2023 118 22 June

ALICE Collaboration††thanks: See Appendix A for the list of collaboration
members ALICE Collaboration

In this Letter, the first measurement of the inelastic cross section for
antitriton–nucleus interactions is reported, covering the momentum range of
$0.8\leq p<2.4$ $\mathrm{GeV}/c$. The measurement is carried out using data
recorded with the ALICE detector in pp and Pb–Pb collisions at a centre-of-
mass energy per nucleon of 13 TeV and 5.02 TeV, respectively. The detector
material serves as an absorber for antitriton nuclei. The raw yield of
(anti)triton nuclei measured with the ALICE apparatus is compared to the
results from detailed ALICE simulations based on the Geant4 toolkit for the
propagation of (anti)particles through matter, allowing one to quantify the
inelastic interaction probability in the detector material. This analysis
complements the measurement of the inelastic cross section of antinuclei up to
$A=3$ carried out by the ALICE Collaboration, and demonstrates the feasibility
of the study of the isospin dependence of inelastic interaction cross section
with the analysis techniques presented in this Letter.

##  1 Introduction

The properties of light antinuclei (such as antideuteron $\overline{\rm d}$,
antihelium ${}^{3}\overline{\rm He}$ and antitriton ${}^{3}\overline{\rm H}$)
have been a subject of various studies at accelerators in the last few
decades. These objects, composed of antiprotons and antineutrons, are stable
in vacuum, but annihilate when coming into contact with normal matter. So far,
light antinuclei have only been observed in high-energy particle collisions at
various fixed-target and collider experiments, from the AGS [1, 2, 3, 4], to
the SPS [5], RHIC [6, 7, 8, 9, 10, 11], and the LHC [12, 13, 14, 15, 16, 17,
18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29]. Their production mechanism
has been actively studied in the context of matter–antimatter asymmetry and of
understanding the formation of composite nuclear objects [30, 31, 32, 33, 34,
24]. However, until very recently, the studies of their inelastic interactions
with matter have been difficult, since obtaining an isolated beam of light
antinuclei with precisely determined momentum comprises formidable challenges.
In fact, only the antideuteron inelastic cross section had been measured at
total momenta of 13.3 GeV/$c$ [35] and 25 GeV/$c$ [36].

Recently, new measurements of the inelastic cross sections of antinuclei with
matter at low momenta ($p\leq 8$ $\mathrm{GeV}/c$) were reported by the ALICE
Collaboration, both for $\overline{\rm d}$ [37] and
${}^{3}\mathrm{\overline{He}}$ [38]. While these measurements were mainly
motivated by their impact on astrophysical dark-matter searches, they also
allow a more detailed look into the physics of low-energy antinucleus–nucleus
interactions, which can be used to improve Monte Carlo (MC) simulations of
particle physics detectors and to better understand the properties of these
composite objects at low kinetic energies. More accurate MC simulations of
inelastic interactions with the detector material also allow one to improve
the measurements of the production yields of antinuclei [39, 24, 26]. However,
one aspect which so far has not been accessible with these measurements is the
isospin dependence of the inelastic cross section of composite antinuclei.
This effect is difficult to evaluate since the lightest isospin-partner
antinuclei are ${}^{3}\mathrm{\overline{He}}$ and ${}^{3}\overline{\rm H}$,
which are only produced in limited quantities in high-energy hadronic
collisions at accelerators [26].

In this Letter the first measurement of the antitriton–nucleus inelastic
interaction cross section $\sigma_{\rm inel}(^{3}\overline{\rm H})$ is
reported, which complements the measurements of the inelastic cross sections
for light antinuclei up to $A=3$ [37, 38]. The results are compared to the
calculations based on the Glauber approach as implemented in the Geant4
toolkit, which is widely used in particle physics for the propagation of
particles through the detector material [40, 41]. The $\sigma_{\rm
inel}(^{3}\overline{\rm H})$ results are also compared with the measurement of
the ${}^{3}\mathrm{\overline{He}}$ inelastic cross section and demonstrate the
feasibility to investigate the isospin dependence of inelastic interactions of
antinuclei.

##  2 Experimental apparatus and data sample

A detailed description of the performance of the ALICE detector and its
subsystems can be found in Refs. [42, 43]. The detectors used in this analysis
for tracking and particle identification are briefly described in the
following paragraph.

Trajectories of charged particles are reconstructed in the ALICE central
barrel with the Inner Tracking System (ITS) [44] and the Time Projection
Chamber (TPC) [45]. Both these detectors cover the full azimuthal angle within
the pseudorapidity interval of $|\eta|<$ 0.9 and reside within a solenoid
which provides a homogeneous magnetic field of $0.5\text{\,}\mathrm{T}$ along
the beam axis. The ITS comprises six cylindrical layers of silicon detectors
which are located at radial distances from the beam axis between
$3.9\text{\,}\mathrm{cm}$ and $43\text{\,}\mathrm{cm}$ and provides important
information to reconstruct the primary collision vertex and to aid in charged
particle tracking. It is surrounded by the TPC – the main tracking device in
the ALICE central barrel which is a 5 m long cylindrical gaseous detector
extending from 85 cm to 247 cm in the radial direction. The TPC provides up to
159 spatial points for the reconstruction of charged-particle tracks and for
particle identification (PID) through the measurement of the specific energy
loss $\mathrm{d}E/\mathrm{d}x$ in the gas volume. The PID is complemented by
the Time-of-Flight (TOF) detector [46] located at the radial distance of 3.7 m
from the beam axis. The TOF measures the arrival time of particles relative to
the event collision time which is provided either by the TOF itself or by the
T0 detectors, two arrays of Cherenkov counters located at forward rapidities
[47]. Together with the momentum of the particle obtained from the track
curvature, the time-of-flight measurement allows one to determine the
particle’s mass. Finally, a stainless steel space-frame supporting structure
and the Transition Radiation Detector (TRD) are located between the TPC and
the TOF; while neither the space-frame nor the TRD is used directly in this
analysis, they significantly contribute to the total material budget in which
antinuclei can interact inelastically [38, 37].

The results presented in this Letter are based on the data collected during
the 2016, 2017, and 2018 LHC operation with proton beams at a centre-of-mass
energy $\sqrt{s}$ = 13 TeV with the high-multiplicity (HM) trigger, and the
2018 Pb–Pb campaign at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV with the minimum
bias (MB), central (0–10%) or semi-central (30–50%) event triggers. The
central event trigger corresponds to the selection of 10% of all inelastic
events with the highest signal amplitude in the V0 detectors (0–10% centrality
[48]), whereas semi-central trigger is tuned to select events within 30–50%
centrality range. Collision events are selected by using the information from
the V0 detectors [49], which consist of two plastic scintillator arrays
located on both sides of the interaction point at forward and backward
pseudorapidities. The V0 detectors are also used to reject other sources of
tracks such as beam–gas interactions and interactions within the beampipe. For
the MB event trigger, coincident signals in both V0 scintillators are required
to be synchronous with the beam crossing time defined by the LHC clock. In
order to trigger on events with high charged-particle multiplicities, the
total signal amplitude measured in the V0 detector is additionally required to
exceed a given threshold for a given event activity. This selects the 0.17% of
events with the highest multiplicity in the V0 detectors in pp collisions. An
additional cut is made on the z position of the primary vertex ($|Vtx_{z}|<10$
cm).

In total, about 109 events from the pp data sample are selected for further
analysis, while for the Pb–Pb dataset about $230\times 10^{6}$ events are
analysed.

##  3 Data analysis

Once produced in the initial collisions between protons or heavy ions,
antitriton nuclei traverse the detector, with some of them interacting
inelastically with the detector material. In a traditional fixed-target
experiment, the measurement of a cross section implies the availability of a
beam of the particle of interest, which traverses the target in order to
determine the loss of particles. Due to the unfeasibility of isolating a beam
of low energy antinuclei, the measurements presented in this work rely on
ratios that are sensitive to this loss without depending on the absolute
number of produced antinuclei. Two methods have been applied to evaluate the
inelastic cross section of antitritons, $\sigma_{\rm inel}(^{3}\overline{\rm
H})$, similarly to what has been done in Refs. [38, 37] for the
${}^{3}\mathrm{\overline{He}}$ and $\overline{\mathrm{d}}$ inelastic cross
section measurements.

The first method, namely the antibaryon-to-baryon method, was used to analyse
the high-multiplicity pp collisions and is based on the comparison of measured
${}^{3}\overline{\rm H}$ and 3H yields. Due to the extra inelastic processes
which occur as particles traverse the detector, less ${}^{3}\overline{\rm H}$
is detected than its matter counterpart. This loss is quantified by comparison
with detailed MC simulations of the ALICE detector. This method makes use of
the fact that the relative amounts of matter and antimatter produced at LHC
energies are almost equal [50, 51], and for ${}^{3}\overline{\mathrm{H}}$ and
${}^{3}\mathrm{H}$ can be calculated from the antiproton-to-proton ratio [51,
52] to be 0.994 ${}_{-0.045}^{+0.006}$ . Thus, the antiparticle-to-particle
ratio is sensitive to the loss of antinuclei. This method allows one to extend
the measurement of ${}^{3}\overline{\rm H}$ up to $p_{\mathrm{primary}}=2.4$
GeV/$c$, but is unfeasible for application in Pb–Pb collisions due to copious
3H background from spallation processes [19].

The second method, applied in the analysis of Pb–Pb data, relies on the
measurement of the amount of raw ${}^{3}\overline{\rm H}$ reconstructed in the
TOF detector and of those reconstructed in the TPC. This is the TOF-to-TPC
method employed in Ref. [38]. In this case, the number of ${}^{3}\overline{\rm
H}$ nuclei tagged in the TPC and measured in the TOF is compared to that of
${}^{3}\overline{\rm H}$ reconstructed in the TPC, which allows one to
quantify the inelastic processes occurring in the material between the TPC and
the TOF detectors. This is an almost direct analogy of a fixed target
experiment, as the particles identified in the TPC act as the beam, while the
ones reaching the TOF represent the particles surviving after the target. In
order to extract the inelastic cross section while avoiding any bias due to
finite detector acceptance and tracking efficiencies, data are compared to MC
simulations that reproduce the conditions of the data taking. This method is
applicable only in the momentum range in which ${}^{3}\overline{\rm H}$ can be
clearly identified in both TPC and TOF detectors
($0.9<p_{\mathrm{primary}}<1.5$ GeV/$c$) and is used in the analysis of Pb–Pb
data due to the larger yield of produced ${}^{3}\overline{\rm H}$ nuclei
compared to pp collisions.
For both methods, the experimental results are compared with the corresponding
ratios evaluated by means of a full-scale MC Geant4 simulation with varied
$\sigma_{\rm inel}(^{3}\overline{\rm H})$ cross sections, as described in
section 3.4. In both cases, using ratios instead of individual particle yields
allows one to extract the antitriton inelastic cross section independently
from its production cross section. Further details on the data analysis are
described in the following sections.

###  3.1 Track selection and particle identification

(Anti)3H candidates are selected from a sample of charged-particle tracks
reconstructed in the ITS and TPC in the pseudorapidity range $|\eta|<0.8\
(0.75)$ for the Pb–Pb (pp) data sample, and at midrapidity with |$y$| < 0.5
for both samples. Several track quality criteria are applied, such as a
minimum number of clusters in the TPC of at least 100 out of a maximum of 159,
and at least 2 in the ITS, with at least one cluster located in any of the two
innermost ITS layers. Furthermore, the number of TPC crossed rows is
constrained to be more than 70. A good quality of the track fit is achieved by
requiring the $\chi^{2}$ per TPC reconstructed point to be less than 2.5 (4)
for the Pb–Pb (pp) data sample. These cuts are stricter in the Pb–Pb data
sample due to the higher track density environment. The number of TPC clusters
used in the calculation of the specific energy loss
($\textrm{d}E/\textrm{d}x$) is required to be larger than 100 (55) to ensure a
good $\textrm{d}E/\textrm{d}x$ resolution in the Pb–Pb (pp) dataset. The
contribution from secondary tracks in the pp data sample is reduced by
selecting a maximum distance of closest approach (DCA) to the primary vertex
in the transverse plane ($\mathrm{DCA}_{xy}$) and in the longitudinal
direction ($\mathrm{DCA}_{z}$) lower than 0.1 cm.

The (anti)triton candidate tracks are identified using the information on the
specific energy loss $\textrm{d}E/\textrm{d}x$ in the TPC gas volume, which is
complemented by the information on the time-of-flight measurement in the TOF
detector. The $n\sigma^{\rm TPC}$ variable represents the PID response in the
TPC expressed in terms of the deviation between the measured and expected
$\textrm{d}E/\textrm{d}x$, normalised by the detector resolution $\sigma$. The
expected $\textrm{d}E/\textrm{d}x$ is computed with a parameterised
Bethe–Bloch formula [43]. For the antibaryon-to-baryon method, (anti)tritons
are selected in the TPC by applying the selection criterion $|n\sigma^{\rm
TPC}|<3.0$, once the requirement on the squared mass hypothesis of the
(anti)tritons
$|\mathrm{m}_{\mathrm{TOF}}^{2}-\mathrm{m}_{{}^{3}\mathrm{\overline{H}}}^{2}|<2$
(GeV/$c^{2}$)2 measured with the TOF detector is fulfilled. Candidate tracks
which do not reach the TOF are not considered in the analysis. This selection
is sufficient to obtain a purity close to 100% for (anti)tritons in the full
momentum range explored in this analysis (1.3 $<p<$ 2.4 $\mathrm{GeV}/c$).

For the TOF-to-TPC method, ${}^{3}\overline{\rm H}$ candidates need to be
reconstructed in both TPC and TOF detectors in the same momentum intervals,
hence the analysis is restricted to the momentum range of 0.9 $<p<$ 1.5
$\mathrm{GeV}/c$. Antitriton candidates are selected in the TPC by applying
the selection of $-2.0<n\sigma^{\rm TPC}<3.5$, and then matched to TOF hits.
The asymmetric selection interval allows one to suppress the contamination due
to other particle species, misidentified as ${}^{3}\overline{\rm H}$ in the
TPC, with lower $\textrm{d}E/\textrm{d}x$ signal. Any residual contamination
in the $n\sigma^{\rm TPC}$ distributions is fitted with an exponential
function and subtracted. Such contribution is negligible at low momentum and
amounts to < 1% in the momentum interval 1.3 $<p<$ 1.5 $\mathrm{GeV}/c$.
Similarly to the $n\sigma^{\rm TPC}$, the $n\sigma^{\rm TOF}$ variable
represents the deviation between the measured and expected time-of-flight of
antitritons, normalised by the resolution of the time-of-flight measurement.
In the TOF, ${}^{3}\overline{\rm H}$ nuclei are selected in the range of
$-3.0<n\sigma^{\rm TOF}<4.0$. The reason for an asymmetric interval is the
presence of an exponential tail towards higher values of $n\sigma^{\rm TOF}$,
that reflects the TOF detector time response [46].

Particularly for this analysis, a special reconstruction of the Pb–Pb
collisions was used, in order to minimise the sensitivity to elastic
scattering in the material. In the TOF, tracks are only associated with a hit
cluster if the cluster is within a certain distance from the extrapolated
position of the track reconstructed in the TPC. This maximum distance was
increased in this reconstruction, from 3 cm to 10 cm, with the latter being
the usual window for pp collisions.

###  3.2 Corrections

The sample of 3H candidates reconstructed as described above includes both the
nuclei produced in the initial collisions and those produced in the spallation
processes occurring when particles traverse the beam pipe and the detector
material. Since this process produces nuclei by spallation from other heavier
nuclei, it can not produce antinuclei, but rather secondary nuclei only. The
antibaryon-to-baryon ratio method employed in pp collisions is sensitive to
these secondary nuclei, since it compares the yields of antitriton to those of
triton in order to measure the inelastic cross section. Therefore, this effect
needs to be corrected for. In order to distinguish between tritons originating
from the initial collision and those originating from spallation processes,
their different DCAs to the primary vertex in the transverse plane are used.
While primary nuclei have DCA distributions peaked around zero, secondary
nuclei show much broader DCA distributions which are flat over most of the
studied DCA range. The different DCA distributions for the two types of nuclei
are studied with templates from detailed MC simulations, and the relative
contributions are therefore obtained, as shown in details in Ref. [19]. The
uncertainty from this correction is estimated to be below 5%.

A second correction is applied to account for any energy loss which occurs
before the inelastic interactions, due to ionisation and rescattering
processes. The energy loss has to be estimated differently between the two
approaches, as what needs to be corrected in the antibaryon-to-baryon method
is the energy loss between the primary vertex and the point where the
${}^{3}\overline{\rm H}$ inelastic interaction occurs, while for the TOF-to-
TPC method it is the energy loss between the TPC and the interaction point.
For the antibaryon-to-baryon method, the momentum of the tracks is estimated
by measuring their curvature, and it is then propagated towards the primary
vertex accounting for the measured energy loss, and thus is the momentum at
the primary vertex $p_{\mathrm{primary}}$.

Due to continuous energy-loss effects in the detector material, the inelastic
interaction of the antinuclei with the detector material happens at a momentum
$p$, which is lower than the momentum $p_{\mathrm{primary}}$ reconstructed at
the primary collision vertex. The corresponding effect is taken into account
utilising MC simulations in which one has precise information about both
momenta for each (anti)particle. In the analysis of pp collisions using the
antibaryon-to-baryon method, the average values of $p/$$p_{\mathrm{primary}}$
distributions in each analysed $p_{\mathrm{primary}}$ interval are used to
consider the energy loss. The root mean square (RMS) of these distributions is
used to determine the uncertainty of the momentum p, which is propagated to
the uncertainty of the measured cross section. For the analysis of the Pb–Pb
data sample using the TOF-to-TPC method, the MC information on the momenta of
daughter tracks originating from the ${}^{3}\overline{\rm H}$ annihilation is
used to estimate the momentum of the particle at annihilation. This is
compared to $p_{\mathrm{primary}}$ to estimate the magnitude of this effect
and the resulting uncertainty. The uncertainty on the inelastic cross section
from the continous energy loss is evaluated to be less than 2% for the
antibaryon-to-baryon method and less than 2.5% for the TOF-to-TPC method.

###  3.3 Systematic uncertainties

Several sources of systematic uncertainties have been considered, depending on
the method used for the inelastic cross section extraction. The total
uncertainty is obtained as the quadratic sum of the individual contributions,
assuming uncorrelated contributions.

The first source of systematic uncertainty, investigated for both methods, is
due to the track selection criteria. The criteria have been varied 100 times,
both in data and MC, using random uniform distributions around the nominal
values. In the case of the antibaryon-to-baryon method, the relative
systematic uncertainty is given by the RMS divided by the mean value of the
distributions of the ${}^{3}\overline{\rm H}$-to-3H ratios in each momentum
interval. For the TOF-to-TPC ratio method, the systematic uncertainty is
evaluated as half the maximum difference between the resulting inelastic cross
sections. Variations consistent with statistical fluctuations are rejected
from the trials used to estimate the systematic uncertainties according to the
Barlow criterion [53]. This contribution is 13$\%$ for the TOF-to-TPC method,
flat in momentum, while it is rejected by the Barlow test in the other method,
using a cutoff value of $2\sigma_{\mathrm{Barlow}}$. This difference in the
systematic uncertainty due to track selection criteria is due to the fact that
in the antibaryon-to-baryon method, the effect of the track selection applies
similarly to both the baryon and antibaryon tracks, and thus cancels out to a
large extent.

For the antibaryon-to-baryon ratio method, the systematic uncertainty due to
the effect of secondary nuclei from spallation on the ratio is considered.
This correction is described in section 3.2. Variations of the binning and of
the fit range (from $\pm 1$ cm to $\pm 2$ cm around the primary vertex) have
been performed to evaluate this uncertainty, which is $\sim$6% in the lowest
momentum bin and $<1$% at higher momenta. For the antibaryon-to-baryon method
[37], three additional uncertainties are included: i) the uncertainty on the
primordial antimatter-to-matter ratio produced in collisions, ii) the
uncertainty due to the elastic cross section of 3H and iii) the one due to the
inelastic cross section of 3H. All three are considered as global
uncertainties for the antibaryon-to-baryon method. These uncertainties are
4.5%, 1%, and 2.3% in the whole momentum interval, respectively.

For the TOF-to-TPC ratio method, additional sources of systematic
uncertainties are related to the description of the material budget in the MC
simulations, the PID, and the momentum correction evaluation. The material
budget of ALICE is varied by $\pm 4.5\%$ in MC simulations, and the deviations
of the final results from the default case are considered as an uncertainty.
The value of 4.5% corresponds to the current uncertainty on the material
obtained by photon conversion measurements [43] and by the studies of the TOF-
to-TPC matching efficiency with pions [54]. The uncertainty related to the PID
has been evaluated as the difference between the raw yields obtained by
subtracting the background contribution from the $n\sigma^{\rm TPC}$
distributions when varying the function used to fit the contamination
(Gaussian, double Gaussian, Gaussian + 2 exponential functions). The
contribution coming from the difference between the bin-counting method and
the integral of the signal function is added in quadrature to the previous
one. The deviation of the final results from the default case divided by
$\sqrt{12}$ is considered as uncertainty.

The systematic uncertainty due to the energy loss correction is evaluated as
described in section 3.2, and amounts to $\sim$2% ($\sim 5$%) in the analysis
of Pb–Pb (pp) collisions.

###  3.4 Monte Carlo simulations

The experimental observables, shown in Fig. 1, are compared with the
corresponding ratios from MC simulations based on Geant4. The parameterisation
of the inelastic cross section in Geant4 is based on Glauber calculations [55,
56], which are based on geometrically scaling the inelastic antiproton–proton
cross sections to heavier systems. This parameterisation neglects the effect
of Coulomb interactions, which are negligible for $p>1$ $\mathrm{GeV}/c$. The
analysis described above is repeated using several MC simulations with varied
values of the antitriton inelastic cross sections. In the case of the
antibaryon-to-baryon method, three MC simulations are used, with $\sigma_{\rm
inel}(^{3}\overline{\rm H})$ multiplied by a factor of 0.75, 1, and 4. The
simulations with these factors were already available and were thus used. In
the case of the TOF-to-TPC method, three MC simulations are used, with
$\sigma_{\rm inel}(^{3}\overline{\rm H})$ multiplied by a factor of 0.5 and
1.5, in addition to the default one. The corresponding MC ratios for the two
cases are shown as coloured bands in Fig. 1 and are used as references for the
experimental ratios to obtain the ${}^{3}\overline{\rm H}$ inelastic cross
section as described in the following section.

Figure 1: Left: raw primary $\overline{{{}^{3}\rm H}}/{\rm{{}^{3}H}}$ ratio as
a function of the momentum $p_{\mathrm{primary}}$ in pp collisions at
$\sqrt{s}=13$ TeV. Right: ratio between the raw number of ${}^{3}\overline{\rm
H}$ candidates reconstructed in the TOF and the raw number of
${}^{3}\overline{\rm H}$ reconstructed in the TPC in Pb–Pb collisions at
$\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV as a function of the momentum
$p_{\mathrm{primary}}$. In both panels, data are shown in black, the
statistical and systematic uncertainties are shown as vertical bars and boxes,
respectively. The results from ALICE MC simulations based on Geant4 are shown
as coloured bands, the different colours referring to the different inelastic
cross sections implemented in the simulations, with default $\sigma_{\rm
inel}$ described in Ref. [56]. The width of the MC band represents the
statistical uncertainty of the simulation.

###  3.5 Inelastic cross section determination

The determination of the inelastic cross section requires precise knowledge of
the ALICE detector material budget. Detailed studies of the detector material
have been carried out in previous works by the ALICE Collaboration [37, 38].
These studies allow the determination of the effective target material. For
the analysis based on the antibaryon-to-baryon method, the inelastic
interactions can occur in the ITS, TPC, TRD, and TOF detectors, hence the
average material corresponds to $\langle Z\rangle=14.8$ and $\langle
A\rangle=31.8$. For the TOF-to-TPC method, instead, the average material is
the TRD and space frame system, corresponding to $\langle Z\rangle=16.1$ and
$\langle A\rangle=34.7$. Using the same procedure described in Refs. [37, 38],
the MC ratios obtained with the different multiplicative factors applied to
$\sigma_{\mathrm{inel}}($${}^{3}\overline{\rm H}$) are fitted in each momentum
interval using a Lambert–Beer function:

$R=\exp(-\rm a\sigma)\times b,$ (1)

where $R$ refers to the MC ratios obtained with either of the two methods, a
and b are the fit parameters, and $\sigma$ refers to the scaling factor of the
$\sigma_{\rm inel}(^{3}\overline{\rm H})$. The experimental ratios are
therefore projected on the fit function and a scaling factor for the Geant4
parameterisation is obtained for each momentum interval. This scaling factor
shows by how much the inelastic cross section needs to be changed in the
Geant4 MC implementation with respect to default to reach the same value for
the observable (antitriton-to-triton ratio for pp, TPC-to-TOF ratio for Pb–Pb)
as in the data. Finally, by multiplying the scaling factor in each interval by
the default inelastic cross section implemented in Geant4, the inelastic cross
section is obtained. Since only cross sections on integer atomic numbers can
be obtained in Geant4, the inelastic cross section on the nearest available
element was scaled according to the Glauber model [55] as described in
equation 2

$\sigma(\rm{A_{ALICE}})=\sigma(\rm{A_{\textsc{Geant4}}})\times\frac{1.34\times\rm{A_{\textsc{Geant4}}^{0.21}}+1.51\times\rm{A_{\textsc{Geant4}}^{-1/3}}}{1.34\times\rm{A_{ALICE}^{0.21}}+1.51\times\rm{A_{ALICE}^{-1/3}}}$
(2)

where $\rm{A_{ALICE}}$ is the average atomic number seen by antinuclei as they
travel through the ALICE detector and $\rm{A_{\textsc{Geant4}}}$ is the atomic
number of the closest available element in Geant4. The resulting $\sigma_{\rm
inel}(^{3}\overline{\rm H})$ is shown in the left panel of Fig. 2, for the two
analysed data samples. For the ease of comparison, the results from the
antibaryon-to-baryon analysis have been scaled to the same average material as
the results from the TOF-to-TPC analysis, also according to equation 2, and
$\sigma($Geant4) is shown as well. Since $\sigma($Geant4) does not depend on
the collision system, this allows for a fair comparison of the shown
measurements. It can be seen that the measurements using the antibaryon-to-
baryon method agree with $\sigma($Geant4) at a 1 $\sigma$ level, and the TOF-
to-TPC ratio method at a 2 $\sigma$ level. The inelastic cross sections are
shown as a function of the momentum $p$ at which the inelastic interaction
occurs.
Comparing the inelastic cross sections for ${}^{3}\overline{\rm H}$ and
${}^{3}\overline{\rm{He}}$ shows that the two measurements are consistent
within uncertainties (see right panel of Fig. 2). The uncertainties are
dominated by statistical uncertainties, and thus do not cancel when taking the
ratio of $\sigma_{\rm inel}(^{3}\overline{\rm H})$ and
$\sigma_{\mathrm{inel}}(^{3}\overline{\mathrm{He}})$. There are no
quantitative predictions for the expected difference between the two isospin
partners, however, a naive approach would be to consider their size as the
dominant factor. No measurements of the nuclear mass radii of these antinuclei
exist, and thus the matter radii are taken as a proxy. However, since the
difference in mass radii is expected to be smaller than the difference in
matter radii, this is a conservative estimate. The measured matter radii of
the two nuclei are 1.76 fm for 3He [57] and 1.59 fm for 3H [57]. While no
independent measurement exists for the antinuclei counterparts, the antinuclei
are assumed to have the same size as their matter counterparts by CPT
symmetry. This would suggest that the inelastic cross section of
${}^{3}\mathrm{\overline{He}}$ should be a factor 0 – 20% larger than the one
of ${}^{3}\overline{\rm H}$. The current measurement is not sensitive enough
to distinguish differences of that order and the cross sections of
${}^{3}\overline{\rm H}$ and ${}^{3}\overline{\rm He}$ are compatible within
errors. The larger size of the data samples expected in the upcoming Run 3 and
Run 4 campaigns of the LHC will allow a significant improvement over the
current measurement.

Figure 2: Left: inelastic interaction cross section for antitritons with the
two analysis methods on an average material element of the ALICE detector as a
function of the momentum $p$ at which the interaction occurs. Dashed black
lines represent the default Geant4 parameterisations for antitritons. Right:
comparison between the results reported in the left panel and the results for
${}^{3}\overline{\rm He}$ inelastic cross section measured in Pb–Pb collisions
at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV from Ref. [38]. Note that
${}^{3}\overline{\rm He}$ nuclei can be clearly identified in both TPC and TOF
detectors over a much wider momentum range than ${}^{3}\overline{\rm H}$. In
both panels, boxes show the statistical and systematic uncertainties summed in
quadrature.

##  4 Summary

The results presented in this Letter represent the first measurement of the
antitriton inelastic cross section, and complete the set of measurements of
antinuclei–matter inelastic cross section up to $A=3$ of the projectile
antinucleus by ALICE. The results have been found, within sizeable
uncertainties, to be consistent with the parameterisation used in Geant4
toolkit and with existing ${}^{3}\mathrm{\overline{He}}$ measurements from
Ref. [38]. They demonstrate the feasibility of studying the isospin dependence
of inelastic interactions of composite antinuclei such as ${}^{3}\overline{\rm
H}$ and ${}^{3}\mathrm{\overline{He}}$. Future studies of larger data samples
collected during the LHC Run 3 and Run 4 campaigns (starting from 2022) with
the upgraded ALICE apparatus will substantially improve on the measurements
presented in this Letter. They will allow for more precise comparison between
${}^{3}\overline{\rm H}$ and ${}^{3}\mathrm{\overline{He}}$ results and for
better calculations of the inelastic cross sections of antinuclei in the
currently used models, improving also our understanding of antinucleus–matter
inelastic interactions at momenta around 1 GeV/$c$.

## Acknowledgements

The ALICE Collaboration would like to thank all its engineers and technicians for their invaluable contributions to the construction of the experiment and the CERN accelerator teams for the outstanding performance of the LHC complex. The ALICE Collaboration gratefully acknowledges the resources and support provided by all Grid centres and the Worldwide LHC Computing Grid (WLCG) collaboration. The ALICE Collaboration acknowledges the following funding agencies for their support in building and running the ALICE detector: A. I. Alikhanyan National Science Laboratory (Yerevan Physics Institute) Foundation (ANSL), State Committee of Science and World Federation of Scientists (WFS), Armenia; Austrian Academy of Sciences, Austrian Science Fund (FWF): [M 2467-N36] and Nationalstiftung für Forschung, Technologie und Entwicklung, Austria; Ministry of Communications and High Technologies, National Nuclear Research Center, Azerbaijan; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Financiadora de Estudos e Projetos (Finep), Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) and Universidade Federal do Rio Grande do Sul (UFRGS), Brazil; Bulgarian Ministry of Education and Science, within the National Roadmap for Research Infrastructures 2020-2027 (object CERN), Bulgaria; Ministry of Education of China (MOEC) , Ministry of Science & Technology of China (MSTC) and National Natural Science Foundation of China (NSFC), China; Ministry of Science and Education and Croatian Science Foundation, Croatia; Centro de Aplicaciones Tecnológicas y Desarrollo Nuclear (CEADEN), Cubaenergía, Cuba; Ministry of Education, Youth and Sports of the Czech Republic, Czech Republic; The Danish Council for Independent Research | Natural Sciences, the VILLUM FONDEN and Danish National Research Foundation (DNRF), Denmark; Helsinki Institute of Physics (HIP), Finland; Commissariat à l’Energie Atomique (CEA) and Institut National de Physique Nucléaire et de Physique des Particules (IN2P3) and Centre National de la Recherche Scientifique (CNRS), France; Bundesministerium für Bildung und Forschung (BMBF) and GSI Helmholtzzentrum für Schwerionenforschung GmbH, Germany; General Secretariat for Research and Technology, Ministry of Education, Research and Religions, Greece; National Research, Development and Innovation Office, Hungary; Department of Atomic Energy Government of India (DAE), Department of Science and Technology, Government of India (DST), University Grants Commission, Government of India (UGC) and Council of Scientific and Industrial Research (CSIR), India; National Research and Innovation Agency - BRIN, Indonesia; Istituto Nazionale di Fisica Nucleare (INFN), Italy; Japanese Ministry of Education, Culture, Sports, Science and Technology (MEXT) and Japan Society for the Promotion of Science (JSPS) KAKENHI, Japan; Consejo Nacional de Ciencia (CONACYT) y Tecnología, through Fondo de Cooperación Internacional en Ciencia y Tecnología (FONCICYT) and Dirección General de Asuntos del Personal Academico (DGAPA), Mexico; Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO), Netherlands; The Research Council of Norway, Norway; Commission on Science and Technology for Sustainable Development in the South (COMSATS), Pakistan; Pontificia Universidad Católica del Perú, Peru; Ministry of Education and Science, National Science Centre and WUT ID-UB, Poland; Korea Institute of Science and Technology Information and National Research Foundation of Korea (NRF), Republic of Korea; Ministry of Education and Scientific Research, Institute of Atomic Physics, Ministry of Research and Innovation and Institute of Atomic Physics and University Politehnica of Bucharest, Romania; Ministry of Education, Science, Research and Sport of the Slovak Republic, Slovakia; National Research Foundation of South Africa, South Africa; Swedish Research Council (VR) and Knut & Alice Wallenberg Foundation (KAW), Sweden; European Organization for Nuclear Research, Switzerland; Suranaree University of Technology (SUT), National Science and Technology Development Agency (NSTDA), Thailand Science Research and Innovation (TSRI) and National Science, Research and Innovation Fund (NSRF), Thailand; Turkish Energy, Nuclear and Mineral Research Agency (TENMAK), Turkey; National Academy of Sciences of Ukraine, Ukraine; Science and Technology Facilities Council (STFC), United Kingdom; National Science Foundation of the United States of America (NSF) and United States Department of Energy, Office of Nuclear Physics (DOE NP), United States of America. In addition, individual groups or members have received support from: European Research Council, Strong 2020 - Horizon 2020 (grant nos. 950692, 824093), European Union; Academy of Finland (Center of Excellence in Quark Matter) (grant nos. 346327, 346328), Finland.

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##  Appendix A The ALICE Collaboration

S. Acharya 127, D. Adamová 87, A. Adler71, G. Aglieri Rinella 33, M. Agnello
30, N. Agrawal 52, Z. Ahammed 135, S. Ahmad 16, S.U. Ahn 72, I. Ahuja 38, A.
Akindinov 141, M. Al-Turany 98, D. Aleksandrov 141, B. Alessandro 57, H.M.
Alfanda 6, R. Alfaro Molina 68, B. Ali 16, A. Alici 26, N. Alizadehvandchali
116, A. Alkin 33, J. Alme 21, G. Alocco 53, T. Alt 65, A.R. Altamura 51, I.
Altsybeev 141, M.N. Anaam 6, C. Andrei 46, A. Andronic 126, V. Anguelov 95, F.
Antinori 55, P. Antonioli 52, N. Apadula 75, L. Aphecetche 104, H.
Appelshäuser 65, C. Arata 74, S. Arcelli 26, M. Aresti 53, R. Arnaldi 57,
J.G.M.C.A. Arneiro 111, I.C. Arsene 20, M. Arslandok 138, A. Augustinus 33, R.
Averbeck 98, M.D. Azmi 16, H. Baba124, A. Badalà 54, J. Bae 105, Y.W. Baek 41,
X. Bai 120, R. Bailhache 65, Y. Bailung 49, A. Balbino 30, A. Baldisseri 130,
B. Balis 2, D. Banerjee 4, Z. Banoo 92, R. Barbera 27, F. Barile 32, L.
Barioglio 96, M. Barlou79, G.G. Barnaföldi 47, L.S. Barnby 86, V. Barret 127,
L. Barreto 111, C. Bartels 119, K. Barth 33, E. Bartsch 65, N. Bastid 127, S.
Basu 76, G. Batigne 104, D. Battistini 96, B. Batyunya 142, D. Bauri48, J.L.
Bazo Alba 102, I.G. Bearden 84, C. Beattie 138, P. Becht 98, D. Behera 49, I.
Belikov 129, A.D.C. Bell Hechavarria 126, F. Bellini 26, R. Bellwied 116, S.
Belokurova 141, G. Bencedi 47, S. Beole 25, A. Bercuci 46, Y. Berdnikov 141,
A. Berdnikova 95, L. Bergmann 95, M.G. Besoiu 64, L. Betev 33, P.P. Bhaduri
135, A. Bhasin 92, M.A. Bhat 4, B. Bhattacharjee 42, L. Bianchi 25, N. Bianchi
50, J. Bielčík 36, J. Bielčíková 87, J. Biernat 108, A.P. Bigot 129, A.
Bilandzic 96, G. Biro 47, S. Biswas 4, N. Bize 104, J.T. Blair 109, D. Blau
141, M.B. Blidaru 98, N. Bluhme39, C. Blume 65, G. Boca 22,56, F. Bock 88, T.
Bodova 21, A. Bogdanov141, S. Boi 23, J. Bok 59, L. Boldizsár 47, M. Bombara
38, P.M. Bond 33, G. Bonomi 134,56, H. Borel 130, A. Borissov 141, A.G.
Borquez Carcamo 95, H. Bossi 138, E. Botta 25, Y.E.M. Bouziani 65, L. Bratrud
65, P. Braun-Munzinger 98, M. Bregant 111, M. Broz 36, G.E. Bruno 97,32, M.D.
Buckland 24, D. Budnikov 141, H. Buesching 65, S. Bufalino 30, P. Buhler 103,
N. Burmasov 141, Z. Buthelezi 69,123, A. Bylinkin 21, S.A. Bysiak108, M. Cai
6, H. Caines 138, A. Caliva 29, E. Calvo Villar 102, J.M.M. Camacho 110, P.
Camerini 24, F.D.M. Canedo 111, S.L. Cantway 138, M. Carabas 114, A.A.
Carballo 33, F. Carnesecchi 33, R. Caron 128, L.A.D. Carvalho 111, J. Castillo
Castellanos 130, F. Catalano 33,25, C. Ceballos Sanchez 142, I. Chakaberia 75,
P. Chakraborty 48, S. Chandra 135, S. Chapeland 33, M. Chartier 119, S.
Chattopadhyay 135, S. Chattopadhyay 100, T.G. Chavez 45, T. Cheng 98,6, C.
Cheshkov 128, B. Cheynis 128, V. Chibante Barroso 33, D.D. Chinellato 112,
E.S. Chizzali II,96, J. Cho 59, S. Cho 59, P. Chochula 33, P. Christakoglou
85, C.H. Christensen 84, P. Christiansen 76, T. Chujo 125, M. Ciacco 30, C.
Cicalo 53, F. Cindolo 52, M.R. Ciupek98, G. ClaiIII,52, F. Colamaria 51, J.S.
Colburn101, D. Colella 97,32, M. Colocci 26, M. Concas IV,57, G. Conesa
Balbastre 74, Z. Conesa del Valle 131, G. Contin 24, J.G. Contreras 36, M.L.
Coquet 130, P. Cortese 133,57, M.R. Cosentino 113, F. Costa 33, S. Costanza
22,56, C. Cot 131, J. Crkovská 95, P. Crochet 127, R. Cruz-Torres 75, P. Cui
6, A. Dainese 55, M.C. Danisch 95, A. Danu 64, P. Das 81, P. Das 4, S. Das 4,
A.R. Dash 126, S. Dash 48, R.M.H. David45, A. De Caro 29, G. de Cataldo 51, J.
de Cuveland39, A. De Falco 23, D. De Gruttola 29, N. De Marco 57, C. De Martin
24, S. De Pasquale 29, R. Deb 134, S. Deb 49, R. Del Grande 96, L. Dello
Stritto 29, W. Deng 6, P. Dhankher 19, D. Di Bari 32, A. Di Mauro 33, B. Diab
130, R.A. Diaz 142,7, T. Dietel 115, Y. Ding 6, R. Divià 33, D.U. Dixit 19, Ø.
Djuvsland21, U. Dmitrieva 141, A. Dobrin 64, B. Dönigus 65, J.M. Dubinski 136,
A. Dubla 98, S. Dudi 91, P. Dupieux 127, M. Durkac107, N. Dzalaiova13, T.M.
Eder 126, R.J. Ehlers 75, F. Eisenhut 65, R. Ejima93, D. Elia 51, B. Erazmus
104, F. Ercolessi 26, F. Erhardt 90, M.R. Ersdal21, B. Espagnon 131, G.
Eulisse 33, D. Evans 101, S. Evdokimov 141, L. Fabbietti 96, M. Faggin 28, J.
Faivre 74, F. Fan 6, W. Fan 75, A. Fantoni 50, M. Fasel 88, P. Fecchio30, A.
Feliciello 57, G. Feofilov 141, A. Fernández Téllez 45, L. Ferrandi 111, M.B.
Ferrer 33, A. Ferrero 130, C. Ferrero 57, A. Ferretti 25, V.J.G. Feuillard 95,
V. Filova 36, D. Finogeev 141, F.M. Fionda 53, F. Flor 116, A.N. Flores 109,
S. Foertsch 69, I. Fokin 95, S. Fokin 141, E. Fragiacomo 58, E. Frajna 47, U.
Fuchs 33, N. Funicello 29, C. Furget 74, A. Furs 141, T. Fusayasu 99, J.J.
Gaardhøje 84, M. Gagliardi 25, A.M. Gago 102, T. Gahlaut48, C.D. Galvan 110,
D.R. Gangadharan 116, P. Ganoti 79, C. Garabatos 98, A.T. Garcia 131, J.R.A.
Garcia 45, E. Garcia-Solis 9, C. Gargiulo 33, K. Garner126, P. Gasik 98, A.
Gautam 118, M.B. Gay Ducati 67, M. Germain 104, A. Ghimouz125, C. Ghosh135, M.
Giacalone 52,26, P. Giubellino 98,57, P. Giubilato 28, A.M.C. Glaenzer 130, P.
Glässel 95, E. Glimos 122, D.J.Q. Goh77, V. Gonzalez 137, M. Gorgon 2, K.
Goswami 49, S. Gotovac34, V. Grabski 68, L.K. Graczykowski 136, E. Grecka 87,
A. Grelli 60, C. Grigoras 33, V. Grigoriev 141, S. Grigoryan 142,1, F. Grosa
33, J.F. Grosse-Oetringhaus 33, R. Grosso 98, D. Grund 36, G.G. Guardiano 112,
R. Guernane 74, M. Guilbaud 104, K. Gulbrandsen 84, T. Gündem 65, T. Gunji
124, W. Guo 6, A. Gupta 92, R. Gupta 92, R. Gupta 49, S.P. Guzman 45, K.
Gwizdziel 136, L. Gyulai 47, M.K. Habib98, C. Hadjidakis 131, F.U. Haider 92,
H. Hamagaki 77, A. Hamdi 75, Y. Han 139, B.G. Hanley 137, R. Hannigan 109, J.
Hansen 76, M.R. Haque 136, J.W. Harris 138, A. Harton 9, H. Hassan 88, D.
Hatzifotiadou 52, P. Hauer 43, L.B. Havener 138, S.T. Heckel 96, E. Hellbär
98, H. Helstrup 35, M. Hemmer 65, T. Herman 36, G. Herrera Corral 8, F.
Herrmann126, S. Herrmann 128, K.F. Hetland 35, B. Heybeck 65, H. Hillemanns
33, B. Hippolyte 129, F.W. Hoffmann 71, B. Hofman 60, G.H. Hong 139, M. Horst
96, A. Horzyk 2, Y. Hou 6, P. Hristov 33, C. Hughes 122, P. Huhn65, L.M. Huhta
117, T.J. Humanic 89, A. Hutson 116, D. Hutter 39, R. Ilkaev141, H. Ilyas 14,
M. Inaba 125, G.M. Innocenti 33, M. Ippolitov 141, A. Isakov 87, T. Isidori
118, M.S. Islam 100, M. Ivanov 98, M. Ivanov13, V. Ivanov 141, K.E. Iversen
76, M. Jablonski 2, B. Jacak 75, N. Jacazio 26, P.M. Jacobs 75, S.
Jadlovska107, J. Jadlovsky107, S. Jaelani 83, C. Jahnke 112, M.J. Jakubowska
136, M.A. Janik 136, T. Janson71, M. Jercic90, S. Ji 17, S. Jia 10, A.A.P.
Jimenez 66, F. Jonas 88,126, D.M. Jones 119, J.M. Jowett 33,98, J. Jung 65, M.
Jung 65, A. Junique 33, A. Jusko 101, M.J. Kabus 33,136, J. Kaewjai106, P.
Kalinak 61, A.S. Kalteyer 98, A. Kalweit 33, V. Kaplin 141, A. Karasu Uysal
73, D. Karatovic 90, O. Karavichev 141, T. Karavicheva 141, P. Karczmarczyk
136, E. Karpechev 141, U. Kebschull 71, R. Keidel 140, D.L.D. Keijdener60, M.
Keil 33, B. Ketzer 43, S.S. Khade 49, A.M. Khan 120,6, S. Khan 16, A.
Khanzadeev 141, Y. Kharlov 141, A. Khatun 118, A. Khuntia 36, M.B. Kidson115,
B. Kileng 35, B. Kim 105, C. Kim 17, D.J. Kim 117, E.J. Kim 70, J. Kim 139,
J.S. Kim 41, J. Kim 59, J. Kim 70, M. Kim 19, S. Kim 18, T. Kim 139, K. Kimura
93, S. Kirsch 65, I. Kisel 39, S. Kiselev 141, A. Kisiel 136, J.P. Kitowski 2,
J.L. Klay 5, J. Klein 33, S. Klein 75, C. Klein-Bösing 126, M. Kleiner 65, T.
Klemenz 96, A. Kluge 33, A.G. Knospe 116, C. Kobdaj 106, T. Kollegger98, A.
Kondratyev 142, N. Kondratyeva 141, E. Kondratyuk 141, J. Konig 65, S.A.
Konigstorfer 96, P.J. Konopka 33, G. Kornakov 136, M. Korwieser 96, S.D.
Koryciak 2, A. Kotliarov 87, V. Kovalenko 141, M. Kowalski 108, V. Kozhuharov
37, I. Králik 61, A. Kravčáková 38, L. Krcal 33,39, M. Krivda 101,61, F.
Krizek 87, K. Krizkova Gajdosova 33, M. Kroesen 95, M. Krüger 65, D.M. Krupova
36, E. Kryshen 141, V. Kučera 59, C. Kuhn 129, P.G. Kuijer 85, T. Kumaoka125,
D. Kumar135, L. Kumar 91, N. Kumar91, S. Kumar 32, S. Kundu 33, P. Kurashvili
80, A. Kurepin 141, A.B. Kurepin 141, A. Kuryakin 141, S. Kushpil 87, M.J.
Kweon 59, Y. Kwon 139, S.L. La Pointe 39, P. La Rocca 27, A. Lakrathok106, M.
Lamanna 33, A.R. Landou 74, R. Langoy 121, P. Larionov 33, E. Laudi 33, L.
Lautner 33,96, R. Lavicka 103, R. Lea 134,56, H. Lee 105, I. Legrand 46, G.
Legras 126, J. Lehrbach 39, T.M. Lelek2, R.C. Lemmon 86, I. León Monzón 110,
M.M. Lesch 96, E.D. Lesser 19, P. Lévai 47, X. Li10, X.L. Li6, J. Lien 121, R.
Lietava 101, I. Likmeta 116, B. Lim 25, S.H. Lim 17, V. Lindenstruth 39, A.
Lindner46, C. Lippmann 98, A. Liu 19, D.H. Liu 6, J. Liu 119, G.S.S. Liveraro
112, I.M. Lofnes 21, C. Loizides 88, S. Lokos 108, J. Lomker 60, P. Loncar 34,
J.A. Lopez 95, X. Lopez 127, E. López Torres 7, P. Lu 98,120, J.R. Luhder 126,
M. Lunardon 28, G. Luparello 58, Y.G. Ma 40, M. Mager 33, A. Maire 129, M.V.
Makariev 37, M. Malaev 141, G. Malfattore 26, N.M. Malik 92, Q.W. Malik20,
S.K. Malik 92, L. Malinina I,VII,142, D. Mallick 81, N. Mallick 49, G.
Mandaglio 31,54, S.K. Mandal 80, V. Manko 141, F. Manso 127, V. Manzari 51, Y.
Mao 6, R.W. Marcjan 2, G.V. Margagliotti 24, A. Margotti 52, A. Marín 98, C.
Markert 109, P. Martinengo 33, M.I. Martínez 45, G. Martínez García 104,
M.P.P. Martins 111, S. Masciocchi 98, M. Masera 25, A. Masoni 53, L.
Massacrier 131, A. Mastroserio 132,51, O. Matonoha 76, S. Mattiazzo 28, P.F.T.
Matuoka111, A. Matyja 108, C. Mayer 108, A.L. Mazuecos 33, F. Mazzaschi 25, M.
Mazzilli 33, J.E. Mdhluli 123, A.F. Mechler65, Y. Melikyan 44, A. Menchaca-
Rocha 68, E. Meninno 103, A.S. Menon 116, M. Meres 13, S. Mhlanga115,69, Y.
Miake125, L. Micheletti 33, L.C. Migliorin128, D.L. Mihaylov 96, K. Mikhaylov
142,141, A.N. Mishra 47, D. Miśkowiec 98, A. Modak 4, A.P. Mohanty 60, B.
Mohanty81, M. Mohisin Khan V,16, M.A. Molander 44, S. Monira 136, Z. Moravcova
84, C. Mordasini 117, D.A. Moreira De Godoy 126, I. Morozov 141, A. Morsch 33,
T. Mrnjavac 33, V. Muccifora 50, S. Muhuri 135, J.D. Mulligan 75, A.
Mulliri23, M.G. Munhoz 111, R.H. Munzer 65, H. Murakami 124, S. Murray 115, L.
Musa 33, J. Musinsky 61, J.W. Myrcha 136, B. Naik 123, A.I. Nambrath 19, B.K.
Nandi 48, R. Nania 52, E. Nappi 51, A.F. Nassirpour 18,76, A. Nath 95, C.
Nattrass 122, M.N. Naydenov 37, A. Neagu20, A. Negru114, L. Nellen 66, R.
Nepeivoda 76, S. Nese 20, G. Neskovic 39, B.S. Nielsen 84, E.G. Nielsen 84, S.
Nikolaev 141, S. Nikulin 141, V. Nikulin 141, F. Noferini 52, S. Noh 12, P.
Nomokonov 142, J. Norman 119, N. Novitzky 125, P. Nowakowski 136, A. Nyanin
141, J. Nystrand 21, M. Ogino 77, S. Oh 18, A. Ohlson 76, V.A. Okorokov 141,
J. Oleniacz 136, A.C. Oliveira Da Silva 122, M.H. Oliver 138, A. Onnerstad
117, C. Oppedisano 57, A. Ortiz Velasquez 66, J. Otwinowski 108, M. Oya93, K.
Oyama 77, Y. Pachmayer 95, S. Padhan 48, D. Pagano 134,56, G. Paić 66, A.
Palasciano 51, S. Panebianco 130, H. Park 125, H. Park 105, J. Park 59, J.E.
Parkkila 33, Y. Patley 48, R.N. Patra92, B. Paul 23, H. Pei 6, T. Peitzmann
60, X. Peng 11, M. Pennisi 25, D. Peresunko 141, G.M. Perez 7, Y. Pestov141,
V. Petrov 141, M. Petrovici 46, R.P. Pezzi 104,67, S. Piano 58, M. Pikna 13,
P. Pillot 104, O. Pinazza 52,33, L. Pinsky116, C. Pinto 96, S. Pisano 50, M.
Płoskoń 75, M. Planinic90, F. Pliquett65, M.G. Poghosyan 88, B. Polichtchouk
141, S. Politano 30, N. Poljak 90, A. Pop 46, S. Porteboeuf-Houssais 127, V.
Pozdniakov 142, I.Y. Pozos 45, K.K. Pradhan 49, S.K. Prasad 4, S. Prasad 49,
R. Preghenella 52, F. Prino 57, C.A. Pruneau 137, I. Pshenichnov 141, M.
Puccio 33, S. Pucillo 25, Z. Pugelova107, S. Qiu 85, L. Quaglia 25, R.E.
Quishpe116, S. Ragoni 15, A. Rakotozafindrabe 130, L. Ramello 133,57, F. Rami
129, S.A.R. Ramirez 45, T.A. Rancien74, M. Rasa 27, S.S. Räsänen 44, R. Rath
52, M.P. Rauch 21, I. Ravasenga 85, K.F. Read 88,122, C. Reckziegel 113, A.R.
Redelbach 39, K. Redlich VI,80, C.A. Reetz 98, A. Rehman21, F. Reidt 33, H.A.
Reme-Ness 35, Z. Rescakova38, K. Reygers 95, A. Riabov 141, V. Riabov 141, R.
Ricci 29, M. Richter 20, A.A. Riedel 96, W. Riegler 33, C. Ristea 64, M.V.
Rodriguez 33, M. Rodríguez Cahuantzi 45, K. Røed 20, R. Rogalev 141, E.
Rogochaya 142, T.S. Rogoschinski 65, D. Rohr 33, D. Röhrich 21, P.F. Rojas45,
S. Rojas Torres 36, P.S. Rokita 136, G. Romanenko 142, F. Ronchetti 50, A.
Rosano 31,54, E.D. Rosas66, K. Roslon 136, A. Rossi 55, A. Roy 49, S. Roy 48,
N. Rubini 26, D. Ruggiano 136, R. Rui 24, P.G. Russek 2, R. Russo 85, A.
Rustamov 82, E. Ryabinkin 141, Y. Ryabov 141, A. Rybicki 108, H. Rytkonen 117,
J. Ryu 17, W. Rzesa 136, O.A.M. Saarimaki 44, R. Sadek 104, S. Sadhu 32, S.
Sadovsky 141, J. Saetre 21, K. Šafařík 36, P. Saha42, S.K. Saha 4, S. Saha 81,
B. Sahoo 48, B. Sahoo 49, R. Sahoo 49, S. Sahoo62, D. Sahu 49, P.K. Sahu 62,
J. Saini 135, K. Sajdakova38, S. Sakai 125, M.P. Salvan 98, S. Sambyal 92, D.
Samitz 103, I. Sanna 33,96, T.B. Saramela111, D. Sarkar 137, N. Sarkar135, P.
Sarma 42, V. Sarritzu 23, V.M. Sarti 96, M.H.P. Sas 138, J. Schambach 88, H.S.
Scheid 65, C. Schiaua 46, R. Schicker 95, A. Schmah95, C. Schmidt 98, H.R.
Schmidt94, M.O. Schmidt 33, M. Schmidt94, N.V. Schmidt 88, A.R. Schmier 122,
R. Schotter 129, A. Schröter 39, J. Schukraft 33, K. Schweda 98, G. Scioli 26,
E. Scomparin 57, J.E. Seger 15, Y. Sekiguchi124, D. Sekihata 124, M. Selina
85, I. Selyuzhenkov 98, S. Senyukov 129, J.J. Seo 95,59, D. Serebryakov 141,
L. Šerkšnytė 96, A. Sevcenco 64, T.J. Shaba 69, A. Shabetai 104, R.
Shahoyan33, A. Shangaraev 141, A. Sharma91, B. Sharma 92, D. Sharma 48, H.
Sharma 55,108, M. Sharma 92, S. Sharma 77, S. Sharma 92, U. Sharma 92, A.
Shatat 131, O. Sheibani116, K. Shigaki 93, M. Shimomura78, J. Shin12, S.
Shirinkin 141, Q. Shou 40, Y. Sibiriak 141, S. Siddhanta 53, T. Siemiarczuk
80, T.F. Silva 111, D. Silvermyr 76, T. Simantathammakul106, R. Simeonov 37,
B. Singh92, B. Singh 96, K. Singh 49, R. Singh 81, R. Singh 92, R. Singh 49,
S. Singh 16, V.K. Singh 135, V. Singhal 135, T. Sinha 100, B. Sitar 13, M.
Sitta 133,57, T.B. Skaali20, G. Skorodumovs 95, M. Slupecki 44, N. Smirnov
138, R.J.M. Snellings 60, E.H. Solheim 20, J. Song 116, A. Songmoolnak106, C.
Sonnabend 33,98, F. Soramel 28, A.B. Soto-hernandez 89, R. Spijkers 85, I.
Sputowska 108, J. Staa 76, J. Stachel 95, I. Stan 64, P.J. Steffanic 122, S.F.
Stiefelmaier 95, D. Stocco 104, I. Storehaug 20, P. Stratmann 126, S. Strazzi
26, C.P. Stylianidis85, A.A.P. Suaide 111, C. Suire 131, M. Sukhanov 141, M.
Suljic 33, R. Sultanov 141, V. Sumberia 92, S. Sumowidagdo 83, S. Swain62, I.
Szarka 13, M. Szymkowski 136, S.F. Taghavi 96, G. Taillepied 98, J. Takahashi
112, G.J. Tambave 81, S. Tang 6, Z. Tang 120, J.D. Tapia Takaki 118, N.
Tapus114, L.A. Tarasovicova 126, M.G. Tarzila 46, G.F. Tassielli 32, A. Tauro
33, G. Tejeda Muñoz 45, A. Telesca 33, L. Terlizzi 25, C. Terrevoli 116, S.
Thakur 4, D. Thomas 109, A. Tikhonov 141, A.R. Timmins 116, M. Tkacik107, T.
Tkacik 107, A. Toia 65, R. Tokumoto93, K. Tomohiro93, N. Topilskaya 141, M.
Toppi 50, T. Tork 131, V.V. Torres 104, A.G. Torres Ramos 32, A. Trifiró
31,54, A.S. Triolo 33,31,54, S. Tripathy 52, T. Tripathy 48, S. Trogolo 33, V.
Trubnikov 3, W.H. Trzaska 117, T.P. Trzcinski 136, A. Tumkin 141, R. Turrisi
55, T.S. Tveter 20, K. Ullaland 21, B. Ulukutlu 96, A. Uras 128, M. Urioni
56,134, G.L. Usai 23, M. Vala38, N. Valle 22, L.V.R. van Doremalen60, M. van
Leeuwen 85, C.A. van Veen 95, R.J.G. van Weelden 85, P. Vande Vyvre 33, D.
Varga 47, Z. Varga 47, M. Vasileiou 79, A. Vasiliev 141, O. Vázquez Doce 50,
O. Vazquez Rueda 116, V. Vechernin 141, E. Vercellin 25, S. Vergara Limón45,
R. Verma48, L. Vermunt 98, R. Vértesi 47, M. Verweij 60, L. Vickovic34, Z.
Vilakazi123, O. Villalobos Baillie 101, A. Villani 24, G. Vino 51, A.
Vinogradov 141, T. Virgili 29, M.M.O. Virta 117, V. Vislavicius76, A.
Vodopyanov 142, B. Volkel 33, M.A. Völkl 95, K. Voloshin141, S.A. Voloshin
137, G. Volpe 32, B. von Haller 33, I. Vorobyev 96, N. Vozniuk 141, J.
Vrláková 38, J. Wan40, C. Wang 40, D. Wang40, Y. Wang 40, Y. Wang 6, A.
Wegrzynek 33, F.T. Weiglhofer39, S.C. Wenzel 33, J.P. Wessels 126, J. Wiechula
65, J. Wikne 20, G. Wilk 80, J. Wilkinson 98, G.A. Willems 126, B. Windelband
95, M. Winn 130, J.R. Wright 109, W. Wu40, Y. Wu 120, R. Xu 6, A. Yadav 43,
A.K. Yadav 135, S. Yalcin 73, Y. Yamaguchi 93, S. Yang21, S. Yano 93, Z. Yin
6, I.-K. Yoo 17, J.H. Yoon 59, H. Yu12, S. Yuan21, A. Yuncu 95, V. Zaccolo 24,
C. Zampolli 33, F. Zanone 95, N. Zardoshti 33, A. Zarochentsev 141, P. Závada
63, N. Zaviyalov141, M. Zhalov 141, B. Zhang 6, C. Zhang 130, L. Zhang 40, S.
Zhang 40, X. Zhang 6, Y. Zhang120, Z. Zhang 6, M. Zhao 10, V. Zherebchevskii
141, Y. Zhi10, D. Zhou 6, Y. Zhou 84, J. Zhu 98,6, Y. Zhu6, S.C. Zugravel 57,
N. Zurlo 134,56

## Affiliation Notes

I Deceased
II Also at: Max-Planck-Institut fur Physik, Munich, Germany
III Also at: Italian National Agency for New Technologies, Energy and
Sustainable Economic Development (ENEA), Bologna, Italy
IV Also at: Dipartimento DET del Politecnico di Torino, Turin, Italy
V Also at: Department of Applied Physics, Aligarh Muslim University, Aligarh,
India
VI Also at: Institute of Theoretical Physics, University of Wroclaw, Poland
VII Also at: An institution covered by a cooperation agreement with CERN

## Collaboration Institutes

1 A.I. Alikhanyan National Science Laboratory (Yerevan Physics Institute)
Foundation, Yerevan, Armenia
2 AGH University of Krakow, Cracow, Poland
3 Bogolyubov Institute for Theoretical Physics, National Academy of Sciences
of Ukraine, Kiev, Ukraine
4 Bose Institute, Department of Physics and Centre for Astroparticle Physics
and Space Science (CAPSS), Kolkata, India
5 California Polytechnic State University, San Luis Obispo, California, United
States
6 Central China Normal University, Wuhan, China
7 Centro de Aplicaciones Tecnológicas y Desarrollo Nuclear (CEADEN), Havana,
Cuba
8 Centro de Investigación y de Estudios Avanzados (CINVESTAV), Mexico City and
Mérida, Mexico
9 Chicago State University, Chicago, Illinois, United States
10 China Institute of Atomic Energy, Beijing, China
11 China University of Geosciences, Wuhan, China
12 Chungbuk National University, Cheongju, Republic of Korea
13 Comenius University Bratislava, Faculty of Mathematics, Physics and
Informatics, Bratislava, Slovak Republic
14 COMSATS University Islamabad, Islamabad, Pakistan
15 Creighton University, Omaha, Nebraska, United States
16 Department of Physics, Aligarh Muslim University, Aligarh, India
17 Department of Physics, Pusan National University, Pusan, Republic of Korea
18 Department of Physics, Sejong University, Seoul, Republic of Korea
19 Department of Physics, University of California, Berkeley, California,
United States
20 Department of Physics, University of Oslo, Oslo, Norway
21 Department of Physics and Technology, University of Bergen, Bergen, Norway
22 Dipartimento di Fisica, Università di Pavia, Pavia, Italy
23 Dipartimento di Fisica dell’Università and Sezione INFN, Cagliari, Italy
24 Dipartimento di Fisica dell’Università and Sezione INFN, Trieste, Italy
25 Dipartimento di Fisica dell’Università and Sezione INFN, Turin, Italy
26 Dipartimento di Fisica e Astronomia dell’Università and Sezione INFN,
Bologna, Italy
27 Dipartimento di Fisica e Astronomia dell’Università and Sezione INFN,
Catania, Italy
28 Dipartimento di Fisica e Astronomia dell’Università and Sezione INFN,
Padova, Italy
29 Dipartimento di Fisica ‘E.R. Caianiello’ dell’Università and Gruppo
Collegato INFN, Salerno, Italy
30 Dipartimento DISAT del Politecnico and Sezione INFN, Turin, Italy
31 Dipartimento di Scienze MIFT, Università di Messina, Messina, Italy
32 Dipartimento Interateneo di Fisica ‘M. Merlin’ and Sezione INFN, Bari,
Italy
33 European Organization for Nuclear Research (CERN), Geneva, Switzerland
34 Faculty of Electrical Engineering, Mechanical Engineering and Naval
Architecture, University of Split, Split, Croatia
35 Faculty of Engineering and Science, Western Norway University of Applied
Sciences, Bergen, Norway
36 Faculty of Nuclear Sciences and Physical Engineering, Czech Technical
University in Prague, Prague, Czech Republic
37 Faculty of Physics, Sofia University, Sofia, Bulgaria
38 Faculty of Science, P.J. Šafárik University, Košice, Slovak Republic
39 Frankfurt Institute for Advanced Studies, Johann Wolfgang Goethe-
Universität Frankfurt, Frankfurt, Germany
40 Fudan University, Shanghai, China
41 Gangneung-Wonju National University, Gangneung, Republic of Korea
42 Gauhati University, Department of Physics, Guwahati, India
43 Helmholtz-Institut für Strahlen- und Kernphysik, Rheinische Friedrich-
Wilhelms-Universität Bonn, Bonn, Germany
44 Helsinki Institute of Physics (HIP), Helsinki, Finland
45 High Energy Physics Group, Universidad Autónoma de Puebla, Puebla, Mexico
46 Horia Hulubei National Institute of Physics and Nuclear Engineering,
Bucharest, Romania
47 HUN-REN Wigner Research Centre for Physics, Budapest, Hungary
48 Indian Institute of Technology Bombay (IIT), Mumbai, India
49 Indian Institute of Technology Indore, Indore, India
50 INFN, Laboratori Nazionali di Frascati, Frascati, Italy
51 INFN, Sezione di Bari, Bari, Italy
52 INFN, Sezione di Bologna, Bologna, Italy
53 INFN, Sezione di Cagliari, Cagliari, Italy
54 INFN, Sezione di Catania, Catania, Italy
55 INFN, Sezione di Padova, Padova, Italy
56 INFN, Sezione di Pavia, Pavia, Italy
57 INFN, Sezione di Torino, Turin, Italy
58 INFN, Sezione di Trieste, Trieste, Italy
59 Inha University, Incheon, Republic of Korea
60 Institute for Gravitational and Subatomic Physics (GRASP), Utrecht
University/Nikhef, Utrecht, Netherlands
61 Institute of Experimental Physics, Slovak Academy of Sciences, Košice,
Slovak Republic
62 Institute of Physics, Homi Bhabha National Institute, Bhubaneswar, India
63 Institute of Physics of the Czech Academy of Sciences, Prague, Czech
Republic
64 Institute of Space Science (ISS), Bucharest, Romania
65 Institut für Kernphysik, Johann Wolfgang Goethe-Universität Frankfurt,
Frankfurt, Germany
66 Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México,
Mexico City, Mexico
67 Instituto de Física, Universidade Federal do Rio Grande do Sul (UFRGS),
Porto Alegre, Brazil
68 Instituto de Física, Universidad Nacional Autónoma de México, Mexico City,
Mexico
69 iThemba LABS, National Research Foundation, Somerset West, South Africa
70 Jeonbuk National University, Jeonju, Republic of Korea
71 Johann-Wolfgang-Goethe Universität Frankfurt Institut für Informatik,
Fachbereich Informatik und Mathematik, Frankfurt, Germany
72 Korea Institute of Science and Technology Information, Daejeon, Republic of
Korea
73 KTO Karatay University, Konya, Turkey
74 Laboratoire de Physique Subatomique et de Cosmologie, Université Grenoble-
Alpes, CNRS-IN2P3, Grenoble, France
75 Lawrence Berkeley National Laboratory, Berkeley, California, United States
76 Lund University Department of Physics, Division of Particle Physics, Lund,
Sweden
77 Nagasaki Institute of Applied Science, Nagasaki, Japan
78 Nara Women’s University (NWU), Nara, Japan
79 National and Kapodistrian University of Athens, School of Science,
Department of Physics , Athens, Greece
80 National Centre for Nuclear Research, Warsaw, Poland
81 National Institute of Science Education and Research, Homi Bhabha National
Institute, Jatni, India
82 National Nuclear Research Center, Baku, Azerbaijan
83 National Research and Innovation Agency - BRIN, Jakarta, Indonesia
84 Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark
85 Nikhef, National institute for subatomic physics, Amsterdam, Netherlands
86 Nuclear Physics Group, STFC Daresbury Laboratory, Daresbury, United Kingdom
87 Nuclear Physics Institute of the Czech Academy of Sciences, Husinec-Řež,
Czech Republic
88 Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States
89 Ohio State University, Columbus, Ohio, United States
90 Physics department, Faculty of science, University of Zagreb, Zagreb,
Croatia
91 Physics Department, Panjab University, Chandigarh, India
92 Physics Department, University of Jammu, Jammu, India
93 Physics Program and International Institute for Sustainability with Knotted
Chiral Meta Matter (SKCM2), Hiroshima University, Hiroshima, Japan
94 Physikalisches Institut, Eberhard-Karls-Universität Tübingen, Tübingen,
Germany
95 Physikalisches Institut, Ruprecht-Karls-Universität Heidelberg, Heidelberg,
Germany
96 Physik Department, Technische Universität München, Munich, Germany
97 Politecnico di Bari and Sezione INFN, Bari, Italy
98 Research Division and ExtreMe Matter Institute EMMI, GSI Helmholtzzentrum
für Schwerionenforschung GmbH, Darmstadt, Germany
99 Saga University, Saga, Japan
100 Saha Institute of Nuclear Physics, Homi Bhabha National Institute,
Kolkata, India
101 School of Physics and Astronomy, University of Birmingham, Birmingham,
United Kingdom
102 Sección Física, Departamento de Ciencias, Pontificia Universidad Católica
del Perú, Lima, Peru
103 Stefan Meyer Institut für Subatomare Physik (SMI), Vienna, Austria
104 SUBATECH, IMT Atlantique, Nantes Université, CNRS-IN2P3, Nantes, France
105 Sungkyunkwan University, Suwon City, Republic of Korea
106 Suranaree University of Technology, Nakhon Ratchasima, Thailand
107 Technical University of Košice, Košice, Slovak Republic
108 The Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy of
Sciences, Cracow, Poland
109 The University of Texas at Austin, Austin, Texas, United States
110 Universidad Autónoma de Sinaloa, Culiacán, Mexico
111 Universidade de São Paulo (USP), São Paulo, Brazil
112 Universidade Estadual de Campinas (UNICAMP), Campinas, Brazil
113 Universidade Federal do ABC, Santo Andre, Brazil
114 Universitatea Nationala de Stiinta si Tehnologie Politehnica Bucuresti,
Bucharest, Romania
115 University of Cape Town, Cape Town, South Africa
116 University of Houston, Houston, Texas, United States
117 University of Jyväskylä, Jyväskylä, Finland
118 University of Kansas, Lawrence, Kansas, United States
119 University of Liverpool, Liverpool, United Kingdom
120 University of Science and Technology of China, Hefei, China
121 University of South-Eastern Norway, Kongsberg, Norway
122 University of Tennessee, Knoxville, Tennessee, United States
123 University of the Witwatersrand, Johannesburg, South Africa
124 University of Tokyo, Tokyo, Japan
125 University of Tsukuba, Tsukuba, Japan
126 Universität Münster, Institut für Kernphysik, Münster, Germany
127 Université Clermont Auvergne, CNRS/IN2P3, LPC, Clermont-Ferrand, France
128 Université de Lyon, CNRS/IN2P3, Institut de Physique des 2 Infinis de
Lyon, Lyon, France
129 Université de Strasbourg, CNRS, IPHC UMR 7178, F-67000 Strasbourg, France,
Strasbourg, France
130 Université Paris-Saclay, Centre d’Etudes de Saclay (CEA), IRFU, Départment
de Physique Nucléaire (DPhN), Saclay, France
131 Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
132 Università degli Studi di Foggia, Foggia, Italy
133 Università del Piemonte Orientale, Vercelli, Italy
134 Università di Brescia, Brescia, Italy
135 Variable Energy Cyclotron Centre, Homi Bhabha National Institute, Kolkata,
India
136 Warsaw University of Technology, Warsaw, Poland
137 Wayne State University, Detroit, Michigan, United States
138 Yale University, New Haven, Connecticut, United States
139 Yonsei University, Seoul, Republic of Korea
140 Zentrum für Technologie und Transfer (ZTT), Worms, Germany
141 Affiliated with an institute covered by a cooperation agreement with CERN
142 Affiliated with an international laboratory covered by a cooperation
agreement with CERN.