2023 248 03 November

$\rm{K}^{+}\rm{K}^{-}$ photoproduction

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

$\rm{K}^{+}\rm{K}^{-}$ pairs may be produced in photonuclear collisions,
either from the decays of photoproduced $\phi(1020)$ mesons, or directly as
non-resonant $\rm{K}^{+}\rm{K}^{-}$ pairs. Measurements of
$\rm{K}^{+}\rm{K}^{-}$ photoproduction probe the couplings between the
$\phi(1020)$ and charged kaons with photons and nuclear targets. We present
the first measurement of coherent photoproduction of $\rm{K}^{+}\rm{K}^{-}$
pairs on lead ions in ultra-peripheral collisions using the ALICE detector,
including the first invesstigation of direct $\rm{K}^{+}\rm{K}^{-}$
production. There is significant $\rm{K}^{+}\rm{K}^{-}$ production at low
transverse momentum, consistent with coherent photoproduction on lead targets.
In the mass range $1.1<M_{\rm{KK}}<1.4$ GeV/$c^{2}$ above the $\phi(1020)$
resonance, for rapidity $|y_{\rm{KK}}|<0.8$ and $p_{\rm{T,KK}}$ $<$ 0.1
GeV/$c$, the measured coherent photoproduction cross section is
$\mathrm{d}\sigma/\mathrm{d}y$ = 3.37 $\pm\ 0.61$ (stat.) $\pm\ 0.15$ (syst.)
mb. The centre-of-mass energy per nucleon of the photon–nucleus (Pb) system
$W_{\gamma\mathrm{Pb,n}}$ ranges from 33 to 188 GeV, far higher than previous
measurements on heavy-nucleus targets. The cross section is larger than
expected for $\phi(1020)$ photoproduction alone. The mass spectrum is fit to a
cocktail consisting of $\phi(1020)$ decays, direct $\rm{K}^{+}\rm{K}^{-}$
photoproduction, and interference between the two. The confidence regions for
the amplitude and relative phase angle for direct $\rm{K}^{+}\rm{K}^{-}$
photoproduction are presented.

Introduction. High-energy photoproduction is an important technique for
studying hadronic interactions. Ultra-peripheral collisions (UPCs) of
relativistic ions are a tool for studying photonuclear interactions at
energies far higher than those available elsewhere [1, 2, 3, 4]. The
electromagnetic field of one nucleus forms an intense virtual-photon beam that
can interact with nuclei from the opposing beam. UPC interactions occur when
the impact parameter ($b$) between the two nuclei is large enough, e.g. $b$ is
greater than the sum of the nuclear radii, so that no obscuring hadron–hadron
interactions occur.

A photon can fluctuate into a quark-antiquark pair (dipole) that scatters
elastically from a target nucleus, emerging as a real vector meson [5]. The
elastic scattering is mediated by the Pomeron, which is a colourless object
and to lowest order, composed of two gluons. The exchange involves the quantum
numbers of the vacuum, so following the Vector Meson Dominance (VMD) model,
the outgoing meson has the same quantum numbers $J^{PC}=1^{--}$ as the
incident photon [6]. Alternatively, the photon can fluctuate directly into a
virtual meson pair, like $\pi^{+}\pi^{-}$ or $\rm{K}^{+}\rm{K}^{-}$. One of
the mesons can then scatter elastically from the target, making the pair real.
Since these channels are indistinguishable, meson pairs from the decay of
vector mesons ($\rho^{0}\rightarrow\pi^{+}\pi^{-}$ or $\phi(1020)\rightarrow$
$\rm{K}^{+}\rm{K}^{-}$) can interfere with the directly produced pairs. The
production amplitude use two terms: the resonance is described using a Breit-
Wigner distribution expressed in the Jackson form, with amplitude $A_{\phi}$,
and there is in addition a continuum component with amplitude $B_{\rm{KK}}$
[7, 8, 9], giving

$\frac{d\sigma}{dM_{\rm{KK}}}=\bigg{|}A_{\phi}\frac{\sqrt{M_{\rm{KK}}M_{\phi}\Gamma_{\phi}}}{M_{\rm{KK}}^{2}-M_{\phi}^{2}+iM_{\phi}\Gamma_{\phi}}+B_{\rm{KK}}\bigg{|}^{2},$
(1)

where $M_{\phi}=1019.416\pm 0.016$ MeV/$c^{2}$ [10] and $\Gamma_{\phi}$ are
the $\phi(1020)$ mass and mass-dependent width, respectively, with

$\Gamma_{\phi}=\Gamma_{0}\frac{M_{\phi}}{M_{\rm{KK}}}\bigg{(}\frac{M_{\rm{KK}}^{2}-4M_{\rm{K}}^{2}}{M_{\phi}^{2}-4M_{\rm{K}}^{2}}\bigg{)}^{3/2}.$
(2)

Here $\Gamma_{0}=4.249\pm 0.013$ MeV/$c^{2}$ is the native $\phi$(1020) width
and $M_{\rm{K}}=493.677\pm 0.016$ MeV/$c^{2}$ is the kaon mass [10]. Both
$A_{\phi}$ and $B_{\rm{KK}}$ are complex, but only their relative phase
matters. By taking $A_{\phi}$ to be real, the relative phase is encoded in
$B_{\rm{KK}}$. Far above the $\phi(1020)$ resonance (many $\Gamma_{0}$), the
mass-dependent width rises, and the cross section declines smoothly. One
difference between the $\rm{K}^{+}\rm{K}^{-}$ and $\pi^{+}\pi^{-}$ systems is
that the branching ratio $\phi(1020)\rightarrow K^{+}K^{-}$ is only 49.1%
[10], while the $\rho^{0}$ almost always decays to $\pi^{+}\pi^{-}$. This
branching ratio is included in $A_{\phi}$. Ryskin and Shabelski considered the
direct dikaon contribution to the total dikaon cross section, and concluded
that it should be small and with a relative phase angle near zero [11]. A
later calculation predicted that the dikaon system should behave similarly to
the dipions, with a small correction to the width to account for 3-body
$\phi(1020)$ decays [9].

The transverse momentum $p_{\rm{T}}$ of the meson depends on the production
mechanism, so it is important in selecting coherent photoproduction events,
where a dipole or virtual meson pair scatters from the target nucleus. The
meson $p_{\rm{T}}$ is the vector sum of the photon $p_{\rm{T}}$ and the
Pomeron $p_{\rm{T}}$, which usually dominates [12]. For coherent production,
its scale is controlled by the form factor of the target nucleus. Destructive
interference between the amplitudes for production on the two nuclei can
reduce the cross section at low $p_{\rm{T}}$, especially near midrapidity [12,
13]. In incoherent production, when a dipole or virtual meson pair scatters
from a single nucleon, the typical $p_{\rm{T}}$ is larger, around a few
hundred MeV/$c$.

Previously, $\phi(1020)$ photoproduction has been studied at fixed-target
experiments [6, 14] and the HERA ep collider [15, 16, 17]. However, the direct
$\rm{K}^{+}\rm{K}^{-}$ contribution has not yet been observed. The H1
collaboration searched for skewing in the $\phi$ Breit-Wigner peak due to
direct $\rm{K}^{+}\rm{K}^{-}$ production (in electroproduction), but found no
evidence for it [17]. In contrast, the $\rho^{0}+{\rm direct}\ \pi^{+}\pi^{-}$
state has been studied in both UPCs [18, 19, 20, 21, 22, 23] and, at lower
energy, at fixed-target experiments [24, 6]. The $\pi^{+}\pi^{-}$ mass spectra
are well fit by the sum of amplitudes for $\rho^{0}$ and direct
$\pi^{+}\pi^{-}$, with a high-statistics fit exhibiting additional
interference from $\omega\rightarrow\pi^{+}\pi^{-}$ [25, 20]. Higher-mass
$\pi^{+}\pi^{-}$ states have also been seen [26, 27, 21].

This letter reports on exclusive photoproduction of the $\rm{K}^{+}\rm{K}^{-}$
final state, from the decay of the $\phi(1020)$ and direct production. The
data covers the mass region $1.1<M_{\rm{KK}}<1.4$ GeV/$c^{2}$. This is
significantly above the $\phi(1020)$ peak, with the lower mass limit at about
$M_{\phi}+18\Gamma_{0}$.

The cross sections are measured at the centre-of-mass energy per nucleon of
the photon–nucleus (Pb) system $W_{\gamma\mathrm{Pb,n}}$, where
$W_{\gamma\mathrm{Pb,n}}$ varies from 33 to 188 GeV, depending on
$M_{\rm{KK}}$ and rapidity. This range of energies is more than an order of
magnitude higher than previous studies using heavy-nucleus targets [6, 14].

Detector and data. The results presented in this letter are based on the data
collected in 2015 by the ALICE experiment [28, 29], with Pb–Pb collisions at a
center-of-mass energy per nucleon pair $\sqrt{s_{\mathrm{NN}}}~{}=~{}5.02$
TeV. A dedicated trigger was used to select candidate UPC events [21],
rejecting any activity within the time windows for nominal beam–beam
interactions, using the scintillator detectors V0 [30] and AD [31, 32] located
at large positive and negative pseudorapidity. In addition, the trigger
required that the Silicon Pixel Detector (SPD), the two innermost layers of
the inner tracking system (ITS) [33], measured at least two short track
segments with a large opening angle in azimuth.

The time projection chamber (TPC) covering the pseudorapidity acceptance of
$\left|\eta\right|~{}<~{}0$.9 was used for charged particle tracking and
vertexing together with the ITS as well as for particle identification based
on the specific ionization energy loss, $\textrm{d}E/\textrm{d}x$ [34].

Analysis Procedure. The analysis selected events with exactly two good tracks.
The tracks were required to have at least 50 hits (clusters) in the TPC, at
least one hit in each of the two layers of the SPD, and to have the distance-
of-closest approach to the event vertex of less than
$0.0182+0.035/p_{\rm{T}}^{1.01}$ cm in the transverse plane and less than 2 cm
along the beam direction. The two selected tracks having opposite charge are
reconstructed as $\rm{K}^{+}\rm{K}^{-}$ pair candidates under the kaon mass
hypothesis. As there are no same-charge pairs passing the particle
identification criteria, the contribution of uncorrelated background could be
ignored in this analysis.

Kaons are identified based on the $\textrm{d}E/\textrm{d}x$ measurement in the
TPC. The selection criteria are applied to the variable $n_{\sigma_{i}}$, the
deviation of the measured signal from the expected signal in units of the
$\textrm{d}E/\textrm{d}x$ measurement uncertainty for each particle hypothesis
$i$. Since the ratio of signal $\rm{K}^{+}\rm{K}^{-}$ pairs to background
$\pi^{+}\pi^{-}$ pairs is less than 0.1%, stringent particle identification
criteria are introduced. First, the tracks in each pair are required to
satisfy $|n_{\sigma_{\rm K}}|<3$. In addition, the tracks which are compatible
within $2n_{\sigma_{\pi,\mu,e}}$ are excluded to reject $\pi^{+}\pi^{-}$ pairs
as well as dilepton pairs from the $\gamma\gamma\rightarrow l^{+}l^{-}$
process.

The contamination of the $\rm{K}^{+}\rm{K}^{-}$ pair candidates by the
misidentified particles is estimated from the 2-dimensional $n_{\sigma_{K}}$
distribution of the two tracks in each pair. While the signal
$\rm{K}^{+}\rm{K}^{-}$ pairs have a two-dimensional Gaussian-like distribution
centered at (0,0), background pairs are clustered at non-zero values. For 1.1
$<M_{\rm{KK}}<$ 1.4 GeV/$c^{2}$, the contamination is negligible as the signal
and background distributions are well separated from each other. At higher
masses, the expected difference in $\textrm{d}E/\textrm{d}x$ between kaons and
lighter particles decreases, so they become indistinguishable in some
$n_{\sigma_{K}}$ regions. Therefore, the invariant mass range above 1.4
GeV/$c^{2}$ is not used in the analysis.

Measurement of the cross section. The invariant mass differential cross
section of exclusive $\rm{K}^{+}\rm{K}^{-}$ photoproduction is obtained by
correcting the number of $\rm{K}^{+}\rm{K}^{-}$ candidates ($N_{\rm{KK}}$)
found in the rapidity interval of $|y_{\rm{KK}}|<0.8$ and in the $p_{\rm{T}}$
interval of $p_{\rm{T,KK}}<0.1$ GeV/$c$ by acceptance and efficiency
($\mathcal{A}\times\epsilon$),

$\frac{\mathrm{d}^{2}\it{\sigma}}{\mathrm{d}\it{M}_{\rm{KK}}\mathrm{d}y_{\rm{KK}}}=\frac{\it{N}_{\rm{KK}}\times
f_{\mathrm{pileup}}}{(\mathcal{A}\times\epsilon)\times\mathcal{L}\times\Delta
M_{\rm{KK}}\times\Delta y_{\rm{KK}}}.$ (3)

The $\mathcal{A}\times\epsilon$ is computed using a dedicated Monte Carlo
simulation with STARlight [35] for the $\rm{K}^{+}\rm{K}^{-}$ pairs from
direct production and $\phi(1020)$ decays.

The generated $\rm{K}^{+}\rm{K}^{-}$ pairs are transported through the
detector setup using a GEANT 3 model [36] to simulate a realistic detector
response. The corresponding integrated luminosity ($\mathcal{L}$) for the data
sample is 0.406 $\mu\rm{b}^{-1}$ with a relative systematic uncertainty of
2.6% [37]. Some events are lost due to pileup, when another interaction
creates a signal in one of the veto detectors. The pileup events mainly come
from two-photon production of $\rm{e}^{+}\rm{e}^{-}$ pairs, and their effect
is taken into account with an additional correction factor,
$f_{\mathrm{pileup}}$ = 11.1 $\pm$ 3.8% [21]. Similarly, the
$p_{\rm{T}}^{2}$-differential cross section of exclusive
$\rm{K}^{+}\rm{K}^{-}$ photoproduction in 1.1 $<M_{\rm{KK}}<$ 1.4 GeV/$c^{2}$
is measured,

$\frac{\mathrm{d}^{2}\it{\sigma}}{\mathrm{d}p_{\rm{T,KK}}^{2}\mathrm{d}\it{y}_{\rm{KK}}}=\frac{\it{N}_{\rm{KK}}\times
f_{\mathrm{pileup}}}{(\mathcal{A}\times\epsilon)\times\mathcal{L}\times\Delta
p_{\rm{T,KK}}^{2}\times\Delta y_{\rm{KK}}}.$ (4)

Systematic uncertainties. The systematic uncertainties of the measured cross
section are estimated for the track selection criteria (1.5%) and the track
matching between ITS and TPC (4%) as well as for the acceptance and efficiency
(1%), without dependence on $p_{\rm{T,KK}}$, $y_{\rm{KK}}$ and $M_{\rm{KK}}$
[21]. Uncertainties of 1% and 3.8% are included for the trigger efficiency and
for the pileup correction, respectively [21]. The uncertainty of the
luminosity (2.6%) results from the uncertainty of the reference luminosity in
the cross section of 2.5% [37] and an additional 0.4% uncertainty on the live-
time of readout detectors used for the trigger.

The systematic uncertainty of the kaon identification is estimated as a
function of $p_{\rm{T,KK}}$ and $M_{\rm{KK}}$ to account for the track
momentum dependence in the kaon identification performance. The expected
signal of TPC $\textrm{d}E/\textrm{d}x$ for each particle hypothesis is varied
in the MC simulations by the maximum difference of the signal in data and MC
simulations. Then, $n_{\sigma_{i}}$ and the corresponding kaon identification
efficiency are recalculated. The resulting uncertainty is negligible for 1.1
$<M_{\rm{KK}}<$ 1.2 GeV/$c^{2}$ and amounts to 3.9% and 6.5% for 1.2
$<M_{\rm{KK}}<$ 1.3 GeV/$c^{2}$ and 1.3 $<M_{\rm{KK}}<$ 1.4 GeV/$c^{2}$,
respectively. The systematic uncertainty increases slowly as a function of
$p_{\rm{T,KK}}$, from 3.4% for $p_{\rm{T,KK}}$ $<$ 0.025 GeV/$c$ to 4.9% for
0.1 $<p_{\rm{T,KK}}<$ 0.2 GeV/$c$. Over most of the kinematic range, this is
the largest single systematic uncertainty.

Results. Figure 1 shows the $p_{\rm{T}}^{2}$ spectrum of the selected
$\rm{K}^{+}\rm{K}^{-}$ events. Most of the cross section is concentrated below
$p_{\rm{T,KK}}^{2}$ $<$ 0.01 $(\mathrm{Ge\kern-1.00006ptV}/c)^{2}$ ,
consistent with coherent photoproduction. Some events are seen at higher
values of $p_{\rm{T,KK}}^{2}$; these may be from incoherent production. The
coherent data are well described with an exponential shape
$\rm{d}^{2}\it{\sigma}/\rm{d}\it{y}\rm{d}\it{p}_{\rm{T}}^{\rm{2}}=a\exp(-bp_{\rm{T}}^{\rm{2}})$,
where the slope parameter $b$ is fixed to that measured for coherent
$\rho^{0}$ photoproduction on lead, $~{}{b=428\ \pm\ 6\ ({\rm stat.})\ \pm\
15\ ({\rm syst.})}$ $(\mathrm{Ge\kern-1.00006ptV}/c)^{-2}$ [38]. The figure
inset shows an expanded view of the low $p_{\rm{T}}^{2}$ region, and compares
the data with two STARlight calculations, with and without an interference
between photon emission from the two nuclei [12, 35], which exhibit different
trends only at very low $p_{\rm{T}}$. The curve with interference is a
slightly better match to the data.

Figure 1: Differential cross section as a function of
$\it{p}_{\rm{T,KK}}^{\rm{2}}$ for exclusive $\rm{K}^{+}\rm{K}^{-}$
photoproduction in Pb–Pb UPCs at $\sqrt{s_{\rm{NN}}}$= 5.02 TeV and
$|y_{\rm{KK}}|<0.8$. The lines and boxes across the data points represent
statistical and systematic uncertainties, respectively. The dashed blue line
and band are the result of a fit to an exponential with the fixed slope
parameter $b=428\ \pm\ 6\ ({\rm stat.})\ \pm\ 15\ ({\rm syst.})$
$(\mathrm{Ge\kern-1.00006ptV}/c)^{-2}$ , from a previous result on $\rho^{0}$
production [38] (see text for details). The inset shows two curves from
STARlight with and without interference between the two photon directions [12,
35].

The invariant mass dependent cross section for coherent $\rm{K}^{+}\rm{K}^{-}$
photoproduction is shown in Fig. 2. The data with $p_{\rm{T,KK}}^{2}$ $>$ 0.01
$(\mathrm{Ge\kern-1.00006ptV}/c)^{2}$ are mostly from incoherent
photoproduction, so are not included in the cross sections. The integrated
cross section $\mathrm{d}\sigma/\mathrm{d}y_{\rm{KK}}$ = 3.37 $\pm\ 0.61$
(stat.) $\pm\ 0.15$ (syst.) mb is measured in the mass range
$1.1<M_{\rm{KK}}<1.4$ GeV/$c^{2}$ for rapidity $|y_{\rm{KK}}|<0.8$ and
$p_{\rm{T,KK}}^{2}$ $<$ 0.01 $(\mathrm{Ge\kern-1.00006ptV}/c)^{2}$ .
$\rm{K}^{+}\rm{K}^{-}$ pairs could be produced by other reactions, such as
$\gamma\gamma\rightarrow f_{2}(1270)\rightarrow$ $\rm{K}^{+}\rm{K}^{-}$, but
calculations indicate that the expected cross section for this process [39]
estimated using STARlight [40] is a negligible fraction of the
$\rm{K}^{+}\rm{K}^{-}$ photoproduction cross section as illustrated in Fig. 2.

Figure 2: Differential cross section of coherent $\rm{K}^{+}\rm{K}^{-}$
photoproduction as a function $\it{M_{\mathrm{KK}}}$ in Pb–Pb UPCs at
$\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV in $|y_{\mathrm{KK}}|\ <\ 0.8$. The lines
and boxes along the data points represent statistical and systematic
uncertainties, respectively. The green solid line presents the best fit result
of $|B_{\rm{KK}}/A_{\phi}|=0.28$ $(\mathrm{Ge\kern-1.00006ptV}/c^{2})^{-1/2}$
and $\varphi$ = 0.06 rad together with the 1$\sigma$ bounds of the fit in a
green band. The blue dashed curve shows the best fit with
$|B_{\pi\pi}/A_{\rho}|=0.54$ $(\mathrm{Ge\kern-1.00006ptV}/c^{2})^{-1/2}$ [21]
and $\varphi$ = 1.46 rad (the best-fit values for $\rho$ plus direct
$\pi^{+}\pi^{-}$) [20]. The black dotted line represents the curves under the
hypothesis of $|B_{\rm{KK}}/A_{\phi}|=0$, showing only the
$\phi(1020)\rightarrow$ $\rm{K}^{+}\rm{K}^{-}$ contribution. The grey band
indicates the impact of the systematic uncertainty from the $\phi(1020)$ meson
cross section, showing a 25$\%$ variation.

The measured cross section is fitted to a combination of
$\phi(1020)\rightarrow$ $\rm{K}^{+}\rm{K}^{-}$ and direct
$\rm{K}^{+}\rm{K}^{-}$ production according to Eq. (1). The amplitude of
$\phi(1020)\rightarrow$ $\rm{K}^{+}\rm{K}^{-}$ ($A_{\phi}$) was calculated
from previous photoproduction measurements on protons [41, 15, 42] and a
Glauber calculation [40], with a branching ratio of
$\phi(1020)\rightarrow\rm{K}^{+}\rm{K}^{-}(49.2\ \pm\ 0.5\%$) [10]. The
reference $\phi(1020)$ cross sections did not include a direct
$\rm{K}^{+}\rm{K}^{-}$ contribution. This could have had a small effect on the
measured $A_{\phi}$.

A 25% uncertainty in $A_{\phi}$ is estimated to account for the uncertainty in
the previous measurements [41, 15] and the uncertainty in the Glauber approach
[43]. STARlight predictions for $\rho^{0}$ production under similar
circumstances were 15-20% below the data [21], while predictions for $J/\psi$
production were about 15-50% above the data, depending on rapidity [44]. The
latter is not surprising since STARlight does not include gluon shadowing. The
$\phi(1020)$ is intermediate in mass, but closer to the $\rho^{0}$, so a $\pm
25\%$ uncertainty in the cross section seems conservative for the
$\phi(1020)$.

The black dotted line and surrounding shaded region in Fig. 2 show the
$\phi$-only prediction, with the 25% uncertainty. The measured cross section
is about 2.1 $\sigma$ above the expected $\phi(1020)\rightarrow$
$\rm{K}^{+}\rm{K}^{-}$ cross section in the range $1.1<M_{\rm{KK}}<1.4$
GeV/$c^{2}$. Also shown, with a blue dashed line, is the prediction using the
values $|B_{\pi\pi}/A_{\rho}|=0.54\ \pm\ 0.01$ (stat.) $\pm\ 0.02$ (syst.)
$(\mathrm{Ge\kern-1.00006ptV}/c^{2})^{-1/2}$ [21] and relative phase angle
$\varphi=1.46\ \pm\ 0.11$ (stat.) $\pm\ 0.07$ (syst.) rad [20] found for
$\rho^{0}$ plus the direct $\pi^{+}\pi^{-}$ system. The resulting
$\rm{d}^{2}\sigma/\rm{d}\it{M_{\rm{KK}}}\rm{d}\it{y_{\rm{KK}}}$ is slightly
below, but consistent with the data points. The best fit of Eq. (1) found the
relative fraction of direct $\rm{K}^{+}\rm{K}^{-}$ contribution with respect
to $A_{\phi}$ to be $|B_{\rm{KK}}/A_{\phi}|=0.28$
$(\mathrm{Ge\kern-1.00006ptV}/c^{2})^{-1/2}$ , with the relative phase angle
between $\phi(1020)\rightarrow$ $\rm{K}^{+}\rm{K}^{-}$ and direct
$\rm{K}^{+}\rm{K}^{-}$ is 0.06 rad.

Figure 3 shows the confidence regions for $|B_{\rm{KK}}/A_{\phi}|$ and
$\varphi$. The horseshoe shape of the curves including the first investigation
of direct $K^{+}K^{-}$ production is because of the large correlations between
the two parameters. If the interference is constructive, a small direct
$\rm{K}^{+}\rm{K}^{-}$ component is preferred, while a large
$\rm{K}^{+}\rm{K}^{-}$ component is better fit with destructive interference.
The invariant mass dependent cross section curves corresponding to the 68$\%$
confidence region are shown as a $1\sigma$ green band in Fig. 3, while the
dashed blue band shows the 95% confidence level. We do not include the
uncertainty on the cross section $\sigma(\gamma A\rightarrow\phi(1020)A)$
within the figure. As $\sigma(\gamma A\ \rightarrow\ \phi(1020)A)$ is reduced
or increased, it moves the confidence region left or right, with relatively
small changes to the shape. One standard deviation ($\pm\ 1\sigma$) changes in
$\sigma(\gamma A\rightarrow\phi(1020)A)$ move $|B_{\rm{KK}}/A_{\phi}|$ by
about $\pm\ 0.15$ $(\mathrm{Ge\kern-1.00006ptV}/c^{2})^{-1/2}$ respectively.
The best-fit point for the $\pi\pi$ system is fully compatible with the
current $\rm{K}^{+}\rm{K}^{-}$ measurement.

Figure 3: Confidence regions for the relative fraction of direct
$\rm{K}^{+}\rm{K}^{-}$ contribution with respect to the amplitude of
$\phi(1020)\rightarrow$ $\rm{K}^{+}\rm{K}^{-}$ ($|B_{\rm{KK}}/A_{\phi}|$) and
the relative phase angle between $\phi(1020)\rightarrow$$\rm{K}^{+}\rm{K}^{-}$
and direct $\rm{K}^{+}\rm{K}^{-}$ ($\varphi$). The best fit is shown as a red
dot at $|B_{\rm{KK}}/A_{\phi}|=0.28$
$(\mathrm{Ge\kern-1.00006ptV}/c^{2})^{-1/2}$ and $\varphi=$ 0.06 rad found
with $\chi^{2}/\rm{ndf_{best\ fit}}=0.3$, while a pink square at the
$|B_{\pi\pi}/A_{\rho}|=0.54\ \pm\ 0.01$ (stat.) $\pm\ 0.02$ (syst.)
$(\mathrm{Ge\kern-1.00006ptV}/c^{2})^{-1/2}$ [21] and relative phase angle
$\varphi=1.46\ \pm\ 0.11$ (stat.) $\pm\ 0.07$ (syst.) rad [20] indicates the
best-fit values for $\rho$ plus direct $\pi^{+}\pi^{-}$. The green solid line
and blue dashed line represent the boundary of 68% and 95% confidence regions,
respectively.

Looking ahead, during LHC Run 3, ALICE will collect a far larger data sample,
due to the increased luminosity [45] and continuous-readout data acquisition
system [46, 47], which eliminates the need for a restrictive, prescaled
trigger. Improved precision measurement of coherent
$\mathrm{K}^{+}\mathrm{K}^{-}$ photoproduction by the reduction of statistical
uncertainty and an improved tracking will make it possible to further
disentangle the resonance and non-resonance contributions with their relative
phase angle.

Conclusions. We report the first study of coherent $\rm{K}^{+}\rm{K}^{-}$
photoproduction in ultra-peripheral collisions at $W_{\gamma\mathrm{Pb,n}}$
from 33 to 188 GeV, in the range $1.1<M_{\rm{KK}}<1.4$ GeV/$c^{2}$ and
$|y_{\mathrm{KK}}|<0.8$. The $\rm{d}^{2}\sigma/\rm{d}\it{p_{\rm
T,KK}^{2}}\rm{d}\it{y_{\rm{KK}}}$ is concentrated below $p_{\rm{T,KK}}^{2}$
$<0.01\ $$(\mathrm{Ge\kern-1.00006ptV}/c)^{2}$ , consistent with coherent
photoproduction. The measured
$\rm{d}^{2}\sigma/\rm{d}\it{M_{\rm{KK}}}\rm{d}\it{y_{\rm{KK}}}$ below
$p_{\rm{T,KK}}^{2}$ $<$ 0.01 $(\mathrm{Ge\kern-1.00006ptV}/c)^{2}$ is about
2.1 $\sigma$ larger than what is expected from $\phi(1020)$ production alone
estimated based on HERA data with a Glauber model calculation, but is
consistent with a mixture of $\phi(1020)$ and direct $\rm{K}^{+}\rm{K}^{-}$
production. The fitted ratio of $\phi(1020)$ production to
$\rm{K}^{+}\rm{K}^{-}$ production is consistent with that seen for the
$\rho^{0}$ and direct $\pi^{+}\pi^{-}$.

## 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) and National Science, Research and Innovation Fund (NSRF via PMU-B B05F650021), Thailand; 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.

## References

  * [1] C. A. Bertulani, S. R. Klein, and J. Nystrand, “Physics of ultra-peripheral nuclear collisions”, Ann. Rev. Nucl. Part. Sci. 55 (2005) 271–310, arXiv:nucl-ex/0502005.
  * [2] A. J. Baltz, “The Physics of Ultraperipheral Collisions at the LHC”, Phys. Rept. 458 (2008) 1–171, arXiv:0706.3356 [nucl-ex].
  * [3] J. G. Contreras and J. D. Tapia Takaki, “Ultra-peripheral heavy-ion collisions at the LHC”, Int. J. Mod. Phys. A 30 (2015) 1542012.
  * [4] S. Klein and P. Steinberg, “Photonuclear and Two-photon Interactions at High-Energy Nuclear Colliders”, Ann. Rev. Nucl. Part. Sci. 70 (2020) 323–354, arXiv:2005.01872 [nucl-ex].
  * [5] S. R. Klein and H. Mäntysaari, “Imaging the nucleus with high-energy photons”, Nature Rev. Phys. 1 (2019) 662–674, arXiv:1910.10858 [hep-ex].
  * [6] T. H. Bauer, R. D. Spital, D. R. Yennie, and F. M. Pipkin, “The Hadronic Properties of the Photon in High-Energy Interactions”, Rev. Mod. Phys. 50 (1978) 261. [Erratum: Rev.Mod.Phys. 51, 407 (1979)].
  * [7] P. Söding, “On the Apparent shift of the rho meson mass in photoproduction”, Phys. Lett. 19 (1966) 702–704.
  * [8] J. D. Jackson, “Remarks on the phenomenological analysis of resonances”, Nuovo Cim. 34 (1964) 1644–1666.
  * [9] P. Lebiedowicz, O. Nachtmann, and A. Szczurek, “Towards a complete study of central exclusive production of $K^{+}K^{-}$ pairs in proton-proton collisions within the tensor Pomeron approach”, Phys. Rev. D 98 (2018) 014001, arXiv:1804.04706 [hep-ph].
  * [10] Particle Data Group Collaboration, R. L. Workman et al., “Review of Particle Physics”, PTEP 2022 (2022) 083C01.
  * [11] M. G. Ryskin and Y. M. Shabelski, “Elastic rho-prime and phi meson photoproduction and electroproduction with nonresonant background”, Phys. Atom. Nucl. 62 (1999) 980–986, arXiv:hep-ph/9712437.
  * [12] S. R. Klein and J. Nystrand, “Interference in exclusive vector meson production in heavy ion collisions”, Phys. Rev. Lett. 84 (2000) 2330–2333, arXiv:hep-ph/9909237.
  * [13] STAR Collaboration, B. I. Abelev et al., “Observation of Two-source Interference in the Photoproduction Reaction Au Au —$>$ Au Au rho0”, Phys. Rev. Lett. 102 (2009) 112301, arXiv:0812.1063 [nucl-ex].
  * [14] R. M. Egloff et al., “Measurements of Elastic Rho and Phi Meson Photoproduction Cross-Sections on Protons from 30 GeV to 180 GeV”, Phys. Rev. Lett. 43 (1979) 657.
  * [15] ZEUS Collaboration, M. Derrick et al., “Measurement of elastic $\phi$ photoproduction at HERA”, Phys. Lett. B 377 (1996) 259–272, arXiv:hep-ex/9601009.
  * [16] ZEUS Collaboration, S. Chekanov et al., “Exclusive electroproduction of phi mesons at HERA”, Nucl. Phys. B 718 (2005) 3–31, arXiv:hep-ex/0504010.
  * [17] H1 Collaboration, F. D. Aaron et al., “Diffractive Electroproduction of rho and phi Mesons at HERA”, JHEP 05 (2010) 032, arXiv:0910.5831 [hep-ex].
  * [18] STAR Collaboration, C. Adler et al., “Coherent rho0 production in ultraperipheral heavy ion collisions”, Phys. Rev. Lett. 89 (2002) 272302, arXiv:nucl-ex/0206004.
  * [19] STAR Collaboration, B. I. Abelev et al., “$\rho^{0}$ photoproduction in ultraperipheral relativistic heavy ion collisions at $\sqrt{s_{NN}}$ = 200 GeV”, Phys. Rev. C 77 (2008) 034910, arXiv:0712.3320 [nucl-ex].
  * [20] STAR Collaboration, L. Adamczyk et al., “Coherent diffractive photoproduction of $\rho^{0}$mesons on gold nuclei at 200 GeV/nucleon-pair at the Relativistic Heavy Ion Collider”, Phys. Rev. C 96 (2017) 054904, arXiv:1702.07705 [nucl-ex].
  * [21] ALICE Collaboration, S. Acharya et al., “Coherent photoproduction of $\rho^{0}$ vector mesons in ultra-peripheral Pb-Pb collisions at $\sqrt{{\mathrm{s}}_{\mathrm{NN}}}$ = 5.02 TeV”, JHEP 06 (2020) 035, arXiv:2002.10897 [nucl-ex].
  * [22] ALICE Collaboration, S. Acharya et al., “First measurement of coherent $\rho$0 photoproduction in ultra-peripheral Xe–Xe collisions at sNN=5.44 TeV”, Phys. Lett. B 820 (2021) 136481, arXiv:2101.02581 [nucl-ex].
  * [23] CMS Collaboration, A. M. Sirunyan et al., “Measurement of exclusive $\rho(770)^{0}$ photoproduction in ultraperipheral pPb collisions at $\sqrt{s_{\mathrm{NN}}}=$ 5.02 TeV”, Eur. Phys. J. C 79 (2019) 702, arXiv:1902.01339 [hep-ex].
  * [24] FOCUS Collaboration, J. M. Link et al., “Observation of a $1750-MeV/c^{2}$ Enhancement in the Diffractive Photoproduction of $K^{+}K^{-}$”, Phys. Lett. B 545 (2002) 50–56, arXiv:hep-ex/0208027.
  * [25] H1 Collaboration, V. Andreev et al., “Measurement of Exclusive $\pi^{+}\pi^{-}$ and $\rho^{0}$ Meson Photoproduction at HERA”, Eur. Phys. J. C 80 (2020) 1189, arXiv:2005.14471 [hep-ex].
  * [26] ZEUS Collaboration, H. Abramowicz et al., “Exclusive electroproduction of two pions at HERA”, Eur. Phys. J. C 72 (2012) 1869, arXiv:1111.4905 [hep-ex].
  * [27] STAR Collaboration, S. R. Klein, “Ultra-Peripheral Collisions with gold ions in STAR”, PoS DIS2016 (2016) 188, arXiv:1606.02754 [nucl-ex].
  * [28] ALICE Collaboration, K. Aamodt et al., “The ALICE experiment at the CERN LHC”, JINST 3 (2008) S08002. https://dx.doi.org/10.1088/1748-0221/3/08/S08002.
  * [29] ALICE Collaboration, B. B. Abelev et al., “Performance of the ALICE Experiment at the CERN LHC”, Int. J. Mod. Phys. A 29 (2014) 1430044, arXiv:1402.4476 [nucl-ex].
  * [30] ALICE Collaboration, E. Abbas et al., “Performance of the ALICE VZERO system”, JINST 8 (2013) P10016, arXiv:1306.3130 [nucl-ex].
  * [31] LHC Forward Physics Working Group Collaboration, K. Akiba et al., “LHC Forward Physics”, J. Phys. G 43 (2016) 110201, arXiv:1611.05079 [hep-ph].
  * [32] M. Broz et al., “Performance of ALICE AD modules in the CERN PS test beam”, JINST 16 (2021) P01017, arXiv:2006.14982 [physics.ins-det].
  * [33] ALICE Collaboration, K. Aamodt et al., “Alignment of the ALICE Inner Tracking System with cosmic-ray tracks”, JINST 5 (2010) P03003, arXiv:1001.0502 [physics.ins-det].
  * [34] J. Alme et al., “The ALICE TPC, a large 3-dimensional tracking device with fast readout for ultra-high multiplicity events”, Nucl. Instrum. Meth. A 622 (2010) 316–367, arXiv:1001.1950 [physics.ins-det].
  * [35] S. R. Klein, J. Nystrand, J. Seger, Y. Gorbunov, and J. Butterworth, “STARlight: A Monte Carlo simulation program for ultra-peripheral collisions of relativistic ions”, Comput. Phys. Commun. 212 (2017) 258–268, arXiv:1607.03838 [hep-ph].
  * [36] R. Brun, F. Bruyant, F. Carminati, S. Giani, M. Maire, A. McPherson, G. Patrick, and L. Urban, GEANT: Detector Description and Simulation Tool; Oct 1994.  CERN Program Library. CERN, Geneva, 1993.  https://cds.cern.ch/record/1082634.  Long Writeup W5013.
  * [37] ALICE Collaboration, S. Acharya et al., “ALICE luminosity determination for Pb$-$Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV”, arXiv:2204.10148 [nucl-ex].
  * [38] ALICE Collaboration, J. Adam et al., “Coherent $\rho$0 photoproduction in ultra-peripheral Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV”, JHEP 09 (2015) 095, arXiv:1503.09177 [nucl-ex].
  * [39] A. J. Baltz, Y. Gorbunov, S. R. Klein, and J. Nystrand, “Two-Photon Interactions with Nuclear Breakup in Relativistic Heavy Ion Collisions”, Phys. Rev. C 80 (2009) 044902, arXiv:0907.1214 [nucl-ex].
  * [40] S. Klein and J. Nystrand, “Exclusive vector meson production in relativistic heavy ion collisions”, Phys. Rev. C 60 (1999) 014903, arXiv:hep-ph/9902259.
  * [41] R. M. Egloff, et al., “Measurements of elastic $\rho$\- and $\phi$-meson photoproduction cross sections on protons from 30 to 180 gev”, Phys. Rev. Lett. 43 (Sep, 1979) 657–660. https://link.aps.org/doi/10.1103/PhysRevLett.43.657.
  * [42] J. A. Crittenden, “Exclusive production of neutral vector mesons at the electron - proton collider HERA”, arXiv:hep-ex/9704009.
  * [43] L. Frankfurt, V. Guzey, M. Strikman, and M. Zhalov, “Nuclear shadowing in photoproduction of $\rho$ mesons in ultraperipheral nucleus collisions at RHIC and the LHC”, Phys. Lett. B 752 (2016) 51–58, arXiv:1506.07150 [hep-ph].
  * [44] ALICE Collaboration, S. Acharya et al., “Coherent $J/\psi$ and $\psi^{\prime}$ photoproduction at midrapidity in ultra-peripheral Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}~{}=~{}5.02$ TeV”, Eur. Phys. J. C 81 (2021) 712, arXiv:2101.04577 [nucl-ex].
  * [45] Z. Citron et al., “Report from Working Group 5: Future physics opportunities for high-density QCD at the LHC with heavy-ion and proton beams”, CERN Yellow Rep. Monogr. 7 (2019) 1159–1410, arXiv:1812.06772 [hep-ph].
  * [46] P. Buncic, M. Krzewicki, and P. Vande Vyvre, “Technical Design Report for the Upgrade of the Online-Offline Computing System”, tech. rep., 2015.  https://cds.cern.ch/record/2011297.
  * [47] ALICE Collaboration, “Upgrade of the ALICE Time Projection Chamber”, tech. rep., 2013.  https://cds.cern.ch/record/1622286.

##  Appendix A The ALICE Collaboration

S. Acharya 127, D. Adamová 86, 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 97, D. Aleksandrov 141, B. Alessandro 57, H.M.
Alfanda 6, R. Alfaro Molina 68, B. Ali 16, A. Alici 26, N. Alizadehvandchali
115, A. Alkin 33, J. Alme 21, G. Alocco 53, T. Alt 65, A.R. Altamura 51, I.
Altsybeev 95, M.N. Anaam 6, C. Andrei 46, N. Andreou 114, A. Andronic 126, E.
Andronov 141, V. Anguelov 94, F. Antinori 55, P. Antonioli 52, N. Apadula 74,
L. Aphecetche 103, H. Appelshäuser 65, C. Arata 73, S. Arcelli 26, M. Aresti
23, R. Arnaldi 57, J.G.M.C.A. Arneiro 110, I.C. Arsene 20, M. Arslandok 138,
A. Augustinus 33, R. Averbeck 97, M.D. Azmi 16, H. Baba123, A. Badalà 54, J.
Bae 104, Y.W. Baek 41, X. Bai 119, R. Bailhache 65, Y. Bailung 49, R. Bala 91,
A. Balbino 30, A. Baldisseri 130, B. Balis 2, D. Banerjee 4, Z. Banoo 91, F.
Barile 32, L. Barioglio 95, M. Barlou78, B. Barman42, G.G. Barnaföldi 47, L.S.
Barnby 85, E. Barreau103, V. Barret 127, L. Barreto 110, C. Bartels 118, K.
Barth 33, E. Bartsch 65, N. Bastid 127, S. Basu 75, G. Batigne 103, D.
Battistini 95, B. Batyunya 142, D. Bauri48, J.L. Bazo Alba 101, I.G. Bearden
83, C. Beattie 138, P. Becht 97, D. Behera 49, I. Belikov 129, A.D.C. Bell
Hechavarria 126, F. Bellini 26, R. Bellwied 115, S. Belokurova 141, L.G.E.
Beltran 109, Y.A.V. Beltran 45, G. Bencedi 47, S. Beole 25, Y. Berdnikov 141,
A. Berdnikova 94, L. Bergmann 94, M.G. Besoiu 64, L. Betev 33, P.P. Bhaduri
135, A. Bhasin 91, M.A. Bhat 4, B. Bhattacharjee 42, L. Bianchi 25, N. Bianchi
50, J. Bielčík 36, J. Bielčíková 86, A.P. Bigot 129, A. Bilandzic 95, G. Biro
47, S. Biswas 4, N. Bize 103, J.T. Blair 108, D. Blau 141, M.B. Blidaru 97, N.
Bluhme39, C. Blume 65, G. Boca 22,56, F. Bock 87, T. Bodova 21, S. Boi 23, J.
Bok 17, L. Boldizsár 47, M. Bombara 38, P.M. Bond 33, G. Bonomi 134,56, H.
Borel 130, A. Borissov 141, A.G. Borquez Carcamo 94, H. Bossi 138, E. Botta
25, Y.E.M. Bouziani 65, L. Bratrud 65, P. Braun-Munzinger 97, M. Bregant 110,
M. Broz 36, G.E. Bruno 96,32, M.D. Buckland 24, D. Budnikov 141, H. Buesching
65, S. Bufalino 30, P. Buhler 102, N. Burmasov 141, Z. Buthelezi 69,122, A.
Bylinkin 21, S.A. Bysiak107, J.C. Cabanillas Noris 109, M. Cai 6, H. Caines
138, A. Caliva 29, E. Calvo Villar 101, J.M.M. Camacho 109, P. Camerini 24,
F.D.M. Canedo 110, M. Carabas 125, A.A. Carballo 33, F. Carnesecchi 33, R.
Caron 128, L.A.D. Carvalho 110, J. Castillo Castellanos 130, F. Catalano
33,25, C. Ceballos Sanchez 142, I. Chakaberia 74, P. Chakraborty 48, S.
Chandra 135, S. Chapeland 33, M. Chartier 118, S. Chattopadhyay 135, S.
Chattopadhyay 99, T.G. Chavez 45, T. Cheng 97,6, C. Cheshkov 128, B. Cheynis
128, V. Chibante Barroso 33, D.D. Chinellato 111, E.S. ChizzaliII,95, J. Cho
59, S. Cho 59, P. Chochula 33, D. Choudhury42, P. Christakoglou 84, C.H.
Christensen 83, P. Christiansen 75, T. Chujo 124, M. Ciacco 30, C. Cicalo 53,
M.R. Ciupek97, G. ClaiIII,52, F. Colamaria 51, J.S. Colburn100, D. Colella
96,32, M. Colocci 26, M. Concas IV,33, G. Conesa Balbastre 73, Z. Conesa del
Valle 131, G. Contin 24, J.G. Contreras 36, M.L. Coquet 130, P. Cortese
133,57, M.R. Cosentino 112, F. Costa 33, S. Costanza 22,56, C. Cot 131, J.
Crkovská 94, P. Crochet 127, R. Cruz-Torres 74, P. Cui 6, A. Dainese 55, M.C.
Danisch 94, A. Danu 64, P. Das 80, 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, R. Del Grande 95, L. Dello Stritto 33,29, W. Deng 6, P.
Dhankher 19, D. Di Bari 32, A. Di Mauro 33, B. Diab 130, R.A. Diaz 142,7, T.
Dietel 113, Y. Ding 6, J. Ditzel 65, R. Divià 33, D.U. Dixit 19, Ø.
Djuvsland21, U. Dmitrieva 141, A. Dobrin 64, B. Dönigus 65, J.M. Dubinski 136,
A. Dubla 97, S. Dudi 90, P. Dupieux 127, M. Durkac106, N. Dzalaiova13, T.M.
Eder 126, R.J. Ehlers 74, F. Eisenhut 65, R. Ejima92, D. Elia 51, B. Erazmus
103, F. Ercolessi 26, B. Espagnon 131, G. Eulisse 33, D. Evans 100, S.
Evdokimov 141, L. Fabbietti 95, M. Faggin 28, J. Faivre 73, F. Fan 6, W. Fan
74, A. Fantoni 50, M. Fasel 87, A. Feliciello 57, G. Feofilov 141, A.
Fernández Téllez 45, L. Ferrandi 110, M.B. Ferrer 33, A. Ferrero 130, C.
Ferrero 57, A. Ferretti 25, V.J.G. Feuillard 94, V. Filova 36, D. Finogeev
141, F.M. Fionda 53, E. Flatland33, F. Flor 115, A.N. Flores 108, S. Foertsch
69, I. Fokin 94, S. Fokin 141, E. Fragiacomo 58, E. Frajna 47, U. Fuchs 33, N.
Funicello 29, C. Furget 73, A. Furs 141, T. Fusayasu 98, J.J. Gaardhøje 83, M.
Gagliardi 25, A.M. Gago 101, T. Gahlaut48, C.D. Galvan 109, D.R. Gangadharan
115, P. Ganoti 78, C. Garabatos 97, A.T. Garcia 131, J.R.A. Garcia 45, E.
Garcia-Solis 9, C. Gargiulo 33, P. Gasik 97, A. Gautam 117, M.B. Gay Ducati
67, M. Germain 103, A. Ghimouz124, C. Ghosh135, M. Giacalone 52, G. Gioachin
30, P. Giubellino 97,57, P. Giubilato 28, A.M.C. Glaenzer 130, P. Glässel 94,
E. Glimos 121, D.J.Q. Goh76, V. Gonzalez 137, P. Gordeev 141, M. Gorgon 2, K.
Goswami 49, S. Gotovac34, V. Grabski 68, L.K. Graczykowski 136, E. Grecka 86,
A. Grelli 60, C. Grigoras 33, V. Grigoriev 141, S. Grigoryan 142,1, F. Grosa
33, J.F. Grosse-Oetringhaus 33, R. Grosso 97, D. Grund 36, N.A. Grunwald94,
G.G. Guardiano 111, R. Guernane 73, M. Guilbaud 103, K. Gulbrandsen 83, T.
Gündem 65, T. Gunji 123, W. Guo 6, A. Gupta 91, R. Gupta 91, R. Gupta 49, S.P.
Guzman 45, K. Gwizdziel 136, L. Gyulai 47, C. Hadjidakis 131, F.U. Haider 91,
S. Haidlova 36, M. Haldar4, H. Hamagaki 76, A. Hamdi 74, Y. Han 139, B.G.
Hanley 137, R. Hannigan 108, J. Hansen 75, J.W. Harris 138, A. Harton 9, M.V.
Hartung 65, H. Hassan 116, D. Hatzifotiadou 52, P. Hauer 43, L.B. Havener 138,
E. Hellbär 97, 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 95, A. Horzyk 2, Y. Hou 6, P. Hristov 33, C. Hughes 121, P.
Huhn65, L.M. Huhta 116, T.J. Humanic 88, A. Hutson 115, D. Hutter 39, M.C.
Hwang 19, R. Ilkaev141, H. Ilyas 14, M. Inaba 124, G.M. Innocenti 33, M.
Ippolitov 141, A. Isakov 84,86, T. Isidori 117, M.S. Islam 99, M. Ivanov13, M.
Ivanov 97, V. Ivanov 141, K.E. Iversen 75, M. Jablonski 2, B. Jacak 19,74, N.
Jacazio 26, P.M. Jacobs 74, S. Jadlovska106, J. Jadlovsky106, S. Jaelani 82,
C. Jahnke 110, M.J. Jakubowska 136, M.A. Janik 136, T. Janson71, S. Ji 17, S.
Jia 10, A.A.P. Jimenez 66, F. Jonas 74,87, D.M. Jones 118, J.M. Jowett 33,97,
J. Jung 65, M. Jung 65, A. Junique 33, A. Jusko 100, M.J. Kabus 33,136, J.
Kaewjai105, P. Kalinak 61, A.S. Kalteyer 97, A. Kalweit 33, D. Karatovic 89,
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 119, S. Khan 16, A. Khanzadeev 141, Y. Kharlov 141,
A. Khatun 117, A. Khuntia 36, Z. Khuranova 65, B. Kileng 35, B. Kim 104, C.
Kim 17, D.J. Kim 116, E.J. Kim 70, J. Kim 139, J. Kim 59, J. Kim 70, M. Kim
19, S. Kim 18, T. Kim 139, K. Kimura 92, 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 74, C.
Klein-Bösing 126, M. Kleiner 65, T. Klemenz 95, A. Kluge 33, C. Kobdaj 105, T.
Kollegger97, A. Kondratyev 142, N. Kondratyeva 141, J. Konig 65, S.A.
Konigstorfer 95, P.J. Konopka 33, G. Kornakov 136, M. Korwieser 95, S.D.
Koryciak 2, A. Kotliarov 86, N. Kovacic89, V. Kovalenko 141, M. Kowalski 107,
V. Kozhuharov 37, I. Králik 61, A. Kravčáková 38, L. Krcal 33,39, M. Krivda
100,61, F. Krizek 86, K. Krizkova Gajdosova 33, M. Kroesen 94, M. Krüger 65,
D.M. Krupova 36, E. Kryshen 141, V. Kučera 59, C. Kuhn 129, P.G. Kuijer 84, T.
Kumaoka124, D. Kumar135, L. Kumar 90, N. Kumar90, S. Kumar 32, S. Kundu 33, P.
Kurashvili 79, A. Kurepin 141, A.B. Kurepin 141, A. Kuryakin 141, S. Kushpil
86, V. Kuskov 141, M. Kutyla136, M.J. Kweon 59, Y. Kwon 139, S.L. La Pointe
39, P. La Rocca 27, A. Lakrathok105, M. Lamanna 33, A.R. Landou 73, R. Langoy
120, P. Larionov 33, E. Laudi 33, L. Lautner 33,95, R. Lavicka 102, R. Lea
134,56, H. Lee 104, I. Legrand 46, G. Legras 126, J. Lehrbach 39, T.M. Lelek2,
R.C. Lemmon 85, I. León Monzón 109, M.M. Lesch 95, E.D. Lesser 19, P. Lévai
47, X. Li10, B.E. Liang-gilman 19, J. Lien 120, R. Lietava 100, I. Likmeta
115, B. Lim 25, S.H. Lim 17, V. Lindenstruth 39, A. Lindner46, C. Lippmann 97,
D.H. Liu 6, J. Liu 118, G.S.S. Liveraro 111, I.M. Lofnes 21, C. Loizides 87,
S. Lokos 107, J. Lomker 60, P. Loncar 34, X. Lopez 127, E. López Torres 7, P.
Lu 97,119, F.V. Lugo 68, 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 91, Q.W. Malik20, S.K. Malik 91, L. Malinina
I,VII,142, D. Mallick 131,80, N. Mallick 49, G. Mandaglio 31,54, S.K. Mandal
79, 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 97, C. Markert 108, P. Martinengo
33, M.I. Martínez 45, G. Martínez García 103, M.P.P. Martins 110, S.
Masciocchi 97, M. Masera 25, A. Masoni 53, L. Massacrier 131, O. Massen 60, A.
Mastroserio 132,51, O. Matonoha 75, S. Mattiazzo 28, A. Matyja 107, C. Mayer
107, A.L. Mazuecos 33, F. Mazzaschi 25, M. Mazzilli 33, J.E. Mdhluli 122, Y.
Melikyan 44, A. Menchaca-Rocha 68, J.E.M. Mendez 66, E. Meninno 102, A.S.
Menon 115, M. Meres 13, Y. Miake124, L. Micheletti 33, D.L. Mihaylov 95, K.
Mikhaylov 142,141, D. Miśkowiec 97, A. Modak 4, B. Mohanty80, M. Mohisin Khan
V,16, M.A. Molander 44, S. Monira 136, C. Mordasini 116, D.A. Moreira De Godoy
126, I. Morozov 141, A. Morsch 33, T. Mrnjavac 33, V. Muccifora 50, S. Muhuri
135, J.D. Mulligan 74, A. Mulliri23, M.G. Munhoz 110, R.H. Munzer 65, H.
Murakami 123, S. Murray 113, L. Musa 33, J. Musinsky 61, J.W. Myrcha 136, B.
Naik 122, A.I. Nambrath 19, B.K. Nandi 48, R. Nania 52, E. Nappi 51, A.F.
Nassirpour 18, A. Nath 94, C. Nattrass 121, M.N. Naydenov 37, A. Neagu20, A.
Negru125, E. Nekrasova141, L. Nellen 66, R. Nepeivoda 75, S. Nese 20, G.
Neskovic 39, N. Nicassio 51, B.S. Nielsen 83, E.G. Nielsen 83, S. Nikolaev
141, S. Nikulin 141, V. Nikulin 141, F. Noferini 52, S. Noh 12, P. Nomokonov
142, J. Norman 118, N. Novitzky 87, P. Nowakowski 136, A. Nyanin 141, J.
Nystrand 21, S. Oh 18, A. Ohlson 75, V.A. Okorokov 141, J. Oleniacz 136, A.
Onnerstad 116, C. Oppedisano 57, A. Ortiz Velasquez 66, J. Otwinowski 107, M.
Oya92, K. Oyama 76, Y. Pachmayer 94, S. Padhan 48, D. Pagano 134,56, G. Paić
66, A. Palasciano 51, S. Panebianco 130, H. Park 124, H. Park 104, J. Park 59,
J.E. Parkkila 33, Y. Patley 48, B. Paul 23, H. Pei 6, T. Peitzmann 60, X. Peng
11, M. Pennisi 25, S. Perciballi 25, D. Peresunko 141, G.M. Perez 7, Y.
Pestov141, V. Petrov 141, M. Petrovici 46, R.P. Pezzi 103,67, S. Piano 58, M.
Pikna 13, P. Pillot 103, O. Pinazza 52,33, L. Pinsky115, C. Pinto 95, S.
Pisano 50, M. Płoskoń 74, M. Planinic89, F. Pliquett65, M.G. Poghosyan 87, B.
Polichtchouk 141, S. Politano 30, N. Poljak 89, 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. Pugelova106, S. Qiu 84, L.
Quaglia 25, S. Ragoni 15, A. Rai 138, A. Rakotozafindrabe 130, L. Ramello
133,57, F. Rami 129, S.A.R. Ramirez 45, T.A. Rancien73, M. Rasa 27, S.S.
Räsänen 44, R. Rath 52, M.P. Rauch 21, I. Ravasenga 33, K.F. Read 87,121, C.
Reckziegel 112, A.R. Redelbach 39, K. Redlich VI,79, C.A. Reetz 97, A.
Rehman21, F. Reidt 33, H.A. Reme-Ness 35, Z. Rescakova38, K. Reygers 94, A.
Riabov 141, V. Riabov 141, R. Ricci 29, M. Richter 20, A.A. Riedel 95, W.
Riegler 33, A.G. Riffero 25, 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 26, 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 84, A. Rustamov 81, E. Ryabinkin 141, Y.
Ryabov 141, A. Rybicki 107, H. Rytkonen 116, J. Ryu 17, W. Rzesa 136, O.A.M.
Saarimaki 44, S. Sadhu 32, S. Sadovsky 141, J. Saetre 21, K. Šafařík 36, P.
Saha42, S.K. Saha 4, S. Saha 80, 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 124,
M.P. Salvan 97, S. Sambyal 91, D. Samitz 102, I. Sanna 33,95, T.B.
Saramela110, P. Sarma 42, V. Sarritzu 23, V.M. Sarti 95, M.H.P. Sas 33, S.
Sawan80, E. Scapparone 52, J. Schambach 87, H.S. Scheid 65, C. Schiaua 46, R.
Schicker 94, F. Schlepper 94, A. Schmah97, C. Schmidt 97, H.R. Schmidt93, M.O.
Schmidt 33, M. Schmidt93, N.V. Schmidt 87, A.R. Schmier 121, R. Schotter 129,
A. Schröter 39, J. Schukraft 33, K. Schweda 97, G. Scioli 26, E. Scomparin 57,
J.E. Seger 15, Y. Sekiguchi123, D. Sekihata 123, M. Selina 84, I. Selyuzhenkov
97, S. Senyukov 129, J.J. Seo 94, D. Serebryakov 141, L. Serkin 66, L.
Šerkšnytė 95, A. Sevcenco 64, T.J. Shaba 69, A. Shabetai 103, R. Shahoyan33,
A. Shangaraev 141, B. Sharma 91, D. Sharma 48, H. Sharma 55, M. Sharma91, S.
Sharma 76, S. Sharma 91, U. Sharma 91, A. Shatat 131, O. Sheibani115, K.
Shigaki 92, M. Shimomura77, J. Shin12, S. Shirinkin 141, Q. Shou 40, Y.
Sibiriak 141, S. Siddhanta 53, T. Siemiarczuk 79, T.F. Silva 110, D. Silvermyr
75, T. Simantathammakul105, R. Simeonov 37, B. Singh91, B. Singh 95, K. Singh
49, R. Singh 80, R. Singh 91, R. Singh 49, S. Singh 16, V.K. Singh 135, V.
Singhal 135, T. Sinha 99, B. Sitar 13, M. Sitta 133,57, T.B. Skaali20, G.
Skorodumovs 94, M. Slupecki 44, N. Smirnov 138, R.J.M. Snellings 60, E.H.
Solheim 20, J. Song 17, C. Sonnabend 33,97, J.M. Sonneveld 84, F. Soramel 28,
A.B. Soto-hernandez 88, R. Spijkers 84, I. Sputowska 107, J. Staa 75, J.
Stachel 94, I. Stan 64, P.J. Steffanic 121, S.F. Stiefelmaier 94, D. Stocco
103, I. Storehaug 20, P. Stratmann 126, S. Strazzi 26, A. Sturniolo 31,54,
C.P. Stylianidis84, A.A.P. Suaide 110, C. Suire 131, M. Sukhanov 141, M.
Suljic 33, R. Sultanov 141, V. Sumberia 91, S. Sumowidagdo 82, S. Swain62, I.
Szarka 13, M. Szymkowski 136, S.F. Taghavi 95, G. Taillepied 97, J. Takahashi
111, G.J. Tambave 80, S. Tang 6, Z. Tang 119, J.D. Tapia Takaki 117, N.
Tapus125, 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 115, S.
Thakur 4, D. Thomas 108, A. Tikhonov 141, N. Tiltmann 126, A.R. Timmins 115,
M. Tkacik106, T. Tkacik 106, A. Toia 65, R. Tokumoto92, K. Tomohiro92, N.
Topilskaya 141, M. Toppi 50, T. Tork 131, P.V. Torres66, V.V. Torres 103, 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 116, T.P. Trzcinski
136, A. Tumkin 141, R. Turrisi 55, T.S. Tveter 20, K. Ullaland 21, B. Ulukutlu
95, A. Uras 128, M. Urioni 134, G.L. Usai 23, M. Vala38, N. Valle 22, L.V.R.
van Doremalen60, M. van Leeuwen 84, C.A. van Veen 94, R.J.G. van Weelden 84,
P. Vande Vyvre 33, D. Varga 47, Z. Varga 47, M. Vasileiou 78, A. Vasiliev 141,
O. Vázquez Doce 50, O. Vazquez Rueda 115, V. Vechernin 141, E. Vercellin 25,
S. Vergara Limón45, R. Verma48, L. Vermunt 97, R. Vértesi 47, M. Verweij 60,
L. Vickovic34, Z. Vilakazi122, O. Villalobos Baillie 100, A. Villani 24, A.
Vinogradov 141, T. Virgili 29, M.M.O. Virta 116, V. Vislavicius75, A.
Vodopyanov 142, B. Volkel 33, M.A. Völkl 94, S.A. Voloshin 137, G. Volpe 32,
B. von Haller 33, I. Vorobyev 33, 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, S.L. Weyhmiller 138, J. Wiechula 65, J.
Wikne 20, G. Wilk 79, J. Wilkinson 97, G.A. Willems 126, B. Windelband 94, M.
Winn 130, J.R. Wright 108, W. Wu40, Y. Wu 119, R. Xu 6, A. Yadav 43, A.K.
Yadav 135, Y. Yamaguchi 92, S. Yang21, S. Yano 92, E.R. Yeats19, Z. Yin 6,
I.-K. Yoo 17, J.H. Yoon 59, H. Yu12, S. Yuan21, A. Yuncu 94, V. Zaccolo 24, C.
Zampolli 33, F. Zanone 94, 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. Zhang119, Z. Zhang 6, M. Zhao 10, V. Zherebchevskii
141, Y. Zhi10, C. Zhong40, D. Zhou 6, Y. Zhou 83, J. Zhu 55,6, 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 Laboratoire de Physique Subatomique et de Cosmologie, Université Grenoble-
Alpes, CNRS-IN2P3, Grenoble, France
74 Lawrence Berkeley National Laboratory, Berkeley, California, United States
75 Lund University Department of Physics, Division of Particle Physics, Lund,
Sweden
76 Nagasaki Institute of Applied Science, Nagasaki, Japan
77 Nara Women’s University (NWU), Nara, Japan
78 National and Kapodistrian University of Athens, School of Science,
Department of Physics , Athens, Greece
79 National Centre for Nuclear Research, Warsaw, Poland
80 National Institute of Science Education and Research, Homi Bhabha National
Institute, Jatni, India
81 National Nuclear Research Center, Baku, Azerbaijan
82 National Research and Innovation Agency - BRIN, Jakarta, Indonesia
83 Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark
84 Nikhef, National institute for subatomic physics, Amsterdam, Netherlands
85 Nuclear Physics Group, STFC Daresbury Laboratory, Daresbury, United Kingdom
86 Nuclear Physics Institute of the Czech Academy of Sciences, Husinec-Řež,
Czech Republic
87 Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States
88 Ohio State University, Columbus, Ohio, United States
89 Physics department, Faculty of science, University of Zagreb, Zagreb,
Croatia
90 Physics Department, Panjab University, Chandigarh, India
91 Physics Department, University of Jammu, Jammu, India
92 Physics Program and International Institute for Sustainability with Knotted
Chiral Meta Matter (SKCM2), Hiroshima University, Hiroshima, Japan
93 Physikalisches Institut, Eberhard-Karls-Universität Tübingen, Tübingen,
Germany
94 Physikalisches Institut, Ruprecht-Karls-Universität Heidelberg, Heidelberg,
Germany
95 Physik Department, Technische Universität München, Munich, Germany
96 Politecnico di Bari and Sezione INFN, Bari, Italy
97 Research Division and ExtreMe Matter Institute EMMI, GSI Helmholtzzentrum
für Schwerionenforschung GmbH, Darmstadt, Germany
98 Saga University, Saga, Japan
99 Saha Institute of Nuclear Physics, Homi Bhabha National Institute, Kolkata,
India
100 School of Physics and Astronomy, University of Birmingham, Birmingham,
United Kingdom
101 Sección Física, Departamento de Ciencias, Pontificia Universidad Católica
del Perú, Lima, Peru
102 Stefan Meyer Institut für Subatomare Physik (SMI), Vienna, Austria
103 SUBATECH, IMT Atlantique, Nantes Université, CNRS-IN2P3, Nantes, France
104 Sungkyunkwan University, Suwon City, Republic of Korea
105 Suranaree University of Technology, Nakhon Ratchasima, Thailand
106 Technical University of Košice, Košice, Slovak Republic
107 The Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy of
Sciences, Cracow, Poland
108 The University of Texas at Austin, Austin, Texas, United States
109 Universidad Autónoma de Sinaloa, Culiacán, Mexico
110 Universidade de São Paulo (USP), São Paulo, Brazil
111 Universidade Estadual de Campinas (UNICAMP), Campinas, Brazil
112 Universidade Federal do ABC, Santo Andre, Brazil
113 University of Cape Town, Cape Town, South Africa
114 University of Derby, Derby, United Kingdom
115 University of Houston, Houston, Texas, United States
116 University of Jyväskylä, Jyväskylä, Finland
117 University of Kansas, Lawrence, Kansas, United States
118 University of Liverpool, Liverpool, United Kingdom
119 University of Science and Technology of China, Hefei, China
120 University of South-Eastern Norway, Kongsberg, Norway
121 University of Tennessee, Knoxville, Tennessee, United States
122 University of the Witwatersrand, Johannesburg, South Africa
123 University of Tokyo, Tokyo, Japan
124 University of Tsukuba, Tsukuba, Japan
125 University Politehnica of Bucharest, Bucharest, Romania
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.