EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH (CERN)

 CERN-EP-2019-077 LHCb-PAPER-2019-015 August 29, 2019

Measurement of $CP$-violating and mixing-induced observables in
$B_{s}^{0}\rightarrow\phi\gamma$ decays

LHCb collaboration†††Authors are listed at the end of this Letter.

A time-dependent analysis of the $B_{s}^{0}\rightarrow\phi\gamma$ decay rate
is performed to determine the $CP$-violating observables $S_{\phi\gamma}$ and
$C_{\phi\gamma}$, and the mixing-induced observable
$\mathcal{A}^{\Delta}_{\phi\gamma}$. The measurement is based on a sample of
$pp$ collision data recorded with the LHCb detector, corresponding to an
integrated luminosity of 3 fb-1 at center-of-mass energies of 7 and 8 TeV. The
measured values are

$\displaystyle S_{\phi\gamma}$ $\displaystyle=0.43\pm 0.30\pm 0.11,$
$\displaystyle C_{\phi\gamma}$ $\displaystyle=0.11\pm 0.29\pm 0.11,$
$\displaystyle\mathcal{A}^{\Delta}_{\phi\gamma}$
$\displaystyle=-0.67\,^{+0.37}_{-0.41}\pm 0.17,$

where the first uncertainty is statistical and the second systematic. This is
the first measurement of the observables $S$ and $C$ in radiative $B_{s}^{0}$
decays. The results are consistent with the Standard Model predictions.

Published in Phys. Rev. Lett. 123 (2019) 081802

© 2024 CERN for the benefit of the LHCb collaboration. CC-BY-4.0 licence.

In the Standard Model (SM) of particle physics, the $b\rightarrow s\gamma$
transition proceeds via loop Feynman diagrams. The small size of the SM
amplitude makes such process sensitive to the contribution of possible new
particles. The emitted photons are produced predominantly with left-handed
helicity in the SM due to parity violation in the weak interaction, with a
small relative right-handed component proportional to the ratio of $s$\- to
$b$-quark masses. In many extensions of the SM, the right-handed component can
be enhanced, leading to observable effects in mixing-induced $C\\!P$
asymmetries and time-dependent decay rates of radiative ${B}^{0}$ and
${B}^{0}_{s}$ decays [1, 2, 3]. Current measurements sensitive to right-handed
contributions [4, 5, 6, 7, 8, 9] are in agreement with SM predictions [10].

The rate $\mathcal{P}(t)$ at which ${B}^{0}_{s}$ or ${\kern
1.79993pt\overline{\kern-1.79993ptB}{}}{}^{0}_{s}$ mesons decay to a common
final state that contains a photon, such as $\phi\gamma$ (where $\phi$ refers
to $\phi(1020)$), depends on the decay time $t$ as [3]

$\begin{split}\mathcal{P}(t)\propto
e^{-\Gamma_{s}t}\bigl{\\{}&\cosh\left(\Delta\Gamma_{s}t/2\right)-\mathcal{A}^{\Delta}\sinh\left(\Delta\Gamma_{s}t/2\right)\\\
&+\zeta\,C\cos\left(\Delta m_{s}t\right)-\zeta\,S\sin\left(\Delta
m_{s}t\right)\bigr{\\}},\end{split}$ (1)

where $\Delta\Gamma_{s}$ and $\Delta m_{s}$ are the width and mass differences
between the ${B}^{0}_{s}$ mass eigenstates, defined positively, $\Gamma_{s}$
is the mean decay width between such eigenstates, and $\zeta$ takes the value
of $+1$ ($-1$) for an initial ${B}^{0}_{s}$ (${\kern
1.79993pt\overline{\kern-1.79993ptB}{}}{}^{0}_{s}$) state. The coefficients
$\mathcal{A}^{\Delta}$ and $S$ are sensitive to the photon helicity amplitudes
and weak phases, while $C$ is related to $C\\!P$ violation in the decay. The
SM predictions for the three coefficients in the
$B_{s}^{0}\rightarrow\phi\gamma$ decay are close to zero [3]. The LHCb
collaboration has previously measured
$\mathcal{A}^{\Delta}_{\phi\gamma}=-0.98\,^{+0.46}_{-0.52}\,{}^{+0.23}_{-0.20}$
[9] from a time-dependent flavour-untagged analysis, which is compatible with
the SM within two standard deviations.

This Letter reports the first measurement of the $C\\!P$-violating observables
$S$ and $C$ from a radiative ${B}^{0}_{s}$ decay, determined from the time-
dependent rate of $B_{s}^{0}\rightarrow\phi\gamma$ decays in which the $\phi$
meson decays to a ${{K}^{+}}{{K}^{-}}$ pair. An update of the
$\mathcal{A}^{\Delta}_{\phi\gamma}$ coefficient measurement is also provided.
Results are based on data collected with the LHCb detector in $pp$ collisions
at center-of-mass energies of 7 and 8 TeV during the years 2011 and 2012,
respectively, corresponding to an integrated luminosity of
3$\text{\,fb}^{-1}$. Compared to Ref. [9], the current analysis benefits from
a 20% higher event selection efficiency, a reoptimized calorimeter
reconstruction and a new photon identification algorithm. Flavor-tagging
algorithms are applied to determine the initial flavor of the ${B}^{0}_{s}$ or
${\kern 1.79993pt\overline{\kern-1.79993ptB}{}}{}^{0}_{s}$ meson, which is
essential to measure the $S$ and $C$ observables, whereas flavor-untagged
decays still contribute to the measurement of $\mathcal{A}^{\Delta}$. The
background is subtracted from a fit to the mass distribution of the
${B}^{0}_{s}$ candidates. A sample of untagged
${{B}^{0}}\rightarrow{{K}^{*0}}\gamma$ decays (where ${K}^{*0}$ refers to
${{K}^{*0}}(892)$), reconstructed in the flavor-specific
${{K}^{*0}}\rightarrow{{K}^{+}}{{\pi}^{-}}$ final state, is used to control
the decay-time-dependent efficiency, since its lifetime is well measured.
Throughout this Letter, the inclusion of charge-conjugated processes is
implied.

The LHCb detector is a single-arm forward spectrometer covering the
pseudorapidity range $2<\eta<5$, described in detail in Refs. [11, 12]. It
includes a high-precision tracking system consisting of a silicon-strip vertex
detector surrounding the $pp$ interaction region, a large-area silicon-strip
detector located upstream of a dipole magnet with a bending power of about
$4{\mathrm{\,Tm}}$, and three stations of silicon-strip detectors and straw
drift tubes placed downstream of the magnet. Different types of charged
hadrons are distinguished using information from two ring-imaging Cherenkov
detectors. Photons, electrons and hadrons are identified by a calorimeter
system consisting of scintillating-pad and preshower detectors, an
electromagnetic and a hadronic calorimeter.

The online event selection is performed by a trigger system, which consists of
a hardware stage, based on information from the calorimeter and muon systems,
followed by a software stage, which applies a full event reconstruction. Two
trigger selections are defined, with different photon and track momentum
thresholds. Samples of simulated events, produced with the software described
in Refs. [13, *Sjostrand:2006za, 15, 16, 17, 18, *Agostinelli:2002hh, 20], are
used to characterize signal and background contributions. The signal sample is
generated with the three coefficients $\mathcal{A}^{\Delta}_{\phi\gamma}$,
$C_{\phi\gamma}$ and $S_{\phi\gamma}$ set to zero.

Candidate $B_{s}^{0}\rightarrow\phi\gamma$ decays are reconstructed from a
photon candidate and two oppositely charged particles identified as kaons. The
selection is designed to maximize the significance $S/\sqrt{S+B}$ of the
signal yield. Photons are reconstructed from energy deposits in the
electromagnetic calorimeter and required to have a momentum transverse to the
beam axis, $p_{\mathrm{T}}$, larger than $3.0$ or
$4.2\text{\,Ge\kern-1.00006ptV\\!/}c$, depending on the trigger selection.
Background due to photons from ${\pi}^{0}$ decays is rejected by a dedicated
algorithm [21]. The kaon candidates are required to have
$p>1.0\text{\,Ge\kern-1.00006ptV\\!/}c$ and
$p_{\mathrm{T}}>0.3\text{\,Ge\kern-1.00006ptV\\!/}c$, where $p$ is the total
momentum, and at least one of them must fulfill
$p>10\text{\,Ge\kern-1.00006ptV\\!/}c$ and $p_{\mathrm{T}}>1.2$ or
$1.8\text{\,Ge\kern-1.00006ptV\\!/}c$, depending on the trigger selection.
Kaon candidates are required to be inconsistent with originating from a
primary $pp$ interaction vertex, and must form a common vertex of good
quality. The ${K}^{+}$ ${K}^{-}$ system must have an invariant mass within
$15\text{\,Me\kern-1.00006ptV\\!/}c^{2}$ of the known $\phi$ mass [22]. The
${B}^{0}_{s}$ candidate must be consistent with originating from only one $pp$
interaction vertex, and only candidates with decay times between 0.3 and 10 ps
are retained. In addition, the cosine of the helicity angle ($\theta_{H}$),
defined as the angle between the momenta of the positively charged kaon and
that of the ${B}^{0}_{s}$ meson in the rest frame of the $\phi$ meson, is
required to be less than $0.8$ in absolute value. This requirement helps to
suppress the ${\pi}^{0}$ and combinatorial backgrounds, which are expected to
be distributed as $\cos^{2}\theta_{H}$ and a uniform distribution,
respectively, as opposed to the $\sin^{2}\theta_{H}$ distribution expected for
the signal. The ${{B}^{0}}\rightarrow{{K}^{*0}}\gamma$ decay, with
${{K}^{*0}}\rightarrow{{K}^{+}}{{\pi}^{-}}$, is selected with almost identical
requirements. A pion is required instead of a kaon, and the invariant mass of
the ${K}^{+}$ ${\pi}^{-}$ system must be within
$100\text{\,Me\kern-1.00006ptV\\!/}c^{2}$ of the known ${{K}^{*0}}$ mass [22].

The signal yields are $5110\pm 90$ for $B_{s}^{0}\rightarrow\phi\gamma$ decays
and $33\,860\pm 250$ for $B^{0}\rightarrow{{K}^{*0}}\gamma$ decays, where the
uncertainties are statistical only. They are obtained from separate extended
unbinned maximum-likelihood fits to the ${{B}^{0}_{s}}\rightarrow\phi\gamma$
and ${{B}^{0}}\rightarrow{{K}^{*0}}\gamma$ reconstructed mass distributions in
the ranges 5000–6000$\text{\,Me\kern-1.00006ptV\\!/}c^{2}$ and
4600–6000$\text{\,Me\kern-1.00006ptV\\!/}c^{2}$, respectively. The mass fits
are shown in Fig. 1. The results are used to assign weights to the candidates
in the data samples in order to subtract the backgrounds [23]. The signal line
shapes are described by modified Crystal Ball functions [24], consisting of a
Gaussian core with power-law tails on both sides of the peak. The mean and
width of the Gaussian core are obtained from data, while the tail parameters
are determined from simulation. Three background categories are considered:
combinatorial, peaking, and partially reconstructed. The combinatorial
background, modeled by a linear function, is produced by the wrong association
of a random photon with two hadrons mostly coming from real $\phi$ and
${{K}^{*0}}$ resonances. The peaking backgrounds originate from other
$b$-hadron decays with a reconstructed mass falling under the signal peak, due
to the misidentification of one or several final-state particles. All possible
combinations of misidentified hadrons, or the misidentification of a $\pi^{0}$
meson as a photon, are considered for the signal and control decay channels.
For the $B_{s}^{0}\rightarrow\phi\gamma$ decay channel, the relevant
contributions are ${{B}^{0}_{s}}\rightarrow\phi\pi^{0}$ and ${{\mathchar
28931\relax}^{0}_{b}}\rightarrow(p{{K}^{-}})\gamma$, where $p{{K}^{-}}$ comes
from $\Lambda(1520)$ and further baryon resonances. For the
$B^{0}\rightarrow{{K}^{*0}}\gamma$ decay channel, the
${{B}^{0}}\rightarrow{{K}^{*0}}\pi^{0}$ and ${{\mathchar
28931\relax}^{0}_{b}}\rightarrow(p{{K}^{-}})\gamma$ decays are taken into
account. Each peaking background is modeled with a Crystal Ball function. The
shape parameters are determined from simulation, except for the width of the
Gaussian core, which is multiplied by a factor to account for the difference
in resolution between data and simulation. The yield ratios of peaking
backgrounds to signal are calculated using simulation samples and taking the
branching ratios from experimental measurements [9, 6]. They are determined to
be below 2% in all cases. Partially reconstructed backgrounds originate from
other $b$-hadron decays in which one or several final-state particles are not
reconstructed. This contribution is negligible in
$B_{s}^{0}\rightarrow\phi\gamma$ decays, while for the
$B^{0}\rightarrow{{K}^{*0}}\gamma$ mode the dominant contributions are: decays
of the type $B\rightarrow K\pi\pi\gamma$ with a missing pion, decays of the
type $B\rightarrow K\pi\pi^{0}X$ (mainly from $B^{+}\rightarrow{{\kern
1.99997pt\overline{\kern-1.99997ptD}{}}{}^{0}}\rho^{+}$ decays) with one or
several missing hadrons, and
${{B}^{0}}\rightarrow{{K}^{*0}}\eta(\gamma\gamma)$ decays with a missing
photon. They are described by an ARGUS function [25] convolved with a Gaussian
function to account for the detector resolution, with the shape parameters
determined from simulation.

Figure 1: Fits to the mass distributions of the (left)
$B_{s}^{0}\rightarrow\phi\gamma$ and (right)
$B^{0}\rightarrow{{K}^{*0}}\gamma$ candidates.

Flavor-tagging algorithms are applied to identify the initial flavor of the
${{B}^{0}_{s}}$ meson. They provide a tag decision $q$, which takes the value
$+1$ if the signal was originally a ${B}^{0}_{s}$ meson, $-1$ if it was a
${\kern 1.79993pt\overline{\kern-1.79993ptB}{}}{}^{0}_{s}$ meson, and zero if
no decision is given. The algorithms also provide an estimate $\eta$ of the
probability for the tag decision to be incorrect (mistag probability). Two
classes of flavor-tagging algorithms are used: same-side (SS) [26] and
opposite-side (OS) taggers [27]. The SS tagger determines the flavor of the
signal candidate by identifying the charge of the kaon produced together with
the ${B}^{0}_{s}$ meson in the fragmentation process, and is based on a neural
network algorithm [26]. The OS taggers rely on the pair production of $b$
hadrons in $pp$ collisions and examine the decay products of the other $b$
hadron in the event. The information used includes the charge of the leptons
produced in semileptonic decays, the charge of kaons produced in $b\rightarrow
c\rightarrow s$ transitions, and the charge of the particles originating from
the decay vertex [27].

The mistag probability estimate $\eta$ is calibrated using a linear function
to obtain a corrected mistag probability $\omega$ for the signal sample. This
is performed using mainly samples of
$B^{+}\rightarrow{{J\mskip-3.0mu/\mskip-2.0mu\psi\mskip 2.0mu}}{{K}^{+}}$ and
$B^{0}\rightarrow{{J\mskip-3.0mu/\mskip-2.0mu\psi\mskip 2.0mu}}{{K}^{*0}}$
decays for the OS tagger and ${{B}^{0}_{s}}\rightarrow D_{s}^{-}\pi^{+}$ and
$B^{*}_{s2}(5840)^{0}\rightarrow B^{+}{{K}^{-}}$ decays for the SS tagger. The
uncertainties of the calibration parameters include a systematic uncertainty
that takes into account possible differences of these parameters between the
decays used for calibration and other $B$-decay modes. The validity of these
calibrations for $B_{s}^{0}\rightarrow\phi\gamma$ decays is checked using both
simulation and data. Finally, the outputs of the algorithms are combined into
a single decision and mistag probability. The effective tagging efficiency,
$\epsilon_{\text{eff}}=\left(4.99\pm 0.14\right)$%, is the product of the
probability to obtain a decision $\epsilon_{\text{tag}}=\left(74.5\pm
0.8\right)$% and the square of the effective dilution
$D=1-2\omega=\left(25.9\pm 0.3\right)$%.

The $C\\!P$-violating and mixing-induced observables are determined from a
weighted unbinned maximum-likelihood fit [28] to the decay-time distributions,
performed simultaneously on the $B_{s}^{0}\rightarrow\phi\gamma$ and
$B^{0}\rightarrow{{K}^{*0}}\gamma$ samples. The signal probability density
function (PDF) of the $B_{s}^{0}\rightarrow\phi\gamma$ decay-time distribution
is defined as the decay rate $\mathcal{P}(t)$ in Eq. 1, convolved with a
resolution function and multiplied by a decay-time-dependent efficiency
$\epsilon(t)$. For the $B^{0}\rightarrow{{K}^{*0}}\gamma$ decay, the time-
dependent decay rate is described as a single exponential function. The
physics parameters are constrained to the averages from Ref. [29]:
$\tau_{{{B}^{0}}}=1.520\pm 0.004\text{\,ps}$, $\Gamma_{s}=0.6629\pm
0.0018\text{\,ps}^{-1}$, $\Delta\Gamma_{s}=0.088\pm 0.006\text{\,ps}^{-1}$ and
$\Delta m_{s}=17.757\pm 0.021\text{\,ps}^{-1}$. The correlation of $-0.11$
between the $\Gamma_{s}$ and $\Delta\Gamma_{s}$ parameters is taken into
account.

The decay-time resolution is modeled by the sum of two Gaussian functions,
with a common mean and independent widths. The widths are given by the per-
candidate decay-time uncertainties, multiplied by constant scaling factors
determined from simulation to account for an observed underestimation of the
uncertainties. Additional control samples are used to determine the decay-time
resolution differences between simulation and data, which are accounted for in
the analysis as a source of systematic uncertainty. These samples include
$\phi$ mesons coming from $pp$ interaction vertices and
${{B}^{0}}\rightarrow{{J\mskip-3.0mu/\mskip-2.0mu\psi\mskip 2.0mu}}{{K}^{*0}}$
decays, with ${{J\mskip-3.0mu/\mskip-2.0mu\psi\mskip
2.0mu}}\rightarrow{\mu^{+}}{\mu^{-}}$. In the latter case, in order to emulate
the signal behavior, the decay is reconstructed with the two muons not
contributing to the vertex fitting. The resolution depends strongly on the
decay time, with an average of $70\text{\,fs}$. The decay-time resolution is
dominated by the photon momentum resolution, therefore being similar for
$B_{s}^{0}\rightarrow\phi\gamma$ and $B^{0}\rightarrow{{K}^{*0}}\gamma$
decays.

The efficiency as a function of the decay time $t$ is parameterized as

$\epsilon(t)\propto\dfrac{t^{a/t}}{\cosh(b\,t)}\,,$ (2)

where the parameters $a$ and $b$ describe mainly the shape of the function at
low and high decay times, respectively. One hundred bins of variable size are
defined to characterize this function. The efficiency parameters are
determined in the simultaneous fit to the data, mainly driven from
$B^{0}\rightarrow{{K}^{*0}}\gamma$ candidates, while the differences between
the two decays are obtained from simulation and fixed in the data fit. In
simulation, the decay-time-dependent efficiencies of the two decay modes are
compatible within uncertainties.

Pseudoexperiments are used to validate the overall fit procedure. In each
pseudoexperiment, samples of $B_{s}^{0}\rightarrow\phi\gamma$ and
$B^{0}\rightarrow{{K}^{*0}}\gamma$ signal decays are generated based on the
data mass fit and the expected yields. Background candidates are included
taking random events from data or simulation. The mass and the decay-time fits
are then performed, following the nominal procedure. The procedure is repeated
for several values of the coefficients. No biases are found on the average
fitted values, in any scenario. Statistical uncertainties are found to be
underestimated by about 15% for $S_{\phi\gamma}$ and $C_{\phi\gamma}$, and 5%
for $\mathcal{A}^{\Delta}_{\phi\gamma}$, due to the background-subtraction
weights [28]. The uncertainties are corrected for in the results below.

The decay-time distributions and the corresponding fit projections are shown
in Fig. 2. The fitted values are $S_{\phi\gamma}=0.43\pm 0.30$,
$C_{\phi\gamma}=0.11\pm 0.29$ and
$\mathcal{A}^{\Delta}_{\phi\gamma}=-0.67\,^{+0.37}_{-0.41}$, with a small
correlation of $-0.04$ between each pair of observables. The statistical
uncertainty includes the uncertainty from the physics parameters taken from
external measurements. For $S_{\phi\gamma}$ and $C_{\phi\gamma}$, the
systematic uncertainty is dominated by the effects of possible differences
between data and simulation in the decay-time resolution parameters (0.08),
and the uncertainty on the parameters used to calibrate the same-side tagging
algorithms (0.04). For $\mathcal{A}^{\Delta}_{\phi\gamma}$, the dominant
source of systematic uncertainties is related to the determination of the
decay-time-dependent efficiency function. In particular, the contribution of
the partially reconstructed background of $B^{0}\rightarrow{{K}^{*0}}\gamma$
decays, coming from the correlation between reconstructed mass and time (0.11)
and the mass-shape modeling (0.08), and the limited size of the simulation
sample used to determine the efficiency differences between
$B_{s}^{0}\rightarrow\phi\gamma$ and $B^{0}\rightarrow{{K}^{*0}}\gamma$ decays
(0.08). The total systematic uncertainties are $0.11$ for $S_{\phi\gamma}$ and
$C_{\phi\gamma}$, and $0.17$ for $\mathcal{A}^{\Delta}_{\phi\gamma}$.

Figure 2: Decay-time fit projections. The top row corresponds to the tagged
(left) $B_{s}^{0}\rightarrow\phi\gamma$ and (right) ${{\kern
1.61993pt\overline{\kern-1.61993ptB}{}}{}^{0}_{s}}\rightarrow\phi\gamma$
candidates, while the bottom plots show the (left) untagged
$B_{s}^{0}\rightarrow\phi\gamma$ and (right)
$B^{0}\rightarrow{{K}^{*0}}\gamma$ candidates. The line is the result of the
fit described in the text, including statistical uncertainties.

In summary, the $C\\!P$-violating and mixing-induced observables
$S_{\phi\gamma}$, $C_{\phi\gamma}$ and $\mathcal{A}^{\Delta}_{\phi\gamma}$ are
measured from a time-dependent analysis of $B_{s}^{0}\rightarrow\phi\gamma$
decays, using a data sample corresponding to an integrated luminosity of
3$\text{\,fb}^{-1}$ collected with the LHCb experiment during the 2011 and
2012 data-taking periods. More than $5000$ $B_{s}^{0}\rightarrow\phi\gamma$
decays are reconstructed. A sample of $B^{0}\rightarrow{{K}^{*0}}\gamma$
decays, which is six times larger, is used for the calibration of the time-
dependent efficiency. From a simultaneous unbinned fit to the
$B_{s}^{0}\rightarrow\phi\gamma$ and $B^{0}\rightarrow{{K}^{*0}}\gamma$ data
samples, the values

$\displaystyle S_{\phi\gamma}$ $\displaystyle=0.43\pm 0.30\pm 0.11,$
$\displaystyle C_{\phi\gamma}$ $\displaystyle=0.11\pm 0.29\pm 0.11,$
$\displaystyle\mathcal{A}^{\Delta}_{\phi\gamma}$
$\displaystyle=-0.67\,^{+0.37}_{-0.41}\pm 0.17$

are measured, where the first uncertainty is statistical and the second
systematic. The results are compatible with the SM expectation [3] within
$1.3$, $0.3$ and $1.7$ standard deviations, respectively.

## Acknowledgements

We express our gratitude to our colleagues in the CERN accelerator departments
for the excellent performance of the LHC. We thank the technical and
administrative staff at the LHCb institutes. We acknowledge support from CERN
and from the national agencies: CAPES, CNPq, FAPERJ and FINEP (Brazil); MOST
and NSFC (China); CNRS/IN2P3 (France); BMBF, DFG and MPG (Germany); INFN
(Italy); NWO (Netherlands); MNiSW and NCN (Poland); MEN/IFA (Romania); MSHE
(Russia); MinECo (Spain); SNSF and SER (Switzerland); NASU (Ukraine); STFC
(United Kingdom); DOE NP and NSF (USA). We acknowledge the computing resources
that are provided by CERN, IN2P3 (France), KIT and DESY (Germany), INFN
(Italy), SURF (Netherlands), PIC (Spain), GridPP (United Kingdom), RRCKI and
Yandex LLC (Russia), CSCS (Switzerland), IFIN-HH (Romania), CBPF (Brazil), PL-
GRID (Poland) and OSC (USA). We are indebted to the communities behind the
multiple open-source software packages on which we depend. Individual groups
or members have received support from AvH Foundation (Germany); EPLANET, Marie
Skłodowska-Curie Actions and ERC (European Union); ANR, Labex P2IO and OCEVU,
and Région Auvergne-Rhône-Alpes (France); Key Research Program of Frontier
Sciences of CAS, CAS PIFI, and the Thousand Talents Program (China); RFBR, RSF
and Yandex LLC (Russia); GVA, XuntaGal and GENCAT (Spain); the Royal Society
and the Leverhulme Trust (United Kingdom).

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LHCb collaboration

R. Aaij29, C. Abellán Beteta46, B. Adeva43, M. Adinolfi50, C.A. Aidala77, Z.
Ajaltouni7, S. Akar61, P. Albicocco20, J. Albrecht12, F. Alessio44, M.
Alexander55, A. Alfonso Albero42, G. Alkhazov35, P. Alvarez Cartelle57, A.A.
Alves Jr43, S. Amato2, Y. Amhis9, L. An19, L. Anderlini19, G. Andreassi45, M.
Andreotti18, J.E. Andrews62, F. Archilli20, J. Arnau Romeu8, A. Artamonov41,
M. Artuso63, K. Arzymatov39, E. Aslanides8, M. Atzeni46, B. Audurier24, S.
Bachmann14, J.J. Back52, S. Baker57, V. Balagura9,b, W. Baldini18,44, A.
Baranov39, R.J. Barlow58, S. Barsuk9, W. Barter57, M. Bartolini21, F.
Baryshnikov73, V. Batozskaya33, B. Batsukh63, A. Battig12, V. Battista45, A.
Bay45, F. Bedeschi26, I. Bediaga1, A. Beiter63, L.J. Bel29, V. Belavin39, S.
Belin24, N. Beliy4, V. Bellee45, N. Belloli22,i, K. Belous41, I. Belyaev36, G.
Bencivenni20, E. Ben-Haim10, S. Benson29, S. Beranek11, A. Berezhnoy37, R.
Bernet46, D. Berninghoff14, E. Bertholet10, A. Bertolin25, C. Betancourt46, F.
Betti17,e, M.O. Bettler51, Ia. Bezshyiko46, S. Bhasin50, J. Bhom31, M.S.
Bieker12, S. Bifani49, P. Billoir10, A. Birnkraut12, A. Bizzeti19,u, M.
Bjørn59, M.P. Blago44, T. Blake52, F. Blanc45, S. Blusk63, D. Bobulska55, V.
Bocci28, O. Boente Garcia43, T. Boettcher60, A. Bondar40,x, N. Bondar35, S.
Borghi58,44, M. Borisyak39, M. Borsato14, M. Boubdir11, T.J.V. Bowcock56, C.
Bozzi18,44, S. Braun14, A. Brea Rodriguez43, M. Brodski44, J. Brodzicka31, A.
Brossa Gonzalo52, D. Brundu24,44, E. Buchanan50, A. Buonaura46, C. Burr58, A.
Bursche24, J.S. Butter29, J. Buytaert44, W. Byczynski44, S. Cadeddu24, H.
Cai67, R. Calabrese18,g, S. Cali20, R. Calladine49, M. Calvi22,i, M. Calvo
Gomez42,m, A. Camboni42,m, P. Campana20, D.H. Campora Perez44, L.
Capriotti17,e, A. Carbone17,e, G. Carboni27, R. Cardinale21, A. Cardini24, P.
Carniti22,i, K. Carvalho Akiba2, A. Casais Vidal43, G. Casse56, M. Cattaneo44,
G. Cavallero21, R. Cenci26,p, M.G. Chapman50, M. Charles10,44, Ph.
Charpentier44, G. Chatzikonstantinidis49, M. Chefdeville6, V. Chekalina39, C.
Chen3, S. Chen24, S.-G. Chitic44, V. Chobanova43, M. Chrzaszcz44, A.
Chubykin35, P. Ciambrone20, X. Cid Vidal43, G. Ciezarek44, F. Cindolo17,
P.E.L. Clarke54, M. Clemencic44, H.V. Cliff51, J. Closier44, V. Coco44, J.A.B.
Coelho9, J. Cogan8, E. Cogneras7, L. Cojocariu34, P. Collins44, T. Colombo44,
A. Comerma-Montells14, A. Contu24, G. Coombs44, S. Coquereau42, G. Corti44,
C.M. Costa Sobral52, B. Couturier44, G.A. Cowan54, D.C. Craik60, A.
Crocombe52, M. Cruz Torres1, R. Currie54, C.L. Da Silva78, E. Dall’Occo29, J.
Dalseno43,v, C. D’Ambrosio44, A. Danilina36, P. d’Argent14, A. Davis58, O. De
Aguiar Francisco44, K. De Bruyn44, S. De Capua58, M. De Cian45, J.M. De
Miranda1, L. De Paula2, M. De Serio16,d, P. De Simone20, J.A. de Vries29, C.T.
Dean55, W. Dean77, D. Decamp6, L. Del Buono10, B. Delaney51, H.-P.
Dembinski13, M. Demmer12, A. Dendek32, D. Derkach74, O. Deschamps7, F. Desse9,
F. Dettori24, B. Dey68, A. Di Canto44, P. Di Nezza20, S. Didenko73, H.
Dijkstra44, F. Dordei24, M. Dorigo26,y, A.C. dos Reis1, A. Dosil Suárez43, L.
Douglas55, A. Dovbnya47, K. Dreimanis56, L. Dufour44, G. Dujany10, P.
Durante44, J.M. Durham78, D. Dutta58, R. Dzhelyadin41,†, M. Dziewiecki14, A.
Dziurda31, A. Dzyuba35, S. Easo53, U. Egede57, V. Egorychev36, S.
Eidelman40,x, S. Eisenhardt54, U. Eitschberger12, R. Ekelhof12, S. Ek-In45, L.
Eklund55, S. Ely63, A. Ene34, S. Escher11, S. Esen29, T. Evans61, A.
Falabella17, C. Färber44, N. Farley49, S. Farry56, D. Fazzini9, M. Féo44, P.
Fernandez Declara44, A. Fernandez Prieto43, F. Ferrari17,e, L. Ferreira
Lopes45, F. Ferreira Rodrigues2, S. Ferreres Sole29, M. Ferro-Luzzi44, S.
Filippov38, R.A. Fini16, M. Fiorini18,g, M. Firlej32, C. Fitzpatrick44, T.
Fiutowski32, F. Fleuret9,b, M. Fontana44, F. Fontanelli21,h, R. Forty44, V.
Franco Lima56, M. Franco Sevilla62, M. Frank44, C. Frei44, J. Fu23,q, W.
Funk44, E. Gabriel54, A. Gallas Torreira43, D. Galli17,e, S. Gallorini25, S.
Gambetta54, Y. Gan3, M. Gandelman2, P. Gandini23, Y. Gao3, L.M. Garcia
Martin76, J. García Pardiñas46, B. Garcia Plana43, J. Garra Tico51, L.
Garrido42, D. Gascon42, C. Gaspar44, G. Gazzoni7, D. Gerick14, E. Gersabeck58,
M. Gersabeck58, T. Gershon52, D. Gerstel8, Ph. Ghez6, V. Gibson51, O.G.
Girard45, P. Gironella Gironell42, L. Giubega34, K. Gizdov54, V.V. Gligorov10,
C. Göbel65, D. Golubkov36, A. Golutvin57,73, A. Gomes1,a, I.V. Gorelov37, C.
Gotti22,i, E. Govorkova29, J.P. Grabowski14, R. Graciani Diaz42, L.A. Granado
Cardoso44, E. Graugés42, E. Graverini45, G. Graziani19, A. Grecu34, R.
Greim29, P. Griffith24, L. Grillo58, L. Gruber44, B.R. Gruberg Cazon59, C.
Gu3, E. Gushchin38, A. Guth11, Yu. Guz41,44, T. Gys44, T. Hadavizadeh59, C.
Hadjivasiliou7, G. Haefeli45, C. Haen44, S.C. Haines51, B. Hamilton62, Q.
Han68, X. Han14, T.H. Hancock59, S. Hansmann-Menzemer14, N. Harnew59, T.
Harrison56, C. Hasse44, M. Hatch44, J. He4, M. Hecker57, K. Heinicke12, A.
Heister12, K. Hennessy56, L. Henry76, M. Heß70, J. Heuel11, A. Hicheur64, R.
Hidalgo Charman58, D. Hill59, M. Hilton58, P.H. Hopchev45, J. Hu14, W. Hu68,
W. Huang4, Z.C. Huard61, W. Hulsbergen29, T. Humair57, M. Hushchyn74, D.
Hutchcroft56, D. Hynds29, P. Ibis12, M. Idzik32, P. Ilten49, A. Inglessi35, A.
Inyakin41, K. Ivshin35, R. Jacobsson44, S. Jakobsen44, J. Jalocha59, E.
Jans29, B.K. Jashal76, A. Jawahery62, F. Jiang3, M. John59, D. Johnson44, C.R.
Jones51, C. Joram44, B. Jost44, N. Jurik59, S. Kandybei47, M. Karacson44, J.M.
Kariuki50, S. Karodia55, N. Kazeev74, M. Kecke14, F. Keizer51, M. Kelsey63, M.
Kenzie51, T. Ketel30, B. Khanji44, A. Kharisova75, C. Khurewathanakul45, K.E.
Kim63, T. Kirn11, V.S. Kirsebom45, S. Klaver20, K. Klimaszewski33, S.
Koliiev48, M. Kolpin14, A. Kondybayeva73, A. Konoplyannikov36, R. Kopecna14,
P. Koppenburg29, I. Kostiuk29,48, O. Kot48, S. Kotriakhova35, M. Kozeiha7, L.
Kravchuk38, M. Kreps52, F. Kress57, S. Kretzschmar11, P. Krokovny40,x, W.
Krupa32, W. Krzemien33, W. Kucewicz31,l, M. Kucharczyk31, V. Kudryavtsev40,x,
G.J. Kunde78, A.K. Kuonen45, T. Kvaratskheliya36, D. Lacarrere44, G.
Lafferty58, A. Lai24, D. Lancierini46, G. Lanfranchi20, C. Langenbruch11, T.
Latham52, C. Lazzeroni49, R. Le Gac8, R. Lefèvre7, A. Leflat37, F. Lemaitre44,
O. Leroy8, T. Lesiak31, B. Leverington14, H. Li66, P.-R. Li4,ab, X. Li78, Y.
Li5, Z. Li63, X. Liang63, T. Likhomanenko72, R. Lindner44, F. Lionetto46, V.
Lisovskyi9, G. Liu66, X. Liu3, D. Loh52, A. Loi24, J. Lomba Castro43, I.
Longstaff55, J.H. Lopes2, G. Loustau46, G.H. Lovell51, D. Lucchesi25,o, M.
Lucio Martinez43, Y. Luo3, A. Lupato25, E. Luppi18,g, O. Lupton52, A.
Lusiani26, X. Lyu4, F. Machefert9, F. Maciuc34, V. Macko45, P. Mackowiak12, S.
Maddrell-Mander50, O. Maev35,44, K. Maguire58, D. Maisuzenko35, M.W.
Majewski32, S. Malde59, B. Malecki44, A. Malinin72, T. Maltsev40,x, H.
Malygina14, G. Manca24,f, G. Mancinelli8, D. Marangotto23,q, J. Maratas7,w,
J.F. Marchand6, U. Marconi17, C. Marin Benito9, M. Marinangeli45, P. Marino45,
J. Marks14, P.J. Marshall56, G. Martellotti28, L. Martinazzoli44, M.
Martinelli44,22,i, D. Martinez Santos43, F. Martinez Vidal76, A. Massafferri1,
M. Materok11, R. Matev44, A. Mathad46, Z. Mathe44, V. Matiunin36, C.
Matteuzzi22, K.R. Mattioli77, A. Mauri46, E. Maurice9,b, B. Maurin45, M.
McCann57,44, A. McNab58, R. McNulty15, J.V. Mead56, B. Meadows61, C. Meaux8,
N. Meinert70, D. Melnychuk33, M. Merk29, A. Merli23,q, E. Michielin25, D.A.
Milanes69, E. Millard52, M.-N. Minard6, O. Mineev36, L. Minzoni18,g, D.S.
Mitzel14, A. Mödden12, A. Mogini10, R.D. Moise57, T. Mombächer12, I.A.
Monroy69, S. Monteil7, M. Morandin25, G. Morello20, M.J. Morello26,t, J.
Moron32, A.B. Morris8, R. Mountain63, H. Mu3, F. Muheim54, M. Mukherjee68, M.
Mulder29, D. Müller44, J. Müller12, K. Müller46, V. Müller12, C.H. Murphy59,
D. Murray58, P. Naik50, T. Nakada45, R. Nandakumar53, A. Nandi59, T. Nanut45,
I. Nasteva2, M. Needham54, N. Neri23,q, S. Neubert14, N. Neufeld44, R.
Newcombe57, T.D. Nguyen45, C. Nguyen-Mau45,n, S. Nieswand11, R. Niet12, N.
Nikitin37, N.S. Nolte44, A. Oblakowska-Mucha32, V. Obraztsov41, S. Ogilvy55,
D.P. O’Hanlon17, R. Oldeman24,f, C.J.G. Onderwater71, J. D. Osborn77, A.
Ossowska31, J.M. Otalora Goicochea2, T. Ovsiannikova36, P. Owen46, A.
Oyanguren76, P.R. Pais45, T. Pajero26,t, A. Palano16, M. Palutan20, G.
Panshin75, A. Papanestis53, M. Pappagallo54, L.L. Pappalardo18,g, W. Parker62,
C. Parkes58,44, G. Passaleva19,44, A. Pastore16, M. Patel57, C.
Patrignani17,e, A. Pearce44, A. Pellegrino29, G. Penso28, M. Pepe Altarelli44,
S. Perazzini17, D. Pereima36, P. Perret7, L. Pescatore45, K. Petridis50, A.
Petrolini21,h, A. Petrov72, S. Petrucci54, M. Petruzzo23,q, B. Pietrzyk6, G.
Pietrzyk45, M. Pikies31, M. Pili59, D. Pinci28, J. Pinzino44, F. Pisani44, A.
Piucci14, V. Placinta34, S. Playfer54, J. Plews49, M. Plo Casasus43, F.
Polci10, M. Poli Lener20, M. Poliakova63, A. Poluektov8, N. Polukhina73,c, I.
Polyakov63, E. Polycarpo2, G.J. Pomery50, S. Ponce44, A. Popov41, D. Popov49,
S. Poslavskii41, E. Price50, C. Prouve43, V. Pugatch48, A. Puig Navarro46, H.
Pullen59, G. Punzi26,p, W. Qian4, J. Qin4, R. Quagliani10, B. Quintana7, N.V.
Raab15, B. Rachwal32, J.H. Rademacker50, M. Rama26, M. Ramos Pernas43, M.S.
Rangel2, F. Ratnikov39,74, G. Raven30, M. Ravonel Salzgeber44, M. Reboud6, F.
Redi45, S. Reichert12, F. Reiss10, C. Remon Alepuz76, Z. Ren3, V. Renaudin59,
S. Ricciardi53, S. Richards50, K. Rinnert56, P. Robbe9, A. Robert10, A.B.
Rodrigues45, E. Rodrigues61, J.A. Rodriguez Lopez69, M. Roehrken44, S.
Roiser44, A. Rollings59, V. Romanovskiy41, A. Romero Vidal43, J.D. Roth77, M.
Rotondo20, M.S. Rudolph63, T. Ruf44, J. Ruiz Vidal76, J.J. Saborido Silva43,
N. Sagidova35, B. Saitta24,f, V. Salustino Guimaraes65, C. Sanchez Gras29, C.
Sanchez Mayordomo76, B. Sanmartin Sedes43, R. Santacesaria28, C. Santamarina
Rios43, M. Santimaria20,44, E. Santovetti27,j, G. Sarpis58, A. Sarti20,k, C.
Satriano28,s, A. Satta27, M. Saur4, D. Savrina36,37, S. Schael11, M.
Schellenberg12, M. Schiller55, H. Schindler44, M. Schmelling13, T.
Schmelzer12, B. Schmidt44, O. Schneider45, A. Schopper44, H.F. Schreiner61, M.
Schubiger29, S. Schulte45, M.H. Schune9, R. Schwemmer44, B. Sciascia20, A.
Sciubba28,k, A. Semennikov36, E.S. Sepulveda10, A. Sergi49,44, N. Serra46, J.
Serrano8, L. Sestini25, A. Seuthe12, P. Seyfert44, M. Shapkin41, T. Shears56,
L. Shekhtman40,x, V. Shevchenko72, E. Shmanin73, B.G. Siddi18, R. Silva
Coutinho46, L. Silva de Oliveira2, G. Simi25,o, S. Simone16,d, I. Skiba18, N.
Skidmore14, T. Skwarnicki63, M.W. Slater49, J.G. Smeaton51, E. Smith11, I.T.
Smith54, M. Smith57, M. Soares17, l. Soares Lavra1, M.D. Sokoloff61, F.J.P.
Soler55, B. Souza De Paula2, B. Spaan12, E. Spadaro Norella23,q, P.
Spradlin55, F. Stagni44, M. Stahl14, S. Stahl44, P. Stefko45, S. Stefkova57,
O. Steinkamp46, S. Stemmle14, O. Stenyakin41, M. Stepanova35, H. Stevens12, A.
Stocchi9, S. Stone63, S. Stracka26, M.E. Stramaglia45, M. Straticiuc34, U.
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1Centro Brasileiro de Pesquisas Físicas (CBPF), Rio de Janeiro, Brazil
2Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil
3Center for High Energy Physics, Tsinghua University, Beijing, China
4University of Chinese Academy of Sciences, Beijing, China
5Institute Of High Energy Physics (ihep), Beijing, China
6Univ. Grenoble Alpes, Univ. Savoie Mont Blanc, CNRS, IN2P3-LAPP, Annecy,
France
7Université Clermont Auvergne, CNRS/IN2P3, LPC, Clermont-Ferrand, France
8Aix Marseille Univ, CNRS/IN2P3, CPPM, Marseille, France
9LAL, Univ. Paris-Sud, CNRS/IN2P3, Université Paris-Saclay, Orsay, France
10LPNHE, Sorbonne Université, Paris Diderot Sorbonne Paris Cité, CNRS/IN2P3,
Paris, France
11I. Physikalisches Institut, RWTH Aachen University, Aachen, Germany
12Fakultät Physik, Technische Universität Dortmund, Dortmund, Germany
13Max-Planck-Institut für Kernphysik (MPIK), Heidelberg, Germany
14Physikalisches Institut, Ruprecht-Karls-Universität Heidelberg, Heidelberg,
Germany
15School of Physics, University College Dublin, Dublin, Ireland
16INFN Sezione di Bari, Bari, Italy
17INFN Sezione di Bologna, Bologna, Italy
18INFN Sezione di Ferrara, Ferrara, Italy
19INFN Sezione di Firenze, Firenze, Italy
20INFN Laboratori Nazionali di Frascati, Frascati, Italy
21INFN Sezione di Genova, Genova, Italy
22INFN Sezione di Milano-Bicocca, Milano, Italy
23INFN Sezione di Milano, Milano, Italy
24INFN Sezione di Cagliari, Monserrato, Italy
25INFN Sezione di Padova, Padova, Italy
26INFN Sezione di Pisa, Pisa, Italy
27INFN Sezione di Roma Tor Vergata, Roma, Italy
28INFN Sezione di Roma La Sapienza, Roma, Italy
29Nikhef National Institute for Subatomic Physics, Amsterdam, Netherlands
30Nikhef National Institute for Subatomic Physics and VU University Amsterdam,
Amsterdam, Netherlands
31Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of
Sciences, Kraków, Poland
32AGH - University of Science and Technology, Faculty of Physics and Applied
Computer Science, Kraków, Poland
33National Center for Nuclear Research (NCBJ), Warsaw, Poland
34Horia Hulubei National Institute of Physics and Nuclear Engineering,
Bucharest-Magurele, Romania
35Petersburg Nuclear Physics Institute NRC Kurchatov Institute (PNPI NRC KI),
Gatchina, Russia
36Institute of Theoretical and Experimental Physics NRC Kurchatov Institute
(ITEP NRC KI), Moscow, Russia, Moscow, Russia
37Institute of Nuclear Physics, Moscow State University (SINP MSU), Moscow,
Russia
38Institute for Nuclear Research of the Russian Academy of Sciences (INR RAS),
Moscow, Russia
39Yandex School of Data Analysis, Moscow, Russia
40Budker Institute of Nuclear Physics (SB RAS), Novosibirsk, Russia
41Institute for High Energy Physics NRC Kurchatov Institute (IHEP NRC KI),
Protvino, Russia, Protvino, Russia
42ICCUB, Universitat de Barcelona, Barcelona, Spain
43Instituto Galego de Física de Altas Enerxías (IGFAE), Universidade de
Santiago de Compostela, Santiago de Compostela, Spain
44European Organization for Nuclear Research (CERN), Geneva, Switzerland
45Institute of Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL),
Lausanne, Switzerland
46Physik-Institut, Universität Zürich, Zürich, Switzerland
47NSC Kharkiv Institute of Physics and Technology (NSC KIPT), Kharkiv, Ukraine
48Institute for Nuclear Research of the National Academy of Sciences (KINR),
Kyiv, Ukraine
49University of Birmingham, Birmingham, United Kingdom
50H.H. Wills Physics Laboratory, University of Bristol, Bristol, United
Kingdom
51Cavendish Laboratory, University of Cambridge, Cambridge, United Kingdom
52Department of Physics, University of Warwick, Coventry, United Kingdom
53STFC Rutherford Appleton Laboratory, Didcot, United Kingdom
54School of Physics and Astronomy, University of Edinburgh, Edinburgh, United
Kingdom
55School of Physics and Astronomy, University of Glasgow, Glasgow, United
Kingdom
56Oliver Lodge Laboratory, University of Liverpool, Liverpool, United Kingdom
57Imperial College London, London, United Kingdom
58School of Physics and Astronomy, University of Manchester, Manchester,
United Kingdom
59Department of Physics, University of Oxford, Oxford, United Kingdom
60Massachusetts Institute of Technology, Cambridge, MA, United States
61University of Cincinnati, Cincinnati, OH, United States
62University of Maryland, College Park, MD, United States
63Syracuse University, Syracuse, NY, United States
64Laboratory of Mathematical and Subatomic Physics , Constantine, Algeria,
associated to 2
65Pontifícia Universidade Católica do Rio de Janeiro (PUC-Rio), Rio de
Janeiro, Brazil, associated to 2
66South China Normal University, Guangzhou, China, associated to 3
67School of Physics and Technology, Wuhan University, Wuhan, China, associated
to 3
68Institute of Particle Physics, Central China Normal University, Wuhan,
Hubei, China, associated to 3
69Departamento de Fisica , Universidad Nacional de Colombia, Bogota, Colombia,
associated to 10
70Institut für Physik, Universität Rostock, Rostock, Germany, associated to 14
71Van Swinderen Institute, University of Groningen, Groningen, Netherlands,
associated to 29
72National Research Centre Kurchatov Institute, Moscow, Russia, associated to
36
73National University of Science and Technology “MISIS”, Moscow, Russia,
associated to 36
74National Research University Higher School of Economics, Moscow, Russia,
associated to 39
75National Research Tomsk Polytechnic University, Tomsk, Russia, associated to
36
76Instituto de Fisica Corpuscular, Centro Mixto Universidad de Valencia -
CSIC, Valencia, Spain, associated to 42
77University of Michigan, Ann Arbor, United States, associated to 63
78Los Alamos National Laboratory (LANL), Los Alamos, United States, associated
to 63

aUniversidade Federal do Triângulo Mineiro (UFTM), Uberaba-MG, Brazil
bLaboratoire Leprince-Ringuet, Palaiseau, France
cP.N. Lebedev Physical Institute, Russian Academy of Science (LPI RAS),
Moscow, Russia
dUniversità di Bari, Bari, Italy
eUniversità di Bologna, Bologna, Italy
fUniversità di Cagliari, Cagliari, Italy
gUniversità di Ferrara, Ferrara, Italy
hUniversità di Genova, Genova, Italy
iUniversità di Milano Bicocca, Milano, Italy
jUniversità di Roma Tor Vergata, Roma, Italy
kUniversità di Roma La Sapienza, Roma, Italy
lAGH - University of Science and Technology, Faculty of Computer Science,
Electronics and Telecommunications, Kraków, Poland
mLIFAELS, La Salle, Universitat Ramon Llull, Barcelona, Spain
nHanoi University of Science, Hanoi, Vietnam
oUniversità di Padova, Padova, Italy
pUniversità di Pisa, Pisa, Italy
qUniversità degli Studi di Milano, Milano, Italy
rUniversità di Urbino, Urbino, Italy
sUniversità della Basilicata, Potenza, Italy
tScuola Normale Superiore, Pisa, Italy
uUniversità di Modena e Reggio Emilia, Modena, Italy
vH.H. Wills Physics Laboratory, University of Bristol, Bristol, United Kingdom
wMSU - Iligan Institute of Technology (MSU-IIT), Iligan, Philippines
xNovosibirsk State University, Novosibirsk, Russia
ySezione INFN di Trieste, Trieste, Italy
zSchool of Physics and Information Technology, Shaanxi Normal University
(SNNU), Xi’an, China
aaPhysics and Micro Electronic College, Hunan University, Changsha City, China
abLanzhou University, Lanzhou, China
†Deceased