Search for weakly decaying $b$-flavored pentaquarks

CERN-EP-2017-329 LHCb-PAPER-2017-043 January 31, 2018

A search for weakly decaying

b-flavored pentaquarks

The LHCb collaboration†

Abstract

Investigations of the existence of pentaquark states containing a single b (anti)quark decaying weakly into four specific final states J/ψ K+π−p, J/ψ K−π−p, J/ψ K−π+p, and J/ψ φ(1020)p are reported. The data sample corresponds to an integrated lu-minosity of 3.0 fb−1 in 7 and 8 TeV pp collisions acquired with the LHCb detector. Signals are not observed and upper limits are set on the product of the production cross section times branching fraction with respect to that of the Λ0_b.

Submitted to Physical Review D

c

CERN on behalf of the LHCb collaboration, licence CC-BY-4.0.

†_{Authors are listed at the end of this paper.}

1

Introduction

The observation of charmonium pentaquark states with quark content ccuud, by the LHCb [1] collaboration in Λ0_b → J/ψ K−_{p decays, raises many questions including: What}

is the internal structure of these pentaquarks? Do other pentaquark states exist? Are they molecular or tightly bound? In this analysis, we search for pentaquarks that contain a single b (anti)quark, that decay via the weak interaction. The Skyrme model [2] has been used to predict that the heavier the constituent quarks, the more tightly bound the pen-taquark state [3–6]. This motivates our search for penpen-taquarks containing a b (anti)quark. No existing searches for weakly decaying pentaquarks containing a b (anti)quark have been published.

Consider the possible pentaquark states bduud, buudd, bduud and bsuud. We label these states as P_B+0_p, P − Λ0_bπ−, P + Λ0_bπ+ and P + B0

sp, respectively, where the subscript indicates the final states the pentaquark would predominantly decay into if it had sufficient mass to decay strongly into those states. While there are many possible decay modes of these states, we focus on modes containing a J/ψ meson in the final state because these can-didates generally have relatively large efficiencies and reduced backgrounds in the LHCb experiment. The Feynman diagrams for the decay of the P_B+0_p and P

+ B0

sp states are shown in Fig. 1. The corresponding diagrams for the decay of P_Λ−0

bπ−

and P_Λ+0

bπ+

are similar to that shown in Fig. 1(a), with the decay of the state being driven by the b → ccs transition. We reconstruct the φ(1020) meson1 in the K+K− decay mode. We note that the P_B+0_p pentaquark might have some decays inhibited by Bose statistics if its structure is based on two identical ud diquarks, i.e. b(ud)(ud). Although the P_B+0

sp state is expected to be produced at a smaller rate on the grounds that B_s0 production in the LHCb experiment acceptance is only about 13% of the rate of the sum of B+ _{and B}0 _{production [7], it}

would not have two identical diquarks, and hence none of its decays would suffer from spin-statistics suppression.

Table 1 lists all of the pentaquarks we search for along with their respective weak

+

d

u

b

u

d

d

c

u

u

d

}

}

p

}

c

s

ψ

J/

K

s

u

b

u

d

s

c

u

u

d

}

}

p

}

c

s

ψ

J/

φ

{

_{

P

P

u

u

}

π

Figure 1: Leading-order diagrams for pentaquark decay modes into (a) J/ψ K+π−p or (b) J/ψ φp final states.

Table 1: Quark content of the b-flavored pentaquarks and their weak decay modes explored here. We consider only the quark decay process b → ccs. The lower and upper bounds of the mass region searched are also given. (In this paper we use natural units where ~ = c = 1.)

Mode Quark content Decay mode Search window I bduud P_B+0_p → J/ψ K+π−p 4668–6220 MeV II buudd P_Λ−0 bπ− → J/ψ K−_π−_{p 4668–5760 MeV} III bduud P_Λ+0 bπ+ → J/ψ K−_π+_{p 4668–5760 MeV} IV bsuud P_B+0 sp → J/ψ φp 5055–6305 MeV decay modes.2 _{It is possible for these pentaquarks (P}

B) to decay either strongly or

weakly depending on their masses. The threshold mass for strong decay for P_B+0_p would be m(B0_{) + m(p), for P}− Λ0 bπ− m(Λ0 b) + m(π −_{), for P}+ Λ0 bπ+ m(Λ0 b) + m(π+) and for P + B0 sp m(B 0 s) +

m(p). Therefore, we define our signal search windows to be below these thresholds. Note that a fifth state, the bsuud pentaquark (P+

B0

sp

) could also decay into J/ψ φp, and thus is implicitly included in our searches. Should a signal be detected for mode IV, we would need to examine noncharmonium modes to distinguish between the possibilities.

2

Detector description and data samples

The LHCb detector [8,9] is a single-arm forward spectrometer covering the pseudorapidity range 2 < η < 5, designed for the study of particles containing b or c quarks. The detec-tor includes a high-precision tracking system consisting of a silicon-strip vertex detecdetec-tor surrounding the pp interaction region, a large-area silicon-strip detector located upstream of a dipole magnet with a bending power of about 4 Tm, and three stations of silicon-strip detectors and straw drift tubes placed downstream of the magnet. The tracking system provides a measurement of momentum, p, of charged particles with a relative uncertainty that varies from 0.5% at low momentum to 1.0% at 200 GeV. The minimum distance of a track to a primary pp interaction vertex (PV), the impact parameter (IP), is measured with a resolution of (15 + 29/pT) µm, where pT is the component of the momentum transverse

to the beam, in GeV. Different types of charged hadrons are distinguished using informa-tion from two ring-imaging Cherenkov detectors (RICH). Photons, electrons and hadrons are identified by a calorimeter system consisting of scintillating-pad and preshower detec-tors, an electromagnetic calorimeter and a hadronic calorimeter. Muons are identified by a system composed of alternating layers of iron and multiwire proportional chambers.

The online event selection is performed by a trigger, 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. The subsequent software trigger is composed of

2_{Unless explicitly stated, mention of a particular mode implies the use of the charge-conjugated mode}

two stages, the first of which performs a partial reconstruction and requires either a pair of well-reconstructed, oppositely charged muons having an invariant mass above 2.7 GeV, or a single well-reconstructed muon with high pT and large IP. The second stage of the

software trigger applies a full event reconstruction and, for this analysis, requires two opposite-sign muons to form a good-quality vertex that is well separated from all of the PVs, and to have an invariant mass within ±120 MeV of the known J/ψ mass [10]. The data sample corresponds to 1.0 fb−1 of integrated luminosity collected with the LHCb detector in 7 TeV pp collisions and 2.0 fb−1 in 8 TeV collisions.

Simulated events are generated in the LHCb acceptance using Pythia [11], with a special LHCb parameter tune [12]. Pentaquark candidate (PB) decays are generated

uni-formly in phase space. Decays of other hadronic particles are described by EvtGen [13], in which final-state radiation is generated using Photos [14]. The interaction of the gen-erated particles with the detector, and its response, are implemented using the Geant4 toolkit [15] as described in Ref. [16]. The lifetime of the simulated pentaquarks is set to 1.5 ps, consistent with that of most weakly decaying b hadrons [10].

3

Event selection and b-hadron reconstruction

A pentaquark candidate is reconstructed by combining a J/ψ → µ+_µ− _{candidate with a}

proton, kaon, and pion (or kaon for mode IV). Our analysis strategy consists of a preselec-tion based on loose particle identificapreselec-tion (PID) and the kinematics of the decay, followed by a more sophisticated multivariate selection (MVA) classifier based on a Boosted Deci-sion Tree (BDT) [17], which uses multiple input variables, accounts for the correlations and outputs a single discriminant. In order to avoid bias, the data in the signal search regions were not examined (blinded) until all the selection requirements were decided.

In the preselection, the J/ψ candidates are formed from two oppositely charged par-ticles with pT greater than 500 MeV, identified as muons and consistent with originating

from a common vertex but inconsistent with originating from any PV. The invariant mass of the µ+_µ− _{pair is required to be within [−48, +43] MeV of the known J/ψ mass [10],}

corresponding to a window of about ±3 times the mass resolution. The asymmetry in the mass window is due to the radiative tail. Pion, kaon, and proton candidates are required to be positively identified in the RICH detector, but with loose requirements as the MVA includes particle identification criteria. Kaon and proton candidates are required to have momenta greater than 5 GeV and 10 GeV, respectively, to avoid regions with suboptimal particle identification. Each track must have an IP χ2 _{greater 9 than with respect to the}

closest PV, must have pT greater than 250 MeV, and the scalar sum of the tracks pT is

required to be larger than 900 MeV. All of the tracks forming the pentaquark state are required to form a good vertex and have a significant detachment from the PV. We also require that the cosine of the angle between the vector from the PV to the PB candidate

vertex (~VP V −PB) and the PB candidate momentum vector (~pPB) be greater than 0.999. The invariant mass of the pentaquark states is calculated by constraining the invariant mass of the dimuon pair to the known J/ψ mass, the muon tracks to originate from the

Mass [MeV]

Candidates/(40 MeV)

LHCb

Figure 2: Invariant mass distributions above the decay mass thresholds for the indicated modes.

J/ψ vertex and the vector sum of the momenta of the final state particles to point back to the PV.

We measure the product of the production cross section and branching fraction of these pentaquark states and normalize it to the analogous measurement [18] by the LHCb collaboration for the Λ0

b baryon in the Λ0b → J/ψ K

−_{p decay. To this end, we impose the}

same kinematic requirements on the PB candidate as applied to the Λ0b candidates in that

analysis, namely pT < 20 GeV and 2.0 < y < 4.5, where y = 1₂ ln



E+pz E−pz



is the rapidity, E the energy and pz the component of the momentum along the beam direction. After

these preselections, the product of trigger and reconstruction efficiencies is around 2% for all the modes.

4

Selection optimization by a multivariate classifier

The MVA classifier is trained using the simulated signal samples described at the end of Section 2 and a background sample of candidates in data with invariant masses within 0.5 GeV above the strong-decay threshold in each final state (see Fig. 2). We use 3 × 106

P_B+0_p → (J/ψ → µ+µ−)K+π−p simulated events for modes I, II and III, with the P + B0_p mass set to 5750 MeV, and 3 × 106 _P+

B0

sp → (J/ψ → µ

+_µ−_{)(φ → K}+_K−_{)p simulated}

events for mode IV, with the P_B+0

sp mass set to 5835 MeV. The dependence of the selection efficiency as a function of mass is accounted for in Section 5.

The training samples needed to model the backgrounds in the signal regions must represent the actual backgrounds as closely as possible. Contamination in the background samples can occur from fully reconstructed weakly decaying b-hadrons that are combined with random particles. In mode I, we find contributions from B0 _{→ J/ψ K}+_π− _{decays and}

B0

s → J/ψ K+K

−_{decays where one of the kaons is misidentified as a pion; then a random}

III, along with the B0 and B_s0 contaminations, a Λ0_b → J/ψ K−_{p decay can be paired}

with a random pion. In mode IV, only the B0 _{and B}0

s contaminations are seen. These

mistaken identification contributions in the background sample are found by looking at the invariant mass distributions obtained by switching one or more final-state particles to another mass hypothesis. If this produces a peak in the mass distribution at the mass of a known particle, we apply a veto in the background training sample eliminating all candidates within ±12 MeV of the peaks, approximately ±1.6 σ. No such peaks are seen in the signal region, after switching the mass hypotheses, for any of the modes. As an example, we show fully reconstructed decays in the background and signal regions for mode I in Fig. 3.

The input variables used to train the classifier for modes I, II, and III are the same. We use the difference in the logarithm of the likelihood for two different particle hypotheses (DLL). They are the DLL(µ − π) for the two muons, DLL(K − π) and DLL(K − p) for the kaon, DLL(p − π) and DLL(p − K) for the proton, and DLL(π − K) for the pion. Also used is the logarithm of χ2

IP, defined as the difference in χ2 of a given PV reconstructed

with and without the considered K, π, and p tracks, and the χ2 of the PB to be consistent

with originating from the PV. Other variables are the logarithm of the cosine of the angle of ~pPB with ~VP V −PB, the flight distance of PB, the scalar sum pT of the K, π and p tracks, the χ2/ndof of the fit of all the decay tracks to the PB vertex, and of the two muon tracks

to the J/ψ vertex with constraints that fix the dimuon invariant mass to the J/ψ mass and force the PB candidate to point back to the PV, where ndof indicates the number

of degrees of freedom. The input variables used to train the classifier for mode IV are similar, but with two kaons instead of a kaon and a pion.

Two important attributes of multivariate classifiers are signal efficiency and back-ground rejection, both of which we wish to maximize. Using the input variables and training samples described earlier, we compared the performances of some common clas-sifiers, including Boosted Decision Trees (BDT), Gradient Boosted Decision Trees, Linear

[MeV] ) -π + K ψ (J/ m 5000 5200 5400 5600 5800 6000 Candidates/(10 MeV) 2000 4000 6000 8000 LHCb [MeV] ) -π + K ψ (J/ m 5000 5200 5400 5600 5800 6000 Candidates/(10 MeV) 200 400 600 800 1000 1200 LHCb (a) (b)

Figure 3: For the P_B+0_p→ J/ψ K+π

−_{p decay search (mode I), the invariant mass of J/ψ K}+_π−

combinations in the (a) region above threshold and in the (b) signal region. The peak in the sideband region results from B0 _decays.

BDT response 0.5 − 0 0.5 dx / (1/N) dN 0 0.5 1 1.5 2 2.5 3 3.5 4

_(a)

Cut value applied on BDT output

0.6 − −0.4 −0.2 0 0.2 0.4 Efficiency 0 0.2 0.4 0.6 0.8 1 Significance 0 2 4 6 8 10 12 14

(b)

Figure 4: (a) Outputs of the BDT classifier for the J/ψ K+π−p final state. The circles (blue) show the signal training sample, and the triangles (red) show the background training sample, while the shaded (blue) histogram shows the signal test sample, and the diagonal (red) line-shaded histogram the background test sample. (b) Efficiencies of signal, solid (blue) curve, and background, dotted (red) curve, and the value of the S/(√B + 1.5), dashed (green) curve, called “significance,” as a function of the BDT output.

Discriminant, and Likelihood Estimators [19]. We base our MVA selection on the BDT algorithm. Once the BDT classifier is trained, it is evaluated by applying it to a sepa-rate testing sample (which is disjoint from the data sample used to train the classifier). The classifier assigns a response (called the BDT output) valued between –1 and 1 to the events, with background events tending toward low values and signal events to high values. These can be seen in Fig. 4(a) for mode I. The BDT outputs for other modes look very similar.

Discrimination between signal candidates, S, and background, B, is accomplished by choosing a BDT value that maximizes the metric S

a/2+√B, where a is the significance

of the signal sought, which has the advantage of being independent of the signal cross section [20]. We choose a to be 3 for all modes, based on the assumption that we are in a situation of looking for a small signal in the midst of larger backgrounds. The variation of the signal and background efficiencies and the metric’s value with the BDT output is shown in Fig. 4(b) for mode I. This variation of efficiencies and the metric with respect to the BDT value is similar for the other modes. After optimization, the BDT signal efficiency varies from 42.9% to 71.4% depending on the decay mode.

One cause of concern is reflections where the particle identification fails leading to the inclusion of other well-known final states. These are eliminated with a small loss of efficiency by removing candidate combinations within ±12 MeV of the appropriate b-hadron mass. A list of these reflections in the particular modes of interest is given in Table 2.

5

Results

After the selections were decided upon, the analysis was unblinded. A search is conducted by scanning the PB invariant mass distributions in the four final states shown in Fig. 5.

The step size used in these scans is 4.0 MeV, corresponding to about half the invariant mass resolution. No signal is observed with the expected width of approximately 7.5 MeV. The PB mass resolution seen in the simulated samples is 6.0 MeV for modes I, II, III,

and 5.2 MeV for mode IV which, as expected, is similar to the 7.5 MeV width seen in data for the Λ0

b baryon in the (J/ψ → µ+µ

−_)K−_{p final state, when the two muons are}

constrained to the J/ψ mass. In order to obtain conservative results, we set upper limits based on the wider 7.5 MeV signal width.

At each PB scan mass value mPB, the signal region is a ±2σ(mPB) window around mPB, while the background is estimated by interpolating the yields in the sidebands starting at 3σ(mPB) from mPB and extending to 5σ(mPB), both below and above mPB following Ref. [21]. The statistical test at each mass is based on the profile likelihood ratio of Poisson-process hypotheses with and without a signal contribution, where the uncertainty on the background interpolation is modeled as purely Poisson (see Ref. [21] for details). No significant excess of signal candidates is observed over the expected background. The upper limits are set on the signal yields using the profile likelihood technique, in which systematic uncertainties are handled by including additional Gaussian terms in the likelihood.

In the absence of a significant signal, we set upper limits in each PB candidate mass

interval on the ratio

R = σ(pp → PBX) · B(PB → J/ψ X) σ(pp → Λ0

bX) · B(Λ0b → J/ψ K−p)

, (1)

where we use the Λ0

b → J/ψ K

−_{p channel for normalization. The product of the production}

cross section and branching fraction of this channel has been measured by the LHCb

Table 2: Decay modes that are vetoed for each pentaquark candidate mode and the specific particle misidentification that causes the reflection.

Search mode Reflection Particle misidentification P_B+0_p → J/ψ K+π −_{p B}+_{→ J/ψ K}+_π−_π+ _π+ _{to p} B+→ J/ψ π+_π−_K+ _π+ _{to K}+ _{and K}+ _{to p} P_Λ−0 bπ− → J/ψ K−_π−_{p B}−_{→ J/ψ K}−_π−_π+ _π+ _{to p} B−→ J/ψ (φ → K−_K+_)π− _K+ _{to p} P_Λ+0 bπ+ → J/ψ K−_π+_{p B}+_{→ J/ψ (φ → K}−_K+_)π+ _K+ _{to p} P_B+0 sp → J/ψ φp B +_{→ J/ψ φK}+ _K+ _{to p}

[MeV] p) -π + K ψ J/ m( 5000 5500 6000 Candidates/(4 MeV) 0 2 4 6 8 10 12 LHCb (a) -5000 5500 Candidates/(4 MeV) 0 5 10 15 20 25 LHCb (b) [MeV] p) + π K ψ J/ m( 5000 5500 Candidates/(4 MeV) 0 5 10 15 20 25 LHCb (c) ) [MeV] p φ ψ J/ m( 5500 6000 Candidates/(4 MeV) 0 1 2 3 4 5 6 LHCb (d) p) -π K ψ J/ m( [MeV]

Figure 5: Reconstructed mass distributions after the BDT selection for the (a) J/ψ K+π−p, (b) J/ψ K−π−p, (c) J/ψ K−π+p, and (d) J/ψ φp final states.

collaboration [18] to be

σ(Λ0_b,√s = 7 TeV) · B(Λ0_b → J/ψ K−p) = 6.12 ± 0.10 ± 0.25 nb,

σ(Λ0_b,√s = 8 TeV) · B(Λ0_b → J/ψ K−p) = 7.51 ± 0.08 ± 0.31 nb, (2) where the uncertainties are statistical and systematic, respectively. The systematic un-certainties include those on the luminosity and detection efficiencies that partially cancel, lowering the effective systematic uncertainty on the normalization. These measurements are averaged, taking into account the different luminosities at the two energies, to produce the overall normalization factor of N F = 7.03 ± 0.06 ± 0.17 nb.

Simulations have been generated at four different PB masses for each decay mode. The

total selection efficiency varies from 0.45% to 1.4% depending on mass and decay mode. The mass dependence of the efficiencies is parametrized by a second-order polynomial, for each decay mode, and incorporated into the upper limit calculation. The dominant source of uncertainty on the efficiency is systematic, and arises from the calibration applied to the particle identification as calculated by the simulation. This absolute efficiency uncertainty varies from 0.02% to 0.17% depending on the decay mode. The statistical uncertainties on the efficiency are negligible. Note that we are taking the PB lifetime as 1.5 ps, and all

simulated efficiencies assume that the PB decays are given by phase space.

For modes I, II, and III, the upper limits on S are normalized to obtain the upper limits on R according to

UL(R) = UL(S)

L · B(J/ψ → µ+_µ−_{) · N F} , (3)

where UL(S) is the efficiency corrected upper limit on S in each particular mass bin, L is the integrated luminosity and B(J/ψ → µ+_µ−_{) is the branching fraction for the}

J/ψ → µ+µ− decay. For mode IV, an additional factor of B(φ → K+K−), which is the branching fraction for the φ → K+_K− _{decay, is included in the denominator of Eq. 3.}

The systematic uncertainty on UL(R) arises from the differences in analysis require-ments between the search mode and the normalization mode (2%), which is estimated based on the differences the selection requirements could make in the relative efficiencies. The detection of an additional track (1%), given by the uncertainty in the data-driven tracking efficiency corrections, and the identification of this track (1%), given by the uncer-tainties in the particle identification calibration procedure, leads to an overall systematic uncertainty of 2.4%. For mode IV, the small uncertainty on B(φ → K+_K−_{) is also taken}

into account. These uncertainties are added in quadrature with the uncertainty on N F . The upper limits on R are then increased linearly by this small systematic uncertainty. The results for UL(R) at 90% confidence level (CL) are shown in Fig. 6. Low invariant mass cut-offs in each mode are imposed when the efficiency uncertainty becomes large.

6

Conclusions

We have searched for pentaquark states containing a b quark that decay weakly via the b → ccs transition in the final states J/ψ K+π−p, J/ψ K−π−p, J/ψ K−π+p, and J/ψ φp. Such states have been speculated to exist [3–6]. No evidence for these decays is found. Upper limits at 90% confidence level on the ratio of the production cross sections of these states times the branching fractions into the search modes, with respect to the production and decay of the Λ0

b baryon in the mode J/ψ K

−_{p (R, see Eq. 1) are found to be about}

10−3, depending on the final state and the hypothesized mass of the pentaquark state.

Acknowledgements

We thank I. Klebanov for useful discussions. 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 (The Netherlands); MNiSW and NCN (Poland); MEN/IFA (Romania); MinES and FASO (Russia); MinECo (Spain); SNSF and SER (Switzerland); NASU (Ukraine); STFC (United Kingdom); NSF (USA). We acknowledge

) [MeV] p -π + K ψ J/ m( b Λ B)× σ /( B P B)× σ UL( ) [MeV] p π K ψ J/ m( b Λ B)× σ /( B P B)× σ UL( ) [MeV] p + π K ψ J/ m( b Λ B)× σ /( B P B)× σ UL( ) [MeV] p φ ψ J/ m( b Λ B)× σ /( B P B)× σ UL( 5000 5500 6000 3 − 10 LHCb

(a)

(b)

(c)

(d)

Figure 6: Upper limits on R at 90% CL for (a) J/ψ K+π−p, (b) J/ψ K−π−p, (c) J/ψ K−π+p, and (d) J/ψ φp final states.

the computing resources that are provided by CERN, IN2P3 (France), KIT and DESY (Germany), INFN (Italy), SURF (The Netherlands), PIC (Spain), GridPP (United King-dom), RRCKI and Yandex LLC (Russia), CSCS (Switzerland), IFIN-HH (Romania), CBPF (Brazil), PL-GRID (Poland) and OSC (USA). We are indebted to the communi-ties behind the multiple open-source software packages on which we depend. Individual groups or members have received support from AvH Foundation (Germany), EPLANET, Marie Sk lodowska-Curie Actions and ERC (European Union), ANR, Labex P2IO, ENIG-MASS and OCEVU, and R´egion Auvergne-Rhˆone-Alpes (France), RFBR and Yandex LLC (Russia), GVA, XuntaGal and GENCAT (Spain), Herchel Smith Fund, the Royal Society, the English-Speaking Union and the Leverhulme Trust (United Kingdom).

References

[1] LHCb collaboration, R. Aaij et al., Observation of J/ψ p resonances consistent with pentaquark states in Λ0_b → J/ψ K−_{p decays, Phys. Rev. Lett. 115 (2015) 072001,}

arXiv:1507.03414.

[2] T. H. R. Skyrme, A non-linear field theory, Proc. Roy. Soc. Lond. A260 (1961) 127. [3] Private communication from I. Klebanov.

[4] I. W. Stewart, M. E. Wessling, and M. B. Wise, Stable heavy pentaquark states, Phys. Lett. B590 (2004) 185, arXiv:hep-ph/0402076.

[5] A. K. Leibovich, Z. Ligeti, I. W. Stewart, and M. B. Wise, Predictions for nonleptonic Λ0

b and Θb decays, Phys. Lett. B586 (2004) 337, arXiv:hep-ph/0312319.

[6] Y. S. Oh, B. Y. Park, and D. P. Min, Pentaquark exotic baryons in the Skyrme model, Phys. Lett. B331 (1994) 362, arXiv:hep-ph/9405297.

[7] LHCb collaboration, R. Aaij et al., Measurement of b-hadron production fractions in 7 TeV pp collisions, Phys. Rev. D85 (2012) 032008, arXiv:1111.2357.

[8] LHCb collaboration, A. A. Alves Jr. et al., The LHCb detector at the LHC, JINST 3 (2008) S08005.

[9] LHCb collaboration, R. Aaij et al., LHCb detector performance, Int. J. Mod. Phys. A30 (2015) 1530022, arXiv:1412.6352.

[10] Particle Data Group, C. Patrignani et al., Review of Particle Physics, Chin. Phys. C40 (2016 and 2017 update) 100001.

[11] T. Sj¨ostrand, S. Mrenna, and P. Skands, PYTHIA 6.4 physics and manual, JHEP 05 (2006) 026, arXiv:hep-ph/0603175; T. Sj¨ostrand, S. Mrenna, and P. Skands, A brief introduction to PYTHIA 8.1, Comput. Phys. Commun. 178 (2008) 852, arXiv:0710.3820.

[12] I. Belyaev et al., Handling of the generation of primary events in Gauss, the LHCb simulation framework, J. Phys. Conf. Ser. 331 (2011) 032047.

[13] D. J. Lange, The EvtGen particle decay simulation package, Nucl. Instrum. Meth. A462 (2001) 152.

[14] P. Golonka and Z. Was, PHOTOS Monte Carlo: A precision tool for QED corrections in Z and W decays, Eur. Phys. J. C45 (2006) 97, arXiv:hep-ph/0506026.

[15] Geant4 collaboration, J. Allison et al., Geant4 developments and applications, IEEE Trans. Nucl. Sci. 53 (2006) 270; Geant4 collaboration, S. Agostinelli et al., Geant4: A simulation toolkit, Nucl. Instrum. Meth. A506 (2003) 250.

[16] M. Clemencic et al., The LHCb simulation application, Gauss: Design, evolution and experience, J. Phys. Conf. Ser. 331 (2011) 032023.

[17] L. Breiman, J. H. Friedman, R. A. Olshen, and C. J. Stone, Classification and re-gression trees, Wadsworth international group, Belmont, California, USA, 1984. [18] LHCb collaboration, R. Aaij et al., Study of the production of Λ0

b and B0 hadrons in

pp collisions and first measurement of the Λ0

b → J/ψpK

− _{branching fraction, Chin.}

Phys. C40 (2016) 011001, arXiv:1509.00292.

[19] A. Hoecker et al., TMVA: Toolkit for multivariate data analysis, PoS ACAT (2007) 040, arXiv:physics/0703039.

[20] G. Punzi, Sensitivity of searches for new signals and its optimization, in Statistical Problems in Particle Physics, Astrophysics, and Cosmology (L. Lyons, R. Mount, and R. Reitmeyer, eds.), p. 79, 2003. arXiv:physics/0308063.

[21] M. Williams, Searching for a particle of unknown mass and lifetime in the presence of an unknown non-monotonic background, JINST 10 (2015) P06002, arXiv:1503.04767.

LHCb collaboration

R. Aaij40, B. Adeva39, M. Adinolfi48, Z. Ajaltouni5, S. Akar59, J. Albrecht10, F. Alessio40, M. Alexander53, A. Alfonso Albero38, S. Ali43, G. Alkhazov31, P. Alvarez Cartelle55,

A.A. Alves Jr59, S. Amato2, S. Amerio23, Y. Amhis7, L. An3, L. Anderlini18, G. Andreassi41, M. Andreotti17,g_{, J.E. Andrews}60_{, R.B. Appleby}56_{, F. Archilli}43_{, P. d’Argent}12_,

J. Arnau Romeu6, A. Artamonov37, M. Artuso61, E. Aslanides6, M. Atzeni42, G. Auriemma26, M. Baalouch5, I. Babuschkin56, S. Bachmann12, J.J. Back50, A. Badalov38,m, C. Baesso62, S. Baker55_{, V. Balagura}7,b_{, W. Baldini}17_{, A. Baranov}35_{, R.J. Barlow}56_{, C. Barschel}40_,

S. Barsuk7, W. Barter56, F. Baryshnikov32, V. Batozskaya29, V. Battista41, A. Bay41, L. Beaucourt4, J. Beddow53, F. Bedeschi24, I. Bediaga1, A. Beiter61, L.J. Bel43, N. Beliy63, V. Bellee41_{, N. Belloli}21,i_{, K. Belous}37_{, I. Belyaev}32,40_{, E. Ben-Haim}8_{, G. Bencivenni}19_,

S. Benson43, S. Beranek9, A. Berezhnoy33, R. Bernet42, D. Berninghoff12, E. Bertholet8, A. Bertolin23, C. Betancourt42, F. Betti15, M.O. Bettler40, M. van Beuzekom43,

Ia. Bezshyiko42_{, S. Bifani}47_{, P. Billoir}8_{, A. Birnkraut}10_{, A. Bizzeti}18,u_{, M. Bjørn}57_{, T. Blake}50_,

F. Blanc41, S. Blusk61, V. Bocci26, T. Boettcher58, A. Bondar36,w, N. Bondar31, I. Bordyuzhin32, S. Borghi56,40, M. Borisyak35, M. Borsato39, F. Bossu7, M. Boubdir9, T.J.V. Bowcock54, E. Bowen42, C. Bozzi17,40, S. Braun12, J. Brodzicka27, D. Brundu16, E. Buchanan48, C. Burr56, A. Bursche16,f, J. Buytaert40, W. Byczynski40, S. Cadeddu16, H. Cai64, R. Calabrese17,g, R. Calladine47, M. Calvi21,i, M. Calvo Gomez38,m, A. Camboni38,m, P. Campana19, D.H. Campora Perez40, L. Capriotti56, A. Carbone15,e, G. Carboni25,j,

R. Cardinale20,h, A. Cardini16, P. Carniti21,i, L. Carson52, K. Carvalho Akiba2, G. Casse54, L. Cassina21, M. Cattaneo40, G. Cavallero20,40,h, R. Cenci24,t, D. Chamont7, M.G. Chapman48, M. Charles8, Ph. Charpentier40, G. Chatzikonstantinidis47, M. Chefdeville4, S. Chen16,

S.F. Cheung57, S.-G. Chitic40, V. Chobanova39, M. Chrzaszcz42, A. Chubykin31,

P. Ciambrone19, X. Cid Vidal39, G. Ciezarek40, P.E.L. Clarke52, M. Clemencic40, H.V. Cliff49, J. Closier40, V. Coco40, J. Cogan6, E. Cogneras5, V. Cogoni16,f, L. Cojocariu30, P. Collins40, T. Colombo40, A. Comerma-Montells12, A. Contu16, G. Coombs40, S. Coquereau38, G. Corti40, M. Corvo17,g, C.M. Costa Sobral50, B. Couturier40, G.A. Cowan52, D.C. Craik58,

A. Crocombe50, M. Cruz Torres1, R. Currie52, C. D’Ambrosio40, F. Da Cunha Marinho2, C.L. Da Silva73, E. Dall’Occo43, J. Dalseno48, A. Davis3, O. De Aguiar Francisco40, K. De Bruyn40, S. De Capua56, M. De Cian12, J.M. De Miranda1, L. De Paula2,

M. De Serio14,d, P. De Simone19, C.T. Dean53, D. Decamp4, L. Del Buono8, H.-P. Dembinski11, M. Demmer10, A. Dendek28, D. Derkach35, O. Deschamps5, F. Dettori54, B. Dey65,

A. Di Canto40, P. Di Nezza19, H. Dijkstra40, F. Dordei40, M. Dorigo40, A. Dosil Su´arez39, L. Douglas53, A. Dovbnya45, K. Dreimanis54, L. Dufour43, G. Dujany8, P. Durante40, J.M. Durham73, D. Dutta56, R. Dzhelyadin37, M. Dziewiecki12, A. Dziurda40, A. Dzyuba31, S. Easo51, M. Ebert52, U. Egede55, V. Egorychev32, S. Eidelman36,w, S. Eisenhardt52, U. Eitschberger10, R. Ekelhof10, L. Eklund53, S. Ely61, S. Esen12, H.M. Evans49, T. Evans57, A. Falabella15_{, N. Farley}47_{, S. Farry}54_{, D. Fazzini}21,i_{, L. Federici}25_{, D. Ferguson}52_,

G. Fernandez38, P. Fernandez Declara40, A. Fernandez Prieto39, F. Ferrari15,

L. Ferreira Lopes41, F. Ferreira Rodrigues2, M. Ferro-Luzzi40, S. Filippov34, R.A. Fini14, M. Fiorini17,g_{, M. Firlej}28_{, C. Fitzpatrick}41_{, T. Fiutowski}28_{, F. Fleuret}7,b_{, M. Fontana}16,40_,

F. Fontanelli20,h, R. Forty40, V. Franco Lima54, M. Frank40, C. Frei40, J. Fu22,q, W. Funk40, E. Furfaro25,j, C. F¨arber40, E. Gabriel52, A. Gallas Torreira39, D. Galli15,e, S. Gallorini23, S. Gambetta52_{, M. Gandelman}2_{, P. Gandini}22_{, Y. Gao}3_{, L.M. Garcia Martin}71_,

J. Garc´ıa Pardi˜nas39, J. Garra Tico49, L. Garrido38, D. Gascon38, C. Gaspar40, L. Gavardi10, G. Gazzoni5, D. Gerick12, E. Gersabeck56, M. Gersabeck56, T. Gershon50, Ph. Ghez4,

S. Gian`ı41_{, V. Gibson}49_{, O.G. Girard}41_{, L. Giubega}30_{, K. Gizdov}52_{, V.V. Gligorov}8_,

D. Golubkov32, A. Golutvin55,69,y, A. Gomes1,a, I.V. Gorelov33, C. Gotti21,i, E. Govorkova43, J.P. Grabowski12, R. Graciani Diaz38, L.A. Granado Cardoso40, E. Graug´es38, E. Graverini42, G. Graziani18_{, A. Grecu}30_{, R. Greim}9_{, P. Griffith}16_{, L. Grillo}56_{, L. Gruber}40_,

B.R. Gruberg Cazon57, O. Gr¨unberg67, E. Gushchin34, Yu. Guz37, T. Gys40, C. G¨obel62, T. Hadavizadeh57, C. Hadjivasiliou5, G. Haefeli41, C. Haen40, S.C. Haines49, B. Hamilton60, X. Han12, T.H. Hancock57, S. Hansmann-Menzemer12, N. Harnew57, S.T. Harnew48,

C. Hasse40, M. Hatch40, J. He63, M. Hecker55, K. Heinicke10, A. Heister9, K. Hennessy54, P. Henrard5, L. Henry71, E. van Herwijnen40, M. Heß67, A. Hicheur2, D. Hill57,

P.H. Hopchev41, W. Hu65, W. Huang63, Z.C. Huard59, W. Hulsbergen43, T. Humair55,

M. Hushchyn35, D. Hutchcroft54, P. Ibis10, M. Idzik28, P. Ilten47, R. Jacobsson40, J. Jalocha57, E. Jans43, A. Jawahery60, F. Jiang3, M. John57, D. Johnson40, C.R. Jones49, C. Joram40, B. Jost40, N. Jurik57, S. Kandybei45, M. Karacson40, J.M. Kariuki48, S. Karodia53,

N. Kazeev35, M. Kecke12, F. Keizer49, M. Kelsey61, M. Kenzie49, T. Ketel44, E. Khairullin35, B. Khanji12, C. Khurewathanakul41, T. Kirn9, S. Klaver19, K. Klimaszewski29,

T. Klimkovich11, S. Koliiev46, M. Kolpin12, R. Kopecna12, P. Koppenburg43,

A. Kosmyntseva32, S. Kotriakhova31, M. Kozeiha5, L. Kravchuk34, M. Kreps50, F. Kress55, P. Krokovny36,w, W. Krzemien29, W. Kucewicz27,l, M. Kucharczyk27, V. Kudryavtsev36,w, A.K. Kuonen41, T. Kvaratskheliya32,40, D. Lacarrere40, G. Lafferty56, A. Lai16,

G. Lanfranchi19, C. Langenbruch9, T. Latham50, C. Lazzeroni47, R. Le Gac6, A. Leflat33,40, J. Lefran¸cois7, R. Lef`evre5, F. Lemaitre40, E. Lemos Cid39, O. Leroy6, T. Lesiak27,

B. Leverington12, P.-R. Li63, T. Li3, Y. Li7, Z. Li61, X. Liang61, T. Likhomanenko68, R. Lindner40, F. Lionetto42, V. Lisovskyi7, X. Liu3, D. Loh50, A. Loi16, I. Longstaff53, J.H. Lopes2, D. Lucchesi23,o, M. Lucio Martinez39, H. Luo52, A. Lupato23, E. Luppi17,g,

O. Lupton40, A. Lusiani24, X. Lyu63, F. Machefert7, F. Maciuc30, V. Macko41, P. Mackowiak10, S. Maddrell-Mander48, O. Maev31,40, K. Maguire56, D. Maisuzenko31, M.W. Majewski28, S. Malde57, B. Malecki27, A. Malinin68, T. Maltsev36,w, G. Manca16,f, G. Mancinelli6, D. Marangotto22,q, J. Maratas5,v, J.F. Marchand4, U. Marconi15, C. Marin Benito38, M. Marinangeli41_{, P. Marino}41_{, J. Marks}12_{, G. Martellotti}26_{, M. Martin}6_{, M. Martinelli}41_,

D. Martinez Santos39, F. Martinez Vidal71, A. Massafferri1, R. Matev40, A. Mathad50, Z. Mathe40, C. Matteuzzi21, A. Mauri42, E. Maurice7,b, B. Maurin41, A. Mazurov47, M. McCann55,40_{, A. McNab}56_{, R. McNulty}13_{, J.V. Mead}54_{, B. Meadows}59_{, C. Meaux}6_,

F. Meier10, N. Meinert67, D. Melnychuk29, M. Merk43, A. Merli22,40,q, E. Michielin23, D.A. Milanes66, E. Millard50, M.-N. Minard4, L. Minzoni17, D.S. Mitzel12, A. Mogini8, J. Molina Rodriguez1_{, T. Momb¨acher}10_{, I.A. Monroy}66_{, S. Monteil}5_{, M. Morandin}23_,

M.J. Morello24,t, O. Morgunova68, J. Moron28, A.B. Morris52, R. Mountain61, F. Muheim52, M. Mulder43, D. M¨uller56, J. M¨uller10, K. M¨uller42, V. M¨uller10, P. Naik48, T. Nakada41, R. Nandakumar51_{, A. Nandi}57_{, I. Nasteva}2_{, M. Needham}52_{, N. Neri}22,40_{, S. Neubert}12_,

N. Neufeld40, M. Neuner12, T.D. Nguyen41, C. Nguyen-Mau41,n, S. Nieswand9, R. Niet10, N. Nikitin33, T. Nikodem12, A. Nogay68, D.P. O’Hanlon50, A. Oblakowska-Mucha28, V. Obraztsov37, S. Ogilvy19, R. Oldeman16,f, C.J.G. Onderwater72, A. Ossowska27, J.M. Otalora Goicochea2, P. Owen42, A. Oyanguren71, P.R. Pais41, A. Palano14, M. Palutan19,40, A. Papanestis51, M. Pappagallo52, L.L. Pappalardo17,g, W. Parker60, C. Parkes56, G. Passaleva18,40, A. Pastore14,d, M. Patel55, C. Patrignani15,e, A. Pellegrino43,

G. Penso26, M. Pepe Altarelli40, S. Perazzini40, D. Pereima32, P. Perret5, L. Pescatore41, K. Petridis48, A. Petrolini20,h, A. Petrov68, M. Petruzzo22,q, E. Picatoste Olloqui38,

B. Pietrzyk4_{, G. Pietrzyk}41_{, M. Pikies}27_{, D. Pinci}26_{, F. Pisani}40_{, A. Pistone}20,h_{, A. Piucci}12_,

V. Placinta30, S. Playfer52, M. Plo Casasus39, F. Polci8, M. Poli Lener19, A. Poluektov50, I. Polyakov61, E. Polycarpo2, G.J. Pomery48, S. Ponce40, A. Popov37, D. Popov11,40, S. Poslavskii37_{, C. Potterat}2_{, E. Price}48_{, J. Prisciandaro}39_{, C. Prouve}48_{, V. Pugatch}46_,

A. Puig Navarro42, H. Pullen57, G. Punzi24,p, W. Qian50, J. Qin63, R. Quagliani8, B. Quintana5, B. Rachwal28, J.H. Rademacker48, M. Rama24, M. Ramos Pernas39, M.S. Rangel2, I. Raniuk45,†, F. Ratnikov35,x, G. Raven44, M. Ravonel Salzgeber40,

M. Reboud4, F. Redi41, S. Reichert10, A.C. dos Reis1, C. Remon Alepuz71, V. Renaudin7, S. Ricciardi51, S. Richards48, M. Rihl40, K. Rinnert54, P. Robbe7, A. Robert8,

A.B. Rodrigues41, E. Rodrigues59, J.A. Rodriguez Lopez66, A. Rogozhnikov35, S. Roiser40, A. Rollings57, V. Romanovskiy37, A. Romero Vidal39,40, M. Rotondo19, M.S. Rudolph61, T. Ruf40, P. Ruiz Valls71, J. Ruiz Vidal71, J.J. Saborido Silva39, E. Sadykhov32, N. Sagidova31, B. Saitta16,f, V. Salustino Guimaraes62, C. Sanchez Mayordomo71, B. Sanmartin Sedes39, R. Santacesaria26, C. Santamarina Rios39, M. Santimaria19, E. Santovetti25,j, G. Sarpis56, A. Sarti19,k, C. Satriano26,s, A. Satta25, D.M. Saunders48, D. Savrina32,33, S. Schael9, M. Schellenberg10, M. Schiller53, H. Schindler40, M. Schmelling11, T. Schmelzer10,

B. Schmidt40, O. Schneider41, A. Schopper40, H.F. Schreiner59, M. Schubiger41, M.H. Schune7, R. Schwemmer40, B. Sciascia19, A. Sciubba26,k, A. Semennikov32, E.S. Sepulveda8, A. Sergi47, N. Serra42, J. Serrano6, L. Sestini23, P. Seyfert40, M. Shapkin37, I. Shapoval45, Y. Shcheglov31, T. Shears54, L. Shekhtman36,w, V. Shevchenko68, B.G. Siddi17, R. Silva Coutinho42,

L. Silva de Oliveira2, G. Simi23,o, S. Simone14,d, M. Sirendi49, N. Skidmore48, T. Skwarnicki61, I.T. Smith52, J. Smith49, M. Smith55, l. Soares Lavra1, M.D. Sokoloff59, F.J.P. Soler53,

B. Souza De Paula2, B. Spaan10, P. Spradlin53, S. Sridharan40, F. Stagni40, M. Stahl12, S. Stahl40, P. Stefko41, S. Stefkova55, O. Steinkamp42, S. Stemmle12, O. Stenyakin37, M. Stepanova31, H. Stevens10, S. Stone61, B. Storaci42, S. Stracka24,p, M.E. Stramaglia41, M. Straticiuc30, U. Straumann42, J. Sun3, L. Sun64, K. Swientek28, V. Syropoulos44, T. Szumlak28, M. Szymanski63, S. T’Jampens4, A. Tayduganov6, T. Tekampe10,

G. Tellarini17,g, F. Teubert40, E. Thomas40, J. van Tilburg43, M.J. Tilley55, V. Tisserand5, M. Tobin41_{, S. Tolk}49_{, L. Tomassetti}17,g_{, D. Tonelli}24_{, R. Tourinho Jadallah Aoude}1_,

E. Tournefier4, M. Traill53, M.T. Tran41, M. Tresch42, A. Trisovic49, A. Tsaregorodtsev6, P. Tsopelas43, A. Tully49, N. Tuning43,40, A. Ukleja29, A. Usachov7, A. Ustyuzhanin35, U. Uwer12_{, C. Vacca}16,f_{, A. Vagner}70_{, V. Vagnoni}15,40_{, A. Valassi}40_{, S. Valat}40_{, G. Valenti}15_,

R. Vazquez Gomez40, P. Vazquez Regueiro39, S. Vecchi17, M. van Veghel43, J.J. Velthuis48, M. Veltri18,r, G. Veneziano57, A. Venkateswaran61, T.A. Verlage9, M. Vernet5,

M. Vesterinen57_{, J.V. Viana Barbosa}40_{, D. Vieira}63_{, M. Vieites Diaz}39_{, H. Viemann}67_,

X. Vilasis-Cardona38,m, M. Vitti49, V. Volkov33, A. Vollhardt42, B. Voneki40, A. Vorobyev31, V. Vorobyev36,w, C. Voß9, J.A. de Vries43, C. V´azquez Sierra43, R. Waldi67, J. Walsh24, J. Wang61_{, Y. Wang}65_{, D.R. Ward}49_{, H.M. Wark}54_{, N.K. Watson}47_{, D. Websdale}55_,

A. Weiden42, C. Weisser58, M. Whitehead40, J. Wicht50, G. Wilkinson57, M. Wilkinson61, M. Williams56, M. Williams58, T. Williams47, F.F. Wilson51,40, J. Wimberley60, M. Winn7, J. Wishahi10, W. Wislicki29, M. Witek27, G. Wormser7, S.A. Wotton49, K. Wyllie40, Y. Xie65, M. Xu65, Q. Xu63, Z. Xu3, Z. Xu4, Z. Yang3, Z. Yang60, Y. Yao61, H. Yin65, J. Yu65,

X. Yuan61, O. Yushchenko37, K.A. Zarebski47, M. Zavertyaev11,c, L. Zhang3, Y. Zhang7, A. Zhelezov12, Y. Zheng63, X. Zhu3, V. Zhukov9,33, J.B. Zonneveld52, S. Zucchelli15.

1_{Centro Brasileiro de Pesquisas F´ısicas (CBPF), Rio de Janeiro, Brazil} 2_{Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil} 3_{Center for High Energy Physics, Tsinghua University, Beijing, China}

4_{Univ. Grenoble Alpes, Univ. Savoie Mont Blanc, CNRS, IN2P3-LAPP, Annecy, France} 5_{Clermont Universit´e, Universit´e Blaise Pascal, CNRS/IN2P3, LPC, Clermont-Ferrand, France} 6_{Aix Marseille Univ, CNRS/IN2P3, CPPM, Marseille, France}

7_{LAL, Univ. Paris-Sud, CNRS/IN2P3, Universit´e Paris-Saclay, Orsay, France}

8_{LPNHE, Universit´e Pierre et Marie Curie, Universit´e Paris Diderot, CNRS/IN2P3, Paris, France} 9_{I. Physikalisches Institut, RWTH Aachen University, Aachen, Germany}

10_{Fakult¨at Physik, Technische Universit¨at Dortmund, Dortmund, Germany} 11_{Max-Planck-Institut f¨ur Kernphysik (MPIK), Heidelberg, Germany}

12_{Physikalisches Institut, Ruprecht-Karls-Universit¨at Heidelberg, Heidelberg, Germany} 13_{School of Physics, University College Dublin, Dublin, Ireland}

14_{Sezione INFN di Bari, Bari, Italy} 15_{Sezione INFN di Bologna, Bologna, Italy} 16_{Sezione INFN di Cagliari, Cagliari, Italy} 17_{Universita e INFN, Ferrara, Ferrara, Italy} 18_{Sezione INFN di Firenze, Firenze, Italy}

19_{Laboratori Nazionali dell’INFN di Frascati, Frascati, Italy} 20_{Sezione INFN di Genova, Genova, Italy}

21_{Sezione INFN di Milano Bicocca, Milano, Italy} 22_{Sezione di Milano, Milano, Italy}

23_{Sezione INFN di Padova, Padova, Italy} 24_{Sezione INFN di Pisa, Pisa, Italy}

25_{Sezione INFN di Roma Tor Vergata, Roma, Italy} 26_{Sezione INFN di Roma La Sapienza, Roma, Italy}

27_{Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences, Krak´ow, Poland} 28_{AGH - University of Science and Technology, Faculty of Physics and Applied Computer Science,}

Krak´ow, Poland

29_{National Center for Nuclear Research (NCBJ), Warsaw, Poland}

30_{Horia Hulubei National Institute of Physics and Nuclear Engineering, Bucharest-Magurele, Romania} 31_{Petersburg Nuclear Physics Institute (PNPI), Gatchina, Russia}

32_{Institute of Theoretical and Experimental Physics (ITEP), Moscow, Russia}

33_{Institute of Nuclear Physics, Moscow State University (SINP MSU), Moscow, Russia}

34_{Institute for Nuclear Research of the Russian Academy of Sciences (INR RAS), Moscow, Russia} 35_{Yandex School of Data Analysis, Moscow, Russia}

36_{Budker Institute of Nuclear Physics (SB RAS), Novosibirsk, Russia} 37_{Institute for High Energy Physics (IHEP), Protvino, Russia}

38_{ICCUB, Universitat de Barcelona, Barcelona, Spain}

39_{Instituto Galego de F´ısica de Altas Enerx´ıas (IGFAE), Universidade de Santiago de Compostela,}

Santiago de Compostela, Spain

40_{European Organization for Nuclear Research (CERN), Geneva, Switzerland}

41_{Institute of Physics, Ecole Polytechnique F´ed´erale de Lausanne (EPFL), Lausanne, Switzerland} 42_{Physik-Institut, Universit¨at Z¨urich, Z¨urich, Switzerland}

43_{Nikhef National Institute for Subatomic Physics, Amsterdam, The Netherlands}

44_{Nikhef National Institute for Subatomic Physics and VU University Amsterdam, Amsterdam, The}

Netherlands

45_{NSC Kharkiv Institute of Physics and Technology (NSC KIPT), Kharkiv, Ukraine}

46_{Institute for Nuclear Research of the National Academy of Sciences (KINR), Kyiv, Ukraine} 47_{University of Birmingham, Birmingham, United Kingdom}

48_{H.H. Wills Physics Laboratory, University of Bristol, Bristol, United Kingdom} 49_{Cavendish Laboratory, University of Cambridge, Cambridge, United Kingdom}

50_{Department of Physics, University of Warwick, Coventry, United Kingdom} 51_{STFC Rutherford Appleton Laboratory, Didcot, United Kingdom}

52_{School of Physics and Astronomy, University of Edinburgh, Edinburgh, United Kingdom} 53_{School of Physics and Astronomy, University of Glasgow, Glasgow, United Kingdom} 54_{Oliver Lodge Laboratory, University of Liverpool, Liverpool, United Kingdom} 55_{Imperial College London, London, United Kingdom}

56_{School of Physics and Astronomy, University of Manchester, Manchester, United Kingdom} 57_{Department of Physics, University of Oxford, Oxford, United Kingdom}

58_{Massachusetts Institute of Technology, Cambridge, MA, United States} 59_{University of Cincinnati, Cincinnati, OH, United States}

60_{University of Maryland, College Park, MD, United States} 61_{Syracuse University, Syracuse, NY, United States}

62_{Pontif´ıcia Universidade Cat´olica do Rio de Janeiro (PUC-Rio), Rio de Janeiro, Brazil, associated to}2 63_{University of Chinese Academy of Sciences, Beijing, China, associated to}3

64_{School of Physics and Technology, Wuhan University, Wuhan, China, associated to}3

65_{Institute of Particle Physics, Central China Normal University, Wuhan, Hubei, China, associated to}3 66_{Departamento de Fisica , Universidad Nacional de Colombia, Bogota, Colombia, associated to}8 67_{Institut f¨ur Physik, Universit¨at Rostock, Rostock, Germany, associated to} 12

68_{National Research Centre Kurchatov Institute, Moscow, Russia, associated to}32

69_{National University of Science and Technology MISIS, Moscow, Russia, associated to}32 70_{National Research Tomsk Polytechnic University, Tomsk, Russia, associated to}32

71_{Instituto de Fisica Corpuscular, Centro Mixto Universidad de Valencia - CSIC, Valencia, Spain,}

associated to 38

72_{Van Swinderen Institute, University of Groningen, Groningen, The Netherlands, associated to}43 73_{Los Alamos National Laboratory (LANL), Los Alamos, United States, associated to}61

a_{Universidade Federal do Triˆangulo Mineiro (UFTM), Uberaba-MG, Brazil} b_{Laboratoire Leprince-Ringuet, Palaiseau, France}

c_{P.N. Lebedev Physical Institute, Russian Academy of Science (LPI RAS), Moscow, Russia} d_{Universit`a di Bari, Bari, Italy}

e_{Universit`a di Bologna, Bologna, Italy</sub> f<sub>Universit`a di Cagliari, Cagliari, Italy} g_{Universit`a di Ferrara, Ferrara, Italy</sub> h<sub>Universit`a di Genova, Genova, Italy} i_{Universit`a di Milano Bicocca, Milano, Italy</sub> j<sub>Universit`a di Roma Tor Vergata, Roma, Italy} k_{Universit`a di Roma La Sapienza, Roma, Italy}

l_{AGH - University of Science and Technology, Faculty of Computer Science, Electronics and}

Telecommunications, Krak´ow, Poland

m_{LIFAELS, La Salle, Universitat Ramon Llull, Barcelona, Spain} n_{Hanoi University of Science, Hanoi, Vietnam}

o_{Universit`a di Padova, Padova, Italy</sub> p<sub>Universit`a di Pisa, Pisa, Italy}

q_{Universit`a degli Studi di Milano, Milano, Italy</sub> r<sub>Universit`a di Urbino, Urbino, Italy}

s_{Universit`a della Basilicata, Potenza, Italy} t_{Scuola Normale Superiore, Pisa, Italy}

u_{Universit`a di Modena e Reggio Emilia, Modena, Italy} v_{Iligan Institute of Technology (IIT), Iligan, Philippines} w_{Novosibirsk State University, Novosibirsk, Russia}

x_{National Research University Higher School of Economics, Moscow, Russia} y_{National University of Science and Technology MISIS, Moscow, Russia}