Observation of Structure in the J/Ψ-Pair Mass Spectrum

EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH (CERN)

CERN-EP-2020-115 LHCb-PAPER-2020-011 CERN-EP-2020-115June 30, 2020 22 June 2020

Observation of structure in the J/ψ-pair mass spectrum

LHCb collaboration†

Abstract √ Using proton-proton collision data at centre-of-mass energies of s = 7, 8 and 13 TeV recorded by the LHCb experiment at the Large Hadron Collider, corresponding to an integrated luminosity of 9 fb−1, the invariant mass spectrum of J/ψ pairs is studied. A narrow structure around 6.9 GeV/c2 matching the lineshape of a resonance and a broad structure just above twice the J/ψ mass are observed. The deviation of the data from nonresonant J/ψ-pair production is above ﬁve standard deviations in the mass region between 6.2 and 7.4 GeV/c2, covering predicted masses of states composed of four charm quarks. The mass and natural width of the narrow X(6900) structure are measured assuming a Breit–Wigner lineshape.

Submitted to Science Bulletin c 2020 CERN for the beneﬁt of the LHCb collaboration. CC BY 4.0 licence.

†Authors are listed at the end of this paper. ii 1 1 Introduction

2 The strong interaction is one of the fundamental forces of nature and it governs the

3 dynamics of quarks and gluons. According to quantum chromodynamics (QCD), the

4 theory describing the strong interaction, quarks are conﬁned into hadrons, in agreement

5 with experimental observations. The quark model [1,2] classiﬁes hadrons into conventional

6 mesons (qq) and baryons (qqq or qqq), and also allows for the existence of exotic hadrons

7 such as tetraquarks (qqqq) and pentaquarks (qqqqq). Exotic states provide a unique

8 environment to study the strong interaction and the conﬁnement mechanism [3]. The ﬁrst 9 experimental evidence for an exotic hadron candidate was the χc1(3872) state observed 10 in 2003 by the Belle collaboration [4]. Since then a series of novel states consistent

11 with containing four quarks have been discovered. Recently, the LHCb collaboration

12 observed resonances interpreted to be pentaquark states [5–8]. All hadrons observed to

13 date, including those of exotic nature, contain at most two heavy charm (c) or bottom (b)

14 quarks, whereas many QCD-motivated phenomenological models also predict the existence 15 of states consisting of four heavy quarks, i.e. T , where Qi is a c or a b quark [9–33]. Q1Q2Q3Q4 16 Theoretically, the interpretation of the internal structure of such states usually assumes 17 the formation of a diquark (Q1Q2) and an antidiquark (Q3Q4) attracting each other. 18 Application of this diquark model successfully predicts the mass of the doubly charmed ++ 19 baryon Ξcc [34,35] and helps to explain the relative rates of bottom baryon decays [36]. 20 Tetraquark states comprising only bottom quarks, Tbbbb, have been searched for by the + − 21 LHCb and CMS collaborations in the Υ µ µ decay [37,38], with the Υ state consisting 22 of a bb pair. However, the four-charm states, Tcccc, have not yet been studied in detail 23 experimentally. A Tcccc state could disintegrate into a pair of charmonium states such 24 as J/ψ mesons, with each consisting of a cc pair. Decays to a J/ψ meson plus a heavier

25 charmonium state, or two heavier charmonium states, with the heavier states decaying

26 subsequently into a J/ψ meson and accompanying particles, are also possible. Predictions 2 27 for the masses of Tcccc states vary from 5.8 to 7.4 GeV/c [9–24], which are above the masses 28 of known charmonia and charmonium-like exotic states and below those of bottomonium

29 hadrons. This mass range guarantees a clean experimental environment to identify possible 30 Tcccc states in the J/ψ-pair (also referred to as di-J/ψ) invariant mass (Mdi-J/ψ) spectrum. 31 In proton-proton (pp) collisions, a pair of J/ψ mesons can be produced in two separate

32 interactions of gluons or quarks, named double-parton scattering (DPS) [39–41], or in a

33 single interaction, named single-parton scattering (SPS) [42–49]. The SPS process includes 34 both resonant production via intermediate states, which could be Tcccc tetraquarks, and 35 nonresonant production. Within the DPS process, the two J/ψ mesons are usually

36 assumed to be produced independently, thus the distribution of any di-J/ψ observable can

37 be constructed using the kinematics from single J/ψ production. Evidence of DPS in pp

38 collisions has been found in studies at the Large Hadron Collider (LHC) experiments [50–54]. 39 The LHCb experiment√ has measured the di-J/ψ production in pp collisions at centre-of- 40 mass energies of s = 7 [55] and 13 TeV [56]. The DPS contribution is found to dominate 41 the high Mdi-J/ψ region, in agreement with expectation. 42 In this paper, fully charmed tetraquark states Tcccc are searched for in the di-J/ψ

1 √ 43 invariant mass spectrum, using pp collision data collected by LHCb at s = 7, 8 and −1 44 13 TeV, corresponding to an integrated luminosity of 9 fb . The two J/ψ candidates in + − 45 a pair are reconstructed through the J/ψ → µ µ decay, and are labelled randomly as 46 either J/ψ1 or J/ψ2 .

47 2 Detector and data set

48 The LHCb detector is designed to study particles containing b or c quarks at the LHC. It is

49 a single-arm forward spectrometer covering the pseudorapidity range 2 < η < 5, described

50 in detail in Refs. [57, 58]. The online event selection is performed by a trigger, which

51 consists of a hardware stage, based on information from the calorimeter and muon systems,

52 followed by a software stage, which applies a full event reconstruction. At the hardware

53 stage, events are required to have at least one muon with high momentum transverse to 54 the beamline, pT. At the software stage, two oppositely charged muon candidates are 55 required to have high pT and to form a common vertex. Events are retained if there is 56 at least one J/ψ candidate selected by both the hardware and software trigger stages.

57 Imperfections in the description of the magnetic ﬁeld and misalignment of subdetectors

58 lead to a bias in the momentum measurement of charged particles, which is calibrated + 59 using reconstructed J/ψ and B mesons [59], with well-known masses.

60 Simulated samples are used to model the signal properties, including the invariant

61 mass resolution and the reconstruction efficiency. In the simulation, pp collisions are 62 generated using Pythia [60] with a specific LHCb configuration [61]. Decays of unstable 63 particles are described by EvtGen [62], in which final-state radiation is generated using 64 Photos [63]. The interaction of the generated particles with the detector and its response 65 are implemented using the Geant4 toolkit [64], as described in Ref. [65].

66 3 Candidate selection

67 In the oﬄine selection, two pairs of oppositely charged muon candidate tracks are recon-

68 structed, with each pair forming a vertex of a J/ψ candidate. Each muon track must have 69 pT > 0.65 GeV/c and momentum p > 6 GeV/c. The J/ψ candidates are required to have a 2 70 dimuon invariant mass in the range 3.0 < Mµµ < 3.2 GeV/c . A kinematic ﬁt is performed 71 for each J/ψ candidate constraining its vertex to coincide with a primary pp collision

72 vertex (PV) [66]. The requirement of a good kinematic ﬁt quality strongly suppresses

73 the contamination of di-J/ψ candidates stemming from feed-down of b-hadrons, which

74 decay at displaced vertices. The four muon tracks in a J/ψ-pair candidate are required to

75 originate from the same PV, reducing to a negligible level the number of pile-up candidates

76 with the two J/ψ candidates produced in separated pp collisions. Fake di-J/ψ candidates,

77 comprising two muon-track candidates reconstructed from the same real particle, are

78 rejected by requiring muons of the same charge to have trajectories separated by an angle

79 inconsistent with zero. For events with more than one reconstructed di-J/ψ candidate,

80 accounting for about 0.8% of the total sample, only one pair is randomly chosen.

2 ) 2 c 3000 Data LHCb Total fit 2500 J/ψ +J/ψ 1 2 bkg +J/ψ 1 2 2000 J/ψ +bkg 1 2 bkg +bkg 1500 1 2

Candidates / (2 MeV/ 1000

500

0 ] 3200 2 2 ) 2 250 [MeV/c µ 3150

(1) µ 200 M

150 3100 Candidates/(5 MeV/c 100

3050 50

3000

0 3000 3050 3100 3150 3200 500

3000 2500 2000 1500 1000 (2) 2 Candidates / (2 MeV/c2) M µµ [MeV/c ]

(1) (2) Figure 1: (Bottom right) Two-dimensional (Mµµ ,Mµµ ) distribution of di-J/ψ candidates and its (1) (2) projections on (bottom left) Mµµ and (top) Mµµ . Four components are present as each projection consists of signal and background J/ψ candidates. The labels J/ψ1,2 and bkg1,2 represent the (1),(2) signal and background contributions, respectively, in the Mµµ distribution.

81 The di-J/ψ signal yield is extracted by performing an extended unbinned maximum- 82 likelihood ﬁt to the two-dimensional distribution of J/ψ1 and J/ψ2 invariant masses, (1) (2) 83 (Mµµ ,Mµµ ), as displayed in Fig. 1, where projections of the data and the ﬁt result are 84 shown. For both J/ψ candidates, the signal mass shape is modelled by a Gaussian kernel

85 with power-law tails [67]. Each component of combinatorial background, consisting of

86 random combinations of muon tracks, is described by an exponential function. The 3 87 total di-J/ψ signal yield is measured to be (33.57 ± 0.23) × 10 , where the uncertainty is

88 statistical. di-J/ψ 89 The di-J/ψ transverse momentum (pT ) in SPS production is expected to be, on di-J/ψ 90 average, higher than that in DPS [48]. The high-pT region is thus exploited to

3 91 select a data sample with enhanced SPS production, which could include contributions 92 from Tcccc states. Two different approaches are applied. In the first approach (denoted di-J/ψ di-J/ψ 93 as pT -threshold), J/ψ-pair candidates are selected with the requirement pT > 94 5.2 GeV/c, which maximises the statistical significance of the SPS signal yield. In the di-J/ψ 95 second approach (denoted as pT -binned), di-J/ψ candidates are categorised into six di-J/ψ 96 pT intervals with boundaries {0, 5, 6, 8, 9.5, 12, 50} GeV/c, defined to obtain equally 2 97 populated bins of SPS signal events in the Mdi-J/ψ range between 6.2 and 7.4 GeV/c . This 98 mass region covers the predicted masses of Tcccc states decaying into a J/ψ pair. For both 99 scenarios, the DPS yield in the Tcccc signal region is extrapolated from the high-Mdi-J/ψ 100 region using the wide-range distribution constructed from available double-differential 101 J/ψ cross-sections [68–70]. The high-Mdi-J/ψ region is chosen such that the SPS yield is 102 negligible compared to DPS. The SPS yield is obtained by subtracting the DPS contribution

103 from the total number of J/ψ-pair signals. di-J/ψ 104 The Mdi-J/ψ distribution for candidates with pT > 5.2 GeV/c and (1),(2) 2 105 3.065 < Mµµ < 3.135 GeV/c is shown in Fig. 2. The di-J/ψ mass is calculated 106 by constraining the reconstructed mass of each J/ψ candidate to its known value [71].

107 The spectrum shows a broad structure just above twice the J/ψ mass threshold ranging 2 108 from 6.2 to 6.8 GeV/c (dubbed threshold enhancement in the following) and a narrower 2 109 structure at about 6.9 GeV/c , referred to hereafter as X(6900). There is also a hint of 2 110 another structure around 7.2 GeV/c , whereas there are no evident structures at higher

111 invariant mass. Several cross-checks are performed to investigate the origin of these

112 structures and to exclude that they are experimental artifacts. The threshold enhancement di-J/ψ 113 and the X(6900) structure become more pronounced in higher pT intervals, and they 114 are present in subsamples split according to diﬀerent beam or detector conﬁgurations

115 for data collection. The structures are not caused by the experimental eﬃciency, since 116 the eﬃciency variation across the whole Mdi-J/ψ range is found to be marginal. Residual 117 background, in which a muon track is reused or at least one J/ψ candidate is produced

118 from a b-hadron decay, is observed to have no structure. The possible contribution of J/ψ 119 pairs from Υ decays is estimated to be negligible and distributed uniformly in the Mdi-J/ψ (1),(2) 120 distribution. In Fig. 2, the Mdi-J/ψ distribution for background pairs with Mµµ in the 2 2 121 range 3.00 − 3.05 GeV/c or 3.15 − 3.20 GeV/c is also shown, with the yield normalised by

122 interpolating the background into the J/ψ signal region, which accounts for around 15% 123 of the total candidates. There is no evidence of structures in the Mdi-J/ψ distribution of 124 background candidates.

125 4 Investigation of the J/ψ-pair invariant mass spec-

126 trum

127 To remove background pairs that have at least one background J/ψ candidate, the sPlot

128 weighting method [72] is applied, where the weights are calculated from the ﬁt to the (1) (2) 129 two-dimensional (Mµµ ,Mµµ ) distribution. The background-subtracted di-J/ψ spectra in

4 ) 2

c 220 LHCb p di-J/ψ > 5.2 GeV/c 200 T 180 3.065 < Mµ µ < 3.135 GeV/c2 160 3.00 < Mµ µ < 3.05 GeV/c2 or 140 3.15 < Mµ µ < 3.20 GeV/c2, normalised 120 100 80 60

Candidates/(28 MeV/ 40 20 0 7000 8000 9000 2 Mdi-J/ψ [MeV/c ]

di-J/ψ Figure 2: Invariant mass spectrum of J/ψ-pair candidates passing the pT > 5.2 GeV/c requirement with reconstructed J/ψ masses in the (black) signal and (blue) background regions, respectively.

2 di-J/ψ 130 the range 6.2 < Mdi-J/ψ < 9.0 GeV/c are shown in Fig. 3 for candidates with pT > di-J/ψ 131 5.2 GeV/c and Fig. 4 for candidates in the six pT intervals, which are investigated 132 by weighted unbinned maximum-likelihood ﬁts [73]. The Mdi-J/ψ distribution of signal 133 events is expected to be dominated by the sum of the nonresonant SPS (NRSPS) and

134 DPS production, which have smooth shapes (referred to as continuum in the following).

135 The DPS continuum is described by an empirical function and its yield determined 2 136 by extrapolation from the Mdi-J/ψ > 12 GeV/c region, which is dominated and well 137 described by the DPS distribution. The continuum NRSPS is modelled by a two-body

138 phase-space distribution multiplied by an exponential function determined from the data.

139 The combination of continuum NRSPS and DPS does not provide a good description 140 of the data, as is illustrated in Fig. 3(a). The Mdi-J/ψ spectrum in the data is tested 141 against the hypothesis that only NRSPS and DPS components are present in the range 2 2 142 6.2 < Mdi-J/ψ < 7.4 GeV/c (null hypothesis) using a χ test statistic. Pseudoexperiments 143 are generated and fitted according to the null hypothesis, and the fraction of these fits 2 144 with a χ value exceeding that in the data is converted into a significance. Considering the di-J/ψ 145 sample in the pT > 5.2 GeV/c region, the null hypothesis is inconsistent with the data 146 at 3.4 standard deviations (σ). A test performed simultaneously in the aforementioned di-J/ψ 147 six pT regions yields a discrepancy of 6.0 σ with the null hypothesis. A higher value di-J/ψ 148 is obtained in the latter case as more detailed information on the pT distribution is 149 exploited. 150 The structures in the Mdi-J/ψ distribution can have various interpretations. There may 151 be one or more resonant states Tcccc decaying directly into a pair of J/ψ mesons, or Tcccc 152 states decaying into a pair of J/ψ mesons through feed-down of heavier quarkonia, for 153 example Tcccc → χc(→ J/ψγ)J/ψ where the photon escapes detection. In the latter case,

5 154 such a state would be expected to peak at a lower Mdi-J/ψ position, close to the di-J/ψ mass 155 threshold, and its structure would be broader compared to that from a direct decay. This

156 feed-down is unlikely an explanation for the narrow X(6900) structure. Rescattering of

157 two charmonium states produced by SPS close to their mass threshold may also generate

158 a narrow structure [74–77]. The two thresholds close to the X(6900) structure could be 2 2 159 formed by χc0χc0 pairs at 6829.4 MeV/c and χc1χc0 pairs at 6925.4 MeV/c , respectively. 160 Whereas a resonance is often described by a relativistic Breit–Wigner (BW) function [71],

161 the lineshape of a structure with rescattering eﬀects taken into account is more complex. In

162 principle, resonant production can interfere with NRSPS of the same spin-parity quantum PC 163 numbers (J ), resulting in a coherent sum of the two components and thus a modiﬁcation 164 of the total Mdi-J/ψ distribution. 165 Two diﬀerent models of the structure lineshape providing a reasonable description of

166 the data are investigated. The X(6900) lineshape parameters and yields are derived from di-J/ψ di-J/ψ 167 fits to the pT -threshold sample. Simultaneous pT -binned fits are also performed 168 as a cross-check and the variation of lineshape parameters is considered as a source of 2 169 systematic uncertainties. Due to its low significance, the structure around 7.2 GeV/c has

170 been neglected.

171 In model I, the X(6900) structure is considered as a resonance, whereas the threshold

172 enhancement is described through a superposition of two resonances. The lineshapes of

173 these resonances are described by S-wave relativistic BW functions multiplied by a two-body 2 174 phase-space distribution. The experimental resolution on Mdi-J/ψ is below 5 MeV/c over the 175 full mass range and negligible compared to the widths of the structures. The projections of di-J/ψ 176 the pT -threshold fit using this model are shown in Fig. 3(b). The mass, natural width and 2 177 yield are determined to be m[X(6900)] = 6905 ± 11 MeV/c , Γ[X(6900)] = 80 ± 19 MeV 178 and Nsig = 252 ± 63, where biases on the statistical uncertainties have been corrected 2 179 using a bootstrap method [78]. The goodness of fit is studied using a χ test statistic and 2 180 found to be χ /ndof = 112.7/89, corresponding to a probability of 4.6%. The fit is also

181 performed assuming the threshold enhancement as due to a single wide resonance (see

182 Supplementary Material); the ﬁt quality is found signiﬁcantly poorer and thus this model

183 is not further investigated.

184 A comparison between the best ﬁt result of model I and the data reveals a tension 2 185 around 6.75 GeV/c , where the data shows a dip. In an attempt to describe the dip, model

186 II allows for interference between the NRSPS component and a resonance for the threshold

187 enhancement. The coherent sum of the two components is deﬁned as q 2 iφ Ae fnr(Mdi-J/ψ) + BW(Mdi-J/ψ) , (1)

188 where A and φ are the magnitude and phase of the nonresonant component, relative to the 189 BW lineshape for the resonance, assumed to be independent of Mdi-J/ψ, and fnr(Mdi-J/ψ) is 190 an exponential function. The interference term in Eq. (1) is then added incoherently to

191 the BW function describing the X(6900) structure and the DPS description. The ﬁt to the di-J/ψ 2 192 pT -threshold sample with this model has a probability of 15.5% (χ /ndf = 104.7/91), 193 and its projections are illustrated in Fig. 3(c). In this case, the mass, natural width and

6 ) 220 2 c Data 200 LHCb 180 Total fit 160 DPS 140 NRSPS 120 100 80 60 40 20

Weighted Candidates / (28 MeV/ 0 7000 8000 9000 2 Mdi-J/ψ [MeV/c ] (a)

) 220 ) 220 2 2 c 200 Data c 200 Data LHCb Total fit LHCb Total fit 180 Resonance 180 Resonance Threshold BW1 Interference 160 Threshold BW2 160 Interference BW DPS 140 140 DPS NRSPS 120 DPS+NRSPS 120 NRSPS 100 100 80 80 60 60 40 40 20 20

Weighted Candidates / (28 MeV/ 0 Weighted Candidates / (28 MeV/ 0 7000 8000 9000 7000 8000 9000 2 2 Mdi-J/ψ [MeV/c ] Mdi-J/ψ [MeV/c ] (b) (c)

di-J/ψ Figure 3: Invariant mass spectra of weighted di-J/ψ candidates with pT > 5.2 GeV/c and di-J/ψ overlaid projections of the pT -threshold ﬁt using (a) the NRSPS plus DPS model, (b) model I, and (c) model II.

2 194 yield are determined to be m[X(6900)] = 6886 ± 11 MeV/c , Γ[X(6900)] = 168 ± 33 MeV 195 and Nsig = 784 ± 148. A larger X(6900) width and yield are preferred in comparison 196 to model I. Here it is assumed that the whole NRSPS production is involved in the

197 interference with the lower-mass resonance despite that there may be several components

198 with diﬀerent quantum numbers in the NRSPS and more than one resonance in the

199 threshold enhancement. di-J/ψ 200 Fits to the Mdi-J/ψ distributions in the six individual pT bins are shown in Fig. 4 201 for model I, while those for model II are given in the Supplementary Material. An

202 additional model describing the dip and the X(6900) structure simultaneously by using the 2 203 interference between the NRSPS and a BW resonance around 6.9 GeV/c is also considered,

204 however the ﬁt quality is signiﬁcantly poorer, as illustrated in the Supplementary Material.

205 Alternative lineshapes, other than the BW, may also be possible to describe these structures

206 and will be the subject of future studies.

207 The increase of the likelihood between the ﬁts with or without considering the X(6900)

7 ) ) 2 900 2 c c Data 100 5.0 < p di-J/ψ < 6.0 GeV/c 800 LHCb Total fit T 700 p di-J/ψ < 5.0 GeV/c Resonance T Threshold BW1 80 600 Threshold BW2 DPS 500 NRSPS 60 400 DPS+NRSPS 300 40 200 20 100

Weighted Candidates / (56 MeV/ 0 Weighted Candidates / (56 MeV/ 0 7000 8000 9000 7000 8000 9000 2 2 Mdi-J/ψ [MeV/c ] Mdi-J/ψ [MeV/c ] (a) (b) ) ) 2 2

c c 70 140 6.0 < p di-J/ψ < 8.0 GeV/c 8.0 < p di-J/ψ < 9.5 GeV/c T 60 T 120 50 100 80 40 60 30 40 20 20 10

Weighted Candidates / (56 MeV/ 0 Weighted Candidates / (56 MeV/ 0 7000 8000 9000 7000 8000 9000 2 2 Mdi-J/ψ [MeV/c ] Mdi-J/ψ [MeV/c ] (c) (d) ) ) 2 2

c c 80 ψ ψ 60 9.5 < pdi-J/ < 12.0 GeV/c 12.0 < pdi-J/ < 50.0 GeV/c T 70 T 50 60 40 50

30 40 30 20 20 10 10

Weighted Candidates / (56 MeV/ 0 Weighted Candidates / (56 MeV/ 0 7000 8000 9000 7000 8000 9000 2 2 Mdi-J/ψ [MeV/c ] Mdi-J/ψ [MeV/c ] (e) (f)

di-J/ψ Figure 4: Invariant mass spectra of weighted di-J/ψ candidates in bins of pT and overlaid di-J/ψ projections of the pT -binned ﬁt with model I.

208 and the threshold enhancement structures on top of the continuum NRSPS plus DPS

209 model is used to calculate the combined global signiﬁcance of the two structures [79] in the 2 210 6.2 < Mdi-J/ψ < 7.4 GeV/c region. Only model I is studied, where the interference between 211 the NRSPS and the threshold enhancement is not included. Similarly, the signiﬁcance for

212 each individual structure is evaluated assuming the presence of the other along with the

8 Table 1: Signiﬁcance evaluated under the various assumptions described in the text.

Signiﬁcance Structure di-J/ψ di-J/ψ pT -threshold pT -binned Any structure beyond NRSPS plus DPS 3.4 σ 6.0 σ Threshold enhancement plus X(6900) 6.4 σ 6.9 σ Threshold enhancement 6.0 σ 6.5 σ X(6900) 5.1 σ 5.4 σ

Table 2: Systematic uncertainties on the mass (m) and natural width (Γ) of the X(6900) structure.

Without interference With interference Component m [ MeV/c2] Γ [ MeV] m [ MeV/c2] Γ [ MeV] sPlot weights 0.8 10.3 4.4 36.9 Experimental resolution 0.0 1.4 0.0 0.6 NRSPS+DPS modelling 0.8 16.1 3.5 9.3 X(6900) shape 0.0 0.3 0.4 0.2 di-J/ψ Cut on pT 4.6 13.5 6.2 56.7 b-hadron feed-down 0.0 0.2 0.0 5.3 Structure at 7.2 GeV/c2 1.3 9.2 6.7 5.2 Threshold structure shape 5.2 20.5 –– NRSPS phase –– 0.3 1.3 Total 7 33 11 69

di-J/ψ 213 NRSPS and DPS continuum. The significance is determined from both pT -threshold di-J/ψ 214 and pT -binned fits, and summarised in Table 1. The results are above 5 σ for the two di-J/ψ 215 structures, with slightly higher significance for the pT -binned case. 216 Systematic uncertainties on the measurements of the mass and natural width of the

217 X(6900) structure are reported in Table 2. They include variations of the results obtained 218 by: including an explicit component in the Mdi-J/ψ ﬁts for the J/ψ combinatorial background 219 rather than subtracting it using the weighting method (sPlot weights in Table 2); convolving 2 220 the Mdi-J/ψ ﬁt functions with a Gaussian function of 5 MeV/c width to account for the 221 invariant mass resolution (Experimental resolution); modelling the threshold structure

222 using an alternative Gaussian function with asymmetric power-law tails, or ﬁtting in a 223 reduced Mdi-J/ψ range excluding the threshold structure (Threshold structure shape); using 224 alternative functions to describe the NRSPS component and varying the DPS yield (NRSPS

9 225 plus DPS modelling); allowing the relative phase in the NRSPS component to vary linearly 226 with Mdi-J/ψ (NRSPS phase) using an alternative P -wave BW function for the X(6900) −1 227 structure and varying the hadron radius in the BW function from 2 to 5 GeV [X(6900) 228 shape]; obtaining results from a simultaneous ﬁt to the Mdi-J/ψ distributions in the six di-J/ψ di-J/ψ 229 pT bins (Cut on pT ); including an explicit contribution for J/ψ mesons from b-hadron 2 230 feed-down (b-hadron feed-down) or adding a BW component for the 7.2 GeV/c structure 2 2 231 (Structure at 7.2 GeV/c ). The total uncertainties are determined to be 7 MeV/c and

232 33 MeV for the mass and natural width, respectively, without considering any interference, 2 233 and 11 MeV/c and 69 MeV when the interference between NRSPS and the threshold

234 structure is introduced.

235 For the scenario without interference, the production cross-section of the X(6900) 236 structure relative to that of all J/ψ pairs (inclusive), times the√ branching fraction 237 B(X(6900) → J/ψJ/ψ), R, is determined in the pp collision data at s = 13 TeV. The mea-

238 surement is obtained for both J/ψ mesons in the ﬁducial region of transverse momentum

239 below 10 GeV/c and rapidity between 2.0 and 4.5. An event-by-event eﬃciency correction

240 is performed to obtain the signal yield at production. The residual contamination from

241 b-hadron feed-down is subtracted from inclusive J/ψ-pair production following Ref. [70].

242 The systematic uncertainties on the X(6900) yield are estimated in a similar way to that

243 for the mass and natural width, while other systematic uncertainties mostly cancel in the

244 ratio. The production ratio is measured to be R = [1.1 ± 0.4 (stat) ± 0.3 (syst)]% without di-J/ψ di-J/ψ 245 any pT requirement and R = [2.6 ± 0.6 (stat) ± 0.8 (syst)]% for pT > 5.2 GeV/c.

246 5 Summary

247 In conclusion, using pp collision data at centre-of-mass energies of 7, 8 and 13 TeV collected −1 248 with the LHCb detector, corresponding to an integrated luminosity of 9 fb , the J/ψ-pair 2 249 invariant mass spectrum is studied. The data in the mass range between 6.2 and 7.4 GeV/c

250 are found to be inconsistent with the hypothesis of NRSPS plus DPS continuum. A narrow

251 structure, X(6900), matching the lineshape of a resonance and a broad structure next to

252 the di-J/ψ mass threshold are found. The global signiﬁcance of either the broad or the

253 X(6900) structure is determined to be larger than ﬁve standard deviations. Describing

254 the X(6900) structure with a Breit–Wigner lineshape, its mass and natural width are

255 determined to be m[X(6900)] = 6905 ± 11 ± 7 MeV/c2

256 and Γ[X(6900)] = 80 ± 19 ± 33 MeV,

257 assuming no interference with the NRSPS continuum is present, where the ﬁrst uncertainty

258 is statistical and the second systematic. When assuming the NRSPS continuum interferes

259 with the broad structure close to the di-J/ψ mass threshold, they become

m[X(6900)] = 6886 ± 11 ± 11 MeV/c2

10 260 and Γ[X(6900)] = 168 ± 33 ± 69 MeV.

261 The X(6900) structure could originate from a hadron state consisting of four charm quarks, 262 Tcccc, predicted in various tetraquark models. The broad structure close to the di-J/ψ mass 263 threshold could be due to a mixture of multiple four-charm states or have contributions

264 from feed-down of four-charm states through heavier quarkonia. Other interpretations

265 cannot presently be ruled out, for example the rescattering of two charmonium states

266 produced close to their mass threshold. More data along with additional measurements, 267 including determination of the spin-parity quantum numbers and pT dependence of the 268 production cross-section, are needed to provide further information about the nature of

269 the observed structure.

270 Acknowledgements

271 We express our gratitude to our colleagues in the CERN accelerator departments for the

272 excellent performance of the LHC. We thank the technical and administrative staﬀ at the

273 LHCb institutes. We acknowledge support from CERN and from the national agencies:

274 CAPES, CNPq, FAPERJ and FINEP (Brazil); MOST and NSFC (China); CNRS/IN2P3

275 (France); BMBF, DFG and MPG (Germany); INFN (Italy); NWO (Netherlands); MNiSW

276 and NCN (Poland); MEN/IFA (Romania); MSHE (Russia); MinECo (Spain); SNSF and

277 SER (Switzerland); NASU (Ukraine); STFC (United Kingdom); DOE NP and NSF (USA).

278 We acknowledge the computing resources that are provided by CERN, IN2P3 (France), KIT

279 and DESY (Germany), INFN (Italy), SURF (Netherlands), PIC (Spain), GridPP (United

280 Kingdom), RRCKI and Yandex LLC (Russia), CSCS (Switzerland), IFIN-HH (Romania),

281 CBPF (Brazil), PL-GRID (Poland) and OSC (USA). We are indebted to the communities

282 behind the multiple open-source software packages on which we depend. Individual groups

283 or members have received support from AvH Foundation (Germany); EPLANET, Marie

284 Sk lodowska-Curie Actions and ERC (European Union); A*MIDEX, ANR, Labex P2IO

285 and OCEVU, and R´egionAuvergne-Rhˆone-Alpes (France); Key Research Program of

286 Frontier Sciences of CAS, CAS PIFI, and the Thousand Talents Program (China); RFBR,

287 RSF and Yandex LLC (Russia); GVA, XuntaGal and GENCAT (Spain); the Royal Society

288 and the Leverhulme Trust (United Kingdom).

11 289 Justiﬁcation

290 The study of exotic hadrons is an important route to gain insight into the strong interaction.

291 Exotic hadronic states observed so far all contain no more than two heavy quarks. Fully

292 heavy tetraquark states are predicted to be candidates of compactly bound exotic states,

293 providing a unique laboratory to investigate the mechanism of multiquark interactions.

294 This paper presents the study of J/ψ-pair mass spectrum using the full LHCb data. New

295 structures consistent with tetraquark states composed of four charm quarks are observed

296 with high statistical signiﬁcance. This is the ﬁrst observation of structures likely to be 297 four-charm tetraquark states, Tcccc.

298 Description of the LHCb experiment

299 LHCb is one of the four big experiments located on the most powerful particle accelerator

300 in the world, the Larger Hadron Collider (LHC) at CERN. The LHCb detector includes

301 a high-precision tracking system, particle identiﬁcation detectors, electromagnetic and

302 hadronic calorimeters and muon detectors, that record particles produced in proton-proton

303 or heavy-ion collisions with a center-of-mass energy up to 13 TeV. The LHCb experiment

304 aims at studies of ﬂavor physics and QCD through precision measurements of particles

305 containing charm or beauty quarks, in order to answer fundamental questions in particle

306 physics, for example the origin of the asymmetry between matter and anti-matter and how

307 does the strong interaction behaves at both high and low energies. The LHCb collaboration

308 consists of more than 1400 members from 19 countries in 6 continents, including both

309 physicists and engineers.

310 Word count

311 This paper contains 23479 characters and 3759 words.

312 Figures: Add 20+150/(aspect ratio) per ﬁgure (120*4=480)

313 Equations: Add 16 words per row (single column) (16)

314 Tables: Add 13 words plus 6.5 words per line (single column) (13+6.5*10+13+6.5*6=130)

315 In total there are 4369 words.

12 316 Supplementary Material

di-J/ψ 317 In the Supplementary Material, the J/ψ-pair mass distributions in bins of pT are shown 318 in Sec. A, the ﬁts using several additional models to the J/ψ-pair mass spectrum are

319 presented in Sec. B, and some supplemental information to the ﬁt result of model II is

320 given in Sec. C.

di-J/ψ 321 A J/ψ-pair mass distributions in bins of pT ) ) )

2 2 2 160 c c c 900 LHCb p di-J/ψ < 5.0 GeV/c 100 5.0 < p di-J/ψ < 6.0 GeV/c 6.0 < p di-J/ψ < 8.0 GeV/c T T 140 T

2 800 3.065 < M µ µ < 3.135 GeV/c

2 120 700 3.00 < M µ µ < 3.05 GeV/c or 80

2 600 3.15 < M µ µ < 3.20 GeV/c , normalised 100 60 500 80 400 40 60 300 40 Candidates/(56 MeV/ 200 Candidates/(56 MeV/ 20 Candidates/(56 MeV/ 100 20 0 0 0 7000 8000 9000 7000 8000 9000 7000 8000 9000 2 2 2 M di-J/ψ [MeV/c ] M di-J/ψ [MeV/c ] M di-J/ψ [MeV/c ]

) 70 ) ) 2 2 60 2 c c c 8.0 < p di-J/ψ < 9.5 GeV/c 9.5 < p di-J/ψ < 12.0 GeV/c 70 12.0 < p di-J/ψ < 50.0 GeV/c 60 T T T 50 60 50 40 50 40 30 40 30 30 20 20 20 Candidates/(56 MeV/ Candidates/(56 MeV/ Candidates/(56 MeV/ 10 10 10 0 0 0 7000 8000 9000 7000 8000 9000 7000 8000 9000 2 2 2 M di-J/ψ [MeV/c ] M di-J/ψ [MeV/c ] M di-J/ψ [MeV/c ]

di-J/ψ Figure 5: Invariant mass spectra of J/ψ-pair candidates in the six pT regions with boundaries {0, 5, 6, 8, 9.5, 12, 50} GeV/c with reconstructed J/ψ masses in the (black) signal and (blue) background regions, respectively.

322 B Additional ﬁts to the J/ψ-pair mass spectrum

323 Figure 6 shows the ﬁts to the J/ψ-pair mass spectrum with (a) the threshold structure

324 described by a single Breit–Wigner (BW) lineshape and (b) using a model that contains

13 2 325 a single BW resonance interfering with the SPS continuum. The χ /ndof of the two ﬁts

326 are 125.6/92 and 118.6/91, corresponding to a probability of 1.2% and 2.8%, respectively. 2 327 Figure 7 shows the ﬁt with an additional BW function introduced to describe the 7.2 GeV/c

328 structure, based on the model that contains two BW lineshapes for the threshold structure

329 and a BW shape for the X(6900) structure on top of the NRSPS plus DPS continuum.

) 220 ) 220 2 2

c Data c Data 200 Total fit 200 LHCb LHCb Total fit 180 Resonance 180 Threshold BW Interference 160 160 DPS Interference BW 140 NRSPS 140 DPS+NRSPS DPS 120 120 NRSPS 100 100 80 80 60 60 40 40 20 20

Weighted Candidates / (28 MeV/ 0 Weighted Candidates / (28 MeV/ 0 7000 8000 9000 7000 8000 9000 2 2 Mdi-J/ψ [MeV/c ] Mdi-J/ψ [MeV/c ] (a) (b)

di-J/ψ Figure 6: Invariant mass spectra of weighted di-J/ψ candidates with pT > 5.2 GeV/c and di-J/ψ overlaid projections of the pT -threshold ﬁt with (a) the threshold structure described as a single BW function, and (b) assuming a single BW interfering with the SPS continuum.

) 220 2 c 200 Data LHCb Total fit 180 Resonance 1 Threshold BW1 160 Threshold BW2 Resonance 2 140 DPS NRSPS 120 DPS+NRSPS 100 80 60 40 20

Weighted Candidates / (28 MeV/ 0 7000 8000 9000 2 Mdi-J/ψ [MeV/c ]

di-J/ψ Figure 7: Invariant mass spectra of weighted di-J/ψ candidates with pT > 5.2 GeV/c and di-J/ψ overlaid projections of the pT -threshold ﬁt with an additional BW function introduced to describe the 7.2 GeV/c2 structure, based on the model that contains two BW lineshapes for the threshold structure and a BW shape for the X(6900) structure on top of the NRSPS plus DPS continuum.

14 330 C Supplement to ﬁt result of model II

331 In model II that contains a BW lineshape for the threshold structure interfering with the

332 NRSPS, a BW shape for the X(6900) structure and the DPS continuum, the parameters 2 333 of the lower-mass BW lineshape is determined to M = 6741 ± 6 (stat) MeV/c and Γ =

334 288 ± 16 (stat) MeV. The systematic uncertainties on the mass and natural width are not

335 studied. Due to the complex nature of the threshold structure, and the simple interference

336 scenario considered, this study is not considered to claim a state with the parameters

337 reported here. di-J/ψ 338 Projections of the ﬁt to the J/ψ-pair invariant mass spectra in bins of pT assuming 339 the interference between the threshold structure and the SPS continuum are shown in

340 Fig. 8.

15 ) ) 2 900 2 c c Data ψ 800 LHCb 100 5.0 < p di-J/ < 6.0 GeV/c Total fit T ψ 700 p di-J/ < 5.0 GeV/c Resonance T 80 600 Interference Interference BW 500 DPS 60 400 NRSPS 300 40 200 20 100

Weighted Candidates / (56 MeV/ 0 Weighted Candidates / (56 MeV/ 0 7000 8000 9000 7000 8000 9000 2 2 Mdi-J/ψ [MeV/c ] Mdi-J/ψ [MeV/c ] (a) (b) ) ) 2 2

c c 70 140 6.0 < p di-J/ψ < 8.0 GeV/c 8.0 < p di-J/ψ < 9.5 GeV/c T 60 T 120 50 100 80 40 60 30 40 20 20 10

Weighted Candidates / (56 MeV/ 0 Weighted Candidates / (56 MeV/ 0 7000 8000 9000 7000 8000 9000 2 2 Mdi-J/ψ [MeV/c ] Mdi-J/ψ [MeV/c ] (c) (d) ) ) 2 2

c c 80 ψ ψ 60 9.5 < pdi-J/ < 12.0 GeV/c 12.0 < pdi-J/ < 50.0 GeV/c T 70 T 50 60 40 50 30 40 30 20 20 10 10

Weighted Candidates / (56 MeV/ 0 Weighted Candidates / (56 MeV/ 0 7000 8000 9000 7000 8000 9000 2 2 Mdi-J/ψ [MeV/c ] Mdi-J/ψ [MeV/c ] (e) (f)

di-J/ψ Figure 8: Invariant mass spectra of weighted di-/J/ψ candidates in bins of pT and overlaid di-J/ψ projections of the pT -binned ﬁt assuming that the threshold structure interferes with the SPS continuum.

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22 LHCb collaboration

31 49 59 45 53 9 513 R. Aaij , C. AbellánBeteta , T. Ackernley , B. Adeva , M. Adinolfi , H. Afsharnia , 82 25 9 64 14 47 58 514 C.A. Aidala , S. Aiola , Z. Ajaltouni , S. Akar , J. Albrecht , F. Alessio , M. Alexander , 44 61 37 47 45 515 A. Alfonso Albero , Z. Aliouche , G. Alkhazov , P. Alvarez Cartelle , A.A. Alves Jr , 2 11 21 21 48 37 516 S. Amato , Y. Amhis , L. An , L. Anderlini , G. Andreassi , A. Andreianov , 20 16 43 67 41 10 517 M. Andreotti , F. Archilli , A. Artamonov , M. Artuso , K. Arzymatov , E. Aslanides , 49 11 16 48 55 60 518 M. Atzeni , B. Audurier , S. Bachmann , M. Bachmayer , J.J. Back , S. Baker , 45 11,b 20 1 61 519 P. Baladron Rodriguez , V. Balagura , W. Baldini , J. Baptista Leite , R.J. Barlow , 11 60 23,47,h 79 13 28 520 S. Barsuk , W. Barter , M. Bartolini , F. Baryshnikov , J.M. Basels , G. Bassi , 35 67 14 48 14 28 1 521 V. Batozskaya , B. Batsukh , A. Battig , A. Bay , M. Becker , F. Bedeschi , I. Bediaga , 67 41 26 48 43 38 22 522 A. Beiter , V. Belavin , S. Belin , V. Bellee , K. Belous , I. Belyaev , G. Bencivenni , 12 39 49 16 67 47 523 E. Ben-Haim , A. Berezhnoy , R. Bernet , D. Berninghoff , H.C. Bernstein , C. Bertella , 12 27 49 19,e 54 49 524 E. Bertholet , A. Bertolin , C. Betancourt , F. Betti , M.O. Bettler , Ia. Bezshyiko , 53 33 72 14 52 12 60 525 S. Bhasin , J. Bhom , L. Bian , M.S. Bieker , S. Bifani , P. Billoir , M. Birch , 54 21,t 62 47 55 48 67 526 F.C.R. Bishop , A. Bizzeti , M. Bjørn , M.P. Blago , T. Blake , F. Blanc , S. Blusk , 58 30 14 45 63 80 527 D. Bobulska , V. Bocci , J.A. Boelhauve , O. Boente Garcia , T. Boettcher , A. Boldyrev , 42,w 37,47 61 41 16 33 528 A. Bondar , N. Bondar , S. Borghi , M. Borisyak , M. Borsato , J.T. Borsuk , 48 59 47 20 60 65 529 S.A. Bouchiba , T.J.V. Bowcock , A. Boyer , C. Bozzi , M.J. Bradley , S. Braun , 45 47 33 55 26 530 A. Brea Rodriguez , M. Brodski , J. Brodzicka , A. Brossa Gonzalo , D. Brundu , 53 49 47 26 40 31 531 E. Buchanan , A. Buonaura , C. Burr , A. Bursche , A. Butkevich , J.S. Butter , 47 47 26 72 20,g 22 532 J. Buytaert , W. Byczynski , S. Cadeddu , H. Cai , R. Calabrese , L. Calero Diaz , 22 52 24,i 44,l 53 533 S. Cali , R. Calladine , M. Calvi , M. Calvo Gomez , P. Camargo Magalhaes , 44 22 47 5 534 A. Camboni , P. Campana , D.H. Campora Perez , A.F. Campoverde Quezada , 24,i 19,e 19,e 29 23,h 26 535 S. Capelli , L. Capriotti , A. Carbone , G. Carboni , R. Cardinale , A. Cardini , 6 24,i 31 45 59 47 536 I. Carli , P. Carniti , K. Carvalho Akiba , A. Casais Vidal , G. Casse , M. Cattaneo , 47 48 28 10 59 53 537 G. Cavallero , S. Celani , R. Cenci , J. Cerasoli , A.J. Chadwick , M.G. Chapman , 12 47 52 8 3 538 M. Charles , Ph. Charpentier , G. Chatzikonstantinidis , M. Chefdeville , C. Chen , 26 33 47 45 48 33 539 S. Chen , A. Chernov , S.-G. Chitic , V. Chobanova , S. Cholak , M. Chrzaszcz , 37 37 22 55 45 47 540 A. Chubykin , V. Chulikov , P. Ciambrone , M.F. Cicala , X. Cid Vidal , G. Ciezarek , 19 57 47 54 47 61 541 F. Cindolo , P.E.L. Clarke , M. Clemencic , H.V. Cliff , J. Closier , J.L. Cobbledick , 47 11 10 9 36 47 542 V. Coco , J.A.B. Coelho , J. Cogan , E. Cogneras , L. Cojocariu , P. Collins , 47 26 52 58 44 47 543 T. Colombo , A. Contu , N. Cooke , G. Coombs , S. Coquereau , G. Corti , 55 47 63 66 1,y 544 C.M. Costa Sobral , B. Couturier , D.C. Craik , J. Crkovská , M. Cruz Torres , 57 66 14 45 47 38 545 R. Currie , C.L. Da Silva , E. Dall’Occo , J. Dalseno , C. D’Ambrosio , A. Danilina , 47 61 47 47 61 546 P. d’Argent , A. Davis , O. De Aguiar Francisco , K. De Bruyn , S. De Capua , 48 1 2 18,d 49 547 M. De Cian , J.M. De Miranda , L. De Paula , M. De Serio , D. De Simone , 22 77 66 82 8 12 548 P. De Simone , J.A. de Vries , C.T. Dean , W. Dean , D. Decamp , L. Del Buono , 54 14 34 72 49 80 549 B. Delaney , H.-P. Dembinski , A. Dendek , X. Denis , V. Denysenko , D. Derkach , 9 11 26,f 7 47 22 79 550 O. Deschamps , F. Desse , F. Dettori , B. Dey , A. Di Canto , P. Di Nezza , S. Didenko , 47 51 17 26 28,x 1 551 H. Dijkstra , V. Dobishuk , A.M. Donohoe , F. Dordei , M. Dorigo , A.C. dos Reis , 58 50 8 59 33 47 552 L. Douglas , A. Dovbnya , A.G. Downes , K. Dreimanis , M.W. Dudek , L. Dufour , 47 66 61 16 33 37 553 P. Durante , J.M. Durham , D. Dutta , M. Dziewiecki , A. Dziurda , A. Dzyuba , 56 69 38 42,w 57 48 554 S. Easo , U. Egede , V. Egorychev , S. Eidelman , S. Eisenhardt , S. Ek-In , 58 67 36 66 13 49 31 47 555 L. Eklund , S. Ely , A. Ene , E. Epple , S. Escher , J. Eschle , S. Esen , T. Evans , 19 3 5 72 52 59 11 38 556 A. Falabella , J. Fan , Y. Fan , B. Fang , N. Farley , S. Farry , D. Fazzini , P. Fedin ,

23 47 47 45 19,e 48 557 M. Féo , P. Fernandez Declara , A. Fernandez Prieto , F. Ferrari , L. Ferreira Lopes , 2 31 49 47 40 558 F. Ferreira Rodrigues , S. Ferreres Sole , M. Ferrillo , M. Ferro-Luzzi , S. Filippov , 18 20,g 34 62 61 34 559 R.A. Fini , M. Fiorini , M. Firlej , K.M. Fischer , C. Fitzpatrick , T. Fiutowski , 11,b 47 23,h 47 59 560 F. Fleuret , M. Fontana , F. Fontanelli , R. Forty , V. Franco Lima , 65 47 20 16 47 58 25,p 561 M. Franco Sevilla , M. Frank , E. Franzoso , G. Frau , C. Frei , D.A. Friday , J. Fu , 14 47 57 41 45 19,e 562 Q. Fuehring , W. Funk , E. Gabriel , T. Gaintseva , A. Gallas Torreira , D. Galli , 27 57 3 2 25 4 26 563 S. Gallorini , S. Gambetta , Y. Gan , M. Gandelman , P. Gandini , Y. Gao , M. Garau , 46 44 49 45 564 L.M. Garcia Martin , P. Garcia Moreno , J. Garc´ıaPardiñas , B. Garcia Plana , 11 44 44 47 31 16 565 F.A. Garcia Rosales , L. Garrido , D. Gascon , C. Gaspar , R.E. Geertsema , D. Gerick , 61 61 55 10 8 54 566 E. Gersabeck , M. Gersabeck , T. Gershon , D. Gerstel , Ph. Ghez , V. Gibson , 45 44 36 20,g 57 567 A. Gioventù , P. Gironella Gironell , L. Giubega , C. Giugliano , K. Gizdov , 12 70 44,l 38 60,79 1,a 568 V.V. Gligorov , C. Göbel , E. Golobardes , D. Golubkov , A. Golutvin , A. Gomes , 33 38 39 24,i 31 16 569 M. Goncerz , P. Gorbounov , I.V. Gorelov , C. Gotti , E. Govorkova , J.P. Grabowski , 44 12 47 44 48 570 R. Graciani Diaz , T. Grammatico , L.A. Granado Cardoso , E. Graugés , E. Graverini , 21 36 31 20,g 61 47 571 G. Graziani , A. Grecu , L.M. Greeven , P. Griffith , L. Grillo , L. Gruber , 62 3 20 16 40 13 572 B.R. Gruberg Cazon , C. Gu , M. Guarise , P. A. Günther , E. Gushchin , A. Guth , 43,47 47 69 48 47 54 573 Yu. Guz , T. Gys , T. Hadavizadeh , G. Haefeli , C. Haen , S.C. Haines , 65 7 16 62 16 62 574 P.M. Hamilton , Q. Han , X. Han , T.H. Hancock , S. Hansmann-Menzemer , N. Harnew , 59 31 47 47 5 60 31 575 T. Harrison , R. Hart , C. Hasse , M. Hatch , J. He , M. Hecker , K. Heijhoff , 14 47 59 25,46 13 68 576 K. Heinicke , A.M. Hennequin , K. Hennessy , L. Henry , J. Heuel , A. Hicheur , 62 61 14 48 16 71 7 5 577 D. Hill , M. Hilton , S.E. Hollitt , P.H. Hopchev , J. Hu , J. Hu , W. Hu , W. Huang , 31 60 55 80 59 31 578 W. Hulsbergen , T. Humair , R.J. Hunter , M. Hushchyn , D. Hutchcroft , D. Hynds , 14 34 37 52 37 37 47 579 P. Ibis , M. Idzik , D. Ilin , P. Ilten , A. Inglessi , K. Ivshin , R. Jacobsson , 47 31 46 65 14 3 62 580 S. Jakobsen , E. Jans , B.K. Jashal , A. Jawahery , V. Jevtic , F. Jiang , M. John , 47 54 55 47 62 50 3 581 D. Johnson , C.R. Jones , T.P. Jones , B. Jost , N. Jurik , S. Kandybei , Y. Kang , 47 53 80 16 54,47 67 582 M. Karacson , J.M. Kariuki , N. Kazeev , M. Kecke , F. Keizer , M. Kelsey , 55 32 47 81 43 67 13 583 M. Kenzie , T. Ketel , B. Khanji , A. Kharisova , S. Kholodenko , K.E. Kim , T. Kirn , 48 63 22 35 51 79 584 V.S. Kirsebom , O. Kitouni , S. Klaver , K. Klimaszewski , S. Koliiev , A. Kondybayeva , 38 34 16 31 39 585 A. Konoplyannikov , P. Kopciewicz , R. Kopecna , P. Koppenburg , M. Korolev , 31,51 51 37 37 40 47 586 I. Kostiuk , O. Kot , S. Kotriakhova , P. Kravchenko , L. Kravchuk , R.D. Krawczyk , 55 60 13 42,w 34 35 587 M. Kreps , F. Kress , S. Kretzschmar , P. Krokovny , W. Krupa , W. Krzemien , 83,33,k 33 42,w 31 66 588 W. Kucewicz , M. Kucharczyk , V. Kudryavtsev , H.S. Kuindersma , G.J. Kunde , 38 47 61 26 26 49 589 T. Kvaratskheliya , D. Lacarrere , G. Lafferty , A. Lai , A. Lampis , D. Lancierini , 61 53 22 13 49,79 55 590 J.J. Lane , R. Lane , G. Lanfranchi , C. Langenbruch , O. Lantwin , T. Latham , 28,u 10 82 9 39,47 79 10 591 F. Lazzari , R. Le Gac , S.H. Lee , R. Lefèvre , A. Leflat , S. Legotin , O. Leroy , 33 16 71 62 16 66 6 6 67 592 T. Lesiak , B. Leverington , H. Li , L. Li , P. Li , X. Li , Y. Li , Y. Li , Z. Li , 67 60 47 14 26 71 5 6 593 X. Liang , T. Lin , R. Lindner , V. Lisovskyi , R. Litvinov , G. Liu , H. Liu , S. Liu , 3 26 45 58 2 49 54 594 X. Liu , A. Loi , J. Lomba Castro , I. Longstaff , J.H. Lopes , G. Loustau , G.H. Lovell , 6 27,n 40 31 31 3 595 Y. Lu , D. Lucchesi , S. Luchuk , M. Lucio Martinez , V. Lukashenko , Y. Luo , 61 20,g 55 28,s 5 6 19,e 596 A. Lupato , E. Luppi , O. Lupton , A. Lusiani , X. Lyu , L. Ma , S. Maccolini , 11 36 48 14 53 597 F. Machefert , F. Maciuc , V. Macko , P. Mackowiak , S. Maddrell-Mander , 53 37 80 37 34 598 L.R. Madhan Mohan , O. Maev , A. Maevskiy , D. Maisuzenko , M.W. Majewski , 62 47 78 42,w 16 26,f 599 S. Malde , B. Malecki , A. Malinin , T. Maltsev , H. Malygina , G. Manca , 10 44 19,e 25,p 9,v 600 G. Mancinelli , R. Manera Escalero , D. Manuzzi , D. Marangotto , J. Maratas , 8 19 21,21,47 11 48 601 J.F. Marchand , U. Marconi , S. Mariani , C. Marin Benito , M. Marinangeli , 48 16 59 30 47 24,i 602 P. Marino , J. Marks , P.J. Marshall , G. Martellotti , L. Martinazzoli , M. Martinelli ,

24 45 46 1 13 47 603 D. Martinez Santos , F. Martinez Vidal , A. Massafferri , M. Materok , R. Matev , 49 47 38 24 82 49 604 A. Mathad , Z. Mathe , V. Matiunin , C. Matteuzzi , K.R. Mattioli , A. Mauri , 11,b 35 60 17 61 61 605 E. Maurice , M. Mazurek , M. McCann , L. Mcconnell , T.H. Mcgrath , A. McNab , 17 59 64 10 14 75 606 R. McNulty , J.V. Mead , B. Meadows , C. Meaux , G. Meier , N. Meinert , 35 24,i 31,77 25 2 47 607 D. Melnychuk , S. Meloni , M. Merk , A. Merli , L. Meyer Garcia , M. Mikhasenko , 73 55 8 20,g 57 61 608 D.A. Milanes , E. Millard , M.-N. Minard , L. Minzoni , S.E. Mitchell , B. Mitreska , 47 14 62 60 14 73 609 D.S. Mitzel , A. Mödden , R.A. Mohammed , R.D. Moise , T. Mombächer , I.A. Monroy , 9 27 22 28,s 34 74 610 S. Monteil , M. Morandin , G. Morello , M.J. Morello , J. Moron , A.B. Morris , 55 67 3 57 7 47 47 611 A.G. Morris , R. Mountain , H. Mu , F. Muheim , M. Mukherjee , M. Mulder , D. Müller , 49 62 61 26 53 48 612 K. Müller , C.H. Murphy , D. Murray , P. Muzzetto , P. Naik , T. Nakada , 56 48 2 57 20,g 25,p 74 613 R. Nandakumar , T. Nanut , I. Nasteva , M. Needham , I. Neri , N. Neri , S. Neubert , 47 60 48 48,m 11 13 614 N. Neufeld , R. Newcombe , T.D. Nguyen , C. Nguyen-Mau , E.M. Niel , S. Nieswand , 39 47 82 34 43 58 615 N. Nikitin , N.S. Nolte , C. Nunez , A. Oblakowska-Mucha , V. Obraztsov , S. Ogilvy , 53 26,f 76 82 33 616 D.P. O’Hanlon , R. Oldeman , C.J.G. Onderwater , J. D. Osborn , A. Ossowska , 2 38 49 46 55 617 J.M. Otalora Goicochea , T. Ovsiannikova , P. Owen , A. Oyanguren , B. Pagare , 47 28,47,s 18 22 61 81 618 P.R. Pais , T. Pajero , A. Palano , M. Palutan , Y. Pan , G. Panshin , 56 57 20,g 64 65 619 A. Papanestis , M. Pappagallo , L.L. Pappalardo , C. Pappenheimer , W. Parker , 61 45 20 21,47 18 60 620 C. Parkes , C.J. Parkinson , B. Passalacqua , G. Passaleva , A. Pastore , M. Patel , 19,e 47 31 47 19 38 621 C. Patrignani , A. Pearce , A. Pellegrino , M. Pepe Altarelli , S. Perazzini , D. Pereima , 9 53 23,h 78 57 25 622 P. Perret , K. Petridis , A. Petrolini , A. Petrov , S. Petrucci , M. Petruzzo , 41 28 8 48 62 30 47 623 A. Philippov , L. Pica , B. Pietrzyk , G. Pietrzyk , M. Pili , D. Pinci , J. Pinzino , 47 16 36 57 52 45 12 624 F. Pisani , A. Piucci , V. Placinta , S. Playfer , J. Plews , M. Plo Casasus , F. Polci , 22 67 10 79,c 67 2 625 M. Poli Lener , M. Poliakova , A. Poluektov , N. Polukhina , I. Polyakov , E. Polycarpo , 53 47 43 5,47 41 43 33 626 G.J. Pomery , S. Ponce , A. Popov , D. Popov , S. Popov , S. Poslavskii , K. Prasanth , 47 45 51 49 62 28,o 627 L. Promberger , C. Prouve , V. Pugatch , A. Puig Navarro , H. Pullen , G. Punzi , 10 5 5 12 8 628 R. Puthumanaillam Krishnankuttyelayath , W. Qian , J. Qin , R. Quagliani , B. Quintana , 17 10 34 53 28 629 N.V. Raab , R.I. Rabadan Trejo , B. Rachwal , J.H. Rademacker , M. Rama , 45 2 41,80 32 8 48 630 M. Ramos Pernas , M.S. Rangel , F. Ratnikov , G. Raven , M. Reboud , F. Redi , 12 46 3 62 28 56 631 F. Reiss , C. Remon Alepuz , Z. Ren , V. Renaudin , R. Ribatti , S. Ricciardi , 56 59 11 12 57 48 632 D.S. Richards , K. Rinnert , P. Robbe , A. Robert , G. Robertson , A.B. Rodrigues , 59 73 47 62 43 633 E. Rodrigues , J.A. Rodriguez Lopez , M. Roehrken , A. Rollings , V. Romanovskiy , 45 45 82 22 67 47 634 M. Romero Lamas , A. Romero Vidal , J.D. Roth , M. Rotondo , M.S. Rudolph , T. Ruf , 46 80 34 45 37 55 635 J. Ruiz Vidal , A. Ryzhikov , J. Ryzka , J.J. Saborido Silva , N. Sagidova , N. Sahoo , 26,f 31 46 30 636 B. Saitta , C. Sanchez Gras , C. Sanchez Mayordomo , R. Santacesaria , 45 22 29,j 79 61 637 C. Santamarina Rios , M. Santimaria , E. Santovetti , D. Saranin , G. Sarpis , 74 30 30,r 29 5 38,39 9 638 M. Sarpis , A. Sarti , C. Satriano , A. Satta , M. Saur , D. Savrina , H. Sazak , 62 13 14 58 47 639 L.G. Scantlebury Smead , S. Schael , M. Schellenberg , M. Schiller , H. Schindler , 15 14 47 48 47 64 640 M. Schmelling , T. Schmelzer , B. Schmidt , O. Schneider , A. Schopper , H.F. Schreiner , 31 48 11 47 22 22 641 M. Schubiger , S. Schulte , M.H. Schune , R. Schwemmer , B. Sciascia , A. Sciubba , 68 38 52,47 49 10 27 14 642 S. Sellam , A. Semennikov , A. Sergi , N. Serra , J. Serrano , L. Sestini , A. Seuthe , 47 82 43 79 48 59 643 P. Seyfert , D.M. Shangase , M. Shapkin , I. Shchemerov , L. Shchutska , T. Shears , 42,w 78 24,i 79 67 644 L. Shekhtman , V. Shevchenko , E.B. Shields , E. Shmanin , J.D. Shupperd , 20 49 2 27 18,d 20,g 645 B.G. Siddi , R. Silva Coutinho , L. Silva de Oliveira , G. Simi , S. Simone , I. Skiba , 74 67 52 62 54 646 N. Skidmore , T. Skwarnicki , M.W. Slater , J.C. Smallwood , J.G. Smeaton , 38 13 60 31 19 9 647 A. Smetkina , E. Smith , M. Smith , A. Snoch , M. Soares , L. Soares Lavra , 64 58 37 37 2 648 M.D. Sokoloff , F.J.P. Soler , A. Solovev , I. Solovyev , F.L. Souza De Almeida ,

25 2 14 25,p 58 47 64 649 B. Souza De Paula , B. Spaan , E. Spadaro Norella , P. Spradlin , F. Stagni , M. Stahl , 47 48 49,79 16 43 14 650 S. Stahl , P. Stefko , O. Steinkamp , S. Stemmle , O. Stenyakin , H. Stevens , 67 28 48 36 79 81 651 S. Stone , S. Stracka , M.E. Stramaglia , M. Straticiuc , D. Strekalina , S. Strokov , 62 26 72 65 61 52 34 652 F. Suljik , J. Sun , L. Sun , Y. Sun , P. Svihra , P.N. Swallow , K. Swientek , 35 34 47 61 3 14 653 A. Szabelski , T. Szumlak , M. Szymanski , S. Taneja , Z. Tang , T. Tekampe , 47 47 59 60 9 8 654 F. Teubert , E. Thomas , K.A. Thomson , M.J. Tilley , V. Tisserand , S. T’Jampens , 6 47 20,g 1 12 58 655 M. Tobin , S. Tolk , L. Tomassetti , D. Torres Machado , D.Y. Tou , M. Traill , 48 79 48 10 28,o 48 656 M.T. Tran , E. Trifonova , C. Trippl , A. Tsaregorodtsev , G. Tuci , A. Tully , 31 35 16 31 41,80 16 657 N. Tuning , A. Ukleja , D.J. Unverzagt , A. Usachov , A. Ustyuzhanin , U. Uwer , 81 19 47 19 31 66 658 A. Vagner , V. Vagnoni , A. Valassi , G. Valenti , M. van Beuzekom , H. Van Hecke , 79 17 76 45 659 E. van Herwijnen , C.B. Van Hulse , M. van Veghel , R. Vazquez Gomez , 45 31 20 53 21,q 660 P. Vazquez Regueiro , C. V´azquezSierra , S. Vecchi , J.J. Velthuis , M. Veltri , 67 31 55 64 48 661 A. Venkateswaran , M. Veronesi , M. Vesterinen , D. Vieira , M. Vieites Diaz , 75 44 59 12 28 662 H. Viemann , X. Vilasis-Cardona , E. Vilella Figueras , P. Vincent , G. Vitali , 31 49 12 37 42,w 663 A. Vitkovskiy , A. Vollhardt , D. Vom Bruch , A. Vorobyev , V. Vorobyev , 37 75 28 16 3 72 4 6 664 N. Voropaev , R. Waldi , J. Walsh , C. Wang , J. Wang , J. Wang , J. Wang , J. Wang , 3 53 7 49 54 59 52 665 M. Wang , R. Wang , Y. Wang , Z. Wang , D.R. Ward , H.M. Wark , N.K. Watson , 12 60 63 53 61 53 666 S.G. Weber , D. Websdale , C. Weisser , B.D.C. Westhenry , D.J. White , M. Whitehead , 14 62 67 54 63,69 667 D. Wiedner , G. Wilkinson , M. Wilkinson , I. Williams , M. Williams , 61 56 35 33 16 11 668 M.R.J. Williams , F.F. Wilson , W. Wislicki , M. Witek , L. Witola , G. Wormser , 54 67 47 5 7 7 71 4 5 669 S.A. Wotton , H. Wu , K. Wyllie , Z. Xiang , D. Xiao , Y. Xie , H. Xing , A. Xu , J. Xu , 3 7 5 4 3 5 3 65 67 670 L. Xu , M. Xu , Q. Xu , Z. Xu , D. Yang , Y. Yang , Z. Yang , Z. Yang , Y. Yao , 59 7 7 67 43 52 671 L.E. Yeomans , H. Yin , J. Yu , X. Yuan , O. Yushchenko , K.A. Zarebski , 15,c 33 47 3 7 3 4 672 M. Zavertyaev , M. Zdybal , O. Zenaiev , M. Zeng , D. Zhang , L. Zhang , S. Zhang , 47 16 5 5 5 3 13,39 673 Y. Zhang , A. Zhelezov , Y. Zheng , X. Zhou , Y. Zhou , X. Zhu , V. Zhukov , 57 19,e 27 61 674 J.B. Zonneveld , S. Zucchelli , D. Zuliani , G. Zunica .

1 675 Centro Brasileiro de Pesquisas F´ısicas (CBPF), Rio de Janeiro, Brazil 2 676 Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil 3 677 Center for High Energy Physics, Tsinghua University, Beijing, China 4 678 School of Physics State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing, 679 China 5 680 University of Chinese Academy of Sciences, Beijing, China 6 681 Institute Of High Energy Physics (IHEP), Beijing, China 7 682 Institute of Particle Physics, Central China Normal University, Wuhan, Hubei, China 8 683 Univ. Grenoble Alpes, Univ. Savoie Mont Blanc, CNRS, IN2P3-LAPP, Annecy, France 9 684 UniversitéClermont Auvergne, CNRS/IN2P3, LPC, Clermont-Ferrand, France 10 685 Aix Marseille Univ, CNRS/IN2P3, CPPM, Marseille, France 11 686 UniversitéParis-Saclay, CNRS/IN2P3, IJCLab, Orsay, France 12 687 LPNHE, Sorbonne Université,Paris Diderot Sorbonne Paris Cité,CNRS/IN2P3, Paris, France 13 688 I. Physikalisches Institut, RWTH Aachen University, Aachen, Germany 14 689 FakultätPhysik, Technische UniversitätDortmund, Dortmund, Germany 15 690 Max-Planck-Institut für Kernphysik (MPIK), Heidelberg, Germany 16 691 Physikalisches Institut, Ruprecht-Karls-UniversitätHeidelberg, Heidelberg, Germany 17 692 School of Physics, University College Dublin, Dublin, Ireland 18 693 INFN Sezione di Bari, Bari, Italy 19 694 INFN Sezione di Bologna, Bologna, Italy 20 695 INFN Sezione di Ferrara, Ferrara, Italy 21 696 INFN Sezione di Firenze, Firenze, Italy

26 22 697 INFN Laboratori Nazionali di Frascati, Frascati, Italy 23 698 INFN Sezione di Genova, Genova, Italy 24 699 INFN Sezione di Milano-Bicocca, Milano, Italy 25 700 INFN Sezione di Milano, Milano, Italy 26 701 INFN Sezione di Cagliari, Monserrato, Italy 27 702 Universita degli Studi di Padova, Universita e INFN, Padova, Padova, Italy 28 703 INFN Sezione di Pisa, Pisa, Italy 29 704 INFN Sezione di Roma Tor Vergata, Roma, Italy 30 705 INFN Sezione di Roma La Sapienza, Roma, Italy 31 706 Nikhef National Institute for Subatomic Physics, Amsterdam, Netherlands 32 707 Nikhef National Institute for Subatomic Physics and VU University Amsterdam, Amsterdam, 708 Netherlands 33 709 Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences, Kraków,Poland 34 710 AGH - University of Science and Technology, Faculty of Physics and Applied Computer Science, 711 Kraków,Poland 35 712 National Center for Nuclear Research (NCBJ), Warsaw, Poland 36 713 Horia Hulubei National Institute of Physics and Nuclear Engineering, Bucharest-Magurele, Romania 37 714 Petersburg Nuclear Physics Institute NRC Kurchatov Institute (PNPI NRC KI), Gatchina, Russia 38 715 Institute of Theoretical and Experimental Physics NRC Kurchatov Institute (ITEP NRC KI), Moscow, 716 Russia, Moscow, Russia 39 717 Institute of Nuclear Physics, Moscow State University (SINP MSU), Moscow, Russia 40 718 Institute for Nuclear Research of the Russian Academy of Sciences (INR RAS), Moscow, Russia 41 719 Yandex School of Data Analysis, Moscow, Russia 42 720 Budker Institute of Nuclear Physics (SB RAS), Novosibirsk, Russia 43 721 Institute for High Energy Physics NRC Kurchatov Institute (IHEP NRC KI), Protvino, Russia, 722 Protvino, Russia 44 723 ICCUB, Universitat de Barcelona, Barcelona, Spain 45 724 Instituto Galego de F´ısica de Altas Enerx´ıas(IGFAE), Universidade de Santiago de Compostela, 725 Santiago de Compostela, Spain 46 726 Instituto de Fisica Corpuscular, Centro Mixto Universidad de Valencia - CSIC, Valencia, Spain 47 727 European Organization for Nuclear Research (CERN), Geneva, Switzerland 48 728 Institute of Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland 49 729 Physik-Institut, UniversitätZürich,Zürich,Switzerland 50 730 NSC Kharkiv Institute of Physics and Technology (NSC KIPT), Kharkiv, Ukraine 51 731 Institute for Nuclear Research of the National Academy of Sciences (KINR), Kyiv, Ukraine 52 732 University of Birmingham, Birmingham, United Kingdom 53 733 H.H. Wills Physics Laboratory, University of Bristol, Bristol, United Kingdom 54 734 Cavendish Laboratory, University of Cambridge, Cambridge, United Kingdom 55 735 Department of Physics, University of Warwick, Coventry, United Kingdom 56 736 STFC Rutherford Appleton Laboratory, Didcot, United Kingdom 57 737 School of Physics and Astronomy, University of Edinburgh, Edinburgh, United Kingdom 58 738 School of Physics and Astronomy, University of Glasgow, Glasgow, United Kingdom 59 739 Oliver Lodge Laboratory, University of Liverpool, Liverpool, United Kingdom 60 740 Imperial College London, London, United Kingdom 61 741 Department of Physics and Astronomy, University of Manchester, Manchester, United Kingdom 62 742 Department of Physics, University of Oxford, Oxford, United Kingdom 63 743 Massachusetts Institute of Technology, Cambridge, MA, United States 64 744 University of Cincinnati, Cincinnati, OH, United States 65 745 University of Maryland, College Park, MD, United States 66 746 Los Alamos National Laboratory (LANL), Los Alamos, United States 67 747 Syracuse University, Syracuse, NY, United States 68 2 748 Laboratory of Mathematical and Subatomic Physics , Constantine, Algeria, associated to

27 69 55 749 School of Physics and Astronomy, Monash University, Melbourne, Australia, associated to 70 2 750 Pontif´ıciaUniversidade Católica do Rio de Janeiro (PUC-Rio), Rio de Janeiro, Brazil, associated to 71 751 Guangdong Provencial Key Laboratory of Nuclear Science, Institute of Quantum Matter, South China 3 752 Normal University, Guangzhou, China, associated to 72 3 753 School of Physics and Technology, Wuhan University, Wuhan, China, associated to 73 12 754 Departamento de Fisica , Universidad Nacional de Colombia, Bogota, Colombia, associated to 74 16 755 UniversitätBonn - Helmholtz-Institut fürStrahlen und Kernphysik, Bonn, Germany, associated to 75 16 756 Institut fürPhysik, UniversitätRostock, Rostock, Germany, associated to 76 31 757 Van Swinderen Institute, University of Groningen, Groningen, Netherlands, associated to 77 31 758 Universiteit Maastricht, Maastricht, Netherlands, associated to 78 38 759 National Research Centre Kurchatov Institute, Moscow, Russia, associated to 79 38 760 National University of Science and Technology “MISIS”, Moscow, Russia, associated to 80 41 761 National Research University Higher School of Economics, Moscow, Russia, associated to 81 38 762 National Research Tomsk Polytechnic University, Tomsk, Russia, associated to 82 67 763 University of Michigan, Ann Arbor, United States, associated to 83 764 AGH - University of Science and Technology, Faculty of Computer Science, Electronics and 765 Telecommunications, Kraków,Poland

a 766 Universidade Federal do TriânguloMineiro (UFTM), Uberaba-MG, Brazil b 767 Laboratoire Leprince-Ringuet, Palaiseau, France c 768 P.N. Lebedev Physical Institute, Russian Academy of Science (LPI RAS), Moscow, Russia d 769 Universitàdi Bari, Bari, Italy e 770 Universitàdi Bologna, Bologna, Italy f 771 Universitàdi Cagliari, Cagliari, Italy g 772 Universitàdi Ferrara, Ferrara, Italy h 773 Universitàdi Genova, Genova, Italy i 774 Universitàdi Milano Bicocca, Milano, Italy j 775 Universitàdi Roma Tor Vergata, Roma, Italy k 776 AGH - University of Science and Technology, Faculty of Computer Science, Electronics and 777 Telecommunications, Kraków,Poland l 778 DS4DS, La Salle, Universitat Ramon Llull, Barcelona, Spain m 779 Hanoi University of Science, Hanoi, Vietnam n 780 Universitàdi Padova, Padova, Italy o 781 Universitàdi Pisa, Pisa, Italy p 782 Universitàdegli Studi di Milano, Milano, Italy q 783 Universitàdi Urbino, Urbino, Italy r 784 Universitàdella Basilicata, Potenza, Italy s 785 Scuola Normale Superiore, Pisa, Italy t 786 Universitàdi Modena e Reggio Emilia, Modena, Italy u 787 Universitàdi Siena, Siena, Italy v 788 MSU - Iligan Institute of Technology (MSU-IIT), Iligan, Philippines w 789 Novosibirsk State University, Novosibirsk, Russia x 790 INFN Sezione di Trieste, Trieste, Italy y 791 Universidad Nacional Autonoma de Honduras, Tegucigalpa, Honduras