Study of bb¯correlations in high energy proton-proton collisions

JHEP11(2017)030 Published for SISSA by Springer Received:August 22, 2017 Revised:October 16, 2017 Accepted:October 20, 2017 Published:November 8, 2017 Study of bb correlations in high energy proton-proton collisions The LHCb collaboration E-mail: [email protected] Abstract: Kinematic correlations for pairs of beauty hadrons, produced in high energy proton-proton collisions, are studied. The data sample used was collected with the LHCb experiment at centre-of-mass energies of 7 and 8 TeV and corresponds to an integrated luminosity of 3 fb−1. The measurement is performed using inclusive b →J/ψX decays in the rapidity range 2 < yJ/ψ <4.5. The observed correlations are in good agreement with theoretical predictions. Keywords: Forward physics, Hadron-Hadron scattering (experiments), Heavy quark production, Particle and resonance production, QCD ArXiv ePrint: 1708.05994 Open Access, Copyright CERN, for the benefit of the LHCb Collaboration. Article funded by SCOAP3. https://doi.org/10.1007/JHEP11(2017)030 JHEP11(2017)030 Contents 1 Introduction 1 2 Detector and simulation 2 3 Signal selection and efficiency determination 3 3.1 Systematic uncertainties 7 4 Results 8 5 Summary and conclusions 13 A Additional variables 14 The LHCb collaboration 23 1 Introduction The production of heavy-flavour hadrons in high energy collisions provides important tests for the predictions of quantum chromodynamics (QCD). Open-charm hadron production has been studied in pp collisions at the Large Hadron Collider (LHC) by the LHCb collaboration at centre-of-mass energies √s= 5, 7 and 13 TeV [1–3], by the ATLAS collaboration at √s= 7 TeV [4] and by the ALICE collaboration at √s= 2.76 and 7 TeV [5–8]. In addition, the CDF collaboration has studied the production of open-charm hadrons in pp collisions at the Tevatron at √s= 1.96 TeV [9,10]. For beauty hadrons, the production cross-sections in high energy pp and pp collisions have been studied by a number of collaborations [11–14]. Most recently, at the LHC, the LHCb collaboration at √s= 7, 8 and 13 TeV and the CMS collaboration at √s= 8 TeV studied beauty hadron production using semileptonic decays [15,16], inclusive decays of beauty hadrons into J/ψmesons [17–19], and exclusive B0→J/ψK(892)∗0, B+→J/ψK+, B0 s→J/ψK+K−[20–23], Λ0 b→J/ψpK−[24,25] and B+ c→J/ψπ+[26,27] decays. The transverse momentum, pT, and rapidity, y, spectra are found to be in agreement with calculations at next-to-leading order (NLO). These calculations are made using the general-mass variable-flavour-number scheme (GMVFNS) [28– 32], Powheg [33] and fixed-order with next-to-leading-log resummation (FONLL) [34–39]. For B+ cmesons, a good agreement in the shapes of the pTand yspectra is found [27] with calculations based on a complete order-α4 sapproach [40–43]. However, the inclusive single-heavy-flavour hadron transverse momentum and rapidity spectra have limited sensitivity to the subprocesses of the production mechanism and the size of higher-order QCD corrections. – 1 – JHEP11(2017)030 The kinematic correlations between the heavy quark and antiquark provide additional information and can enable a better understanding of the production mechanism, such as the contribution of the gluon-splitting, flavour-creation and flavour-excitation processes, as well as the role of higher-order corrections. Such correlations have been studied for pairs of open-charm mesons by the CDF collaboration in the central rapidity region |y|<1 [44,45] and by the LHCb collaboration in the forward rapidity region 2 < y < 4 [46]. The difference in the azimuthal angle, φ, between two reconstructed open-charm mesons shows a strong correlation, which demonstrates the importance of the gluon-splitting mechanism for the production of cc events. For charm production in the central rapidity region, the contributions from flavour-creation and flavour-excitation processes have been identified, in addition to that from gluon splitting [44,45]. The azimuthal and rapidity correlations in bb production have been studied by the UA1 [47], D0 [48] and CDF [49–52] collaborations in pp collisions at √s= 0.63, 1.8 and 1.96 TeV. At the LHC, the first study of bb correlations in high energy pp collisions in the central rapidity region has been performed by the CMS collaboration [53]. The collaboration found that none of the available calculations describe the shapes of the differential cross-section well [54–58]. In particular, the region where the contributions of gluon-splitting processes are expected to be large is not adequately described by any of the predictions from MC@NLO [54–56], Cascade [57,58], Pythia 8 [59], or MadGraph [60,61]. Recently, a study of bb correlations in pp collisions in the central rapidity region has been performed by the ATLAS collaboration [62] and a good agreement with calculations was obtained. The four-flavour MadGraph5 prediction [63] provides the best overall agreement with data, and performs better than the Pythia 8 and Herwig++ [64] generators. This paper reports the study of bb correlations in high energy hadron collisions in the forward rapidity region. The data sample used was collected with the LHCb experiment at centre-of-mass energies of 7 and 8 TeV and corresponds to integrated luminosities of 1 and 2 fb−1, respectively. The beauty hadrons are reconstructed via their inclusive decays into J/ψmesons, denoted here as b →J/ψX decays, using J/ψmesons decaying into the µ+µ−final state. The results are compared with the leading-order (LO) and NLO expectations from Pythia [59,65] and Powheg [66–69], respectively. 2 Detector and simulation The LHCb detector [70,71] 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 detector includes a high-precision tracking system consisting of a silicon-strip vertex detector surrounding the pp interaction region [72], 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/c. The minimum distance of a track to a primary vertex (PV), the impact parameter (IP), – 2 – JHEP11(2017)030 is measured with a resolution of (15 + 29/pT)µm, where pTis the component of the momentum transverse to the beam, in GeV/c. Different types of charged hadrons are distinguished using information from two ring-imaging Cherenkov detectors. Photons, electrons and hadrons are identified by a calorimeter system consisting of scintillating-pad and preshower detectors, an electromagnetic calorimeter and a hadronic calorimeter. Muons are identified by a system composed of alternating layers of iron and multiwire proportional chambers [73]. The online event selection is performed by a trigger [74], 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 hardware trigger selects pairs of opposite-sign muon candidates with a requirement that the product of the muon transverse momenta is larger than 1.7 (2.6) GeV2/c2for data collected at √s= 7 (8) TeV. The subsequent software trigger is composed of two stages, the first of which performs a partial event reconstruction. A full event reconstruction is then made at the second stage. In the software trigger, the invariant mass of well-reconstructed pairs of oppositely charged muons that form a vertex with good reconstruction quality is required to exceed 2.7 GeV/c2and the vertex is required to be significantly displaced from all PVs. Simulated samples are used to determine the reconstruction and trigger efficiencies. Proton-proton collisions are generated using Pythia [59,65] with a specific LHCb configuration [75]. Decays of hadronic particles are described by EvtGen [76], in which final-state radiation is generated using Photos [77]. The interaction of the generated particles with the detector, and its response, are implemented using the Geant4 toolkit [78,79] as described in ref. [80]. 3 Signal selection and efficiency determination Selected events are required to have two reconstructed J/ψ→µ+µ−candidates. In the following these two candidates are marked with subscripts 1 and 2, which are randomly assigned. The muon candidates must be identified as muons, have good reconstruction quality, pT>500 MeV/c and 2 <η<5 [73,81]. Both reconstructed J/ψcandidates are required to have a good-quality vertex, a reconstructed mass in the range 3.00 < mµ+µ−<3.18 GeV/c2, 2 < pJ/ψ T<25 GeV/c and 2 < yJ/ψ<4.5. These criteria ensure a good reconstruction and trigger efficiency. Only events triggered by at least one of the J/ψcandidates are retained. The two J/ψcandidates are required to be associated with the same PV and, in order to suppress background from promptly produced J/ψmesons, both dimuon vertices are required to be significantly displaced from that PV. The two-dimensional distribution of the µ+µ−masses, mµ+µ− 1and mµ+µ− 2, for the selected pairs of J/ψ→µ+µ−candidates is presented in figure 1for several requirements on pJ/ψ T. A clear signal peak, corresponding to events with two J/ψmesons detached from the PV, is visible. The signal yield is determined by performing an extended unbinned maximum likelihood fit to the two-dimensional mass distribution. The distribution is fitted with the func- – 3 – JHEP11(2017)030 3 3.05 3.1 3.15 3 3.05 3.1 3.15 0 50 100 150 200 3 3.05 3.1 3.15 3 3.05 3.1 3.15 0 50 100 3 3.05 3.1 3.15 3 3.05 3.1 3.15 0 10 20 30 3 3.05 3.1 3.15 3 3.05 3.1 3.15 0 5 10 mµ+µ− 1GeV/c2 mµ+µ− 2GeV/c2 mµ+µ− 1GeV/c2 mµ+µ− 2GeV/c2 mµ+µ− 1GeV/c2 mµ+µ− 2GeV/c2 mµ+µ− 1GeV/c2 mµ+µ− 2GeV/c2 Candidates/(10 MeV/c2)2 Candidates/(10 MeV/c2)2 Candidates/(10 MeV/c2)2 Candidates/(20 MeV/c2)2 LHCb √s= 7,8 TeV a) pJ/ψ T>2 GeV/c b) pJ/ψ T>3 GeV/c c) pJ/ψ T>5 GeV/c d) pJ/ψ T>7 GeV/c Figure 1. Distribution of mµ+µ− 1vs mµ+µ− 2for selected pairs of J/ψ→µ+µ−candidates in different pJ/ψ Tregions. tion F(m1, m2) = NSS S(m1)S(m2) +NSB 2S(m1)B0(m2) + B0(m1)S(m2) +NBB B00 (m1, m2), where the first term corresponds to a signal of two J/ψmesons, the second term corresponds to a combination of one J/ψmeson and combinatorial background; and the last term describes pure combinatorial background. The coefficients NSS,NSB and NBB are the yields for these three components. The signal component, denoted as S(m), is modelled by a double-sided Crystal Ball function [82,83]. The background component, B0(m), is parameterized as the product of an exponential and a first-order polynomial function and the background component B00(m1, m2) is parameterized as the product of two exponential functions e−τm1and e−τm2, with the same slope parameter, τ, and a symmetric second-order polynomial. With these parameterizations the overall function is symmetric, F(m2, m1)≡F(m1, m2). The power-law tail parameters of the double-sided Crystal Ball function are fixed to the values obtained from simulation, leaving the mean and the core width as free parameters. Results of the extended unbinned maximum likelihood fit for – 4 – JHEP11(2017)030 3.05 3.1 3.15 0 20 40 60 80 100 120 140 160 180 200 220 240 3.05 3.1 3.15 0 20 40 60 80 100 120 140 160 180 200 220 240 Candidates/(2 MeV/c2) Candidates/(2 MeV/c2) mµ+µ− 1GeV/c2mµ+µ− 2GeV/c2 LHCb √s= 7,8 TeV J/ψJ/ψ J/ψ+ comb. comb. total fit pJ/ψ T>2 GeV/c Figure 2. Projections of the extended unbinned maximum likelihood fit to (left) mµ+µ− 1and (right) mµ+µ− 2for pJ/ψ T>2 GeV. The total fit function is shown as a solid thick orange line. The solid thin red curve shows the signal component, while the background with one true J/ψcandidate is shown by the dashed magenta line and the pure combinatorial background is shown with a dotted thin blue line. pJ/ψ T>2 GeV/c pJ/ψ T>3 GeV/c pJ/ψ T>5 GeV/c pJ/ψ T>7 GeV/c NSS 2066 ±72 1092 ±50 302 ±17 98 ±13 NSB 2066 ±88 949 ±58 217 ±17 40 ±13 NBB 945 ±73 343 ±50 39 ±12 11 ±9 Table 1. Signal and background yields from the extended unbinned maximum likelihood fit for different requirements on pJ/ψ T. The uncertainties are statistical only. the different requirements on pJ/ψ Tare presented in table 1. Figure 2shows the projections of the fit for pJ/ψ T>2 GeV/c. Several background sources potentially contribute to the observed J/ψ-pair signal. The first group of sources involves events where two J/ψmesons originate from different pp collision vertices: it includes events with two J/ψmesons from decays of beauty hadrons, events with one J/ψmeson originating from a beauty hadron decay and another J/ψmeson produced promptly and, finally, events with two prompt J/ψmesons. The second group of sources consists of events where both J/ψmesons originate from the same pp collision, namely prompt J/ψ-pair production [83,84], and associated production of a prompt J/ψmeson and a bb pair, where one of the b hadrons decays into a J/ψmeson. The contribution from the first group of background sources is estimated from the measured production cross-sections for b →J/ψX and prompt J/ψevents [17,18], the multiplicity of pp collision vertices and the size of the beam collision region. Taking from simulation an estimate for the probability of reconstructing two spatially close PVs as a single PV, the total relative contribution from these sources is found to be less than 0.1%. For the second group of background sources, the contribution from prompt J/ψ-pair production is significantly suppressed by the requirement that both dimuon vertices are – 5 – JHEP11(2017)030 displaced from the PV. Using the production cross-section for prompt J/ψpairs,1the relative contribution from this source is estimated to be less than 0.05%. The background from associated production of bb and a prompt J/ψmeson in the same pp collision is calculated assuming double parton scattering is the dominant production mechanism, following ref. [85]. The relative contribution from this source is estimated to be less than 0.05%. Normalized differential cross-sections [46,85] are presented as a function of kinematic variables, defined below, and here generically denoted as v, 1 σ dσ dv≡1 Ncor ∆Ncor i ∆vi ,(3.2) where Ncor is the total number of efficiency-corrected signal candidates, ∆Ncor iis the number of efficiency-corrected signal candidates in bin i, and ∆viis the corresponding bin width. The efficiency-corrected yields Ncor and ∆Ncor iare calculated as in refs. [46,86] Ncor =X j ωj J/ψJ/ψ tot,j , ∆Ncor i=X j⊂i ωj J/ψJ/ψ tot,j , where the sum runs over all pairs of J/ψcandidates in the case of Ncor and all pairs of J/ψcandidates in bin iin the case of ∆Ncor i. Here J/ψJ/ψ tot is the total efficiency for the pair of J/ψcandidates and the weights ωjare determined using the sPlot technique [87]. The total efficiency of the J/ψpair is estimated on an event-by-event basis as in refs. [46,83–86] J/ψJ/ψ tot =J/ψJ/ψ acc J/ψJ/ψ rec&sel J/ψJ/ψ µID J/ψJ/ψ trg ,(3.3) where acc is the geometrical acceptance of the LHCb detector, rec&sel is the reconstruction and selection efficiency for candidates with all final-state muons inside the geometrical acceptance, µID is the muon identification (µID) efficiency for the selected candidates and trg is the trigger efficiency for the selected candidates satisfying the µID requirement. The efficiencies, acc,rec&sel and µID, are factorized as J/ψJ/ψ≡J/ψ1J/ψ2,(3.4) while the trigger efficiency is decomposed as in refs. [46,83,84] J/ψJ/ψ trg ≡1−1−J/ψ1 trg 1−J/ψ2 trg .(3.5) The efficiencies J/ψ acc ,J/ψ rec&sel and J/ψ trg are estimated as functions of the transverse momentum and rapidity of the J/ψmeson using simulation. The trigger efficiency for single J/ψmesons, J/ψ trg , has been validated using data. The muon identification efficiency for J/ψmesons is factorized as J/ψ µID ≡µ+ µID µ− µID,(3.6) 1The production cross-section of J/ψpairs is measured at √s= 7 TeV [83]. The cross-section at √s= 8 TeV is estimated using a linear interpolation between the measurements at √s= 7 TeV and √s= 13 TeV [84]. – 6 – JHEP11(2017)030 Source Uncertainty [%] Signal determination <1.0 Muon identification 0.4 Track reconstruction 1.7 Trigger 1.2 Simulated sample size <0.1 Table 2. Summary of relative systematic uncertainties for the efficiency-corrected signal yield. where the corresponding single-muon identification efficiency, µ± µID, is determined as a function of muon momentum and pseudorapidity using large samples of prompt J/ψmesons. 3.1 Systematic uncertainties The systematic uncertainty due to the imprecise determination of the luminosity does not enter in the normalized differential cross-sections. The systematic uncertainties, related to the evaluation of the efficiency-corrected signal yields Ncor and ∆Ncor ifrom eq. (3.2) are summarized in table 2and are discussed in detail below. Systematic uncertainties associated with the signal determination are studied by varying the signal and background shapes used for the fit function. For the signal parameterization, the power-law tail parameters of the double-sided Crystal Ball function are varied according to the results of fits to large samples of low-background b →J/ψX and B+→J/ψK+candidates. The alternative signal shape parameterization from ref. [88] is also used in the fits. For the parameterization of the background functions, B0(m) and B00(m1, m2), the order of the polynomial functions is varied. The difference in the fitted signal yields does not exceed 1% in all of the above cases. The systematic uncertainty related to the muon identification is estimated to be 0.4%. It is obtained from the uncertainties for the single-particle identification efficiencies, µ± µID, using pseudoexperiments. The efficiency J/ψ rec&sel is corrected on a per-track basis for small discrepancies between data and simulation using data-driven techniques [81,89]. The uncertainty in the correction factor is propagated to the determination of the efficiency-corrected signal yields using pseudoexperiments. This results in a systematic uncertainty of 0.6%. Added in quadrature to the (correlated) uncertainty from the track reconstruction of 0.4% per track (1.6% in total) these sources give an overall systematic uncertainty associated with the track reconstruction of 1.7%. The trigger efficiency has been validated using large low-background samples of B+→J/ψK+decays and inclusive samples of J/ψmesons. Taking the largest difference between simulation and data for J/ψ trg , the corresponding systematic uncertainty for the efficiency-corrected yields is 1.2%. The uncertainties in the efficiencies J/ψ acc ,J/ψ rec&sel and J/ψ trg , which are due to the limited size of the simulation samples, are propagated to the efficiency-corrected signal yields using pseudoexperiments and are less than 0.1%. – 7 – JHEP11(2017)030 Part of the uncertainties, summarized in table 2, cancel in the ratio ∆Ncor i Ncor and thus do not affect the normalized differential cross-sections. For all bins for which the normalized differential cross-sections are evaluated, the systematic uncertainty is much smaller than the corresponding statistical uncertainty and is therefore neglected hereafter. 4 Results The normalized differential production cross-sections defined by eq. (3.2) are presented as a function of the following variables: • |∆φ∗|, the difference in the azimuthal angle, φ∗, between the two beauty hadrons, where φ∗is estimated from the direction of the vector from the PV to the decay vertex of the J/ψmeson; • |∆η∗|, the difference in the pseudorapidity, η∗, between the two beauty hadrons, where η∗is estimated from the direction of the vector from the PV to the decay vertex of the J/ψmeson; • AT≡    pJ/ψ1 T−pJ/ψ2 T pJ/ψ1 T+pJ/ψ2 T     , the asymmetry between the transverse momenta of two J/ψmesons; •mJ/ψJ/ψ, the mass of the J/ψpair; •pJ/ψJ/ψ T, the transverse momentum of the J/ψpair; •yJ/ψJ/ψ, the rapidity of the J/ψpair. The differential cross-sections with respect to other variables are given in appendix A. The shapes for the differential production cross-sections for |∆φ∗|and |∆η∗|variables are independent of the decay of the long-lived beauty hadrons and directly probe the production properties of pairs of beauty hadrons. The other variables have a minor dependence both on the branching fractions of different beauty hadrons, as well as on the b →J/ψX decay kinematics. The normalized differential production cross-sections are shown in figures 3,4,5and 6 for different requirements on the minimum transverse momentum of the J/ψmesons. Since the distributions obtained for data accumulated at √s= 7 and 8 TeV are very similar, they are treated together. In general, the width of the resolution function is much smaller than the bin width, i.e. the results are not affected by bin-to-bin migration. The exception to this is a small fraction of events with 2.0< pJ/ψ T<2.5 GeV/c, where the resolution for |∆φ∗| and |∆η∗|is close to half of the bin-width. The normalized differential production cross-sections are compared with expectations from Powheg [66–69] and Pythia [59,65,75] using the parton distribution functions from CT09MCS [90], CTEQ6L1 [91] and CTEQ6.6 [92] for the samples produced with Powheg,Pythia 6 and Pythia 8, respectively. Since no visible difference between Pythia 6 and Pythia 8 samples are found, they are combined. For the Powheg samples – 8 – JHEP11(2017)030 0 0.2 0.4 0.6 0.8 1 0 0.5 1 1.5 2 2.5 0 0.2 0.4 0.6 0.8 1 0 0.5 1 1.5 2 2.5 0 0.5 1 1.5 2 2.5 0 0.2 0.4 0.6 0.8 1 1.2 1.4 0 0.5 1 1.5 2 2.5 0 0.2 0.4 0.6 0.8 1 1.2 1.4 0 0.5 1 1.5 2 2.5 0 0.2 0.4 0.6 0.8 1 1.2 1.4 0 0.5 1 1.5 2 2.5 0 0.2 0.4 0.6 0.8 1 1.2 1.4 π σ dσ d|∆φJ/ψ| π σ dσ d|∆φJ/ψ| 1 σ dσ d|∆ηJ/ψ| 1 σ dσ d|∆ηJ/ψ| 1 σ dσ d|∆yJ/ψ| 1 σ dσ d|∆yJ/ψ|  ∆φJ/ψ /π  ∆φJ/ψ /π  ∆ηJ/ψ  ∆ηJ/ψ   ∆yJ/ψ  ∆yJ/ψ  LHCb √s= 7,8 TeV a) b) c) d) e) f) Powheg Pythia uncorrelated b¯ b Figure 7. Normalized differential production cross-sections (points with error bars) for pJ/ψ T>2 GeV/c (left) and pJ/ψ T>3 GeV/c (right) data for a,b)  ∆φJ/ψ /π, c,d)  ∆ηJ/ψ , and e,f)  ∆yJ/ψ , together with the Powheg (orange line) and Pythia (green band) predictions. The expectations for uncorrelated bb production are shown by the dashed magenta line. The uncertainties in the Powheg and Pythia predictions due to the choice of factorization and renormalization scales are shown as orange cross-hatched and green solid areas, respectively. well with the model of uncorrelated bb production for  ∆ηJ/ψ and  ∆yJ/ψ , supporting the hypothesis of large effective decorrelation of the produced heavy quarks. – 15 – JHEP11(2017)030 0 0.2 0.4 0.6 0.8 1 0 0.5 1 1.5 2 2.5 3 3.5 0 0.2 0.4 0.6 0.8 1 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 0 0.5 1 1.5 2 2.5 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 0 0.5 1 1.5 2 2.5 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 0 0.5 1 1.5 2 2.5 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 0 0.5 1 1.5 2 2.5 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 π σ dσ d|∆φJ/ψ| π σ dσ d|∆φJ/ψ| 1 σ dσ d|∆ηJ/ψ| 1 σ dσ d|∆ηJ/ψ| 1 σ dσ d|∆yJ/ψ| 1 σ dσ d|∆yJ/ψ|  ∆φJ/ψ /π  ∆φJ/ψ /π  ∆ηJ/ψ  ∆ηJ/ψ   ∆yJ/ψ  ∆yJ/ψ  LHCb √s= 7,8 TeV a) b) c) d) e) f) Powheg Pythia uncorrelated b¯ b Figure 8. Normalized differential production cross-sections (points with error bars) for pJ/ψ T>5 GeV/c (left) and pJ/ψ T>7 GeV/c (right) data for a,b)  ∆φJ/ψ /π, c,d)  ∆ηJ/ψ , and e,f)  ∆yJ/ψ , together with the Powheg (orange line) and Pythia (green band) predictions. The expectations for uncorrelated bb production are shown by the dashed magenta line. The uncertainties in the Powheg and Pythia predictions due to the choice of factorization and renormalization scales are shown as orange cross-hatched and green solid areas, respectively. – 16 – JHEP11(2017)030 Open Access. This article is distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits any use, distribution and reproduction in any medium, provided the original author(s) and source are credited. References [1] LHCb collaboration, Measurements of prompt charm production cross-sections in pp collisions at √s= 5 TeV,JHEP 06 (2017) 147 [arXiv:1610.02230] [INSPIRE]. 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Kopecna12, P. Koppenburg43, A. Kosmyntseva32, S. Kotriakhova31, M. Kozeiha5, L. Kravchuk34, M. Kreps50, P. Krokovny36,w, F. Kruse10, W. Krzemien29, W. Kucewicz27,l, M. Kucharczyk27, V. Kudryavtsev36,w, A.K. Kuonen41, K. Kurek29, 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, T. Likhomanenko68, R. Lindner40, F. Lionetto42, V. Lisovskyi7, X. Liu3, D. Loh50, A. Loi16, I. Longstaff53, J.H. Lopes2, D. Lucchesi23,o, A. Luchinsky37, 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, A. Malinin68, T. Maltsev36,w, G. Manca16,f , G. Mancinelli6, P. Manning61, D. Marangotto22,q, J. Maratas5,v, J.F. Marchand4, U. Marconi15, C. Marin Benito38, M. Marinangeli41, P. Marino41, J. Marks12, G. Martellotti26, M. Martin6, M. Martinelli41, D. Martinez Santos39, F. Martinez Vidal70, D. Martins Tostes2, L.M. Massacrier7, A. Massafferri1, R. Matev40, A. Mathad50, Z. Mathe40, C. Matteuzzi21, A. Mauri42, E. Maurice7,b, B. Maurin41, A. Mazurov47, M. McCann55,40, A. McNab56, R. McNulty13, J.V. Mead54, B. Meadows59, C. Meaux6, 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¨acher10, I.A. Monroy66, S. Monteil5, M. Morandin23, 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. Nandi57, I. Nasteva2, M. Needham52, N. Neri22,40, S. Neubert12, 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. Onderwater71, A. Ossowska27, J.M. Otalora Goicochea2, P. Owen42, A. Oyanguren70, P.R. Pais41, A. Palano14,d, M. Palutan19,40, A. Papanestis51, M. Pappagallo14,d, L.L. Pappalardo17,g, W. Parker60, C. Parkes56, G. Passaleva18, A. Pastore14,d, M. Patel55, C. Patrignani15,e, A. Pearce40, A. Pellegrino43, G. Penso26, M. Pepe Altarelli40, S. Perazzini40, P. Perret5, L. Pescatore41, K. Petridis48, A. Petrolini20,h, A. Petrov68, M. Petruzzo22,q, E. Picatoste Olloqui38, B. Pietrzyk4, M. Pikies27, D. Pinci26, F. Pisani40, A. Pistone20,h, A. Piucci12, V. Placinta30, S. Playfer52, M. Plo Casasus39, F. Polci8, M. Poli Lener19, A. Poluektov50,36, I. Polyakov61, E. Polycarpo2, G.J. Pomery48, S. Ponce40, A. Popov37, D. Popov11,40, S. Poslavskii37, C. Potterat2, E. Price48, – 24 –