Forward production of Υ mesons in pp collisions at √s=7 and 8 TeV

JHEP11(2015)103 Published for SISSA by Springer Received:September 9, 2015 Accepted:October 9, 2015 Published:November 16, 2015 Forward production of Υ mesons in pp collisions at √s=7 and 8 TeV The LHCb collaboration E-mail: [email protected] Abstract: The production of Υ mesons in pp collisions at √s= 7 and 8 TeV is studied with the LHCb detector using data samples corresponding to an integrated luminosity of 1 fb−1and 2 fb−1respectively. The production cross-sections and ratios of cross-sections are measured as functions of the meson transverse momentum pand rapidity y, for p < 30 GeV/c and 2.0< y < 4.5. Keywords: Spectroscopy, Quarkonium, Hadron-Hadron Scattering, QCD, Hard scattering ArXiv ePrint: 1509.02372 Open Access, Copyright CERN, for the benefit of the LHCb Collaboration. Article funded by SCOAP3. doi:10.1007/JHEP11(2015)103 JHEP11(2015)103 Contents 1 Introduction 1 2 Detector and simulation 2 3 Selection and cross-section determination 3 4 Systematic uncertainties 5 5 Results 7 6 Summary 19 The LHCb collaboration 29 1 Introduction In high energy hadron collisions, the production of heavy quarkonium systems such as the bb states (Υ(1S), Υ(2S) and Υ(3S), represented generically as Υ in the following) probes the dynamics of the colliding partons and provides insight into the non-perturbative regime of quantum chromodynamics (QCD). Despite many models that have been proposed, a complete description of heavy quarkonium production is still not available. The effective theory of non-relativistic QCD (NRQCD) [1,2] provides the foundation for much of the current theoretical work. According to NRQCD, the production of heavy quarkonium factorises into two steps: a heavy quark-antiquark pair is first created at short distances, and subsequently evolves non-perturbatively into a quarkonium state. The NRQCD calculations include the colour-singlet (CS) and colour-octet (CO) matrix elements for the pertubative stage. The CS model [3,4], which provides a leading-order description of quarkonium production, underestimates the cross-section for single J/ψproduction at the Tevatron [5] at high pT, where pTis the component of the meson momentum transverse to the beam. To resolve this discrepancy, the CO mechanism was introduced [6]. The corresponding matrix elements were determined from the high-pTdata, as the CO cross-section decreases more slowly with pTthan that predicted by the CS model. More recent higher-order calculations [7–11] show better agreement between CS predictions and the experimental data [12], reducing the need for large CO contributions. The production of Υ mesons in proton-proton (pp) collisions can occur either directly in parton scattering or via feed down from the decay of heavier bottomonium states, such as χb[13– 18], or higher-mass Υ states, which complicates the theoretical description of bottomonium production [19,20]. – 1 – JHEP11(2015)103 The production of the Υ mesons has been studied using pp collision data taken at √s= 2.76, 7 and 8 TeV by the LHCb [21–23], ALICE [24], ATLAS [25] and CMS [26,27] experiments in different kinematic regions. The existing LHCb measurements of these quantities were performed at √s= 7 TeV with a data sample collected in 2010 corresponding to an integrated luminosity of 25 pb−1, and at √s= 8 TeV for early 2012 data using 50 pb−1. Both measurements were differential in pTand yof the Υ mesons in the ranges 2.0< y < 4.5 and pT<15 GeV/c. Based on these measurements, an increase of the production cross-section in excess of 30% between √s= 7 and 8 TeV was observed, which is larger than the increase observed for other quarkonium states such as the J/ψ[23,28] and larger than the expectations from NRQCD [11]. In this paper we report on the measurement of the inclusive production cross-sections of the Υ states at √s= 7 and 8 TeV and the ratios of these cross-sections. The Υ cross-section measurement is performed using a data sample corresponding to the complete LHCb Run 1 data set with integrated luminosities of 1 fb−1and 2 fb−1, accumulated at √s= 7 and 8 TeV, respectively. These samples are independent from those used in the previous analyses [22, 23]. The increased size of the data sample results in a better statistical precision and allows the measurements to be extended up to pTvalues of 30 GeV/c. 2 Detector and simulation The LHCb detector [29,30] 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, 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, the impact parameter, is measured with a resolution of (15 + 29/pT)µm, where pTis 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 [31]. The online event selection is performed by a trigger [32], 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. At the hardware stage, events for this analysis are selected by requiring dimuon candidates with a product of their pTvalues exceeding 1.7 (2.6) (GeV/c)2for data collected at √s= 7 (8) TeV. In the subsequent software trigger, two well-reconstructed tracks are required to have hits in the muon system, pT>500 MeV/c,p > 6 GeV/c and to form a common vertex. Only events with a dimuon candidate with a mass mµ+µ−>4.7 GeV/c2are retained for further analysis. In the offline selection, trigger decisions are associated with reconstructed particles. Se- – 2 – JHEP11(2015)103 lection requirements can therefore be made on the trigger selection itself and on whether the decision was due to the signal candidate, the other particles produced in the pp collision, or a combination of both. In the simulation, pp collisions are generated using Pythia 6 [33] with a specific LHCb configuration [34]. Decays of hadronic particles are described by EvtGen [35], in which final-state radiation is generated using Photos [36]. The interaction of the generated particles with the detector, and its response, are implemented using the Geant4 toolkit [37] as described in ref. [39]. 3 Selection and cross-section determination The event selection is based on the criteria described in the previous LHCb Υ analyses [21– 23] but slightly modified to improve the signal-to-background ratio. It includes selection criteria that ensure good quality track reconstruction [40], muon identification [41], and the requirement of a good fit quality for the dimuon vertex, where the associated primary vertex position is used as a constraint in the fit [42]. In addition, the muon candidates are required to have 1 < pT<25 GeV/c, 10 <p<400 GeV/c and pseudorapidity within the region 2.0<η<4.5. The differential cross-section for the production of an Υ meson decaying into a muon pair is BΥ×d2 dpTdyσ(pp →ΥX) ≡1 ∆pT∆yσΥ→µ+µ− bin =1 ∆pT∆y NΥ→µ+µ− L,(3.1) where BΥis the branching fraction of the Υ →µ+µ−decay, ∆yand ∆pTare the rapidity and pTbin sizes, σΥ→µ+µ− bin is a production cross-section for Υ →µ+µ−events in the given (pT, y) bin, NΥ→µ+µ−is the efficiency-corrected number of Υ →µ+µ−decays and Lis the integrated luminosity. Given the sizeable uncertainty on the dimuon branching fractions of the Υ mesons [43], the measurement of the production cross-section multiplied by the dimuon branching fraction is presented, as in previous LHCb measurements [21–23]. A large part of the theoretical and experimental uncertainties cancel in the ratios of production cross-sections of various Υ mesons, defined for a given (pT, y) bin as Ri,j≡σΥ(iS)→µ+µ− bin σΥ(jS)→µ+µ− bin =NΥ(iS)→µ+µ− NΥ(jS)→µ+µ− .(3.2) The evolution of the production cross-sections as a function of pp collision energy is studied using the ratio R8/7≡ σΥ→µ+µ− bin √s=8 TeV σΥ→µ+µ− bin √s=7 TeV .(3.3) The signal yields NΥ→µ+µ−in each (pT, y) bin are determined from an unbinned extended maximum likelihood fit to the dimuon mass spectrum of the selected candidates within the range 8.5< mµ+µ−<12.5 GeV/c2. The correction for efficiency is embedded – 3 – JHEP11(2015)103 √s= 7 TeV √s= 8 TeV NΥ(1S)→µ+µ−(2639.8±3.7) ·103(6563.1±6.3) ·103 NΥ(2S)→µ+µ−(667.3±2.2) ·103(1674.3±3.5) ·103 NΥ(3S)→µ+µ−(328.8±1.5) ·103(786.6±2.6) ·103 Table 1. Efficiency-corrected signal yields for data samples accumulated at √s= 7 and 8 TeV summed over the full kinematic range pT<30 GeV/c, 2.0< y < 4.5. The uncertainties are statistical only. in the fit procedure. Each dimuon candidate is given a weight calculated as 1/εtot, where εtot is the total efficiency, which is determined for each Υ →µ+µ−candidate as εtot =εrec&sel ×εtrg ×εµID,(3.4) where εrec&sel is the reconstruction and selection efficiency, εtrg is the trigger efficiency and εµID is the efficiency of the muon identification criteria. The efficiencies εrec&sel and εtrg are determined using simulation, and corrected using data-driven techniques to account for small differences in the muon reconstruction efficiency between data and simulation [40,41]. The efficiency of the muon identification criteria εµID is measured directly from data using a large sample of low-background J/ψ→µ+µ−events. All efficiencies are evaluated as functions of the muon and dimuon kinematics. The mean total efficiency εtotreaches a maximum of about 45% for the region 15 < pT<20 GeV/c, 3.0< y < 3.5, and drops down to 10% at high pTand large y, with the average efficiency being about 30%. In each (pT, y) bin, the dimuon mass distribution is described by the sum of three Crystal Ball functions [44], one for each of the Υ(1S), Υ(2S) and Υ(3S) signals, and the product of an exponential function with a second-order polynomial for the combinatorial background. The mean value and the resolution of the Crystal Ball function describing the mass distribution of the Υ(1S) meson are free fit parameters. For the Υ(2S) and Υ(3S) mesons the mass differences m(Υ(2S)) −m(Υ(1S)) and m(Υ(3S)) −m(Υ(1S)) are fixed to the known values [43], while the resolutions are fixed to the value of the resolution of the Υ(1S) signal, scaled by the ratio of the masses of the Υ(2S) and Υ(3S) to the Υ(1S) meson. The tail parameters of the Crystal Ball function describing the radiative tail are fixed from studies of simulated samples. The fits are performed independently on the efficiency-corrected dimuon mass distributions in each (pT,y) bin. As an example, figure 1shows the results of the fits in the region 3 < pT<4 GeV/c and 3.0< y < 3.5. For each bin the position and the resolution of the Υ(1S) signal is found to be consistent between √s= 7 and 8 TeV data sets. The resolution varies between 33 MeV/c2in the region of low pTand small rapidity and 90 MeV/c2for the high pTand large yregion, with the average value being close to 42 MeV/c2. The total signal yields are obtained by summing the signal yields over all (pT, y) bins and are summarised in table 1. – 4 – JHEP11(2015)103 LHCb √s= 7 TeV 3< pT<4 GeV/c 3.0< y < 3.5 LHCb √s= 8 TeV 3< pT<4 GeV/c 3.0< y < 3.5 Candidates/(10 MeV/c2) Candidates/(10 MeV/c2) mµ+µ−GeV/c2mµ+µ−GeV/c2 Figure 1. Efficiency-corrected dimuon mass distributions for (left) √s= 7 TeV and (right) √s= 8 TeV samples in the region 3 < pT<4 GeV/c, 3.0< y < 3.5. The thick dark yellow solid curves show the result of the fits, as described in the text. The three peaks, shown with thin magenta solid lines, correspond to the Υ(1S), Υ(2S) and Υ(3S) signals (left to right). The background component is indicated with a blue dashed line. To show the signal peaks clearly, the range of the dimuon mass shown is narrower than that used in the fit. Source σΥ→µ+µ− bin Ri,jσΥ→µ+µ−R8/7 Fit model and range 0.1−4.8 0.1−2.9 0.1 — Efficiency correction 0.2−0.6 0.1−1.1 0.4 — Efficiency uncertainty 0.2−0.3 — 0.2 0.3 Muon identification 0.3−0.5 — 0.3 0.2 Data-simulation agreement Radiative tails 1.0 — 1.0 — Selection efficiency 1.0 0.5 1.0 0.5 Tracking efficiency 0.5⊕(2 ×0.4) — 0.5⊕(2 ×0.4) — Trigger efficiency 2.0 — 2.0 1.0 Luminosity 1.7 (√s= 7 TeV) —1.7 (√s= 7 TeV) 1.4 1.2 (√s= 8 TeV) 1.2 (√s= 8 TeV) Table 2. Summary of relative systematic uncertainties (in %) for the differential production crosssections, their ratios, integrated cross-sections and the ratios R8/7. The ranges indicate variations depending on the (pT, y) bin and the Υ state. 4 Systematic uncertainties The systematic uncertainties are summarised in table 2, separately for the measurement of the cross-sections and of their ratios. The uncertainty related to the mass model describing the shape of the dimuon mass distribution is studied by varying the fit range and the signal and background parametri- – 5 – JHEP11(2015)103 sation used in the fit model. The fit range is varied by moving the upper edge from 12.5 to 11.5 GeV/c2; the degree of the polynomial function used in the estimation of the background is varied between zeroth and the third order. Also the tail parameters of the Crystal Ball function are allowed to vary in the fit. In addition, the constraints on the difference in the Υ signal peak positions are removed for all bins with high signal yields. The maximum relative difference in the number of signal events is taken as a systematic uncertainty arising from the choice of the fit model. As an alternative to the determination of the signal yields from efficiency-corrected data, the method employed in ref. [21] is used. In this method the efficiency-corrected yields for each (pT, y) bin are calculated using the sPlot technique [45]. The difference between this method and the nominal one is taken as a systematic uncertainty on the efficiency correction. Reconstruction, selection and trigger efficiencies in eq. (3.4) are obtained using simulated samples. The uncertainties due to the finite size of these samples are propagated to the measurement using a large number of pseudoexperiments. The same technique is used for the propagation of the uncertainties on the muon identification efficiency determined from large low-background samples of J/ψ→µ+µ−decays. Several systematic uncertainties are assigned to account for possible imperfections in the simulated samples. The possible mismodelling of the bremsstrahlung simulation for the radiative tail and its effect on the signal shape has been estimated in previous LHCb analyses [23] and leads to an additional uncertainty of 1.0% on the cross-section. Good agreement between data and simulation is observed for all variables used in the selection. The small differences seen would affect the efficiencies by less than 1.0%, which is conservatively taken as the systematic uncertainty to account for the disagreement between data and simulation. The efficiency is corrected using data-driven techniques to account for small differences in the tracking efficiency between data and simulation [40,41]. The uncertainty in the correction factor is propagated to the cross-section measurement using pseudoexperiments and results in a global 0.5% systematic uncertainty plus an additional uncertainty of 0.4% per track. The systematic uncertainty associated with the trigger requirements is assessed by studying the performance of the dimuon trigger for Υ(1S) events selected using the single muon high-pTtrigger [32] in data and simulation. The comparison is perfomed in bins of the Υ(1S) meson transverse momentum and rapidity and the largest observed difference of 2.0% is assigned as the systematic uncertainty associated with the imperfection of trigger simulation. The luminosity measurement was calibrated during dedicated data taking periods, using both van der Meer scans [46] and a beam-gas imaging method [47,48]. The absolute luminosity scale is determined with 1.7 (1.2)% uncertainty for the sample collected at √s= 7 (8) TeV, of which the beam-gas resolution, the spread of the measurements and the detector alignment are the largest contributions [48–50]. The ratio of absolute luminosities for samples accumulated at √s= 7 and 8 TeV is known with a 1.4% uncertainty. – 6 – JHEP11(2015)103 The total systematic uncertainty in each (pT, y) bin is the sum in quadrature of the individual components described above. For the integrated production cross-section the systematic uncertainty is estimated by taking into account bin-to-bin correlations. Several systematic uncertainties cancel or significantly reduce in the measurement of the ratios Ri,jand R8/7, as shown in table 2. The production cross-sections are measured at centre-of-mass energies of 7 and 8 TeV, where the actual beam energy for pp collisions is known with a precision of 0.65% [51]. Assuming a linear dependence of the production cross-section on the pp collision energy, and using the measured production cross-sections at √s= 7 (8) TeV, the change in the production cross-section due to the imprecise knowledge of the beam energy is estimated to be 1.4 (1.2)%. The effect is strongly correlated between √s= 7 and 8 TeV data and will therefore mostly cancel in the measurement of the ratio of cross-sections at the two energies. The efficiency is dependent on the polarisation of the Υ mesons. The polarisation of the Υ mesons produced in pp collisions at √s= 7 TeV at high pTand central rapidity has been studied by the CMS collaboration [52] in the centre-of-mass helicity, Collins-Soper [53] and the perpendicular helicity frames. No evidence of significant transverse or longitudinal polarisation has been observed for the region 10 < pT<50 GeV/c,|y|<1.2. Therefore, results are quoted under the assumption of unpolarised production of Υ mesons and no corresponding systematic uncertainty is assigned on the cross-section. Under the assumption of transversely polarised Υ mesons with λϑ= 0.2 in the LHCb kinematic region,1the total production cross-section would result in an increase of 3%, with the largest local increase of around 6% occuring in the low pTregion (pT<3 GeV/c), both for small (y < 2.5) and large (y > 4.0) rapidities. 5 Results The double-differential production cross-sections multiplied by the dimuon branching fractions for the Υ mesons are shown in figure 2. The corresponding production cross-section σΥ→µ+µ− bin in (pT, y) bins are presented in tables 3,4and 5for √s= 7 TeV and tables 6,7 and 8for √s= 8 TeV. The cross-sections integrated over yas a function of pTand integrated over pTas a function of rapidity are shown in figures 3and 4, respectively. The transverse momentum spectra are fit using a Tsallis function [54] dσ pTdpT∝1 + Ekin T n T −n ,(5.1) where Ekin T≡qm2 Υ+p2 T−mΥis the transverse kinetic energy, the power nand the temperature parameter Tare free parameters, and mΥis the known mass of a Υ meson [43]. This function has a power-law asymptotic behaviour ∝p−n Tfor high pTas expected for hard scattering processes. It has been successfully applied to fit pTspectra [55–58] in wide ranges of particle species, processes and kinematics. A fit with the Tsallis distribution for 1The CMS measurements for Υ(1S) mesons are consistent with small transverse polarisation in the helicity frame with the central values for the polarisation parameter 0 .λϑ.0.2 [52]. – 7 – JHEP11(2015)103 d2 dpTdyσΥ(1S)→µ+µ−hpb GeV/c i d2 dpTdyσΥ(1S)→µ+µ−hpb GeV/c i d2 dpTdyσΥ(2S)→µ+µ−hpb GeV/c i d2 dpTdyσΥ(2S)→µ+µ−hpb GeV/c i d2 dpTdyσΥ(3S)→µ+µ−hpb GeV/c i d2 dpTdyσΥ(3S)→µ+µ−hpb GeV/c i •2.0< y < 2.5 2.5< y < 3.0 H3.0< y < 3.5 N3.5< y < 4.0 4.0< y < 4.5 •2.0< y < 2.5 2.5< y < 3.0 H3.0< y < 3.5 N3.5< y < 4.0 4.0< y < 4.5 •2.0< y < 2.5 2.5< y < 3.0 H3.0< y < 3.5 N3.5< y < 4.0 4.0< y < 4.5 •2.0< y < 2.5 2.5< y < 3.0 H3.0< y < 3.5 N3.5< y < 4.0 4.0< y < 4.5 •2.0< y < 2.5 2.5< y < 3.0 H3.0< y < 3.5 N3.5< y < 4.0 4.0< y < 4.5 •2.0< y < 2.5 2.5< y < 3.0 H3.0< y < 3.5 N3.5< y < 4.0 4.0< y < 4.5 LHCb √s= 7 TeV LHCb √s= 8 TeV LHCb √s= 7 TeV LHCb √s= 8 TeV LHCb √s= 7 TeV LHCb √s= 8 TeV pT[GeV/c]pT[GeV/c] pT[GeV/c]pT[GeV/c] pT[GeV/c]pT[GeV/c] Figure 2. Double differential cross-sections d2 dpTdyσΥ→µ+µ − for (top) Υ(1S), (middle) Υ(2S) and (bottom) Υ(3S) at (left) √s= 7 TeV and (right) √s= 8 TeV. The error bars indicate the sum in quadrature of the statistical and systematic uncertainties. The rapidity ranges 2.0< y < 2.5, 2.5< y < 3.0, 3.0< y < 3.5, 3.5< y < 4.0 and 4.0< y < 4.5 are shown with red filled circles, blue open squares, cyan downward triangles, magenta upward triangles and green diamonds, respectively. Some data points are displaced from the bin centres to improve visibility. – 8 – JHEP11(2015)103 pT[GeV/c] 2.0< y < 2.5 2.5< y < 3.0 3.0< y < 3.5 3.5< y < 4.0 4.0< y < 4.5 0−1 3.30 ±0.17 ±0.09 3.29 ±0.10 ±0.04 2.72 ±0.09 ±0.05 2.42 ±0.08 ±0.02 1.47 ±0.11 ±0.03 1−2 8.19 ±0.27 ±0.01 8.45 ±0.16 ±0.06 7.18 ±0.14 ±0.02 5.83 ±0.13 ±0.13 3.43 ±0.17 ±0.11 2−3 10.73 ±0.30 ±0.14 11.16 ±0.18 ±0.07 9.05 ±0.15 ±0.14 7.56 ±0.14 ±0.03 4.94 ±0.19 ±0.05 3−4 12.44 ±0.31 ±0.07 12.00 ±0.18 ±0.04 9.99 ±0.16 ±0.08 7.98 ±0.15 ±0.10 4.69 ±0.18 ±0.08 4−5 11.37 ±0.30 ±0.07 11.42 ±0.18 ±0.01 9.51 ±0.15 ±0.05 7.70 ±0.14 ±0.05 4.48 ±0.17 ±0.20 5−6 10.06 ±0.27 ±0.04 10.21 ±0.17 ±0.07 8.53 ±0.14 ±0.09 6.64 ±0.13 ±0.12 3.68 ±0.15 ±0.01 6−7 9.35 ±0.26 ±0.16 8.60 ±0.15 ±0.03 7.36 ±0.13 ±0.07 5.66 ±0.12 ±0.12 3.13 ±0.14 ±0.01 7−8 7.83 ±0.23 ±0.06 7.48 ±0.14 ±0.05 6.14 ±0.11 ±0.08 4.79 ±0.11 ±0.04 2.48 ±0.12 ±0.04 8−9 6.66 ±0.21 ±0.05 6.13 ±0.12 ±0.08 4.91 ±0.10 ±0.03 3.64 ±0.09 ±0.01 1.75 ±0.11 ±0.05 9−10 5.29 ±0.19 ±0.07 4.81 ±0.11 ±0.04 3.99 ±0.09 ±0.02 3.00 ±0.08 ±0.05 1.24 ±0.09 ±0.01 10 −11 4.11 ±0.17 ±0.08 3.98 ±0.09 ±0.08 3.19 ±0.07 ±0.03 2.42 ±0.07 ±0.05 1.10 ±0.09 ±0.07 11 −12 3.27 ±0.15 ±0.09 3.16 ±0.08 ±0.04 2.49 ±0.06 ±0.07 1.73 ±0.06 ±0.02 0.69 ±0.07 ±0.02 12 −13 2.91 ±0.13 ±0.04 2.65 ±0.07 ±0.04 1.95 ±0.06 ±0.02 1.41 ±0.06 ±0.02 0.46 ±0.07 ±0.01 13 −14 2.41 ±0.12 ±0.04 2.07 ±0.06 ±0.03 1.52 ±0.05 ±0.04 1.05 ±0.05 ±0.02 0.60 ±0.09 ±0.02 14 −15 1.93 ±0.11 ±0.07 1.67 ±0.06 ±0.04 1.17 ±0.04 ±0.01 0.83 ±0.04 ±0.03 15 −16 1.52 ±0.09 ±0.04 1.21 ±0.05 ±0.02 0.90 ±0.04 ±0.02 0.61 ±0.04 ±0.01 0.46 ±0.08 ±0.01 16 −17 1.10 ±0.08 ±0.02 0.97 ±0.04 ±0.01 0.76 ±0.04 ±0.01 0.42 ±0.03 ±0.02 17 −18 0.89 ±0.07 ±0.02 0.77 ±0.04 ±0.01 0.56 ±0.03 ±0.01 0.40 ±0.032 ±0.01 18 −19 0.79 ±0.06 ±0.01 0.58 ±0.03 ±0.01 0.43 ±0.03 ±0.01 0.31 ±0.029 ±0.01 19 −20 0.59 ±0.05 ±0.01 0.49 ±0.03 ±0.01 0.32 ±0.02 ±0.01 0.20 ±0.02 ±0.01 20 −21 0.84 ±0.06 ±0.01 0.73 ±0.04 ±0.02 0.46 ±0.03 ±0.01 0.46 ±0.04 ±0.02 21 −22 22 −23 0.51 ±0.05 ±0.01 0.46 ±0.03 ±0.04 0.32 ±0.02 ±0.01 23 −24 24 −25 0.34 ±0.04 ±0.01 0.30 ±0.02 ±0.01 0.21 ±0.03 ±0.01 25 −26 26 −27 0.52 ±0.05 ±0.02 0.18 ±0.02 ±0.01 0.20 ±0.02 ±0.01 27 −28 28 −29 0.12 ±0.02 ±0.01 29 −30 Table 8. Production cross-section σΥ(3S)→µ+µ − bin [pb] in (pT, y) bins for √s= 8 TeV. The first uncertainties are statistical and the second are the uncorrelated component of the systematic uncertainty. The overall correlated systematic uncertainty is 2.8% and is not included in the numbers in the table. The horizontal lines indicate the bin boundaries. – 15 – JHEP11(2015)103 √s T [GeV] n Υ(1S) 7 TeV 8 TeV 1.19 ±0.04 1.20 ±0.04 8.01 ±0.33 7.71 ±0.27 Υ(2S) 7 TeV 8 TeV 1.33 ±0.05 1.37 ±0.05 7.57 ±0.41 7.53 ±0.34 Υ(3S) 7 TeV 8 TeV 1.53 ±0.07 1.63 ±0.06 7.85 ±0.56 8.23 ±0.51 Table 9. Results of the fits to the transverse momentum spectra of Υ mesons using the Tsallis function in the reduced range 6 < pT<30 GeV/c. pT<30 GeV/c pT<15 GeV/c √s= 7 TeV √s= 8 TeV √s= 7 TeV √s= 8 TeV σΥ(1S)→µ+µ−2510 ±3±80 3280 ±3±100 2460 ±3±80 3210 ±3±90 σΥ(2S)→µ+µ−635 ±2±20 837 ±2±25 614 ±2±20 807 ±2±24 σΥ(3S)→µ+µ−313 ±2±10 393 ±1±12 298 ±1±10 373 ±1±11 Table 10. The production cross-section σΥ→µ+µ − (in pb) for Υ mesons in the full kinematic range pT<30 GeV/c (left two columns), and reduced range pT<15 GeV/c (right two columns), for 2.0< y < 4.5. The first uncertainties are statistical and the second systematic. kinematic range 2.0< y < 4.5, is presented in figure 4. The quality of the fit is good for all cases. The integrated production cross-sections multiplied by the dimuon branching fractions in the full range pT<30 GeV/c and 2.0< y < 4.5 at √s= 7 and 8 TeV are reported in table 10, where the first uncertainties are statistical and the second systematic. The same measurements are also shown integrated over the reduced range pT<15 GeV/c in the same rapidity range, to allow the comparison with previous measurements [22,23]. The ratios of integrated production cross-section R8/7are presented in table 11 for the full (pT<30 GeV/c) and reduced (pT<15 GeV/c) ranges. The results for the reduced range are consistent with the previous measurements, confirming the increase of the bottomonium production cross-section of approximately 30% when the centre-of-mass energy increases from √s= 7 to 8 TeV [22,23]. The ratios R8/7as a function of pTintegrated over the region 2.0< y < 4.5 are shown in figure 5a. The ratios are fitted with a linear function. The fit quality is good, with a pvalue exceeding 35% for all cases, and the slopes are found to be 10.8±0.6, 9.5±1.2 and 9.8±1.6 (in units of 10−3/(GeV/c)) for Υ(1S), Υ(2S) and Υ(3S), respectively. The measurements are compared with the NRQCD theory predictions [11] in the same kinematic range, where only uncertainties from the CO long distance matrix elements are considered since most other uncertainties are expected to cancel in the ratio. The theory predictions are independent on the Υ state and are consistently lower than the measurements. – 16 – JHEP11(2015)103 (a) (b) R8/7(pT) R8/7(y) LHCb 2.0< y < 4.5 LHCb pT<30 GeV/c pT[GeV/c]y •Υ(1S) Υ(2S) Υ(3S) •Υ(1S) Υ(2S) Υ(3S) Figure 5. Ratios of the differential cross-sections (left) d dpTσΥ→µ+µ − and (right) d dyσΥ→µ+µ − at √s= 8 and 7 TeV for (red solid circles) Υ(1S), (blue open squares) Υ(2S) and (green solid diamonds) Υ(3S). On the left hand plot, the results of the fit with a linear function are shown with straight thin red solid, blue dotted and green dashed lines. In the same plot, the next-to-leading order NRQCD theory predictions [11] are shown as a thick line. On the right hand plot, the curved red solid, blue dotted and greed dashed lines show the CO model predictions [63,64] with the normalisation fixed from the fits in figure 4for Υ(1S), Υ(2S) and Υ(3S) mesons, respectively. Some data points are displaced from the bin centres to improve visibility. pT<30 GeV/c pT<15 GeV/c Υ(1S) 1.307 ±0.002 ±0.025 1.304 ±0.002 ±0.024 Υ(2S) 1.319 ±0.005 ±0.025 1.315 ±0.005 ±0.024 Υ(3S) 1.258 ±0.007 ±0.024 1.254 ±0.007 ±0.023 Table 11. The ratio of production cross-sections for Υ mesons at √s= 8 to that at √s= 7 TeV in the full kinematic range pT<30 GeV/c (left) and reduced range pT<15 GeV/c (right) for 2.0< y < 4.5. The first uncertainties are statistical and the second systematic. The ratio R8/7as a function of rapidity, integrated over the region pT<30 GeV/c is shown in figure 5b. The ratios are compared with the expectations from the CO mechanism [63,64] with normalisation factors fixed from the fits of figure 4. The trend observed in data does not agree with the pure CO model. It can be noted that also for open beauty hadrons the differential cross-sections exhibit a larger rise as a function of √sat smaller rapidities [55], while the FONLL calculations [66] predict this behaviour towards larger rapidity. The ratios Ri,jat √s= 7 and 8 TeV are reported in figure 6and tables 12,13,14 and 15 as a function of pTfor different rapidity bins. The same ratios as a function of pTintegrated over rapidity, and as a function of yintegrated over pT, are shown in figure 7. The ratios Ri,jshow little dependence on rapidity and increase as a function of pT, in agreement with previous observations by LHCb [22,23], ATLAS [25] and CMS [26] – 17 – JHEP11(2015)103 R2,1 R2,1 R3,1 R3,1 R3,2 R3,2 •2.0< y < 2.5 2.5< y < 3.0 H3.0< y < 3.5 N3.5< y < 4.0 4.0< y < 4.5 •2.0< y < 2.5 2.5< y < 3.0 H3.0< y < 3.5 N3.5< y < 4.0 4.0< y < 4.5 •2.0< y < 2.5 2.5< y < 3.0 H3.0< y < 3.5 N3.5< y < 4.0 4.0< y < 4.5 •2.0< y < 2.5 2.5< y < 3.0 H3.0< y < 3.5 N3.5< y < 4.0 4.0< y < 4.5 •2.0< y < 2.5 2.5< y < 3.0 H3.0< y < 3.5 N3.5< y < 4.0 4.0< y < 4.5 •2.0< y < 2.5 2.5< y < 3.0 H3.0< y < 3.5 N3.5< y < 4.0 4.0< y < 4.5 LHCb √s= 7 TeV LHCb √s= 8 TeV LHCb √s= 7 TeV LHCb √s= 8 TeV LHCb √s= 7 TeV LHCb √s= 8 TeV pT[GeV/c]pT[GeV/c] pT[GeV/c]pT[GeV/c] pT[GeV/c]pT[GeV/c] Figure 6. The production ratios Ri,jfor (top) Υ(2S) to Υ(1S), (middle) Υ(3S) to Υ(1S), and (bottom) Υ(3S) to Υ(2S), measured with data collected at (left) √s= 7 TeV and (right) √s= 8 TeV. The error bars indicate the sum in quadrature of the statistical and systematic uncertainties. The rapidity ranges 2.0< y < 2.5, 2.5≤y < 3.0, 3.0≤y < 3.5, 3.5≤y < 4.0 and 4.0≤y < 4.5 are shown with red circles, blue squares, cyan downward triangles, magenta upward triangles and green diamonds, respectively. Some data points are displaced from the bin centres to improve visibility. – 18 – JHEP11(2015)103 Ri,j(pT) Ri,j(pT) Ri,j(y) Ri,j(y) LHCb √s= 7 TeV 2.0< y < 4.5 LHCb √s= 8 TeV 2.0< y < 4.5 LHCb √s= 7 TeV pT<30 GeV/c LHCb √s= 8 TeV pT<30 GeV/c pT[GeV/c]pT[GeV/c] y y •R2,1 R3,1 R3,2 •R2,1 R3,1 R3,2 •R2,1 R3,1 R3,2 •R2,1 R3,1 R3,2 Figure 7. The production ratios (red solid circles) R2,1, (blue open squares) R3,1and (green solid diamonds) R3,2for (left) √s= 7 TeV and (right) √s= 8 TeV data, integrated over the (top) 2.0< y < 4.5 region and (bottom) pT<30 GeV/c region. at √s= 7 TeV. The ratios of integrated cross-sections Ri,jat √s= 7 and 8 TeV are reported in table 16, for the full and the reduced pTkinematic regions. All ratios Ri,j agree with previous LHCb measurements. The ratio R2,1agrees with the estimates of 0.27 from refs. [64,69], while R3,1significantly exceeds the expected value of 0.04 [64,69] but agrees with the range 0.14 −0.22, expected for the hypothesis of a large admixture of a hybrid quarkonium state in the Υ(3S) meson state [69]. 6 Summary The forward production of Υ mesons is studied in pp collisions at centre-of-mass energies of 7 and 8 TeV using data samples corresponding to integrated luminosities of 1 fb−1and 2 fb−1respectively, collected with the LHCb detector. The double differential production cross-sections are measured as a function of meson transverse momenta and rapidity for the range pT<30 GeV/c, 2.0< y < 4.5. The measured increase in the production cross-sections of Υ mesons between √s= 8 and 7 TeV significantly exceeds theory expecta- – 19 – JHEP11(2015)103 pT[GeV/c] 2.0< y < 2.5 2.5< y < 3.0 3.0< y < 3.5 3.5< y < 4.0 4.0< y < 4.5 0−1 0.223 ±0.010 ±0.002 0.218 ±0.006 ±0.001 0.211 ±0.006 ±0.001 0.210 ±0.007 ±0.004 0.214 ±0.015 ±0.005 1−2 0.202 ±0.006 ±0.002 0.213 ±0.004 ±0.001 0.209 ±0.004 ±0.001 0.212 ±0.004 ±0.001 0.225 ±0.010 ±0.001 2−3 0.229 ±0.006 ±0.001 0.216 ±0.003 ±0.001 0.215 ±0.003 ±0.001 0.220 ±0.004 ±0.001 0.218 ±0.009 ±0.004 3−4 0.243 ±0.006 ±0.004 0.224 ±0.003 ±0.001 0.228 ±0.003 ±0.001 0.231 ±0.004 ±0.001 0.231 ±0.009 ±0.001 4−5 0.241 ±0.006 ±0.001 0.241 ±0.004 ±0.001 0.241 ±0.004 ±0.001 0.245 ±0.004 ±0.003 0.247 ±0.010 ±0.002 5−6 0.255 ±0.007 ±0.002 0.241 ±0.004 ±0.001 0.244 ±0.004 ±0.001 0.252 ±0.005 ±0.001 0.277 ±0.012 ±0.001 6−7 0.265 ±0.008 ±0.003 0.262 ±0.005 ±0.001 0.260 ±0.005 ±0.002 0.267 ±0.006 ±0.001 0.279 ±0.014 ±0.004 7−8 0.291 ±0.009 ±0.003 0.279 ±0.006 ±0.002 0.280 ±0.006 ±0.002 0.277 ±0.007 ±0.003 0.287 ±0.017 ±0.003 8−9 0.316 ±0.011 ±0.002 0.298 ±0.007 ±0.001 0.300 ±0.007 ±0.002 0.308 ±0.009 ±0.002 0.307 ±0.021 ±0.005 9−10 0.308 ±0.012 ±0.002 0.313 ±0.008 ±0.001 0.307 ±0.008 ±0.003 0.314 ±0.011 ±0.004 0.323 ±0.028 ±0.002 10 −11 0.309 ±0.014 ±0.003 0.323 ±0.009 ±0.002 0.289 ±0.009 ±0.001 0.359 ±0.014 ±0.001 0.33 ±0.04 ±0.01 11 −12 0.333 ±0.017 ±0.004 0.328 ±0.011 ±0.003 0.329 ±0.011 ±0.001 0.337 ±0.015 ±0.002 0.38 ±0.06 ±0.01 12 −13 0.326 ±0.019 ±0.005 0.344 ±0.013 ±0.002 0.343 ±0.013 ±0.001 0.342 ±0.019 ±0.001 0.33 ±0.06 ±0.01 13 −14 0.392 ±0.025 ±0.005 0.379 ±0.015 ±0.001 0.392 ±0.017 ±0.001 0.397 ±0.023 ±0.002 0.37 ±0.08 ±0.01 14 −15 0.354 ±0.026 ±0.007 0.378 ±0.017 ±0.003 0.398 ±0.020 ±0.005 0.402 ±0.030 ±0.006 15 −16 0.45 ±0.04 ±0.01 0.418 ±0.022 ±0.002 0.353 ±0.021 ±0.001 0.377 ±0.033 ±0.004 0.31 ±0.11 ±0.01 16 −17 0.37 ±0.04 ±0.01 0.395 ±0.023 ±0.004 0.435 ±0.028 ±0.001 0.50 ±0.05 ±0.01 17 −18 0.42 ±0.04 ±0.01 0.457 ±0.031 ±0.001 0.408 ±0.031 ±0.001 0.44 ±0.05 ±0.01 18 −19 0.43 ±0.05 ±0.01 0.478 ±0.035 ±0.002 0.42 ±0.04 ±0.01 0.38 ±0.06 ±0.01 19 −20 0.49 ±0.06 ±0.01 0.51 ±0.04 ±0.01 0.42 ±0.04 ±0.01 0.51 ±0.09 ±0.01 20 −21 0.47 ±0.05 ±0.01 0.489 ±0.035 ±0.002 0.42 ±0.04 ±0.01 0.40 ±0.05 ±0.01 21 −22 22 −23 0.39 ±0.05 ±0.01 0.44 ±0.04 ±0.01 0.50 ±0.06 ±0.01 23 −24 24 −25 0.58 ±0.08 ±0.01 0.59 ±0.07 ±0.01 0.47 ±0.07 ±0.01 25 −26 26 −27 0.51 ±0.08 ±0.01 0.49 ±0.07 ±0.01 0.47 ±0.08 ±0.02 27 −28 28 −29 0.48 ±0.09 ±0.01 29 −30 Table 12. The ratio R2,1for √s= 7 TeV. The first uncertainties are statistical and the second are the uncorrelated component of the systematic uncertainties. The overall correlated systematic uncertainty is 0.7% and is not included in the numbers in the table. The horizontal lines indicate bin boundaries. – 20 – JHEP11(2015)103 pT[GeV/c] 2.0< y < 2.5 2.5< y < 3.0 3.0< y < 3.5 3.5< y < 4.0 4.0< y < 4.5 0−1 0.085 ±0.007 ±0.001 0.088 ±0.004 ±0.001 0.094 ±0.004 ±0.002 0.091 ±0.005 ±0.002 0.083 ±0.010 ±0.003 1−2 0.088 ±0.004 ±0.001 0.088 ±0.003 ±0.001 0.096 ±0.003 ±0.001 0.096 ±0.003 ±0.001 0.105 ±0.007 ±0.001 2−3 0.097 ±0.004 ±0.001 0.095 ±0.002 ±0.001 0.096 ±0.002 ±0.001 0.102 ±0.003 ±0.001 0.102 ±0.006 ±0.004 3−4 0.109 ±0.004 ±0.002 0.099 ±0.002 ±0.001 0.101 ±0.002 ±0.001 0.105 ±0.003 ±0.001 0.104 ±0.006 ±0.001 4−5 0.104 ±0.004 ±0.001 0.113 ±0.003 ±0.001 0.109 ±0.003 ±0.001 0.111 ±0.003 ±0.002 0.108 ±0.007 ±0.001 5−6 0.121 ±0.005 ±0.002 0.121 ±0.003 ±0.001 0.120 ±0.003 ±0.001 0.121 ±0.004 ±0.001 0.124 ±0.008 ±0.001 6−7 0.134 ±0.006 ±0.002 0.133 ±0.004 ±0.001 0.136 ±0.004 ±0.001 0.145 ±0.005 ±0.001 0.146 ±0.010 ±0.004 7−8 0.147 ±0.007 ±0.002 0.145 ±0.004 ±0.001 0.142 ±0.004 ±0.001 0.149 ±0.005 ±0.002 0.152 ±0.012 ±0.002 8−9 0.162 ±0.008 ±0.002 0.155 ±0.005 ±0.001 0.161 ±0.005 ±0.002 0.177 ±0.007 ±0.001 0.160 ±0.016 ±0.002 9−10 0.177 ±0.009 ±0.002 0.179 ±0.006 ±0.001 0.178 ±0.006 ±0.002 0.155 ±0.008 ±0.003 0.170 ±0.019 ±0.001 10 −11 0.184 ±0.011 ±0.001 0.193 ±0.007 ±0.001 0.173 ±0.007 ±0.001 0.204 ±0.010 ±0.001 0.168 ±0.026 ±0.013 11 −12 0.195 ±0.013 ±0.002 0.209 ±0.008 ±0.003 0.205 ±0.009 ±0.001 0.218 ±0.012 ±0.002 0.158 ±0.033 ±0.001 12 −13 0.217 ±0.016 ±0.003 0.231 ±0.010 ±0.001 0.202 ±0.010 ±0.001 0.207 ±0.014 ±0.001 0.18 ±0.05 ±0.01 13 −14 0.246 ±0.019 ±0.005 0.256 ±0.012 ±0.002 0.204 ±0.012 ±0.001 0.221 ±0.017 ±0.001 0.29 ±0.06 ±0.01 14 −15 0.244 ±0.022 ±0.003 0.260 ±0.014 ±0.002 0.261 ±0.015 ±0.004 0.234 ±0.022 ±0.003 15 −16 0.307 ±0.030 ±0.002 0.275 ±0.017 ±0.001 0.259 ±0.018 ±0.001 0.279 ±0.028 ±0.003 0.33 ±0.12 ±0.01 16 −17 0.290 ±0.032 ±0.003 0.260 ±0.018 ±0.002 0.307 ±0.023 ±0.002 0.33 ±0.04 ±0.01 17 −18 0.235 ±0.031 ±0.002 0.319 ±0.025 ±0.002 0.261 ±0.024 ±0.002 0.37 ±0.05 ±0.01 18 −19 0.27 ±0.04 ±0.01 0.340 ±0.028 ±0.001 0.300 ±0.031 ±0.001 0.33 ±0.06 ±0.01 19 −20 0.32 ±0.05 ±0.01 0.301 ±0.032 ±0.006 0.31 ±0.04 ±0.01 0.33 ±0.07 ±0.01 20 −21 0.39 ±0.05 ±0.01 0.335 ±0.028 ±0.002 0.331 ±0.032 ±0.002 0.35 ±0.05 ±0.01 21 −22 22 −23 0.41 ±0.05 ±0.01 0.304 ±0.034 ±0.002 0.38 ±0.05 ±0.01 23 −24 24 −25 0.32 ±0.06 ±0.01 0.47 ±0.06 ±0.01 0.28 ±0.06 ±0.01 25 −26 26 −27 0.45 ±0.08 ±0.01 0.36 ±0.06 ±0.01 0.33 ±0.06 ±0.02 27 −28 28 −29 0.34 ±0.08 ±0.01 29 −30 Table 13. The ratio R3,1for √s= 7 TeV. The first uncertainties are statistical and the second are the uncorrelated component of the systematic uncertainties. The overall correlated systematic uncertainty is 0.7% and is not included in the numbers in the table. The horizontal lines indicate bin boundaries. – 21 – JHEP11(2015)103 pT[GeV/c] 2.0< y < 2.5 2.5< y < 3.0 3.0< y < 3.5 3.5< y < 4.0 4.0< y < 4.5 0−1 0.211 ±0.007 ±0.003 0.213 ±0.004 ±0.002 0.216 ±0.004 ±0.001 0.212 ±0.005 ±0.001 0.223 ±0.010 ±0.002 1−2 0.221 ±0.004 ±0.001 0.217 ±0.003 ±0.001 0.215 ±0.003 ±0.001 0.218 ±0.003 ±0.001 0.208 ±0.006 ±0.003 2−3 0.222 ±0.004 ±0.001 0.217 ±0.002 ±0.001 0.218 ±0.002 ±0.001 0.220 ±0.003 ±0.001 0.225 ±0.006 ±0.001 3−4 0.235 ±0.004 ±0.001 0.231 ±0.002 ±0.001 0.228 ±0.002 ±0.001 0.237 ±0.003 ±0.002 0.232 ±0.006 ±0.002 4−5 0.238 ±0.004 ±0.001 0.243 ±0.003 ±0.001 0.234 ±0.002 ±0.001 0.240 ±0.003 ±0.001 0.249 ±0.007 ±0.005 5−6 0.251 ±0.005 ±0.001 0.253 ±0.003 ±0.001 0.250 ±0.003 ±0.001 0.249 ±0.003 ±0.002 0.263 ±0.007 ±0.001 6−7 0.274 ±0.005 ±0.003 0.270 ±0.003 ±0.001 0.268 ±0.003 ±0.002 0.265 ±0.004 ±0.002 0.270 ±0.009 ±0.001 7−8 0.294 ±0.006 ±0.002 0.282 ±0.004 ±0.002 0.278 ±0.004 ±0.002 0.279 ±0.005 ±0.002 0.287 ±0.010 ±0.002 8−9 0.313 ±0.007 ±0.002 0.295 ±0.004 ±0.002 0.292 ±0.004 ±0.001 0.296 ±0.006 ±0.001 0.308 ±0.014 ±0.006 9−10 0.312 ±0.008 ±0.002 0.306 ±0.005 ±0.001 0.304 ±0.005 ±0.001 0.322 ±0.007 ±0.002 0.316 ±0.018 ±0.001 10 −11 0.324 ±0.010 ±0.002 0.315 ±0.006 ±0.002 0.332 ±0.006 ±0.002 0.327 ±0.008 ±0.003 0.362 ±0.025 ±0.004 11 −12 0.352 ±0.012 ±0.004 0.329 ±0.007 ±0.002 0.328 ±0.007 ±0.004 0.331 ±0.010 ±0.003 0.343 ±0.032 ±0.004 12 −13 0.358 ±0.014 ±0.004 0.350 ±0.008 ±0.002 0.352 ±0.009 ±0.001 0.357 ±0.012 ±0.002 0.31 ±0.04 ±0.01 13 −14 0.384 ±0.016 ±0.003 0.350 ±0.009 ±0.001 0.365 ±0.010 ±0.004 0.370 ±0.015 ±0.002 0.34 ±0.04 ±0.01 14 −15 0.379 ±0.018 ±0.005 0.370 ±0.011 ±0.003 0.372 ±0.012 ±0.001 0.393 ±0.018 ±0.008 15 −16 0.399 ±0.021 ±0.005 0.393 ±0.013 ±0.002 0.390 ±0.015 ±0.003 0.407 ±0.022 ±0.003 0.45 ±0.07 ±0.01 16 −17 0.432 ±0.025 ±0.002 0.402 ±0.016 ±0.002 0.390 ±0.017 ±0.002 0.379 ±0.024 ±0.008 17 −18 0.389 ±0.027 ±0.003 0.421 ±0.018 ±0.001 0.439 ±0.021 ±0.001 0.416 ±0.032 ±0.005 18 −19 0.414 ±0.030 ±0.001 0.438 ±0.021 ±0.003 0.448 ±0.024 ±0.001 0.43 ±0.04 ±0.01 19 −20 0.44 ±0.04 ±0.01 0.416 ±0.023 ±0.001 0.368 ±0.024 ±0.007 0.42 ±0.04 ±0.01 20 −21 0.491 ±0.033 ±0.002 0.460 ±0.021 ±0.003 0.409 ±0.022 ±0.005 0.46 ±0.04 ±0.01 21 −22 22 −23 0.46 ±0.04 ±0.01 0.463 ±0.027 ±0.002 0.440 ±0.032 ±0.004 23 −24 24 −25 0.51 ±0.05 ±0.01 0.473 ±0.035 ±0.001 0.49 ±0.05 ±0.01 25 −26 26 −27 0.46 ±0.05 ±0.01 0.51 ±0.05 ±0.01 0.44 ±0.04 ±0.01 27 −28 28 −29 0.49 ±0.06 ±0.01 29 −30 Table 14. The ratio R2,1for √s= 8 TeV. The first uncertainties are statistical and the second are the uncorrelated component of the systematic uncertainties. The overall correlated systematic uncertainty is 0.7% and is not included in the numbers in the table. The horizontal lines indicate bin boundaries. – 22 – JHEP11(2015)103 pT[GeV/c] 2.0< y < 2.5 2.5< y < 3.0 3.0< y < 3.5 3.5< y < 4.0 4.0< y < 4.5 0−1 0.086 ±0.004 ±0.001 0.089 ±0.003 ±0.001 0.083 ±0.003 ±0.001 0.092 ±0.003 ±0.001 0.093 ±0.007 ±0.001 1−2 0.083 ±0.003 ±0.001 0.090 ±0.002 ±0.001 0.088 ±0.002 ±0.001 0.089 ±0.002 ±0.001 0.087 ±0.004 ±0.002 2−3 0.086 ±0.003 ±0.001 0.091 ±0.002 ±0.001 0.087 ±0.002 ±0.001 0.094 ±0.001 ±0.001 0.103 ±0.004 ±0.001 3−4 0.098 ±0.003 ±0.001 0.098 ±0.002 ±0.001 0.098 ±0.002 ±0.001 0.100 ±0.002 ±0.001 0.102 ±0.004 ±0.001 4−5 0.099 ±0.003 ±0.001 0.107 ±0.002 ±0.001 0.107 ±0.002 ±0.001 0.111 ±0.002 ±0.001 0.117 ±0.005 ±0.004 5−6 0.107 ±0.003 ±0.001 0.115 ±0.002 ±0.001 0.117 ±0.002 ±0.001 0.121 ±0.003 ±0.001 0.117 ±0.005 ±0.001 6−7 0.126 ±0.004 ±0.001 0.125 ±0.002 ±0.001 0.132 ±0.002 ±0.001 0.135 ±0.003 ±0.002 0.135 ±0.006 ±0.001 7−8 0.138 ±0.004 ±0.001 0.142 ±0.003 ±0.001 0.144 ±0.003 ±0.001 0.152 ±0.004 ±0.001 0.141 ±0.007 ±0.001 8−9 0.155 ±0.005 ±0.001 0.154 ±0.003 ±0.001 0.156 ±0.003 ±0.001 0.157 ±0.004 ±0.001 0.147 ±0.009 ±0.003 9−10 0.162 ±0.006 ±0.001 0.160 ±0.004 ±0.001 0.170 ±0.004 ±0.001 0.183 ±0.005 ±0.002 0.157 ±0.012 ±0.001 10 −11 0.164 ±0.007 ±0.001 0.180 ±0.005 ±0.002 0.186 ±0.005 ±0.001 0.205 ±0.007 ±0.002 0.220 ±0.019 ±0.009 11 −12 0.176 ±0.008 ±0.003 0.193 ±0.005 ±0.001 0.198 ±0.005 ±0.003 0.195 ±0.007 ±0.001 0.213 ±0.024 ±0.004 12 −13 0.211 ±0.010 ±0.002 0.221 ±0.006 ±0.001 0.216 ±0.007 ±0.001 0.224 ±0.009 ±0.002 0.192 ±0.031 ±0.002 13 −14 0.236 ±0.013 ±0.001 0.228 ±0.007 ±0.001 0.227 ±0.008 ±0.003 0.235 ±0.011 ±0.002 0.245 ±0.040 ±0.008 14 −15 0.245 ±0.015 ±0.003 0.248 ±0.009 ±0.003 0.236 ±0.010 ±0.001 0.257 ±0.014 ±0.005 15 −16 0.258 ±0.017 ±0.002 0.236 ±0.010 ±0.002 0.248 ±0.011 ±0.002 0.271 ±0.017 ±0.001 0.263 ±0.050 ±0.002 16 −17 0.251 ±0.019 ±0.003 0.263 ±0.012 ±0.002 0.272 ±0.014 ±0.001 0.235 ±0.019 ±0.006 17 −18 0.265 ±0.022 ±0.002 0.274 ±0.014 ±0.001 0.283 ±0.017 ±0.001 0.322 ±0.028 ±0.002 18 −19 0.283 ±0.024 ±0.002 0.277 ±0.017 ±0.002 0.278 ±0.018 ±0.001 0.343 ±0.035 ±0.004 19 −20 0.290 ±0.029 ±0.001 0.292 ±0.019 ±0.001 0.257 ±0.020 ±0.003 0.268 ±0.034 ±0.007 20 −21 0.310 ±0.025 ±0.002 0.312 ±0.017 ±0.004 0.273 ±0.018 ±0.005 0.355 ±0.032 ±0.009 21 −22 22 −23 0.308 ±0.032 ±0.002 0.334 ±0.023 ±0.001 0.348 ±0.028 ±0.002 23 −24 24 −25 0.275 ±0.035 ±0.001 0.353 ±0.029 ±0.002 0.374 ±0.040 ±0.002 25 −26 26 −27 0.430 ±0.050 ±0.005 0.325 ±0.040 ±0.001 0.329 ±0.040 ±0.005 27 −28 28 −29 0.310 ±0.040 ±0.004 29 −30 Table 15. The ratio R3,1for √s= 8 TeV. The first uncertainties are statistical and the second are the uncorrelated component of the systematic uncertainties. The overall correlated systematic uncertainty is 0.7% and is not included in the numbers in the table. The horizontal lines indicate bin boundaries. – 23 – JHEP11(2015)103 √s= 7 TeV √s= 8 TeV pT<30 GeV/c R2,10.253 ±0.001 ±0.004 0.255 ±0.001 ±0.004 R3,10.125 ±0.001 ±0.002 0.120 ±0.000 ±0.002 R3,20.493 ±0.003 ±0.007 0.470 ±0.002 ±0.007 pT<15 GeV/c R2,10.249 ±0.001 ±0.004 0.251 ±0.001 ±0.004 R3,10.121 ±0.001 ±0.002 0.116 ±0.000 ±0.002 R3,20.485 ±0.003 ±0.007 0.463 ±0.002 ±0.007 Table 16. The ratios Ri,jin the full kinematic range pT<30 GeV/c and in the reduced range pT<15 GeV/c for 2.0< y < 4.5. The first uncertainties are statistical and the second systematic. tions and confirms the previous LHCb observations [22,23]. For the region pT<15 GeV/c the results agree with the previous measurements [22,23], and supersede them. Acknowledgments We thank K.-T. Chao, H. Han and H.-S. Shao for providing the theory predictions for our measurements. We also would like to thank S.P. Baranov, L.S. Kisslinger, J.-P. Lansberg, A.K. Likhoded and A.V. Luchinsky for interesting and stimulating discussions on quarkonia production. 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); NSFC (China); CNRS/IN2P3 (France); BMBF, DFG, HGF and MPG (Germany); INFN (Italy); FOM and NWO (The Netherlands); MNiSW and NCN (Poland); MEN/IFA (Romania); MinES and FANO (Russia); MinECo (Spain); SNSF and SER (Switzerland); NASU (Ukraine); STFC (United Kingdom); NSF (U.S.A.). The Tier1 computing centres are supported by IN2P3 (France), KIT and BMBF (Germany), INFN (Italy), NWO and SURF (The Netherlands), PIC (Spain), GridPP (United Kingdom). We are indebted to the communities behind the multiple open source software packages on which we depend. We are also thankful for the computing resources and the access to software R&D tools provided by Yandex LLC (Russia). Individual groups or members have received support from EPLANET, Marie Sk lodowska-Curie Actions and ERC (European Union), Conseil g´en´eral de Haute-Savoie, Labex ENIGMASS and OCEVU, R´egion Auvergne (France), RFBR (Russia), XuntaGal and GENCAT (Spain), Royal Society and Royal Commission for the Exhibition of 1851 (United Kingdom). 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. – 24 – JHEP11(2015)103 A. 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Zucchelli14. 1Centro Brasileiro de Pesquisas F´ısicas (CBPF), Rio de Janeiro, Brazil 2Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil 3Center for High Energy Physics, Tsinghua University, Beijing, China 4LAPP, Universit´e Savoie Mont-Blanc, CNRS/IN2P3, Annecy-Le-Vieux, France 5Clermont Universit´e, Universit´e Blaise Pascal, CNRS/IN2P3, LPC, Clermont-Ferrand, France 6CPPM, Aix-Marseille Universit´e, CNRS/IN2P3, Marseille, France 7LAL, Universit´e Paris-Sud, CNRS/IN2P3, Orsay, France 8LPNHE, Universit´e Pierre et Marie Curie, Universit´e Paris Diderot, CNRS/IN2P3, Paris, France 9Fakult¨at Physik, Technische Universit¨at Dortmund, Dortmund, Germany 10 Max-Planck-Institut f¨ur Kernphysik (MPIK), Heidelberg, Germany 11 Physikalisches Institut, Ruprecht-Karls-Universit¨at Heidelberg, Heidelberg, Germany 12 School of Physics, University College Dublin, Dublin, Ireland 13 Sezione INFN di Bari, Bari, Italy 14 Sezione INFN di Bologna, Bologna, Italy 15 Sezione INFN di Cagliari, Cagliari, Italy 16 Sezione INFN di Ferrara, Ferrara, Italy 17 Sezione INFN di Firenze, Firenze, Italy 18 Laboratori Nazionali dell’INFN di Frascati, Frascati, Italy 19 Sezione INFN di Genova, Genova, Italy 20 Sezione INFN di Milano Bicocca, Milano, Italy 21 Sezione INFN di Milano, Milano, Italy 22 Sezione INFN di Padova, Padova, Italy 23 Sezione INFN di Pisa, Pisa, Italy 24 Sezione INFN di Roma Tor Vergata, Roma, Italy 25 Sezione INFN di Roma La Sapienza, Roma, Italy 26 Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences, Krak´ow, Poland 27 AGH - University of Science and Technology, Faculty of Physics and Applied Computer Science, Krak´ow, Poland – 31 – JHEP11(2015)103 28 National Center for Nuclear Research (NCBJ), Warsaw, Poland 29 Horia Hulubei National Institute of Physics and Nuclear Engineering, Bucharest-Magurele, Romania 30 Petersburg Nuclear Physics Institute (PNPI), Gatchina, Russia 31 Institute of Theoretical and Experimental Physics (ITEP), Moscow, Russia 32 Institute of Nuclear Physics, Moscow State University (SINP MSU), Moscow, Russia 33 Institute for Nuclear Research of the Russian Academy of Sciences (INR RAN), Moscow, Russia 34 Budker Institute of Nuclear Physics (SB RAS) and Novosibirsk State University, Novosibirsk, Russia 35 Institute for High Energy Physics (IHEP), Protvino, Russia 36 Universitat de Barcelona, Barcelona, Spain 37 Universidad de Santiago de Compostela, Santiago de Compostela, Spain 38 European Organization for Nuclear Research (CERN), Geneva, Switzerland 39 Ecole Polytechnique F´ed´erale de Lausanne (EPFL), Lausanne, Switzerland 40 Physik-Institut, Universit¨at Z¨urich, Z¨urich, Switzerland 41 Nikhef National Institute for Subatomic Physics, Amsterdam, The Netherlands 42 Nikhef National Institute for Subatomic Physics and VU University Amsterdam, Amsterdam, The Netherlands 43 NSC Kharkiv Institute of Physics and Technology (NSC KIPT), Kharkiv, Ukraine 44 Institute for Nuclear Research of the National Academy of Sciences (KINR), Kyiv, Ukraine 45 University of Birmingham, Birmingham, United Kingdom 46 H.H. Wills Physics Laboratory, University of Bristol, Bristol, United Kingdom 47 Cavendish Laboratory, University of Cambridge, Cambridge, United Kingdom 48 Department of Physics, University of Warwick, Coventry, United Kingdom 49 STFC Rutherford Appleton Laboratory, Didcot, United Kingdom 50 School of Physics and Astronomy, University of Edinburgh, Edinburgh, United Kingdom 51 School of Physics and Astronomy, University of Glasgow, Glasgow, United Kingdom 52 Oliver Lodge Laboratory, University of Liverpool, Liverpool, United Kingdom 53 Imperial College London, London, United Kingdom 54 School of Physics and Astronomy, University of Manchester, Manchester, United Kingdom 55 Department of Physics, University of Oxford, Oxford, United Kingdom 56 Massachusetts Institute of Technology, Cambridge, MA, United States 57 University of Cincinnati, Cincinnati, OH, United States 58 University of Maryland, College Park, MD, United States 59 Syracuse University, Syracuse, NY, United States 60 Pontif´ıcia Universidade Cat´olica do Rio de Janeiro (PUC-Rio), Rio de Janeiro, Brazil, associated to 2 61 Institute of Particle Physics, Central China Normal University, Wuhan, Hubei, China, associated to 3 62 Departamento de Fisica , Universidad Nacional de Colombia, Bogota, Colombia, associated to 8 63 Institut f¨ur Physik, Universit¨at Rostock, Rostock, Germany, associated to 11 64 National Research Centre Kurchatov Institute, Moscow, Russia, associated to 31 65 Yandex School of Data Analysis, Moscow, Russia, associated to 31 66 Instituto de Fisica Corpuscular (IFIC), Universitat de Valencia-CSIC, Valencia, Spain, associated to 36 67 Van Swinderen Institute, University of Groningen, Groningen, The Netherlands, associated to 41 aUniversidade Federal do Triˆangulo Mineiro (UFTM), Uberaba-MG, Brazil bP.N. Lebedev Physical Institute, Russian Academy of Science (LPI RAS), Moscow, Russia cUniversit`a di Bari, Bari, Italy dUniversit`a di Bologna, Bologna, Italy eUniversit`a di Cagliari, Cagliari, Italy fUniversit`a di Ferrara, Ferrara, Italy gUniversit`a di Urbino, Urbino, Italy – 32 – JHEP11(2015)103 hUniversit`a di Modena e Reggio Emilia, Modena, Italy iUniversit`a di Genova, Genova, Italy jUniversit`a di Milano Bicocca, Milano, Italy kUniversit`a di Roma Tor Vergata, Roma, Italy lUniversit`a di Roma La Sapienza, Roma, Italy mUniversit`a della Basilicata, Potenza, Italy nAGH - University of Science and Technology, Faculty of Computer Science, Electronics and Telecommunications, Krak´ow, Poland oLIFAELS, La Salle, Universitat Ramon Llull, Barcelona, Spain pHanoi University of Science, Hanoi, Viet Nam qUniversit`a di Padova, Padova, Italy rUniversit`a di Pisa, Pisa, Italy sScuola Normale Superiore, Pisa, Italy tUniversit`a degli Studi di Milano, Milano, Italy †Deceased – 33 –