Compact Muon Solenoid
LHC, CERN
Visit us: CMS Public Website, CMS Physics ;
Contact us: CMS Publications Committee
| CMS-HIN-16-021 ; CERN-EP-2017-261 | ||
| Pseudorapidity distributions of charged hadrons in proton-lead collisions at ${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 5.02 and 8.16 TeV | ||
| CMS Collaboration | ||
| 26 October 2017 | ||
| JHEP 01 (2018) 045 | ||
| Abstract: The pseudorapidity distributions of charged hadrons in proton-lead collisions at nucleon-nucleon center-of-mass energies ${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 5.02 and 8.16 TeV are presented. The measurements are based on data samples collected by the CMS experiment at the LHC. The number of primary charged hadrons produced in non-single-diffractive proton-lead collisions is determined in the pseudorapidity range $| \eta_{\text{lab}} | < $ 2.4. The charged-hadron multiplicity distributions are compared to the predictions from theoretical calculations and Monte Carlo event generators. In the center-of-mass pseudorapidity range $| \eta_{\text{cm}} | < $ 0.5, the average charged-hadron multiplicity densities ${<} \mathrm{d} N_{\text{ch}} / \mathrm{d} \eta_{\text{cm}} {>} | _ {| \eta_{\text{cm}} | < 0.5 }$ are 17.31 $\pm$ 0.01 (stat) $\pm$ 0.59 (syst) and 20.10 $\pm$ 0.01 (stat) $\pm$ 0.85 (syst) at ${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 5.02 and 8.16 TeV, respectively. The particle densities per participant nucleon are compared to similar measurements in proton-proton, proton-nucleus, and nucleus-nucleus collisions. | ||
| Links: e-print arXiv:1710.09355 [nucl-ex] (PDF) ; CDS record ; inSPIRE record ; HepData record ; CADI line (restricted) ; | ||
| Figures | |
png pdf |
Figure 1:
The $\Delta \eta $ (a) and $\Delta \phi $ (b, c) distributions of hit pairs for tracklets in pPb collisions at 8.16 TeV (squares) and from MC simulations with the EPOS and HIJING 1.3 generators (solid lines). The statistical uncertainties are smaller than the marker sizes for all distributions shown. |
png pdf |
Figure 1-a:
The $\Delta \eta $ distribution of hit pairs for tracklets in pPb collisions at 8.16 TeV (squares) and from MC simulations with the EPOS and HIJING 1.3 generators (solid lines). The statistical uncertainties are smaller than the marker sizes for all distributions shown. |
png pdf |
Figure 1-b:
The $\Delta \phi $ distribution of hit pairs for tracklets in pPb collisions at 8.16 TeV (squares) and from MC simulations with the EPOS and HIJING 1.3 generators (solid lines). The statistical uncertainties are smaller than the marker sizes for all distributions shown. |
png pdf |
Figure 1-c:
The $\Delta \phi $ distribution of hit pairs for tracklets in pPb collisions at 8.16 TeV (squares) and from MC simulations with the EPOS and HIJING 1.3 generators (solid lines). The statistical uncertainties are smaller than the marker sizes for all distributions shown. |
png pdf |
Figure 2:
Distributions of the pseudorapidity density of charged hadrons in the region $ | {\eta _{\text {lab}}} | < 2.4$ in NSD pPb collisions at $ {\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 5.02 (open squares) and 8.16 TeV (full squares). The measurement at 5.02 TeV by the ALICE Collaboration [30] is shown as filled circles. The shaded boxes indicate the systematic uncertainties which, in the case of the CMS data, are correlated between the two beam energies. The proton beam goes in the positive ${\eta _{\text {lab}}}$ direction. |
png pdf |
Figure 3:
Distributions of the pseudorapidity density of charged hadrons in the region $ | {\eta _{\text {lab}}} | < $ 2.4 for NSD pPb collisions at 8.16 TeV (squares) compared to predictions from the MC event generators EPOS LHC [27,17] (v3400), HIJING [14] (versions 1.3 [15] and 2.1 [12]), and DPMJET-III [16], as well as from the KLN model [11]. The shaded boxes around the data points indicate their systematic uncertainties. The proton beam goes in the positive ${\eta _{\text {lab}}} $ direction. |
png pdf |
Figure 4:
Comparison of the measured $ {{\mathrm {d}}{}N_{\text {ch}}/ {\mathrm {d}}\eta _{\text {cm}}} $ at midrapidity, scaled by the number of participating nucleons (${N_{\text {part}}}$) in pPb [30,51], pAu [52], dAu [33,48,53] and central heavy ion collisions [37,38,39,40,41,42,43,44,45,46,47,26,48,49,50], as well as NSD [54,55,56,50,57,22,23] and inelastic [58,56,59,37,25] pp collisions. The AA data points at $ {\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 2.76 TeV have been shifted horizontally for visibility. The dashed curves, included to guide the eye, correspond to a fit to the data points using the same functional form as in Refs. [59,46]. |
| Tables | |
png pdf |
Table 1:
Summary of the systematic uncertainties from various sources, for pPb collisions at 5.02 and 8.16 TeV. The range of values indicates the minimum and maximum uncertainties across the ${\eta _{\text {lab}}}$ range. |
| Summary |
| The pseudorapidity distributions of primary charged hadrons have been measured by the CMS experiment at the LHC in proton-lead collisions at ${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 5.02 and 8.16 TeV. Based on pairs of pixel clusters from two different layers of the barrel region of the CMS pixel detector, the distributions have been obtained for NSD pPb events at both collision energies. The measured $\mathrm{d} N / \mathrm{d} \eta_{\text{lab}}$ distribution at 5.02 TeV is consistent with published results by the ALICE Collaboration. At 8.16 TeV, the measured $\mathrm{d} N / \mathrm{d} \eta_{\text{lab}} $ distribution is higher than the predictions of EPOS LHC, but significantly lower than the predictions from the HIJING 1.3 and DPMJET-III event generators. At $\eta_{\text{lab}} \approx $ 0, the measured distributions are in good agreement with calculations from the KLN gluon saturation model and predictions from the HIJING 2.1 event generator with the effects of gluon shadowing included. The charged-hadron multiplicity densities in the nucleon-nucleon center-of-mass frame, $ {<} \mathrm{d} N_{\text{ch}} / \mathrm{d} \eta_{\text{cm}} {>} | _ {| \eta_{\text{cm}} | < 0.5 } $, are 17.31 $\pm$ 0.01 (stat) $\pm$ 0.59 (syst) and 20.10 $\pm$ 0.01 (stat) $\pm$ 0.85 (syst) at ${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 5.02 and 8.16 TeV, respectively. When comparing the average charged-particle density per participant nucleon for pp, pA, and NN collisions as a function of collision energy, the pA results are found to be below those in central NN collisions and NSD pp collisions, but coincide with the trend seen in inelastic pp collisions. These results represent the first measurement of hadron production at this new center-of-mass energy frontier in nuclear collisions, and provide constraints for the understanding of nonperturbative QCD effects in high-energy nuclear collisions. |
| References | ||||
| 1 | W. Busza | Review of experimental data on hadron-nucleus collisions at high-energies | Acta Phys. Polon. B 8 (1977)333 | |
| 2 | C. A. Salgado et al. | Proton-nucleus collisions at the LHC: scientific opportunities and requirements | JPG 39 (2012) 015010 | 1105.3919 |
| 3 | CMS Collaboration | Nuclear effects on the transverse momentum spectra of charged particles in pPb collisions at $ \sqrt{s_{_\mathrm{NN}}} = $ 5.02 TeV | EPJC 75 (2015) 237 | CMS-HIN-12-017 1502.05387 |
| 4 | CMS Collaboration | Charged-particle nuclear modification factors in PbPb and pPb collisions at $ \sqrt{s_{_\mathrm{NN}}} = $ 5.02 TeV | JHEP 04 (2017) 039 | CMS-HIN-15-015 1611.01664 |
| 5 | CMS Collaboration | Study of B meson production in $ p $+Pb collisions at $ \sqrt{s_{_\mathrm{NN}}} = $ 5.02 TeV using exclusive hadronic decays | PRL 116 (2016) 032301 | CMS-HIN-14-004 1508.06678 |
| 6 | ALICE Collaboration | $ D $-meson production in $ p $-Pb collisions at $ \sqrt{s_{_\mathrm{NN}}} = $ 5.02 TeV and in pp collisions at $ \sqrt{s} = $ 7 TeV | PRC 94 (2016) 054908 | 1605.07569 |
| 7 | CMS Collaboration | Measurement of prompt and nonprompt $ \mathrm{J}/{\psi} $ production in pp and pPb collisions at $ \sqrt{s_{_\mathrm{NN}}} = $ 5.02 TeV | EPJC 77 (2017) 269 | CMS-HIN-14-009 1702.01462 |
| 8 | CMS Collaboration | Transverse momentum spectra of inclusive b jets in pPb collisions at $ \sqrt{s_{_\mathrm{NN}}} = $ 5.02 TeV | PLB 754 (2016) 59 | CMS-HIN-14-007 1510.03373 |
| 9 | CMS Collaboration | Measurement of inclusive jet production and nuclear modifications in pPb collisions at $ \sqrt{s_{_\mathrm{NN}}} = $ 5.02 TeV | EPJC 76 (2016) 372 | CMS-HIN-14-001 1601.02001 |
| 10 | CMS Collaboration | Studies of dijet transverse momentum balance and pseudorapidity distributions in pPb collisions at $ \sqrt{s_{_\mathrm{NN}}} = $ 5.02 TeV | EPJC 74 (2014) 2951 | CMS-HIN-13-001 1401.4433 |
| 11 | A. Dumitru, D. E. Kharzeev, E. M. Levin, and Y. Nara | Gluon saturation in $ pA $ collisions at energies available at the CERN Large Hadron Collider: Predictions for hadron multiplicities | PRC 85 (2012) 044920 | 1111.3031 |
| 12 | R. Xu, W.-T. Deng, and X.-N. Wang | Nuclear modification of high-$ p_{\mathrm{T}} $ hadron spectra in high-energy $ p+A $ collisions | PRC 86 (2012) 051901 | 1204.1998 |
| 13 | J. L. Albacete, A. Dumitru, H. Fujii, and Y. Nara | CGC predictions for p+Pb collisions at the LHC | NP A 897 (2013) 1 | 1209.2001 |
| 14 | X.-N. Wang and M. Gyulassy | HIJING: A Monte Carlo model for multiple jet production in pp, pA and AA collisions | PRD 44 (1991) 3501 | |
| 15 | M. Gyulassy and X.-N. Wang | HIJING 1.0: A Monte Carlo program for parton and particle production in high energy hadronic and nuclear collisions | CPC 83 (1994) 307 | nucl-th/9502021 |
| 16 | S. Roesler, R. Engel, and J. Ranft | The Monte Carlo event generator DPMJET-III | in Advanced Monte Carlo for radiation physics, particle transport simulation and applications. Proceedings, Conference, MC2000, Lisbon, Portugal, October 23-26, 2000, p. 1033 2000 | hep-ph/0012252 |
| 17 | T. Pierog et al. | EPOS LHC: Test of collective hadronization with data measured at the CERN Large Hadron Collider | PRC 92 (2015) 034906 | 1306.0121 |
| 18 | E178 Collaboration | Energy dependence of the pseudorapidity distributions in proton-nucleus collisions between 50 and 200$ GeV/$c | PRL 39 (1977) 1499 | |
| 19 | W. Kittel and E. A. De Wolf | Soft Multihadron Dynamics | Hackensack, USA: World Scientific, 2005 ,ISBN 9789812562951 | |
| 20 | CMS Collaboration | Charged particle multiplicities in pp interactions at $ \sqrt{s}= $ 0.9 , 2.36, and 7 TeV | JHEP 01 (2011) 079 | CMS-QCD-10-004 1011.5531 |
| 21 | D. d'Enterria et al. | Constraints from the first LHC data on hadronic event generators for ultra-high energy cosmic-ray physics | Astropart. Phys. 35 (2011) 98 | 1101.5596 |
| 22 | CMS Collaboration | Transverse-momentum and pseudorapidity distributions of charged hadrons in pp collisions at $ \sqrt{s} = $ 0.9 and $ 2.36 $ TeV | JHEP 02 (2010) 041 | CMS-QCD-09-010 1002.0621 |
| 23 | CMS Collaboration | Transverse-momentum and pseudorapidity distributions of charged hadrons in $ pp $ collisions at $ \sqrt{s} = $ 7 TeV | PRL 105 (2010) 022002 | CMS-QCD-10-006 1005.3299 |
| 24 | CMS and TOTEM Collaborations | Measurement of pseudorapidity distributions of charged particles in proton-proton collisions at $ \sqrt{s} = $ 8 TeV by the CMS and TOTEM experiments | EPJC 74 (2014) 3053 | 1405.0722 |
| 25 | CMS Collaboration | Pseudorapidity distribution of charged hadrons in proton-proton collisions at $ \sqrt{s} = $ 13 TeV | PLB 751 (2015) 143 | CMS-FSQ-15-001 1507.05915 |
| 26 | CMS Collaboration | Dependence on pseudorapidity and on centrality of charged hadron production in PbPb collisions at $ \sqrt{s_{_\mathrm{NN}}} = $ 2.76 TeV | JHEP 08 (2011) 141 | CMS-HIN-10-001 1107.4800 |
| 27 | K. Werner, F.-M. Liu, and T. Pierog | Parton ladder splitting and the rapidity dependence of transverse momentum spectra in deuteron-gold collisions at the BNL Relativistic Heavy Ion Collider | PRC 74 (2006) 044902 | hep-ph/0506232 |
| 28 | CMS Collaboration | The CMS experiment at the CERN LHC | JINST 3 (2008) S08004 | CMS-00-001 |
| 29 | GEANT4 Collaboration | $ \scGeant4 $ --- a simulation toolkit | NIMA 506 (2003) 250 | |
| 30 | ALICE Collaboration | Pseudorapidity density of charged particles in $ p $+Pb collisions at $ \sqrt{s_{_\mathrm{NN}}} = $ 5.02 TeV | PRL 110 (2013) 032301 | 1210.3615 |
| 31 | D. Kharzeev and E. Levin | Manifestations of high density QCD in the first RHIC data | PLB 523 (2001) 79 | nucl-th/0108006 |
| 32 | D. Kharzeev, E. Levin, and M. Nardi | Onset of classical QCD dynamics in relativistic heavy ion collisions | PRC 71 (2005) 054903 | hep-ph/0111315 |
| 33 | PHOBOS Collaboration | Pseudorapidity distribution of charged particles in $ d $+Au collisions at $ \sqrt{s_{_\mathrm{NN}}} = $ 200 GeV | PRL 93 (2004) 082301 | nucl-ex/0311009 |
| 34 | A. Capella, U. Sukhatme, C.-I. Tan, and J. Tran Thanh Van | Dual parton model | PR 236 (1994) 225 | |
| 35 | G. Veneziano | Regge intercepts and unitarity in planar dual models | NPB 74 (1974) 365 | |
| 36 | M. L. Miller, K. Reygers, S. J. Sanders, and P. Steinberg | Glauber modeling in high-energy nuclear collisions | Ann. Rev. Nucl. Part. Sci. 57 (2007) 205 | nucl-ex/0701025 |
| 37 | PHOBOS Collaboration | Charged-particle multiplicity and pseudorapidity distributions measured with the PHOBOS detector in Au+Au, Cu+Cu, d+Au, and p+p collisions at ultrarelativistic energies | PRC 83 (2011) 024913 | 1011.1940 |
| 38 | NA50 Collaboration | Scaling of charged particle multiplicity in Pb-Pb collisions at SPS energies | PLB 530 (2002) 43 | |
| 39 | STAR Collaboration | Multiplicity distribution and spectra of negatively charged hadrons in $ Au+Au $ collisions at $ \sqrt{s_{_\mathrm{NN}}} = $ 130 GeV | PRL 87 (2001) 112303 | nucl-ex/0106004 |
| 40 | BRAHMS Collaboration | Charged particle densities from Au+Au collisions at $ \sqrt{s_{_\mathrm{NN}}} = $ 130 GeV | PLB 523 (2001) 227 | nucl-ex/0108016 |
| 41 | BRAHMS Collaboration | Pseudorapidity distributions of charged particles from Au+Au collisions at the maximum RHIC energy, $ \sqrt{s_{_\mathrm{NN}}} = $ 200 GeV | PRL 88 (2002) 202301 | nucl-ex/0112001 |
| 42 | PHENIX Collaboration | Centrality dependence of charged particle multiplicity in Au-Au collisions at $ \sqrt{s_{_\mathrm{NN}}} = $ 130 GeV | PRL 86 (2001) 3500 | nucl-ex/0012008 |
| 43 | PHOBOS Collaboration | Charged-particle multiplicity near midrapidity in central $ Au+Au $ collisions at $ \sqrt{s_{_\mathrm{NN}}} = $ 56 and 130 GeV | PRL 85 (2000) 3100 | hep-ex/0007036 |
| 44 | PHOBOS Collaboration | Charged-particle pseudorapidity density distributions from $ Au+Au $ collisions at $ \sqrt{s_{_\mathrm{NN}}} = $ 130 GeV | PRL 87 (2001) 102303 | nucl-ex/0106006 |
| 45 | PHOBOS Collaboration | Significance of the fragmentation region in ultrarelativistic heavy-ion collisions | PRL 91 (2003) 052303 | nucl-ex/0210015 |
| 46 | ALICE Collaboration | Charged-particle multiplicity density at midrapidity in central Pb-Pb collisions at $ \sqrt{s_{_\mathrm{NN}}} = $ 2.76 TeV | PRL 105 (2010) 252301 | 1011.3916 |
| 47 | ATLAS Collaboration | Measurement of the centrality dependence of the charged particle pseudorapidity distribution in lead-lead collisions at $ \sqrt{s_{_\mathrm{NN}}} = $ 2.76 TeV with the ATLAS detector | PLB 710 (2012) 363 | 1108.6027 |
| 48 | PHENIX Collaboration | Transverse energy production and charged-particle multiplicity at midrapidity in various systems from $ \sqrt{s_{_\mathrm{NN}}}= $ 7.7 to 200 GeV | PRC 93 (2016), no. 2, 024901 | 1509.06727 |
| 49 | STAR Collaboration | Identified particle production, azimuthal anisotropy, and interferometry measurements in Au+Au collisions at $ \sqrt{s_{_\mathrm{NN}}} = $ 9.2 GeV | PRC 81 (2010) 024911 | 0909.4131 |
| 50 | STAR Collaboration | Systematic measurements of identified particle spectra in $ pp $, $ d $+Au, and Au+Au collisions at the STAR detector | PRC 79 (2009) 034909 | 0808.2041 |
| 51 | E178 Collaboration | Experimental study of multiparticle production in hadron-nucleus interactions at high energy | PRD 22 (1980) 13 | |
| 52 | NA35 Collaboration | Charged particle production in proton, deuteron, oxygen and sulphur nucleus collisions at 200 GeV per nucleon | EPJC 2 (1998) 643 | hep-ex/9711001 |
| 53 | PHENIX Collaboration | Measurements of azimuthal anisotropy and charged-particle multiplicity in $ d $+Au collisions at $ \sqrt{s_{_\mathrm{NN}}}= $ 200 , 62.4, 39, and 19.6 GeV | Submitted to \it PRC | 1708.06983 |
| 54 | UA1 Collaboration | A study of the general characteristics of proton-antiproton collisions at $ \sqrt{s} = $ 0.2 to 0.9 TeV | NPB 335 (1990) 261 | |
| 55 | UA5 Collaboration | Particle multiplicities in pp interactions at $ \sqrt{s} = $ 540 GeV | PLB 121 (1983) 209 | |
| 56 | UA5 Collaboration | Scaling of pseudorapidity distributions at c.m. energies up to 0.9 TeV | Z. Phys. C 33 (1986) 1 | |
| 57 | CDF Collaboration | Pseudorapidity distributions of charged particles produced in $ \bar{p}p $ interactions at $ \sqrt{s} = $ 630 and 1800 GeV | PRD 41 (1990) 2330 | |
| 58 | Aachen-CERN-Heidelberg-Munich Collaboration | Charged particle multiplicity distributions in pp collisions at ISR energies | NPB 129 (1977) 365 | |
| 59 | ALICE Collaboration | Charged-particle multiplicity measurement in proton-proton collisions at $ \sqrt{s}= $ 0.9 and 2.36 TeV with ALICE at LHC | EPJC 68 (2010) 89 | 1004.3034 |
|
|
Compact Muon Solenoid LHC, CERN |
|
|
|
|
|
|