Compact Muon Solenoid
LHC, CERN
Visit us: CMS Public Website, CMS Physics ;
Contact us: CMS Publications Committee
| CMS-HIN-16-013 ; CERN-EP-2018-213 | ||
| Strange hadron production in pp and pPb collisions at ${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 5.02 TeV | ||
| CMS Collaboration | ||
| 10 October 2019 | ||
| Phys. Rev. C 101 (2020) 064906 | ||
| Abstract: The transverse momentum (${p_{\mathrm{T}}}$) distributions of $\Lambda$, $ \Xi^{-}$, and $\Omega^{-}$ baryons, their antiparticles, and ${\mathrm{K^0_S}}$ mesons are measured in proton-proton (pp) and proton-lead (pPb) collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV over a broad rapidity range. The data, corresponding to integrated luminosities of 40.2 nb$^{-1}$ and 15.6 $\mu$b$^{-1}$ for pp and pPb collisions, respectively, were collected by the CMS experiment. The nuclear modification factor ${R_{\mathrm{pPb}}} $, defined as the ratio of the particle yield in pPb collisions and a scaled pp reference, is measured for each particle. A strong dependence on particle species is observed in the ${p_{\mathrm{T}}}$ range from 2 to 7 GeV, where ${R_{\mathrm{pPb}}} $ for ${\mathrm{K^0_S}}$ is consistent with unity, while an enhancement ordered by strangeness content and/or particle mass is observed for the three baryons. In pPb collisions, the strange hadron production is asymmetric about the nucleon-nucleon center-of-mass rapidity. Enhancements, which depend on the particle type, are observed in the direction of the Pb beam. The results are compared to predictions from EPOS LHC, which includes parametrized radial flow. The model is in qualitative agreement with the ${R_{\mathrm{pPb}}} $ data, but fails to describe the dependence on particle species in the yield asymmetries measured away from mid-rapidity in pPb collisions. | ||
| Links: e-print arXiv:1910.04812 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; HepData record ; CADI line (restricted) ; | ||
| Figures | |
png pdf |
Figure 1:
Invariant mass distribution of ${\mathrm{K^0_S}}$ (upper left), $\Lambda$+$\bar{\Lambda}$ (upper right), $\Xi^{-}$+${\bar{\Xi}}^{+}$ (lower left), and $\Omega^{-}$+$\bar{\Omega}^{+}$ (lower right) candidates within $ {| {y_\mathrm {CM}} |} < $ 1.8 in pPb collisions. The solid lines show the results of fits described in the text. The dashed lines indicate the fitted background component. |
png pdf |
Figure 2:
The invariant ${p_{\mathrm {T}}} $-differential spectra of ${\mathrm{K^0_S}}$ (upper left), $\Lambda$+$\bar{\Lambda}$ (upper right), $\Xi^{-}$+${\bar{\Xi}}^{+}$ (lower left), and $\Omega^{-}$+$\bar{\Omega}^{+}$ (lower right) for $ {| {y_\mathrm {CM}} |} < $ 1.8, $-$1.8 $< {y_\mathrm {CM}} < $ 0, and 0 $ < {y_\mathrm {CM}} < $ 1.8 in pp and pPb collisions at $ {\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 5.02 TeV. Spectra for different ${y_\mathrm {CM}}$ ranges are scaled by factors of powers of 10, with $ {| {y_\mathrm {CM}} |} < $ 1.8 not scaled. To compare the strange-particle spectra in pp and pPb collisions directly, the spectra in pPb collisions are divided by 6.9, which is the average number of binary nucleon-nucleon collisions. The vertical bars correspond to statistical uncertainties, which are usually smaller than the marker size, while the horizontal bars represent the bin width. |
png pdf |
Figure 3:
(Upper) Nuclear modification factors for ${\mathrm{K^0_S}}$ (black filled circles), $\Lambda$+$\bar{\Lambda}$ (red filled squares), $\Xi^{-}$+${\bar{\Xi}}^{+}$ (blue open circles), and $\Omega^{-}$+$\bar{\Omega}^{+}$ (purple open squares) for $ {| {y_\mathrm {CM}} |} < $ 1.8 in pPb collisions are presented. The vertical bars correspond to statistical uncertainties, and the horizontal bars represent the bin width, while the open boxes around the markers denote the systematic uncertainties. The $< {\mathrm {T}_\mathrm {pPb}} > $ and pp integrated luminosity uncertainties are represented by the shaded boxes around unity. The results are compared to the EPOS LHC predictions, which include collective flow in pp and pPb collisions. The data and predictions share the same color for each particle species. (Lower) The ratios of nuclear modification factors for ${\mathrm{K^0_S}}$, $\Lambda$+$\bar{\Lambda}$, $\Xi^{-}$+${\bar{\Xi}}^{+}$, and $\Omega^{-}$+$\bar{\Omega}^{+}$ of the EPOS LHC predictions to the measurements are shown. The bands represent the combination of statistical and systematic uncertainties. |
png pdf |
Figure 4:
Nuclear modification factors of ${\mathrm{K^0_S}}$ (black filled circles), $\Lambda$+$\bar{\Lambda}$ (red filled squares), and $\Xi^{-}$+${\bar{\Xi}}^{+}$ (blue open circles) particles for $-$1.8 $< {y_\mathrm {CM}} < $ 0 (Pb going, left) and 0 $ < {y_\mathrm {CM}} < $ 1.8 (p going, right) in pPb collisions are presented. The vertical bars correspond to statistical uncertainties, and the horizontal bars represent the bin width, while the open boxes around the markers denote the systematic uncertainties. The $< {\mathrm {T}_\mathrm {pPb}} > $ and pp integrated luminosity uncertainties are represented by the shaded boxes around unity. The results are compared to the EPOS LHC predictions, which include collective flow in pp and pPb collisions {[38]}. The data and predictions share the same color for each particle species. |
png pdf |
Figure 5:
The invariant ${p_{\mathrm {T}}} $-differential spectra of ${\mathrm{K^0_S}}$ (left) and $\Lambda$+$\bar{\Lambda}$ (right) particles for $-$1.8 $< {y_\mathrm {CM}} < -$1.3, $-$1.3 $< {y_\mathrm {CM}} < -$0.8, $-$0.8 $< {y_\mathrm {CM}} < -$0.3, 0.3 $ < {y_\mathrm {CM}} < $ 0.8, 0.8 $ < {y_\mathrm {CM}} < $ 1.3, and 1.3 $ < {y_\mathrm {CM}} < $ 1.8 in pPb \ collisions at $ {\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 5.02 TeV. Spectra in different ${y_\mathrm {CM}}$ ranges are scaled by factors of powers of 10, with $-$0.8 $< {y_\mathrm {CM}} < -$0.3 not scaled. The vertical bars correspond to statistical uncertainties, which are usually smaller than the marker size, while the horizontal bars represent the bin width. |
png pdf |
Figure 6:
The ${Y_\text {asym}}$ of ${\mathrm{K^0_S}}$ (black filled circles), $\Lambda$+$\bar{\Lambda}$ (red filled squares), and charged particles (blue open squares) at 0.3 $ < {| {y_\mathrm {CM}} |} < $ 0.8, 0.8 $ < {| {y_\mathrm {CM}} |} < $ 1.3, and 1.3 $ < {| {y_\mathrm {CM}} |} < $ 1.8 ($ {| \eta _\mathrm {CM} |}$ ranges for charged particles) in pPb collisions at $ {\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 5.02 TeV. The vertical bars correspond to statistical uncertainties, and the horizontal bars represent the bin width, while the boxes around the markers denote the systematic uncertainties. The results are compared to the EPOS LHC predictions, which include collective flow in pp and pPb collisions [38]. The data and predictions share the same color for each particle species. |
| Tables | |
png pdf |
Table 1:
Summary of different sources of systematic uncertainties in ${\mathrm{K^0_S}}$, $\Lambda$, $ \Xi^{-}$, and $\Omega^{-}$ ${p_{\mathrm {T}}} $ spectra and ${R_{\mathrm {pPb}}}$ measurements for different ${y_\mathrm {CM}}$ ranges in both pp and pPb collisions. The ranges quoted cover both the ${p_{\mathrm {T}}} $ and the rapidity dependence of the uncertainties. |
png pdf |
Table 2:
Summary of systematic uncertainties in the ${Y_\text {asym}}$ measurements in pPb collisions. The ranges quoted cover both the ${p_{\mathrm {T}}} $ and the rapidity dependence of the uncertainties. Because of limitations in the size of the data sample, the ${Y_\text {asym}}$ of $\Xi^{-}$ and $\Omega^{-}$ are not presented. |
| Summary |
| The transverse momentum (${p_{\mathrm{T}}}$) spectra of ${\mathrm{K^0_S}}$ mesons, and $\Lambda$, $ \Xi^{-}$, and $\Omega^{-}$ baryons (each summed with its anti-particle) have been measured in proton-proton and proton-lead collisions in several nucleon-nucleon center-of-mass rapidity (${y_\mathrm{CM}} $) ranges. The nuclear modification factors of ${\mathrm{K^0_S}}$, $\Lambda$, and $\Xi^{-}$ in $|{{y_\mathrm{CM}} }| < $ 1.8, $-$1.8 $< {y_\mathrm{CM}} < $ 0, and 0 $ < {y_\mathrm{CM}} < $ 1.8 ranges are measured. In the ${p_{\mathrm{T}}}$ range from 2 to 7 GeV, enhancements are visible and a clear mass ordering is observed, which is consistent with expectations from radial-flow effects in hydrodynamic models. For each particle species, the nuclear modification factor ${R_{\mathrm{pPb}}}$ in the Pb-going side is higher than in the p-going side. This trend is also consistent with expectations from radial flow. The rapidity asymmetries ${Y_\text{asym}}$ in ${\mathrm{K^0_S}}$ and $\Lambda$ yields between equivalent positive and negative $ {y_\mathrm{CM}} $ are presented as functions of ${p_{\mathrm{T}}}$ in 0.3 $ < |{{y_\mathrm{CM}} }| < $ 0.8, 0.8 $ < |{{y_\mathrm{CM}} }| < $ 1.3, and 1.3 $ < |{{y_\mathrm{CM}} }| < $ 1.8, and compared to those for charged particles. The ${Y_\text{asym}}$ values are larger than unity in all three $ {y_\mathrm{CM}} $ ranges with greater enhancements observed at more forward regions. The mass dependence of ${R_{\mathrm{pPb}}}$ in the EPOS LHC model, which includes collective flow, is stronger than that observed in the data. The model also describes the increasing trend of ${Y_\text{asym}}$ from mid-rapidity to forward rapidity, but fails to describe the dependence on particle species at forward rapidity. The results presented in this paper provide new insights into particle production in pPb collisions at high energies. |
| References | ||||
| 1 | NA44 Collaboration | Collective expansion in high-energy heavy ion collisions | PRL 78 (1997) 2080 | |
| 2 | NA49 Collaboration | Baryon stopping and charged particle distributions in central Pb+Pb collisions at 158 GeV per nucleon | PRL 82 (1999) 2471 | nucl-ex/9810014 |
| 3 | STAR Collaboration | Measurement of inclusive anti-protons from Au+Au collisions at ${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 130 GeV | PRL 87 (2001) 262302 | nucl-ex/0110009 |
| 4 | PHENIX Collaboration | Single identified hadron spectra from ${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 130 GeV Au+Au collisions | PRC 69 (2004) 024904 | nucl-ex/0307010 |
| 5 | PHENIX Collaboration | Identified charged particle spectra and yields in Au+Au collisions at ${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 200 GeV | PRC 69 (2004) 034909 | nucl-ex/0307022 |
| 6 | ALICE Collaboration | Centrality dependence of $ \pi $, K, p production in Pb-Pb collisions at $ \sqrt{s_{NN}} = $ 2.76 TeV | PRC 88 (2013) 044910 | 1303.0737 |
| 7 | 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 |
| 8 | E. Schnedermann, J. Sollfrank, and U. W. Heinz | Thermal phenomenology of hadrons from 200A GeV S+S collisions | PRC 48 (1993) 2462 | nucl-th/9307020 |
| 9 | R. C. Hwa and C. B. Yang | Scaling distributions of quarks, mesons and proton for all $ {p_{\mathrm{T}}}, $ energy and centrality | PRC 67 (2003) 064902 | nucl-th/0302006 |
| 10 | R. J. Fries, B. Muller, C. Nonaka, and S. A. Bass | Hadronization in heavy ion collisions: recombination and fragmentation of partons | PRL 90 (2003) 202303 | nucl-th/0301087 |
| 11 | V. Greco, C. M. Ko, and P. Levai | Parton coalescence and anti-proton/pion anomaly at RHIC | PRL 90 (2003) 202302 | nucl-th/0301093 |
| 12 | X.-N. Wang | Rapidity asymmetry in high-energy d+A collisions | PLB 565 (2003) 116 | nucl-th/0303004 |
| 13 | Z.-B. Kang, I. Vitev, and H. Xing | Nuclear modification of high transverse momentum particle production in p+A collisions at RHIC and LHC | PLB 718 (2012) 482 | 1209.6030 |
| 14 | M. Arneodo | Nuclear effects in structure functions | PR 240 (1994) 301 | |
| 15 | PHENIX Collaboration | Absence of suppression in particle production at large transverse momentum in ${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 200 GeV d+Au collisions | PRL 91 (2003) 072303 | nucl-ex/0306021 |
| 16 | PHOBOS Collaboration | Centrality dependence of charged hadron transverse momentum spectra in d+Au collisions at ${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 200 GeV | PRL 91 (2003) 072302 | nucl-ex/0306025 |
| 17 | STAR Collaboration | Evidence from d+Au measurements for final state suppression of high $ {p_{\mathrm{T}}} $ hadrons in Au+Au collisions at RHIC | PRL 91 (2003) 072304 | nucl-ex/0306024 |
| 18 | BRAHMS Collaboration | Transverse momentum spectra in Au+Au and d+Au collisions at ${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 200 GeV and the pseudorapidity dependence of high $ {p_{\mathrm{T}}} $ suppression | PRL 91 (2003) 072305 | nucl-ex/0307003 |
| 19 | CMS Collaboration | Observation of long-range near-side angular correlations in proton-lead collisions at the LHC | PLB 718 (2013) 795 | CMS-HIN-12-015 1210.5482 |
| 20 | CMS Collaboration | Multiplicity and transverse momentum dependence of two- and four-particle correlations in pPb and PbPb collisions | PLB 724 (2013) 213 | CMS-HIN-13-002 1305.0609 |
| 21 | CMS Collaboration | Evidence for collective multiparticle correlations in p-Pb collisions | PRL 115 (2015) 012301 | CMS-HIN-14-006 1502.05382 |
| 22 | CMS Collaboration | Evidence for collectivity in pp collisions at the LHC | PLB 765 (2017) 193 | CMS-HIN-16-010 1606.06198 |
| 23 | PHENIX Collaboration | Measurement of long-range angular correlations and azimuthal anisotropies in high-multiplicity p+Au collisions at ${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 200 GeV | PRC 95 (2017) 034910 | 1609.02894 |
| 24 | PHENIX Collaboration | Measurement of long-range angular correlation and quadrupole anisotropy of pions and (anti)protons in central d+Au collisions at ${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 200 GeV | PRL 114 (2015) 192301 | 1404.7461 |
| 25 | PHENIX Collaboration | Measurements of elliptic and triangular flow in high-multiplicity $ ^3 $He+Au collisions at ${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 200 GeV | PRL 115 (2015) 142301 | 1507.06273 |
| 26 | PHENIX Collaboration | Creation of quark-gluon plasma droplets with three distinct geometries | NP 15 (2019) 214 | 1805.02973 |
| 27 | ALICE Collaboration | Multi-strange baryon production in p-Pb collisions at ${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 5.02 TeV | PLB 758 (2016) 389 | 1512.07227 |
| 28 | ALICE Collaboration | Enhanced production of multi-strange hadrons in high-multiplicity proton-proton collisions | NP 13 (2017) 535 | 1606.07424 |
| 29 | J. Rafelski and B. Muller | Strangeness production in the quark-gluon plasma | PRL 48 (1982) 1066 | |
| 30 | CMS Collaboration | Multiplicity and rapidity dependence of strange hadron production in pp, pPb, and PbPb collisions at the LHC | PLB 768 (2017) 103 | CMS-HIN-15-006 1605.06699 |
| 31 | CMS Collaboration | Study of the production of charged pions, kaons, and protons in pPb collisions at ${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 5.02 TeV | Eur. Phys. Journ. C 74 (2014) 2847 | CMS-HIN-12-016 1307.3442 |
| 32 | CMS Collaboration | Measurement of inclusive jet production and nuclear modifications in pPb collisions at ${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 5.02 TeV | EPJC 76 (2016) 372 | CMS-HIN-14-001 1601.02001 |
| 33 | ALICE Collaboration | Measurement of charged jet production cross sections and nuclear modification in p-Pb collisions at ${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 5.02 TeV | PLB 749 (2015) 68 | 1503.00681 |
| 34 | ALICE Collaboration | Transverse momentum dependence of inclusive primary charged-particle production in p-Pb collisions at ${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 5.02 TeV | EPJC 74 (2014) 3054 | 1405.2737 |
| 35 | ATLAS Collaboration | Transverse momentum, rapidity, and centrality dependence of inclusive charged-particle production in ${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 5.02 TeV p+Pb collisions measured by the ATLAS experiment | PLB 763 (2016) 313 | 1605.06436 |
| 36 | CMS Collaboration | Nuclear effects on the transverse momentum spectra of charged particles in pPb collisions at ${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 5.02 TeV | EPJC 75 (2015) 237 | CMS-HIN-12-017 1502.05387 |
| 37 | P. Bozek, A. Bzdak, and V. Skokov | The rapidity dependence of the average transverse momentum in p+Pb collisions at the LHC: the color glass condensate versus hydrodynamics | PLB 728 (2014) 662 | 1309.7358 |
| 38 | 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 |
| 39 | Z.-B. Kang, I. Vitev, and H. Xing | Multiple scattering effects on inclusive particle production in the large-x regime | PRD 88 (2013) 054010 | 1307.3557 |
| 40 | CMS Collaboration | Description and performance of track and primary-vertex reconstruction with the CMS tracker | JINST 9 (2014) P10009 | CMS-TRK-11-001 1405.6569 |
| 41 | CMS Collaboration | The CMS experiment at the CERN LHC | JINST 3 (2008) S08004 | CMS-00-001 |
| 42 | GEANT4 Collaboration | GEANT4--a simulation toolkit | NIMA 506 (2003) 250 | |
| 43 | CMS Collaboration | Charged-particle nuclear modification factors in PbPb and pPb collisions at ${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 5.02 TeV | JHEP 04 (2017) 039 | CMS-HIN-15-015 1611.01664 |
| 44 | CMS Collaboration | The CMS trigger system | JINST 12 (2017) P01020 | CMS-TRG-12-001 1609.02366 |
| 45 | CMS Collaboration | CMS luminosity calibration for the pp reference run at $ \sqrt{s} = $ 5.02 TeV | CMS-PAS-LUM-16-001 | CMS-PAS-LUM-16-001 |
| 46 | T. Sjostrand et al. | An introduction to PYTHIA 8.2 | CPC 191 (2015) 159 | 1410.3012 |
| 47 | CMS Collaboration | Event generator tunes obtained from underlying event and multiparton scattering measurements | EPJC 76 (2016) 155 | CMS-GEN-14-001 1512.00815 |
| 48 | 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 |
| 49 | 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 | |
| 50 | CMS Collaboration | Strange particle production in pp collisions at $ \sqrt{s} = $ 0.9 and 7 TeV | JHEP 05 (2011) 064 | CMS-QCD-10-007 1102.4282 |
| 51 | Particle Data Group, C. Patrignani et al. | Review of particle physics | CPC 40 (2016) 100001 | |
| 52 | CMS Collaboration | Measurement of tracking efficiency | CMS-PAS-TRK-10-002 | |
| 53 | PHENIX Collaboration | Spectra and ratios of identified particles in Au+Au and d+Au collisions at ${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 200 GeV | PRC 88 (2013) 024906 | 1304.3410 |
| 54 | J. L. Albacete et al. | Predictions for p+Pb collisions at ${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 5.02 TeV | Int. J. Mod. Phys. E 22 (2013) 1330007 | 1301.3395 |
|
|
Compact Muon Solenoid LHC, CERN |
|
|
|
|
|
|