CMS-HIN-19-002 ; CERN-EP-2020-039 | ||
Measurement of the azimuthal anisotropy of Υ(1S) and Υ(2S) mesons in PbPb collisions at √sNN= 5.02 TeV | ||
CMS Collaboration | ||
14 June 2020 | ||
Phys. Lett. B 819 (2021) 136385 | ||
Abstract: The second-order Fourier coefficients (v2) characterizing the azimuthal distribution of Υ(1S) and Υ(2S) mesons arising from PbPb collisions at √sNN= 5.02 TeV are studied. The Υ mesons are reconstructed in their dimuon decay channel, as measured by the CMS detector. The data set was collected in 2018 and corresponds to an integrated luminosity of 1.7 nb−1. The scalar product method is used to extract the v2 coefficients of the azimuthal distribution. Results are reported for the rapidity range |y|< 2.4, with the transverse momentum 0 <pT< 50 GeV/c, and in three centrality ranges of 10-30, 30-50 and 50-90%. In contrast to the J/ψ mesons, no azimuthal anisotropy is observed for the Υ mesons. | ||
Links: e-print arXiv:2006.07707 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; HepData record ; CADI line (restricted) ; |
Figures | |
![]() png pdf |
Figure 1:
Simultaneous fit of the dimuon invariant mass spectrum and the v2Sig+Bkg distribution, as defined in Eq. (4), for pT< 50 GeV/c and with centrality 10-90%. The solid (signal + background) and dashed (background only) blue lines show the result of the mass fit, and the solid and dashed red lines show the corresponding results for the binned χ2 fit to the v2 distribution. |
![]() png pdf |
Figure 2:
(left) pT integrated v2 values for Υ(1S) mesons measured in four centrality bins and for the Υ(2S) meson in the 10-90% centrality range. (right) v2 of Υ(1S) mesons as a function of pT in the 10-90% centrality range compared with model calculations from Du and Rapp [22], Yao [42,43], Hong and Lee [44,45], and Bhaduri, Borghini, Jaiswal and Strickland [46]. All results are for the rapidity range of |y|< 2.4. The vertical bars denote statistical uncertainties, and the rectangular boxes show the total systematic uncertainties. |
![]() png pdf |
Figure 2-a:
pT integrated v2 values for Υ(1S) mesons measured in four centrality bins and for the Υ(2S) meson in the 10-90% centrality range. All results are for the rapidity range of |y|< 2.4. The vertical bars denote statistical uncertainties, and the rectangular boxes show the total systematic uncertainties. |
![]() png pdf |
Figure 2-b:
v2 of Υ(1S) mesons as a function of pT in the 10-90% centrality range compared with model calculations from Du and Rapp [22], Yao [42,43], Hong and Lee [44,45], and Bhaduri, Borghini, Jaiswal and Strickland [46]. All results are for the rapidity range of |y|< 2.4. The vertical bars denote statistical uncertainties, and the rectangular boxes show the total systematic uncertainties. |
![]() png pdf |
Figure 3:
The v2 coefficients for Υ(1S) mesons as a function of pT in three centrality bins: 10-30% (left), 30-50% (middle) and 50-90% (right). The rapidity range is |y|< 2.4. The vertical lines indicate the statistical uncertainties and the rectangular boxes show the total systematic uncertainties. |
![]() png pdf |
Figure 4:
The v2 for Υ(1S) mesons as a function of pT in the rapidity range |y|< 2.4 compared with the ALICE results for Υ(1S) (open circles) and J/ψ (full squares) mesons measured in 2.5 <y< 4 [24]. All results are measured in the range of 0 <pT< 15 GeV/c and centrality interval 5-60%. The vertical bars denote statistical uncertainties, and the rectangular boxes show the total systematic uncertainties. |
Summary |
The v2 coefficients for Υ(1S) and Υ(2S) mesons are measured in PbPb collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV. Results are reported for the rapidity range |y|< 2.4, with transverse momentum 0 <pT< 50 GeV/c, and in three centrality intervals of 10-30, 30-50, and 50-90% for the Υ(1S) meson, while the centrality interval 10-90% is used for the Υ(2S) meson. The v2 values are observed to be compatible with zero for the Υ(1S) meson in the measured kinematic bins and centrality intervals. This observation contrasts with the positive v2 values reported for J/ψ mesons, suggesting different medium effects for charmonia and bottomonia. The measured values of v2 are consistent with the predictions of several theoretical models. The v2 value found for Υ(2S) mesons, which is being reported for the first time, is also consistent with zero. As there are expected to be differences in the various processes through which the QGP affects Υ(1S) and Υ(2S) mesons, these measurements provide new inputs for the study of bottomonia production in heavy ion collisions. |
References | ||||
1 | W. Busza, K. Rajagopal, and W. van der Schee | Heavy ion collisions: the big picture and the big questions | Annual Review of Nuclear and Particle Science 68 (2018) 339 | 1802.04801 |
2 | F. Karsch, E. Laermann, and A. Peikert | The pressure in 2, 2+1 and 3 flavor QCD | PLB 478 (2000) 447 | hep-lat/0002003 |
3 | E. V. Shuryak | Theory of hadronic plasma | Sov. Phys. JETP 47 (1978) 212.[Zh. Eksp. Teor. Fiz., 74 (1978) 408] | |
4 | T. Matsui and H. Satz | J/ψ suppression by quark-gluon plasma formation | PLB 178 (1986) 416 | |
5 | CMS Collaboration | Observation of sequential Upsilon suppression in PbPb collisions | PRL 109 (2012) 222301 | CMS-HIN-11-011 1208.2826 |
6 | CMS Collaboration | Suppression of √sNN, \Upsilon(\text{2S}), and \Upsilon(\text{3S}) quarkonium states in PbPb collisions at √sNN= 2.76 TeV | PLB 770 (2017) 357 | CMS-HIN-15-001 1611.01510 |
7 | ALICE Collaboration | Υ suppression at forward rapidity in Pb-Pb collisions at √sNN= 5.02 TeV | PLB 790 (2019) 89 | 1805.04387 |
8 | CMS Collaboration | Suppression of excited Υ states relative to the ground state in Pb-Pb collisions at √sNN= 5.02 TeV | PRL 120 (2018) 142301 | CMS-HIN-16-008 1706.05984 |
9 | CMS Collaboration | Measurement of nuclear modification factors of √sNN, \Upsilon(\text{2S}), and \Upsilon(\text{3S}) mesons in PbPb collisions at √sNN= 5.02 TeV | PLB 790 (2019) 270 | CMS-HIN-16-023 1805.09215 |
10 | STAR Collaboration | Suppression of Υ production in d+Au and Au+Au collisions at √sNN= 200 GeV | PLB 735 (2014) 127 | 1312.3675 |
11 | A. Andronic et al. | Heavy-flavour and quarkonium production in the LHC era: from proton--proton to heavy-ion collisions | EPJC 76 (2016) 107 | 1506.03981 |
12 | L. He et al. | Anisotropic parton escape is the dominant source of azimuthal anisotropy in transport models | PLB 753 (2016) 506 | 1502.05572 |
13 | N. Borghini and C. Gombeaud | Anisotropic flow far from equilibrium | EPJC 71 (2011) 1612 | 1012.0899 |
14 | P. Romatschke | Collective flow without hydrodynamics: simulation results for relativistic ion collisions | EPJC 75 (2015) 429 | 1504.02529 |
15 | A. Jaiswal and P. P. Bhaduri | Effect of an anisotropic escape mechanism on elliptic flow in relativistic heavy-ion collisions | PRC 97 (2018) 044909 | 1712.02707 |
16 | S. Voloshin and Y. Zhang | Flow study in relativistic nuclear collisions by fourier expansion of azimuthal particle distributions | Z. Phys. C 70 (1996) 665 | hep-ph/9407282 |
17 | ALICE Collaboration | Search for collectivity with azimuthal J/ψ-hadron correlations in high multiplicity p-Pb collisions at √sNN= 5.02 and 8.16 TeV | PLB 780 (2018) 7 | 1709.06807 |
18 | ALICE Collaboration | J/ψ elliptic flow in Pb-Pb collisions at √sNN= 5.02 TeV | PRL 119 (2017) 242301 | 1709.05260 |
19 | CMS Collaboration | Suppression and azimuthal anisotropy of prompt and nonprompt J/ψ production in PbPb collisions at √sNN= 2.76 TeV | EPJC 77 (2017) 252 | CMS-HIN-14-005 1610.00613 |
20 | B. Krouppa and M. Strickland | Predictions for bottomonia suppression in 5.023 TeV Pb--Pb collisions | Universe 2 (2016) 16 | 1605.03561 |
21 | N. Brambilla, M. A. Escobedo, J. Soto, and A. Vairo | Quarkonium suppression in heavy-ion collisions: an open quantum system approach | PRD 96 (2017) 034021 | 1612.07248 |
22 | X. Du, R. Rapp, and M. He | Color screening and regeneration of bottomonia in high-energy heavy-ion collisions | PRC 96 (2017) 054901 | 1706.08670 |
23 | A. Emerick, X. Zhao, and R. Rapp | Bottomonia in the quark-gluon plasma and their production at RHIC and LHC | EPJA 48 (2012) 72 | 1111.6537 |
24 | ALICE Collaboration | Measurement of √sNN elliptic flow at forward rapidity in Pb-Pb collisions at √sNN= 5.02 TeV | PRL 123 (2019) 192301 | 1907.03169 |
25 | M. Luzum and J.-Y. Ollitrault | Eliminating experimental bias in anisotropic-flow measurements of high-energy nuclear collisions | PRC 87 (2013) 044907 | 1209.2323 |
26 | CMS Collaboration | The CMS experiment at the CERN LHC | JINST 3 (2008) S08004 | CMS-00-001 |
27 | CMS Collaboration | The CMS trigger system | JINST 12 (2017) P01020 | CMS-TRG-12-001 1609.02366 |
28 | 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 |
29 | CMS Collaboration | Transverse momentum and pseudorapidity distributions of charged hadrons in pp collisions at √s= 0.9 and 2.36 TeV | JHEP 02 (2010) 041 | CMS-QCD-09-010 1002.0621 |
30 | T. Sjostrand et al. | An introduction to PYTHIA 8.2 | CPC 191 (2015) 159 | 1410.3012 |
31 | CMS Collaboration | Extraction and validation of a new set of CMS PYTHIA8 tunes from underlying-event measurements | EPJC 80 (2020) 4 | CMS-GEN-17-001 1903.12179 |
32 | R. Baier and R. Ruckl | Hadronic collisions: a quarkonium factory | Z. Phys. C 19 (1983) 251 | |
33 | R. Gastmans, W. Troost, and T. T. Wu | Cross-sections for gluon + gluon → heavy quarkonium + gluon | PLB 184 (1987) 257 | |
34 | P. L. Cho and A. K. Leibovich | Color-octet quarkonia production. II. | PRD 53 (1996) 6203 | hep-ph/9511315 |
35 | GEANT4 Collaboration | GEANT4--a simulation toolkit | NIMA 506 (2003) 250 | |
36 | I. P. Lokhtin et al. | Heavy ion event generator HYDJET++ (hydrodynamics plus jets) | CPC 180 (2009) 779 | 0809.2708 |
37 | CMS Collaboration | Measurements of inclusive W and Z cross sections in pp collisions at √s= 7 TeV | JHEP 01 (2011) 080 | CMS-EWK-10-002 1012.2466 |
38 | CMS Collaboration | Performance of CMS muon reconstruction in pp collision events at √s= 7 TeV | JINST 7 (2012) P10002 | CMS-MUO-10-004 1206.4071 |
39 | CMS Collaboration | Measurement of prompt D0 meson azimuthal anisotropy in Pb-Pb collisions at √sNN= 5.02 TeV | PRL 120 (2018) 202301 | CMS-HIN-16-007 1708.03497 |
40 | M. J. Oreglia | A study of the reactions ψ′→γγψ | PhD thesis, Stanford University, 1980 SLAC Report SLAC-R-236, see A | |
41 | Particle Data Group, M. Tanabashi et al. | Review of particle physics | PRD 98 (2018) 030001 | |
42 | X. Yao et al. | Coupled Boltzmann transport equations of heavy quarks and quarkonia in quark-gluon plasma | 2004.06746 | |
43 | X. Yao and B. Muller | Quarkonium inside the quark-gluon plasma: diffusion, dissociation, recombination, and energy loss | PRD 100 (2019) 014008 | 1811.09644 |
44 | J. Hong and S. H. Lee | √sNN transverse momentum spectra through dissociation and regeneration in heavy ion collisions | PLB 801 (2020) 135147 | 1909.07696 |
45 | W. Ke, Y. Xu, and S. A. Bass | Linearized Boltzmann-Langevin model for heavy quark transport in hot and dense QCD matter | PRC 98 (2018) 064901 | 1806.08848 |
46 | P. P. Bhaduri, N. Borghini, A. Jaiswal, and M. Strickland | Anisotropic escape mechanism and elliptic flow of bottomonia | PRC 100 (2019) 051901 | 1809.06235 |
![]() |
Compact Muon Solenoid LHC, CERN |
![]() |
![]() |
![]() |
![]() |
![]() |
![]() |