CMS-PAS-HIN-17-003

CMS-PAS-HIN-17-003
Elliptic flow of charm and strange hadrons in high-multiplicity pPb collisions at $\sqrt{\smash[b]{s_{\mathrm{NN}}}} =$ 8.16 TeV
CMS Collaboration
February 2018

Abstract: First measurements of the elliptic flow of prompt $\mathrm{D^{0}}$ mesons in comparison to $\mathrm{K^0_S}$ , $\Lambda$ , $\Xi^{-}$ , and $\Omega^{-}$ hadrons in pPb collisions at $\sqrt{\smash[b]{s_{\mathrm{NN}}}} =$ 8.16 TeV are reported. The results are based on data collected by the CMS experiment at the LHC and are presented for particles at midrapidity with transverse momentum up to 8 GeV/c after correcting for the contribution of back-to-back jet correlations. The results are compared to PbPb collision data at $\sqrt{\smash[b]{s_{\mathrm{NN}}}} =$ 5.02 TeV for 30-50% centrality. A significant elliptic flow ( $v_2$ ) signal is observed for all particles, in very high-multiplicity (about 200 charged particles) pPb events. When divided by the number of constituent quarks and studied as function of the transverse kinetic energy per quark, the $\mathrm{D^{0}}$ $v_2$ values are observed to be significantly smaller than those of light flavor particles, an effect not observed in PbPb collisions. These results show a weaker collective flow associated with charm quarks than with light flavor quarks in high-multiplicity pPb collisions, and may indicate a weaker coupling between heavy quarks and the hypothesised hydrodynamic quark-gluon plasma.
Links: CDS record (PDF) ; inSPIRE record ; CADI line (restricted) ; These preliminary results are superseded in this paper, PRL 121 (2018) 082301. The superseded preliminary plots can be found here.

Figures	Summary	References	CMS Publications

Figures
png pdf	Figure 1: Example of the simultaneous fit to the invariant mass spectrum and $v_{2}^{S+B}(m_{\rm inv})$ in the ${p_{{\mathrm {T}}}}$ interval 4.2-5 GeV/ $c$ for events with 185 $\leq {N_{\mathrm {trk}^{\mathrm {offline}}}} <$ 250.
png pdf	Figure 2: Top: the $v_{2}^\text {sub}$ results for prompt ${\mathrm {D^{0}}}$ meson, as well as for strange hadrons as a function of ${p_{{\mathrm {T}}}}$ for pPb collisions at $\sqrt{\smash[b]{s_{\mathrm{NN}}}} =$ 8.16 TeV with 185 $\leq {N_{\mathrm {trk}^{\mathrm {offline}}}} <$ 250 (left) and PbPb collisions at $\sqrt{\smash[b]{s_{\mathrm{NN}}}} =$ 5.02 TeV with centrality between 30 and 50% (right). Bottom: the $n_{\mathrm {q}}$ -scaled $v_{2}^\text {sub}$ results. The ${\mathrm {D^{0}}}$ $v_2$ data in PbPb are taken from Ref. [40]. The error bars correspond to statistical uncertainties, while the shaded areas denote the systematic uncertainties.

Summary

First measurements of elliptic azimuthal anisotropies for prompt

$\mathrm{D^{0}}$ mesons in comparison to

$\mathrm{K^0_S}$ ,

$\Lambda$ ,

$\Xi^{-}$ , and

$\Omega^{-}$ hadrons in high-multiplicity pPb collisions at

$\sqrt{\smash[b]{s_{\mathrm{NN}}}} =$ 8.16TeV are presented. Significant positive

$v_2$ values are observed for

$\mathrm{D^{0}}$ mesons with

${p_{{\mathrm {T}}}} >$ 2 GeV/

$c$ . Comparing to strange hadron results, the

$\mathrm{D^{0}}$

$v_2$ values are found to be smaller at a given

${p_{{\mathrm {T}}}}$ value, or at similar transverse kinetic energy per constituent quark after normalizing

$v_2$ by the number of constituent quarks. This effect is not observed in PbPb collisions with centrality between 30 and 50%. These results may indicate a weaker coupling between heavy quarks and the hypothesised hydrodynamic QGP medium in small collision systems.

References
1	PHOBOS Collaboration	System size dependence of cluster properties from two- particle angular correlations in Cu+Cu and Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}\ =$ 200 GeV	PRC 81 (2010) 024904	0812.1172
2	STAR Collaboration	Distributions of charged hadrons associated with high transverse momentum particles in pp and Au + Au collisions at $\sqrt{s_{\mathrm{NN}}}\ =$ 200 GeV	PRL 95 (2005) 152301	nucl-ex/0501016
3	STAR Collaboration	Long range rapidity correlations and jet production in high energy nuclear collisions	PRC 80 (2009) 064912	0909.0191
4	PHOBOS Collaboration	High transverse momentum triggered correlations over a large pseudorapidity acceptance in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}\ =$ 200 GeV	PRL 104 (2010) 062301	0903.2811
5	CMS Collaboration	Long-range and short-range dihadron angular correlations in central PbPb collisions at a nucleon-nucleon center of mass energy of 2.76 TeV	JHEP 07 (2011) 076	CMS-HIN-11-001 1105.2438
6	CMS Collaboration	Centrality dependence of dihadron correlations and azimuthal anisotropy harmonics in PbPb collisions at $\sqrt{s_{\mathrm{NN}}}\ =$ 2.76 TeV	EPJC 72 (2012) 2012	CMS-HIN-11-006 1201.3158
7	ALICE Collaboration	Elliptic flow of charged particles in Pb-Pb collisions at 2.76 TeV	PRL 105 (2010) 252302	1011.3914
8	ATLAS Collaboration	Measurement of the azimuthal anisotropy for charged particle production in $\sqrt{s_{\mathrm{NN}}}\ =$ 2.76 TeV lead-lead collisions with the ATLAS detector	PRC 86 (2012) 014907	1203.3087
9	CMS Collaboration	Measurement of the elliptic anisotropy of charged particles produced in PbPb collisions at nucleon-nucleon center-of-mass energy = 2.76 TeV	PRC 87 (2013) 014902	CMS-HIN-10-002 1204.1409
10	CMS Collaboration	Studies of azimuthal dihadron correlations in ultra-central PbPb collisions at $\sqrt{s_{\mathrm{NN}}}\ =$ 2.76 TeV	JHEP 02 (2014) 088	CMS-HIN-12-011 1312.1845
11	J.-Y. Ollitrault	Anisotropy as a signature of transverse collective flow	PRD 46 (1992) 229
12	U. Heinz and R. Snellings	Collective flow and viscosity in relativistic heavy-ion collisions	Ann. Rev. Nucl. Part. Sci. 63 (2013) 123	1301.2826
13	C. Gale, S. Jeon, and B. Schenke	Hydrodynamic Modeling of Heavy-Ion Collisions	Int. J. Mod. Phys. A 28 (2013) 1340011	1301.5893
14	CMS Collaboration	Observation of Long-Range Near-Side Angular Correlations in Proton-Proton Collisions at the LHC	JHEP 09 (2010) 091	CMS-QCD-10-002 1009.4122
15	ATLAS Collaboration	Observation of Long-Range Elliptic Azimuthal Anisotropies in $\sqrt{s}=$ 13 and 2.76 $TeV pp$ Collisions with the ATLAS Detector	PRL 116 (2016) 172301	1509.04776
16	CMS Collaboration	Measurement of long-range near-side two-particle angular correlations in pp collisions at $\sqrt s =$ 13 TeV	PRL 116 (2016) 172302	CMS-FSQ-15-002 1510.03068
17	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
18	ALICE Collaboration	Long-range angular correlations on the near and away side in $\mathrm{pPb}\$ collisions at $\sqrt{s_{\mathrm{NN}}}\ =$ 5.02 TeV	PLB 719 (2013) 29	1212.2001
19	ATLAS Collaboration	Observation of associated near-side and away-side long-range correlations in $\sqrt{s_{NN}} =$ 5.02 TeV proton-lead collisions with the ATLAS detector	PRL 110 (2013) 182302	1212.5198
20	LHCb Collaboration	Measurements of long-range near-side angular correlations in $\sqrt{s_{\text{NN}}}=$ 5 TeV proton-lead collisions in the forward region	PLB 762 (2016) 473	1512.00439
21	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
22	B. H. Alver, C. Gombeaud, M. Luzum, and J.-Y. Ollitrault	Triangular flow in hydrodynamics and transport theory	PRC 82 (2010) 034913	1007.5469
23	B. Schenke, S. Jeon, and C. Gale	Elliptic and triangular flow in event-by-event D=3+1 viscous hydrodynamics	PRL 106 (2011) 042301	1009.3244
24	Z. Qiu, C. Shen, and U. Heinz	Hydrodynamic elliptic and triangular flow in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}\ =$ 2.76 TeV	PLB 707 (2012) 151	1110.3033
25	PHENIX Collaboration	Measurement of long-range angular correlation and quadrupole anisotropy of pions and (anti)protons in central $d +$ Au collisions at $\sqrt{s_{\mathrm{NN}}}\ =$ 200 GeV	PRL 114 (2015) 192301	1404.7461
26	STAR Collaboration	Long-range pseudorapidity dihadron correlations in $d$ +Au collisions at $\sqrt{s_{\rm NN}}=$ 200 GeV	PLB 747 (2015) 265	1502.07652
27	PHENIX Collaboration	Measurements of multiparticle correlations in $d +$ Au collisions at 200, 62.4, 39, and 19.6 GeV and $p +$ Au collisions at 200 GeV and implications for collective behavior	Submitted to PRLett	1707.06108
28	PHENIX Collaboration	Measurements of elliptic and triangular flow in high-multiplicity $^{3}$ He $+$ Au collisions at $\sqrt{s_{\mathrm{NN}}}\ =$ 200 GeV	PRL 115 (2015) 142301	1507.06273
29	ALICE Collaboration	Long-range angular correlations of pi, K and p in p--Pb collisions at $\sqrt{s_{\mathrm{NN}}}\ =$ 5.02 TeV	PLB 726 (2013) 164	1307.3237
30	CMS Collaboration	Long-range two-particle correlations of strange hadrons with charged particles in pPb and PbPb collisions at LHC energies	PLB 742 (2015) 200	CMS-HIN-14-002 1409.3392
31	CMS Collaboration	Evidence for collectivity in pp collisions at the LHC	PLB 765 (2017) 193	CMS-HIN-16-010 1606.06198
32	CMS Collaboration	Evidence for collective multi-particle correlations in pPb collisions	PRL 115 (2015) 012301	CMS-HIN-14-006 1502.05382
33	ATLAS Collaboration	Measurement of multi-particle azimuthal correlations in $pp$ , $p+$ Pb and low-multiplicity Pb $+$ Pb collisions with the ATLAS detector	EPJC 77 (2017) 428	1705.04176
34	ATLAS Collaboration	Measurement of multi-particle azimuthal correlations with the subevent cumulant method in $pp$ and $p$ +Pb collisions with the ATLAS detector at the LHC	Submitted to PRC	1708.03559
35	K. Dusling, W. Li, and B. Schenke	Novel collective phenomena in high-energy proton–proton and proton–nucleus collisions	Int. J. Mod. Phys. E 25 (2016) 1630002	1509.07939
36	P. Braun-Munzinger	Quarkonium production in ultra-relativistic nuclear collisions: Suppression versus enhancement	JPG 34 (2007) S471	nucl-th/0701093
37	STAR Collaboration	Measurement of ${\mathrm{D^0}}$ Azimuthal Anisotropy at Midrapidity in Au + Au Collisions at $\sqrt{s_{\mathrm{NN}}} =$ 200 GeV	PRL 118 (2017) 212301	1701.06060
38	ALICE Collaboration	Azimuthal anisotropy of D meson production in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}} =$ 2.76 TeV	PRC 90 (2014) 034904	1405.2001
39	ALICE Collaboration	D-meson azimuthal anisotropy in mid-central Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}} =$ 5.02 TeV	Submitted to PRLett	1707.01005
40	CMS Collaboration	Measurement of prompt D $^{0}$ meson azimuthal anisotropy in PbPb collisions at $\sqrt{s_{\mathrm{NN}}}\ =$ 5.02 TeV	Submitted to PRLett	CMS-HIN-16-007 1708.03497
41	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
42	CMS Collaboration	The CMS experiment at the CERN LHC	JINST 3 (2008) S08004	CMS-00-001
43	CMS Collaboration	Constraints on the chiral magnetic effect using charge-dependent azimuthal correlations in pPb and PbPb collisions at the LHC	Submitted to PRC	CMS-HIN-17-001 1708.01602
44	CMS Collaboration	Observation of correlated azimuthal anisotropy Fourier harmonics in pp and pPb collisions at the LHC	Submitted to PRLett	CMS-HIN-16-022 1709.09189
45	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
46	T. Sjostrand, S. Mrenna, and P. Z. Skands	A Brief Introduction to PYTHIA 8.1	CPC 178 (2008) 852	0710.3820
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	S. Porteboeuf, T. Pierog, and K. Werner	Producing Hard Processes Regarding the Complete Event: The EPOS Event Generator	in Proceedings, 45th Rencontres de Moriond on QCD and High Energy Interactions: La Thuile, Italy, March 13-20, 2010, p. 135, Gioi Publishers Gioi Publishers	1006.2967
49	CMS Collaboration	Multiplicity and transverse momentum dependence of two- and four-particle correlations in $\mathrm{pPb}\$ and $\mathrm{PpPb}\$ collisions	PLB 724 (2013) 213	CMS-HIN-13-002 1305.0609
50	M. Nahrgang et al.	Elliptic and triangular flow of heavy flavor in heavy-ion collisions	PRC 91 (2015) 014904	1410.5396
51	M. He, R. J. Fries, and R. Rapp	Heavy Flavor at the Large Hadron Collider in a Strong Coupling Approach	PLB 735 (2014) 445	1401.3817
52	J. Xu, J. Liao, and M. Gyulassy	Bridging Soft-Hard Transport Properties of Quark-Gluon Plasmas with CUJET3.0	JHEP 02 (2016) 169	1508.00552