CMS-HIN-16-007

CMS-HIN-16-007 ; CERN-EP-2017-174
Measurement of prompt $\mathrm{D}^0$ meson azimuthal anisotropy in PbPb collisions at $\sqrt{s_{_\mathrm{NN}}} =$ 5.02 TeV
CMS Collaboration
11 August 2017
Phys. Rev. Lett. 120 (2018) 202301
Abstract: The prompt $\mathrm{D}^0$ meson azimuthal anisotropy coefficients, $v_{2}$ and $v_{3}$ , are measured at midrapidity ( $\|y\| <$ 1.0) in PbPb collisions at a center-of-mass energy $\sqrt{ s_{_\mathrm{NN}}} =$ 5.02 TeV per nucleon pair with data collected by the CMS experiment. The measurement is performed in the transverse momentum ( $p_{\mathrm{T}}$ ) range of 1 to 40 GeV/ $c$ , for central and midcentral collisions. The $v_{2}$ coefficient is found to be positive throughout the $p_{\mathrm{T}}$ range studied. The first measurement of the prompt $\mathrm{D}^0$ meson $v_{3}$ coefficient is performed, and values up to 0.07 are observed for $p_{\mathrm{T}}$ around 4 GeV/ $c$ . Compared to measurements of charged particles, a similar $p_{\mathrm{T}}$ dependence, but smaller magnitude for $p_{\mathrm{T}} <$ 6 GeV/ $c$ , is found for prompt $\mathrm{D}^0$ meson $v_{2}$ and $v_{3}$ coefficients. The results are consistent with the presence of collective motion of charm quarks at low $p_{\mathrm{T}}$ and a path length dependence of charm quark energy loss at high $p_{\mathrm{T}}$ , thereby providing new constraints on the theoretical description of the interactions between charm quarks and the quark-gluon plasma.
Links: e-print arXiv:1708.03497 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; HepData record ; CADI line (restricted) ;

Figures	Summary	References	CMS Publications

Figures
png pdf	Figure 1: Example of simultaneous fit to the invariant mass spectrum and $v_{2}^{S+B}(m_{\rm inv})$ in the ${p_{\mathrm {T}}}$ interval 4-5 GeV/ $c$ for the centrality class 10-30%.
png pdf	Figure 2: Prompt $\mathrm{D}^0$ meson $v_{2}$ (upper) and $v_{3}$ (lower) coefficients at midrapidity ( $\|y\| <$ 1.0) for the centrality classes 0-10% (left), 10-30% (middle), and 30-50% (right). The vertical bars represent statistical uncertainties, grey bands represent systematic uncertainties from nonprompt $\mathrm{D}^0$ mesons and open boxes represent other systematic uncertainties. The measured $v_{n}$ coefficient of charged particles at midpseudorapidity ( $\|\eta \| <$ 1.0) [36] and theoretical calculations for prompt D meson $v_{n}$ coefficient [37,25,38,39,40] are also plotted for comparison.

Summary

In summary, measurements of prompt

$\mathrm{D}^0$ meson azimuthal anisotropy coefficients,

$v_{2}$ and

$v_{3}$ , using the scalar product method in PbPb collisions at

$\sqrt{ s_{_\mathrm{NN}}} =$ 5.02 TeV have been presented. The

$v_{2}$ values are found to be positive in the

$p_{\mathrm{T}}$ range of 1 to 40 GeV/

$c$ . The

$v_{3}$ coefficient is measured for the first time, and values up to 0.07 are observed for

$p_{\mathrm{T}}$ around 4 GeV/

$c$ . The

$v_{2}$ coefficient is observed to be centrality dependent, while the

$v_{3}$ coefficient shows little centrality dependence. Compared with those of charged particles, the measured

$\mathrm{D}^0$ meson

$v_{2}$ and

$v_{3}$ coefficients are found to be smaller for

$p_{\mathrm{T}} <$ 6 GeV/

$c$ but to have similar

$p_{\mathrm{T}}$ dependence. Through the comparison with theoretical calculations, the

$v_{2}$ and

$v_{3}$ results at low

$p_{\mathrm{T}}$ suggest that the charm quarks take part in the collective motion of the system. The

$v_{2}$ values for

$p_{\mathrm{T}} >$ 6 GeV/

$c$ , which are consistent with those of charged particles, suggest that the path length dependence of charm quark energy loss is similar to that of light quarks. The results provide new constraints on models of the interactions between charm quarks and the quark-gluon plasma, and the charm quark energy loss mechanisms.

References
1	STAR Collaboration	Experimental and theoretical challenges in the search for the quark gluon plasma: The STAR collaboration's critical assessment of the evidence from RHIC collisions	NP A 757 (2005) 102	nucl-ex/0501009
2	PHENIX Collaboration	Formation of dense partonic matter in relativistic nucleus-nucleus collisions at RHIC: Experimental evaluation by the PHENIX collaboration	NP A 757 (2005) 184	nucl-ex/0410003
3	BRAHMS Collaboration	Quark gluon plasma and color glass condensate at RHIC? The perspective from the BRAHMS experiment	NP A 757 (2005) 1	nucl-ex/0410020
4	PHOBOS Collaboration	The PHOBOS perspective on discoveries at RHIC	NP A 757 (2005) 28	nucl-ex/0410022
5	B. Muller, J. Schukraft, and B. Wyslouch	First results from Pb+Pb collisions at the LHC	Ann. Rev. Nucl. Part. Sci. 62 (2012) 361	1202.3233
6	N. Armesto and E. Scomparin	Heavy-ion collisions at the Large Hadron Collider: a review of the results from Run 1	EPJPlus 131 (2016) 52	1511.02151
7	A. M. Poskanzer and S. A. Voloshin	Methods for analyzing anisotropic flow in relativistic nuclear collisions	PRC 58 (1998) 1671	nucl-ex/9805001
8	P. Braun-Munzinger	Quarkonium production in ultra-relativistic nuclear collisions: Suppression versus enhancement	JPG 34 (2007) S471	nucl-th/0701093
9	F.-M. Liu and S.-X. Liu	Quark-gluon plasma formation time and direct photons from heavy ion collisions	PRC 89 (2014) 034906	1212.6587
10	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
11	D. Molnar and S. A. Voloshin	Elliptic Flow at Large Transverse Momenta from Quark Coalescence	PRL 91 (2003) 092301	nucl-th/0302014
12	V. Greco, C. M. Ko, and P. L\' evai	Parton Coalescence and Antiproton/Pion Anomaly at RHIC	PRL 90 (2003) 202302	nucl-th/0301093
13	M. Gyulassy, I. Vitev, and X. N. Wang	High $p_{\mathrm{T}}$ Azimuthal Asymmetry in Noncentral $A+A$ at RHIC	PRL 86 (2001) 2537	nucl-th/0012092
14	E. V. Shuryak	Azimuthal asymmetry at large $p_t$ seem to be too large for a ``jet quenching''	PRC 66 (2002) 027902	nucl-th/0112042
15	STAR Collaboration	Observation of $\mathrm{D}^0$ Meson Nuclear Modifications in Au+Au Collisions at $\sqrt{s_{_\mathrm{NN}}} =$ 200 GeV	PRL 113 (2014) 142301	1404.6185
16	ALICE Collaboration	Transverse momentum dependence of D-meson production in Pb-Pb collisions at $\sqrt{s_{_\mathrm{NN}}} =$ 2.76 TeV	JHEP 03 (2016) 081	1509.06888
17	PHENIX Collaboration	Energy Loss and Flow of Heavy Quarks in Au+Au Collisions at $\sqrt{s_{_\mathrm{NN}}} =$ 200 GeV	PRL 98 (2007) 172301	nucl-ex/0611018
18	PHENIX Collaboration	Heavy quark production in $p+p$ and energy loss and flow of heavy quarks in Au + Au collisions at $\sqrt{s_{_\mathrm{NN}}} =$ 200 GeV	PRC 84 (2011) 044905	1005.1627
19	STAR Collaboration	Elliptic flow of electrons from heavy-flavor hadron decays in Au + Au collisions at $\sqrt{s_{_\mathrm{NN}}} =$ 200, 62.4, and 39 GeV	PRC 95 (2017) 034907	1405.6348
20	ALICE Collaboration	Elliptic flow of electrons from heavy-flavour hadron decays at mid-rapidity in PbPb collisions at $\sqrt{s_{_\mathrm{NN}}} =$ 2.76 TeV	JHEP 09 (2016) 028	1606.00321
21	ALICE Collaboration	Elliptic flow of muons from heavy-flavour hadron decays at forward rapidity in PbPb collisions at $\sqrt{s_{_\mathrm{NN}}} =$ 2.76 TeV	PLB 753 (2016) 41	1507.03134
22	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
23	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
24	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
25	M. Nahrgang et al.	Elliptic and triangular flow of heavy flavor in heavy-ion collisions	PRC 91 (2015) 014904	1410.5396
26	STAR Collaboration	Elliptic flow from two and four particle correlations in Au+Au collisions at $\sqrt{s_{_\mathrm{NN}}} =$ 130 GeV	PRC 66 (2002) 034904	nucl-ex/0206001
27	M. Luzum and J.-Y. Ollitrault	Eliminating experimental bias in anisotropic-flow measurements of high-energy nuclear collisions	PRC 87 (2013) 044907	1209.2323
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	The CMS Experiment at the CERN LHC	JINST 3 (2008) S08004	CMS-00-001
30	Particle Data Group, C. Patrignani et al.	Review of Particle Physics	CPC 40 (2016) 100001
31	G. E. Forden and D. H. Saxon	Improving vertex position determination by using a kinematic fit	NIMA 248 (1986) 439
32	E877 Collaboration	Proton and pion production relative to the reaction plane in Au+Au collisions at AGS energies	PRC 56 (1997) 3254	nucl-ex/9707002
33	T. Sjostrand, S. Mrenna, and P. Z. Skands	A brief introduction to PYTHIA 8.1	CPC 178 (2008) 852	0710.3820
34	CMS Collaboration	Event generator tunes obtained from underlying event and multiparton scattering measurements	EPJC 76 (2016) 155	CMS-GEN-14-001 1512.00815
35	I. P. Lokhtin and A. M. Snigirev	A model of jet quenching in ultrarelativistic heavy ion collisions and high- $p_{\mathrm{T}}$ hadron spectra at RHIC	EPJC 45 (2006) 211	hep-ph/0506189
36	CMS Collaboration	Azimuthal anisotropy of charged particles with transverse momentum up to 100 $GeVc$ in PbPb collisions at $\sqrt{s_{_\mathrm{NN}}} =$ 5.02 TeV	Submitted to \it PLB	CMS-HIN-15-014 1702.00630
37	S. Cao, T. Luo, G.-Y. Qin, and X.-N. Wang	Linearized Boltzmann transport model for jet propagation in the quark-gluon plasma: Heavy quark evolution	PRC 94 (2016) 014909	1605.06447
38	T. Song et al.	Charm production in Pb+Pb collisions at energies available at the CERN Large Hadron Collider	PRC 93 (2016) 034906	1512.00891
39	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
40	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
41	CMS Collaboration	Measurement of the elliptic anisotropy of charged particles produced in PbPb collisions at $\sqrt{s_{_\mathrm{NN}}} =$ 2.76 TeV	PRC 87 (2013) 014902	CMS-HIN-10-002 1204.1409
42	CMS Collaboration	Measurement of higher-order harmonic azimuthal anisotropy in PbPb collisions at $\sqrt{s_{_\mathrm{NN}}} =$ 2.76 TeV	PRC 89 (2014) 044906	CMS-HIN-11-005 1310.8651
43	B. Alver and G. Roland	Collision geometry fluctuations and triangular flow in heavy-ion collisions	PRC 81 (2010) 054905	1003.0194
44	S. Y. F. Liu and R. Rapp	An in-medium heavy-quark potential from the $Q\bar{Q}$ free energy	NP A 941 (2015) 179	1501.07892