CMS-PAS-HIN-19-007

CMS-PAS-HIN-19-007
Fragmentation of jets containing a ${\mathrm{J}/\psi}$ meson in PbPb and pp collisions at 5 TeV
CMS Collaboration
June 2020

Abstract: Jets containing a ${\mathrm{J}/\psi}$ meson are studied in PbPb collisions at a center of mass energy of ${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} =$ 5.02 TeV, using the CMS detector at the LHC. Jets are selected to be in the transverse momentum range of 30 $< {p_{\mathrm{T}}} <$ 40 GeV. The yield of ${\mathrm{J}/\psi}$ in these jets is evaluated as function of the jet fragmentation function variable $z$ , the ratio of the ${\mathrm{J}/\psi}$ ${p_{\mathrm{T}}}$ to the jet ${p_{\mathrm{T}}}$ . The nuclear modification factor is then derived by comparing the yield in PbPb to the corresponding expectation from pp data at the same collision energy. The suppression of the ${\mathrm{J}/\psi}$ yield shows a dependence on $z$ , indicating that the interaction of the ${\mathrm{J}/\psi}$ with the quark-gluon plasma formed in heavy-ion collisions depends on the fragmentation pattern of the jet that gives rise to the ${\mathrm{J}/\psi}$ meson.
Links: CDS record (PDF) ; CADI line (restricted) ; These preliminary results are superseded in this paper, Submitted to PLB. The superseded preliminary plots can be found here.

Figures	Summary	References	CMS Publications

Figures
png pdf	Figure 1: Projections of a two-dimensional fit used to extract the prompt ${\mathrm{J}/\psi}$ yield in PbPb collisions. Left: The invariant mass distribution. Right: The $l_{{\mathrm{J}/\psi}}$ distribution.
png pdf	Figure 1-a: Projections of a two-dimensional fit used to extract the prompt ${\mathrm{J}/\psi}$ yield in PbPb collisions. Left: The invariant mass distribution. Right: The $l_{{\mathrm{J}/\psi}}$ distribution.
png pdf	Figure 1-b: Projections of a two-dimensional fit used to extract the prompt ${\mathrm{J}/\psi}$ yield in PbPb collisions. Left: The invariant mass distribution. Right: The $l_{{\mathrm{J}/\psi}}$ distribution.
png pdf	Figure 2: Detector response matrices for jets containing a prompt ${\mathrm{J}/\psi}$ meson, showing the bin migration probability as a function of jet ${p_{\mathrm{T}}}$ and $z$ . The response for pp collisions (left) is evaluated using PYTHIA 8. The response for PbPb collisions (right) is evaluated using PYTHIA 8 embedded into HYDJET.
png pdf	Figure 2-a: Detector response matrices for jets containing a prompt ${\mathrm{J}/\psi}$ meson, showing the bin migration probability as a function of jet ${p_{\mathrm{T}}}$ and $z$ . The response for pp collisions (left) is evaluated using PYTHIA 8. The response for PbPb collisions (right) is evaluated using PYTHIA 8 embedded into HYDJET.
png pdf	Figure 2-b: Detector response matrices for jets containing a prompt ${\mathrm{J}/\psi}$ meson, showing the bin migration probability as a function of jet ${p_{\mathrm{T}}}$ and $z$ . The response for pp collisions (left) is evaluated using PYTHIA 8. The response for PbPb collisions (right) is evaluated using PYTHIA 8 embedded into HYDJET.
png pdf	Figure 3: The main sources of systematic uncertainty, plotted as a function of $z$ in pp (left) and PbPb (right) collisions.
png pdf	Figure 3-a: The main sources of systematic uncertainty, plotted as a function of $z$ in pp (left) and PbPb (right) collisions.
png pdf	Figure 3-b: The main sources of systematic uncertainty, plotted as a function of $z$ in pp (left) and PbPb (right) collisions.
png pdf	Figure 4: Normalized $z$ distribution in pp collisions, compared to prompt and nonprompt PYTHIA 8 simulation, at generator level. The shaded boxes represent systematic uncertainties.
png pdf	Figure 5: Left: ${\mathrm{J}/\psi}$ yields as a function of $z$ in pp and PbPb collisions. Right: The nuclear modification factor $R_{\rm AA}$ as a function of $z$ . Bars indicate statistical uncertainties, while systematic uncertainties are depicted as boxes. The box around unity shows the normalization uncertainties.
png pdf	Figure 5-a: Left: ${\mathrm{J}/\psi}$ yields as a function of $z$ in pp and PbPb collisions. Right: The nuclear modification factor $R_{\rm AA}$ as a function of $z$ . Bars indicate statistical uncertainties, while systematic uncertainties are depicted as boxes. The box around unity shows the normalization uncertainties.
png pdf	Figure 5-b: Left: ${\mathrm{J}/\psi}$ yields as a function of $z$ in pp and PbPb collisions. Right: The nuclear modification factor $R_{\rm AA}$ as a function of $z$ . Bars indicate statistical uncertainties, while systematic uncertainties are depicted as boxes. The box around unity shows the normalization uncertainties.
png pdf	Figure 6: The nuclear modification factor $R_{\rm AA}$ for two centrality selections of PbPb collisions as a function of $z$ . Due to limited statistical precision, the lowest z bin is excluded. Bars indicate statistical uncertainties, while systematic uncertainties are depicted as boxes. The boxes around unity show the normalization uncertainties.

Summary

Jets containing a

${\mathrm{J}/\psi}$ meson were studied in pp and PbPb collisions at

${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} =$ 5.02 TeV, for jets of 30

$< {p_{\mathrm{T}}} <$ 40 GeV and

$|\eta| <$ 2. We compared the distribution of the fragmentation variable

$z$ , the ratio of the

${\mathrm{J}/\psi}$

${p_{\mathrm{T}}}$ to that of the jet, between the two systems. The resulting nuclear modification factor shows a rising trend as a function of

$z$ . The suppression at low

$z$ is found to be larger in the 20% most central events, compared to the rest. The results show explicitly that the

${\mathrm{J}/\psi}$ produced with a large degree of surrounding jet activity are more highly suppressed than those produced in isolation.

References
1	T. Matsui and H. Satz	${\mathrm{J}/\psi}$ suppression by quark-gluon plasma formation	PLB 178 (1986) 416
2	P. Braun-Munzinger and J. Stachel	(Non) thermal aspects of charmonium production and a new look at ${\mathrm{J}/\psi}$ suppression	PLB 490 (2000) 196	nucl-th/0007059
3	PHENIX Collaboration	${\mathrm{J}/\psi}$ production versus centrality, transverse momentum, and rapidity in AuAu collisions at ${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} =$ 200 GeV	PRL 98 (2007) 232301	nucl-ex/0611020
4	PHENIX Collaboration	${\mathrm{J}/\psi}$ suppression at forward rapidity in AuAu collisions at ${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} =$ 200 GeV	PRC 84 (2011) 054912	1103.6269
5	ALICE Collaboration	${\mathrm{J}/\psi}$ suppression at forward rapidity in PbPb collisions at ${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} =$ 2.76 TeV	PRL 109 (2012) 072301	1202.1383
6	NA50 Collaboration	Evidence for deconfinement of quarks and gluons from the ${\mathrm{J}/\psi}$ suppression pattern measured in Pb + Pb collisions at the CERN SPS	PLB 477 (2000) 28--36
7	LHCb Collaboration	Study of ${\mathrm{J}/\psi}$ Production in Jets	PRL 118 (2017) 192001	1701.05116
8	R. Bain et al.	NRQCD Confronts LHCb Data on Quarkonium Production within Jets	PRL 119 (2017) 032002	1702.05525
9	F. Arleo	Quenching of hadron spectra in heavy ion collisions at the LHC	PRL 119 (2017) 062302	1703.10852
10	CMS Collaboration	Measurement of prompt and nonprompt charmonium suppression in PbPb collisions at 5.02 TeV	EPJC 78 (2018) 509	CMS-HIN-16-025 1712.08959
11	ATLAS Collaboration	Prompt and non-prompt ${\mathrm{J}/\psi}$ and $\psi (2\mathrm {S})$ suppression at high transverse momentum in 5.02 TeV Pb+Pb collisions with the ATLAS experiment	EPJC 78 (2018) 762	1805.04077
12	CMS Collaboration	Charged-particle nuclear modification factors in PbPb and pPb collisions at $\sqrt{s_{\mathrm{N}\;\mathrm{N}}}=$ 5.02 TeV	JHEP 04 (2017) 039	CMS-HIN-15-015 1611.01664
13	CMS Collaboration	Suppression and azimuthal anisotropy of prompt and nonprompt ${\mathrm{J}}/\psi$ production in PbPb collisions at $\sqrt{{s_{_{\text {NN}}}}} =$ 2.76 TeV	EPJC 77 (2017) 252	CMS-HIN-14-005 1610.00613
14	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
15	CMS Collaboration	Particle-flow reconstruction and global event description with the cms detector	JINST 12 (2017) P10003	CMS-PRF-14-001 1706.04965
16	CMS Collaboration	Performance of the CMS muon detector and muon reconstruction with proton-proton collisions at $\sqrt{s} =$ 13 TeV	JINST 13 (2018) P06015	CMS-MUO-16-001 1804.04528
17	CMS Collaboration	The CMS experiment at the CERN LHC	JINST 3 (2008) S08004	CMS-00-001
18	CMS Collaboration	The CMS trigger system	JINST 12 (2017) P01020	CMS-TRG-12-001 1609.02366
19	T. Sjostrand et al.	An Introduction to PYTHIA 8.2	CPC 191 (2015) 159	1410.3012
20	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
21	P. Nason et al.	Bottom production	in Workshop on Standard Model Physics (and more) at the LHC (First Plenary Meeting)	hep-ph/0003142
22	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
23	GEANT Collaboration	GEANT4 --- A simulation toolkit	NIMA 506 (2003) 250
24	Particle Data Group Collaboration	Review of Particle Physics	PRD 98 (2018) 030001
25	M. Pivk and F. R. Le Diberder	$_{s}$ Plot A statistical tool to unfold data distributions	NIMA555 (2005) 356	physics/0402083
26	M. Cacciari, G. P. Salam, and G. Soyez	The anti- $k_t$ jet clustering algorithm	JHEP 04 (2008) 063	0802.1189
27	M. Cacciari, G. P. Salam, and G. Soyez	FastJet user manual	EPJC 72 (2012) 1896	1111.6097
28	CMS Collaboration	Jet energy scale and resolution in the CMS experiment in pp collisions at 8 TeV	JINST 12 (2017) P02014	CMS-JME-13-004 1607.03663
29	P. Berta, M. Spousta, D. W. Miller, and R. Leitner	Particle-level pileup subtraction for jets and jet shapes	JHEP 06 (2014) 092	1403.3108
30	G. D'Agostini	A Multidimensional unfolding method based on Bayes' theorem	Nucl.\ Instrum.\ Meth.\ A 362 (1995) 487
31	T. Adye	Unfolding algorithms and tests using RooUnfold	Presented at PHYSTAT 2011, CERN, Geneva, Switzerland, January 2011
32	CMS Collaboration	Performance of CMS muon reconstruction in $pp$ collision events at $\sqrt{s} =$ 7 TeV	JINST 7 (2012) P10002	CMS-MUO-10-004 1206.4071
33	C. Loizides, J. Kamin, and D. d'Enterria	Improved Monte Carlo Glauber predictions at present and future nuclear colliders	PRC 97 (2018) 054910	1710.07098
34	P. Caucal, E. Iancu, A. Mueller, and G. Soyez	Vacuum-like jet fragmentation in a dense QCD medium	PRL 120 (2018) 232001	1801.09703