Quarkonium measurements via the di-muon decay … channel in p+p and Au+Au collisions with the STAR experiment Takahito Todoroki (BNL) for the STAR Collaboration Strangeness in Quark

Quarkonium measurements via the di-muon decay channel in p+p and Au+Au collisions

with the STAR experiment

Takahito Todoroki (BNL) for the STAR Collaboration

Strangeness in Quark Matter 2016

From June 27th to July 1st 2016 UC Berkeley

6/28/16 1 Takahito Todoroki, sQM 2016

0 1 2 3 4 5 6 7 8 9 10pt (GeV)

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primordial w/fte+Bfdregenerationtotalprimordialprimordial w/fteNuc. Abs.Nuc. Abs. w/fte

0-20%

Au-Au (200 A GeV)|y|<0.35

Probe QGP with J/ψ

6/28/16 Takahito Todoroki, sQM 2016 2

•  Various production mechanisms –  Prompt: direct production; decay of ψ(2S) and χc (40%) –  Non-prompt: B-meson decay (up to 20% at high pT)

•  Different effects in play –  Hot nuclear matter effects

•  Dissociation •  Regeneration •  Medium-induced energy loss

–  Cold nuclear matter effects

HOWEVER

Phys. Rev. C 82, 064905, (Modified)

•  Color-screening : J/ψ dissociates in the medium

T. Matsui and H. Satz PLB 178 (1986) 416

ϒ : A cleaner but rarer probe

•  Much smaller effects from co-mover absorption and regeneration → ( σcc ~ 800µb, σbb ~ 2µb )

•  Sequential melting of different ϒ states •  Low combinatorial background


•  Much lower production rates (mb >> mc) •  Feed-down contribution to ϒ(1S) •  Separation of different ϒ states via the

di-electron channel is challenging due to bremsstrahlung.

Advantage

Disadvantage Phys. Lett. B 735 (2014) 127

The Solenoid Tracker At RHIC (STAR)

Ø  TPC: precisely measure momentum and energy loss

Ø  TOF: measure time-of-flight Ø  BEMC: trigger on and identify

electrons Ø  MTD (|η|<0.5) : trigger on and

identify muons –  Installed 63% in 2013 and

100% in 2014 behind magnet

–  Precise timing measurement (σ~100 ps)

–  Dimuon trigger for quarkonia


Muon Telescope Detector

Barrel ElectroMagnetic Calorimeter

Time Projection Chamber

•  Mid-rapidity detector: |η| < 1, 0 < φ < 2π

Time-Of-Flight

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CGC+NRQCDNLO NRQCD

STAR preliminary

J/ψ cross section and xT scaling in p+p collisions

•  Inclusive J/ψ cross section measured in 0 < pT < 20 GeV/c –  CGC+NRQCD and NLO NRQCD agree with data

•  xT scaling of high-pT J/ψ observed for 500 GeV p+p collisions –  Breaking of xT scaling : affected by soft process


PRC 80, 041902(2009)

PRL 113 (2014) 192301 JHEP 05 (2015) 103

J/ψ cross section xT scaling

]2 [GeV/c-µ+µM2.6 2.8 3 3.2 3.4 3.6 3.8

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|<0.5, pψJ/

|y = 24935, S/B = 1:28.6ψJ/N

σSignificance = 21.9

]2 [GeV/c-µ+µM2.6 2.8 3 3.2 3.4 3.6 3.8

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Like-sign pairs

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Au+Au @ 200 GeV-1 ~ 14.2 nbL

> 5 GeV/cψT,J/

|<0.5, pψJ/

|y = 1129, S/B = 1:1.8ψJ/N

σSignificance = 15.2

J/ψ yield extraction

Signal extraction •  Mixed-event à combinatorial background. •  Fit background-subtracted unlike-sign with

Gaussian+pol3 •  Signal = (counting in[2.9,3.3] GeV/c2) –

(residual background)


No bremsstrahlung tail N ~ 25000 S/B ratio & Significance S/B = 1:29, ~ 22σ @ pT > 0 GeV/c S/B = 1:1.8, ~ 15σ @ pT > 5 GeV/c

pT > 0 GeV/c pT

> 5 GeV/c

Full statistics from 2014 Au+Au 200 GeV run

Invariant yield of J/ψ


•  First mid-rapidity measurement of J/ψ yield in Au+Au collisions via the di-muon channel for 0 < pT < 15 GeV/c

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=0)βTBW fit (

STAR preliminary

Invariant yield of J/ψ


•  First mid-rapidity measurement of J/ψ yield in Au+Au collisions via the di-muon channel for 0 < pT < 15 GeV/c

•  Consistent with the published di-electron results using Run10 data over the entire kinematic range.

Di-electron: STAR PLB 722 (2013) 55 STAR PRC 90, 024906 (2014)

J/ψ suppression:


RAA =σ inel

Ncoll

d 2NAA / dydpTd 2σ pp / dydpT

•  Suppression at Low-pT –  Dissociation –  Regeneration –  Cold nuclear matter effect

•  At high pT, strong suppression in 0-20% and a rising trend in 20-60% central collisions –  Dissociation –  Formation time effect; B feed down

(GeV/c)T

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, |y| < 1 (MB)-e+e→ψJ/, |y| < 1 (HT)-e+e→ψJ/

STAR Au+Au @ 200 GeV, |y| < 0.5-µ+µ→ψJ/

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J/ψ suppression:


RAA =σ inel

Ncoll

d 2NAA / dydpTd 2σ pp / dydpT

•  Consistent with di-electron channel results for the entire pT range within uncertainties in all centralities


J/ψ RAA vs pT : RHIC vs LHC

•  Less suppressed at LHC in low-pT → larger regeneration contribution due to higher charm cross-section

•  More suppressed at LHC in high-pT → larger dissociation rate due to higher temperature


(GeV/c)T

p0 2 4 6 8 10 12 14

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= 0.2 TeV, |y| < 0.5NNsSTAR: Au+Au, = 2.76 TeV, |y| < 0.8NNsALICE: Pb+Pb,

= 2.76 TeV, |y| < 2.4NNsCMS: Pb+Pb,

STAR preliminary

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> 5 GeV/cT

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uncertaintycollN

STAR preliminary

RAA vs. centrality

•  Central collisions : significant suppression is observed for pT > 0 GeV/c and pT > 5 GeV/c → interplay of different effects

•  Peripheral collisions : RAA of J/ψ for pT > 0 GeV/c is smaller than that for pT > 5 GeV/c probably due to cold nuclear matter effects


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p = 200 GeV |y| < 0.5NNsSTAR: Au+Au,

= 200 GeV |y| < 0.35NNsPHENIX: Au+Au, = 2.76 TeV |y| < 0.8NNsALICE: Pb+Pb,

Centrality dependence : RHIC vs LHC


ALICE : PLB 734 (2014) 314 PHENIX : PRL 98 (2007) 232301 pT

> 0 GeV/c

•  STAR data are consistent with PHENIX with better statistical precision for pT > 0 GeV/c

partN0 50 100 150 200 250 300 350

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> 0 GeV/c


•  pT > 0 GeV/c : more suppressed at RHIC in central collisions

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•  pT > 0 GeV/c : more suppressed at RHIC in central collisions •  High pT : less suppressed at RHIC in all centralities

CMS: JHEP 05 (2012) 063

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T = 2.76 TeV, |y| < 2.4, pNNsCMS: Pb+Pb,

STAR preliminary


> 5 GeV/c pT > 0 GeV/c

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= 0.2 TeV, |y| < 0.5NNsSTAR: Au+Au, = 2.76 TeV, |y| < 0.8NNsALICE: Pb+Pb, = 2.76 TeV, |y| < 2.4NNsCMS: Pb+Pb,

Transport Model ITransport Model II

RHICRHIC

LHCLHC

Transport Models

•  Transport models including dissociation and regeneration effects qualitatively describe pT dependence shape

•  Model I : below data at low-pT for LHC and shows different trend at high pT for RHIC


ALICE : PLB 734 (2014) 314 CMS: JHEP 05 (2012) 063

Transport model: Model I at RHIC: PLB 678 (2009) 72 Model I at LHC: PRC 89 (2014) 054911 Model II at RHIC: PRC 82 (2010) 064905 Model II at LHC: NPA 859 (2011) 114

Model I : Tsinghua Group Model II : TAMU Group

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Transport Models



> 0 GeV/c


•  pT > 0 GeV/c : both models can describe centrality dependence at RHIC, but tends to overestimate suppression at LHC

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= 200 GeV, |y| < 0.5, pNNsSTAR: Au+Au, > 6.5 GeV/c

T = 2.76 TeV, |y| < 2.4, pNNsCMS: Pb+Pb,

STAR preliminary


RHICRHIC

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RHICRHIC

LHCLHC

Transport Models


CMS: JHEP 05 (2012) 063 ALICE : PLB 734 (2014) 314 PHENIX : PRL 98 (2007) 232301 pT

> 0 GeV/c pT > 5 GeV/c

•  pT > 0 GeV/c : both models can describe centrality dependence at RHIC, but tends to overestimate suppression at LHC

•  pT > 5 GeV/c : there is tension among models and data


Does J/ψ flow?


(GeV/c)T

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maximum non-flow

initially producedccoalescence from thermalized c

initial + coalescenceinitial + coalescencehydrodynamic

Au+Au 200 GeV 0-80 % Run10+11-e+e→ψSTAR J/

STAR preliminary

•  Measure the second-order Fourier coefficient (v2) –  Primordial: little or zero v2 –  Regenerated: inherit v2 from the constituent charm quarks

STAR, PRL 111 (2013) 052301 L. Yan, P. Zhuang, and N. Xu, PRL 97 (2006) 232301 V. Greco, C.M. Ko, and R. Rapp, PLB 595 (2004) 202 X. Zhao and R. Rapp, arXiv: 0806.1239 Y. Liu, N. Xu and P. Zhuang, NPA 834 (2010) 317 U.W. Heinz and C. Shen, (private communication)

J/ψ à e+ + e-

•  For pT above 2 GeV/c, v2 is consistent with zero à contribution of regenerated J/ψ is small –  Non-flow effects

estimated using J/ψ-h correlation in pp collision can account for possible deviation of v2 from zero at high pT

Does J/ψ flow?


•  Measure the second-order Fourier coefficient (v2) –  Primordial: little or zero v2 –  Regenerated: inherit v2 from the constituent charm quarks

•  Consistent results from di-muon channel within large error bars

(GeV/c)T

p0 1 2 3 4 5 6 7 8 9 10

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|y| < 0.5, Run14-µ+µ→ψJ/ |y| < 1, Run10+11-e+e→ψJ/

Au+Au 200 GeV 0-80 % STAR preliminary

(1S)

ϒ(2S+3S)/

ϒ

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0.8p+p (world-wide)

CMS [email protected] TeV (0-100%)

) (0-80%)µµSTAR Au+Au@200 GeV (

STAR preliminary

(1S)ϒ(2S)/ϒ

(1S)ϒ(3S)/ϒ

pp AuAu @ RHIC PbPb @ LHC

ϒ(2S+3S)/ϒ(1S) ratio

•  Signs of Y(2S+3S) from the di-muon channel –  Challenging for di-electron channel due to Bremsstrahlung

•  Hint of less melting of ϒ(2S+3S) at RHIC than at LHC


World-wide PRC 88(2013) 067901 CMS : PRL 109(2012) 222301 CMS : JHEP 04 (2014) 103

NΥ(1S) ~ 157 ± 24

95% Upper Limit

Summary •  First J/ψ and ϒ measurements via di-muon channel at mid-

rapidity at RHIC •  p+p collisions at √s = 500 GeV

– Inclusive J/ψ cross section can be described by CGC+NRQCD & NLO NRQCD for 0<pT<20 GeV/c

•  Au+Au collisions at √sNN = 200 GeV ( Run 14 full statistics ) – Clear J/ψ suppression above 5 GeV/c in central collisions → Dissociation – J/ψ RAA can be qualitatively described by transport models including

dissociation and regeneration. However there is tension at high pT – Updated J/ψ v2 in di-electron channel using Run10+11 data → favors small

contribution from regeneration above 2 GeV/c – Hint of less melting of ϒ(2S+3S) at RHIC compared to that at LHC

•  Similar amount of data from Run16 on tape. Stay tuned!!


Back Up


ϒ(2S+3S)/ϒ(1S) ratio

•  Fit the like-sign and unlike-sign simultaneously: –  Mean of ϒ is fixed to PDG value, while width is determined from

simulation. –  Ratio of ϒ(2S)/ϒ(3S) is fixed to pp value, and shape of bb and Drell-

Yan background is estimated using PYTHIA


NΥ(1S) ~ 157 ± 24

Muon Telescope Detector (MTD)


•  Separate ϒ(2S+3S) from ϒ(1S)

•  Potential to separate ϒ(2S) and ϒ(3S) states as muons suffer less from bremsstrahlung

•  Relatively high efficiency for J/ψ at low pT à cover wide kinematic range

(GeV/c)T

p0 1 2 3 4 5 6 7 8 9 10

effi

cien

cyψ

J/

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> 3.4 GeVT

Electron: BEMC trigger with E

Muon: MTD trigger

STAR preliminary

Simulation

Run13 p+p 500 GeV Analysis details


•  Muon identification –  Match TPC tracks to MTD –  Require z residual below 20 cm

•  Decay channel: J/ψ à µ+ + µ- •  Data set: p+p collisions at 500 GeV taken in 2013 •  MTD dimuon trigger: two hits in MTD

•  Sampled integrated luminosity ~ 28.3 pb-1

•  Background: fitting Gaussian (signal) & pol3

Ø Signal extraction: Integral of Gaussian

]2 [GeV/cµµM2.4 2.6 2.8 3 3.2 3.4 3.6 3.8

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ents

/0.0

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0

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59± = 1335ψJ/N20.003 GeV/c±M = 3.087

20.003 GeV/c± = 0.062σ

0.04±S/B = 0.851.14± = 24.70S+BS/

fitsignalbackground

< 10 GeV/cψJ/T

0 < p| < 0.5µµ

|y

STAR Preliminary

A closer look: event multiplicity dependence


•  Collective effects in high-multiplicity pp collisions? •  Do we see similar or different behavior at RHIC?

•  Stronger-than-linear rise of open charm production vs event activity.

•  Similar behavior seen for inclusive J/ψ at both mid- and forward-rapidity.

•  Several ideas on the market: –  PYTHIA 8: c and b quarks produced

in Multi-Parton-Interaction -> underestimate yield at large multiplicity

–  Percolation model: string screening -> quadratic rise at high multiplicity

–  Hard process is associated with larger gluon radiation

arXiv:1505.00664

D meson

Event activity0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

>ψ

J/<N

ψJ/N

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>0 GeV/cT

, |y|<0.5, p-µ+µ→ψSTAR: J/>4 GeV/c

T, |y|<1, p-e+e→ψSTAR: J/

>0 GeV/cT

PYTHIA8.183 default: p>4 GeV/c

TPYTHIA8.183 default: p

STAR preliminary

>0 GeV/cT

Percolation model: p

STAR data points+15% one-sided error along both x- and y- direction

Event activity0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

>ψ

J/<N

ψJ/N

0

2

4

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12p+p collisions

>0 GeV/cT

, |y|<0.5, p-µ+µ→ψSTAR 500 GeV: J/

>4 GeV/cT

, |y|<1, p-e+e→ψSTAR 500 GeV: J/

>0 GeV/cT

, |y|<0.9, p-e+e→ψALICE 7 TeV: J/

<4 GeV/cT

ALICE 7 TeV: D meason, |y|<0.5, 2<p

STAR preliminary

STAR data points+15% one-sided error along both x- and y- direction

J/ψ yield vs event activity

•  Stronger-than-linear growth for relative J/ψ yield → Soft and hard processes are correlated

•  Different trends for low and high pT J/ψ •  PYTHIA8 and Percolation model reproduce trends in data •  Measurements at high multiplicities can help distinguish different models


ALICE : JHEP09(2015)148

Characterize event activity


Multiplicity of TOF matched tracks

|η| < 0.9

Beam-Beam Counter coincidence rate600 800 1000 1200 1400 1600 1800 2000

310×

TofM

ult

0

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40

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310

410

510

610Run11 p+p @ 500 GeV

Mean of each BBCrate sliceSTAR preliminary

•  Insensitive to pile-up effects

TofMult< TofMult >

Run14 Au+Au 200 GeV Analysis details


•  Muon identification cuts –  Energy loss measurement by TPC –  Match TPC tracks to MTD

•  Distance between MTD hits and projected TPC tracks along both z and φ directions

•  Time difference between MTD measured time and expected travel time of muons

•  Decay channel: J/ψ, ϒ à µ+ + µ-

•  Dimuon trigger: two hits in MTD •  Data set: Au+Au collisions at 200 GeV recorded in 2014

–  Integrated luminosity ~ 14.2 nb-1

–  Equivalent or more data will be taken in 2016

Comparison to di-electron


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> 5 GeV/cT

, |y| < 1, p-e+e→ψSTAR J/

uncertaintycollN

STAR preliminary

J/ψ RAA vs pT : STAR vs Transport Models


(GeV/c)T

p0 2 4 6 8 10 12 14

AA

R

0.20.40.60.8

11.21.41.61.8 0-60%STAR Au+Au @ 200 GeV

, |y| < 0.5-µ+µ→ψJ/, |y| < 1 (MB)-e+e→ψJ/, |y| < 1 (HT)-e+e→ψJ/

(GeV/c)T

p0 2 4 6 8 10 12 14

AA

R

0.20.40.60.8

11.21.41.61.8 20-40%

)et al.Transport Model I (Y.-P. Liu )et al.Transport Model II (X. Zhao

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(GeV/c)T

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J/ψ RAA vs pT : STAR vs PHENIX


(GeV/c)T

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(GeV/c)T

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Tp

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(GeV/c)T

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PHENIX PRL 98 (2007) 232301

J/ψ RAA vs pT : Mid vs Forward rapidity


(GeV/c)T

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AA

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, 1.2 < |y| < 2.2-µ+µ→ψPHENIX: J/

STAR preliminary

PHENIX : PRC 84 (2011) 054912

Compare J/ψ v2

35

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-0.15

-0.1

-0.05

0

0.05

0.1

0.15

0.2

0.25

maximum non-flow

initially producedccoalescence from thermalized c

initial + coalescenceinitial + coalescencehydrodynamic

Au+Au 200 GeV 0-80 % Run10+11-e+e→ψSTAR J/

STAR preliminary

STAR, PRL 111 (2013) 052301

•  By combining published results with Run11 analysis, the statistical error bar is reduced by a factor of √2.

•  Additional systematic uncertainty is assigned due to J/ψ yield extraction.

6/28/16 Takahito Todoroki, sQM 2016

Documents

Quarkonium measurements via the di-muon decay … channel in p+p and Au+Au collisions with the STAR experiment Takahito Todoroki (BNL) for the STAR Collaboration Strangeness in Quark