J/ ψ and Υ measurements in Mauro R. Cosentino for the STAR Collaboration Universidade de São...

J/ψ and Υ measurements in

Mauro R. Cosentinofor the STAR CollaborationUniversidade de São Paulo

1

24th Winter Workshop, South Padre, TX

Outlook

• Motivation• Experimental Setup• Data Analysis• Results• Conclusions• Perspectives

2WWND2008 – Texas, USA, Apr. 10, 2008 Mauro R. Cosentino

What Quarkonia Can Tell?

• Suppression in A+A by color screening• Sequential suppression• Hot wind dissociation• Is enough to measure quarkonia in A+A? NO!


H. Liu, K. Rajagopal and U.A. Wiedemann,PRL 98, 182301(2007) and hep-ph/0607062

H. Satz, Nucl. Phys. A (783):249-260(2007)

H. Satz, Nucl. Phys. A (783):249-260(2007)

Quarkonia Production

• Base line: p+p– QQ pairs come from gluon fusion– Color Singlet Model– NRQCD (includes Octate states)– Color Evaporation Model

• CNM Effects: d+Au– Shadowing and Anti-shadowing– Gluon saturation– Nuclear absorption


The Experiment

• 0< φ <2π; |η|<1• |B|= 0.5 T• TPC

– Tracking detector– PID

• BEMC– Main quarkonia trigger detector– PID

• CTB– Auxiliar quarkonia trigger detector


Quarkonia measurement: How did we make it?


• QQ->e+e- golden decay• Rare Probes: TRIGGER! • Exploit full STAR acceptance• Level 0: Topologic

– 6φ sectors– Search BTOW E>th0– Search in non-adjacent

sectors– At least 2 BTOW>th0

• Υ : Only 1 BTOW


• J/ψ: CTB veto to photons

• L0 HT seeds L2

• Seeds Clusters

• Tracks straight lines

• Vertex BBC / (0,0,0)

• θ12 angle given by C1-V-C2

• M = [2E1E2(1-cos θ12)]

• 2.2<MJ/ψ<5.0; 6<MΥ<15 (GeV/c2)

Trigger: Level 2, algorithm



High-pT J/ψ


p+p data sample:• 1. EMC triggered events in year 2005• ET>3.5 GeV• Integrated luminosity: 3 (pb)-1

• 2. EMC triggered events in year 2006• ET>5.4 GeV• Integrated luminosity: 11 (pb)-1 Cu+Cu data sample:• 1. EMC triggered events in year 2005• ET>3.75 GeV• Integrated luminosity: 0.9 (nb)-1

• pp-equivalent: 3 (pb)-1

p+p data sample:• 1. J/ψ triggered events in year 2006

• Integrated luminosity: 377 (nb)-1

• 2. Υ triggered events in year 2006

• Integrated luminosity: 9(pb)-1

Au+Au data sample:• 1. Υ triggered events in year 2007

• Integrated luminosity: 300(μb)-1

• pp-equivalent: 12(pb)-1

Triggered data


Quarkonia measurement: How did we make it?Electron Identification

• TPC – dE/dx

• BEMC – ptrack/Etow

• BEMC – Shower Max (High-pT J/ψ)

4<pT<5 GeV/c

dE/dx projection

J/ψ Results


EMC+TPC electrons:1, pT>4.0 GeV/c

TPC only electrons:1, pT>1.2 GeV/c

Reach higher pT (~14GeV/c)

J/ψ

trig

ger

HT

trig

ger

0<p T

<5.

5 G

eV/c

MC describes position and width

Z. Tang, QM2008

QM2008

J/ψ Results

11

• Consistent with previous measurements

• Significantly increased pT range

•Consistent with Color Evaporation calculations (R. Vogt, private communication)

WWND2008 – Texas, USA, Apr. 10, 2008 Mauro R. Cosentino

J/ψ Results

12

NRQCD pT calculation inconsistent with data(F. Cooper, M. X. Liu and G. Nayak, PRL 93:171801, 2004)

}

WWND2008 – Texas, USA, Apr. 10, 2008 Mauro R. Cosentino

J/ψ Results


<pT2>= 3,43±0,68 (GeV/c)2

<pT2>= 2,4+1,2ln(s1/2)

STAR Measurement × world data

CEM calculation,M. Bejidian et al.,hep-ph/0311048

J/ψ Results

14WWND2008 – Texas, USA, Apr. 10, 2008

• Extend the pT range to 10GeV/c

• Consistent with no suppression at high pT: RAA(pT>5 GeV/c) = 0.9±0.2

• Indicates RAA increase from low pT to high pT

• Most models expect a decrease RAA at high pT: AdS/CFT: H. Liu, K. Rajagopal and U.A. Wiedemann, PRL 98, 182301(2007) and hep-ph/0607062

Two Component Approach: X. Zhao and R. Rapp, hep-ph/07122407 Private communication

Mauro R. Cosentino

Z. Tang, QM2008

Υ Results: p+p


preliminary

preliminary

• Υ(1S+2S+3S) total yield: integrated from 7 to 11 GeV from background-subtracted mee distribution

• Peak width consistent with expected mass resolution• Significance of signal is 3σ

P. Djawotho, QM2006

Υ Results: p+p


preliminar

y

STAR 2006 sqrt(s)=200 GeV p+p ++→e+e- cross section consistent with pQCD and world data

Bee×(dσ/dy)y=0=91±28(stat.)±22(syst.) pb

P. Djawotho, QM2006

Υ Results: Au+Au


• Stronger 4 signal• First measurement of in nucleus-nucleus collisions ever• RAA in progress

D. Das, QM2008

Conclusions


• J/ψ data: – Corroborate previous measurement at same s– Extend significantly the pT range at s = 200 GeV

– High-pT: RAA increases with pT contradicting models

– Confirms that Color Singlet Model is no good for Hadroproduction

– NRQCD fails to explain pT spectrum

Conclusions


• Υ data: – pp data: measurement consistent with pQCD

calculations and world data– AuAu data: 1st measurement ever!– Strong signal

Perspectives for Quarkonia


• Υ RAA coming soon

• At least 2 papers being prepared

• Run VIII (d+Au) just finished: analysis will provide information of CNM effects on Quarkonia

• RHIC II + DAQ1000 will allow separation of 1S, 2S and 3S Υ states and enhance statistics for J/ψ

Perspectives for Quarkonia


• STAR Upgrades:

– Time-Of-Flight (i): improved electron identification

– Time-Of-Flight (ii): allows J/ψ trigger on high multiplicity events

– Heavy Flavor Tracker (i): determination of BJ/ψ contribution

– Heavy Flavor Tracker (ii): γ conversion rejection

– Muon Telescope Detector: will provide QQµ+µ- measurements with good momentum resolution

THANK YOU!

BACKUP SLIDES



Anti-shadowing@RHIC: the Υ case: large m large x

With huge mass we move away from the “sweet spot” into anti-shadowing region

• Model dependent• EKS: ~1.15 at x• Affects RAA interpretation• To understand we need in d+Au

Note:~70% from gg~29% from qg~ 1% from qq

Cannot necessarily separate initial from final state effects for at RHIC energy


Scaling of Charm Production

Chen Zhong (STAR), J. Phys. G Nucl. Part. Phys., 34:S741-S744


Consistency of STAR and PHENIX


Intrinsic kT effect on pT spectrum

kT=0 kT>0


High-pT J/ψ in Cu+Cu

0-60%


Mass and states

91 pb++

12 pb0.53 nb2.1810.3552

17 pb0.87 nb1.9110.02326

62 pb2.6 nb2.389.46030

Bee×(dσ/dy)y=0(dσ/dy)y=0Bee [%]Mass [GeV/c2]State


Mass Spectra (1st approach) First Rough Look: Using identical cuts as in p+p analysis. Pros : allows “apples-to-apples” comparison with p+p Cons : not optimal for Au+Au

– larger background, different trigger thresholds

J/ ψ and Υ measurements in Mauro R. Cosentino for the STAR Collaboration Universidade de São...

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