Charm Production from STAR Experiment

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Outline: STAR Present Measurements

J/ψ Measurements in p+p, d+Au and Au+Au collisions

Open Charm Measurement D meson direct reconstruction. Non-photonic electron

Summary of the Present Results.

Future STAR Heavy Flavor Program.

05/15/2012 Berkeley School 2012

W. Xie for STAR Collaboration(PURDUE University, West Lafayette)

Motivation for Studying Heavy Quarks

• Heavy quark mass are external parameter to QCD.

• Sensitive to initial gluon density and gluon distribution.

• Interact with the medium differently from light quarks.

• Suppression or enhancement pattern of heavy quarkonium production reveals critical features of the medium.

• Cold Nuclear effect (CNM):– Different scaling properties in central

and forward rapidity region CGC.– Gluon shadowing, etc

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0D

D0

K+

lK-

e-/-

e-/-

e+/+

Heavy quarkonia

Open heavy flavor

Non-photonic electron

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Quarkonia Suppression: “Smoking Gun” for QGP

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Color Screening

cc

cc

J/y

D+

d

• Low temperature

• Vacuum

• High temperature

• High density

(screening effect take place)

Sequential meltinga QGP thermometerH. Satz, NPA 783 (2007) 249c.

d

D-

The life of Charmonia in the Medium can be Complicated

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• Observed J/y is a mixture of direct production+feeddown (R. Vogt: Phys. Rep. 310,

197 (1999)). – All J/y ~ 0.6J/y(Direct) + ~0.3 cc + ~0.1y’

– B meson feed down. • Important to disentangle different component

• Suppression and enhancement in the “cold” nuclear medium– Nuclear Absorption, Gluon shadowing, initial state energy loss, Cronin

effect and gluon saturation (CGC)

• Hot/dense medium effect – J/ , y dissociation, i.e. suppression– Recombination from uncorrelated charm pairs D+

cc

c

J/y

Important to Study Open Charm Production

• A good reference to J/Ψ suppression or enhancement.– Same or similar initial state effect.

• CGC, Shadowing, initial state energy loss, etc.

– Large cross section (compared to J/ψ). • Accurate reference measurements.

• One of the important probes complimentary to J/ψ measurements – Interactions between heavy quark and medium are quite different

from the ones for light quarks• gluon radiation, collisional energy loss, collisional disassociation, etc

– allow further understanding of the medium properties.

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The STAR Detector

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MRPC ToF barrel

BBC

PMD

FPD

FMS

EMC barrelEMC End Cap

DAQ1000 Completed

TPC

FTPC

FGT Ongoing R&D

FHC

HLTHFT

MTD

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The (major) STAR Detector for Charm Measurements

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Time Projection Chamber: • , full azimuth • Tracking.• PID through dE/dx

Barrel Electromagnetic Calorimeter• , full azimuth • BTOW:

• Tower: • p/E for electron ID • Fast online trigger

• BSMD:• Double layer High spatial

resolution MWPC. • •

• e/h separation.

Time of Flight: • , full azimuth .• PID through TOF • Timing resolution: ~85

ps.

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Particle Identification from TOF+dE/dx

|1/-1|<0.03

Extend hadron PID to intermediate pT

• Important for open charm measurements.

TOF/TPC allows electron PID down to very low momentum

Important for charmonia measurements.

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Electron Identification from TPC + BEMC

High pT electron PID: TPC+BTOW:

Associate TPC tracks with BTOW clusters.

cut p/E ~1.0 Cut on number of BSMD strips per

cluster: Associate TPC tracks with BSMD

clusters. Higher for electron.

2.5 < pT<3.0 GeV/c 8.0< pT<10 GeV/c

Charm Signals Observed in STAR

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STAR can measure charm • of all different kind

• (J/ψ, D0, D*, electron …)• in broad pT range.• at both mid and forward rapidity• in all collision species.

STAR Preliminary

forward J/ψ

J/ψ from χc enriched

STAR Preliminary

D0 Au+Au 200 GeV

D* p+p 200 GeV

D* p+p 500 GeV

STAR Charmonia Measurements

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e-/-

e+/+

J/y Production in 200GeV p+p Collisions

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Color singlet model (NNLO*CS): P. Artoisenet et al., PRL. 101, 152001

(2008), and J.P. Lansberg private communication.

Include no feeddown from higher mass state.

LO CS+ color octet (CO): G. C. Nayak et al., PRD 68, 034003

(2003), and private communication. Include no feeddown from higher

mass state. Agree with the data

Color Evaporation Model: M. Bedjidian et al., hep-ph/0311048;

R. Vogt private communication Include feeddown from Xc and ψ’ Agree with the data

STAR: Phys. Rev. C80, 041902(R) (2009)

Tsallis Blast-Wave model: ZBT et al., arXiv:1101.1912; JPG 37, 085104 (2010)

Zebo Tang, JPG 38, 124107 (2011)

J/y-hadron Azimuthal Correlation in 200GeV p+p Collisions

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BJ/ : y 10-20% of total J/ y (pT > 4GeV/c) at RHIC The ratio has no significant dependence on collisions energy. Constrain J/ y Production mechanisms in p+p:

J/y+c, J/y+D or J/y+e

S. Brodsky, J.-P. Lansberg, arXiv:0908.0754

Zebo Tang, JPG 38, 124107 (2011)

Away side associated hadron pT spectra

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Consistent with hadron-hadron correlation away-side seems to come from gluon/light quark fragmentation

STAR, PRL95, 152301 (2005) Zebo Tang, JPG 38, 124107 (2011)

E. Braaten Phys. Rev. Lett. 71, 1673 (1993).

J/y Polarization

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On top of spectra, J/psi polarization provide additional discrimination power against models.

Results are consistent with the COM and NLO+ CSM prediction. • Much more statistics are needed.

pT (J/psi: GeV/c)

See Barbara Trzeciak’s talk for details.

Helicity frame

J/ y Suppression/Enhancement in 200GeV d+A and A+A and Collisions

d+Au Collisions:• Nice consistency with PHENIX

Cu+Cu Collisions: RAA(p>5 GeV/c) = 1.4± 0.4±0.2

RAA seems larger at higher pT.

Model favored by data: 2-component: nucl-th/0806.1239 Incl. color screening, hadron phase

dissociation, coalescence, B feeddown. Model unfavored by the data:

AdS/CFT+Hydro: JPG35,104137(2008)

Comparison with open charm: Charm quark & Heavy resonance :

NPA784, 426(2007); PLB649, 139 (2007), and private communication

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Phys.Rev.C80:041902,2009

J/y spectra in 200GeV Au+Au collisions

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Broad pT coverage from 0 to 10 GeV/c

J/y spectra significantly softer than the prediction from light hadrons Much smaller

radial flow? Regeneration at

low pT?

Tsallis Blast-Wave model: ZBT et al., arXiv:1101.1912; JPG 37, 085104 (2010)

Phys. Rev. Lett. 98, 232301 (2007)

Zebo Tang, JPG 38, 124107 (2011)

RAA vs. pT

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Increase from low pT to high pT

Consistent with unity at high pT in (semi-) peripheral collisionsMore suppression in central than in peripheral even at high pT

STAR CuCu: PRC80, 014922(R)PHENIX: PRL98, 232301

Yunpeng Liu, Zhen Qu, Nu Xu and Pengfei Zhuang, PLB 678:72 (2009) and private comminication Xingbo Zhao and Ralf Rapp, PRC 82,064905(2010) and private communication

Zebo Tang, JPG 38, 124107 (2011)Zebo Tang, JPG 38, 124107 (2011)

RAA vs. Npart

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Systematically higher at high pT in all centralities

Suppression in central collisions at high pT

System size dependence due to J/y formation time effect?

Escaping at high pT (without jet quenching effect)?

Yunpeng Liu, Zhen Qu, Nu Xu and Pengfei Zhuang, PLB 678:72 (2009) and private comminication Xingbo Zhao and Ralf Rapp, PRC 82,064905(2010) and private communication

STAR Pion: Yichun Xu at QM2009

Zebo Tang, JPG 38, 124107 (2011)

J/y flow: more discriminating power

If charm quark flows. J/Psi from recombination also flow.

If the observation is consistent with zero flow, it could mean

J/psi does not flow OR

Flow is small due to mass ordering effect OR

Recombination is not a dominant process.

Yan,Zhuang,XuPRL 97, 232301 (2006)

J/

PHENIX NPE v2: arXiv:1005.1627v2

x

yz

STAR Preliminary

J/y elliptic flow v2

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V2 (hadron) > V2 (Φ) > v2 (J/ψ) ~0. Is it completely due to mass ordering effect?

Zebo Tang, JPG 38, 124107 (2011)

STAR Preliminary

Zebo Tang, JPG 38, 124107 (2011)

J/y elliptic flow v2

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[1] V. Greco, C.M. Ko, R. Rapp, PLB 595, 202.[2] L. Ravagli, R. Rapp, PLB 655, 126.[3] L. Yan, P. Zhuang, N. Xu, PRL 97, 232301.[4] X. Zhao, R. Rapp, 24th WWND, 2008.[5] Y. Liu, N. Xu, P. Zhuang, Nucl. Phy. A, 834, 317.[6] U. Heinz, C. Shen, priviate communication.

disfavors the case that J/Ψ with pT > 2GeV/c is produced dominantly by coalescence from thermalized charm and anti-charm quarks.

Models P-value

Initially produced 1.8/3 6.2e-1

Coalescence at freezeout 22.6/3 4.9e-5

Coalescence In transport 13.9/3 3.0e-3

Coalescence In transport 4.8/3 1.8e-1

Coalescence +initial mix 2.9/3 4.0e-1

Coalescence +initial mix 1.8/4 7.7e-1

Hydro T=120 w/viscosity 16.5/3 9.2e-4

Hydro T=165w/ viscosity 14.9/3 1.9e-03

Hydro T=120 w/o viscosity 191.6/3 2.7e-41

Hydro T=165w/o viscosity 237.3/3 0.0

Courtesy of Hao Qiu

STAR Open Charm Measurements

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D0

K+

+

l

K-

e-/-D0

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D0 signal in p+p 200 GeV

B.R. = 3.89%

p+p minimum bias 105 M

4-s signal observed.

Different methods reproduce combinatorial background.

Consistent results from two background methods.

𝐷0 (𝐷0 )→𝐾∓𝜋±

arXiv:1204.4244.

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D* signal in p+p 200 GeV

• Minimum bias 105M events in p+p 200 GeV collisions.

• Two methods to reconstruct combinatorial background: wrong sign and side band.

• 8-s signal observed.

Background recomstruction:

Wrong sign: D0 and -, and +

Side band: 1.72< M(K) < 1.80 or 1.92 < M(K) < 2.0 GeV/c2

𝑫∗± →𝑫𝟎 (𝑫𝟎 )+𝝅± →𝑲∓𝝅±+𝝅±

arXiv:1204.4244.

The charm cross section at mid-rapidity is:

The charm total cross section is extracted as:

b

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D0 and D* pT spectra in p+p 200 GeV

[1] C. Amsler et al. (PDG), PLB 667 (2008) 1. [2] FONLL: M. Cacciari, PRL 95 (2005) 122001.

arXiv:1204.4244.

D0 scaled by Ncc / ND0 = 1 / 0.56[1]

D* scaled by Ncc / ND* = 1 / 0.22[1]

Consistent with FONLL[2] upper limit.

Xsec = dN/dy|ccy=0 × F × spp

F = 4.7 ± 0.7 scale to full rapidity.

spp(NSD) = 30 mb

|

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D0 signal in Au+Au 200 GeV

Year 2010 minimum bias 0-80% 280M Au+Au 200 GeV events.

8-s signal observed. Mass = 1863 ± 2 MeV (PDG value is 1864.5 ± 0.4 MeV) Width = 12 ± 2 MeV

YiFei Zhang, JPG 38, 124142 (2011)

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Charm cross section vs Nbin

Charm cross section follows number of binary collisions scaling =>Charm quarks are mostly produced via initial hard scatterings.

All of the measurements are consistent.

Year 2003 d+Au : D0 + e

Year 2009 p+p : D0 + D*

Year 2010 Au+Au: D0

Assuming ND0 / Ncc = 0.56 does not change.

Charm cross section in Au+Au 200 GeV:

Mid-rapidity:

186 ± 22 (stat.) ± 30 (sys.) ± 18 (norm.) mb

Total cross section:

876 ± 103 (stat.) ± 211 (sys.) mb[1] STAR d+Au: J. Adams, et al., PRL 94 (2005) 62301[2] FONLL: M. Cacciari, PRL 95 (2005) 122001.[3] NLO:  R. Vogt, Eur.Phys.J.ST 155 (2008) 213   [4] PHENIX e: A. Adare, et al., PRL 97 (2006) 252002.

YiFei Zhang, JPG 38, 124142 (2011)arXiv:1204.4244.

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Charm cross section vs √sNN

Compared with other experiments, provide constraint for theories.

YiFei Zhang, JPG 38, 124142 (2011)

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D0 RAA compared with Alice result

YiFei Zhang, JPG 38, 124142 (2011)

ALICE results shows D meson is suppressed at high pT.

More luminosity and detector upgrade are needed from STAR to reach high pT.

At present, NPE is the key to study high pT charm and bottom production.

A. Rossi, JPG 38, 124139 (2011)

Non-photonic Electron Measurements

DGLV: Djordjevic, PLB632, 81 (2006)

BDMPS:Armesto, et al.,PLB637, 362 (2006)

T-Matrix:Van Hees et al., PRL100,192301(2008).

Coll. Dissoc. R. Sharma et al., PRC 80, 054902(2009).

Ads/CFT: W. Horowitz Ph.D thesis.

RL.+ Coll. J. Aichelin et al., SQM11

32 Models with different or similar mechanisms can or can not

describe the data Which one is right and what are missing?

Charm dominate at pT<5 GeV/c

STAR: PRL 106, 159902 (2011)PHENIX: arXiv:1005.1627v2

Summary for the Present STAR Charmonia Measurements

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In p+p collisions J/y spectra measurements are extended to high pT

J/y polarization is consistent with COM and NLO+ CSM prediction Large S/B ratio allows correlation study

o B has sizeable (not dominant) contribution at high pT

o High-pT J/y away side hadron production consistent with gluon / light quark fragmentation

In heavy-ion collisions Observation of no suppression for J/y at high pT (5-10 GeV/c) at STAR in

200GeV Cu+Cu and peripheral Au+Au collisions, and suppression at high pT in central Au+Au collisions J/y suppression at high pT less than that at low pT J/y v2 measurements are consistent with zero, disfavor production at pT > 2

GeV/c dominated by coalescence from thermalized charm quarks

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D0 and D* are measured in p+p 200 GeV up to pT = 6 GeV/c.

D0 is measured in Au+Au 200 GeV up to pT = 5 GeV/c.

The charm cross section per nucleon-nucleon 200 GeV collision at mid-rapidity

Charm cross sections at mid-rapidity follow number of binary collisions scaling, which indicates charm quarks are mostly produced via initial hard scatterings.

D0 nuclear modification factor RAA is measured. No obvious suppression observed at pT < 3 GeV/c.

Large suppression of high-pT non-photonic electron production is observed.

A real challenge to our understanding of energy loss mechanism.

Summary for the Present STAR Open Charm Measurements

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|

STAR Preliminary

STAR Preliminary

STAR Preliminary

The sQGP is Complicated

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We thus need more probes, other than charms, to have a more complete picture of its properties, e.g. Upslions.

Cleaner Probes compared to J/psi: recombination can be neglected at RHIC Grandchamp, Sun, Van Hess, Rapp, PRC 73, 064906 (2006)

Almost no feeddown for Upsilon

Final state co-mover absorption is small.

Anthony Kesich, WWnd2012

A Quick Glimpse of STAR Upsilon Measurements

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0-10% CentralitySTAR Preliminary

S. Digal, P. Petreczky, and H. Satz, Phys Rev. D 64,094015 (2001)Anthony Kesich, WWnd2012

Consistent with the melting of all excited states.

Questions to be addressed by STAR in the next Decade.

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(http://www.bnl.gov/npp/docs/STAR_Decadal_Plan_Final%5B1%5D.pdf)

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How to address these questions

At both

low pT

and

high pT

Heavy Flavor Tracker (HFT)

TPC Volume

Magnet

Return Iron

Solenoid

Outer Field Cage

Inner Field Cage

EASTWEST

FGT

SSDISTPXL

HFT Detector Radius(cm)

Hit Resolution R/ - Z (m - m)

Radiation length

SSD 22 30 / 860 1% X0

IST 14 170 / 1800 1.32 %X0

PIXEL8 8 / 8 ~0.37 %X0

2.5 8 / 8 ~0.37% X0

SSD• existing single layer detector, double side strips (electronic upgrade)

IST • one layer of silicon strips along beam direction, guiding tracks from the

SSD through PIXEL detector. - proven strip technology

Prototype for run2013 and complete for run2014

PIXEL • double layers• 18.4x18.4 m pixel pitch • 2 cm x 20 cm each ladder • 10 ladders, delivering ultimate

pointing resolution. • new active pixel technology

Muon Telescope Detector (MTD)

Use the magnet steel as absorber and TPC for tracking.

• covers the whole iron bars and leave the gaps in-between uncovered.

• Acceptance: ||<0.5 and 45% in azimuth

• 118 modules, 1416 readout strips, 2832 readout channels

• Long-MRPC detector technology,

• HPTDC electronics (same as STAR-TOF)

~43% for run2013 and Complete for run2014

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RHIC CAD Projections

http://www.bnl.gov/npp/docs/pac0611/Fischer_Machine%20performance%20and%20projections.pdf

Production and flow of Directly Reconstructed Charm

RCP=a*N10%/N(60-80)%

Assuming D0 Rcp distribution as charged hadron

Assuming D0 v2 distribution from quark coalescence.

500M minbias events. STAR duty factor: 50% (underestimated).

Efficiency of |Vz|<5cm: 20%.

50 kHz collision rate at RHIC-II and 500 Hz bandwidth for minbias trigger

Access Bottom Production via ElectronsCurves:  H. van Hees et al. Eur. Phys. J. C 61 (2009) 799

(Be) spectra obtained via the subtraction of charm decay electrons from inclusive NPEs: no model dependence

500M minbias events for low pT

500 µb-1 sampled Luminosity for high pT corresponding to 5 nb-1 RHIC delivered luminosity

BJ/ + X with HFT+TPC+MTD

Prompt J/

J/ from B

Cleanest sample of B meson decays. BJ/ψee suffer from low trigger efficiency. A much better measurements: BJ/ψ->µµ

• not limited by triggers• Less multiple scattering, leading to higher B meson ID efficiency.

One RHIC-II run, ~3000 counts in Au+Au and 200 counts in p+p

Upsilon Mass Resolution with MTD

Di-electrons with inner trackerDi-electrons without inner tracker. Di-muons from any case

Before run013, will provide us with the initial clue on Upsilon production.

After run013, will tell us in detail how Upsilon is produced.

o With detector upgrade and much more luminosity

Projections on J/ψ Measurements

J/µµ

J/µµ

(delivered)

(delivered)

Zebo Tang, JPG 38, 124107 (2011)

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Projections on Upsilon Measurements

𝚼→𝝁𝝁

Good accuracy in inclusive in each centrality.

Good accuracy in inclusive in each centrality. Capable of

separating 1S/(2S+3S) states.

𝚼→𝒆𝒆

Charm Baryons

cpK Lowest mass charm baryons c = 60 m

c/D enhancement? 0.11 (pp PYTHIA) 0.4-0.9 (Di-quark correlation in QGP)

S.H. Lee etc. PRL 100 (2008) 222301 Total charm yield in heavy ion collisions

QGP Thermal Radiation with dileptons

QGP thermal radiations

dominated by the correlated pair from charm-decay electrons. Addressed by• e correlation with Muon Telescope Detector at STAR from ccbar:

• S/B=2 (Meu>3 GeV/c2 and pT(e)<2 GeV/c)• S/B=8 with electron pairing and tof association

• Accurate D meson measurements

L. Ruan et al., JPG 36 (2009) 095001 J. Zhao, JPG 38, 124134 (2011)

Summary

Precision measurements of J/ψ will continue to be one of the most important tasks in the field

Precision measurements of other heavy flavor probes are a necessary condition for a complete understanding of the interaction between heavy quarks and the Medium.

STAR HFT and MTD upgrades together with existing subsystems and RHIC II luminosities will provide us with the unprecedented opportunity to accomplish these tasks.

The accomplishment of these tasks will allow us to better understand the medium properties, which may leads to new discoveries.

BACKUP SLIDES

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Charm Quark Hadronization

Lee, et. al, PRL 100 (2008) 222301

Direct (hard) fragmentation in elementary collisions. However, in heavy ion collisions …

V. Greco et al., PLB 595(2004)202

Coalescence approach

Charm baryon enhancement ? - coalescence of c and di-quark

Reconstruction of Displaced Vertices

D0 decays

particle c (m) Mass (GeV)

D0 123 1.865

D+ 312 1.869

Ds+ 150 1.968

c+ 60 2.286

B0 459 5.279

B+ 491 5.279

Direct topological reconstruction of charm and bottom decays

Efficiency / SignificanceNeed New plots

D0 spectrum covering 0.5 - ~10 GeV/c in one RHIC run

STAR HFT vs. PHENIX VTX

Upsilon Statistics

Collision system

Delivered lumi.

12 weeks

Sampled lumi.

12 weeks (70%)

Υ counts Min. lumi.precision

on Υ (3s) (10%)

Min. lumi.precision

on Υ (2s+3s)

(10%)

200 GeV p+p

200 pb-1 140 pb-1 390 420 pb-1 140 pb-1

500 GeV p+p

1200 pb-1 840 pb-1 6970 140 pb-1 50 pb-1

200 GeV Au+Au

22 nb-1 16 nb-1 1770 10 nb-1 3.8 nb-1

Delivered luminosity: 2013 projected;Sampled luminosity: from STAR operation performance

Some pixel features and specificationsPointing resolution (12 19GeV/pc) m

Layers Layer 1 at 2.5 cm radiusLayer 2 at 8 cm radius

Pixel size 18.4 m X 18.4 m

Hit resolution 8 m rms

Position stability 6 m (20 m envelope)

Radiation thickness per layer

X/X0 = 0.37%

Number of pixels 436 M

Integration time (affects pileup) 0.2 ms

Radiation requirement 20-90 kRad

Rapid detector replacement

< 8 Hours

criticalanddifficult

more than a factor of 3 better than other vertex detectors (ATLAS, ALICE and PHENIX)

MTD (Run 10 Prototype) Performance

Total resolution: 109 psMTD intrinsic resolution: 96 ps

satisfying the design goal

System spatial resolution: 2.5 cm, dominated by multiple scatteringexpected from simulation

σ: 109 ps

σ: 2.5 cm

pure muonspT: ~6 GeV/c

position difference (cm)

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Ramona Vogt

Workshop on Heavy Quark Production in Heavy-ion Collisions, Jan. 6, 2011, Purdue University

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