Measurement of Open Heavy Flavor Production in STAR Experiment at RHIC

W. Xie for STAR Collaboration

(Purdue University, West Lafayette)

1DIS2010 Convitto della Calza, Firenze, 19th - 23rd April 2010

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 reveal critical features of the medium.

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

and forward rapidity region CGC.– Gluon shadowing, etc

0D

D0

K+

lK-

e-/-

e-/-

e+/+

Heavy quarkonia

Open heavy flavor

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Non-photonic electron

3

MRPC ToF barrelMRPC ToF barrel

BBC

PMD

FPD

FMS

EMC barrelEMC End Cap

DAQ1000DAQ1000

FGT

Completed

Ongoing

MTD

R&DHFT

TPC

FHC

HLT

The STAR Detector

The Long Standing Issue on RHIC NPE Measurement

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Results differ by a factor of two inpT spectra Total cross section p+p collisions Au+Au collisions

Investigation is underway

STAR PRL 97(2007)192301PHENIX PRL 98(2007)172301

PRL 94(2005)082301PRL 97(2006)252002

STAR d+Au PRL 94(2005)62301

STAR

STAR Solution

Significantly Increase the S/B of this analysis (2008-present)Cross check NPE measurements with early runs.

STAR preliminary

R(cm)

Beam pipe + SVT + SSD+ Dalitz

Beam pipe + Dalitz

TPC Inner Field cage

Cou

nt

Yield of conversion electrons at different radial location 5

STAR high pT NPE Measurements in 200GeV p+p collisions

Measurement done using TPC+EMC using run08 and run05 data.pT>2.5GeV/c NPE measurement with dramatically different background agree with each very well

• Combined using “Best Linear Unbiased Estimate”. χ2/ndf = 4.81/7 = 0.69 6

Comparison with the Published NPE Results

STAR and PHENIX NPE result in 200GeV p+p collisionsAre consistent within errors at pt > 2.5 GeV/c

STAR High pT NPE results are consistent with FONLL in 200GeV p+p collisions

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8/18

Disentangle Charm and Bottom Production

• Wider φ distribution for B meson because of the larger mass.

•Combined fit on data to obtain the B meson contribution to non-photonic electron.

DheB

BheBhe rr )1(

)/( BDBB eeer

B

D hep-ph/0602067

9/18

Disentangle Charm and Bottom Production

cc0D0D

eK

K

0D

eK

bb0D

KB B

0*D

• Near side: mostly from B mesons •Away side: charm (~75%), Bottom (~25%)

STAR preliminary

JPG35(2008)104117

JPG35(2008)104117

~30-60% of non-photonic electron come from B meson decay in 200GeV p+p collisions.

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B Quark contribution is Significant in p+p colliosions

Nuclear Physics A830 (2009)849c

STAR preliminary

Constrain B quark Cross Section

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Nuclear Physics A830 (2009)849c

STAR preliminary

•Obtain B quark high pT spectrum

•Constrain B quark Production Cross Section at RHIC using Model predictions.

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Future of Heavy Flavor Measurement at STARMTD (MRPC)

Summary and Perspective

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STAR NPE results and PHENIX published result are consistent within errors at pt > 2.5 GeV/c in 200GeV p+p Collisions.

STAR hight pT NPE Results are consistent with FONLL.

New measurements of D mesons and low pT NPE using TOF should provide good constraints on total charm cross section

Expecting exciting results in the coming years with upgraded detectors and luminosity.

backup

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Future of Heavy Flavor Measurement at STAR

Courtesy of T. Ullirich

MTD (MRPC)

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Analysis Method in STAR for High pT NPE

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)(

)()(photonicN

inclusiveNnpeN

Photonic Reconstruction Efficiency estimated from embedding.Small variation in ε can leads to large difference in NPE

Dominant background:

ee

ee

0

Combining run5 and run8 resultsUsing “Best Linear Unbiased Estimate” NIM A500(2003)391,

•χ2/ndf = 4.8/7 = 0.69 •Run05 and run08 are consistent with each other. 18

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