STAR Open Heavy Flavor Measurements
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Transcript of STAR Open Heavy Flavor Measurements
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STAR Open Heavy Flavor Measurements
Gang Wang (UCLA)
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Motivation
D0 / Ds / D*
Non-photonic electron
Summary
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Why heavy quarks?X. Zhu, et al, Phys. Lett. B647, 366(2007).
- Higgs mass: electro-weak symmetry breaking (current quark mass).
- QCD mass: Chiral symmetry breaking (constituent quark mass).
Strong interactions do not affect heavy-quark mass.
Initial fusion dominates heavy flavor production.
Study properties of the hot and dense medium at the early stage of heavy-ion collisions.
Light flavor thermalization.
M. Gyulassy & Z. Lin, PRC 51 (1995) 2177
Charm quark
The STAR detector and Particle IDLarge acceptance|| < 1, 0 < < 2
p
TPC dE/dx, momentum
TOF 1/ difference
Run9 ~ 72% of full TOFRun10: 100%
significantly improved PID for final state hadrons, especially for kaons
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Previous D0 measurements
% 83.3~)( 00 KDD
STAR Preliminary ArXiv: 0805.0364
run4
D0
PRL. 94 (2005) 62301
run3
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Nbin scaling Charm x-section ~ Nbin.
STAR Preliminary ArXiv: 0805.0364
run4run3
NPE+D0 NPE+μ+D0
NPE+μ
Difficulties:
Short life time
Low production rate
Large combinatorial bg
D0 in 200GeV p+p
Mass window: 1.72 – 2.1 GeV/c2
~ 4signal observed.
Yifei Zhang, DNP2010 talk
0.4 < pT < 2.2 GeV/c
Mixing event
Track rotation
Same sign
run9
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Ds in 200GeV Au+Au
%5.4~ sD
Preliminary results indicate statistical hadronization.
• Assume pT spectrum shape similar to D0: 47% yield covered.• D± yields estimated from D±
/D0 ratio from e+e- data.
with the help of Silicon Vertex Tracker.
Sarah LaPointe, WWND2010 talk
I.Kuznetsova, J. Rafelski,Eur. Phys. J. C 51 1 (2007) 113-133
run7
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D* in 200GeV p+p
Background combinations:Wrong sign:D0 and -, D0bar and +
Side band:1.72< M(K) < 1.80 or1.92 < M(K) < 2.0 GeV/c2
All triggers included.More than 4 signal at low pT and very significant at high pT - mostly from EMC-based high neutral energy triggers.
%7.67~)()*(* 00 sDDDD
Yifei Zhang, DNP2010 talk
run4
D* in 200GeV p+p
All triggers included.
More than 4 signal at low pT and very significant at high pT - mostly from EMC-based high neutral energy triggers.
Wrong sign and side-band method reproduce background well.
STAR Preliminary
No significant charge asymmetry
Yifei Zhang, DNP2010 talk9
Summary: D mesons
Previous STAR NPE/μ/D0 measurents in Au+Au and d+Au show the Nbin scaling of charm x-section.
STAR Ds measurement in Au+Au tends to support the statistical hadronization model.
Open charm hadrons are reconstructed from STAR run9 p+p 200 GeV data.
4 D0 signal at low pT and more significant D* signal at high pT are observed.
Working on efficiency for pT spectra and cross-section.
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Photon conversions
→ → e+ e- in material
Dalitz decays
→ e+ e-
Heavy flavor electronsD/B → e± + X
Weak Kaon decaysKe3: K± → e± e < 3% contribution in pT > 1 GeV/c
Vector Meson DecaysJ→ e+e-< 15% contribution in all pT
Photonic electron Non-photonic electron
Electron signal and background
11%~anything 10.1%~anything
16%~anything 6.5%~anything 0
0
eDBeB
eDeD
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Long and slowly dying issue on RHIC NPE
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Results differ by a factor of two in pT spectra Total cross section p+p collisions Au+Au collisions
Investigation is underway
STAR PRL 97(2007)192301
PHENIX PRL 98(2007)172301
PRL 94(2005)082301PRL 97(2006)252002
STAR d+Au PRL 94(2005)62301
STAR
run3
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STAR preliminary
R(cm)
Beam pipe + SVT + SSD+ Dalitz
Beam pipe + Dalitz
TPC Inner Field cage
Cou
nt
STAR efforts Significantly Increase the S/B of this analysis (2008-present) Cross check NPE measurements with early runs.
Yield of conversion electrons at different radial location 13
Wei Xie, HP2010 talk
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STAR high pT NPE in 200GeV p+p
Measurement done using TPC+EMC using run08 and run05 data. pT>2.5GeV/c NPE measurement with dramatically different background agree with each other very well
• Combined using “Best Linear Unbiased Estimate”. χ2/ndf = 4.81/7 = 0.69 14
Wei Xie, HP2010 talk
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Comparison with the Published NPE Results
STAR and PHENIX NPE result in 200GeV p+p collisions consistent within errors at pT > 2.5 GeV/c
STAR High pT NPE results are consistent with FONLL in 200GeV p+p collisions15
Wei Xie, HP2010 talk
See Wenqin Xu's talk for details on eB x-section!
Away Side in medium: How does B/D lose energy? Via conical emission?
Conical Pattern in Conical Pattern in 2-Particle Correlations in Au+Au Collisions
pTtrig = 3-4.0 GeV/c;
pTasso = 0.5-1 GeV/c
Motivations Near Side:what’s the contribution of B/D decay to the non-photonic electrons?
trigger
What if we trigger on non-photonic
electrons?
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Study of heavy flavor via non-photonic electrons
• D mesons have their directions well represented by the daughter electrons, above 1.5 GeV/c.
• Electrons from B decays can represent the B meson momentum direction well if pT > 3 GeV/c.
PYTHIA
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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
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~30-60% of non-photonic electron come from B meson in 200GeV p+p collisions.
Assume the same fraction in Au+Au collisions, results indicate B meson is suppressed
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B Meson Suppression in 200 GeV Au+Au
See Andre Mischke's talk for details!
Phys. Rev. Lett. 105 (2010) 202301
run5&6
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Raw NPE-h correlation without pile-up removal in 500GeV p+p collisions.
PYTHIA simulation still shows different near-side peaks for NPE from D and B.
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NPE-h Correlation in 500 GeV p+p
Wei Li (ATHIC2010 talk)
run9
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CuCuAuAu
21.7 / 5 34.4 / 5
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B. Biritz (QM2009)
Away side broadened, beyond PYHTIA fit, in both the Au+Au and the Cu+Cu collisions
Broadened Awayside in the NPE-h Correlations
0 – 20%: 3 < pTtrig < 6 GeV/c & 0.15 < pT
asso < 0.5 GeV/c
run5
run7
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Non-photonic e-h correlations in d+Au 200 GeV
The away-side correlation can be well described by PYTHIA calculations for p+p. No medium effects seen here.
3 < pTtrig < 6 GeV/c & 0.15 < pT
asso < 0.5 GeV/c
Gang Wang, HP2010 talk
run8
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Above 1.5 GeV/c, D-decay electrons well represent the mother D mesons’ direction.
eD v2 ~ D v2Similarly, above 3 GeV/c,
eB v2 ~ B v2
Partonic Partonic flow flow picture is picture is supported supported for u, d, s.for u, d, s.What What about about heavier heavier quarks?quarks?
Motivations
PHENIX, arXiv:nucl-ex/0604011; STAR, Nucl. Phys. A 830(2009)19c.
NPE v2
Non-photonic e v2 is lower than hadron v2 (or KS0, Λ).
STAR, Phys. Rev. C 77 (2008) 54901
Gang Wang, HP2010 talk 24
run7
Summary: NPE Discrepancy in high pT NPE has been solved!
NPE-h correlations have been measured in p+p collisions to retrieve B and D contributions, and used to study B energy loss.
Using d+Au as a reference, the shape of NPE-h correlation on the away-side is found to be modified in central Cu+Cu and Au+Au collisions due to the presence of the dense medium created in these collisions.
NPE v2 values obtained via fitting the correlations fall in a reasonable range, and are lower than hadron(or KS
0, Λ) v2.
Correlations with heavy flavor tag: jet reconstruction, ridge..
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Future of Heavy Flavor Measurement at STARMTD (MRPC)
See Xin Dong's talk for details!
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backup
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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
K* in 200GeV p+p
Three different methods to reproduce combinatorial background.
Very good K*0 and K2*(1430) signal observed.
K*0
K2*(1430)
Run 9 p+p 200 GeV 105M minbias eventsYifei Zhang, DNP2010 talk
0.4 < pT < 2.2 GeV/c
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Energy loss mechanisms of non-photonic Electrons
D0
radiative energy loss
c quark
K+
l
e-/- light
(D. kharzeev, M.Djordjevic et al. )
u
c
“dead cone effect”: gluon radiation suppressed at < mQ/EQ
collision energy loss
c quark
Hot/Dense Medium
Hot/Dense Medium
(Teany, Ralf, Denes et al.)
D0
K+
l
e-/-
D0
meson energy loss
c quark u
c
Hot/Dense Medium
Ivan, et al
u
cD0
K+
l
e-/-
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