Transcript Measurement of Heavy Flavor Production in STAR Experiment at RHIC

Measurement of Heavy Flavor Production in
STAR Experiment at RHIC
W. Xie for STAR Collaboration
(Purdue University, West Lafayette)
Strong Interaction In The 21st
Century, TIFR, 2010
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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.
D0
K
+
l
K
-
• Suppression or enhancement pattern
of heavy quarkonium production
reveal critical features of the medium.
e-/-
D0

Non-photonic
electron
Open heavy flavor
e-/-
• Cold Nuclear effect (CNM):
– Different scaling properties in central
and forward rapidity region CGC.
– Gluon shadowing, etc
e+/+
Heavy quarkonia
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Some Variables to quantify the medium effect
RAA ( or RdA)
“no effect”
No medium
effect
5 N+N coll. in 1 A+A coll.
Heavy quarks are from Hard collision:
•Each collision is separated clearly.
• In the absence of any nuclear effect,
RAA 
RdA 
yield ( Au  Au)
yield ( p  p)  N (collisions )
yield (d  Au)
yield ( p  p)  N (collisions )
Yield(A+A) = yield(p+p)*N(collisions), i.e.
scale with number of collisions (Ncoll)
The larger the
energy loss
The smaller
the RAA
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The STAR Detector
MTD
MRPC ToF barrel
EMC barrel
EMC End Cap
FMS
BBC
TPC
FPD
FHC
PMD
Completed
DAQ1000
HLT
HFT
FGT
Ongoing
R&D
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Measurements on Non-photonic Electron RAA
STAR hadrons pT> 6 GeV/c
• large suppression of heavy quark production is observed
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The Large Suppression was a Surprise
K+
Hot/Dense Medium
u
c quark
e-/-
c
l
D0
“dead cone effect”: light
gluon radiation
suppressed at q < mQ/EQ
radiative energy loss
(D. kharzeev, M.Djordjevic et al. )
K+
Hot/Dense Medium
u
c quark
e-/-
c
l
D0
collision energy loss
(Teany, Ralf, Denes et al.)
K+
Hot/Dense Medium
c quark
u
e-/-
c
D0
meson energy loss
Ivan, et al
D0
l
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Do we Understand the Result?
PHENIX nucl-ex/0611018
STAR nucl-ex/0607012
•
Radiative Energy Loss with reasonable
gluon densities do not explain the
observed suppression
– Djordjevic, PLB632 81 (2006)
– Armesto, PLB637 362 (2006)
•
Collisional EL may be significant for
heavy quarks
– Wicks, nucl-th/0512076
– Van Hess, PRC 73 034913 (2006)
– Van Hess PRL 100, 192301(2008).
•
heavy quarks fragment inside the
medium and are suppressed by
dissociation?
– Adil and Vitev, hep-ph/0611109
– Similar suppression for B and D at
high-pT
Possible Key to the solution: Separate charm and bottom measurements
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Disentangle Charm and Bottom Production
e  h  rB eB h  (1  rB )eD h
rB  eB /(eD  eB )
B
• wider φ distribution for B
meson because of the larger
mass.
D
8/18
X.Y. Lin, hep-ph/0602067
•Combined fit on data to obtain
the B meson contribution to nonphotonic electron.
Disentangle Charm and Bottom Production

K
D

K
0
D
cc

0
D0

e
K

B
bb
B

e
K
D *0
D0
STAR preliminary
JPG35(2008)104117
JPG35(2008)104117
9/18
• near side: mostly from B mesons
•Away side: charm (~75%), Bottom (~25%)

B Quark contribution is Significant
Star preliminary
Nuclear Physics A830 (2009)849c
~30-60% of non-photonic electron come from B meson decay.
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Disentangle Charm and Bottom Quark Energy Loss
eBAA  eCAA
 RAA 
N bin (eBpp  eCpp )
S. Sakai : SQM08
eb
ec
 rB RAA
 (1  rB ) RAA
 rB  e /( e
pp
B
pp
B
e )
pp
C
I: Djordjevic et al, PLB 632 (2006) 81;
dNg/dy = 1000
II: Adil et al, PLB 649 (2007) 139
III: Hees et al, PRL. 100 (2008) 192301
11/18
pT > 5 GeV/c
Quarkonia Suppression: “smoking gun” for QGP
Physics Letter B Vol.178, no.4 1986
c
• Low temperature
c
• Vacuum
J/y
• High temperature
c
c
d
d
Color Screening
D+
D-
• High density
(screening effect take place)
The melting sequence: cc -> Y’ -> J/y -> Upsilon
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The life of Quarkonia in the medium can be complicated
• Observed J/y is a mixture of direct production+feeddown.
– All J/y ~ 0.6J/y(Direct) + ~0.3 cc + ~0.1y’
• 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)
c
J/y
c
c
• Hot/dense medium effect
– J/y,  dissociation, i.e. suppression
– Recombination from uncorrelated charm pairs
– Survival (or not) in the hot/dense medium from lattice calculation
D+
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Quarkonia Signals in STAR
arXiv:1001.2745
STAR Preliminary
STAR Preliminary
forward J/ψ
STAR Preliminary
STAR Preliminary
J/ψ from χc enriched
STAR Preliminary
•STAR can measure Quarkonia
• of all different kind (, J/ψ, χc, …)
• in all pT range.
• at both mid and forward rapidity
• in all collision species.
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J/y Production in 200GeV p+p collisions
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 Mode:

Phys.Rev.C80:041902,2009


M. Bedjidian et al., hep-ph/0311048;
R. Vogt private communication
Include feeddown from Xc and ψ’
Agree with the data
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J/y-hadron Azimuthal Correlation in 200GeV p+p Collisions
Phys.Rev.C80:041902,2009


Constrain B meson yield through BJ/y: (13 ± 5) % of total J/y
(pT>5GeV/c)
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
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J/y Suppression/enhancement in 200GeV A+A Collisions
Au+Au Collisions:
• Nice agreement with PHENIX
Star preliminary
Au+Au: 0-80%
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
Phys.Rev.C80:041902,2009
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 Production in 200GeV p+p Collisions
arXiv:1001.2745
arXiv:1001.2745
arXiv:1001.2745
Bee
d
dy
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 114  38( stat ) 24
( sys )
pb
y 0
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RdAu ( ) in 200GeV d+Au Collisions
NPA830(2009)235c
NPA830(2009)235c
d
Bee
dy
 35  4( stat )  5( sys ) nb
y 0
RdAu  0.98  0.32( stat )  0.28( sys )
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Future of Heavy Flavor Measurement at STAR
MTD (MRPC)
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Courtesy of T. Ullirich
Examples of Future Measurements
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Summary and Perspective
Heavy flavor Studies at RHIC is at its early stage
Expecting exciting results in the coming years
with upgraded detectors and luminosity.
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backup
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Non-photonic e-h correlations in Au+Au 200 GeV
STAR Preliminary
Au+Au: 0-20%
3 < pTtrig < 6 GeV/c && 0.15 < pTasso < 1.0 GeV/c
24/18
Discrepancy between STAR and PHENIX
• A factor of two difference between STAR and PHENIX
• In high pT yield
•Total cross section
• in all collision species.
•STAR New Measurements in p+p collision will come out soon.
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Forward Meson Spectrometer (FMS)
• 20x more acceptance than previous forward detectors at
STAR
• Full azimuthal coverage for 2.5 < η < 4
FPD
• Increased acceptance not
only increases pion yields and
kinematic range but also gives
much higher geometric
efficiency for high-xF J/ψ
3/31/2009
FMS
Geometric
Efficiency:
J/ψ xF
Chris Perkins
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Continuum contribution under Upsilon Peak
 DY b b  38  24 pb
D0 Signal
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J/y Suppression in Au+Au collisions
1
CNM: abs = 1-3 mb
RAA
0
Bar: uncorrelated error
Bracket : correlated error
1
0
RAA (1.2<|y|<2.2) /RAA (|y|<0.35)
•
Larger suppression in forward rapidity comparing to midrapidity.
•
CNM suppression can not explain the results in Au+Au collisions
Comparing RHIC to SPS Suppression results
NA50
at at
SPSSPS
(0<y<1)
NA50
(0<y<1)
PHENIX
at RHIC
(|y|<0.35)
NA50
SPS
(0<y<1)
PHENIX
atat
RHIC
(|y|<0.35)
PHENIX at RHIC (1.2<|y|<2.2)
NA50 at SPS (0<y<1)
PHENIX at RHIC (|y|<0.35)
PHENIX at RHIC (1.2<|y|<2.2)
NA50
NA50(0<y<1)
(0<y<1)
Bar: uncorrelated error
Bar:
uncorrelated
Normalized
by error
NA51
Bracket
: correlated
error p+p data
Bracket
:
correlated
error
Global
error = 12%based
and
with correction
on
Globalerror
error==7%
12%
isnot
not
shown
Global
are
shown
Eur. Phys. J. C39 (2005)
: 355
• Suppression pattern similar in RHIC and SPS. • After removing the CNM effect, differences
start to show-up.
• CNM effect not removed yet.
•suppression at SPS consistent with the
melting of psi’ and chi_c?
•Need more precise d+Au measurements
Do we understand J/y results
Rapp
direct
Rapp
direct
Capella
1mb
Capella
1mb
Capella
3mb
Capella
3mb
Satz (w/ CNM)
•Models that include only anomalous
suppression predict too much
suppression for RHIC mid-rapidity
•Satz - color screening in QGP with CNM
added (EKS shadowing + 1 mb)
• Capella – comovers with normal
absorption and shadowing
• Rapp – direct production with CNM
effects (without regeneration)
• Models including both suppression
and recombination match data better
•R. Rapp(for y=0) PRL 92, 212301 (2004)
•Thews (for y=0) Eur. Phys. J C43, 97 (2005)
• Nu Xu et al. (for y=0) nucl-th/0608010
• Bratkovskaya et al. (for y=0) PRC 69,
054903 (2004)
• A. Andronic et al. (for y=0) nucl-th/0611023
• All seems to be somewhat more
consistent with the data.
•Other sensitive comparisons are needed
Flow of electrons from Charm and Bottom meson decay
[Phys.Lett. B595 202-208 ]
[PRC72,024906]
[PRC73,034913]
[PRB637,362]
 Strong elliptic flow for non-photonic electron
 Main source is D meson -> indicate non-zero D v2
 Charm v2 also non-zero ?
 Bottom sneak in here?
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LO
NLO
NNLO
PRL 101, 152001
35