Charm Production at Large Rapidities in pp and dAu Collisions at RHIC
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Transcript of Charm Production at Large Rapidities in pp and dAu Collisions at RHIC
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April 21, 2006 X. R. Wang, DIS2006, Tsukuba, Japan 1
Charm Production at Large Rapidities in pp and
dAu Collisions at RHIC
Xiaorong Wang for PHENIX collaboration
New Mexico State University
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Xiaorong Wang, SQM 2006 2April 21, 2006
The PHENIX Detectors
South Muon arm : -1.2 > > -2.0 North Muon arm : 2.4 > > 1.2
golddeuteron
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Xiaorong Wang, SQM 2006 3April 21, 2006
Physics Questions
Cold nuclear medium effects: Parton distributions
gluon (anti)shadowing CGC
Interactions with medium Parton energy loss QCD Power Correction
Recombination
New probes: Charm
PHENIX Preliminary
Au-goingd-going
Direction
High pT light hadrons
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Xiaorong Wang, SQM 2006 4April 21, 2006
Gluon Shadowing in Heavy Nucleus
X
y
yield
Universal
)(ˆ)()( 2121 zDdxFxFd QQxxQQpp
From Eskola, Kolhinen, VogtNucl. Phys. A696 (2001) 729-746.
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Xiaorong Wang, SQM 2006 5April 21, 2006
Shadowing at Forward rapidity in dAu collisions
Color Glass Condense Dynamic Multiple
Scattering Power Correction
J. Qiu & I. Vitev
D. Kharzeev & K. Tuchinhep-ph/0310358
Power correction only
CGC
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Xiaorong Wang, SQM 2006 6April 21, 2006
Recombination
“Explains” light hadron yields in forward and backward rapidities Input: low pT forward
/backward hadron distributions
Expect similar effects on open charm(?)
Measurement of charm yields could provide additional constrains on these models
H
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Xiaorong Wang, SQM 2006 7April 21, 2006
Prompt µ background subtraction
Punch-through hadrons: Data driven method to Estimate
attenuation
Decay muons: Vertex distribution analysis
Open Charm Analysis Techniques
Decay muons
Punch-through hadronsPrompt muons ?
Gap2 Gap3 Gap4
Prompt+decay muons
Hadron
num
ber
of
trac
ks
00 37.0)( NeNiNiL
Muondetector
absorber
decay
punchthrough
prompt
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Xiaorong Wang, SQM 2006 8April 21, 2006
Comparison Prompt - pt spectrum with theory
FONLL: Fixed Order next-to-leading order terms and Next-to-Leading-Log large pT resummation.
FONLL and PYTHIA calculation under predicted PHENIX Data at forward rapidity,
Run2pp -
FONLL: Solid line and bandWithout scaling the charm contribution: dotted linembsyspythiasysdata
statdy
dy
cc
).(.).(105.0
.)(013.0243.0|
049.0087.0
6.1
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Xiaorong Wang, SQM 2006 9April 21, 2006
Prompt ’s pT spectra in dAu collisions and RdAu
North Arm: d going direction;
South Arm: Au going direction
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Xiaorong Wang, SQM 2006 10April 21, 2006
How about J/Psi?
_NO_ Recombination! Gluon shadowing/saturation Initial state parton energy loss J/Psi final state nuclear
absorption has minimal effects on the shape
X
RdA
0
0.2
0.4
0.6
0.8
1.0
1.2
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Xiaorong Wang, SQM 2006 11April 21, 2006
Shadowing or Energy Loss ?
)1972( ppdA
Shadowing is not enough
Initial state energy loss? Incoming gluons
loss energy before the hard collisions
Affects low pT particle production in the FWD and BWD papidities
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Xiaorong Wang, SQM 2006 12April 21, 2006
pT broadening: Cronin Effect
Broadening of J/ pT distribution suggests initial scattering (maybe also energy loss) is important
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Xiaorong Wang, SQM 2006 13April 21, 2006
Summary and Outlook Physics at Forward and Backward Rapidity:
open charm J/psi
Observed: heavy ~ ligh hadrons suppression in the forward enhancement in the backward
Causes for such effects are not very clear Shadowing: CGC, Power correction Initial state energy loss recombination Need more theoretical work
Need/Like to have: Lower energy dAu collisions: stay away from shadowing regions Explore { x, Q, sqrt(s) } space -> (y, pT, sqrt(s)) experimentally
Parton energy loss vs shadowing pT evolution – shadowing vs power correction Shadowing vs recombination
Explore QCD dynamics in details in coming years!
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Xiaorong Wang, SQM 2006 14April 21, 2006
Backup
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Xiaorong Wang, SQM 2006 15April 21, 2006
Sources of prompt muons (pT> 0.9GeV) (determined from Pythia)
D±±, … , c++,
B± ±
± ±
* + -
q q * + -
J/,… + -
, , + -
charge asymmetric
charge symmetric
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Xiaorong Wang, SQM 2006 16April 21, 2006
Nuclear Modification Factor: RdAu (decay from light hadrons)
PHENIX Preliminary PHENIX Preliminary
Au-goingd-going
Direction
RdAu vs pTRdAu vs η
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Xiaorong Wang, SQM 2006 17April 21, 2006
Experimental Challenge
Prompt Muons
Punch-through hadrons
Decay Muon
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Xiaorong Wang, SQM 2006 18April 21, 2006
PHENIX muon arms “x” coverage
From Eskola, Kolhinen, VogtNucl. Phys. A696 (2001) 729-746.
gluons in Pb / gluons in p
X
PYTHIA open charm simulation
Particle production in the d direction (north) is sensitive to the small-x parton distribution in the Au nuclei; whereas in the gold (south) is sensitive to the large-x in Au
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Xiaorong Wang, SQM 2006 19April 21, 2006
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Xiaorong Wang, SQM 2006 20April 21, 2006