identified particle dependence of nuclear modification factors in d+au collisions at rhic
DESCRIPTION
Identified Particle Dependence of Nuclear Modification Factors in d+Au Collisions at RHIC. Lee Barnby - University of Birmingham For the STAR Collaboration. Outline. Motivation for d+Au measurements Previous p+A results Au+Au results STAR setup for d+Au run - PowerPoint PPT PresentationTRANSCRIPT
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Identified Particle Dependence of Nuclear Modification Factors in
d+Au Collisions at RHIC.
Lee Barnby - University of Birmingham
For the STAR CollaborationQuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.
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Outline
• Motivation for d+Au measurements– Previous p+A results
– Au+Au results
• STAR setup for d+Au run• Nuclear modification factors in d+Au• Implications for Au+Au interpretation • Forward rapidity region• Summary and outlook
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Motivation• Species dependent Cronin effect at lower
energies.– Cronin effect decreasing with increasing √s.– Still existing at √s = 200 GeV?
• Final state explanation for high pT suppression and disappearance of back-to-back correlations in Au+Au but…
– What about particle dependence of nuclear modification factors in Au+Au at intermediate pT?
• RHIC provided d+Au rather than p+Au collisions purely for technical reasons.
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Lower energy p+A
measurements
PRD 11, 3105 (1975) Cronin et. al
€
I( pT , A) = I( pT ,1)Aα ( pT )
Enhancement growing with pT
Larger enhancement with heavier particle: < proton
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Lower Energy Cronin effect
data• Ratio of per nucleon
cross sections for p+W and p+Be collisions at √s=38.8 GeV – Enhancement varies
with pT and with particle species
pT GeV/c
PRL 68, 452 (1992) Straub et al.
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Lower Energy Cronin data (II)
√s
• Cronin enhancement decreasing with increasing √s
• Certainly for , K• Trend less clear for proton?
• Larger magnitude effect for p
RW
/Be
PRL 68, 452 (1992) Straub et al.
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Au+Au Nuclear Modification
PRL 91, 072302 (2003) STAR
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Au+Au Nuclear Modification
PRL 91, 072302 (2003) STAR
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Au+Au Nuclear Modification
See poster by P. Sorensen (STAR)
Different behaviour for and K0 in pT 2-4 GeV range.
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d+Au Nuclear Modification h±
STAR, PRL 91 (2003) 072304
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STAR Setup
• 10 M minimum bias d+Au events used.• Main TPC at mid-rapidity measures charged
tracks– Reconstruct “V0s” p and
s
– And “kinks” K±± K±±
• TOF at mid-rapidity identifies , K, p• FTPC reconstructs charged tracks at forward
rapidity ( ~ 3)– Used in centrality classification
See poster C.Mironov
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Spectra √s=200 GeV d+Au collisions
K0S
PT [GeV/c]
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Spectra √s=200 GeV p+p collisions
See poster J. Adams & M. Heinz
STAR Preliminary
PT [GeV/c]
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Nuclear modification factors
€
RAB =d2N /dptdη
TAB d2σ pp /dptdη
Rd
Au
K0s
STAR Preliminary
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Nuclear modification factors
h±
K0s
h± data PRL 91 (2003) 072304
STAR Preliminary
Rd
Au
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Nuclear modification factors
STAR Preliminary
Rd
Au
STAR TOF data nucl-ex/0309012
h±
K0s proton
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Nuclear modification factors
STAR Preliminary
Rd
Au
STAR TOF data nucl-ex/0309012
h±
K0s proton K±
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Nuclear modification factors
STAR Preliminary
Rd
Au
STAR TOF data nucl-ex/0309012
h±
K0s proton K±
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Central to peripheral
STAR Preliminary
PT [GeV/c]
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Au+Au interpretation
Difference between identified particle nuclear modification factors also seen in d+Au collisions. However they are smaller and unlikely to explain difference in RCP at intermediate pT
• Order 20% not a factor 2.
Baseline for suppression in central Au+Au is actually is close to Nbinary scaling
• Depends on details of convoluting d+Au collisions
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Au+Au Nuclear Modification
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Spectra at forward rapidities
dN/d STAR Preliminary
See poster J. Putschke
• Minimum bias curve shows agreement with PHOBOS and with HIJING model
• Dotted lines are saturation model predictions for centrality selections
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d+Au RCP at forward rapidities
PT [GeV/c]
RC
P • Au-Side RCP shows almost no variation with centrality
• d-side is interesting: more central is more suppressed
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Summary and Outlook
• Particle dependence of nuclear modification factors in d+Au of order 20% unlikely to explain RCP differences in d+Au.
• More conspicuous differences at forward rapidity on d-side.
• More p+p data required to go further in pT and improve precision of RdAu measurement.