PHENIX Heavy-Flavor Results
Matt Snowball (LANL)
on behalf of the PHENIX collaboration
Hard Probes 2015
e
μ
The PHENIX Detector and Heavy Flavor
• Mid-rapidity Electrons– |η| < 0.35– Δϕ = π– Tracking: DC, PC– eID: RICH, EMcal
• Forward/Backward-rapidity Muons
– 1.2 < |η| < 2.2– Δϕ = 2π– ~10λ absorber– Tracking: wire chamber– MuID: 5 layers of steel
and Iarocci tube plane
• Measurement of leptons from semi-leptonic
decays of D/B mesons– Imperative to understand/subtract background from other lepton
sources(hadron cocktail method)
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Heavy Quark Production
• Heavy quarks produced in early stage of collision
– Dominant production mechanism is gluon-gluon fusion at RHIC energy– Experience full evolution of medium in heavy-ion collisions
• Heavy Flavor is like a tracer moving through the medium, allowing to uniquely probe its evolution
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Heavy Quark Production
• By changing the size of the system with different nuclei we can follow the evolution of the medium
• RHIC is well suited to be able to change from small to very large systems• Leptons from Heavy Flavor become a unique reference to watch as the system
size changes
p+p
Ncoll=1
Au+Au Ncoll~1000
d+AuCu+Cu
Au+Au
We can study evolution of medium effects/modification
as system size increases
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5
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d+Au Results
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mid
Electrons at Mid-Rapidity
Consistent with scaled p+p results
Enhancementat intermediate pT
Phys. Rev. Lett. 109, 242301 (2012)
e
AudRg from EPS09
Shadowing/Anti-Shadowing Transition
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Central: Peripheral:
fwd bwd
Muons at Forward/Backward Rapidity
Phys. Rev. Lett. 112, 252301 (2014)
Consistent with scaled p+p results
Enhancementat backward rapidity
μμ
AudRg from EPS09
Shadowing Region
Anti-Shadowing Region
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Suppressionat forward rapidity
Central: Peripheral:
d+Au: Small But Surprising
QGP medium in d+Au collisions?– long-range correlation– elliptic flow
arXiv:1404.7461
Peripheral Central
Mid/Backward-yRdA > 1
Forward-yRdA < 1
All-yRdA ≈ 1
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fwd mid
Electron-Muon Correlation
Phys. Rev. C. 89, 034915 (2014)
• pQCD-based models agree with the data in p+p collisions• Clear suppression of e-mu correlation in d+Au collisions
– CNM effects from heavy nuclei
e μ
AudRg from EPS09
p+p d+Au
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Explanations?
Phys. Rev. C. 88, 024906 (2013)
• Initial-state effects fail to reproduce the data at both rapidity simultaneously • Modification of nPDF• Initial kT broadening
• Cronin enhancement?• Initial kT component due to multiple scattering of incoming partons
consistent with nPDF modification
enhancement beyond nPDF modification
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Where is theory on this?
• pQCD calculation considering incoherent multiple scattering reproduce the enhancement at backward rapidity
Phys. Lett. B731 (2014) 51
• Radial flow also qualitatively reproduce the enhancement
13 Phys. Lett. B740 (2015) 25
I. Vitev et al
A. Sickles
Where is theory on this?
• pQCD calculation considering incoherent multiple scattering reproduce the enhancement at backward rapidity
Phys. Lett. B731 (2014) 51
• Radial flow also qualitatively reproduce the enhancement
Phys. Lett. B740 (2015) 2514
I. Vitev et al
A. Sickles
Heavy Flavor Comparison with J/ψ
J/ψ: Phys. Rev. C. 87, 034904 (2013)
• Similar suppression at forward rapidity– Low co-mover density– Same suppression mechanism
• Different behavior at mid and backward rapidity– Different suppression mechanism
• Larger nuclear break-up effects at higher-density region
d-Going Mid-Rapidity Au-Going
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Cu+Cu Results
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Phys. Rev. C. 90, 034903 (2014)
<Ncoll> ≈ 182.7
<Ncoll> ≈ 5.1
• RAA
– Significant enhancement in peripheral events– Slight suppression in central events
• RCP shows a significant suppression– Hot Nuclear Matter effects dominate in
central Cu+Cu collisions
<Ncoll> ≈ 182.7
<Ncoll> ≈ 5.1
Cu+Cu Collisions
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Mid-y Electrons
Comparison Between Systems
• Mid-rapidity HF electrons• Very nice agreement between similar systems!• Consistent nuclear modification factors between d+Au, Cu+Cu, and
Au+Au collisions of similar system size (Npart)
CENTRAL d+Au ≈ PERIPHERAL Cu+Cu CENTRAL Cu+Cu ≈ MID Au+Au
20 PRC 90 034903 (2014)
Evolution of HF e production
• The nuclear modification factors for HF electrons at mid-rapidity in d+Au, Cu+Cu, and Au+Au
• Nice trend from smaller systems, d+Au and peripheral Cu+Cu, where enhancement effects are dominating to central Cu+Cu and Au+Au collisions, where suppression effects take over
21 PRC 90 034903 (2014)
Future Measurements!
PHENIX silicon vertex tracking system
• Good data samples with the VTX/FVTX of p+p, p+Au, and Au+Au collisions have been collected!– charm/bottom production ratios can be obtained with DCA– charm/bottom separated RAA, RpA can also be obtained
– VTX/FVTX results coming for QM15
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Summary
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• Open Heavy Flavor in d+Au• Suppression at +y - Consistent with nPDF modification, E-loss• Enhancement at mid-y - Beyond nPDF expectations. Cronin? Multiple scattering?• Enhancement at -y - Beyond nPDF expectations. Consistent with incoherent
multiple scattering
• Quarkonia in d+Au• J/ψ Suppression at +y - Similar behavior to muons from open HF• J/ψ Small enhancement at –y - Evidence for extra mechanism → Nuclear break-up?
• Similar sized systems from d+Au, Cu+Cu, and Au+Au give similar Nuclear Modification Factors
• FVTX results expected soon!• DCA Analyses for HF production ratios
BACK UP
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Rapidity Expansion
e μ
μ
Aud
Mid BwdFwd
Rg from EPS09
• The difference between forward and backward is larger than the expectation from EPS09s
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Rapidity Expansion in Cu+Cu
• Larger suppression at forward rapidity– may need additional CNM effects (shadowing) at forward rapidity– theoretical calculations considering both hot and cold nuclear matter effects
• consistent with the data at forward rapidity
• slightly overestimate the suppression at pT > 3GeV/c, but does not match at pT < 3GeV/c at mid-rapidity
HF μ:Phys. Rev. C 86, 024909 (2012)
theoretical calculation:R. Sharma, I. Vitev, B.-W, ZhangPhys. Rev. C 80, 054902 (2009)
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Most Central Collisions
HF e @ mid-rapidity
<Ncoll>≈15.1<Ncoll>≈182.7<Ncoll>≈995.4
Phys. Rev. C. 90, 034903 (2014)
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HF e in Au+Au Collisions - 62.4 GeV
• Enhancement relative to scaled p+p results (ISR data)– Cronin-like enhancement is dominating at lower beam energy?– sizeable difference from the theory considering energy loss
arXiv:1405.330128