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)

2

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

3

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

6

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

8

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

9

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

10

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

11

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

12

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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16

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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

24

Rapidity Expansion

e μ

μ

Aud

Mid BwdFwd

Rg from EPS09

• The difference between forward and backward is larger than the expectation from EPS09s

25

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