Download - Cold Nuclear Matter Effects on Open Heavy Flavor at RHIC J. Matthew Durham for the PHENIX Collaboration Stony Brook University [email protected]

Cold Nuclear Matter Effects on Open Heavy Flavor at RHIC

J. Matthew Durhamfor the PHENIX CollaborationStony Brook University

[email protected]

Matt Durham - WWND 2011 2

Open Heavy Flavor at RHIC

Phys. Rev. Lett. 98, 172301 (2007)

One of the most striking results from RHIC is the strong suppression and flow of heavy quarks in Au+Au collisions

d+Au

Au+Au

d+Au allows quantification of nuclear effects without complications of hot medium


Cold Nuclear Matter Effects

Phys. Rev. C 74, 024904 (2006)

Mass ordering of Cronin enhancement observed for π,K,p

Does this continue with D meson? B?

MD ~1.8 GeV

Closed heavy flavor is suppressed at mid-rapidity (details in Alex’s talk next)

Open heavy flavor in d+Au can shed light on these interesting phenomena

arXiv:1010.1246


Measurement Methodology

Direct Reconstruction:

Identify parent meson via

daughter products

Indirect Method:

Measure leptons from D/B decays

Straightforward triggering scheme

PHENIX is especially well suited for lepton measurements

Matt Durham - WWND 2011 52007-12-14

The PHENIX Experiment Electrons are tracked by

drift chamber and pad chamber

The Ring Imaging Cherenkov Counter is primary electron ID device

Electromagnetic calorimeters measure electron energy – allow E/p comparisons

BBC/ZDC provide MinBias trigger and centrality determination in HI collisions

e+e

Run-8 Configuration


Electron Sources Dalitz decays

Mostly Also from

Conversions in material Photons predominantly from

Kaon decays

Dielectron decays of vector mesons

Thermal/direct radiation Small but significant at high pt

Heavy Flavor Decays

ee 0

,,,

0

eeK 0

ee ,,

SIGNAL

BACKGROUND


Background Subtraction Methods Cocktail Method

PHENIX has measurements of most of the background electron sources.

A cocktail of these sources are subtracted from the inclusive electron sample to isolate the HF contribution.

Converter Method Extra material in the PHENIX

aperture intentionally increases background by a well defined amount.

Allows precise quantification of photonic background.

arXiv:1005.3674


Conversions Vast majority of conversion electrons come from photons

from , with kinematics very similar to Scale up Dalitz decay electrons by appropriate factor to

account for conversions (determined through simulation)

Cocktail Ingredients I Light mesons

Fit d+Au pion data with Hagedorn function Set other meson’s shape with mt-scaling Normalization set by particle ratios at high pt

2220mMpmp mesonttt

0 ee 0 0 ee 0


Cocktail Ingredients II Direct Photons

PHENIX p+p data, scaled up by Ncoll for each centrality

Ke3 decays Electrons from kaon decays away from the vertex are

mis-reconstructed at high pT.

Full simulation of PHENIX detector determines Ke3 contribution (only relevant at pT<1GeV/c)

A note on the J/ψ: We know J/ ψ is suppressed in d+Au We don’t yet have kinematic dependence of J/ ψ RdA

J/ ψ is significant at high pT, so knowledge of the exact behavior at pT>4GeV/c is necessary to correctly account for this contribution

As of now, J/ ψ is not subtracted


Total MB Cocktail


Converter Method

noninconv

nonoutconv

NNRN

NNN

)1(

For one day in Run-8, a brass sheet was wrapped around the beam pipe.

This increases photonic background by a well defined amount.

Precise measurements of converter material allow precise determination of Rγ via simulation


Cocktail and Converter Comparison

1

)1(

R

NNN

outconvinconv

Cocktail method gives a calculation of photonic background

Converter method gives us a measurement of photonic background

Difference is ~10% for all centralities.

Photonic cocktail components scaled to match converter data.


Photonic Backgrounds

Excellent agreement between the two methods


Heavy Flavor Electron Spectra

Subtract cocktail from the inclusive electron sample to obtain the HF contribution

Black line is Ncoll scaled fit to p+p

With d+Au spectra, divide by scaled p+p reference to obtain RdA

ppT

eHFcoll

AudT

eHF

dAu

dpdNN

dpdN

R


Peripheral RdA


Semi-Peripheral RdA


Semi-Central RdA


Central RdA


Minimum Bias RdA


Peripheral RdA consistent with p+p

Enhancement in open HF yields at 1<pT<4 GeV/c for more central collisions

Suppression at the highest pT

Rcp allows examination of “turn-on” of these effects within d+Au (with much smaller systematics) Aud

T

eHF

coll

AudT

eHF

collcp

dpdN

N

dpdN

NR

8860

8860

200

200

1

1

A few comments on RdA


Rcp (40-60)/(60-88)


Rcp (20-40)/(60-88)


Rcp (0-20)/(60-88)


Light Quarks Heavy Quarks

Phys. Rev. Lett. 101, 232301 (2008) arXiv:1005.1627

Phys. Rev. Lett. 98, 172302 (2007)


At pT> 4 GeV/c:

AAAA RRe 0

dAdA RRe 0

At pT< 4 GeV/c:

AAAA RRe 0


Summary PHENIX now has a full suite of heavy flavor

measurements across a wide range of Ncoll and colliding systems.

The Run-8 d+Au data set shows: Enhancement of open HF at moderate pT Suppression at the highest pT

This new reference for A+A data suggests heavy quark energy loss in the medium is even greater than previously thought:

Is the apparent difference in energy loss for light and heavy quarks really just a CNM effect?


BACKUPS


A. Dion, QM09


Centrality Determination in d+Au

Download - Cold Nuclear Matter Effects on Open Heavy Flavor at RHIC J. Matthew Durham for the PHENIX Collaboration Stony Brook University [email protected]

Top Related