# Presentation: 318488

## Nuclear Medium Effects on Heavy Flavor Production at RHIC

- Xiaochun He
- Georgia State University

**Medium**

- HCP2006, Duke University

- 5/26/2006

## Outline

- Motivation
- RHIC Experiments
- Heavy Flavor Physics at RHIC
- Open charm
- J/
- Direct Photon
- Summary and Outlook

- HCP2006, Duke University

- 5/26/2006

## If You Believe the Big Bang Model

- HCP2006, Duke University

- 5/26/2006

**Notes:**
The Big Band Model

The space-time evolution (phase transition)

Particle creation and models

My focus is on electromagnetic observables

## Work in a QCD Factory 

- Create QCD matter
- Measure created particles
- Study **medium** effects on elementary QCD processes
- Understand the matter evolution at extreme high temperature and energy density (What is the temperature anyway?)

- HCP2006, Duke University

- 5/26/2006

**Notes:**
We are doing is actually working in a QCD factory, a very expansive one.  Actually, it is NOT that expensive at all considering typical Forture 500 companies.

## RHIC Experiments

- HCP2006, Duke University

- 5/26/2006

- HCP2006, Duke University

- 5/26/2006

## Slide 7

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- 5/26/2006

## RHIC Summary, Runs 01 - 05 

- Time 05, Oct 04th 2005, Achim Franz, BNL

- RHIC Summary, Runs 01 - 05

- Time 05, Oct 04th 2005, Achim Franz, BNL

- HCP2006, Duke University

- 5/26/2006

## The nucleon-pair luminosity is defined as LNN = A1A2L, where L is the luminosity, and A1 and A2 are the number of nucleons of the ions in the two beam respectively.

- The nucleon-pair luminosity is defined as LNN = A1A2L, where L is the luminosity, and A1 and A2 are the number of nucleons of the ions in the two beam respectively.

- HCP2006, Duke University

- 5/26/2006

## Run6 Is Still Going

- HCP2006, Duke University

- 5/26/2006

## Highlights from RHIC

- OL

- HCP2006, Duke University

- 5/26/2006

## The PHENIX Detector

- HCP2006, Duke University

- 5/26/2006

## Heavy Quarks as Medium Probes

- Heavy quarks* *(*c*, *b*) provide a hard scale via their mass which allow us to make comparison with pQCD.  Three ways to make use of this:
-   Color screening of (Q-Qbar) bound states;
-   Energy loss of “slow” heavy quarks (suppressed by 	“dead-cone” effect for  < M/E);
-   D-, B-mesons as probes of collective flow.
- RHIC program: *c*-quarks and J/(and some *b*).

- HCP2006, Duke University

- 5/26/2006

## Open Charm

- HCP2006, Duke University

- 5/26/2006

## Inclusive electron Spectra from p+p at 200 GeV

- HCP2006, Duke University

- 5/26/2006

## Inclusive non-photonic electron yields in Au+Au at 200 GeV

- Most central collision

- Less central collisions

**PRL 96, 032301 (2006)**

- The spectra of electrons from heavy flavor decays were determined by subtracting cocktails of background contributions from other sources from the inclusive data.  The most important background is the 0 Dalitz decay.

- HCP2006, Duke University

- 5/26/2006

## Participant Model

**Participant and spectator**
*N*part: number of participant nucleons in collision
*N*coll: number of binary N-N collision
**Centrality**
- Determined with BBC and ZDC correlation
*N*part, *N*coll is obtained from MC with Galuber model.
- 0%: central, 100%: peripheral collision

- HCP2006, Duke University

- 5/26/2006

## Medium Effects in Heavy Ion Collisions

- HCP2006, Duke University

- 5/26/2006

**Notes:**
Copied from Isobe’s talk slide #4

## RAA for e in Au+Au Collisions

- RAA for e in Au+Au Collisions

**PRL 96, 032301 (2006)**

- HCP2006, Duke University

- 5/26/2006

**Notes:**
Nuclear modification factor RAA for electrons from heavy flavor decays as function of pT in Au + Au collisions at sqrt(s) = 200 GeV for different centrality classes.  The error bars are statistical only. Error brackets (boxes) indicate the systematic uncertainties in TAA.

For the most central collisions the pion zero RAA is shown for comparison.

## Dense Medium:  Theory Comparison

- HCP2006, Duke University

- 5/26/2006

**Notes:**
Nuclear modification factor RAA for electrons from heavy quark decays as function of pT for the 10% most central Au+Au collisions at sqrt(200) GeV in comparison with predictions from models incorporating charm quark energy loss.  Curves (1a) to (1c) include electrons from charm decays only.  They correspond to different values of the time-averaged transport coefficient q_hat, which denotes the average squared transverse momentum transferred from a hard parton per unit path length while traversing the medium and, as such, is proportional to the density of scattering centers in the medium.  

## Direct Open Charm Measurement at RHIC

**PRL 94, 062301 (2005)**

- HCP2006, Duke University

- 5/26/2006

## J/ Results from RHIC

- HCP2006, Duke University

- 5/26/2006

## Why J/

- Gluon fusion dominates J/ production, however, several competing processes need to be clear up
- Color singlet vs octet ccbar state
- Feed-down from other ccbar resonance states
- Other sources?
- What is the **medium** effects on J/?

- HCP2006, Duke University

- 5/26/2006

## J/ Cross-section vs Rapidity & Energy

- (’ may be coming soon, at least for e+e-, but higher luminosities will be needed to get significant # of counts)

- Pythia
- shape

- J/  p+p

- J/ Cross-section vs Rapidity & Energy

- HCP2006, Duke University

- 5/26/2006

## Cold Nuclear Medium Effects

- Gluon (anti-)shadowing
- Nuclear absorption.
- Initial state energy loss.
- Cronin effect

- HCP2006, Duke University

- 5/26/2006

## PHENIX J/ Nuclear Dependence

- PHENIX J/ Nuclear Dependence
- for 200 GeV pp and dAu Collisions

- Data favors weak shadowing & absorption
- With limited statistics difficult to disentangle nuclear effects
- Will need another dAu run! (more pp data also)

**Klein,Vogt, PRL 91:142301,2003**** **
**Kopeliovich, NP A696:669,2001 **

**PRL **_**96**_**, 012304 (2006)**

- HCP2006, Duke University

- 5/26/2006

## J/ Suppression Comparison

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- 5/26/2006

## Direct  from RHIC

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- 5/26/2006

## Shining Photon:  Baseline Measurement

- NO direct photon suppression (initial state), and large 0 suppression (final state)

- HCP2006, Duke University

- 5/26/2006

## Summary

- _[Link to Slide 11](slide11.xml)_

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- 5/26/2006

## Outlook

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- 5/26/2006

## More J/Results Are Coming

- J/ polarization
- J/ v2
- Bottomonium
- ...

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- 5/26/2006

## Thank You All

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- 5/26/2006

## Backup Slides

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- 5/26/2006

## RHIC-II - Quarkonia

- With detector upgrades (PHENIX and STAR):
- J/ from B decays with displaced vertex measurement (both).
- Reduce J/ →μμ background with forward μ trigger in PHENIX.
- Improve mass resolution for charmonium and resolve  family.
- See  in forward calorimeter in front of muon arms  (PHENIX) and in FMD in STAR
- And with the luminosity upgrade:
-  J/ RAA to high pT. Does J/ suppression go away at high pT?
-  J/ v2 measurements versus pT. See evidence of charm recombination?
-   RAA. Which Upsilons are suppressed at RHIC?
-  Measure c → J/ +   RAA. Ratio to J/?
-  Measure ’ RAA. Ratio to J/?
-  Measure B → J/ using displaced vertex - independent B yield measurement, also get background to prompt J/ measurement.

- From Mike Leitch, SQM2006

- HCP2006, Duke University

- 5/26/2006

##  Tc corresponds to the confinement-deconfinement transition between quarks and hadrons.

-  *Tc* corresponds to the confinement-deconfinement transition between quarks and hadrons.

- HCP2006, Duke University

- 5/26/2006

## Slide 37

- HCP2006, Duke University

- 5/26/2006

## AuAu J/ψ’s - Quark Gluon Plasma (QGP) signature?

- Debye screening predicted  to destroy J/ψ’s in a QGP with different states “melting” at different temperatures due to different binding energies.

- _AuAu J/__ψ__’s - Quark Gluon Plasma (QGP) signature?_

- NA50 anomalous suppression

- Survival probability corrected for normal absorption

- energy density

- on the other hand, recent lattice calculations suggest J/ψ not screened after all.
- Suppression only via feed-down from screened C & ’

- but recent regeneration models might give enhancement that compensates for screening?

- Karsch, Kharzeev, Satz

- screening

- regeneration

- sum

- HCP2006, Duke University

- 5/26/2006