# Presentation: 678613

## Recent Results from         .          . on Heavy Flavor and Electromagnetic Probes at RHIC 

- Recent Results from         .          . on Heavy Flavor and Electromagnetic Probes at RHIC

- Andrew Glenn
- University of Colorado
- for the PHENIX collaboration
- March 27, 2006

## Outline

- Electromagnetic Probes
- Direct Photons
- Virtual Photons
- Heavy Flavor Production
- Open Charm
- Hidden Charm (J/Ψ)

- Andrew Glenn

- March 27, 2006

## Electromagnetic Probes 

- 

****

**space**

**time**

******  ****Expansion  ******

**          ****QGP**
**Thermaliztion**

- e-

- e+

- electro-magnetic radiation: , e+e-, m+m-
- rare, emitted “any time”; reach detector unperturbed by strong final state interaction

- γ

- Andrew Glenn

- March 27, 2006

## 
Initial hard scattering (p+p) pQCD
Thermal radiation from QGP (1<pT<3GeV)
Hadron-gas interaction (pT<1GeV/c)()  (),  K*  K
Compton scattering in hard scattered and thermal partons (Jet-photon conversion)
Bremsstrahlung of hard scattered partons in medium (small compared to the above)

- Photon Sources

- PRC 69(2004)014903

- _Initial hard scattering__* *_(p+p) pQCD
- _Thermal radiation_ from QGP (1<pT<3GeV)
- _Hadron-gas interaction_ (pT<1GeV/c)()  (),  K*  K
- _Compton scattering in hard scattered and thermal partons_ (Jet-photon conversion)
- _Bremsstrahlung of hard scattered partons_ in medium (small compared to the above)

- Andrew Glenn

- March 27, 2006

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

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

- Direct Photon Baseline

- Andrew Glenn

- March 27, 2006

## Including Virtual Photons

- phase space factor
- 1 for high pT g

- Ratios of  *M***inv** bins to lowest one
- If no direct photons: ratios can be calculated from Dalitz decays
- If excess: direct photons

- Ratios

- Andrew Glenn

- March 27, 2006

## Thermal Hint?

- For pT<3GeV/c, thermal photon contribution looks dominant
- However, recent p+p result needs to be considered
- Factor of ~4 larger than NLO pQCD at 3GeV/c! (still within error, though)
*Smaller errors on real photon will help for making a conclusion.*

- NLO pQCD: L.E.Gordon and W. Vogelsang, PRD48(1993)3136

***pQCD is LO!***

- Andrew Glenn

- March 27, 2006

## High Mass Virtual Photons

**Measurement of Low Mass Dielectron Continuum in sqrt(s_NN)=200GeV Au-Au Collisions in the PHENIX Experiment at RHIC**
- Alberica Toia Stony Brook University

- Dilepton continuum

- Andrew Glenn

- March 27, 2006

## Photon Highlights

- High pT  (>6GeV/c ) photon yield is well described by NLO pQCD calculation
- Virtual photon measurement using very low mass dileptons improves error bars at low pT
- Hint of non-pQCD (thermal?) photons in central collisions

- Andrew Glenn

- March 27, 2006

## Heavy Quarks

- Carry the information of early stage of collisions.
- Charm quark is massive (even at RHIC energy).
- Creation takes place only at the beginning of collisions.
- How are heavy quarks are effected by the medium?

- Andrew Glenn

- March 27, 2006

## Heavy flavor electrons in p+p

- Andrew Glenn

- March 27, 2006

## Prompt  in p+p

**Appears to be little rapidity dependence of heavy quark production in p+p (large errors though)**

**Measurement of Open Heavy Flavor with Single Muons in pp and dAu collisions at 200 GeV**
- Xiaorong Wang, New Mexico State University

- Andrew Glenn

- March 27, 2006

## Quark Energy Loss

********

****

- What about heavy quarks ?
- 2001, proposed “dead cone” effect suggests smaller energy loss of charm
- Recent theories propose energy loss of charm quark is similar to light quarks.
- (Armesto et al, PRD 71, 054027, 2005; M. Djordjevic et al., PRL 94, 112301, 2005.)

- Andrew Glenn

- March 27, 2006

## Heavy Flavor in Au+Au

**preparing the high p****T **** spectrum (up to p****T**** = 10 GeV/c).**

- Andrew Glenn

- March 27, 2006

## Heavy Flavor RAA in Au+Au

** ****We see strong suppression even for heavy quark (charm).**
**The data provides a strong constraint on the energy loss models.**

**Medium Modification of Heavy Flavor Production Measured by PHENIX in Au+Au Collisions at sqrt(s_NN)=200 GeV**
- Alan Dion State University of New York at Stony Brook

- Heavy Flavor RAA in Au+Au

- Andrew Glenn

- March 27, 2006

## Open Charm Flow in Au+Au

- Theory:Greco, Ko, Rapp:   PLB 595 (2004) 202

-  Significant anisotropy is observed for heavy flavor electron.
-  v2 has good agreement of charm flow assumption below    pT < 2.0 GeV/c
-  In high pT region (pT >  2 GeV/c), v2 is reduced.   (b quark contribution?)

**The Azimuthal Anisotropy of Electrons from Heavy Flavor Decays in sqrt{s_{NN}}=200 GeV Au-Au Collisions at PHENIX**Shingo Sakai University of Tsukuba
**Elliptic flow of inclusive single muon in sqrt(s_NN) = 200 GeV Au+Au collision at PHENIX**
- IhnJea Choi Yonsei University

- Andrew Glenn

- March 27, 2006

## Theory Aside

- In a calculation by Teaney and Moore (hep-ph/0412346), they calculate the expected elliptic flow (v2) and transverse momentum modifications for different charm quark diffusion coefficients.  The two effects go hand in hand.

- Anything that increases the cross section for interactions will have this general effect.

- Andrew Glenn

- March 27, 2006

## Open Charm Highlights

- Binary scaling of total charm yield works well.
- Nuclear modification factor RAA shows a strong suppression at high pT region.
- Non zero v2 of heavy flavor electron observed.
- HEAVY QUARKS ARE SIGNIFICANTLY AFFECTED BY THE MEDIUM

- Andrew Glenn

- March 27, 2006

## J/ Production

- QGP

- Mixed phase

- Freeze out

-  Gluon Shadowing
- (Modification of
- PDF in nuclei)

- Nuclear

-  Nuclear absorption
- by the spectators
-  Cronin effect

-  Color screening
- (Dissociation by gluons)

*Need to understand the J/****production in each collision stage.*

- Andrew Glenn

- March 27, 2006

## RAA of J/ in Au+Au/Cu+Cu

- Constrained by d+Au

- Suppression increased toward the central collisions.Factor of 3 suppression at most central (Au+Au)
- Beyond the suppression from cold matter effect.
- Same pattern between Au+Au and Cu+Cu at forward-rapidity, but different pattern at mid-rapidity.

- Andrew Glenn

- March 27, 2006

## RAA and Suppression Models

- Co-mover (abs = 1mb)

- Direct dissociation
- (+Comover)

- QGP screening
- (+Comover, feed down)

**J/******** suppression **
**at RHIC is **
**over-predicted **
**by the suppression **
**models that **
**described SPS **
**data successfully.**

- Andrew Glenn

- March 27, 2006

## Recombination Models

- Better matching with results compared to the suppression models.
- Don’t forget about free paramerters.
- At RHIC (energy):  Recombination compensates stronger suppression?

- Andrew Glenn

- March 27, 2006

## Invariant pT distributions 

- Extraction of *<p**T**2**> *by fitting* *with *A(1+(p**T**/B)**2**)**-6*

- Andrew Glenn

- March 27, 2006

## <pT2> as a function of Ncol

**Au+Au = RED**
**Cu+Cu = BLUE**
- Dashed: without recombination
- Solid: includes recombination

- Recombination model
- matches better to the data...
- But don’t forget the error bars

- nucl-th/0505055

- Andrew Glenn

- March 27, 2006

## Connected Observables

- Suppression due to multiple scattering in cold nuclear matter

- A.M. Glenn, Denes Molnar, J.L. Nagle nucl-th/0602068

- Andrew Glenn

- March 27, 2006

## Rapidity dependence

- No significant change in rapidity shape in Au+Au and Cu+Cu.
- RAA is flat (within errors) as a function of rapidity, which is not predicted by the recombination model.

- nucl-th/0505055

- nucl-th/0507027

- Andrew Glenn

- March 27, 2006

## RAA vs. pT in Au+Au/Cu+Cu

- Suppression of J/ yield at low pT in both Au+Au and Cu+Cu.
- High pT J/ escape the medium? Leakage effect? [Phys. Lett. B 607 (2005)]
- Might one expect “pile up” at low pT for recombination+energy loss?

- Andrew Glenn

- March 27, 2006

## J/ Highlights

- Factor of 3 (4 Cu+Cu) suppression in most central collisions
- Beyond the suppression from cold matter effects.
- Over-predicted by the suppression models effective for SPS.
- Possible signs of recombination, but plenty of open questions (flies in the ointment?)

**J/Psi measurements in Cu+Cu and Au+Au collisions at sqrt(s) = 200 GeV by PHENIX at RHIC**Andry Rakotozafindrabe Laboratoire Leprince Ringuet (LLR) - École Polytechnique (France)

- Andrew Glenn

- March 27, 2006

##  12 Countries;  58 Institutions;  480 Participants*

**  ****USA   Abilene Christian University, Abilene, TX **
**             ****Brookhaven National Laboratory, Upton, NY **
**             ****University of California - Riverside, Riverside, CA**
**             ****University of Colorado, Boulder, CO**
**             ****Columbia University, Nevis Laboratories, Irvington, NY**
**             ****Florida State University, Tallahassee, FL**
**             ****Florida Technical University, Melbourne, FL**
**             ****Georgia State University, Atlanta, GA**
**             ****University of Illinois Urbana Champaign, Urbana-Champaign, IL**
**             ****Iowa State University and Ames Laboratory, Ames, IA**
**             ****Los Alamos National Laboratory, Los Alamos, NM**
**             ****Lawrence Livermore National Laboratory, Livermore, CA**
**             ****University of New Mexico, Albuquerque, NM **
**             ****New Mexico State University, Las Cruces, NM**
**             ****Dept. of Chemistry, Stony Brook Univ., Stony Brook, NY**
**             ****Dept. Phys. and Astronomy, Stony Brook Univ., Stony Brook, NY  **
**             ****Oak Ridge National Laboratory, Oak Ridge, TN**
**             ****University of Tennessee, Knoxville, TN  **
**             ****Vanderbilt University, Nashville, TN****	**

**Brazil        University of São Paulo, São Paulo**
**China        Academia Sinica, Taipei, Taiwan**
**                  ****China Institute of Atomic Energy, Beijing**
**                  ****Peking University, Beijing**
**France      LPC, University de Clermont-Ferrand, Clermont-Ferrand**
**                  ****Dapnia, CEA Saclay, Gif-sur-Yvette**
**                  ****IPN-Orsay, Universite Paris Sud, CNRS-IN2P3, Orsay          **
**                  ****LLR, Ecòle Polytechnique, CNRS-IN2P3, Palaiseau**
**                  ****SUBATECH, Ecòle des Mines at Nantes, Nantes**
**Germany  University of M****ü****nster, M****ü****nster**
**Hungary   Central Research Institute for Physics (KFKI), Budapest**
**                  ****Debrecen University, Debrecen**
**                  ****Eötvös Loránd University (ELTE), Budapest **
**India         Banaras Hindu University, Banaras**
**                  ****Bhabha Atomic Research Centre, Bombay**
**Israel        Weizmann Institute, Rehovot**
**Japan       Center for Nuclear Study, University of Tokyo, Tokyo**
**                  ****Hiroshima University, Higashi-Hiroshima **
**                  ****KEK, Institute for High Energy Physics, Tsukuba **
**                  ****Kyoto University, Kyoto**
**                  ****Nagasaki Institute of Applied Science, Nagasaki**
**                  ****RIKEN, Institute for Physical and Chemical Research, Wako**
**                                               ****RIKEN-BNL Research Center, Upton, NY              **
**	****     ****Rikkyo University, Tokyo, Japan             **
**                  ****Tokyo Institute of Technology, Tokyo**
**                  ****University of Tsukuba, Tsukuba **
**                  ****Waseda University, Tokyo                    **
**S. Korea   Cyclotron Application Laboratory, KAERI, Seoul**
**                  ****Kangnung National University, Kangnung**
**                  ****Korea University, Seoul **
**                  ****Myong Ji University, Yongin City **
**                  ****System Electronics Laboratory, Seoul Nat. University, Seoul**
**                  ****Yonsei University, Seoul**
**Russia      Institute of High Energy Physics, Protovino **
**                  ****Joint Institute for Nuclear Research, Dubna **
**                  ****Kurchatov Institute, Moscow**
**                  ****PNPI, St. Petersburg Nuclear Physics Institute, St. Petersburg**
**                  ****St. Petersburg State Technical University, St. Petersburg**
**Sweden    Lund University, Lund**

*** ******12 Countries;  58 Institutions;  480 Participants****

***as of January 2004**

- Andrew Glenn

- March 27, 2006

- BONUS SLIDES

- Andrew Glenn

- March 27, 2006

## Related talks at SQM

**Elliptic flow of inclusive single muon in sqrt(s_NN) = 200 GeV Au+Au collision at PHENIX**IhnJea Choi Yonsei University
**Medium Modification of Heavy Flavor Production Measured by PHENIX in Au+Au Collisions at sqrt(s_NN)=200 GeV**Alan Dion State University of New York at Stony Brook
**J/Psi measurements in Cu+Cu and Au+Au collisions at sqrt(s) = 200 GeV by PHENIX at RHIC**Andry Rakotozafindrabe Laboratoire Leprince Ringuet (LLR) - École Polytechnique (France)
**The Azimuthal Anisotropy of Electrons from Heavy Flavor Decays in sqrt{s_{NN}}=200 GeV Au-Au Collisions at PHENIX**Shingo Sakai University of Tsukuba
**Measurement of Low Mass Dielectron Continuum in sqrt(s_NN)=200GeV Au-Au Collisions in the PHENIX Experiment at RHIC**Alberica Toia Stony Brook University**Measurement of Open **
**Heavy Flavor with Single Muons in pp and dAu collisions at 200 GeV**Xiaorong Wang, New Mexico State University

- Andrew Glenn

- March 27, 2006

## PHENIX experiment

- Muon Arms:
- Muons at forward rapidity
-  J/ 
-  1.2<  < 2.4
-  P > 2 GeV/c
-  

- Central Arms:
- Hadrons, photons, electrons
-  J/ e+e-
-  0.35
-  *P**e* > 0.2 GeV/c
-  (2 arms x /2)

- Andrew Glenn

- March 27, 2006

## Measure inclusive electron pairs or photons
Measure 0 and  spectra via 2 decay, and estimate background electron-pairs or photon distribution
Other hadron spectra estimated by mT scaling of power-law fit to 0
Conservative assumption on normalization: /0=0.450.05, /0=1.0, ’/0=1.0
Look for an excess of signals over background

- Measure 0 and  spectra via 2 decay, and estimate background electron-pairs or photon distribution
- Other hadron spectra estimated by *m**T* scaling of power-law fit to 0
- Conservative assumption on normalization: ******/********0****=0.45********0.05, ********/********0****=1.0, ********’/********0****=1.0**
- Look for an excess of signals over background

- Very low-mass dileptons

***Kroll-Wada Formula***

***phase space factor is unity for high p******T****** *********

- Ratios of  *M***inv** bins to lowest one (Rdata)
- If no direct photons: the ratios become exactly what can be calculated from Dalitz decay formula above
- If excess over calculation: direct photons

- Including Virtual Photons

- Andrew Glenn

- March 27, 2006

##  excess ratio (measured/background)
Systematic error revisited and improved: pT-correlated: 7.5%, point-by-point: 7.0%

Consistent with Run2

-  excess ratio (measured/background)
- Systematic error revisited and improved: pT-correlated: 7.5%, point-by-point: 7.0%
- Consistent with **Run2**

**and very low-mass dilepton (~21% relative error to ratio)**

- Note that *dir / *incl +1 is slightly different from meas / background. Centrality range is different as well.
- Mass Range:0<Mee<30MeV/c2 (calculated from that in 90<Mee<300MeV/c2)

- Results

- Andrew Glenn

- March 27, 2006

## Very low mass dilepton ratio converted to direct photon spectrum

Assumption: dir / incl = *dir / *incl   (for Mee << M)

dir = *dir / *incl  incl
incl is real inclusive photon

- Overlaid with thermal + pQCD calc.

*** ******Additional ~10 % systematic error from inclusive*** ********* included***

- Very low mass dilepton ratio converted to direct photon spectrum
- Assumption: dir / incl = *dir / *incl   (for Mee << M)
- dir = *dir / *incl  incl
- incl is real inclusive photon

**D. d’Enterria, D. Perresounko, nucl-th/0503054**

- A Thermal Hint?

- Andrew Glenn

- March 27, 2006

## Direct photon in higher mass Dilepton?

- Contribution of *direct photons converted into electron pairs?*
- Try to see what it looks like
- Take the direct photon spectra
- Kroll-Wada’s formula to convert direct photon to electron-pair spectra
- Phase space factor considered
- (1-mee2/M2)3
- M = E,  |F(mee)| = 1
- Acceptance filter for PHENIX is not applied
- Look at higher mass region.

*Needs a detailed look with taking the acceptance into account.*

- 0

- 

**Direct photon internal conversion**

- 0-20% centrality
- pT>1.0GeV/c

- Probably not significant compared to predicted thermally radiating dilepton.

- Andrew Glenn

- March 27, 2006

## Cocktail comparison

-  Data and cocktail absolutely normalized
- Cocktail from hadronic sources
- Charm from PYTHIA
- Predictions are filtered in ***PHENIX acceptance***
- Good agreement in p0 Dalitz
- Continuum:hint for enhancement not significant within systematics
- What happens to charm?
- Single e  pt suppression
- angular correlation???
-  LARGE SYSTEMATICS!

- Andrew Glenn

- March 27, 2006

## Data/cocktail

|  | Measurement [10-5 counts/event] | Predictions[10-5 counts/event] |
| --- | --- | --- |
| 0.15-0.7 GeV/c2 | 17.8 ± 3.8 ± 1.50 | 12.3 |
| 1.1-2.5 GeV/c2 | 0.67 ± 0.50 ± 0.11 | 1.16 |

- Andrew Glenn

- March 27, 2006

## Comparison with theory

- R.Rapp, Phys.Lett. B 473 (2000)
- R.Rapp, Phys.Rev.C 63 (2001)
- R.Rapp, nucl/th/0204003

- 
- 
- 
- 

- 
- 

- Andrew Glenn

- March 27, 2006

## Total Charm Yield in Run2 Au+Au

**Binary scaling works well for total charm yield**
**dN****e****/dy is fit to AN****coll************ = 0.938+/-0.075+/-0.0018 **
***Coming soon*****: High statistic data in Run4 Au+Au**

- S.S. Adler, *et al.*, PRL 94 082301

- Andrew Glenn

- March 27, 2006

## Prompt  in Run3 d+Au 

** ****Suppression(?) ****in d going direction**
** ****Enhancement(?) ****in Au going direction**

***d***

**Au**

**South**

**North**

**Beam direction**

- Andrew Glenn

- March 27, 2006

## Heavy flavor in Run3 d+Au

**Minimum Bias****non-photonic electrons**

**PHENIX preliminary**

- Andrew Glenn

- March 27, 2006

## RAA of heavy flavor electrons

- Theory curves (1abc) from N. Armesto, *et al.*, PRD 71, 054027
- (2ab) from M. Djordjevic, M. Gyullasy, S.Wicks, PRL 94, 112301

**PRL accepted recently (nucl-ex/0510047).**

**Clear evidence **
**for strong medium effects!**

- Andrew Glenn

- March 27, 2006

## J/ measurement

**PHENIX measured the J/******** yield in p+p, d+Au, Au+Au and Cu+Cu to understand the J/******** production in each stage of collisions.**

- Base line for all measurements
- J/as a function of ***rapidity, p******T***

- Initial stage effect
-  Gluon shadowing
- Nuclear medium effect
-  Nuclear absorption
-  Cronin effect
- J/  as a function of
***rapidity, p******T******, X******Au***

- p+p collisions

- d+Au collisions

- Andrew Glenn

- March 27, 2006

## PHENIX measured the J/ yield in p+p, d+Au, Au+Au and Cu+Cu to understand the J/ production in each stage of collisions.

- Au+Au collisions
- Cu+Cu collisions

- Extract the medium effect
-  Color screening
-  Coalescence
- J/  (yield) as a function
***rapidity, p******T***
***collision centrality***
***collision species (Au+Au/Cu+Cu)***
***collision energy (200GeV/62.4GeV)***

- p+p/d+Au collisions

- Note that feed down effect from c and ’ is also important.
- But they are not accessible with the current RHIC luminosity.

- J/ measurement

- Andrew Glenn

- March 27, 2006

## J/ cross section in p+p 

**Cross section vs. rapidity and energy dependence **

- Integrated cross section  = 2.61+-0.20(fit)+-0.26(abs) b
- Gives a good base line for d+Au, Au+Au and Cu+Cu.

- nucl-ex/
- 0507032
- Accepted
- in PRL

- Andrew Glenn

- March 27, 2006

## J/ in d+Au Collisions

- gluons in Pb / gluons in p

**X**

- Eskola, et al.,  Nucl. Phys. A696 (2001) 729-746.

- South muon arm (y < -1.2) :
**large X****Au**** ******** ****0.090**
- Central arm (y  0) :
**intermediate X****Au**** ******** 0.020**
- North muon arm (y > 1.2) :
**small X****Au**** ******** ****0.003**

**Understand the cold matter effects**
- Gluon Shadowing
- Cronin effect (pT broadening)
- Nuclear Absorption
**Coverage of X****Au**** in d+Au ****at PHENIX**

- Andrew Glenn

- March 27, 2006

##  J/ in d+Au vs. pT

**Cronin effect (p****T**** broadening)**

- Observation of pT broadening at RHIC.
- Initial state multiple scattering of partons

- nucl-ex/0507032
- accepted in PRL

- Andrew Glenn

- March 27, 2006

## pT broadening

**Suppression factor ********:**
****** ****vs. p****T**** **
**Comparison to **
**E866 at ********s = 39 GeV.**

- dAu = pp (2x197)****

- Trend of pT broadening
- at RHIC is consistent
- with E866 results.

- nucl-ex/0507032
- Accepted in PRL

- Andrew Glenn

- March 27, 2006

## Nuclear Absorption and Shadowing

**R****dAu**** vs. rapidity,  centrality, ******** vs. x coverage**

- RdA

- 0

- 0.2

- 0.4

- 0.6

- 0.8

- 1.0

- 1.2

**Rapidity**

**R****dAu**

- Weak nuclear absorption :  =1–3 mb  (4.3 mb at SPS)
- Suppression increased weakly toward the central collisions.
- Weak shadowing (violation of XAu scaling) :  > 0.92

- nucl-ex/0507032
- Accepted in PRL

- Andrew Glenn

- March 27, 2006

## Summary (d+Au J/ measurements)

**Observation of Cronin effect (p****T**** broadening)**
**Trend of Cronin effect is consistent  with lower**
**energy results.**
**Observation of nuclear absorption and shadowing **
**effect.**
- Nuclear absorption at RHIC is weak (1-3mb)
- compared to lower energy results (SPS, FNAL)
- Shadowing effect is weak
**A modest baseline measurement for A+A collisions. **
**Further statistics are needed for the detail study of cold matter effects.**

- Andrew Glenn

- March 27, 2006

## Invariant pT distributions 

- Extraction of *<p**T**2**> *by fitting* *with *A(1+(p**T**/B)**2**)**-6*

- Andrew Glenn

- March 27, 2006

## Feed down and J/ suppression

- Feed down and J/ suppression

**Feed down from ********c ****and ********’ is important.**
- 30% from c and 10% from ’ (FNAL E705, HERA-B)
- Tdiss(’)  Tdiss() 1.1 Tc << Tdiss(J/) 2 Tc (Lattice calc.)
*J/****suppression at RHIC could be due to the melt of ****c **and ****’? (*_*J/*__**__*would survive at RHIC.*_*)*

- The melt of c and ’ can
- explain Jsuppression
- at SPS.

- How about J/suppression
- at RHIC?

- Describe well up to mid-central
- and more suppression at most
- central.
- Feed down is larger at RHIC?
- Melting of J/at most central?
- Need to study c and ’
- production at RHIC (RHIC-2).

- Andrew Glenn

- March 27, 2006