# Presentation: 540071

## Heavy Quark and Quarkonia  Mesurements

- W. Xie
-  *(Riken BNL Research Center, BNL)*

- RHIC/AGS users meeting 2007

## Thanks Alex, Maunal, Pibero and others for providing additional STAR information.

## Motivation for Studying Heavy Quarks

- Heavy quark mass are external parameter to QCD.
- Sensitive to initial gluon density and gluon distribution.
- energy loss feature different from light quarks. Its suppression and the flow capability provide key information on the hot/dense medium properties.
- Suppression or enhancement pattern of heavy quarkonium production reveal critical features of the medium.
- Cold Nuclear effect (CNM):
- Different scaling properties in central and forward rapidity region CGC.
- Gluon shadowing, etc

## Heavy Quark Energy Loss in the Medium

- D0

**radiative energy loss**

- c quark

- K+

- e-/-

**(D. kharzeev, M.Djordjevic**** *****et al. )***

- c

**“****dead cone effect”:**
-  gluon radiation suppressed at **< *m*Q/*E*Q

**collision energy loss**

- c quark

**Hot/Dense Medium**

**Hot/Dense Medium**

- (**Teany, Ralf, Denes et al.)**

- e-/-

## Variables to quantify the medium effect

- _Heavy quarks are from Hard collision: _
- Each collision is separated clearly.
-  In the absence of any nuclear effect,
- Yield(A+A) = yield(p+p)*N(collisions), i.e. scale with number of collisions (**Ncoll**)

- “no effect”

**R****AA**** ( or R****dA****)**

**No medium effect**

## How Measurements has been done 

**D****0**

- K+

- **l**

- K-

**e****-****/********-**

**e****+****/********+**

- Open heavy flavor

_**PHENIX Measurement**_
- Little material to produce background.
- different methods

## Measurement in p+p collisions: the reference

** ****Both PHENIX and STAR provide precise measurement extent to large pT. **
** ****Within errors, PHENIX measurements agrees with FONLL calculation. **
**But the two experiment disagree by a factor of two while both experiment are self-consistent on different type of measurements. **

## The difference also appears in Au+Au Collisions

- _Road to the possible solution in the near future: _
**Direct D meson measurement from PHENIX. **
**Low material run from STAR aiming at RUN8 and thereafter.**
**The difference is cancelled out when calculate R****AA**
** ****The two experiment get consistent ****R****AA ****!!**

## Measurements on RAA in Au+Au collisions

-  large suppression of charm quark production is observed
-  D meson probably less suppressed than light hadrons.
- Where the bottom show up in the spectrum?

## Do we Understand the Result?

- Radiative Energy Loss  with reasonable gluon densities do not explain the observed suppression
- Djordjevic, Phys. Lett. B632 81 (2006)
- Armesto, Phys. Lett. B637 362 (2006)
- Collisional EL may be significant for heavy quarks
- Wicks, nucl-th/0512076
- van Hess, Phys. Rev. C73 034913 (2006)
- heavy quarks fragment inside the medium and are suppressed by dissociation?
- Adil and Vitev,  hep-ph/0611109
- Similar suppression for B and D at high-pT

- PHENIX nucl-ex/0611018
- STAR nucl-ex/0607012

## Energy Loss and Flow are Closely connected

-  Charm was NOT expected to flow with the medium since it’s too heavy !

## Flow of electrons from Charm and Bottom meson decay

-  Strong elliptic flow for non-photonic electron
-  Main source is D meson -> indicate non-zero D v2
-  Charm v2 also non-zero ?
-  Bottom sneak in here?

- [Phys.Lett. B595 202-208 ]

- [PRC72,024906]

- [PRC73,034913]

- [PRB637,362]

## Constraints of /s from charm measurements

- “Perfect Fluid”: viscosity close to quantum limit:
- Rapp and van Hees _[Phys.Rev.C71:034907,2005](http://arxiv.org/abs/nucl-th/0412015)_
- Simultaneously describe PHENIX RAA(E) and v2(e) with diffusion coefficient in range DHQ ×2T ~4-6
- Moore and Teaney _[Phys.Rev.C71:064904,2005](http://arxiv.org/abs/hep-ph/0412346)_
- Find DHQ/(/(e+p)) ~ 6 for Nf=3
- Calculate perturbatively, argue result also plausible non-perturbatively
- Combining
- Recall   e+p = T s    at mB=0
- This then gives ******/s ~(1.5-3)/4******

## One attempt to separate B and D mesons: e-hadron correlations in p+p: bottom vs. charm 

-  PHENIX also doing charge correlation in the mass space. Results coming out soon.
** ****Direct measurements via VTX upgrade is needed for Au+Au collisions **

## Quarkonia Suppression: “smoking gun” for QGP

- Physics Letter B  Vol.178, no.4 1986

**J/******

**D****+**

-  Low temperature
-  Vacuum

-  High temperature
-  High density
- (screening effect take place)

- The melting sequence:   c -> ’ -> J/ -> Upsilon

- d

**D****-**

## The life of J/ in the medium is very complicated

- _Observed J/____ is a mixture of direct production+feeddown._
-  All J/ ~ 0.6J/(Direct) + ~0.3c + ~0.1’
- Important to disentangle different component (*through upgrade*)
- _Suppression and enhancement in the “cold” nuclear medium_
-  Nuclear Absorption, Gluon shadowing, initial state energy loss, Cronin effect and gluon saturation (CGC)
- _Hot/dense medium effect _
-  J/ dissociation, i.e. suppression
-  Recombination from uncorrelated charm pairs
- Survival (or not) in the hot/dense medium from lattice calculation
- See Agnes Mocsy’s presentation during the workshop.

- D+

**J/******

## J/ Baseline Measurement via p+p and d+Au collision

- J/**** Baseline Measurement via p+p and d+Au collision

-  high precision p+p results
-  d+Au favor σABS ~ 0-3 mb.

- Bll* pp(J/ )=178±3(stat)± 53(sys) ± 18(lum) nb

## J/ Suppression in Au+Au  collisions

- RAA (1.2<|y|<2.2) /RAA (|y|<0.35)

- 1

- RAA

- 0

- 1

- 0

- Bar: uncorrelated error
- Bracket : correlated error

- Larger suppression in forward rapidity comparing to midrapidity.
- CNM suppression can not explain the results in Au+Au collisions

## SPS Results

-  NA50 observed anomalous J/psi suppression
-  NA60 results are consistent with NA50.

## Comparing RHIC to SPS Suppression results

-  Suppression pattern similar in RHIC and SPS.
-  CNM effect not removed yet.

-  After removing the CNM effect,  differences start to show-up.
- suppression at SPS consistent with the melting of psi’ and chi_c?
- Need more precise d+Au measurements

## Do we understand J/ results

- Satz - color screening in QGP with CNM added (EKS shadowing + 1 mb)
-  Capella – comovers with normal absorption and shadowing
-  Rapp – direct production with CNM effects (without regeneration)
** ****Models including both suppression and recombination match data better**
- R. Rapp(for _y=0_)  PRL 92, 212301 (2004)
- Thews  (for _y=0_)  Eur. Phys. J C43, 97 (2005)
-  Nu Xu *et al.*  (for _y=0_) nucl-th/0608010
-  Bratkovskaya *et al. *(for _y=0_)  PRC 69, 054903 (2004)
-  A. Andronic *et al.* (for _y=0_)  nucl-th/0611023
** ****All seems to be somewhat more consistent with the data. **
- Other sensitive comparisons are needed** **

- Do we understand J/**** results

## Golden Comparisons

- Charm flows. If recombination is correct, J/Psi should also flow.
- PHENIX expect to accomplish in run7 with higher luminosity (x3) and better (~sqrt(3.5)) reaction plane resolution.

- Charm suppression increase at higher pT. If recombination is correct, J/Psi suppression should quadratically increased at higher pT.
-  Not yet observed in PHENIX up to 5GeV.
- What the minimum pT to see the pattern?

- Single electron from open charm meson

- Single electron from open charm meson

## A New Hope:  Heavy quarkonia family 

- Powerful constraints on the medium properties once good measurements in Au+Au, d+Au and p+p are achieved.

## The Road Ahead

- constrained measurements
- measure charm, bottom directly
- precise measurements
- More luminosity.

## A bright near future at RHIC

| Signal | RHIC Exp. | Obtained | RHIC I (>2008) | RHIC II | LHC/ALICE+ |
| --- | --- | --- | --- | --- | --- |
| J/psi→e+e-
J/ps →m+m- | PHENIX |   ~800
~7000 | 3,300
29,000 | 45,000
395,000 | 9,500
740,000 |
|  → e+e- 
 → m+m- | STAR
PHENIX | -
- | 830
80 | 11,200
1,040 | 2,600
8,400  |
| B→J/psi→e+e-  
B→J/psi→m+m- 	 | PHENIX | -
- | 40
420 | 570
5,700 | N/A
N/A |
| cc→e+e- g 
cc→m+m- g	 | PHENIX | -
- | 220
8,600 | 2,900* 
117,000* | N/A
N/A |
| D→Kp | STAR | ~0.4×106 (S/B~1/600) | 30,000**       	 | 30,000**
 | 8000 |

- 12 weeks Au+Au run (**(****∫L****eff ****dt ~ 18 nb****-1****)**
**4 weeks of Pb+Pb at LHC.**
- *Large backgrounds, quality uncertain as yet
- ** Running at 100 Hz min bias

**(See Ed O’brien and Jim Thomas’s upgrade talks tomorrow)**

## and a bright future at LHC  

-  The matter created at RHIC and the one that will be created at LHC is expected to have different properties since the temperature at LHC will be much higher than at RHIC.

**(di-)muons: J/********, ********’, ********, ********’,********’’, open charm, open bottom**

**(di-)electrons: J/********, ********’, ********, ********’,********’’, open charm, open bottom**

**hadrons: exclusive D****0**

**electron-muon coincidences: open charm & bottom**

- From P. Crochet (RBRC heavy flavor workshop Nov. 2005)

## backup

## J/Psi v2 measurement projection

- Including the gain of a factor of 2 from HBD cut
- And gain from event mixing

## STAR J/ψ Signal

**J/********e****+****e****-**** Au+Au √s****NN****=200 GeV**

**J/********e****+****e****-**** p+p √s=200 GeV**

- STAR J/ψ Signal

- Signal in 200 GeV p+p from 2005
- Tested and working trigger in p+p
- No trigger for AuAu until full ToF in 2009
- Also signal in Au+Au with TPC only
-  Large hadron contamination
- Need full EMC

**STAR Preliminary**

**STAR Preliminary**

***Johann Gonzalez***

## Slide 30

## single electron with VTX

**Red     : Dalitz+Conversion**
**Green : Charm**
**Blue    : Beauty**

** ****Fraction of electron source            **

**p****T**

**no DCA cut**

**With DCA cut**

## Charm production at RHIC: spectra shape

- Is this shown only at high-pT?

## Integrated RAA vs. Npart

## Slide 34

## Charm cross section from STAR

- Use all possible signals
- D mesons
- Electrons
- Muons
- Charm cross section is well constrained
- 95% of the total cross section
- Direct measurement
- D-mesons and muons constrain the low-pT region

- Y. Zhang (STAR), Hard Probes 2006

## Add this to previous slides with the result to balance with STAR

- Subtraction of “photonic” sources.
- conversion of photons from hadron decays in material
- Dalitz decays of light  mesons  ()
- Converter method
- Comparison of e+/- spectra with and without converter allows separation of photonic and non-photonic sources of single electrons.
- measurement via -e coincidences
- Yield of -e in vicinity of  mass with mixed event subtraction

## 

Require  t0 >>2R/
 satisfied at RHIC but not sure about it at SPS.

- Require  t0 >>2R/
-  satisfied at RHIC but not sure about it at SPS.

- 22

- Bar: uncorrelated error
- Bracket : correlated error
**Global error = 12% and 7%**
**are not shown here.**
**Box : uncertainty from CNM effects**

- A Further comparison after removing the CNM effect

-  RHIC and SPS shows similar pattern in the same energy density region, i.e. <3.5GeV/fm^3, that is consistent with the melting of psi’ and chi_c.
-  RHIC data show more suppression at higher energy density
-  Still have Large error and mainly from run3 d+Au. Larger luminosity d+Au run is needed.

## J/y suppression vs. light hadrons

- Heavy flavor
- electrons

- J/

- 0

## Open Charm Measurement in forward region and CGC

*D.E. Kharzeev, K. Tuchin, hep-ph0310358*