# Presentation: 013339

## J/ψ production inPHENIX

- Raphaël Granier de Cassagnac
- LLR – École polytechnique / IN2P3
- For the PHENIX collaboration
- Hot Quarks 2006
- Villasinius, Sardinia, May 20th

**Notes:**
« I will report on the Jpsi production that has been observed by the phenix experiment. » 

## J/ψ in nucleus-nucleus(phenix preliminary = QM05)

**Notes:**
Nothing new on data since QM05
A bit more on their (non) interpretation

## RAA versus Ncoll

- Hugo Pereira da Costa, for PHENIX, QM05, nucl-ex/0510051

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th

**Notes:**
Versus Ncoll !

## Quick comparison to NA50

- Same magnitude
- 30% survival prob.
- No fundamental reason
- Differences:
- Higher energy density
- (x10 beam energies)
- Balance between cold & hot nuclear effects ?

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th

## J/ψ in deuteron-goldPRL96 (2006) 012304

## Cold nuclear matter effects

- Various “cold” effects:
- Shadowing      or anti-shadowing
- (gluon saturation, Color Glass Condensate...)
- Energy loss of initial parton
- pT broadening (Cronin effect)
- J/ψ (or cc ) absorption
- Something else ?

** ̄**

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th

**Notes:**
“ The goal is to disentangle normal nuclear effects. And indeed, you can think of many of them. First, you have to pick up partons in your projectiles, and thus you are sensitive to parton distribution functions in the nuclei, the so called antishadowing, shadowing and maybe you can even reach the gluon saturation region. Then, the initial partons can suffer energy loss or pt broadening. Finally, the produced Jpsi can be absorbed by the nuclear matter. 
The tool we use to investigate these effects is d+Au collisions, and we have to study them over the broadest range ot transverse momentum, rapidity and centrality we can achieve. And actually, this is the order I have chosen to present our results. 
There are to interests in doing this study. The first is to gather some information on the nuclear effect mechanism. The second is to serve as a baseline for Au+Au collision. Because hopefully, we’ll soon have to answer the burning question : why do Jpsi appear / disappear in Au+Au collisions.”

## Deuteron             Gold 

- In PHENIX, J/ψ mostly produced by gluon fusion, and thus sensitive to gluon pdf
- Three rapidity ranges probe different momentum fraction of Au partons
- South (y < -1.2) : large x2 (in gold)   ~ 0.090
- Central (y ~ 0) : intermediate x2        ~ 0.020
- North (y > 1.2) : small x2 (in gold)    ~ 0.003

- d

- Au

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th

**Notes:**
...
“ If we see a Jpsi at negative rapidity, it has to come from a high x in the gold. Indeed our average X in the south is 0.09. On the contrary, if we see a northern psi, is has to come from a low X in the gold, and our average is 3.10 ^ -3. The midrapidity measurement is around 0.02. Here is a example of theoretical prediction of shadowing. This is the ratio of the gluon pdf in a lead nucleon to the gluon pdf in a proton versus X. You can see that our forward measurement is sitting in shadowing-land, while the backward should see anti-shadowing. ”
Shadowing diffère d’un facteur trois entre modèles... 

## RdAu versus rapidity

- RdA

- RdAu versus rapidity

- Data favours
- (weak) shadowing
- Eskola, Kolhinen, Salgado
- prescription matches better
- (weak) absorption
- σabs ~ 1 to 3 mb
- (4.18 ± 0.35 mb @SPS)
- But with limited statistics difficult to disentangle nuclear effects !

- PHENIX, PRL96 (2006) 012304
- Klein,Vogt, PRL91 (2003) 142301
- Kopeliovich, NPA696 (2001) 669

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th

**Notes:**
Define RdAu !
Drop is energy loss ! (Mike’s cartoon)
3 millions of Jpsi !
Let’s take a closer look to the comparison with lower energy...

1) COHERENCE PHENOMENA IN CHARMONIUM PRODUCTION OFF NUCLEI AT THE ENERGIES OF RHIC AND LHC.By Boris Kopeliovich, Alexander Tarasov (Heidelberg, Max Planck Inst. & Regensburg U. & Dubna, JINR), Jorg Hufner (Heidelberg, Max Planck Inst. & Heidelberg U.),. Apr 2001. 50pp. Published in Nucl.Phys.A696:669-714,2001 e-Print Archive: hep-ph/0104256 

## Black lines:
EKS98 from 0 to 3 mb
Colored lines:
FGS for 3 mb
Slopes consistent with shadowing models 
Especially low x2 

- Black lines:
- EKS98 from 0 to 3 mb
- Colored lines:
- FGS for 3 mb
- Slopes consistent with shadowing models
- Especially low x2

**High x****2**** ~ 0.09**

**Low x****2**** ~ 0.003**

- RdA

- RdAu versus Ncoll

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th

**Notes:**
...
“ in fact, it almost look as a soft process ” ?

## Cold nuclear matter effects

- Shadowing + nuclear absorption (crucial !)

- PHENIX, QM05, nucl-ex/0510051
- Vogt, nucl-th/0507027

- Error bar code : bars = statistical,
- bracket = systematic, box : global.

- 1.2 < |y| < 2.2

-  -0.35 < y < 0.35

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th

**Notes:**
Back to AuAu !
Error bar code : bars = statistical, bracket = systematic, box : global.
Notice the difference between forward and mid rapidities !

## “NA50 only” effects

- Capella, Ferreiro, EPJC42 (2005) 419
- Grandchamp et al, PRL92 (2004) 212301
- Kotstyuk et al, PRC68 (2003) 041902
-  Digal, Fortuno, Satz, EPJC32 (2004) 547
- 	       + Private communications +

- Cold effects + ...
- Comovers (hadrons/partons?)
- Kinetic model (J/ψ  c c )
- Thermal plasma
- All overestimate suppression !
- So does parton percolation
- Onset at Npart ~ 90
- Simultaneous J/ψ + χc + ψ’

- (AuAu only)

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th

**Notes:**
“ First, let’s give a chance to the models that did a good job in explaining the NA50 data. Here, I pick up the AuAu data only, at both rapidities... ”
“ If you wonder what percolation means, it is when partons overlap in space and recombine ”
Grandchamp Phys.Rev.Lett.92:212301,2004 
Capella Eur.Phys.J.C42:419-424,2005 
Kotstyuk Phys.Rev.C68:041902,2003 
Digal, Fortunato & Satz. Eur.Phys.J.C32:547-553,2004 
(j’ai tous les pdf)

## RHIC “new” effects

- 1st. Variety of recombination & coalescence models
- c c  J/ψ (at freeze-out)
- goes as Ncc2 (poorly known)
- (other models not displayed)
- 2nd. One detailed QGP hydro + J/ψ transport (Zhu et al)
- 	(here without cold nuclear effects, see later...)
- Look at y, pT...

- Grandchamp et al, PRL92 (2004) 212301
- Bratkoskaya et al, PRC69 (2004) 054903
- Andronic et al, PLB571 (2003) 36
- Zhu, Zhuang, Xu, PLB607 (2005) 107
-                       + Private communications +

- (AuAu only)

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th

**Notes:**
+ régénération
Zhu Phys.Lett.B607:107-114,2005
Bratkoskaya Phys.Rev.C69:054903,2004 
Andronic Phys.Lett.B571:36-44,2003 
Hadron string dynamics
+ statistical coalescence
+ statistical hadronization

## y shape (vs recombination)

- Recombination emphasizes quark y-distribution
- Quark (open charm)         y-distribution unknown
- No significant change in rapidity in data...

- Recombined only !

-  Thews & Mangano, PRC73 (2006) 014904c

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th

**Notes:**
Thews, Phys.Rev.C73:014904,2006 

## <pT2> (vs Cronin effect)

- <pT2> (vs Cronin effect)

- <pT2>AA = <pT2>pp +   pT2 x L [nuclear matter thickness]
- (random walk of initial gluons)
-   pT2 from pp and dA 
- L <-> Ncoll conversion
- Negligible broadening @ y=0 !?...
- 	(open symbols)

- VN Tram, Moriond 2006 & PhD thesis

- p+p d+Au       Au+Au

- (lower energy survey)

- Open symbol: y ~ 0
- Full & Curve: y ~ 2

- <pT2> = 2.51 + 0.32 L

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th

## 2nd. Zhu et al (updated)

- 2nd. Zhu et al (updated)

- Zhu, Zhuang, Xu,
- PLB607 (2005) 107
- + private communication

- + Nuclear absorption (1 or 3 mb)
- + Cronin effect from our dAu

- (dominated by Cronin
- determined on dA data)

- Predicted RAA (y=0) ~ (y=2)

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th

**Notes:**
Y=0 is very close !

## 3rd (simple) explanation

- 3rd (simple) explanation

- Amount of anomalous suppression depends on cold nuclear effects amplitude
- But could as low as 30 to 40%
- Compatible to feed-down ratio
- J/ψ ~ 0.6 J/ψ + 0.3 χc + 0.1 ψ’
- Recent lattice Tdψ ~ 1.5 - 2.5 Tc
- ε x (TdJ/ψ ~ 2Tc)4 = 2 εc εdJ/ψ ~ 32 εc !
- Wait for LHC ?

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th

## Conclusions (1)

- For now, 3 models to “explain” the data:
- 1st Recombination ?
- But no sign of y or pT2 modifications...
- J/ψ  (Ncc)2   (but how much is Ncc ?)
- 2nd J/ψ detailed transport in hydro QGP
- 3rd Sequential melting ?
- J/ψ may still survive @ RHIC...
- All assume a QGP...

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th

## Conclusions (2)

- What do we need to answer ?
- Final AA analysis
- A bit more data & more bins !
- With a better pp ref (run 5)
- With J/ψ elliptic flow ? 
- More dA ! Better handle cold nuclear effects...
- More AA ! With open charm, ψ’,...
- First look at ψ’ and upsilons
- Going on with run 5 pp...
- Better open charm measurements
- Si VTX upgrade 
- LHC !

- Zhu, Zhuang, Xu, PLB607 (2005) 107

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th

**Notes:**
17 bins en CuCu
?? en AuAu !
“ In case of coalescence, the J/psi should inherit the flow of charm quarks ” (+ un plot pour HP06)

##  13 Countries;  62 Institutions;  550 Participants*

*** ******13 Countries;  62 Institutions;  550 *****Participants*********

***as of March 2005**

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th

## Back up slides

## Quick look at NA60

- In In-In collisions, preliminary plateau also rules out percolation, comovers and available plasma

-  Percolation
-  Plasma
-  Comovers

- NA60 preliminary

- Roberta Arnaldi, QM05

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th

## 3rd Sequential melting

- Sequential melting
- J/ψ survival only
- Cold nuclear matter effects derived from dAu data for RHIC
- Axis cannot be energy density since same 0 (1fm/c) is assume for SPS and RHIC !
- Larger at SPS
- Smaller at RHIC

- Karsch, Kharzeev & Satz hep-ph/0512239

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th

## Quick look to open charm

- Through semileptonic decays (D  e)

- PHENIX, PRL94 (2005) 082301

- ~25% systematic uncertainties
- (without Silicon vertex
- detector upgrade)

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th

**Notes:**
14 paires dans les événements les plus centraux !

## Charm quench & flow

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th

## Na50/Phenix comparisons

- NA50 expected 4.18mb

- PHENIX expected

- 1mb

- 3mb

- PHENIX expected

- 1mb

- NA50 expected 4.18 mb

- 3mb

- Consistent suppression amplitude observed
- but cold nuclear effects may be different

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th

**Notes:**
Le problème de ces plots, c’est qu’il n’y a pas les points à mi rapidité... 

## measured/expected vs Bj

- Below unity !
- Suppression amplitude consistent within error bars

- abs = 1 mb

- abs = 3 mb

- (x 0) !

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th

## measured/expected vs Npart

- Under unity
- Larger difference when 1mb but compatible within error bars

- abs = 1 mb

- abs = 3 mb

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th

## recombination/suppression

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th

## pT spectra

- In pp:
- <pT2> = 2.5 GeV 2
- In AuAu & CuCu:
- <pT2> = 3  5.3 GeV 2

- Au+Au (|y|[1.2,2.2])

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th

## <pT2> (vs recombination)

- <pT2> (vs recombination)

- Robert Thews, SQM06

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th

## <pT2> (vs recombination)

- Cu+Cu

- Au+Au

- 100% pQCD + kT

- 100% recombined

- Seems to favor recombination scenario
- But Cronin effect not under control...

- Lines from Thews & Mangano, PRC73 (2006) 014904

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th

**Notes:**
Attention ! Y a un bug sur le plot AuAu...

## Cronin effect

-  nuclear density,  elastic gluon-nucleon scattering cross section, (<pt2>)
- kick given by each scattering and L average thickness of nuclear matter

*√* s =17.3 GeV : NA50/60  Pb+Pb, In+In
*√* s = 19.4 GeV : NA3 p+p, NA38 p+Cu, p+U,O+U, S+U
*√* s = 27.4 GeV : NA50 p+Be, p+Al, p+Cu, p+W
*√* s = 29.1 GeV :NA51 p+p, p+d, NA50 p+Al, p+W
*√* s = 38.8 GeV : E866/789/771

- Scattering of initial gluons of nucleon before ccbar formation random walk : <pt2>AA = <pt2>pp + (<pt2>) LAA

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th

## Cronin effect

- Cronin : <pt2>AA = <pt2>pp + (<pt2>) LAA

- Extrapolation curve from PHENIX J/ψ results  in p+p and d+Au

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th

## Cronin effect

- At forward rapidity, <pt2> variation compatible with this Cronin extrapolation
- At mid rapidity, measurements in p+p and d+Au indicate a weak Cronin effect

- Cronin : <pt2>AA = <pt2>pp + (<pt2>) LAA
- Extrapolation curve from PHENIX J/ψ results  in p+p and d+Au

- p+p d+Au Au+Au

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th

## A busy plot about <pT2>

- ( curves to be compared with AA @ 1.2<|y|<2.2 )

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th

## Rapidity width

- No noticeable change in rapidity width

- Width pp =  1.75  0.21

- VN Tram thesis

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th

## More on transport model...

- 2+1D hydro
- Boltzman-type transport
- Local equilibrium
- (0.8 & 0.6 fm/c)
- Normal to anomalous
- Tc = 165 MeV
- Tfo = 60 MeV
- g+Ψ  cc
- 40% feeddown
- No in-medium mod.
- No absorption @RHIC (here)

- Zhu, Zhuang, Xu,
- PLB607 (2005) 107

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th

## How does   PHENIX see the J/ψ ?

- How does   PHENIX see the J/ψ ?

- J/ψ  e+e– identified in RICH and EMCal
- || < 0.35
- pe > 0.2 GeV
- J/ψ  μ+μ–
- identified in 2 fwd spectrometers
- 1.2 < || < 2.4
- pμ > 2 GeV
- Centrality and vertex given by
- BBC in 3<||<3.9
- and ZDC

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th

**Notes:**
“ First, let me explain how phenix is looking for Jpsi’s. At mid-rapidity, we have a cerenkov and an electromagnetic calorimeter which allow us to identify electrons and thus reconstruct the dielectron decay of the psi’s. At higher rapidities, we can look for Jpsi’s decayng to two muons, in a backward [click] and a forward spectrometer. The last apparatus we use in this analysis is the beam beam counter which provide a centrality and a vertex measurement. ”

## J/ψ in PHENIX

| Year | Ions | sNN | Luminosity | Status | J/ (ee + μμ) |
| --- | --- | --- | --- | --- | --- |
| 2000 | Au-Au | 130 GeV | 1 b-1 | Central (electrons) | 0 |
| 2001 | Au-Au | 200 GeV | 24 b-1 | Central | 13 + 0 [1] |
| 2002 | p-p | 200 GeV | 0.15 pb-1 | + 1 muon arm | 46 + 66 [2] |
| 2002 | d-Au | 200 GeV | 2.74 nb-1 | Central | 360 + 1660 [3] |
| 2003 | p-p | 200 GeV | 0.35 pb-1 | + 2 muon arms | 130 + 450 [3] |
|  | Au-Au | 200 GeV | 240 b-1 | preliminary | ~ 1000 + 5000 [4] |
| 2004 | Au-Au | 63 GeV | 9.1 b-1 | analysis | ~ 13 |
|  | p-p | 200 GeV | 324 nb-1 |  |  |
|  | Cu-Cu | 200 GeV | 4.8 nb-1 | preliminary | ~ 1000 + 10000 [4] |
| 2005 | Cu-Cu | 63 GeV | 190 mb-1 | analysis | ~ 10 + 200 |
|  | p-p | 200 GeV | 3.8 pb-1 |  | ~ 1500 + 10000 |
| 2006 | p-p | 200 GeV | ?? | Running... | ?? |

- [1] _[PRL92 (2004) 051802](http://xxx.lanl.gov/hep-ex/0307019)_
- [2] _[PRC69 (2004) 014901](http://xxx.lanl.gov/nucl-ex/0305030)_
- [3] _[PRL96 (2006) 012304](http://arxiv.org/abs/nucl-ex/0507032)_
- [4] QM05, _[nucl-ex/0510051](http://arxiv.org/pdf/nucl-ex/0510051)_

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th

**Notes:**
“ This table reflect the short history of rhic. [rhic] All data I’m going to show are from the run 3. For the first time, we had the three spectrometers operational. And together with the delivered luminosities, this allowed us to collect a couple thousands Jpsi’s. Let me also mention that all the results we will debate are preliminary ”
[erreur de couleur]
Run5pp d’après talk Wei & note Mike

## First upsilons...

- Run 5 pp (3 pb-1)

- Hie Wei, Quark Matter 2005

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th

## Centrality analysis

- Au breaks up in our south beam counter
- Define 4 centrality classes
- Relate centrality to <Ncoll>
- through Glauber computation
- <Ncoll> = 8.4 ± 0.7

**<N****coll****> = 3.2 ± 0.3**

**<N****coll****> = 15.0 ± 1.0**

- South BBC Charge

- Central

- Peripheral

- Counts

- MB

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th

## Centrality analysis

- BBC charge versus ZDC energy

- Most central
- 0 - 5 %
- < Npart > = 351 ± 2.9
- < Ncoll > = 1065 ± 105

- Most peripheral
- 80 – 92.2%
- < Npart > = 6.3 ± 1.2
- < Ncoll > = 4.9 ± 1.2

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th

## Cross section versus pT

- Cross section versus pT

- Some pT broadening

- PHENIX, PRL96 (2006) 012304

- <pT2> =  <pT2>dAu – <pT2>pp
-  Backward: 1.77 ± 0.37 GeV 2
- Mid: (-1.28 ± 0.94 GeV 2 )
- Forward: 1.12 ± 0.35 GeV 2

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th

**Notes:**
Draw the electron points on the same graphs as muons !
pp dielectron point is close to old pp dimuon point...
Clear that this are muons !!!

## RdAu versus pT

- RdAu versus pT

**Low x****2**

**High x****2**

- Broadening comparable to lower energy       (s = 39 GeV in E866)

- RdA

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th

## d+Au perspectives

- We have seen small nuclear effects !
- Weak shadowing / antishadowing
- Weak absorption (~ 1 to 3 mb)
- pT broadening similar to lower energies
- Difficult to disentangle given statistics
- Need more luminosity !
- But, no large nuclear effect !
- Good news to see J/ψ suppression in Au-Au !

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th

## J/ψ in proton-proton

## Cross section vs rapidity

- Total cross section
-  (pp  J/ψ)
- 2.61 ± 0.20 ± 0.26 μb
- Error from fit      (incl. syst and stat)
- Error on absolute normalization

- PHENIX, PRL96 (2006) 012304

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th

**Notes:**
RUN2 = 234 +/- 36 +/- 34 +/- 24 ! 1.3 sigma appart
« Measure both rapidity »

## Cross section versus pT

- Fit the function
- <pT2> = 2.51 ± 0.21
- ( GeV2 )

- PHENIX, PRL96 (2006) 012304

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th

**Notes:**
Draw the electron points on the same graphs as muons !
pp dielectron point is close to old pp dimuon point...
Clear that this are muons !!!

## p+p perspectives

- Production mechanism
- Color Octet Model does the job
- In AA (or dA)
- Large combinatorial background
- Low physics background
- (Drell-Yan or dileptons from open charm)
- p+p is our baseline
- Nuclear modification factor
- Run5 pp analysis going on
- > 10 times statistics

- PRL96, 012304 (2006)

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th

## NA50 versus NA60 (QM05)

- No overlap...

- Good agreement !

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th

## Dielectron pp and dA

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th

##  versus X compared to lower s

-  versus X compared to lower s

- Not universal versus X2 : shadowing is not the whole story.
- Same versus XF for diff s. Incident parton energy loss ? (high Xd = high XF)
- Energy loss expected to be weak at RHIC energy.

- X2 (in gold)

- E866, PRL 84, (2000) 3256 NA3, ZP C20, (1983) 101
- PHENIX, PRL96 (2006) 012304

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th

**Notes:**
Définir X_F et X_2 !!! Initial state energy loss !!!

## How to get xF scaling ?

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th

## J/ψ transverse momentum (run2)

- Phenomenological + exponential fits of dimuon and dielectron data give mean pT :
- 	<pT>  = 1.80 ± 0.23 (stat) ± 0.16 (sys) GeV/c

- Color Singlet Model
- Color Octet Model
- (from Nayak et al.
- hep/ph 0302095)
- COM contribution is
- dominant, as for high
- pT J/ @ Tevatron

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th

**Notes:**
Phenomenological : 1/(2 pi pt) dsigma/dpt = 1 (1+(pt/B)^2)^(-6)

## J/ cross section from run 2

- J/ cross section from run 2

- Integrated cross-section :
- RUN2  234 ± 36 (stat) ± 34 (sys) ± 24(abs) μb
- RUN3  159 nb ± 8.5 % (fit) ± 12.3% (abs)

**e****+****e****–**

******+********–**

- Results consistent
- with shapes from
- various models and
- PDF.
- Take the PYTHIA
- shape to extract
- our cross-section

- Error from absolute
- normalization

- Consistent
- (1.3 sigma
- difference)

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th

## Naive picture

- Less absorption
- Shadowing
- Energy loss

- (Kopeliovich)

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th

## Tuchin & Kharzeev 

- Hard probes 2004
- _hep-ph/0504133_
- Coherent production of charm (open or closed)
- (y<0 production time to low to make computation)
- Shadowing from CGC computation...

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th

## Tuchin & Kharzeev...

- + absorption for
- SPS & fermilab

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th

## ... gold+gold extrapolation ...

- J/ψ in PHENIX - raphael@in2p3.fr

- HQ2006, May 20th