# Presentation: 820421

## J/ from dAu (nuclear effects)

- Raphaël Granier de Cassagnac*
- Santa Fe Muon Fest
- 21st June 2004

- * David Silvermyr
- enjoying the soccer
- cup in Europe

- Raphaël - Santa Fe Muon Fest - J/psi in dAu

- 21st June 2004

## Physics motivations for dAu

- Get the reference for Au+Au collisions (and QGP)
- Disentangle various “ cold ” nuclear effects
- In nuclei modification of parton distribution functions
- Antishadowing & Shadowing (gluon saturation ? Color Glass Cond ?)
- Energy loss of initial partons
- Can kill the J/ !
- Multiple scattering of initial partons
- pT broadening (Cronin effect)
- J/ absorption
- Or other final state effects ?...
- The tools :
- Look over broad ranges of pT, rapidity, centrality...

- Raphaël - Santa Fe Muon Fest - J/psi in dAu

- 21st June 2004

## Outline

- Some technicalities about our dAu run
- Quark Matter 2004 reminder
- The preliminary result
- A word about interpretations
- Expectation for Au-Au
- Progress towards the final result
- A kind of report from the PPG038

- Raphaël - Santa Fe Muon Fest - J/psi in dAu

- 21st June 2004

## 1. Our dAu run (online)

- Luminosity : 2.74 nb–1
- Trigger : LVL1 trigger with
- Half with 1Deep 1Shallow
- (eq. to 1.57 south and 1.71 north MinBias Gevents)
- Half with 2Deeps
- (eq. to 1.18 south and 1.55 north MinBias Gevents)
- (recabling of LVL1 trigger wrt run 2 : deep means 4th gap* – back to nominal for run 4)

- * Starting to count at 1

- Raphaël - Santa Fe Muon Fest - J/psi in dAu

- 21st June 2004

## Our dAu run (offline)

- Reconstruction code first looked for muon reaching the 3rd gap* (thus missing some triggered 1D1S events)
- So is pro43 (CCF) thus the QM04 result
- So was the later “official” pro45 (RCF)
- ( MUTOO was running successfully without MuId matching allowing to notice this “mistake” )
- Fixed for pro48 (dAu) and pro50 (pp) CCF production (being used for final result)

- * Starting to count at 1

- Raphaël - Santa Fe Muon Fest - J/psi in dAu

- 21st June 2004

**Notes:**
Mistake -> oubli...

## 2. QM04 reminders

- See the analysis note 255 for +–
- See the analysis note 258 for e+e–
- QM04 proceedings nucl-ex/0403030

-  analysis done on
- 600 + 800 J/ from dAu
- 120 + 300 J/ from pp
- (south + north)
- ee analysis done on
- 300 J/ from dAu
- 100 J/ from pp

- Raphaël - Santa Fe Muon Fest - J/psi in dAu

- 21st June 2004

**Notes:**
Un slide sur l’analyse ??? 

## pT broadening in dAu

- High x2
- ~ 0.09

- Low x2
- ~ 0.003

- pT broadening in dAu

- <pT2> =
- <pT2>dAu – <pT2>pp
- 1.77 ± 0.35 GeV2
- 1.29 ± 0.35 GeV2
- (preliminary)

- Raphaël - Santa Fe Muon Fest - J/psi in dAu

- 21st June 2004

## dAu/pp versus pT

- dAu/pp versus pT

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

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

- “broadening” comparable to lower energies  (s = 39 GeV in E866)

**Low x****2**

**High x****2**

- Raphaël - Santa Fe Muon Fest - J/psi in dAu

- 21st June 2004

**Notes:**
Skip !

## dAu/pp vs rapidity

-  Data favour (some) shadowing +  (weak) absorption ( > 0.92)
- With limited statistics difficult to disentangle nuclear effects

- Backward
- High X2 ~ 0.09
- Antishadowing
- expected

- Forward
- Low X2 ~ 0.003
- Shadowing
- expected

- Raphaël - Santa Fe Muon Fest - J/psi in dAu

- 21st June 2004

##  compared to lower s

- XF = Xd - XAu

-  compared to lower s

- X2 (in gold)

- E866: PRL 84, 3256 (2000)NA3: ZP C20, 101 (1983)

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

- Rapidity

- Raphaël - Santa Fe Muon Fest - J/psi in dAu

- 21st June 2004

**Notes:**
Skip this one ???

## Central/peripheral vs Ncoll

- Low variations at low et mid x2 :
- Weak net nuclear effects
- Small shadowing centrality dependence...
- At High x2 surprising steep rising shape with centrality !
- Can antishadowing be that violent ?

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

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

- RCP

- Raphaël - Santa Fe Muon Fest - J/psi in dAu

- 21st June 2004

**Notes:**
Skip eventually

## dAu / pp vs Ncoll

- dAu / pp vs Ncoll

- Low x2 consistant with inhomogeneous shadowing...
- High x2 steeper than corresponding antishadowing !
- What can it be ?
- Something about being closer to the gold rest frame ?
- No clear understanding yet...
- Theorists at work...

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

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

- RdA

- Raphaël - Santa Fe Muon Fest - J/psi in dAu

- 21st June 2004

**Notes:**
Rajouter la référence ?

## 3. A word about interpretations

- The steep rising shape makes the J/ look like lighter hadrons... No fundamental reasons for that...
- Different processes (gluon fusion for J/, still q+g for hadrons)
- Different pT ranges ! (J/ = all pT)
- Hard versus soft ??? (create the J/ mass first)

- Open charm could help !
- No J/ effects...
- See tomorrow’s talks !
- (Ming, Chun, Ken, Kazuya...)
- Some theorists at work
- (Kharzeev & Tuchin, Kopeliovich, Thews...) not published yet

- Hadron RCP [0-20%]

- Raphaël - Santa Fe Muon Fest - J/psi in dAu

- 21st June 2004

**Notes:**
Check Ming !!! And others... Mike’s plot instead.

## 4. Expectation for Au-Au

- backward x forward rapidity
- With data points
- With arbitrary scaled theoretical curves
- As much as a factor of 2 suppression due to... shadowing ?
- (for Hugo’s talk today, for MinJung, ViNham and ? theses tomorrow)

- Raphaël - Santa Fe Muon Fest - J/psi in dAu

- 21st June 2004

## 5. Progress towards final results

- PPG038 is formed
- Title : “ *J/Psi Production and Nuclear Effects for d+Au and p+p Collisions at RHIC*  ”
- Intended : Physical Review Letters
- Chair : Mike Leitch
- Members : Yasuyuki Akiba, Jane Burward-Hoy, Raphael Granier de Cassagnac, Soichiro Kametani, DongJo Kim, Sasha Lebedev, David Silvermyr, Wei Xie.
- other contributors working as well...

- Raphaël - Santa Fe Muon Fest - J/psi in dAu

- 21st June 2004

## Dominant  uncertainties

- Typical statistical errors are (splitting in 2 rapidity bins)
- ~ 7% from dAu
- ~ 13% from pp
- (merged S+N)

- Should improve !
-  Higher efficiency with shallower roadfinding
-  Better under-standing of MuTr efficiencies (Xiaorong’s work)

- (from AN255)

- Raphaël - Santa Fe Muon Fest - J/psi in dAu

- 21st June 2004

**Notes:**
Refine – Trouver l’info de Xiaorong...

## Where are we trying to gain ?

- Need more pp statistics !
- (for RdA, pp yields and cross sections...)
- What can we hope from run 4 ?
- Need more dAu statistics !
- (mostly for Rcp)
- Need to work on background subtraction !
- Combinatorial background (reduce stat. error)
- Physical background (for dAu yields, Rcp...)
- Detector inefficiencies knowledge may stay as the dominant systematics...

- Raphaël - Santa Fe Muon Fest - J/psi in dAu

- 21st June 2004

**Notes:**
Fast !

## Getting more (shallower) muons

- More J/ but more comb. background
- Is it worth it ?
- Look at the signal/background ratio
- or _rough_ estimate of error :

- Staying with QM04
- “standard cuts”

- Raphaël - Santa Fe Muon Fest - J/psi in dAu

- 21st June 2004

## Adding cuts to optimize S/B

- New cuts to get better S/B
- For instance :
- Mimic offline the trigger condition (1D1S or 2D)
- DG0 maximum
- 15 for north arm
- 30 for south arm
- DS3ctp maximum
- 15 for north arm
- 25 for south arm
- (study done by Ermias Tujuba an undergrad student at LLR)

- It is decided to work with the shallower roads.
- Cuts may be further defined.

- Raphaël - Santa Fe Muon Fest - J/psi in dAu

- 21st June 2004

## A useless statistical error...

- Part of our error is due to comb. bg. through : #J/**** = (+-) – 2 √(++)(--)
- Carries a _statistical_ error
- Using rough formula and
- previous cuts, we can hope :
- And thus hope a gain a bit everywhere
- (yields, RdA, Rcp)

- Raphaël - Santa Fe Muon Fest - J/psi in dAu

- 21st June 2004

## To get rid of the comb. errors

- Various ideas (from the easier to the tougher)
- Redistribute the bg events of a bin in the nearby bins (acc. to gaussian) (Mike)
- Reduce fluctuations but shouldn’t change errors
- Fit the (++) and (--) (Fred/Ermias)
- Reduce fluctuations and errors
- Difficult to fit small samples (high pT)
- Mixing events ! (Fred)
- Should _eradicate_ errors and fluctuations

- Raphaël - Santa Fe Muon Fest - J/psi in dAu

- 21st June 2004

## As an example of the progress... 

- The 4 methods on one centrality bin of the dAu north 2 deeps sample.

- (thanks to Fred and
- Andry, his PhD student)

- 2 √(N++.N––)

- + Gaussian smearing

- + fitted exponentials

- Mixed
- events

- Remarks :
-  1 and 2 can be used together...
-  What are the systematics assoc. to each methods ?
-  Will be probably interesting for AuAu too...

- Raphaël - Santa Fe Muon Fest - J/psi in dAu

- 21st June 2004

## Need to work on physical bg too

- Syst error = allow any value between no background (exp) and twice the measured background with (exp+gauss)
- Check that various shapes give consistent results...
- Can we assume a smaller uncertainty ?
- Need more knowledge about open charm and DY...

- Open charm

- Drell-Yan, open beauty ?

- See Sebastien’s
- this afternoon

- Raphaël - Santa Fe Muon Fest - J/psi in dAu

- 21st June 2004

**Notes:**

Prendre quelque chose dans une présentation de David...

## Need to work on physical bg

- Maybe, one day, we’ll be able to use this kind of fit...
- (with a low systematic error associated)

- Raphaël - Santa Fe Muon Fest - J/psi in dAu

- 21st June 2004

## To be done...

- More doubling of the analysis wrt QM04
- Mike + DongJo’s efficiencies
- Raphael & Ermias efficiencies
- Cuts, background techniques may vary between us for crosscheck.
- We’re a bit late... Finalization should occur during July...

- Raphaël - Santa Fe Muon Fest - J/psi in dAu

- 21st June 2004

## Insight on new plots (work in progress)

- Raphaël - Santa Fe Muon Fest - J/psi in dAu

- 21st June 2004

## Conclusions

- We have seen (small) nuclear effects !
- Some shadowing
- Smaller absorption than expected ( > 0.92)
- pT broadening similar to lower energies
- Something above antishadowing ?
- Rising RdA versus centrality at high x2   (y < -1.2)
- Reanalysis is in progress... More news in July
- Hope for a slightly lower uncertainties
- Still difficult to disentangle the effects
- The relevance do Au-Au comparison will depend on the magnitude of Au-Au effect !
- We still need more luminosity !

- Raphaël - Santa Fe Muon Fest - J/psi in dAu

- 21st June 2004

## Back up slides

- Raphaël - Santa Fe Muon Fest - J/psi in dAu

- 21st June 2004

## Deuteron               Gold 

- In PHENIX, J/ 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

- From Eskola, Kolhinen, Vogt
- Nucl. Phys. A696 (2001) 729-746.

- _Example of predicted gluon shadowing in d+Au_

- gluons in Pb / gluons in p

- X

- Anti
- Shadowing

- Shadowing

- Raphaël - Santa Fe Muon Fest - J/psi in dAu

- 21st June 2004

**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. ”

## Systematics due to physical bg

- Raphaël - Santa Fe Muon Fest - J/psi in dAu

- 21st June 2004

## Centrality in d+Au

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

**<N****coll****> = 3.2 ± 0.3**

**<N****coll****> = 15.0 ± 1.0**

- South BBC Charge

- Central

- Peripheral

- Counts

- MB

- Raphaël - Santa Fe Muon Fest - J/psi in dAu

- 21st June 2004

## Number of MB events

- Raphaël - Santa Fe Muon Fest - J/psi in dAu

- 21st June 2004