# Presentation: 637981

## Cold nuclear matter effectson heavy flavours(a review)

- 2008, October 8th
- Tsinghua, Beijing, China
- Strange Quark Matter 2008
- Raphaël Granier de Cassagnac
- LLR – École polytechnique / IN2P3

## Disclaimer

*Before to claim for anomalous suppression, one has to check for normal suppression*
*Cold nuclear effects on heavy flavours are so important to understand J/ψ in AA collisions... *
*...**that most of my talk was covered by Alex, Taku and others yesterday!*
*Thus, you could have slept half an hour more...*
*But let me try to wake you up... *

- 2008, October 8th

- Cold effects on heavy flavours - raphael@in2p3.fr

## Some semantics: my definition of cold

- 2008, October 8th

- Cold effects on heavy flavours - raphael@in2p3.fr

- Parton Shadowing

- Parton saturation
- (Color Glass Condensate)

- Nuclear
- absorption

- Cronin effect

- Energy loss

- Color screening
- Sequential suppression

- Quark recombination
- or coalescence

- Comovers
- Partonic / Hadronic ?

- EMC effect

- Parton Antishadowing

- Intrinsic
- charm

## Outline: go through experimental programs and observed cold effects

- @SPS (20 GeV): _many pA_ ! High statistics ! But small kinematics      (–0.1 < xF < +0.1)  Nuclear absorption
- @FNAL, HERA (30 GeV): less pA... High statistics ! Large rapidity (xF) coverage...  Many cold nuclear effects needed! _But no AA_...
- @RHIC (200 GeV): only dAu, low statistics (for now), but
- Rapidity (–2.2 to +2.4)  Absorption + (anti)shadowing
- _Centrality dependence_  Data driven method
- Open charm, with large uncertainties
- Bonus: a word about Cronin effect
- @LHC (5.5 TeV): likely to be as RHIC, only dPb to start with, large rapidity coverage (three experiments)...  Uncharted territory

- 2008, October 8th

- Cold effects on heavy flavours - raphael@in2p3.fr

**Notes:**
@HERAB: similar, negative xF (–0.35 to +0.15)

## SPS charmonia & nuclear length L

- Introducing nuclear absorption σabs
*“**One parameter to fit them all*
*And out of nuclei to unbind them”*

## J/ψ / Drell-Yan versus L 

- _Normal nuclear absorption alone_ does a splendid job describing pA, SU and peripheral InIn and PbPb:
- exp (-σabs ρ° L)
- (or more sophisticated Glauber approach)
- L = nuclear thickness
- Collisions subsequent to J/ψ formation
- σabs = 4.18 ± 0.35 mb

- 2008, October 8th

- Cold effects on heavy flavours - raphael@in2p3.fr

- σabs = 4.18 ± 0.35 mb

- NA50, EPJ C39 (2005) 335
- NA60, PRL99 (2007) 132302

## BTW, cold effects on Drell-Yan @ SPS?

**AxB scaling in various systems**

**Pb+Pb Ncoll scaling**

- 2008, October 8th

- Cold effects on heavy flavours - raphael@in2p3.fr

- NA50, e.g. QM2002
- NA50, PLB450 (1999) 456

- Drell-Yan
- Minimum bias

- Data

- Glauber

- pp pd      pA                   SU PbPb

- Neither cold nor hot modifications
- Quark (anti)shadowing must be small
- It is a good reference for charmonia

## What about the ψ’ ?

- ψ’ are more absorbed than J/ψ

- 2008, October 8th

- Cold effects on heavy flavours - raphael@in2p3.fr

- ψ’

- J/ψ

- NA50, EPJC48 (2006) 329
- NA50, EPJC49 (2007) 559

- ψ’/Drell-Yan

- σabs = 4.2 ± 0.5 mb

- σabs = 7.7 ± 0.9 mb

- 7.7 ± 0.9 mb

- ψpA / A

## E866 and xF

*Broadening your interest *
*gets you into trouble*

## J/ψ, ψ’, D mesons

- At midrapidity (xF=0):
- D meson unmodified (within 10% accuracy)
-  Little (gluon) shadowing
- Again ψ’ more absorbed
- Larger coverage reveals new effects...

- 2008, October 8th

- Cold effects on heavy flavours - raphael@in2p3.fr

- σpA = σpp x A****

- E789, PRL72 (1994) 2542
- E866/NuSea, PRL84 (2000) 3256

- xF = xp – xA

**Notes:**
According to Ramona, CEM, 80-90% from gluon fusion at midrapidity, but qqbar dominates at high xF... 

## Examples of how to fit the whole xF range

- 2008, October 8th

- Cold effects on heavy flavours - raphael@in2p3.fr

- Vogt, PRC61 (2000) 035203
- Kopeliovitch et al, NPA696 (2001) 669
- Courtesy to Mike Leitch

**Energy loss** of incident parton shifts effective xF
- and produces nuclear suppression which
- increases with xF

- Many effects, complicated story
- Not very relevant for AA studies...

## Other experiments and quarkonia

**E772: Upsilon less suppressed **
**Less shadowing & absorption?**

**HERA B = wealth of J/****ψ****, ****ψ****’ and ****χ****c**** to negative x****F**
**J/****ψ ****f****rom ****χ****c ****: 18.8 ± 1.3 ± 2.4 %**

- 2008, October 8th

- Cold effects on heavy flavours - raphael@in2p3.fr

- HERA B, arXiv:0807.2167

## Is σabs varying with √sNN?

- Theoretical arguments that it should decrease with √s
- σabs= 0 @ RHIC, LHC because tform >> tcross
- When comparing experiment, please beware of effects interplay
- Same xF or same shadowing scheme!
- _No firm conclusion_...

- 2008, October 8th

- Cold effects on heavy flavours - raphael@in2p3.fr

- Woehri et al,
- Hard probes 2008

- See also, Arleo and Tram,
- EPJC55 (2008) 449, slide XX

- P. Braun-Munzinger

- Cortese (NA60), Hard probes 08
- + homemade powerpoint fits

## RHIC & rapidity dependence

- Linking rapidity and shadowing...

## The hot (burning) question...

- In AA collisions, is the higher J/ψ suppression seen at forward rapidity due to cold effects?
- Otherwise, the hot candidate is quark recombination
- The relevant plot 
- Need a 40% effect...

- 2008, October 8th

- Cold effects on heavy flavours - raphael@in2p3.fr

- A. Linden-Levy
- T. Gunji

- 60%

- PHENIX, PRL98 (2007) 232301

## Linking rapidity & shadowing

- At RHIC, J/ mostly produced by gluon fusion, and thus sensitive to gluon pdf
- For example, in Phenix, rapidity probes different momentum fraction of Au gluons
- 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

- 2008, October 8th

- Cold effects on heavy flavours - raphael@in2p3.fr

- d

- Au

## RdAu vs rapidity

- RdAu vs rapidity

**NDSG Shadowing scheme**

**EKS Shadowing scheme**

- 2008, October 8th

- Cold effects on heavy flavours - raphael@in2p3.fr

- A. Linden-Levy

- PHENIX, PRC 77 (2008)  024912

_**Underestimated error bars**_** to be revisited**
**σ****abs**** not better known than a couple of mb!**
**No strong constraint on shadowing models**

## A complication : production mechanisms

- Cold effects depend on production mechanisms
- For instance :
- g + g→ J/ψ (+ soft) giving *intrinsic* pT (from initial gluons kT)
- g + g J/ψ + g giving *extrinsic* pT (balanced        by gluon pT) and _working well for pp_
- Sample different xBjorken

- 2008, October 8th

- Cold effects on heavy flavours - raphael@in2p3.fr

- Possible solution of the J/ψ production puzzle,
- Haberzetl & Lansberg, PRL100 (2008) 032006

- Fereiro, Fleuret, Lansberg and
- Rakotozafindrabe  arXiv:0809.4684

**log scale**

## Extrinsic/intrisic effect on dAu and AuAu

**Effect on dAu ≈ 10% **
**(on top of shadowing)**

**Effect on AuAu **
**Intrinsic R****AA****(y=1.7) = R****AA**** (y=0)**
**Extrinsic ≈ 10% (right direction)**

- 2008, October 8th

- Cold effects on heavy flavours - raphael@in2p3.fr

- extrinsic

- intrinsic

- Fereiro, Fleuret, Lansberg and
- Rakotozafindrabe  arXiv:0809.4684

## To illustrate that we don’t know much... 

**nuclear absorption **

**pdf modifications**

***“******Use EKS98 & EPS08 in parallel to map out most of such uncertainty”***

- 2008, October 8th

- Cold effects on heavy flavours - raphael@in2p3.fr

- INTERPLAY

- EKS 98

- EPS 08

- J/ψ
- RHIC
- y=1.7

- σnDS(mb)

- σEKS

- Arleo & Tram, EPJC55 (2008) 449-461

- Pb/p

-  a global (uneasy) fit of σabs to all data
-  shadowing scheme dependence of σabs
-  σabs = 3.5 ± 0.2 ± 1.7 mb

- Eskola, Paukkunen, Salgado, JHEP 0807 (2008) 102
- Eskola & Paukkunen, Hard probes 2008

## What should we do now ?

- Try not to rely on shadowing and σabs ?
- (centrality dependence and data driven method)
- Try to disentangle them ?
- (open charm)

- 2008, October 8th

- Cold effects on heavy flavours - raphael@in2p3.fr

## RHIC J/ψ centrality dependence

- First place where we compute centrality in pA like collisions !
- Can this replace varying A ?

- RGdC, QM06, JPG35 (2008) 104023
- PHENIX, PRC 77, 024912 (2008)

- A data driven method in which you don’t rely on 1/ shadowing scheme 2/ σabs 3/ production mechanism  4/ feed down ratio, but on A/ a (usually assumed) factorization and B/ the Glauber model.

## RdA versus centrality

- Convert to local impact parameter and fit... Ex:

- 2008, October 8th

- Cold effects on heavy flavours - raphael@in2p3.fr

- PHENIX, PRC 77 (2008) 024912

**–****2.2 < y < –1.2**

**|y| < 0.35**

**1.2 < y < 2.2**

- b(fm)

## Plug it in a Glauber model

- 2008, October 8th

- Cold effects on heavy flavours - raphael@in2p3.fr

- Glauber provides, for a given A+A collision at bAA, a set of N+N collisions occurring at bi1 and bi2.
- One minimal assumption is rapidity factorization: RAA(|y|,bAA) =
- Σcollisions [ RdA (-y,bi1) x RdA (+y,bi2) ] / Ncoll
- Correct (at least) in the case of absorption & shadowing since production :
- ~ pdf1 x pdf2 x exp –ρσ(L1+L2)

## Extrapolate to AuAu

- Full error propagation of dAu uncertainties
- [ dramatic for midrapidity since R(–y) = R(+y) ]

-  J/ψ anomalous suppression could
- be the same at mid and forward rapidity!

- 2008, October 8th

- Cold effects on heavy flavours - raphael@in2p3.fr

- Survival = 55 +23–38 %

-  Midrapidity

- PHENIX, PRC 77  (2008) 024912

## Recent news from CGC

- 2008, October 8th

- Cold effects on heavy flavours - raphael@in2p3.fr

- Gluon saturation could further suppress forward J/ψ in AuAu
- First numerical estimate
- _Absolute amount of suppression is fitted to the AuAu data_!
- Waiting forward to new dAu data to fit them first
- However, rapidity dependence should be ok
- But it _fails to reproduce peripheral data_ 
- Anyway...

- Kharzeev, Levin, Nardi, Tuchin
- arXiv: 0808.2954 & 0809.2933

*dN/dy*

-  J/ψ anomalous suppression could
- be the same at mid and forward rapidity!

## Open charm

- “We want open charm!”
- Should help understanding shadowing (common with closed charm)

- 2008, October 8th

- Cold effects on heavy flavours - raphael@in2p3.fr

- Peter
- Helmut

## Heavy flavour (bulk)

- 2008, October 8th

- Cold effects on heavy flavours - raphael@in2p3.fr

- A factor of 2 difference between experiments
- “detector material is not the issue”
- Open charm is suffering from a ≈25% systematic error
- Too large to constrain any shadowing...
- Binary scaling (within these uncertainties...)

- ?

- ???

- Zhangbu Xu

- PHENIX, PRL98 (2007) 172301

## Heavy flavour rapidity dependence?

- 2008, October 8th

- Cold effects on heavy flavours - raphael@in2p3.fr

- Only pp measurement, very poorly known

- D. Hornback, PHENIX, QM08

## Heavy flavour (pT dependence)

- 2008, October 8th

- Cold effects on heavy flavours - raphael@in2p3.fr

- STAR, PRL (2007) 192301

- Interesting d-Au excess? Needs confirmation with run8!

- _Homemade_ RdA from PHENIX preliminary dAu (run3) and PHENIX published pp
-  Wait for serious run8 analysis

## Even better will be the silicon era...

- PHENIX

- STAR

- 2008, October 8th

- Cold effects on heavy flavours - raphael@in2p3.fr

- 38

## Bonus : Cronin effect and J/ψ pT broadening

- (doesn’t change the total yield)

- 2008, October 8th

- Cold effects on heavy flavours - raphael@in2p3.fr

## Cronin effect...

- Multiple scattering of the incoming partons raise the outgoing quarkonia pT
- <pT2>AB = <pT2>pp + δ x L (random walk)

- 2008, October 8th

- Cold effects on heavy flavours - raphael@in2p3.fr

- FNAL

- SPS

- Cortese (NA60), Hard probes 08
- + homemade powerpoint fits

## Cronin effect at RHIC?

- 2008, October 8th

- Cold effects on heavy flavours - raphael@in2p3.fr

- 2.7 sigma slope

- Mid rapidity

- Forward rapidity

- No strong <pT2> dependence...
- Modest rise at forward rapidity
- Could be broadening

- <pT2> from PHENIX,
- PRL101 (2008) 122301
- Homemade L values

## LHC = uncharted territory

## LHC : another cold vs hot fight ?

- EKS vs EPS extrapolation vary by factors of 10 at LHC x’s ! And you need two gluons...
- Would be fun if regeneration takes over...

- 2008, October 8th

- Cold effects on heavy flavours - raphael@in2p3.fr

- EKS 98

- EPS 08

- 2.5 < y <
-  4

- Pb/p

- -0.9
- < y <
- 0.9

- -4
- < y <
- -2.5

- (emited gluons and pT neglected)

**10****–5**** **

- ALICE

- C
- M
- S

## Conclusions

- Heavy flavour suffer from cold effects, which are quite unconstrained...
- Easier when they go in the opposite direction as the hot effects
- e.g.  for the jet quenching
- Let’s hope it will be the case for the J/ψ at LHC
- But RHIC can still play:
- RHIC run8 : J/ψ, open charm, ψ’...
- Silicon upgrades for open charm
- I think a dCu run could be interesting too (ala SPS)

- 2008, October 8th

- Cold effects on heavy flavours - raphael@in2p3.fr

## BTW, Nambu, Maskawa and Kobayashi got the Nobel Prize yesterday 

- 2008, October 8th

- Cold effects on heavy flavours - raphael@in2p3.fr

- (RGdC, PhD thesis)

## That’s all folk...

- 2008, October 8th

- Cold effects on heavy flavours - raphael@in2p3.fr

## J/ψ different energy

- 2008, October 8th

- Cold effects on heavy flavours - raphael@in2p3.fr

- open charm

- dE/dx ?
- Intrinsic
- Charm ?

- Shadowing ?

- Absorption ?

-  = xp- xA

-  = xA

## Intrisic / extrinsic on AuAu

- 2008, October 8th

- Cold effects on heavy flavours - raphael@in2p3.fr

## Complication : feed-down

**χ****c**** large dispersion**

**ψ’ = 8.6 pm 2.5 % at RHJIC**

- 2008, October 8th

- Cold effects on heavy flavours - raphael@in2p3.fr