charmonium dissociation and recombination at rhic and lhc
DESCRIPTION
RENCONTRES DE MORIOND: QCD AND HIGH ENERGY HADRONIC INTERACTIONS La Thuile, Aosta valley, Italy March 8th - March 15th, 2008. Charmonium dissociation and recombination at RHIC and LHC. Elena G. Ferreiro Universidade de Santiago de Compostela, Spain. Outline 1. Motivation - PowerPoint PPT PresentationTRANSCRIPT
Charmonium dissociation and recombinationat RHIC and LHC
Elena G. FerreiroUniversidade de Santiago de Compostela, Spain
RENCONTRES DE MORIOND: QCD AND HIGH ENERGY HADRONIC INTERACTIONSLa Thuile, Aosta valley, Italy March 8th - March 15th, 2008
0712.4333 A. Capella, L. Bravina, E.G. Ferreiro, A.B. Kaidalov, K. Tywoniuk, E. Zabrodin0801.4949 E. G. Ferreiro, F. Fleuret, A. Rakotozafindrabe
Outline1. Motivation2. Initial state effects (CNM) in charmonium production
shadowing & absorptionresults for J/psi in d+Au @ RHIC
3. Charmonium suppression in the comover modelresults for J/psi in Cu+Cu and Au+Au @ RHICpredictions for Pb+Pb @ LHC
4. Conclusions
The J/ production: An intringuing story...
Matsui and Satz: J/ψ destruction in a QGP by Debye screening
different states “melting” at different temperatures due to different binding energies.
Color Screening
cc
SPS experimental results presented a compelling evidence for the existence of a new state of matter in which quarks, instead of being bound up into more complex particles such as protons and neutrons are liberated to roam freely. NA50 anomalous
suppressionTheoretical models at SPS: w and wo QGP?
QGP
no QGP QGP
Too many effects...
CGC
QGPpomeron shadowing
gluon shadowing
nuclear absorption
recombination
sequential suppresion
parton saturation
percolation
hadronic comovers
partonic comovers
cronin effectlow x
D
Dc c
co movers
c c
c cJ ψ
gluon
J/c
c-bar c
Color Screening
cc
COLD or HOT effects
CGC
QGP
pomeron shadowinggluon shadowing
nuclear absorption
recombinationsequential suppresion
parton saturation
percolation hadronic comovers
partonic comovers
•cold effects:
•hot effects:
wo or w QGP
recombination
multiple scattering of a pre-resonance c-cbar pair within the nucleons of the nucleus
nuclear structure functions in nuclei ≠ superposition of constituents nucleonsFKG, EKS, pomeron/gluonIMP@RHIC, NI@SPS
IMP@SPS, NI@RHICrecombination effects favoured by the high density of partons become important and lead to eventual saturation of the parton densities non thermal colour connection
dissociation of the c-cbar pair with the dense medium produced in the collision partonic or hadronic
suppression by a dense medium, not thermalized
wo thermalisation, even if the medium is dense NO QGP
w thermalisation QGP
J/ production in pA collisions:
• Only the CNM effects are present in these collisions
• absorption in nuclear matter: abs ~5 mb @ SPS energies vanishing abs @ RHIC energies
• shadowing at high energies, production of heavy state probes the very low-x distribution of the nuclear structure function:
J/ production in AA collisions:
• CNM and QGP effects can be present in these collisions
• what is the underlying mechanism behind J/ suppressionQGP screening, comovers interaction
• puzzle at RHIC: same amount of suppression as at SPS higher suppression at forward than at mid y
• recombination?
CNM effect: nuclear absorption
The primordial spectrum of particles is altered by interactions with the nuclear matter they traverse on the way out to the detector
• At low energy: the heavy system undergoes successive interactions with nucleons in its path and has to survive all of them => Strong nuclear absorption
• At high energy: the coherence length is large and the projectile interacts with the nucleus as a whole => Small nuclear absorption
Coherence length:
At RHIC energies we take: abs=0 at mid rapiditya very small nuclear absorption at forward rapidty
CNM effects: shadowing
• Approach based on multiple collisions • It takes into account triple pomeron interactions • Equivalente to interaction among gluons
Function F gives the amount ofshadowing correctionsF=0 no corrections
pomeron shadowingThe nuclear structure functions in nuclei are modified from the simple superposition of nucleons
phenomenology EKS
The shadowing increases with x and decreases with Q2
J/production in dAu at RHIC
_____ Results from pomeron shadowing
abs=0
_____ Results from EKS shadowing
abs=0
A. Capella, E. G. Ferreiro, Phys. Rev. C76:064906, 2007
More about J/ shadowing effects: checking different models
Method: J/ pT and rapidity extracted from PHENIX 200 GeV p+p data 2
21
with
1
TT
y
NN
T
pmm
es
mx
²
, Glauber Monte Carlo
Results: d+Au collisions @ 200 GeV (no break up cross section abs=0)
arXiv:0801.4949 E. G. Ferreiro, F. Fleuret, A. Rakotozafindrabe
Studying RdAu .vs. pT give new constraints on shadowing models
J/ production in AA collisions at RHIC: Comovers interaction
The interaction of a particle or a parton with the medium is described by thegain and loss differential equations which govern the final state interactions
Assuming only J/dissociation:
Shadowing + comovers dissociation:•Too strong suppression at mid rapidities•Ratio mid/forward rapidities not reproduced
Recombination seems to be necessary at RHIC
Capella & Ferreiro, Phys. Rev. C76 (2007) 064906
Comovers suppression and recombination
We modify the rate equation to include effects of recombination of c¯c pairs in the comovers scenario: inclusion of the gain term
arxiv: 0712.4333 A. Capella, L. Bravina, E.G. Ferreiro, A.B. Kaidalov, K. Tywoniuk, E. Zabrodin
Cross sections are taken from pp data @ 200 GeVand from PYTHIA.
No free parameters in the model!
Comovers suppression and recombination: Comparison with Au+Au data @ RHIC
C=0.32
The effect of recombination is stronger at mid than at forward rapidities
This over-compensates the suppression due to a higher density of comovers at y=0
arxiv: 0712.4333 A. Capella, L. Bravina, E.G. Ferreiro, A.B. Kaidalov, K. Tywoniuk, E. Zabrodin
Comovers suppression and recombination: Comparison with Cu+Cu data @ RHIC
C=0.59 C=0.32
arxiv: 0712.4333 A. Capella, L. Bravina, E.G. Ferreiro, A.B. Kaidalov, K. Tywoniuk, E. Zabrodin
Comovers suppression and recombination: Predictions for Pb+Pb @ LHC
• Recombination: a crucial effect?
• Strong dependence on the charm cross section
• Theoretical extrapolations are very uncertain
• We assume c¯c ~s0.3 C=2.5
Statistical hadroAndronic et al.
Comover modelCapella et al.
Other approaches predict enhancement!
CONCLUSIONS
• PHENIX data on d+Au collisions have revealed that CNM effects play an essential role at RHIC energies
• In order to determine the importance of hot and dense matter effects on J/ production in A+A collisions, it is fundamental to have a proper baseline for CNM effects including
initial state shadowing corrections
Initial CNM effects
shadowing
+ comover interaction
loss and gain eqs at partonic and hadronic level
suppression recombination
•
reproduce data without free parametres:
The nuclear shadowing is calculated from parameterization of diffractive HERA data
We use the interaction comover cross section fixed to reproduce SPS data
For the density of open charm, necessary to estimate recombination, we use the experimental data
Confusing way to distinguish the effects...
CGC
QGP
pomeron shadowing
gluon shadowing
nuclear absorption
recombination
sequential suppresion
parton saturation
percolation
hadronic comovers
partonic comovers
….
cronin effect
•initial effects
•final effects
Nuclear absorption
At RHIC and y=0, x= 0.025-0.05