J/ψ and ϒ production in proton+nucleus collisions: lessons from RHIC for the 2012 p+Pb LHC run

Elena G. FerreiroUniversidade de Santiago de Compostela, Spain

in collaboration with F. Fleuret, J-P. Lansberg , N. Matagne and A. Rakotozafindrabe

EPJC61 (2009), PLB680 (2009), PRC81 (2010), NPA855 (2011), FBS53 (2012), arXiV:1110:5047

Heavy Ion Collisions in the LHC Era 16 - 20 July 2012, Quy Nhon, Vietnam

• If we focalise on p+A data (where no QGP is possible) only cold nuclear matter (CNM) effects are in play:

shadowing and nuclear absorptionEMC and energy loss

• A lot of work trying to understand A+A data (since J/y QGP signal)

• In fact, the question is even more fundamental: p+p data we do not know the specific production kinematics at a partonic level: (2→2,3,4) vs (2→1)

Quarkonium as a hint of deconfinement

Quarkonium as a hint of coherence

Quarkonium as a hint of QCD1

LHC p+Pb run

Motivation

E. G. Ferreiro USC ϒ and J/ψ production in pA: from RHIC to LHC HIC in the LHC Era 19 July 2012 1

ContentsOur goal:

To investigate the CNM effects and the impact of the specific partonic production kinematics

3 ingredients:• Quarkonium partonic production mechanism

• Shadowing • Nuclear absorption

• Results on J/y production @ RHIC and LHC

To extend our study to ϒ and other CNM effects : • fractional energy loss

• gluon EMC effect• • Results on ϒ and J/y production @ RHIC

• Results on ϒ @ LHC2E. G. Ferreiro USC ϒ and J/ψ production in pA: from RHIC to LHC HIC in the LHC Era 19 July 2012 2

Background

E. G. Ferreiro USC ϒ and J/ψ production in pA: from RHIC to LHC HIC in the LHC Era 19 July 2012 3

Particle spectrum altered by interactions with the nuclear matter they traverse=> J/Y suppression due to final state interactions with spectator nucleons

• 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 => Smaller nuclear absorption

sabs @ mid y < sabs @ forward y?Rapidity dependence of nuclear absorption?

• Usual parameterisation:(Glauber model)

Nuclear absorption: a final cold nuclear matter effect

Energy dependence

In terms of formation time:

Sabs = exp(-r sabs L )nuclear matter density break-up cross section path length

5

C. Lourenço et al.

E. G. Ferreiro USC ϒ and J/ψ production in pA: from RHIC to LHC HIC in the LHC Era 19 July 2012 4

• Nuclear shadowing is an initial-state effect on the partons distributions• Gluon distribution functions are modified by the nuclear environment• PDFs in nuclei different from the superposition of PDFs of their nucleons

Shadowing: an initial cold nuclear matter effect

Shadowing effects increases with energy (1/x) and decrease with Q2 (mT)

shadowing

antishadowing

3

EMCThe shadowing corrections

depend on the partonic process producing the J/Ysince it affects kinematics (x,Q2)

E. G. Ferreiro USC ϒ and J/ψ production in pA: from RHIC to LHC HIC in the LHC Era 19 July 2012 5

On the kinematics of J/y production: two approaches

Investigating two production mechanisms (including pT for the J/y):

g+g → J/y• intrinsic scheme: the pT of the J/y comes from initial partons

Not relevant for, say, pT>3 GeVOnly applies if COM(LO, as

2) is the relevant production mechanism at low pT

g+g → J/y+g, gg,ggg,…•extrinsic scheme: the pT of the J/y is balanced by the outgoing parton(s)

COM (NLO, NNLO), CSM (LO, NLO, NNLO)

• CNM -shadowing- effects depends on J/y kinematics (x,Q2)

• J/y kinematics depends on the production mechanism =>

2→2, 3, 4

2→1

for a given y, larger x in extrinsic scheme => modification of shadowing effects

E. G. Ferreiro USC ϒ and J/ψ production in pA: from RHIC to LHC HIC in the LHC Era 19 July 2012 6

• in order to reproduce data @ RHIC: nuclear absorption sabs extrinsic > sabs intrinsic the kinematics matter for the extraction of sabs

2→2

g+g

→ J/y+g

2→1

g+g

→ J/y

• shadowing depends on the partonic process: 2→1 or 2→2

E. G. Ferreiro, F. Fleuret, J. P. Lansberg and A. Rakotozafindrabe PRC 81 (2010) 064911

How partonic kinematics affects CNM: J/y in d+Au @ RHIC

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J/y in Au+Au @ RHIC: rapidity dependence

• The J/y suppression from shadowing is y-dependent Reminder: sabs taken as constant

• Can account for a part of the y-dependence of the most central data

E. G. Ferreiro USC ϒ and J/ψ production in pA: from RHIC to LHC HIC in the LHC Era 19 July 2012 8

“CEM NLO” before kT smearing “Traditional” 2 → 2

J/y in Pb+Pb @ LHC: centrality dependence vs data

E. G. Ferreiro USC ϒ and J/ψ production in pA: from RHIC to LHC HIC in the LHC Era 19 July 2012 9

“CEM NLO” before kT smearing “Traditional” 2 → 2

underlying partonic model

without kt smearing with kt smearing

kt smearing procedure is applied after the (x1,x2) integration

J/y in Pb+Pb @ LHC: centrality dependence vs data

E. G. Ferreiro USC ϒ and J/ψ production in pA: from RHIC to LHC HIC in the LHC Era 19 July 2012 10

Uncertainty bands:mF from 0.5 mT to 2 mT

(as done in pp for g(x,mF)

Something new… searching for other CNM effects:ϒ production

• Gluon EMC effect

• Fractional energy loss

E. G. Ferreiro USC ϒ and J/ψ production in pA: from RHIC to LHC HIC in the LHC Era 19 July 2012 11

Absorption: ϒ vs J/y

E. G. Ferreiro USC ϒ and J/ψ production in pA: from RHIC to LHC HIC in the LHC Era 19 July 2012 12

uncertainty principle: time needed – in their rest frame to distinguish the energy levels of the 1S and 2S states

RHIC: sϒ

abs < 1 mb

nPDF uncertainty on ϒ production in d+Au @ RHIC

• backward: ok within uncertainties• central: reasonable job • forward : clearly too high (for any σabs)

Physical interpretation• backward: EMC effect• central: antishadowing • forward : shadowing≈1 energy loss is needed

Extrinsic scheme: sabs=0 mb, sabs= 0.5mb , sabs= 1 mb in 3 shadowing models

16E. G. Ferreiro USC ϒ and J/ψ production in pA: from RHIC to LHC HIC in the LHC Era 19 July 2012 13

Searching for new effects: gluon EMC on ϒ in dAu @ RHIC

antishadowingEMC

Let us try to increase the suppression of g(x) in the EMC region, thr shadow incert.:

we have used three of the EPS09 LO sets: one with a quark-like EMC gluon suppression, and the two limiting curves

Works better for backward region

E. G. F., F. Fleuret, J. P. Lansberg and A. Rakotozafindrabe arXiV:1110:5047

What about the forward region?E. G. Ferreiro USC ϒ and J/ψ production in pA: from RHIC to LHC HIC in the LHC Era 19 July 2012 14

Searching for new effects: energy loss on ϒ in dAu @ RHIC

E. G. Ferreiro USC ϒ and J/ψ production in pA: from RHIC to LHC HIC in the LHC Era 19 July 2012 15

WORK IN PROGRESS, preliminary

Searching for new effects: energy loss on ϒ in dAu @ RHIC

E. G. Ferreiro USC ϒ and J/ψ production in pA: from RHIC to LHC HIC in the LHC Era 19 July 2012 16

WORK IN PROGRESS, preliminary

Work in progress: ϒ production @ LHC

• Shadowing effect is not smallRemember that in PbPb collisions at y = 0shadowing effect is squared compared to pPb

E. G. Ferreiro USC ϒ and J/ψ production in pA: from RHIC to LHC HIC in the LHC Era 19 July 2012 17

• Shadowing effect is not smallRemember that in PbPb collisions at y = 0shadowing effect is squared compared to pPb

• Energy loss also likely matters, in particular in the most forward rapidity

Work in progress: ϒ production @ LHC

E. G. Ferreiro USC ϒ and J/ψ production in pA: from RHIC to LHC HIC in the LHC Era 19 July 2012 18

• Shadowing effect is not small Remember that in PbPb collisions at y = 0 shadowing effect is squared compared to pPb

• Energy loss also likely matters• Overall, nuclear matter effects are not small

they should be accounted when analysing PbPb data

Work in progress: ϒ production @ LHC

E. G. Ferreiro USC ϒ and J/ψ production in pA: from RHIC to LHC HIC in the LHC Era 19 July 2012 19

Conclusions

• for J/y d+Au collisions @ RHIC A+A collisions @ RHIC and LHC

CNM strong effects at both energy

• We have studied the influence of specific partonic kinematics

within 2 schemes: intrinsic (2→ 1) and extrinsic (2→2) pT

for different shadowings including nuclear absorption and different partonic models

• for ϒ in d+Au collisions @ RHIC:

EMC effect in the backward region fractional energy loss in the central & forward region• energy loss can also affect J/y @ RHIC•work in progress: ϒproduction @ LHChttp://phenix-france.in2p3.fr/software/jin/index.html

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