Cold Nuclear Matter effects at RHIC Latest results (run 2008) Frédéric Fleuret - LLR1/18

STAR & PHENIX Frédéric Fleuret - LLR2/18 TPC |  | < 1 0 <  < 2  Tracking  momentum ionization energy loss  electron ID BEMC |  | < 1 0 <  < 2  E/p  electron ID High-energy tower trigger (p T >3GeV)

STAR & PHENIX Frédéric Fleuret - LLR3/18 1.2<|y|<2.2

Data : 1 st d+Au run in 2003 Frédéric Fleuret - LLR4/18 EKS 98 nDSg  Need better precision on d+Au Phys. Rev. C 77, Phys. Rev. C 81,  Need better precision on d+Au Effect of the J/  production mecanism Extrinsic pT (2  2).vs. Intrinsic (2  1) Extrapolation from d+Au to Au+Au for J/  mandatory to measure HDM effects

PHENIX example Data : New d+Au run in 2008 Frédéric Fleuret - LLR5/18 CampagneEspècesÉnergie (GeV) Luminosité intégrée (Phenix) 2000/2001Au+Au130 1,0  b /2002Au+Au p+p ,0  b -1 0,15 pb /2003 d+Au p+p 200 2,74 nb -1 0,35 pb /2004 Au+Au  b -1 9  b /2005 Cu+Cu p+p nb -1 0,19 nb -1 2,70  b -1 3,80 pb /2006 p+p ,7 pb -1 0,1 pb /2007 Au+Au  b /2008 d+Au p+p nb -1 5,2 pb /2009 p+p ,6 pb pb /2010 Au+Au ,7 1,3 nb -1 0,11 nb  b -1 0,26  b -1 ~30 times larger statistic in 2008.vs PHENIX run 3 PHENIX run 8 better precision for J/  first measurement of 

 first measurement in d+Au Frédéric Fleuret - LLR6/18 Made by both STAR and PHENIX (run 2008) See Nicolas’s talk for CNM effect discussion

PHENIX : R dAu and R CP J/  measurement in dAu 2008 Frédéric Fleuret - LLR7/ % Central  the most central 20-40% 40-60% 60-88%  The most peripheral r T (fm) Caution ! wide distributions Most peripheral Most central r T = transverse radius of the NN collisions wrt the center of the Au nucleus R dAu

CNM measurement Frédéric Fleuret - LLR8/18 PHENIX : R dAu arXiv: Production mecanism = intrinsic p T : R. Vogt, Phys. Rev. C71, (2005) Gluon saturation : D. Kharzeev and K. Tuchin, Nucl. Phys. A735, 248 (2004) arXiv : « find a reasonable agreement within uncertainties with the unbiased R dAu data » 2003 data 2008 data Intrinsic p T  reasonable agreement Gluon saturation miss mid y

CNM measurement Frédéric Fleuret - LLR9/18 PHENIX : R CP arXiv: data2008 data R CP has the advantage of cancelling most of the systematic uncertainties. Intrinsic p T + EPS09 R dAu  « reasonable agreement » R CP  miss forward rapidity Gluon saturation : R dAu  miss mid rapidity R CP  « reasonable agreement »

CNM measurement Frédéric Fleuret - LLR10/18 About Extrinsic p T ? Intrinsic p T : (2  1) + EPS09 R dAu  « reasonable agreement » R CP  miss forward rapidity Gluon saturation : R dAu  miss mid rapidity R CP  « reasonable agreement » PHENIX preliminary Extrinsic p T : (2  2) + EKS98 R CP  better agreement than intrinsic (and saturation)  still missing very forward y  abs = 0, 2, 4, 6 mb

Phenix Empirical approach Phenix ArXiv: goal : explore the centrality and rapidity dependence of the nuclear effects Frédéric Fleuret - LLR11/18 As a function of centrality in d+Au : given r T = transverse radius of the NN collisions wrt the center of Au nucleus Empirical parametrization of CNM: R dAu (r T ) = M(r T ) linear  inhomogenous shadowing exponential  absorption Quadratic  energy loss 0-20% Central  the most central 20-40% 40-60% 60-88%  The most peripheral r T (fm) How it works : inhomogenous shadowing 

– Starting point Shadowing parametrizations are given as a function of x, Q² and A All integrated in b (impact parameter) – no spatial dependence available – not possible to study shadowing as a function of centrality – Idea Proposed by R. Vogt and S.R. Klein (2003) See Phys. Rev. Lett (2003) « we discuss how the shadowing and its spatial dependence may be measured … We find that inhomogenous shadowing has a significant effect on central dA collisions » Shadowing Homogenous shadowing Frédéric Fleuret - LLR12/18 gluons in Pb / gluons in p Eskola, Kolhinen, Vogt Nucl. Phys. A696 (2001) The shadowing part

Inhomogenous shadowing Inhomogenous shadowing : (on MC basis) Frédéric Fleuret - LLR13/18 The shadowing part PRL91:« the incident parton interacts coherently with all the target partons along its path length » 9 overlapping nucleons Where the J/  is created

Inhomogenous shadowing Back to PHENIX arXiv: Frédéric Fleuret - LLR14/18 The density weighted longitudinal thickness Shadowing  Linear dependence with longitudinal thickness -a

Phenix empirical approach Parametrizations Frédéric Fleuret - LLR15/18 Note : nuclear absorption is usually quoted as e -  l   = 0.17 nucleon/fm 3  ~ 4 mb = 0.4 fm² l = length of nuclear matter ~ few fm   l  is small a=0 a=a 1 > 0 a=a 2 > a 1 Region with « standard »  abs linear exponential quadratic

Phenix empirical approach Parametrizations against data Frédéric Fleuret - LLR16/18 Backward and mid-rapidity points agree within uncertainties for the three cases presented here. Forward rapidity points require the suppression to be stronger than exponential or linear with the thickness. Cautious, this picture can be misleading backward rapidity  anti shadowing  a shadowing < 0 need nuclear absorption to fit the data  a abs > 0 (in real life, effects should be added together) Some quadratic dependence in forward region  energy loss ?

Summary Frédéric Fleuret - LLR17/18 Extrinsic p T does fit the data well still missing very forward data J/  R CP.vs. R dAu : Quadratic dependence For forward data  R dAu : extrinsic p T Missing very forward data May want to add energy loss for both J/  and 

Conclusion New data available – 30 times more statistic in run 2008.vs – First R dAu for  – High statistical sample for J/  Results – Data may indicate some energy loss in forward rapidity region – Should come in the future : J/  R dAu.vs.p T J/  R dAu.vs.N coll Frédéric Fleuret - LLR18/18