1 / 23

Chun Zhang Oak Ridge National Lab. For PHENIX Collaboration

Measuring nuclear modification on hadron productions at backward/forward rapidities in d+Au collisions at PHENIX. Chun Zhang Oak Ridge National Lab. For PHENIX Collaboration. Q s ~ A 1/3 e λ y. Small Bjorken x gluons.

corar
Download Presentation

Chun Zhang Oak Ridge National Lab. For PHENIX Collaboration

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Measuring nuclear modification on hadron productions at backward/forward rapidities in d+Au collisions at PHENIX Chun Zhang Oak Ridge National Lab. For PHENIX Collaboration

  2. Qs~ A1/3 eλy Small Bjorken x gluons • Gluon density increases very fast with increasing Q2 and decreasing Bjorken x. • Heavy nuclei enhance gluon color field by A1/3. • Gluons from different nucleons start to overlap to each other in phase space. • Gluon density is saturated. • The color field inside heavy nuclei may become classical field, fluctuation of the field is much smaller than the field strength. • Color Glass Condensate(CGC) • Explore saturation phenomena with the PHENIX forward/backward detectors. • Qs ~ 2.0GeV/c at PHENIX forward coverage.

  3. PHENIX muon arms (sNN)1/2 = 200 GeV PHENIX has two muon arms, south (-2.2 < η < -1.2) and north (1.2 < η < 2.4). Each arm has a Tracking detector and a Muon identifier. Tracking detector consists of 3+3+2 cathode strip chambers located at different position in a magnetic field. Muon Identifier consists of 5 gaps of transversely oriented Iarocci tube planes, interleaved with layers of steel. Two Beam Beam counters, South and North, south BBC used to determine the collision impact parameter. gold deuteron North/Forward South/Backward

  4. deuteron gold b Centrality determinationCategorize collisions by <Nbinary> • We want to normalize the physics quantity by number of nucleon nucleon collisions Nbinary for comparison. • In PHENIX, we use south Beam Beam Counter ( -3.1 >  > -3.9 ) to determine the centrality classes for dAu collisions.. • Multiplicity seen by the PHENIX south Beam Beam Counter (BBCS) is proportional to Nbinary. • Events are thus categorized into four centrality bins by their BBCS multiplicity ( or percentage of multiplicity distribution). • Each centrality bin maps into an Nbinary distribution by a model.

  5. 4.0 > pT > 1.5 GeV/c Charged hadron Rcp Impact parameter increasing Black solid dot : backward; reminder high x in gold, low x in deuteron η [-2.0, 1.4] η [1.4, 2.2] Black solid square : foward; Reminder low x in gold, high x in deuteron PRL. 94 082302, 2005

  6. D. Kharzeev et.al PLB. 599, 23(2004) 0-20/60-80 30-50/60-80 30-50/60-80 0-20/60-80 R. Vogt Phys.Rev. C70 064902(2004) The CGC calculation has two free parameters, which are fixed by fitting the BRAHMS results. • assumes shadowing stems from the multiple interactions of the incident partons. ws assumes that shadowing is proportional to the local density. Compare with theoretical calculations

  7. Azimuthal correlation between two particles at different rapidities • CGC also predicts that when near-side and away-side hadrons are separated by several units of rapidity, quantum evolution effects lead to • the depletion of back-to-back correlations as a function of rapidity interval between the detected hadrons (at fixed pT). • There is ~2 unit rapidity gap between the PHENIX south/north muon arms and the PHENIX central arms(0.35 >  > -0.35). • In d+Au, north-central correlations are sensitive to small Bjorken x partons in gold nuclei and south central correlations are sensitive to large Bjorken x partons in gold nuclei D. Kharzeev, E. Levin, L. McLerran Nucl.Phys. A748 (2005) 627-640

  8. Simulation Associated particle Trigger Particle Trigger Particle Associated particle Kinematics Central arms North arm South arm • Trigger particles are charged hadrons from muon arms and associated particle are charged hadrons from central arms • There is a pseudo-rapidity gap between trigger particles and associated particles, No near side correlations.

  9. Correlation functions for muon-central correlation in p+p

  10. Correlation functions for south-central correlation in d+Au 0-40%sensitive to large x in gold nuclei

  11. Correlation functions for north-central correlation in d+Au 0-40%sensitive to small x in gold nuclei

  12. Correlation functions for south-central correlation in d+Au 40-88%sensitive to large x in gold nuclei

  13. Correlation functions for north-central correlation in d+Au 40-88%sensitive to small x in gold nuclei

  14. Summary • In d+Au collisions, suppression at forward rapidity and enhancement at backward rapidity on hadron yields relative to N binary scaling are observed by PHENIX. • Two theoretical calculations, i.e. CGC and leading twist shadowing are compared with data at forward rapidity. The comparison suggests CGC calculations describe experimental observation better. • CGC has also predicted the mono-jet when near side jets at forward rapidity and back-to-back jets are several units rapidity away. • We are able to see jet-like signals in the PHENIX muon arm and central arm two particle correlations in p+p, peripheral d+Au as well as central d+Au. • The detail analysis on how to quantify these jet signals is undergoing right now.

  15. BACKUPS

  16. Determine centrality • PHENIX South BBC locates at gold going side • The charge multiplicity on BBC south proportion to Npart of Au nucleus

  17. Rcp @ y = 0 Impact parameter in creasing

  18. Stopped muons Stoppedhadrons • Muons stopping in gap 3 have lost 2.5 GeV of energy via dE/dx • Hadrons stopping in gap 3 typically have much higher energy and stop inelastically Momentum (GeV/c) MC muons Blue is for muons stopping at gap3 h/m Separation Purple is for muons stopping at gap2

  19. Fermi Effect enhancement Saturation? EMC effect shadowing Nuclear DIS and Nuclear modification • Structure functions in bound nucleons are different from structure functions in free nucleons • In different x range, the nuclear modification behaves differently, • x>0.8, ratio >1 : Fermi Motion. • 0.8>x>0.2, ratio <1 : EMC effect. • 0.2>x>0.08, ratio > 1 : anti-shadowing • 0.08>x, ratio <1 : shadowing • The modification is A dependent and varies with • Q2 very slowly.

  20. Shadowing in DISModification on partonic structure • Partons localized longitudinally with a distance z = 1/(xpN), if z ≥ 2RAM/pN, partons from different nucleons overlap, fusion. xN = 1/(2RNM) ~ 0.1 xA = 1/(2RAM) L.V. Gribovet.al. Nucl. Phys. B188(1981)555 A.H. Mueller and J. Qiu Nucl. Phys. B268(1986)427 K. J. Eskola, J. Qiu and X.N. Wang Phys.Rev.Lett. 72 (1994) 36-39 • Depletion in low x, enhancement in high x NMC data Berger and Qiu PLB 206(1988)141 F.F Close and R. Robert PLB213(1988)41 Q2 rescaling plus xN and xA for the onset of shadowing

  21. Shadowing in DISGeneralized Vector Meson Dominance (GVMD) Compare with NMC data Q2 = 14 GeV2 Q2 = 2.8 GeV2 d is the coherent length of the vector meson, l is the mean free path. d > l && RA > l Shadowing effect disappears when x increases at fixed Q Michele Arneodo, Phys. Rep. 240(1994) 301 C.L. Bilchak, et.al. Phys. Lett. B 233(1989)461

  22. Proton Nucleus collisions • pA or dA Drell-Yan and J/Y • Inclusive hadron production Alberto Accardi and Miklos Gyulassy J. Phys. G30 (2004) S969-S974

  23. Nuclear modification @ RHIC Q2 102 RHIC All previous pA, AA 101 10-2 10-1 xbj

More Related