Forward (onium) physics from PHENIX Mickey Chiu

Why are we interested? High energy behavior might be universal across all hadrons and predicted entirely by the CGC as CGC: Geometric Scaling Strongly coupled regime which becomes classical  computable!  0.3 x < 10 -2

CGC in Heavy Ion Collisions As Initial state for Heavy Ion Collisions Multiplicity Distributions Long range correlations from a “glasma”, explanation of the ridge PHOBOS W=200 GeV But the outstanding question is, do we see the CGC at RHIC?

 related to rapidity of produced hadrons. As y grows Expectations for a color glass condensate Kharzeev, Kovchegov, and Tuchin, hep-ph/ Iancu and Venugopalan, hep-ph/ Are the forward d+Au results evidence for gluon saturation at RHIC energies? Not clear. Need more data, and more observables.

2  2 Hard Scattering (LO) a. y 3 forward, y 4 mid-rapidity (MPC-EMC) b. y 3, y 4 both forward (MPC-MPC) a. y 3 forward, y 4 backwards (MPC.S-MPC.N) Simply Elastic Scattering p1p1 p2p2 p3p3 p4p4 P=  s/2 P Initial State: Final State: Special Cases:

2 Jun 2009Color Glass Condensate Workshop, RHIC-AGS PHENIX Muon Piston Calorimeter Small cylindrical hole in Muon Magnet Piston, Radius 22.5 cm and Depth 43.1 cm SOUTHNORTH 2.16Refractive Index , 500 nmMain Emission Lines 1000 GyRadiation Hardness -2% /  C Temp. Coefficient ~10 25  C Light Yield 22.4 cmInteraction Length 0.89 cmRadiation Length 2.0 cmMoliere radius gWeight 20 X0, 0.92 Length 2.2x2.2x18 cm 3 Size 8.28 g/cm 3 Density PbWO 4

2 Jun 2009Color Glass Condensate Workshop, RHIC-AGS rapidity  coverage 2  EMCAL + Central Tracker PHENIX Acceptance MPC Addition of MPC increases PHENIX acceptance for calorimetry by a factor of 4 (with a detector more than 10 times smaller) Especially important that the very forward region (  >3) is covered EMCAL + Central Tracker South Muon Tracker North Muon Tracker

2 Jun 2009Color Glass Condensate Workshop, RHIC-AGS PHENIX Side View Muon Piston Muon Piston Calorimeter (MPC) PHENIX central spectrometer magnet

2 Jun 2009Color Glass Condensate Workshop, RHIC-AGS Forward/Central Correlation d Au  0, or clusters PHENIX central spectrometer magnet Backward direction (South)  Forward direction (North)  Muon Piston Calorimeter (MPC)  0 or h +/-

2 Jun 2009Color Glass Condensate Workshop, RHIC-AGS The MPC can reliably detect pions (via  0   ) up to 17 GeV in energy –Limitations are the tower separation and merging effects  p T max ~ 1.7 GeV/c To go to higher p T, use single clusters in the calorimeter –Use  0 s for 7 GeV < E < 17 GeV –Use clusters for 20 GeV < E < 50 GeV Correlation measurements are performed using  0 s, clusters Use event mixing to identify pions  form foreground (same event pairs) and mixed event background photon pair distributions MPC Pion/Cluster Identification North MPC M inv (GeV/c 2 ) 12 < E < 15Foreground Background Yield

2 Jun 2009Color Glass Condensate Workshop, RHIC-AGS Correlation Measurements  s NN = 200 GeV d-Au, pp collisions from 2008 at RHIC –No flow contribution –Rapidity separated jets produce no nearside peak  Constant background + Gaussian signal Trigger particles are (  0, h +/- ) with |  | < 0.35 Associate particles are  0, clusters with 3.1 <  < 3.9 One method to quantify the correlation: –To compare pp with dA, form ratio of conditional yields N pair  Peripheral d-Au Correlation Function

2 Jun 2009Color Glass Condensate Workshop, RHIC-AGS h +/- (trigger,central)/  0 (associate,forward)  =0.55 GeV/c pp Correlation Function dAu 0-20% dAu 60-88% =0.77 GeV/c =1.00 GeV/c p T t, h +/- p T a,  < p T t < 2.0 GeV/c for all plots

2 Jun 2009Color Glass Condensate Workshop, RHIC-AGS  0 (trigger,central)/  0 (associate,forward)  =0.55 GeV/c pp Correlation Function dAu 0-20% dAu 60-88% =0.77 GeV/c =1.00 GeV/c 2.0 < p T t < 3.0 GeV/c for all plots p T t,  0 p T a,  0

2 Jun 2009Color Glass Condensate Workshop, RHIC-AGS  0 (trigger,central)/cluster (associate,forward)  =1.09 GeV/c pp Correlation Function dAu 0-20% dAu 60-88% =2.00 GeV/c =3.10 GeV/c 2.0 < p T t < 3.0 GeV/c for all plots p T t,  0 p T a, cluster

2 Jun 2009Color Glass Condensate Workshop, RHIC-AGS Forward/Central Correlation Widths No significant changes in correlation width between pp and dAu within experimental uncertainties Trigger  0 : |  < 0.35, 2.0 < p T < 3.0 GeV/c Trigger  0 : |  < 0.35, 3.0 < p T < 5.0 GeV/c dAu 0-20% pp dAu 40-88%

2 Jun 2009Color Glass Condensate Workshop, RHIC-AGS Forward/Central I dA vs N coll Increasing suppression of I dA reaches a factor 2 for central events Model calculations are needed to distinguish between different models –Saturation (Color Glass Condensate) –Shadowing –Cronin –Others? Associate  0 : 3.1 <  < 3.9, 0.45 < p T < 1.59 GeV/c

2 Jun 2009Color Glass Condensate Workshop, RHIC-AGS 2009 Muon-Central IdA & Widths, 2003 d+Au Phys.Rev.Lett.96:222301,2006 d Au

2 Jun 2009Color Glass Condensate Workshop, RHIC-AGS 2009 d+Au RCP, 1.2<|  |<2.2 RHIC experiments have observed a suppression of hadron production relative to binary collision scaling in deuteron-gold reaction at forward rapidity sensitive to low x partons in the gold nucleus, Phys.Rev.Lett.94:082302,2005). PHENIX 2003 d+Au

2 Jun 2009Color Glass Condensate Workshop, RHIC-AGS 2009 Kopeliovich, hep- ph/ v3 Universal Sudakov suppression (energy conservation) Vitev, hep-ph/ v1 CNM effects: dynamical shadowing, dE/dx, Cronin Vitev, hep-ph/ v2 Dynamical shadowing Kharzeev, NPA 748, 727 (2005) 19

2 Jun 2009Color Glass Condensate Workshop, RHIC-AGS 2009 At least two kinds of effects may give suppression in pairs that include a forward rapidity wrt mid-rapidity trigger hadron Mono-jets in the gluon saturation (CGC) picture give suppression of pairs per trigger and some broadening of correlation Kharzeev, NPA 748, 727 (2005) P T is balanced by many gluons Dilute parton system (deuteron) Dense gluon field (Au) Rapidity-separated hadron correlations in d+Au shadowing (non-LT) gives suppression of pairs wrt to singles for mid-rapidity tag – but small for forward tag Vitev, hep-ph/ v2 shadowing (non-LT) gives suppression of pairs wrt to singles for mid-rapidity tag – but small for forward tag Vitev, hep-ph/ v2

2 Jun 2009Color Glass Condensate Workshop, RHIC-AGS 2009 depletion at small-x enhancement (anti-shadowing) at larger-x EMC effect at large x Fermi motion near x~1 Either from global fits to deep-inelasitic scattering and Drell-Yan data e.g. Eskola – EPS09 arXiv: Or from coherence models e.g. Vitev hep-ph/ Shadowing & the EMC effect

2 Jun 2009Color Glass Condensate Workshop, RHIC-AGS /2/2015 QM09 Knoxville TN 22 Vogt EKS Phys Rev C77, Extrinsic EKS v PHENIX d+Au published J/Psi RdAu Production model makes a difference.

2 Jun 2009Color Glass Condensate Workshop, RHIC-AGS Quarkonia Production & Suppression – J/Ψ in d+Au Initial d+Au J/Ψ update from new 2008 data (~30x 2003) R CP pretty flat vs centrality at backward rapidity; but falls at forward rapidity (small-x) more soon – precision statistics requires precision systematics & careful analysis starting to study constraints on CNM models (thanks R. Vogt) EKS σ = 0,1,2,3,4,…15

2 Jun 2009Color Glass Condensate Workshop, RHIC-AGS 2009 Conclusions Forward Pion I_dA for Central Arm Triggered hadrons – forward MPC pi0’s Widths ~ consistent between p+p and d+Au Associated Yields suppressed in d+Au, and stronger with more central collisions Working on triggered MPC data and Au going MPC side Can then map out x dependence Less forward muon arm triggered (2-5 GeV pT) hadrons – central arm hadron correlations show small I_dAu difference R_dAu of those muon arm hadrons shows suppression pattern New data from run08 on the way Some of the more “ordinary” cold nuclear effects can be mapped out with complementary measurements, like J/Psi. d+Au is a very complicated system

2 Jun 2009Color Glass Condensate Workshop, RHIC-AGS 2009 Backup Slides

2 Jun 2009Color Glass Condensate Workshop, RHIC-AGS 2009 Figure 2: The ratio of gluon distributions in lead relative to deuterium as determined from projected measurements with an EIC, as a function of gluon momentum fraction x. HKM and FGS represent QCD parameterizations of existing data extrapolated linearly to small x. The curve labeled Color Glass Condensate is a saturation model prediction. Domains relevant to nucleus-nucleus collisions at RHIC and the LHC are shown.

2 Jun 2009Color Glass Condensate Workshop, RHIC-AGS Brief PHENIX Status & Future Recent detector improvements: large, more accurate reaction plane detector higher-p T PID (TOF-West) forward (MPC) calorimeters Hadron blind detector (HBD) Operations improvements: integrated luminosity: Au+Au (x3); d+Au (x30) data taking efficiency: 52% (2007) -> 68% (2008) Future: HBD for clean low-mass dielectron measurements (next AuAu run) muon Trigger system for high-p T muon triggering (W’s) silicon detectors for new level of robustness in heavy-quark measurements continuing DAQ upgrades to maintain high speed and efficiency VTX/FVTX HBD MPC

2 Jun 2009Color Glass Condensate Workshop, RHIC-AGS 2009 LHC: extending the low-x reach RHIC as opened the low-x frontier finding indications for new physics (CGC?) LHC will lower the x- frontier by another factor ~30 at the same rapidities

2 Jun 2009Color Glass Condensate Workshop, RHIC-AGS 2009 Cold Nuclear Matter (CNM) & Gluon Saturation Mike Leitch - PHENIX 29 Traditional shadowing or coherence models Gluon saturation at small x; amplified in a nucleus Initial state energy loss & multiple scattering hep-ph/ v1 R G Pb

2 Jun 2009Color Glass Condensate Workshop, RHIC-AGS Experimental Method: Overview Using azimuthal angle two-particle correlation technique –d+Au, pp collisions at  s NN = 200 GeV from RHIC Run8 –Rapidity separated particles with one particle in the forward direction allows one to probe the gluon distribution at lower x –Trigger particles are (  0, h +/- ) with |  | < 0.35 –Associate particles are forward  0 s and clusters with 3.1 <  < 3.9 Central Rapidity Spectrometer 3.1 < η < 3.9 π0π0 π0π0 x-range in Au: < x < 0.1 Forward EMC From calculation by Marco Stratmann

2 Jun 2009Color Glass Condensate Workshop, RHIC-AGS 2009 Any difference between p+p and d+Au? Kharzeev, Levin, McLerran (NPA748, 627) d+Au: Mono-jet? P T is balanced by many gluons Dilute parton system (deuteron) Dense gluon field (Au) Color glass condensate predicts that the back-to-back correlation from p+p should be suppressed p+p: Di-jet

2 Jun 2009Color Glass Condensate Workshop, RHIC-AGS 2009 Forward-midrapidity correlations in d+Au PHENIX doesn’t see any changes for ~ STAR might see suppression for ~ PRL 96, STAR PRL 97, π 0 : | | = 4.0 h ± : | η | < 0.75 p T > 0.5 GeV/c PRL 94,

Regions of: Fermi smearing EMC effect Enhancement Shadowing Saturation? Regions of shadowing and saturation mostly around Q 2 ~1 GeV 2 F 2D /F 2A Observation that structure functions are altered in nuclei stunned much of the HEP community ~25 years ago Cold Nuclear Structure (d+Au)

Saturation picture in nuclei Transverse area of a parton ~ 1/Q 2 Cross section parton-probe :  ~  s /Q 2 Partons start to overlap when S A ~N A  The parton density saturates Saturation scale : Q s 2 ~  s (Q s 2 )N A /  R A 2 ~A 1/3 At saturation N parton is proportional to 1/  s Q s 2 is proportional to the density of participating nucleons; larger for heavy nuclei. Relativistic proton picture Nucleus picture (In rest frame of proton)