Forward (onium) physics from PHENIX

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 E2ln~ Eas

CGC: )/(ln~~~ 222QCDT Eyb

•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?

ln 1x related to rapidity of

produced hadrons.

As y grows

Expectations for a color glass condensate

Kharzeev, Kovchegov, and Tuchin, hep-ph/0307037

Iancu and Venugopalan, hep-ph/0303204

Are the forward d+Au results evidence for gluon saturation at RHIC energies?Not clear. Need more data, and more observables.

22 Hard Scattering (LO)

)(2

)( 4433,4,321

yyyyTzz eeee

mppPxx

)(2

)( 4433,4,321

yyyyTzz eeee

mEEPxx

a. y3 forward, y4 mid-rapidity (MPC-EMC)

)( 431

yyT ees

mx

b. y3, y4 both forward (MPC-MPC)

)( 431

yyT ees

mx 02 x

42

yT es

mx

a. y3 forward, y4 backwards (MPC.S-MPC.N)

31

yT es

mx 4

2yT e

s

mx

Simply Elastic Scattering

),0,0,( 111 PxPxp ),0,0,( 222 PxPxp

ymp Tz sinhymE T cosh)( 43

1yyT ee

s

mx

)( 432

yyT ees

mx

),,( ,333 zT ppEp ),,( ,444 zT ppEp

p1p2

p3

p4

P=s/2 P

Initial State:

Final State:

Special Cases:

2 Jun 2009 Color Glass Condensate Workshop, RHIC-AGS 2009 6

PHENIX Muon Piston Calorimeter

Small cylindrical hole in Muon Magnet Piston, Radius 22.5 cm and Depth 43.1 cm

SOUTH NORTH

2.16Refractive Index

420-440, 500 nmMain Emission Lines

1000 GyRadiation Hardness

-2% / CTemp. Coefficient

~10 p.e./MeV @ 25 CLight Yield

22.4 cmInteraction Length

0.89 cmRadiation Length

2.0 cmMoliere radius

721.3 gWeight

20 X0, 0.92 Length

2.2x2.2x18 cm3Size

8.28 g/cm3Density

PbWO4


-3 -2 -1 0 1 2 3 rapidity

cove

rage

2

EM

CA

L +

Ce

ntr

al

Tra

ck

er

PHENIX Acceptance

MP

C

MP

C

•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

EM

CA

L +

Ce

ntr

al

Tra

ck

er

Sou

th M

uon

Tra

cker

North M

uon T

racker


PHENIX Side View

Muon Piston

Muon Piston Calorimeter (MPC)

PHENIX central spectrometer magnet


Forward/Central Correlation

dAu0, or

clusters

PHENIX central spectrometer magnet

Backward direction (South) Forward direction

(North)

Muon Piston Calorimeter (MPC)

0 or h+/-


• The MPC can reliably detect pions (via 0) up to 17 GeV in energy– Limitations are the tower separation and merging effects

pT max ~ 1.7 GeV/c

• To go to higher pT, use single clusters in the calorimeter

– Use 0s for 7 GeV < E < 17 GeV

– Use clusters for 20 GeV < E < 50 GeV

• Correlation measurements are performed using 0s, clusters

• Use event mixing to identify pions form foreground (same event pairs) and mixed event background photon pair distributions

MPC Pion/Cluster IdentificationNorth MPC

Minv (GeV/c2)

12 < E < 15Foreground

Background

Yield


Correlation Measurements sNN = 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

)Acceptance

/

Acceptance

/(6.1/2

Acceptance

/ 2

8.02

8.0

0

FGFGFGpair

ddNd

ddNd

ddNN

assoctrig

pair

N

NCY

Npair

pp

dAdA CY

CYI

Peripheral d-Au Correlation Function

Acceptance

/ FGddN


h+/- (trigger,central)/0 (associate,forward)

<pTa>=0.55 GeV/c

pp

Cor

rela

tion

Fu

nct

ion

dAu 0-20%

dAu 60-88%

<pTa>=0.77 GeV/c <pT

a>=1.00 GeV/c

pTt,

h+/-

pTa, 0

1.0 < pTt < 2.0 GeV/c

for all plots


0 (trigger,central)/0 (associate,forward)

<pTa>=0.55 GeV/c

pp

Cor

rela

tion

Fu

nct

ion

dAu 0-20%

dAu 60-88%


a>=1.00 GeV/c2.0 < pTt < 3.0 GeV/c

for all plots

pTt, 0

pTa, 0


0 (trigger,central)/cluster (associate,forward)

<pTa>=1.09 GeV/c

pp

Cor

rela

tion

Fu

nct

ion

dAu 0-20%

dAu 60-88%


a>=3.10 GeV/c2.0 < pTt < 3.0 GeV/c

for all plots

pTt, 0

pTa,

cluster


Forward/Central Correlation Widths

• No significant changes in correlation width between pp and dAu within experimental uncertainties

Trigger 0: |< 0.35, 2.0 < pT < 3.0 GeV/c Trigger 0: |< 0.35, 3.0 < pT < 5.0 GeV/c

dAu 0-20%

ppdAu 40-88%


Forward/Central IdA vs Ncoll

• Increasing suppression of IdA 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 < pT < 1.59 GeV/c

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

Muon-Central IdA & Widths, 2003 d+Au

Phys.Rev.Lett.96:222301,2006

dAu


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


Kopeliovich, hep-ph/0501260v3Universal Sudakov suppression(energy conservation)

Vitev, hep-ph/0605200v1CNM effects: dynamical shadowing, dE/dx, Cronin

Vitev, hep-ph/0405068v2Dynamical shadowing

Kharzeev, NPA 748, 727 (2005)

19


•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 correlationKharzeev, NPA 748, 727 (2005)

PT 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 tagVitev, hep-ph/0405068v2

shadowing (non-LT) gives suppression of pairs wrt to singles for mid-rapidity tag – but small for forward tagVitev, hep-ph/0405068v2


• 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:0902.4154

Or from coherence models • e.g. Vitev hep-ph/0309094

Shadowing & the EMC effect

2 Jun 2009 Color Glass Condensate Workshop, RHIC-AGS 200904/21/23 QM09 Knoxville TN 22

Vogt EKS

Phys Rev C77, 024912Extrinsic EKS 0809.4684v1

•2003 PHENIX d+Au published J/Psi RdAu•Production model makes a difference.


23Quarkonia Production & Suppression – J/Ψ in d+Au

Initial d+Au J/Ψ update from new 2008 data (~30x 2003)

• RCP 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)

%8860%8860

%200%200

%200

collinv

collinv

CPNN

NNR

EKS σ = 0,1,2,3,4,…15EKS σ = 0,1,2,3,4,…15


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


Backup Slides


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.


27

Brief PHENIX Status & Future

Recent detector improvements:• large, more accurate reaction plane detector• higher-pT 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-pT 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


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


Cold Nuclear Matter (CNM) & Gluon Saturation

Mike Leitch - PHENIX

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Traditional shadowing or coherence models

Gluon saturation at small x; amplified in a nucleus

Initial state energy loss & multiple scattering

hep-ph/0902.4154v1

RG

Pb


Experimental Method: Overview• Using azimuthal angle two-particle correlation technique

– d+Au, pp collisions at sNN = 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 0s and clusters with 3.1 < < 3.9

Central Rapidity Spectrometer

3.1 < η < 3.9π0

π0

x-range in Au: 0.006 < x < 0.1

Forw

ard

EM

C

From calculation by Marco Stratmann


Any difference between p+p and d+Au?

Kharzeev, Levin, McLerran (NPA748, 627)

d+Au: Mono-jet?

PT 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


Forward-midrapidity correlations in d+Au

• PHENIX doesn’t see any changes for <xg> ~ 0.015

• STAR might see suppression for <xg> ~ 0.006

PRL 96, 222301

STARSTAR PRL 97, 152302

π0: |<η>| = 4.0h±: |η| < 0.75 pT > 0.5 GeV/c

PRL 94, 082302

Regions of:• Fermi smearing• EMC effect• Enhancement• Shadowing• Saturation?

Regions of shadowing and saturation mostly around Q2 ~1 GeV2

F2D/F2A

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/Q2

• Cross section parton-probe : ~ s/Q2

• Partons start to overlap when SA~NA• The parton density saturates

• Saturation scale : Qs2 ~ s(Qs

2)NA/RA2 ~A1/3

• At saturation Nparton is proportional to 1/s

• Qs2 is proportional to the density of participating nucleons; larger for

heavy nuclei.

Relativistic proton picture

Nucleus picture

NBjBjcoh mxpxkl

1~

1~

1~

(In rest frame of proton)

Forward (onium) physics from PHENIX

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