Cold Nuclear Matter Physics at Forward Rapidities from d+Au Collisions at PHENIX

Mickey Chiu

QM2011 Annecy 22

PHENIX Muon Piston Calorimeter

Small cylindrical holes in Muon Magnet Pistons, Radius 22.5 cm and Depth 43.1 cm

SOUTH

PbWO4

North

)( 43 yyTd ee

s

px )( 43 yyT

Au ees

px

•Fwd-Fwd, x~(0.001,0.005)•Mid-Fwd, x~(0.008,0.040)•Mid-Bwd, x~(0.050,0.100)

d(forward) Au(backward)

QM2011 Annecy 3

MPC PerformanceNorth MPC

Decay photon impact positions for low and high energy 0s. The decay photons from high energy 0s merge into a single cluster

Sometimes use (EM) clusters, but always corrected to 0 energy

Clusters 80% 0 (PYTHIA)

“Trigger”Near

Far

Jet1

Jet2

QM2011 Annecy 4

•Large suppression in RdA•That increases with centrality•And increases with larger rapidity

•Consistent with previous measurements•However, x covered by single inclusive measurement is over wide range

•Includes shadowing, anti-shadowing, (EMC effect)

RdAu in 2 forward rapidity Bins

Guzey, Strikman, Vogelsang, PLB603, 173

Guzey, Strikman, Vogelsang, PL B603, 173

QM2011 Annecy 5

CNM effects: dynamical shadowing, Energy Loss, Cronin

RdA Past, di-Hadron Future

Kharzeev, NPA 748, 727 (2005)

•Di-Hadron Correlations allow one to select out the di-jet from the underlying event•Constrains x range (probe one region at a time)•Probe predicted angular decorrelation of di-jets (width broadening)

Kharzeev, Levin, McLerran  Nucl. Phys. A748 (2005) 627

Color Glass Condensate

(Qiu, Vitev PLB632:507,2006)

QM2011 Annecy 6

di-Hadron Signal

Peripheral d+Au Correlation Function

d

dN

NN

NCY

assoc

trigassoctrig

pair 1

CORRELATED

Npair

“Di-Hadron Nuclear Modification factor”

trigdA

trigdAdA RIJ

• Possible indicators of nuclear effects

• JdA < 1, RdA < 1

• Angular decorrelation of widths

pppairpp

dApairdA

colldA N

J

/

/1

ppsglpp

dAsgldA

colldA N

R

/

/1

“Sgl-Hadron Nuclear Modification factor”

“Conditional Yield”

Number of di-jet particle pairs per trigger particle after corrections for efficiencies, combinatoric background, and subtracting off pedestal

Caveats:

1. Low pT (but back-to-back peak is selected)

2. Pedestal Determination (Assumed up to twice the width as a systematic).

3. Di-Hadrons instead of di-jets (but ok if fragmentation unmodified)

QM2011 Annecy 7

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

<pTa>=0.55 GeV/c

p+p

Cor

rela

tion

Fu

nct

ion

d+Au 0-20%

d+Au 60-88%

<pTa>=0.77 GeV/c <pT

a>=1.00 GeV/c3.0 < pTt < 5.0 GeV/c

for all plots

pTt, 0

pTa, 0 PHENIX Preliminary

QM2011 Annecy 8

Correlation Widths, d+Au and p+p

• No significant broadening between p+p and d+Au within large experimental uncertainties

Trigger p0: |h| < 0.35, 2.0 < pT < 3.0 GeV Trigger p0: |h| < 0.35, 3.0 < pT < 5.0 GeV

dAu 0-20%

ppdAu 40-88%

8

•Widths are consistent between p+p and d+Au (all centralities) within large statistical and systematic errors•No broadening seen (within errors)

QM2011 Annecy 9

JdA vs Ncoll, pTmid, pT

fwd

MPC 0 pT

•Suppression of di-hadron correlation (relative to p+p binary scaling hypothesis) with

Increasing Centrality

Decreasing pTmid

Decreasing pTfwd

QM2011 Annecy 10

Fwd-Fwd: p+p vs d+Au Peripheral

Peripheral d+Au collisions are similar to p+p collisions

Beam view of d+Au peripheral collisionpT

t, 0

pTa, 0

QM2011 Annecy 11

Fwd-Fwd: p+p vs d+Au Central

“Monojet” in central d+Au collisions

Beam view of d+Au peripheral collisionpT

t, 0

pTa, 0

QM2011 Annecy 12

JdA for Fwd-Fwd

fragAuTTfrag

Au zxs

epepx

21

21

MPC 0 pT

(assuming LO)•Better way to plot:

•Suppression of JdA gets larger in fwd-fwd correlations•Trend with pT, centrality also consistent with mid-fwd correlations

QM2011 Annecy 13

xAufrag Dependence

s

epepx TTfrag

Au

21

21

Note: points for mid-fwd JdA are offset for visual clarityStatistical and systematic errors are added in quadrature

•Plotting vs suggests that the effect is due to something happening in the nucleus as one probes to lower x•Does it prove CGC?

•Shadowing? Initial state energy loss? Multi-Parton Interactions (MPI)?

60-88%(Peripheral)

0-20%(Central)

Trig pT: 1.1-5 GeV/c

Assoc pT:0.5-1.5 GeV

Trig pT: 0.5-7 GeV/c

QM2011 Annecy 14

d

cdab

pbpp

ap

d

cdab

Aub

Auda

d

pppairsppcoll

dAupairsdAu

dA

zzDxfxf

zzDxfxf

NJ

c

c

,)()(

,)()(

/

/

Extending the LO picture

b=0-100%Q2 = 4 GeV2

xAu

EPS09 NLO gluonsEskola , Paukkunen, Salgado, JHP04 (2009)065

),(

),(),(

2

22

QxAxG

QxxGQxR

p

AuAuG

Low x, mostly gluons JdA ~ RGAuHigh x, mostly quarks

Weak effects expected

60-88%(Peripheral)

0-20%(Central)

QM2011 Annecy 15

Backward (Au-going) MPC*

Au-going, high x

Au-going, high x

d-going, low xd-going, low x

•Plotted vs IdA, but when factoring in RdA, this is a suppression of JdA in d-going, and enhancement in Au-going.

•In anti-shadowing region?•Fwd-Bwd Correlations ( ~ 7): Future search for Mueller-Navelet Jets

*See Z. Citron Poster

QM2011 Annecy 16

•Large suppression (up to an order of magnitude) in FWD-FWD di-hadron yields in d+Au relative to p+p (JdA)

•Suppression depends strongly on centrality•And gets stronger as both particles go toward more forward rapidities•Nuclear Shadowing? We see extreme Shadowing in most central.•Gluon Saturation/Color Glass Condensate?•Initial State Energy Loss? MPI?

•Heavy Ion Physics is well into quantitative extraction of the properties of the sQGP•This requires careful control of all aspects of collisions (eg Initial State)•v2/v3, Initial State and /s

•Talks by Shinichi Esumi, Roy Lacey•PHENIX Heavy Flavor Studies

•Talks by Abhisek Sen, Cesar da Silva (Friday)•Angular Broadening of Away Side Jet?

•Mid-Fwd, no increase seen within errors•Mid-MidFwd, also no increase •Fwd-Fwd, currently inconclusive

•Future•Submitted to PRL, arxiv:nucl-ex/1105.5112•Do di-Hadrons measure RG

Au?•Better than incl. hadrons (EPS08)

•p,n tagging, ’s, fwd-bwd, more d+Au running…

Summary

PRL 96:222301,2006

QM2011 Annecy 17

Backup Slides

QM2011 Annecy 18

IdA vs JdA: Can we decouple effects?

d

dN

NN

d

dN

N

N

N

N

NN

d

dN

N

d

dN

NI pp

trigassocpp

evtcoll

dAtrigassoc

dAevt

dAevt

dAtrig

ppevt

pptrigcoll

ppassoc

pptrig

dAassoc

dAtrig

dA)|(

)|(

1

1

1

1

dAtrigdA

trigdA J

RI

1

•IdA is the per trigger comparison of d+Au jet associated counts relative to p+p•JdA is the rate of the associated pairs from a jet (per minbias event)•Can we use this to tell if the jets are modified, or do they disappear?•From the CNT-MPC corrrelations, we get IdA ~ 0.5, and RdA ~ 1.1

•JdA ~ 0.5•The rate of correlated pairs is about half of p+p

•Does this imply that the missing jets have disappeared, and not that they are modified, since IdA ~ JdA?•But not true for STAR FMS triggered-central barrel, where IdA ~ 1 and JdA ~ 0.5

QM2011 Annecy 19

JdA, RdA vs Ncoll

MPC 0 pT

Qiu-Vitev Shadowing + Energy Loss

(private communication)

QM2011 Annecy 20

Muon-Central IdA & Widths, 2003 d+Au

Phys.Rev.Lett.96:222301,2006

dAu

QM2011 Annecy 21

Nuclear Modification in d+Au at Forward(Backward) Rapidity

Phys. Rev. Lett. 94, 082302 (2005)

Punch through hadrons & Hadron decay muons •Forward η suppression •No backward η suppression

•Gluon Saturation?•Cronin, Shadowing, E-loss?

•Look at 2 particle correlations …

21

QM2011 Annecy 22

Run8 FMS p0+h± pT scan (inclusive)

• dAu width larger than pp (consistent with FMS-BEMC results)

• dAu back-to-back peak area larger than pp at lower pT

• Work in progress towards even lower pT

STARSTAR

“gsv”

pp

dAu

Df

Const (BG)

Peak Area

Peak Width

pT1

1.5 2.0 2.5 3.0 GeV/cpT

2 0.5 1.0 1.5 2.0 GeV/c

Slide from A. Ogawa

QM2011 Annecy 23

Where is the Saturation Scale if we are actually seeing the CGC?

Fwd-Fwd?

Iancu and Venugopalan, hep-ph/0303204

Extended scaling?

H. Kowalski and D. Teaney. Phys. Rev.D, 68:114005, 2003

•We evaluated in PYTHIA the ~ coverage for Q2 and x for the fwd-fwd and cnt-fwd correlations•No nuclear modifications evaluated yet•Not clear that we are in the saturation region – possibly in extended region?

•Can we determine Qs from the data?•Go to lower pt, but then background becomes worse•Nuclear Scaling:

Fwd-Cnt?

2

20

2

x

AcQQ A

s

QM2011 Annecy 24

24

Fwd-Fwd Near Side CorrectionPoints affected by pair cuts (and hence merging effects in clustering)

North MPC

“Trigger”Near

Far

Jet1

Jet2