K. Barish

Kenneth N. Barishfor the PHENIX Collaboration

28th Winter Workshop on Nuclear Dynamics

Dorado del Mar, Puerto Rico, April 2012

sPHENIX Spin and Forward Physics

K. Barish

Forward Detector at sPHENIX

Primarily motivations» p+p: Forward transverse asymmetries

– Separation of Sivers and Collins. – Factorization and universality of TMDs.

» d+A: Cold Nuclear Matter– Calibration of quarkonium: J/y and ¡ families– Initial state of heavy ion collisions (connections to

CGC/TMDs?)» A+A:

– 3D “image” of medium

– System expansion viaphotons

K. Barish

The Proton Spin Structure

Polarization experiments» Helicity

– Valence quarks– Sea quarks– Gluons

DSSV arXiv:0904.3821

momentum

K. Barish

The Proton Spin Structure (p+p)

Polarization experiments» Helicity

– Valence quarks– Sea quarks– Gluons

» Transversity

What is the connection to orbital angular momentum?

momentum momentum

K. Barish

Transverse Spin Asymmetries

 

K. Barish

Transverse Spin Asymmetries

𝑥𝐹=2𝑝𝑙

√ 𝑠

In (collinear) pQCD AN should scale like

Asymmetries were expected to be very small.

s 4.4GeV s 6.6GeV s 19.4GeV s 62.4GeV

q s

NT

mA

p

K. Barish

Transverse Spin Asymmetry Sources

(I) Transversity quark distributionsand Collins fragmentation functionCorrelation between proton & quark spin + spin dependant fragmentation function

),()( 221

kzHxqCollins FFQuark transverse

spin distribution

J. C. Collins, Nucl. Phys. B396, 161 (1993)

(III) Higher-twist effectsTwist-3 quark-gluon/gluon-gluon correlatorsExpectation: at large pT, AN ~ 1/pT

So far, fall-off with pT has not been observed.

Graphic from Zhongbo Kang

» Access to non-collinear PDFs» Needs orbital angular momentum of the

quarks

(II) Sivers quark-distribution

Correlation between proton-spin and intrinsic transverse quark momentum

)(),( 21 zDkxf h

qqT

Sivers distribution

D. Sivers, Phys. Rev. D 41, 83 (1990)

X. Ji, J.-W. Qiu, W. Vogelsang, F. Yuan, PRL 97, 082002 (2006)

K. Barish

Factorization & Universality

Collinear factorization for hadron-hadron scattering is well established and universality of the parton distributions are justified. Less experimental data for polarized case, but the data is

supportive and most theoretical foundations are common. Foundation for DG and Dq programs.

Going beyond the twist-2 collinearly factorized picture is essential to explore QCD dynamics and fully understand the spin structure of the nucleon Exploring the validity of factorization and universality of

transverse momentum dependent (TMD) parton distributions factorization is key.

K. Barish

Measurements

Initial state interaction

Sivers effect

Final state interaction

Collins effect

Hard ScatteringTransversity

Twist-3

Transverse Asymmetries

Inclusive AN (central/forward) Hadron Correlations (back-to-back) Interference Fragmentation Functions Jet correlations/structure Drell-Yan

Upgrades

Upgrade plans

Þ Separation of Sivers & Collins and test TMD parton distribution factorization and universality

K. Barish

Global AN Analysis

A. Prokudin, Z.-B. Kang– arXiv:1201.5427 [hep-

ph]

InputHERMES

COMPASS

STAR 0

Functional form similar to DSSV SIDIS PP

d quark Sivers

u quark Sivers

Þ Need to map out Drell-Yan Sivers over a wide kinematic range

K. Barish

Polarized Drell-Yan Production

No fragmentationDirect correlation of intrinsic transverse quark properties and proton spin

Solid factorizationFundamental QCD test

Estimated DY AN

Z. Kang and J. Qiu. Phys. Rev., D81:054020, 2010

Current A

cceptance

Proposed A

cceptance

K. Barish

Drell-Yan Feasibility

Fast Monte-Carlostudies with effective detector smearing

QCD background decreases with increasing rapidity

Drell-Yan reduced signal

K. Barish

What is Needed for DY Measurements?

Measure DY Sivers via p+pe+e— above the J/y but below the ¡ at √s=500 GeV

Asymmetry expected to peak at y~3– Cover 2<h<4

Charge sign determination – Work ongoing to understand how to shape field in large h

region e/p separation

– Hadronic calorimetry, preshower

K. Barish

Jet Correlations / Structure

Initial State (Sivers) Jets with identified hadrons

(measure AN for jets) Do jets from certain quarks

prefer to go left or right?

Goal: Separate the initial state effects (Sivers) from final state effects (Collins). Then compare with other measurements (such as Drell-Yan Sivers). This will provide a stringent test of TMD PDFs factorization and universality.

Final State (Collins) Left-right asymmetry of

identified particle inside a jet Do certain hadrons fragment

from certain quarks to the left or right of the jet axis?

K. Barish

Jet Asymmetry (Sivers)

Initial State (Sivers) Jets with identified hadrons

(measure AN for jets) Do jets from certain quarks

prefer to go left or right? twist 3

Fit of SIDIS

SIDISold

√S = 200 GeVy=3.3 jets

Zhong Bo Kang et al. arXiv:1103.1591 Measurements of jet asymmetry in forward

direction sensitive to quark-gluon correlation function.

K. Barish

Hadrons in Jets (Collins)

Final State (Collins) Left-right asymmetry of

identified particle inside a jet Do certain hadrons fragment

from certain quarks to the left or right of the jet axis?

jet ® h+X

F. Yuan, PLB 666 (2008) 44-47 Direct Collins measurement of fragmentation Expect large asymmetries in forward

direction

K. Barish

What is needed for Jet measurements?

Good Jet reconstruction to be able to measure Sivers cleanly– Electromagnetic and hadronic calorimetry

Particle ID to measure Collins effect– Collins effect different for different hadrons RICH

B Field and tracker to determine charge sign of hadrons

Sivers

Collins

K. Barish

Cold Nuclear Matter (d+Au)

The Physics– Calibration of quarkonium: J/y and ¡ families– Initial state of heavy ion collisions

– connection to CGC – connection to spin physics: TMD PDFs

RHIC’s uniqueness–  Ö s dependence– Possibility of different species– Low Q2

What drives the design– Large data samples– 1>h>4– Detector sensitive to e, g, charged hadrons, jets

Directphoton

Drell-Yan

Open HeavyFlavor

K. Barish

Calibration of quarkoniumParton initial energy loss

Quark pdf

Gluon pdf Absorbtion or breakup cross section

recombination

DY vs √s (quark)

g-jet (quark) open heavy (gluon)

Quarkonia (gluon) A+A quarkonia centrality

A+A open heavy

d+A

Each measurement is sensitive to various effects Using a redundant set of measurements will allow the isolation of the

necessary components

K. Barish

Color Glass Condensate (CGC) Gluons

High density limit low-x forward rapidity

Calculable regime of gluons at high density but weak coupling– Nuclear Amplification

xGA~A1/3xGp

Gluon saturation: characterized by Qsat

Predictions– Suppression

» Low-x or forward η» More central

“Suppression” of away side jet

Low –x is key20

x

Q (GeV)1

10-1

10-3

10-2

10-4CGC

1 10 100

Central Arms Y~0

fsPHENIXY=1-4

move boundaryby changing Centrality toMap out QS

QS ~1-2GeV @RHIC

QCD~220 MeV

Prediction;Suppression :Low-x or forward ηMore central

xG(x)

xSaturation

K. Barish

Connection with TMDs? Problem: TMD factorization violated for dijet

production in hadron+hadron collisions– Solution: Get back effective TMD factorization in case of

small x partons at high density (“CGC regime”) – probed by quark, or photon

Problem: TMD parton distributions not universal– Solution: they can be constructed for building blocks which

ARE universal.» e.g. Gluon PDF G(1)(x,q^), G(2)(x, q^)» quantities derived via CGC and via TMD identical

Equivalence between TMD and CGC approach in “CGC” regime

» Connections to TMD’s in spin? xpfq(xp)

xG(2)(x,q^)

Þ Measure : photon-jet & dijets at low-x in d+Au

Domingues, Marquet, Xiao, Yuan arXiv:1101.07152v2, PRL 106, 022301

K. Barish

Heavy-ions (Au+Au)

3D “image” of medium– At mid-rapidity only see only

the evolution/final state of the “slice” of the fluid which is initially at rest longitudinally.

– Make flow measurements in forward direction.

Forward photon measurements– Information on system

expansion / early evolution.– Access to high baryon

density region.

T. Renk, PRC71, 064905(2005)

Bjorken: boost-invariant expansion

Landau: complete initial

Talk by P. Stankus

K. Barish 23

PHENIX Design

K. Barish

MuID

RICH

HCalEMCal

Tracker

EMcal

Hcal

2T Magnet

sPHENIX Conceptual Design

*Not to scale

K. Barish

Mid Rapidity Region

Ali Hanks talk Tuesday Full 2p coverage Electromagnetic and Hadronic

calorimetry 2T Solenoidal Field VTX detector for central tracker

Also allow heavy quark jets Primary (initial) focus of jet and

di-jet measurements in HI Designed to include possible

upgrade path: additional tracking, EID, ePHENIX

Will take full advantage of RHIC’s flexibility: d+A, Cu+Au, U+U, etc.

K. Barish

Forward Region

Rely on central magnet field Studying other field/magnet

possibilities EMCal based on restack of

current PHENIX calorimetry PbSc from central arm (5.52

cm2) MPC forward arm (2.2 cm2)

For tracker considering GEM technology

Interest of HI in forward direction may influence choices based on expected multiplicity.

PbSc restack

=12x12 towers1 tower is 5.5cm2

MPC restack

= 2.2cm2

K. Barish

Outlook

sPHENIX Forward will significantly extend physics capabilities With new Forward Detector, will be able to understand large

SSA, separating contributions from Sivers and Collins. Forward Detector will also provide calibration for quarkonium

measurements and probe CNM effects in d+A (connections with CGC and TMDs?)

Potential exists to explore 3D image of medium in Au+Au Workshops planned. Multiple funding sources pursued. Staged implementation approach

Drell-Yan/Quarkonia needs only EMCal, charged particle ID, and charge sign

Then add jet followed by identified hadron capabilities. The sPHENIX forward would also be well matched with

ePHENIX.

K. Barish

Backups …

K. Barish

Drell-Yan Feasibility

 

K. Barish

Towards eRHIC

R [cm]

100

6070

EMCal

PID

Inner Tracker

Outer tracker

Additional tracking

as needed

MagnetImmediate focus:

Make sure sPHENIX concept of barrel consistent with upgrade plans for ePHENIX physics

sPHENIX central arm proposal (CD0) to be submitted on Jul 1, 2012

Is EMCal resolutions good enough?

Enough space for PID?

Momentum range for PID

Material budget limitation for tracking

Minimal configuration/requirements: Backward: electrons, photonsBarrel: electron, photons, hadronsForward: hadronsRoman Pots for forward protons

e- p/A

Forward Backward

Barrel cross section diagram