Spin Physics with Muons

Ming X. Liu

Los Alamos National Lab

–Physics Motivations–Highlight of Baseline Physics

• Run3 and Beyond

–New Development

• Proton Spin - a major puzzle from polarized DIS experiments– Proton Spin Decomposition

• Origin of Proton Spin: – gluon, sea quarks, orbital angular momentum ? – DIS can’t directly probe gluons and anti-quarks

• Need a new tool : RHIC-SPIN– a polarized proton collider– quark-gluon, quark-quark and gluon-gluon interactions– directly explore gluon and sea quark distributions

04.031.0

gqLG 2

1

2

1

Experimentally

RHIC-Spin PhysicsRHIC-Spin PhysicsNew Frontier of Nucleon Structure ResearchNew Frontier of Nucleon Structure Research

RHIC-Spin PhysicsRHIC-Spin PhysicsNew Frontier of Nucleon Structure ResearchNew Frontier of Nucleon Structure Research

The Experiment• Polarized Protons at RHIC

– E_cm=50 - 500 GeV– Pol=70%– L=2x10^32 cm^-2sec^-1

• Particle Detectors– PHENIX et al

• Physics Studies– Nucleon Spin Structure

• Gluon distribution• Quark distribution

– New Physics

Experimental Observables

)()()()(

)()()()(

L

LL

A

A

• Asymmetries

)()(

)()(

)()(

)()(

T

TT

A

A

What do we learn from such measurements ?

• Asymmetries

• Polarized Quark and Gluon Distributions - LO

• Proton Structure– QCD dynamics

dt

dQxfQxf

dp

dE

cdab

bbBa

aA

),(),( 22

3

3

1

0)(

)()()(

dxxff

xfxfxf

Gluon Polarization and Heavy Quarks

• Heavy Quark production at 200 GeV

• Distinct Experimental signatures– high Pt lepton

– 2nd vertex

• Large asymmetry and pQCD

%85:

%95:

bbggbb

ccggcc

)(),(),( 223

3

zDdt

dQxFQxF

dp

dE

M

X

cdab

bbBa

aA

X

QCDQ

ˆ

ˆ

)(

)(

)(

)(

2

2

1

1 partonLL xG

xG

xG

xGA

1.12

ˆ

M

s

1.5

2

5

ALL

Heavy Quark and Quarkonium @PHENIX

• Exp. Signatures– full reconstruction

• D -> kπ• J/Psi -> μ+μ-

– semi-leptonic decay• BR ~10% (c, b)

– charge correlation– Long lifetimes*

• 2nd VTX (Upgrade Plan)

• A common device in Coll. Exp’s

b cW-

-

s

W+

+

Jet

leptonPt

VTX

IP

b_b

Expectations from Y03: ΔG

PB=30%, 1k J/Psi

– 30%

• 1st longitudinally polarized p-p collisions @200GeV

• L=0.35 /pb; pol =30%

Single Muon Pt J/Psi Pt

ALL from muons

Sea Quark Polarization & Flavor Asymmetry

)()(

)()(?

xdxu

xdxu

• Nucleon is a complex system• Sea quarks and gluons correlated• QCD dynamics

LANL/E866

)()(

)()(?

xuxd

xuxd

Quark and Anti-Quark Polarization

Bunce G. et al, hep-ph/0007218

Physics Beyond the SM with Polarized Beams

Novel ideas for new physics search– Spin Asymmetry - advantage over

traditional unpolarized beams

– SUSY search• Light glunio hypothesis

]1,1[:)ˆ

()~~,(:

1)(:

M

sFggbbggaSUSY

bbggaSM

LL

LL

)}()({)}()({)}()({)}()({

LLA

g

g

)~(gb

)~(gb

PRL 86, 4231(2001)

g

1.12

ˆ

M

s

1.5

2

5SM: QQbar

SUSY

LLa

Study J/ Production Mechanism

- J/Psi polarization - a key probe?- Spin dynamics in pQCD

*cos1*cos

2

d

d

α= +1: transversely polarizedα= -1: longitudinally polarizedα= 0: no polarization

+J/

*-

hep-ph/0106120 M. Kramer

Asymmetries from J/Psi

PRD 56 (1997)A. Tkabladze &O. Teryaev PRL 87 (2001) F.Yuan & K. Chao

ALL Asymmetry J/Psi Polarization

Summary• Muons from polarized p-p collisions

– A unique tool to study:• polarized gluon and sea-quark distributions• pQCD/NRQCD factorization model• heavy quarkonia production mechanism

– QGP probe?– a new tool for physics beyond the Standard Model

• VTX + muon –> “B” physics

• Expectations from Y03 p-p run– statistically limited for pol. measurements – open charm and beauty X-sections are possible

• Very rich physics program in coming years (2005+)– Polarization

– Spin asymmetry• Pol PDF

),...,/|,(boundFT QQPsiJXPf

),|,,(

,..),|,(

),...,/|,(

ˆ2 bbccXPfA

bcXPfA

QQPsiJXPfA

SM

FTLL

FTLL

boundFTLL

...);;/(2

bcJdydP

d

T

Heavy Quark Production and G(x)

• Gluon’s x range

protonx1P

CentralArm

Muon Armx2P

ｂ→ eｂ→

CentralArm

ｂ→ｂ→ e

Gx

Muon Probe @PHENIX

• Heavy quarks– Open Charm/Beauty– Quarkonium, DY

• Light hadrons– Kaon, Pion

• W,Z decays• Hard probes

– pQCD and Factorization– LO/NLO – Spin : soft ? Hard?

– QCD– CC– BB

Muon Pt

“Muon” as a hadron tag - turn background into signal -

• Low Pt pi/kaon decay– ~0.2% pi->mu

• Punch through hadrons (pions)– ~0.6% pi->pi, tagged by MUID

• Large statistics

Pt Pt