Probing the Color Gauge Link via Heavy Quark TSSA in p+p Collisions Ming X. Liu Los Alamos National Lab INT Spin Workshop 11/2010 A new Experimental Test

Probing the Color Gauge Link via Heavy Quark TSSA in p+p Collisions

Ming X. LiuLos Alamos National Lab

INT Spin Workshop 11/2010

A new Experimental Test of color dynamics in hard scattering

- TSSA for Open (anti)charm, J/Psi and DY- Test color structures for quark and anti-quark- Experimental opportunity: RHIC and other future Exp’s

An experimentalist’s point of approach

04/18/23 Ming X. Liu INT Workshop 2

Drawing from D. Sivers @Santa Fe Polarized Drell-Yan Workshop Dinner 10/31-11/1, 2010

Color Flow in DY and DIS• The sign change – a new fundamental test of color gauge formalism• Charm TSSA could provides a new independent experimental test

of the underlying physics

Twist-3: sign change from gluonic-pole in hard parts

In the overlapped region – consistent description

04/18/23 3Ming X. Liu INT Workshop

Collins ‘02

Ji, Qiu, Vogelsang, Yuan ‘06Bacchetta, Boer, Diehl, Mulders ‘08

Nice things about heavy quarks

• Experimentally tag Fermion and anti-Fermion

• Theoretically “clean” to use pQCD– MQ >> ΛQCD

– Hard fragmentation


Ming X. Liu INT Workshop 5

Do we understand the physics?The Challenge of “Too Large”

PRD65, 092008 (2002)

PRL36, 929 (1976)

ZGS 12 GeV beam

AGS 22 GeV beam

FNAL 200 GeV beam

PLB261, 201 (1991)PLB264, 462 (1991)

RHIC 20,000 GeV beam

Non-Perturbative cross section Perturbative cross section

PRL (2004)

Large Transverse Single Spin Asymmetry (SSA) in forward meson production persists up to RHIC energy.

04/18/23

Color Interaction and TSSA• Do we understand the underlying physics?

– the Sivers asymmetry, for example • What can we learn more from future data?

– DY, charm, direct-photon…

We are colliding hadrons, not partons!04/18/23 6Ming X. Liu INT Workshop

Gamberg, Kang 2010

Generalizing GPM… with modified hard cross sections (gluonic-pole cross sections)PRL 99 (2007) A. Bacchetta et al, PRD 72 (2005) A. Bacchetta, C.J. Bomhof, P.J.Mulders, F.Pijlman


Charm and anti-Charm TSSA and Color Structure

• Quark and anti-Quark have different color structure in hard scatterings

• Experimentally Charm and anti-Charm can be cleanly identified,

• AN(charm) provide new insight to the underlying physics of TSSA– Directly test the different color structure for quark and anti-quark

AN (c) : c X

AN (c ) : c X

AN (c)?

AN (c )

04/18/23 8

A new clean experimental test of the color couplingto quark vs antiquark in hard scatterings!

Ming X. Liu INT Workshop

TSSA in Heavy Quark ProductionKang, Qiu, Vogelsang, Yuan, PRD 2008



Open Charm TSSA in Twist-3 Approach

TSSA in Charm Production at Low Energy (I)

• Low energy • Initial state interactions

• Final state interactions


q q cc F. Yuan and J. Zhou PLB 668 (2008) 216-220

Heavy Quark TSSA at Low Energy (cont.)Twist-3 quark-gluon correlation fun.

• Different color factors for charm and anti-charm

~1

2NC2

~NC

2 2

2NC2

~2

2NC2

Charm anti-CharmInitial state

F. Yuan and J. Zhou PLB 668 (2008) 216-220


q q cc

AN : q q c(c ) XJPARC p+p

GSI: p+pbar


14

• Sensitive to gluon Sivers function * probe gluon’s orbital angular momentum?

-- Minimize Collins’ effects * heavy flavor production dominated by gluon

gluon fusion at RHIC energy Pythia 6.1 simulation (LO)

* gluon has zero transversity

• Tri-gluon correlation functions

• Also sensitive to J/ψ production mechanisms and QCD dynamics

%85:

%95:

bbggbb

ccggcc

%85:

%95:

bbggbb

ccggcc

Heavy Flavor TSSA @RHIC

Open Charm

Johann Riedl, SPIN2008

Heavy Quark SSA at High Energy (II)Twist-3 tri-gluon correlation

• Consequence of different color factors for charm and anti-charm

Kang et al 2008Koike et al 2010


g g c c

The Physics GoalsExperimental Study of the Color Flow via Open Heavy Quark TSSA

• Current understanding of TSSA based on the color gauge invariant QCD formalism– Twist-3, modified GPM … – Expect significant difference between AN(c) and AN(c-bar)

• The process dependence of TSSA can be tested experimentally– DY vs DIS– Charm (quark) vs anti-charm (anti-quark)– Other processes ..


Experimental Prospects

• RHIC – @high energy• Other facilities @low energy

– JPARC– GSI/FAIR– Fermilab– EIC


Open Charm Production in p+pwith PYTHIA (LO)


E906

RHIC 62GeV

JAPRC

RHIC 200 GeV

Charm Production p+p @200GeV

• At low pT, g+g dominates


LO NLO

More on Open Charm Production• Fixed targets vs NLO • Collider mode @RHIC

PRL 95, 122001 (2005) M. Cacciari, P. Nason, R. VogtEPJ C 52, 987 (2007) J. Riedl, A. Schafer, M. Stratmann


21

D meson production dominated by gluon-gluon fusion at RHIC energy

Sensitive to gluon Sivers effect AN measured for muons from D decay

Smear by decay kinematics

Anselmino et al, PRD 70, 074025 (2004)

Gluon Sivers=0

Gluon Sivers=Max

Calculations for D mesons

Measurement for -

D (-)

Forward Open (anti)Charm AN

22

TSSA and J/Ψ Production J/ψ TSSA is sensitive to the production mechanisms Assuming a non-zero gulon sivers function, In pp scattering, TSSA vanishes if

the pair are produced in a color-octet model but survives in the color-singlet model

Feng Yuan, Phys. Rev D78, 014024(2008)

One color-singlet diagramOne color-singlet diagram— no cancellation, asymmetry generated by the initial state interaction

Two color-octet diagramsTwo color-octet diagrams— cancellation between initial and final state interactions, no asymmetry

In Collinear higher twist approach, the relation is not quiet simple. There are partial but not full cancellation of terms.

Z. Kang

23

PHENIX Detector•Central Arm || < 0.35

Drift Chamber (DC) PbGl and PbSc Ring Imaging Cherenkov Detector (RICH) Pad Chambers (PC) Time Expansion Chamber (TEC)

•Global Detectors (Luminosity,Trigger)

BBC ZDC

•Muon Arms 1.2 < |η| < 2.4

Muon tracker (MuTr) Muon Identifier (MuID)

Year s [GeV] Recorded L Pol [%] FOM (P2L)

2006 (Run 6) 200 2.7 pb-1 51 700 nb-1

2008 (Run 8) 200 5.2 pb-1 46 1100 nb-1

e+

e-

μ+

μ-

24

J/ψ Measurements in the Muon and Central Arms

/JIn Muon Arm

ANIncl: oppositely-charged muon pairs in the

invariant mass range ±2σ around J/ψ mass.

ANBG: oppositely-charged muon pairs in the

invariant mass range 1.8 (2.0run8) < m <2.5 along with charged pairs of the same sign in invariant mass range 1.8 (2.0run8) < m < 3.6

In Central Arm eeJ /

BG subtraction: 2*sqrt{Ne+e+Ne-e-} Remaining continuum backgroundIs small, not enough statisticsAssuming: AN

BG=0

arXiv: 1009.4864

r

ArAA

BGN

InclNJ

N

1

./

25

Asymmetries were obtained as a function of J/Psi Feynman-x, with a value of -0.086 ± 0.026 (stat.) ± 0.003 (sys.) in the forward region.

X. Wang, SPIN2010, arXiv: 1009.4864

- Suggests possible non-zero tri-gluon correlation functions in transversely polarized protons.- If well defined in this reaction, the results suggests non-zero gluon Sivers distribution functions.

J/ψ AN at Forward Rapidity

26

NRQCD and J/ψ Production

Theoretical predictions of J/Ψ production at RHIC are in good agreement with the PHENIX data: COM process dominant◦ PRD 68 (2003) 034003 G. Nayak, M. Liu, F. Cooper◦ PRL 93 (2004) 171801 F. Cooper, M. Liu, G. Nayak

PHENIX, PRL 92, 051802 (2004)

27

NRQCD and J/ψ Polarization

NRQCD failed on J/NRQCD failed on J/ψψ polarization. polarization.J/J/ψψ production mechanism is still an open question. production mechanism is still an open question. Very active field of theoretical study…Very active field of theoretical study…

Near Future ProspectsPHENIX Silicon VTX Upgrades: by 2011

Ming X. Liu Seminar@UNM 28

• Precision Charm/Beauty Measurements• BJ/, Drell-Yan, ’

Drell-Yan prompt

10/26/10

Charm SSA to Probe Gluon Sivers Distribution

29

Kang, Qiu, Yuan, Vogelsang, Phys. Rev. D 78,114013(2008)

D meson Single-Spin Asymmetry:

• Production dominated by gluon-gluon fusion

• Sensitive to gluon Sivers distribution• PHENIX-2006 data ruled out the max. gluon Sivers

• Much improved results expected with VTX detectors

AN

AN (c) ?

AN (c )

Ming X. Liu INT Workshop04/18/23

A few Observations and Comments• Twist-3 and Generalized TMD Parton Model

– Color gauge approach

• Quark sector: some knowledge– Quark Sivers and Collins functions– Twist-3 quark-gluon correlation functions

• Gluon sector: largely unknown– Gluon Sivers function(s)??– Twist-3 tri-gluon correlation functions

• Next experimental step for p+p – Heavy quark probe!– Directly access the color charge coupling to quark and anti-quark– Multi probes in a wide kinematic range – High luminosity polarized fixed target Drell-Yan and Charm experiment?

• It is all about the color flow in hard scattering– TSSA @RHIC-SPIN– p/d+A @RHIC – Jlab-12, EIC…


Charm TSSA @EIC

• Open charm• J/Psi• Need model

calculations


Kang and Qiu PRD (2008)

EIC: J/Psi TSSA (I)• TSSA could be closely connected to J/Psi production

mechanismsF. Yuan PRD 70, 074025


EIC: J/Psi SSA (II)

• Color octet channel


New Idea: High Luminosity Polarized Fixed Target p+p?

• Drell-Yan• Open charm@ low √s



Example (I): E906 Drell-Yan

Polarized DY possibility:• Polarized targets • Polarize the Main

Injector • Or both• 120 GeV proton beam

4.9m

XBeam

XTarget

10/26/10


UVA/J-Lab/SLAC Polarized proton/deuteron target

• Polarized NH3/ND3 targets• Dynamical Nuclear Polarization • Operate at 5 T and 1 K. Pol ~ B/T• Used with high beam intensities –

up to ~100 nA• Large capacity pumps• Polarizations:

– p > 90%, – d ~ 50%

• Able to handle high luminosity – up to ~ 1035 (Hall C)

~ 1034 (Hall B)

D. Crabb MENU10

10/26/10


Expected DY AN Sensitivity @120 GeV.

Target- 6 cm NH3

- 1019 proton

10/26/10

Also open charm and J/psi

Summary and Outlook• Experimental confirmation (or disproval) of color

flow dynamics in hard scattering is a critical step toward understanding the mechanisms of SSA• Drell-Yan• Charm vs anti-Charm

• Future experimental prospects – exciting opportunity!– RHIC, high energy – EIC– Polarized fixed targets, low energy


Backup



Critical Role of VTX/FVTX for Drell-Yan and Open Charm

• Tracking muons with MuTr+FVTX– Prompt muons from DY– Displaced tracks from π/K and heavy

quark decays

Drell Yan

beauty

charm

combinatorial background

DCA < 1 σ cut: Increase DY/bb ~ 5

ϒ-states

J/Ψ

Drell Yan

char

m beauty

DY: 4 GeV < M < 9 GeV; B-background: use FVTX


Example (II): Polarized DY w/ Fixed Target @RHIC ?

Polarized fixed target DY exp. with extracted polarized proton beams:

PHENIX STA

R

BRAHMS

Fixed Target DY Exp.

@Beam Dump

1. High density LH2/LD2 target

2. High density polarized targets

3 Map out x-dep.

- 250 GeV proton beams- Pol up to 70%

10/26/10


Fixed Target @RHIC ?• Beam dump experiment: dimuon channel

– Parasitic mode• Significant beams still left at the end of a store (~50%)• Cycle time ~8hr

– Dedicated fixed target• Cycle time ~ 1hr

– Dimu x-section @ 250 GeV (M>4) ~20pb

• Targets– E906-like unpolarized LH2 target

• 51cm LH2 (2.1x1024/cm2)• Can handle L ~ 1x1036cm-2s-1

– Polarized solid target• UVA/J-Lab/SLAC: L ~1035cm-2s-1

• Advantages– Polarized beams– (polarized) targets– Higher Energy and large x-coverage– High luminosity

10/26/10


DY AN Sensitivity @250 GeV Fixed Target

4.5<M<8 GeVqT < 1 GeV10 fb-1

50 fb-1

xF

10/26/10

Open charm at fixed target (cross section)

• Charm cross section by fixed target experiments are reasonably reproduced by LO pQCD event generator (PYTHIA) with large K-factor, or by NLO pQCD calculation (HVQMNR). Note that pQCD may or may not be applicable to charm production because charm mass is small (~1.5GeV)

• In the left figure, world pi+N data and p+N data are compared with PYTHIA calculation. The s1/2 dependence of the calculation mainly reflects the underlying PDF.

s1/2(GeV)

cc in pN,N

Charm production



Proton Efficiency: Collider vs Fixed Target Mode

• Design value: 2x1011x100 = 2 x 1013 proton per store per ring• Collision rate ~ 10 MHz

– Num. of collisions per store– 10M x 3600sec x 8 hr = 2.9 x 1010

– Fract. of p’s used = 3 x1011 / 2 x 1013 = 1.5 x 10-2

• In the fixed target mode, for a ~20% interaction length, we can use ~20% of the protons from the beam– 0.2/ 1.5 x 10-2 = 13x gain in luminosity

• Center of Mass Energies for p+p– Collider mode: sqrt(s) = 500 GeV– Fixted T mode: sqrt(s) = 22 GeV

10/26/10

Color Flow in Twist-3Kang @RBRC workshop 2010


Generalized Parton Model• Assume TMD factorization


Anselmino et al.

TMD factorization breakdown… a failure or an opportunity? Mulders, Xiao.. @RBRC workshop 2010

Documents

Probing the Color Gauge Link via Heavy Quark TSSA in p+p Collisions Ming X. Liu Los Alamos National Lab INT Spin Workshop 11/2010 A new Experimental Test