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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
04/18/23 Ming X. Liu INT Workshop 4
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
04/18/23 7Ming X. Liu INT Workshop
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
04/18/23 9Ming X. Liu INT Workshop
TSSA in Charm Production at Low Energy (I)
• Low energy • Initial state interactions
• Final state interactions
04/18/23 Ming X. Liu INT Workshop 11
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
04/18/23 12Ming X. Liu INT Workshop
q q cc
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:
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ccggcc
%85:
%95:
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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
04/18/23 15Ming X. Liu INT Workshop
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 ..
04/18/23 16Ming X. Liu INT Workshop
Experimental Prospects
• RHIC – @high energy• Other facilities @low energy
– JPARC– GSI/FAIR– Fermilab– EIC
04/18/23 17Ming X. Liu INT Workshop
Open Charm Production in p+pwith PYTHIA (LO)
04/18/23 18Ming X. Liu INT Workshop
E906
RHIC 62GeV
JAPRC
RHIC 200 GeV
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
04/18/23 20Ming X. Liu INT Workshop
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…
04/18/23 30Ming X. Liu INT Workshop
Charm TSSA @EIC
• Open charm• J/Psi• Need model
calculations
04/18/23 Ming X. Liu INT Workshop 31
Kang and Qiu PRD (2008)
EIC: J/Psi TSSA (I)• TSSA could be closely connected to J/Psi production
mechanismsF. Yuan PRD 70, 074025
04/18/23 32Ming X. Liu INT Workshop
New Idea: High Luminosity Polarized Fixed Target p+p?
• Drell-Yan• Open charm@ low √s
04/18/23 Ming X. Liu INT Workshop 34
Ming X. Liu Seminar@UNM 35
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
Ming X. Liu Seminar@UNM 36
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
Ming X. Liu Seminar@UNM 37
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
04/18/23 38Ming X. Liu INT Workshop
04/18/23 Ming X. Liu INT Workshop 40
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
Ming X. Liu Seminar@UNM 4141
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
Ming X. Liu Seminar@UNM 42
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
Ming X. Liu Seminar@UNM 43
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
Ming X. Liu Seminar@UNM 46
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