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Measuring Orbital Angular Momentum through Jet kT

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University of New Mexico/RBRC. Jan Rak, Rob Hobbs, Imran Younus. 6/2/2005. Douglas Fields ... Where, is the product of the Jacobian and the density profile of ... – PowerPoint PPT presentation

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Title: Measuring Orbital Angular Momentum through Jet kT


1
Measuring Orbital Angular Momentum through Jet kT
  • Douglas Fields
  • University of New Mexico/RBRC

Jan Rak, Rob Hobbs, Imran Younus
2
Basic Picture
  • Idea came from me trying to understand Sivers
    effect
  • Quantum Fan Level Description
  • This is a double spin asymmetry
  • This is for longitudinally polarized protons
  • Rotating partons around spin direction
  • Two classes of collisions
  • Like helicity, i.e.,
  • Un-like helicity, i.e.,

3
Like Helicity(Positive on Positive Helicity)
Measure jet
Integrate over b, left with some residual kT
4
Un-like Helicity(Positive On Negative Helicity)
Integrate over b, left with some
different residual kT
5
History
  • Talked to many people Werner pointed me to a
    paper by Meng Ta-chung et al.
  • Experiment B similar idea, only for Drell-Yan

6
From Meng Ta-Chung et al.Phys Rev. D40, p769,
(1989)
kTR
kPR
7
From Meng Ta-Chung et al.Phys Rev. D40, p769,
(1989)
Like Helicity
kTR
kPR
Un-like Helicity
kPR
kTR
8
From Meng Ta-Chung et al.Phys Rev. D40, p769,
(1989)
  • This paper makes the following assumptions
  • Uniform spherical density F(b,?P,?T)
  • kPRkTRkR (no dependence on b, ?P, ?T.)
  • Then,

Evaluated numerically
9
How Large an Effect Can We Expect?
10
Pause For Feedback
  • Need theoretical guidance!
  • Would be nice to have experimental handle on
    impact parameter
  • Multiplicity
  • Forward or central
  • Underlying event
  • but, not explicitly necessary.

11
How do we measure kt?
  • ?0 - h? azimuthal correlation functions

Trigger ?0
Intra-jet pairs angular width ?N ? ?jT?
Inter-jet pairs angular width ?A ? ?jT? ? ?kT?
12
PHENIXDetector Overview
  • East Arm
  • tracking
  • DC, PC1, TEC, PC3
  • electron hadron ID
  • RICH,TEC/TRD,
  • TOF, EMCal
  • photons
  • EMCal
  • West Arm
  • tracking
  • DC,PC1, PC2, PC3
  • electron ID
  • RICH,
  • EMCal
  • photons
  • EMCal

13
p0 Identification
  • PHENIX has central arm EMCal with electron
    rejection in RICH.
  • Used shower profile cut.
  • Good S/B at higher pt (gt2GeV).

14
Charged Particles
  • Tracks in the Drift Chamber
  • Hits in the Pad Chambers
  • RICH veto for low momentum
  • Shower shape cut at high momentum

15
Correlation Functions
  • dNreal ?f distribution from particles in the
    same event
  • dNmixed ?f distribution from particles in
    different events with similar vertex position
  • Norm
  • Fit to two gaussians plus a constant term

1.5ltpTlt2.0
Fit const Gauss(0)Gauss(??)
3.0ltpTlt4.0
Intra-jet pairs angular width ?N ? ?jT?
Inter-jet pairs angular width ?A ? ?jT? ? ?kT?
16
Jet Kinematics
17
How accurately can we measure ltktgt?
  • is extracted from and
    fragmentation functions which are extracted from
    the inclusive distributions.

18
How accurately can we measure ?ltktgt?
  • ZT uncertainties should cancel in the difference
  • Bunch Shuffling in Run3 (PHENIX)
  • d ?ltktgt 80MeV

19
For Run5
  • 10-20 times more statistics than Run3
  • Statistical errors smaller by factor of 3-5
  • Polarization in Run5 55
  • Effect larger by factor of 5 (PYPB) than Run3

20
Summary
  • We can make a measurement of the
    double-longitudinal spin dependence of jet ltkTgt.
  • This may be sensitive to orbital angular
    momentum.
  • These effects (if really there) may also
    influence the double-longitudinal cross-section
    asymmetry.
  • Need theoretical guidance
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