Study of the gluon polarization in the proton with a silicon vertex upgrade at RHICPHENIX'

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Study of the gluon polarization in the proton
with a silicon vertex upgrade at RHIC/PHENIX.

• Manabu Togawa,
• Kyoto University / RIKEN
• for the PHENIX collaboration

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Base line of spin program at PHENIX

• Polarized parton distribution in proton.
• (longitudinal polarization)

- Gluon polarization

• pion / hadron ( ref. p0 Y.Fukaos talk )

• prompt photon

• heavy flavor
• Single e ( D -gt e X)
• J/Y

- Anti-quark polarization

• W? (required sqrt(s) 500GeV )

• Transversity (transverse polarization)

• pion pair

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With VTX tracker (Barrel part)

• PHENIX Vertex Tracker (VTX) will be installed in
  Summer of 2007.

• Reconstruction of the jet axis
• Using charged particles in wide rapidity coverage

• Access to the displaced vertex -heavy flavor
  tagging
• VTX can know the detail of collision point.
• Looking at the gap between decay and collision
  point.

Beam pipe
Barrel (hlt1.2 and 2p azimuthal coverage)
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VTX takes advantage of PHENIXfor gluon
polarization

M.Karliner and R.Robinett. Phys. Lett. B324 (1994)
LO analyzing power
1.1
1.5

• Prompt photon
• Determine xg,xq
• Heavy flavor production
• Separate charm and beauty by looking at their
  life time. For D and B meson, tD lt tB
• We must separate charm and beauty for gluon
  polarization since analyzing power is different.

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low pT higher mass
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cosq
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Current PHENIX setup (for prompt photon)
Central ARM hlt0.35 0ltfltp
Prompt photon process (main gluon compton
process 90)
Prompt photon
- We measure the inclusive photon production.
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Jet reconstruction with VTX (For prompt
photon)using pythia simulation
known by EMCal
g (Eg)
qg
q (x1,p)
g (x2,p)
qjet
q (Ejet)
qjet reconstruct by charged particles
using Cone algorithm.
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Current PHENIX setup (for heavy quark)
in CENTRAL ARM
Central ARM hlt0.35 0ltfltp
c quark D -gt e (anything) D -gt pK J/Y -gt
ee-
pK(D) or ee-(J/Y)
b quark B -gt e (anything) B -gt J/Y X
single electron
(main gluon fusion 90)
In single electron analysis

• back ground.
• p0, h Dalitz decay
• g conversion ( g -gt ee-)

• We can not separate electron
• from D and B (J/Y too).

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Displaced vertex ( For Heavy production )
Black charged particles from
collision point Blue electron from D or B

• The gap btw decay point and collision can be
  evaluated with DCA.
• Distance of Closest Approach.
• DCA of D and B meson are different.
• We can separate them.

Azimuthal angle
Studied by tuned pythia
For example cut
DCA (mm)
Vladimir L. Rykov
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How to separate D and B
Fraction of electron source
With DCA cut
no DCA cut
Red DalitzConversion Green Charm Blue
Beauty
pT
No DCA cut eall(no DCA cut) eDalitz eD
eB With DCA cut eall(DCA cut)
Rdalitz(pT) eDalitz RD (pT) eD RB (pT)
eB RXXX is electron ratio of no DCA cut to
DCA cut for xxx. (can be estimated by
simulation)
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Silicon detector
Junji Tojo
Hiroaki Ohnishi
Pixel detector
Strip detector (test)
test sensor design (Hamamatsu)
test hybrid module design (ORNL)

• ALICE hybrid
• PHENIX sensor delivered in this month
• electronics QA done
• to be bump-bonded in a month or so

SVX4 readout chip (Fermilab)
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Summary

• VTX is being built to extend capability for
  PHENIX experiment as an upgrade.
• VTX will extend the acceptance of charged
  particles
• to the hlt1.2 and 2p azimuthal coverage.
• VTX will be able to reconstruct jet direction.
• Determine xg,xq in the prompt photon process
• VTX will be able to determine the displaced
  vertex.
• Separate charm and beauty statistically.
• 320pb-1 will provide another test of
  ?g(x)
• We will have VTX detector in 2007 - 2008 RUN.

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Back up
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single electron charm ALL
NLO calculation
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DCA resolution

• DCA resolution is dominated most inner 2 layers.

DCA resolution
pT
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Jet reconstruction (For direct photon)
known by EMCal
Assuming that the pT of the prompt photon
and recoil jet are balanced.
g (Eg)
q (x1,p)
qg
g (x2,p)
qjet
q (Ejet)
qjet reconstruct by charged particles
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x value shift
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Gluon shadowing effect
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Cone Algorithm

• Apply pt cut and
• first cut pt gt 1.0 (GeV)
• Remaining particles (13 particles remain)
• calculate jet axis taking average
• ltetagt ltøgt -gt first jet
  axis
• Second cut
• Calculate cone radius R defined as
• apply second cut Rlt0.5 and pt gt1.0
• and calculate jet axis
• -gt go to second cut iteration

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Pythia parameters

• For charm
• Reproduce SPS,FNAL (charm) and ISR (single e)
• For bottom

Pythia parameters ltkTgt1.5 ltmcgt1.25
K-factor3.5 CTEQ5L
PHENIX PRL 88(2002)192303
NLO pQCD (M. Mangano et al., NPB405(1993)507)
PHENIX
ISR
Pythia parameters ltkTgt1.0 (default)
ltmcgt4.8 (default) K-factor2.6
GRV94D(NLL,DIS)
PYTHIA (single electron)
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Rapidity resolution vs.pt
Resolution (Qrapidity - JetRapidity)
pT
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Photon Jet

• PHENIX baseline
• prompt photon (inclusive)
• asymmetry ?
• gluon polarization
• photons pT ? xg

?s200GeV, 320pb-1
prompt photon pTgt5GeV/c
rough xg evaluation ?
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Transversity

• Inclusive prompt-photon measurement
• Laenen, Sterman Vogelsang
• threshold resummation
• necessary to sum up all kinematics of
  opposite-side jet
• kT resummation
• Photon jet
• threshold resummation
• should not be necessary
• kT effect
• E706