Possibility of direct extraction of the transversitiy from polarized Drell-Yan measurement in COMPASS

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Possibility of direct extraction of the
transversitiy from polarized Drell-Yan
measurement in COMPASS
Workshop on Hadron Structure at J-PARC, November
30 - December 2, 2005             KEK, Tsukuba,
Ibaraki, Japan
T.Iwata ( Yamagata University) on behalf of
COMPASS collaboration

• Transversity
• Drell-Yan for transverstiy
• transverse momentum dependent PDFs
• polarized Drell-Yan
• idea of the Drell-Yan measurement in COMPASS
• requirements to the apparatus
• summary

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Transversity
Nucleon quark structure completely described by
3 distribution functions ( at twist 2
level)
longitudinal

1. momentum distribution
2. helicity distribution
3. transversity distribution

transverse

• transversity has never
• been determined
• in experiments

• accessible in SI-DIS with transversely
  polarized targets
• data available from HERMES, COMPASS, J-Lab
• need polarized fragmentation functions ( not
  well known)
• study ongoing in Belle

T.Iwata _at_ Workshop on Hadron Structure at J-PARC,
Nov. 30 Dec. 2, 2005, KEK
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Drell-Yan for Transversity
Drell-Yan is alternative way to access
transversity
Advantage no need of any fragmention functions

• double polarized Drell-Yan

allows direct extraction of transverstiy
Possible
GSI


But, a big challenge experimentally
T.Iwata _at_ Workshop on Hadron Structure at J-PARC,
Nov. 30 Dec. 2, 2005, KEK
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Single polarized Drell-Yan

• single polarized Drell-Yan

less difficut experimentally
COMPASS setup
COMMON Apparatus for muon hadron programs

• Unique environment of COMPASS
• polarized target
• hadron beam
• high rate trackers
• muon identification

Polarized target long. trans. pol

• Two stages
• RICH
• High rate trackers
• Ecal, Hcal
• Muon filters

Beam muon hadrons(p/p)
Transversity accompanied with T-odd PDF ( one
of the transvese momentum dependent PDFs)
A.Sissakian et al., Phys. Rev. D72, 054027 (2005)
T.Iwata _at_ Workshop on Hadron Structure at J-PARC,
Nov. 30 Dec. 2, 2005, KEK
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Transverse momentum dependent PDFs
Nucleon
unpol.
long. pol.
trans. pol.
number density
Sivers
unpol.
Nucleon
T-odd
Parton
helicity
long. pol.
Quark
transversity
Boer-Mulders
survive after integration over kT
trans. pol.
T-odd
T.Iwata _at_ Workshop on Hadron Structure at J-PARC,
Nov. 30 Dec. 2, 2005, KEK
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Unpolarized-Drell-Yan
How to extract transversity in DY
measurement? The ider is based on
A.Sissakian et al., Phys. Rev. D72, 054027 (2005)
unpolarized Drell-Yan case
qT weighted angular distribution (qT transvese
momentum of virtual photon)
lepton pair CM frame
V.Barone et al., Phys. Rep. 359 (2002)1-168
T.Iwata _at_ Workshop on Hadron Structure at J-PARC,
Nov. 30 Dec. 2, 2005, KEK
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Coefficient of COS2f term
Boer-Mulder PDF(T-odd) for anti-q in p
Boer-Mulder PDF(T-odd) for q in proton
1st moment of the PDFs
number densities (well known)
T.Iwata _at_ Workshop on Hadron Structure at J-PARC,
Nov. 30 Dec. 2, 2005, KEK
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Single Spin Asymmetry
single polarized Drell-Yan case
qT weighted single spin asymmetry for
azimuthal angle of the target spin vector
target spin vector
Boer-Mulder PDF(T-odd) for anti-q in p
transversity
T.Iwata _at_ Workshop on Hadron Structure at J-PARC,
Nov. 30 Dec. 2, 2005, KEK
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Simplidied equations
neglect s-quark, sea quark in proton, and d-quark
contributions (d-quark originally suppressed due
to its charge)
expressions with only u-quark PDFs
given from
Boer-Mulder PDF(T-odd) for anti-u in p
transversity
known
transversity
known
to be extracted
T.Iwata _at_ Workshop on Hadron Structure at J-PARC,
Nov. 30 Dec. 2, 2005, KEK
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Extraction in single exp. I
Additonal assumption based on Boers model
Phys.Rev. D60, 014012 (1999)
E615 _at_ Fermilab
Phys. Rev. D39 (1989) 92
anomalously large cos2f dependence observed
Naive Drell-Yan thery predicts
pQCD (LO,NLO) not explained it
Boers Model explained it with transverse
momentum dependent PDF (at LO)
T.Iwata _at_ Workshop on Hadron Structure at J-PARC,
Nov. 30 Dec. 2, 2005, KEK
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Extraction in single exp. II
With the assumption, the observables are
rewritten only with the PDFs for proton
unknown PDFs
Boer-Mulder PDF (T-odd) for proton
at the point
transversity
T.Iwata _at_ Workshop on Hadron Structure at J-PARC,
Nov. 30 Dec. 2, 2005, KEK
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Counting rate in COMPASS

• Beam 100 GeV p-
• Target 60 g/cm2 NH3
• Luminosity
• Cross section value
• Acceptance
• Expected rate for DY
• Thus 0.08 events/spill (4000 spills/day)
  ? 320 events/day
• Total statistics (SPS eff80) 120 days ? 30k
  events/year

Very preliminary!
T.Iwata _at_ Workshop on Hadron Structure at J-PARC,
Nov. 30 Dec. 2, 2005, KEK
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Comparison of running conditions
current condition Drell-Yan
beam pol. m 160 GeV p - 100 GeV
intensity 2x108m/spill(4.8s)(4.2x107m/s) 4.8x108 p- /spill(4.8s)(1.0x108 p- /s)
pol. target 6LiD 60 g/cm2 (NH3 60 g/cm2 in 2006 ) NH3 60 g/cm2
polarization mode longitudinal transverse transverse
total event rate 105/s 1x108/s
charged hadrons/event 4 6
current condition with m beam
Drell-Yan with p beam
T.Iwata _at_ Workshop on Hadron Structure at J-PARC,
Nov. 30 Dec. 2, 2005, KEK
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Requirements to the apparatus

• Spectrometer
• high rate capability required ( for trackers
  near the target)
• upgrading SciFi, GEM, Micromegas
• no need of complete particle ID(only muon ID
  with muon filters)
• Polarized target
• ? heat load increase by x 10 ( 0.5mW,
  2mW/spill)
• runing in frozen spin mode( for transverse
  polarization)
• better cooling efficiency needed to maintain
  its polarization

T.Iwata _at_ Workshop on Hadron Structure at J-PARC,
Nov. 30 Dec. 2, 2005, KEK
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Improvements of PT
The dilution refrigerator can manage the heat
load (sufficient cooling power)
small beads or thin sheet
larger surface area
frozen spin mode
Maximum beam intensity vs. bead diameter
DNP mode
N.Doshita et al., NIM A 526 (2004) 138-143
Problem removing heat from the material
NH3 in SMC, (2006 COMPASS)
heat from target bead
? bottle neck Kapitza resistance
Relaxation time(NH3) T1400 hours _at_ 60mK, 0.4T,
T.Iwata _at_ Workshop on Hadron Structure at J-PARC,
Nov. 30 Dec. 2, 2005, KEK
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Summary

• Drell-Yan process is a powerful tool to study
  the
• transverstiy and the accompanying T-odd kt
  dependent
• PDFs.
• COMPASS offers unique environment for the single
  plarized
• Drell-Yan measurement.
• The design of the measurment is underway in
  COMPASS
• collaboration.
• Requirements to the apparatus were shown in
  this talk.

T.Iwata _at_ Workshop on Hadron Structure at J-PARC,
Nov. 30 Dec. 2, 2005, KEK
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Backup slides
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Boers Model
Phys.Rev. D60, 014012 (1999)
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given from
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Accessible kinematics in COMPASS