03/03/31 日本物理学会 1 hermes による横偏極水素標的を 用いた quark transversity...
TRANSCRIPT
03/03/31 日本物理学会 1
HERMES による横偏極水素標的を用いた quark transversity の測定
大須賀弘 , 田中秀和 , 宮地義之 , 柴田利明 , 他 HERMES Collaboration
東京工業大学柴田研究室
03/03/31 日本物理学会 2
OutlineOutline
•Transversity - What is the Transversity? - Motivation of the Transversity Measurement - How to Access the Transversity
• HERMES Experiment
( 27.6 GeV e+ + N Deep Inelastic Scattering)
• AUL(φ) Single-Spin Asymmetry and Transversity (analyzed)
• AUT(φ) Single-Spin Asymmetry and Transversity (in progress)
• Conclusion
03/03/31 日本物理学会 3
NotationNotation
Quark Number Density: q(x) F⇒ 1(x)
Quark Helicity: Δq(x) g⇒ 1(x)
Quark Transversity: δq(x) h⇒ 1(x)
introduced by Jaffe and Ji in their classificationPhys. Rev. Lett. 71 (1993) 2547
03/03/31 日本物理学会 4
What is the Transversity?What is the Transversity?
Quark Number Density: q(x)
q q xqexF )(
2
1)( 2
1
Quark Helicity: Δq(x)
q q xqexg )(
2
1)( 2
1
Quark Transversity: δq(x)
q q xqexh )(
2
1)( 2
1
03/03/31 日本物理学会 5
MotivationMotivation
The difference between helicity distribution Δq and transversity distribution δq ⇒ measure of the relativistic effects for quarks inside the nucleon
Relativistic Effects for Quarks inside the Nucleon
)()( xqxq for non-relativistic quarks
03/03/31 日本物理学会 6
Characteristics of TransversityCharacteristics of Transversity
• for relativistic quarks :
• transversity distribution CHIRAL ODD
• Bounds:
( Soffer Bound )
• q and q contribute with opposite sign to the transversity ⇒ predominantly sensitive to valence quark polarization
)()( xqxq )()(
2
1)( xqxqxq
)()( xqxq
03/03/31 日本物理学会 7
How to Access TransversityHow to Access Transversity
Collins Effect with Transverse Target
- Cleanest method is
- effect already visible using a longitudinally polarized target
1sin qHAUT
dAA UTUT )(sinsin sinφ moment :
)(UTAAzimuthal Asymmetry with Transversely Polarized Target :
U: Unpolarized BeamT: Transversely Polarized Target along Beam Direction
Azimuthal Angle :
the angle between lepton scattering plane and hadron production plane
)(1 zH : Collins Fragmentation Function (T-odd, Chiral odd)
03/03/31 日本物理学会 8
HERMES at DESY-HERAHERMES at DESY-HERA
• target: gas target in internal storage cell • PID: RICH, TRD, Preshower, Calorimeter
8 m
e+ beam
27.6 GeV
03/03/31 日本物理学会 9
Transversity Measurement at HERMESTransversity Measurement at HERMES
HERMES 1995-2000
HERMES 2002-
Longitudinally Polarized Target
Transversely Polarized Target
⇒ Quark Helicity Distribution: Δq ⇒ Glimpse on Quark Transversity Distribution: δq
⇒ Quark Transverse Distribution: δq
(analyzed)
(in progress)
03/03/31 日本物理学会 10
Azimuthal Asymmetry withAzimuthal Asymmetry withLongitudinal Longitudinal Polarized Target (analyzed)Polarized Target (analyzed)
Longitudinal Target Spin Asymmetry:
)()(
)()(1)(
NN
NN
PA
tUL
• significant sinφ dependence observed for π+ and π0
• sin 2φ moment consistent with zero for all pions
π0
π-
π+
π0 : Phys. Rev. D64 (2001) 097101π± : Phys. Rev. Lett. 84 (2000) 4047-4051
03/03/31 日本物理学会 11
Sinφ Moment of the Azimuthal Asymmetry (analyzed)Sinφ Moment of the Azimuthal Asymmetry (analyzed)
HERMES: Phys. Rev. D64 (2001) 097101
SL (T) : component of the longitudinal (transverse) target polarization in the virtual photon frame
q q
qqT
qqLqLUL zHxqxeySzHxxhe
yQ
ySA )()()1()()(
1
)2(2 ,1
2,1
2sin
z x p ⊥ (GeV)
sinφ moment of the azimuthal asymmetry: sin
ULA
π0
π+
π-
15.012
yQ
MxST
03/03/31 日本物理学会 12
Transversity Measurement at HERMESTransversity Measurement at HERMES
HERMES 1995-2000
HERMES 2002-
Longitudinally Polarized Target
Transversely Polarized Target
⇒ Quark Helicity Distribution: Δq ⇒ Glimpse on Quark Transversity Distribution: δq
⇒ Quark Transverse Distribution: δq
(analyzed)
(in progress)
03/03/31 日本物理学会 13
Target MagnetTarget Magnet
• Transverse target ( B = 0.295 T )• Transversely polarized hydrogen• Target polarization above 80%
03/03/31 日本物理学会 14
Azimuthal Asymmetries with Transversely Polarized Target(unpolarized beam)
q
q
UT zDxqe
zHxqeA
)()(
)()(
12
,1
2
sin
ls : Collins Angle
ls : Angle between Target Spin Vector
and Scattering Plane
)(1 zH : Collins Fragmentation Function
Azimuthal Asymmetry withAzimuthal Asymmetry withTransversely Transversely Polarized Target (in progress)Polarized Target (in progress)
03/03/31 日本物理学会 15
Integrated Deep Inelastic Scattering eventsIntegrated Deep Inelastic Scattering events
0 100 200 300
Total DIS : 512K
Day of Year (2002)
5000
4000
3000
2000
1000
0
×102
Nu
mb
er o
f D
IS
even
ts • 2002: 512 K DIS events
(accumulated)
• Up to Spring 2003: 1.3 M DIS events
(in progress)
03/03/31 日本物理学会 16
ConclusionConclusion
• HERMES is a deep inelastic scattering experiment using HERA 27.6 GeV positron beam • Transversity is the distribution of the quark’s transverse spin in a transversely polarized nucleon• The transversity measurement can provide a measure of the relativistic effects for quarks inside the nucleon•HERMES suggests both δq and significantly non-zero• HERMES is taking data with transversely polarized hydrogen target• Spring 2003: 1.3 Million DIS events expected• HERMES will do the first determination of transverse u-quark distribution
sinULA
1H
03/03/31 日本物理学会 17
How to Access TransversityHow to Access Transversity
• Drell - Yan Process
•Λ-hyperon Semi-Inclusive Deep Inelastic Scattering
• Collins Effect with Transverse Target
- Cleanest method is
- effect already visible using a longitudinally polarized target
11sin HhAUT
AdAUT sinsinsinφ moment
UTAAzimuthal Asymmetry with Transversely Polarized Target
U: Unpolarized BeamT: Transversely Polarized Target along Beam Direction
03/03/31 日本物理学会 18
q q
qqT
qqLqLUL zHxqxeySzHxxhe
yQ
ySA )()()1()()(
1
)2(2 ,1
2,1
2sin
Sinφ Moment of the Single Spin AsymmetrySinφ Moment of the Single Spin Asymmetry
HERMES, Phys. Rev. D64 (2001) 097101
• Larger for π+,π0 than π-
⇒ u-quark dominance in case of proton target• Peak around x=0.3 ⇒ valence quark dominance
SL (T) : component of the longitudinal (transverse) target polarization in the virtual photon frame
03/03/31 日本物理学会 19
Deep Inelastic Scattering (DIS)Deep Inelastic Scattering (DIS)
lepton
nucleon
γ
hadron
)(E,k k
) (M,P 0
),(E'k' k'
)(ν,q q
θ
)p,(Ep hhhadronization
fragmentation
2MνQ
x
, 2θ
sin 4EE'qQ
2
222
νE
z h
Inclusive
Semi-inclusive
03/03/31 日本物理学会 20
SSA with Longitudinal Polarized TargetSSA with Longitudinal Polarized Target
Longitudinally polarized in experiment(along beam direction) L/T polarized in theory
(along virtual gamma direction)
UTTULLUL SSA sinsinsin ~
03/03/31 日本物理学会 21
MotivationMotivation
quark (u,d,s)gluon
Sz
gqZ LGLS 2
1
2
1
Spin Structure of the Nucleon
Contribution from the quark spin
1988: EMC
1988-2000: SLAC, CERN, DESY
17.012.0
4.0...2.0
03/03/31 日本物理学会 22
MotivationMotivation
HERMES 1995-2000
HERMES 2002-
Longitudinally Polarized Target
Transversely Polarized Target
⇒ Quark Helicity Distribution: Δq
⇒ Remaining Quark Transverse Distribution: δq
03/03/31 日本物理学会 23
History of TransversityHistory of Transversity
The concept was Introduced by Ralston and Soper (1979) via Drell - Yan Production with polarized beams
LO anomalous dimensions were first calculatedby Baldracchini et al. (1981)
Also calculated (for g2 evolution) - Kodaira et al. (1979) - Antoniadis and Kounnas (1981) - Bukhvostov et al. (1985) - PGR (1986)
Re-calculated by Artru and Mekhfi (1990)
03/03/31 日本物理学会 24
Twist-2 Quark Distribution FunctionsTwist-2 Quark Distribution Functions
・
• Functions Surviving on Integration over Transverse Momenta• The others are sensitive to intrinsic < kt > in the nucleon and in the fragmentation process
03/03/31 日本物理学会 25
How Access TransversityHow Access Transversity
• Collins Effect with Transverse Target
• Λ-hyperon SIDIS
• Drell - Yan Process
- Cleanest method is
- effect already visible using a longitudinally polarized target
11sin HhAUT
11)()(
)()(hh
XllPPdXllPPd
XllPPdXllPPdADYTT
- Method requires significant spin transfer from quark to Λ in fragmentation process…
- low rate of quark fragmentation into Λ-particle ( ~ 2%)