study of spin structure of nucleon at compass and its challenges
DESCRIPTION
STUDY OF SPIN STRUCTURE OF NUCLEON AT COMPASS AND ITS CHALLENGES. Takahiro Iwata Yamagata University. on behalf of the COMPASS Collaboration. KEK Workshop on Nucleon Structure, January 10, 2009. OUTLINE. COMPASS apparatus Data taking history Direct measurements of D G/G - PowerPoint PPT PresentationTRANSCRIPT
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STUDY STUDY OF OF
SPIN STRUCTURE OF NUCLEON SPIN STRUCTURE OF NUCLEON AT COMPASSAT COMPASS
ANDANDITS CHALLENGESITS CHALLENGES
Takahiro IwataYamagata University
KEK Workshop on Nucleon Structure, January 10, 2009
on behalf of the COMPASS Collaboration
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COMPASS apparatus Data taking history Direct measurements of G/G
high pT hadron pairs & open charm
q from SI-DIS Transverse spin effects
asymmetries with proton target Plans and Challenges
OUTLINE
Takahiro Iwata KEK Workshop on Nucleon Structure 2009, January 10, 2009
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Takahiro Iwata KEK Workshop on Nucleon Structure 2009, January 10, 2009
SM1
SM2
Pol. beam
MuonWall
MuonWall
E/HCAL
E/HCAL
RICH
Polarised Target
SciFiSiliconMicromegasGEMs
StrawsSDCMWPCW45
THE SPECTROMETERtwo stages spectrometer • Large Angle Spectrometer (SM1)• Small Angle Spectrometer (SM2)
tracking, calorimetry, PID
• high energy beam• broad kinematical range• large angular acceptance
0.003 < x < 0.510-3 < Q2 < 10 GeV2
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THE TARGET SYSTEM
Solid polarized target operated in Dynamic Nuclear Polarization technique with a dilution refrigerator
New COMPASS target magnet:+180~-180 mrad geometrical acceptance The world largest polarized targetTo match larger acceptance:new microwave cavity3 target cells: reduction of false asymmetries
Target: NH3 for proton , 6LiD for deuteron
longitudinal & transverse mode availablevery long relaxation time ( 4000 h)∼magnetic field rotation without polarization loss Polarization of NH3 -92%, +88%, -83%
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THE RICH DETECTOR
5 m
6 m3 m
CC44FF1010
photon detectors
threshold momenta● p= 2 GeV/c● p
K = 9 GeV/c
● pP =17 GeV/c
Takahiro Iwata KEK Workshop on Nucleon Structure 2009, January 10, 2009
• radiator gas: C4F10
• mirror wall: 20 m2 surface• photon-detectors:
•outer part (75%) MWPC(pad RO) with CsI cathode• inner part(25%) 576 MAPMTs with indiv. telescope
Installed in 2005,Used in data taking from 2006
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DATA TAKING HISTORY 2002 - 2008
in 2002, 2003, 2004, 2006 and 2007
COMPASS has taken data in muon program configuration
160 GeV, polarized muon
• 2002-2006 6LiD polarized target ( ~pol. deuterons)
L-mode: 80 / T-mode: 20
2005 no data taking, new target system installed
• 2007 NH3 polarized target (~ pol. protons)
L-mode: 50 /T-mode: 50
• 2008: hadron beam at 190 GeV for the hadron program
Takahiro Iwata KEK Workshop on Nucleon Structure 2009, January 10, 2009
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Takahiro Iwata KEK Workshop on Nucleon Structure 2009, January 10, 2009
Direct Measurements Direct Measurements of of
Gluon Polarization Gluon Polarization G/GG/G
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DIRECT MEASUREMENTS OF G/G
Leading order analysis in the moment..
access to G/G
Photon Gluon Fusion: g -> qq
q = u,d,s “HIGH pT HADRON PAIRS”2 hadrons with high pT
Large statistics physical background: „model” (MC) dependent
・ hard scale given by pT
q = c “OPEN CHARM”charm hadrons ( one hadron detected)
no background, less MC dependent.
small statistics
・ hard scale charm mass: 2 = 4mc2
Takahiro Iwata KEK Workshop on Nucleon Structure 2009, January 10, 2009
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Takahiro Iwata KEK Workshop on Nucleon Structure 2009, January 10, 2009
// PGF BkgPGFGA R a A
G
+PhotonGluonFusion
LeadingOrderDIS
QCD Compton
Resolved Q2 < 1 GeV2
measure
HIGH PT HADRON PAIRSextracted
Data divided into two data sets• High Q2 : Q2>1GeV2
• Low Q2 : Q2<1GeV2
PGF
totPGFR
LO
totLOR
C
totCR
PGFaLOa Ca
cross-section ratio
analyzing power
Monte Carlo
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Takahiro Iwata KEK Workshop on Nucleon Structure 2009, January 10, 2009
HIGH PT HADRON PAIRS : Q2>1 GeV2
/ 0 08 0 10 0 05G G . . (stat.) . (syst.)
2002-2004 data result:
2 2g @ x 0.082 ( : 0.055 0.123) 3 ( / ) range GeV c (prelim.)
systematic error: false asymmetry mainly contributes
• Q2>1GeV2, 0.1 < y < 0.9• pT1, pT2 > 0.7 GeV, XF1,2>0, z1,2>0, z1+z2<0.95• M2
h1,h2>1.5GeV2
• Monte Carlo• LEPTO with MRST2004LO & JETSET
fragmentation• R & a for PGF, QCDC and LO determiend• Neural Network parametrization• Good agreement with the data
New result
averaged values
Reduced by 1/3from 2002-2003
New
method
In previous analysisAbkg neglected , because A1,d~0 at small x
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Takahiro Iwata KEK Workshop on Nucleon Structure 2009, January 10, 2009
HIGH PT HADRON PAIRS : Q2<1 GeV2
PYTHIA-Monte Carlo for low Q²
PGF
QCDC
LO DIS
Direct Resolvedphoton
neglect
neglect
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Takahiro Iwata KEK Workshop on Nucleon Structure 2009, January 10, 2009
HIGH PT HADRON PAIRS : Q2<1 GeV2
point like: perturbative(calculable) VMD: non-pertarbative extream scenarios
photon PDFs : unknownResolved photon processes
,
, , , , , ,
f f f f f f
f u d s u d s g
VMD VMDpoint like point like
VMD VMD VMDf f f - M.Gluck et al., Eur.Phys.J. C20:272(2001)
/ 0 016 0 058 0 055G G . . (stat.) . (syst.) 07.0035.0085.0
Gx @ 22 )c/GeV(3 (prelim.)
2002-2004 data result:
PL B 633 (2006) 25COMPASS 2002-03 data published
Stat. error reduced by 30% compared to
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Takahiro Iwata KEK Workshop on Nucleon Structure 2009, January 10, 2009
πKD0 * 0D D
Kslow
untaggedD* tagged by slow pion
G/G FROM OPEN CHARM
BR:4%BR:68%
nD0 = 37398 nD* = 8675
D0K
D0K0
D0K
0K DM M GeV 0K D
M M GeV
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Takahiro Iwata KEK Workshop on Nucleon Structure 2009, January 10, 2009
2002 – 2006 (full deuteron statistics) D0+D*
G/G = - 0.49 ± 0.27 (stat) ± 0.11(syst) @ xg ~ 0.11, m2 ~ 13 GeV2
G/G FROM OPEN CHARM
b T
1A
fP P LL
GSG a S B
• Neural network trained with AROMA Monte Carlo
• good description of data
• f : dilution factor ~0.4• Pb : beam polarization ~0.8• Pt : target polarization ~0.5• S/(S+B): determined from fit• Calculation with event weighting
False asymmetry
& S/S+B determination
New result
Kinematics not fully given in the experiment (only one charm detected)
need efficient way to determine aLL
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Takahiro Iwata KEK Workshop on Nucleon Structure 2009, January 10, 2009
QCD Fit to g1
COMPASS062 = 3 Gev2
RESULTS FOR G/G
ΔG/G ≈0 @ xg ≈ 0.1
new high-pT pointhigh Q2
new open charm
∫DG=+0.26
∫DG=-0.31
RECALL: charm point at larger scale (2 = 13 Gev2 )
HERMESSinglehadron
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G/G SUMMARY & PROSPECTS
New preliminary results have been obtained G/G ≈0 at xg ≈ 0.1 likely
Prospects:
open charm:
including 2007 proton data, but not much improvement
high-Pt hadron pairs:
include data from 2006, 2007
use single high-Pt hadron, determine G/G in 2-3 bins of xg
Takahiro Iwata KEK Workshop on Nucleon Structure 2009, January 10, 2009
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Takahiro Iwata KEK Workshop on Nucleon Structure 2009, January 10, 2009
Polarized PDF, Polarized PDF, qq
fromfromSemi-Inclusive Semi-Inclusive
DISDIS
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q from SI-DIS
Takahiro Iwata KEK Workshop on Nucleon Structure 2009, January 10, 2009
Inclusiveasymmetry
flavor dependent fragmentation functions
flavor & valence/sea decomposition for q
Semi-inclusivehadron identified asymmetries
2 2 2q 1q2
1 2 2 2q 1q
e Δq x,Q g x,QA x,Q =
e q x,Q F x,Q
2 2 2qqh 2
1 2 2 2qq
e Δq x,Q z,QA x, z, Q
e q x,Q z,Q
hq
hq
D
D
2z,QhqD
COMPASS 2002-2006 data on deuteron (full statistics on deuteron)
Evaluation of , , v vΔu +Δd Δu+Δd Δs Δs
+ - + -π π K K1,d 1,d 1,d 1,d 1,dA , A , A , A , A
at LO QCD
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Takahiro Iwata KEK Workshop on Nucleon Structure 2009, January 10, 2009
deuteron data 2002-2006 ( full statistics on deuteron)
ASYMMETRIES
Q2>1GeV2, 0.004<x<0.3, 10<p<50GeV, 0.2<z<0.85
Statistics: + 623 10 - 621 10 + 64.8 10 K - 63.3 10 K
Impurities corrected; although the correction is very small
New data
at small x
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Takahiro Iwata KEK Workshop on Nucleon Structure 2009, January 10, 2009
• Asymmetries to be independent on Q2 :• Assume• Un-polarized PDF: MRST04• Fragmentation Functions: two parameterizations
• DSS-FF • from e+e-, SI-DIS , pp collision
• EMC-FF• charge/isospin symmetry • all un-favored FFs are equal• Assume • No Q2 dependence• s-quark favored FF is large
• Least square fit in each x bin
+ +K πus
D =D
BASES OF EVALUATION
Δs=Δs h
1,dA x, z
+ -
+ -
K Ks s
SF
u u
D DR = 3.4
D D
K K
SFR 6.6
main differencein favored FF of strange quark
:
:
Ku
K
s
u uDK
s sD
:
:
K
u
Ks
D u uK
s sD
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Takahiro Iwata KEK Workshop on Nucleon Structure 2009, January 10, 2009
Similar results with different FFs;agreement with LO DNS-PDF
RESULTS OF FIT
Compatible with 0;Not sensitive to FFs
EMC-FF gives larger stat. errors
DNS-PDF: global fit to e+e-, SIDIS & pp Phys.Rev.D71:094018,2005(comparable to typical QCD fits to g1)
0.3
0.0040.035 sdx DNS-PDF:
0.3
0.004
0.01 0.01 0.01(DSS-FF)
0.05 0.03 0.01(EMC-FF)
sdx
valence
sea
strange
1 0.3
0.3 0.0040.002 s dx sdx
small contribution from large x
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Takahiro Iwata KEK Workshop on Nucleon Structure 2009, January 10, 2009
agreement between two evaluations
s FROM CHARGED KAON ASYMMETRY
well constrained
by K+ and K- cross-
section data
+ -K +K1,d 1,d 1,d
Δs Q/s+α=A + A -A
s α-0.8
DNS-FF
+
+
Kd
UF Ku
D z dzR = 0.14
D z dz
Q=u+u+d+d
+
+
K
sSF K
u
D z dzR =
D z dz
UF SF
UF
2R 2R=
3R 2
UF
SF
R =0.14
R =6.6
=3.4
6.6 EMC-FF
DNS-FF
=2.1 KRE-FF
not constrained !
Alternative way to access s
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Takahiro Iwata KEK Workshop on Nucleon Structure 2009, January 10, 2009
• 1st moment strongly depends on RSF
• With a large RSFs<0 expected in unmeasured lower x region
• Comparison between SI-DIS and inclusive DIS is limited by the errors
s V.S. RSF
from SI-DIS0.3
0.004 sdx
UFR =0.14
1
0 sdx from inclusive DIS
COMPASS,QCD-fits to g1
Phys.Lett. B 660 (2008) 458
1 0.3
0.3 0.0040.002 s dx sdx
only 2 difference
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Takahiro Iwata KEK Workshop on Nucleon Structure 2009, January 10, 2009
q FROM SI-DIS SUMMARY
SI-DIS asymmetries from full deuteron data shown
Evaluation of valence, sea, strange polarized PDFs
Valence component is consistent with inclusive DIS data
Sea polarization is 0 over the measured range
Strange component strongly depends on s-quark FF (RSF )
Comparison between SI-DIS and incl. DIS is limited by errors
Prospects:
analysis of 2007 proton data
extraction of RUF and RSF form COMPASS
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Takahiro Iwata KEK Workshop on Nucleon Structure 2009, January 10, 2009
Transverse Spin EffectsTransverse Spin Effects
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TRANSVERSE SPIN EFFECTS IN COMPASS
Tq(x) = q↑↑(x) - q↑↓(x)
h1q(x),
q(x), Tq(x)
Transversity PDF quark with spin parallel to the nucleon spin in a transversely polarized nucleon
from Collins asym. in SIDIS single hadron production transverse polarization, two hadron asym. , ,,,
related to orbital angular momentum of quark
TMD PDF an intrinsic asymmetry in the parton transverse momentum distribution induced by the nucleon spin
from Sivers asym. in SIDIS single hadron production
Takahiro Iwata KEK Workshop on Nucleon Structure 2009, January 10, 2009
New COMPASS data for Collins & Sivers Asymmetries on Proton
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SINGLE HADRON ASYMMETRIES
S = azim. angle of initial quark spin
S’ = azim. angle of struck quark spin
S= - S’ ( due to helicity conservation)
h = azim. angle of leading hadron initial quark spin (nucleon spin)struck quark spin
hadron ( Breit frame )quark direction
•Collins angle: Azim. angle of a hadron wrt the struck quark spin
C = h - S’ (= h +S- )
•Sivers angle:Azim. angle of a
hadron wrt the initial quark spin
(=nucleon spin)
S= h - S
Scattering plane
SIDIS cross-section for transv. PT
1 ... C SSIDIS 1 2dσ a sin a sin
Collins Sivers
Takahiro Iwata KEK Workshop on Nucleon Structure 2009, January 10, 2009
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COLLINS & SIVERS ASYMMETRIES
Collins Asymmetry
± refer to the opposite orientation of the transverse spin of the nucleonPT is the target polarisation; DNN is the transverse spin transfer coefficient initial struck quark, given by QED
y 0
h C h T NN Coll CN N 1 P D A sin
2 0 hq T T qq
Coll 2 hq qq
e Δ q Δ DA
e q D
0h S h T Siv SN N 1 P A sin
2 T hq 0 qq
Siv 2 hq qq
e Δ q DA
e q D
Sivers Asymmetry
Transvesity
Sivers PDF
Collins fragmentation
function
Takahiro Iwata KEK Workshop on Nucleon Structure 2009, January 10, 2009
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PROTON DATA EVENT SELECTION
Takahiro Iwata KEK Workshop on Nucleon Structure 2009, January 10, 2009
DIS cuts:
• Q2>1 (GeV/c)2, 0.1<y<0.9, W>5 GeV/c2
Cut for hadrons
Track Length<10 X0
Energy Deposit in HCALs
pT>0.1 GeV/c
Z>0.2
Statistics h+ : 5.7M h-: 4.5M
Proton data in 2007, ~20% analyzed
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COLLINS ASYMMETRY ON PROTON
Takahiro Iwata KEK Workshop on Nucleon Structure 2009, January 10, 2009
at small x, the asymmetries are compatible with zero in the valence region the asymmetries are different from zero,opposite sign for positive and negative hadrons, and the same strength and sign as HERMES
systematic errors ~ 0.3 stat
20% statistics
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Takahiro Iwata KEK Workshop on Nucleon Structure 2009, January 10, 2009
COLLINS ASYM. DATA V.S. PREDICTIONcomparison with M. Anselmino et al. predictions
arXiv:0805.2677
good agreement
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SIVERS ASYMMETRY FOR PROTON
Takahiro Iwata KEK Workshop on Nucleon Structure 2009, January 10, 2009
the measured asymmetries are small, compatible with zero
systematic errors ~ 0.5 stat
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Takahiro Iwata KEK Workshop on Nucleon Structure 2009, January 10, 2009
SIVERS ASYM. DATA V.S. PREDICTION
comparison with recent M. Anselmino et al. predictionsarXiv:0805.2677
marginal agreement with COMPASS proton data
HERMES proton data
COMPASS deuteron data
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TRANSVERSEPOLARIZATION
2q
qT 2
q Λ /qq
T Λ /ΛT,ex
T
p
qΔ q xe
= fP D ye q x D
D
P
Δ z
z
PT : target polarization;
f : target dilution factor D(y): transverse spin transfer coefficient initial struck quark, given by QED
Transversity
Takahiro Iwata KEK Workshop on Nucleon Structure 2009, January 10, 2009
2002-2004 deuteron data (no RICH ID) already reported Small tendency seen for anti-Λ
Another way to access Transversity
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NEW DATA ON PROTON TARGET
p
Takahiro Iwata KEK Workshop on Nucleon Structure 2009, January 10, 2009
• Secondary vertex downstream of primary vertex.• PT > 23 MeV/c to exclude e+e− pairs• Proton and pion momenta > 1 GeV/c• Q2 > 1 (GeV/c)2, 0.1 < y < 0.9• Λ decay distance DΛ > 7 σD
• Collinearity < 10 mrad
0sK
0sK
• Pid by RICH• 60% higher statistics
w.r.t. deuteron data
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POLARIZATION ON PROTON TARGET
Takahiro Iwata KEK Workshop on Nucleon Structure 2009, January 10, 2009
• Systematic errors have been estimated to be smaller than statistical errors from false polarization.
• No dependence on x.
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TRANSVERSE SPIN EFFECTS SUMMARY
New preliminary results of 2007 proton transverse run:
• Collins Asymmetry:• different from zero• Agreement with predictions of Anselmino et al.
(consistent with HERMES, Belle)• Sivers Asymmetry:
• Small and compatible with zero within present statistical errors
• Marginal agreement with the prediction • Transverse polarization:
• small and compatible with zero within present statistics
Takahiro Iwata KEK Workshop on Nucleon Structure 2009, January 10, 2009
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Takahiro Iwata KEK Workshop on Nucleon Structure 2009, January 10, 2009
Plans and Challenges Plans and Challenges in in
COMPASSCOMPASS
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PLANS & CHALLENGES IN COMPASS
2009 Run for Hadron program 190 GeV hadron beam & Liq.H2 target (partly test with the muon beam)2010~ Run for Muon program(with pol. proton target)?
Challenges• Polarized Drell-Yan program
• 200 GeV - Beam & Polarized Target• TMD PDFs(Boer-Mulders, Sivers) • Transversity
• GPD program• 100GeV polarized Beam & Liq.H2 Target(+ Pol.T)
• DVCS(Deeply Virtual Compton Scattering)• HEMP(Hard Exclusive Meson Production)
Takahiro Iwata KEK Workshop on Nucleon Structure 2009, January 10, 2009
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Takahiro Iwata KEK Workshop on Nucleon Structure 2009, January 10, 2009
BACKUP SLIDES
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EVENT SELECTION
DIS events
Q2 > 1 GeV2
W2 > 25 GeV2
0.1 < y < 0.9
hadrons
pht > 0.1 GeV/c
z > 0.2 (all h)
z > 0.25 (leading h)
Q2 = 2.4 (GeV/c)2
xBj 0.035
W = 9.4 GeV/c2
2002 dataTakahiro Iwata KEK Workshop on Nucleon Structure 2009, January 10, 2009
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ASYMMETRIES 2003-2004 vs 2002
2003-2004 data released in April 2006 (DIS2006)
comparison with the published 2002 data PRL 94 (2005) 202002
increase in statistics by a factor of 7!
Takahiro Iwata KEK Workshop on Nucleon Structure 2009, January 10, 2009
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COLLINS ASYMMETRIES 2002-2004
DIS2006DIS2006
• small errors (~1%)• small asymmetries
d0Tu
0TTTd Coll, DD4dΔuΔA• cancellation between p and n
(lh and ah) d0Tu
0TTTd Coll, DDdΔuΔA 4
CERN-PH-EP/2006-036
Takahiro Iwata KEK Workshop on Nucleon Structure 2009, January 10, 2009
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• SIDIS(deuteron COMPASS/ proton HERMES) & Belle data
Anselmino et al., hep-ph/0701006v1
COLLINS ASYMMETRY & GLOBAL FIT
PRESENT PICTURE
T0D(fav.) ~ - T
0D(unfav)
Td not well constrained
from the global fit
Takahiro Iwata KEK Workshop on Nucleon Structure 2009, January 10, 2009
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SIVERS ASYMMETRIES 2002-2004
DIS2006DIS2006
DdΔuΔA T0
T0d Siv,
• small errors (~1%)• small asymmetries
• cancellation between p and n (lh and ah)
CERN-PH-EP/2006-036
Takahiro Iwata KEK Workshop on Nucleon Structure 2009, January 10, 2009
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model calculations to be compared with the COMPASS 2002-04 data
Vogelsang and Yuan
Anselmino et al
preliminary COMPASS 2002-2004
preliminary COMPASS 2002-2004
Collins et al
preliminary COMPASS 2002-2004
SIVERS ASYMMETRIES & MODELS
T T0 0Δ u - Δ d
PRESENT PICTURE
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again, difficult to see an effect …
±, K± Collins Asymmetries 2003-2004
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±, K± SIVERS ASYMMETRIES 2003-2004
Takahiro Iwata KEK Workshop on Nucleon Structure 2009, January 10, 2009
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TWO HADRON ASYMMETRIES
modulation of the number of events in RS
initial quark spin quark direction
S = angle of initial quark spin (=target spin)
S’ = angle of final (struck) quark spin
S= - S’ ( due to helicity conservation)
R = angle of two-hadron plane
RS =R –S’ = R +S-
Breit framesee hep-ph/0407345
Trento conventions
( ) / ( ) /( )
( ) / ( ) /RS tot RS tot
UT RS
RS tot RS tot
N N N NA
N N N N
RSsinUT RSA sin( )
2 2
2 2
,
,RS
hi T i i hsin i
UT hi i i hi
e q x H z MA
e q x D z M
2,hi hH z M : interference
fragmentation function( presently unknown)
transversityRSi
f
h
l-l’
Takahiro Iwata KEK Workshop on Nucleon Structure 2009, January 10, 2009
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TWO HADRON ASYMMETRIES
Event selectionz1> 0.1 & z2>0.1 xf1>0.1 & xf2>0.1z=z1+z2<0.9
2002-2004
6.1x106 combinations
diffractive production
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TWO HADRON ASYMMETRIES
RSsin
RSUT
NN T
=D P
AA
f
DNN : transverse spin transfer
coefficient initial struck quark
f : target dilution factor
PT : target polarization;
Takahiro Iwata KEK Workshop on Nucleon Structure 2009, January 10, 2009
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TWO HADRON ASYMMETRIES
z ordered pairs
Takahiro Iwata KEK Workshop on Nucleon Structure 2009, January 10, 2009
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Takahiro Iwata KEK Workshop on Nucleon Structure 2009, January 10, 2009
TRANSVERSE MOMENTUM DEPENDENT PDFs
1( )f qNucleon
Parton
numberdensity
Nucleonunpol. long. pol. trans. pol.
unpol.long. pol.
trans. pol.Q
uark
1Tf
Tk
Sivers
1 ( )Lg q helicity 1Tg
1h
Tk
1( )Th q transversity
1ThTk1Lh
Tk
T-odd
Tk
survive after integration over kT
T-odd
Boer-Mulders
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RESULTS OF NLO QCD FIT
solutions : G > 0 G < 0
∫G(x)dx = +0.26 +0.04,-0.06 -0.31 +0.10,-0.14
∫(x)dx = +0.28 ± 0.01 +0.32 ± 0.01
@ Q2=3(GeV)2
Both give 0.2-0.3 for the absolute value of the gluon spin contribution (∫G(x)dx)
Gluon spin contribution is not large
Takahiro Iwata KEK Workshop on Nucleon Structure 2009, January 10, 2009
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TRANSVERSEPOLARIZATION
L L
L L
P P
P P
2q
qT 2
q Λ /qq
T Λ /ΛT,ex
T
p
qΔ q xe
= fP D ye q x D
D
P
Δ z
z
p
PT : target polarization;
f : target dilution factor D(y): transverse spin transfer coefficient initial struck quark, given by QED
Transversity
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systematic errors not larger than statistical errors
RICH ID not used yet
POLARIZATION ON DEUTERON TARGET
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SIVERS ASYMMETRY ON PROTON
Takahiro Iwata KEK Workshop on Nucleon Structure 2009, January 10, 2009
x>0.05 x>0.05
H.Wollny, SPIN 2008
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hard scale: 2 = 4mc2
Theory understood
Combinatorial background
Limited statistics
Challenging measurement
c
c
Photon Gluon Fusion: g -> c c
G/G FROM OPEN CHARM
0
0( )
D K
D K
Kaon ID with RICH
Takahiro Iwata KEK Workshop on Nucleon Structure 2009, January 10, 2009
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c
c
q from SI-DIS, Impurity studies
Takahiro Iwata KEK Workshop on Nucleon Structure 2009, January 10, 2009