harut avakian (jlab)
DESCRIPTION
SIDIS results from JLAB. Harut Avakian (JLab). Mainz, April 1, 2009. Outline. Describe the complex nucleon structure in terms of partonic degrees of freedom of QCD. Physics motivation Transverse Momentum Distributions (TMDs) of quarks and spin-azimuthal asymmetries in semi-inclusive DIS - PowerPoint PPT PresentationTRANSCRIPT
IWHSS09, Apr 11
Harut Avakian (JLab)Harut Avakian (JLab)
Mainz, April 1, 2009
SIDIS results from JLAB
IWHSS09, Apr 12
Outline
Describe the complex nucleon structure in terms of partonic degrees of freedom of QCD
•Physics motivation–Transverse Momentum Distributions (TMDs) of quarks and spin-azimuthal asymmetries in semi-inclusive DIS
•SIDIS results from JLab at 6 GeV –Tests of the applicability of the partonic picture–Studies of spin-orbit correlations with CLAS
•Measurements of TMDs at 6 GeV–Longitudinally polarized proton target measurements (E05-113) –Transversely polarized 3He (E06-010/011) and proton targets (E08-015)
•Summary
IWHSS09, Apr 13
z
sin2moment of the cross section for unpolarized beam and longitudinal target
U unpolarizedL long.polarizedT trans.polarized
SIDIS kinematical plane and observables
Transverse spin effects are observable as correlations of transverse spin and transverse momentum of quarks.
IWHSS09, Apr 14
Structure of the Nucleon
GPDs/IPDs
d2kT
d2kT
TMD PDFs f1
u(x,kT), .. h1u(x,kT)
Gauge invariant definition (Belitsky,Ji,Yuan 2003)Universality of kT-dependent PDFs (Collins,Metz 2003)Factorization for small kT. (Ji,Ma,Yuan 2005)
Wpu(k,rT) “Mother” Wigner distributions
d2 r T
PDFs f1u(x), .. h1
u(x)
quark polarization
IWHSS09, Apr 15
CLAS at JLAB
Electron beam energy 6 GeV Lumi ~1034cm-2sec-1
IWHSS09, Apr 16
Scattering of 5.7 GeV electrons off unpolarized and polarized proton and deuteron targets
SIDIS with CLAS at 6 GeV
DIS kinematics, Q2>1 GeV2, W2>4 GeV2, y<0.85 0.4>z>0.7, MX
2>2 GeV2
2
eX
e
1) Polarized NH3/ND3 (~5 days)2) Polarized H 30+30 days (2001/2005)
IWHSS09, Apr 17
multiplicities in SIDIS ep→e’X
+/- multiplicities at large z diverge from SIDIS predictions0 multiplicities less affected by higher twists0.4<z<0.7 kinematical range, where higher twists are expected to be small
DSS (Q2=2.5GeV2)
DSS (Q2=25GeV2)
M.AghasyanHall-C
IWHSS09, Apr 18
Rpd-
Both ratios agree with PDF models for z<0.7 (Mx>1.4 GeV)
Tests of partonic picture with ratios
Hall-C @ 6 GeV
Rpd+
IWHSS09, Apr 19
A1 PT-dependence in SIDIS
M.Anselmino et al hep-ph/0608048
+ ALL can be explained in terms of broader kT distributions for f1 compared to g1
02=0.25GeV2
D2=0.2GeV2
In perturbative limit predicted to be constant
Como-2005
constituent quark model (Pasquini et al).
IWHSS09, Apr 110
BBS/LSS no OAM
BBS/LSS with OAM
Quark longitudinal polarization
JMR model
q
DqMR , R=s,a
For given x the sign of the polarization is changing at large kT
Effect of the orbital motion on the q- may be significant (H.A.,S.Brodsky, A.Deur,F.Yuan 2007)
u/u
(dipole formfactor), J.Ellis, D-S.Hwang, A.Kotzinian
IWHSS09, Apr 111
A1 PT-dependence in SIDIS
M.Anselmino et al hep-ph/0608048
+ A1 suggests broader kT distributions for f1 than for g1
- A1 may require non-Gaussian kT-dependence for different helicities and/or flavors
02=0.25GeV2
D2=0.2GeV2
0.4<z<0.7
IWHSS09, Apr 112
Extracting widths from A1
Assuming the widths of f1/g1 x,z and flavor independent
Anselmino et al
Collins et al
Fits to unpolarized data
IWHSS09, Apr 113
A1 PT-dependence
CLAS data suggests that width of g1 is less than the width of f1
AnselminoCollins
IWHSS09, Apr 114
Collins Effect: azimuthal modulation of the fragmentation function
D(z,PT)=D1(z,PT)+H1┴(z,PT) sin(hS’)
spin of quark flips wrt y-axisS’ = -S sin(hS)
C
S
STy
x
h
PT sT
S’
C
FUT∞h1H1┴ sT(q×PT)↔ H1┴
x
PT
hS=h
y
y
x
S h
PTS = +h
x
PT
h
S=y
hadronizing quark
Intial quark polarization
IWHSS09, Apr 115
SIDIS (*p->X) x-section at leading twist
•Measure Boer-Mulders distribution functions and probe the polarized fragmentation function•Measurements from different experiments consistent
TMD PDFs
IWHSS09, Apr 11616
Kotzinian-Mulders asymmetryKotzinian-Mulders asymmetry
•Data indicate that spin-orbit correlations with long.pol. target may be significant•Provide measurement of SSA for all 3 pions, extract the RSMT TMD (Ralston-Soper (1979), Mulders-Tangerman (1995)
curves, QSM from Efremov et al
Transversely polarized quarks in the longitudinally polarized nucleon
More data needed to clarify the situation with negative pions
IWHSS09, Apr 11717
What comes nextWhat comes next
Hall-A Transversely polarized 3He target measurement (E06-010/011)
Hall-B Longitudinally polarized proton (NH3) target measurement (E05-113)
Hall-B Transversely polarized proton target measurement (E08-015)
Currently runningCalibrating September 2011
Sivers asymmetry
Collins asymmetry with transverse (neutron)target
Correlations of transverse and longitudinal momenta (PT-dependences) in ALL
Collins asymmetry with longitudinally polarized (proton) target
Exclusive asymmetries as background
Sivers asymmetry
Collins asymmetry with transverse proton target
Shape of proton studies
Exclusive asymmetries as background
Fixed bins in x/Q2 Wide kinematical coverage , multiple hadronic states
IWHSS09, Apr 118
Cell: Astral Cell: Maureen
e
e’
HRSL
BigBite
16o
30o
Polarized3He Target
Target Single-Spin Asymmetry in Semi-Inclusive n↑(e, e’+/-)
pt ~ 65% (proposal 42%)
• First measurement of the neutron Collins and Sivers asymmetries in SIDIS.
• High density polarized 3He target. • Run in Hall A from 10/24/08-2/5/09. 110 shift workers, 7 Ph.D. students.
Reaction on a Transversely Polarized 3He TargetE06-010:
IWHSS09, Apr 119
Experimental Setup
Inner Calorimeter (424 PbWO4 crystals) to detect high energy photons at forward lab angles.
Polarized target (NH3/ND3)
13o
50o
IC
1) Polarized NH3 with IC 60 days 2) Polarized HD-Ice (no IC, 25 days)
IWHSS09, Apr 12020
AALLLL P PTT-dependence in SIDIS-dependence in SIDIS
M.Anselmino et al hep-ph/0608048
• study the PT-dependence for different quark helicities and flavors for bins in x, 2 (x) • flavor decomposition in PT-bins.
02=0.25GeV2
D2=0.2GeV2
0.4<z<0.7
E05-113
IWHSS09, Apr 12121
Kotzinian-Mulders asymmetryKotzinian-Mulders asymmetry
•Provide measurement of SSA for all 3 pions, extract the RSMT TMD (Ralston-Soper (1979), Mulders-Tangerman (1995) •Study Collins fragmentation with longitudinally polarized target
curves, QSM from Efremov et al
60 days of CLAS L=1.5.1034cm-2s-1
Transversely polarized quarks in the longitudinally polarized nucleon
E05-113
IWHSS09, Apr 122
Pros1. Small field (∫Bdl~0.005-0.05Tm)2. Small dilution (fraction of events from polarized material)3. Less radiation length4. Less nuclear background (no nuclear attenuation)5. Wider acceptance
much better FOM, especially for deuteron Cons
1. HD target is highly complex and there is a need for redundancy due to the very long polarizing times (months).
2. Need to demonstrate that the target can remain polarized for long periods with an electron beam with currents of order of 1-2 nA
3. Additional shielding of Moller electrons necessary (use minitorus)
CLAS transversely polarized HD-Ice target
Heat extraction is accomplished with thin aluminum wires running through the target (can operate at T~500-750mK)
HD-Ice target at ~2nA ~ NH3 at 5 nA
HD-Ice target vs std nuclear targets
IWHSS09, Apr 12323
Collins SSAsCollins SSAs
CLAS with a transversely polarized target will allow measurements of transverse spin distributions and constrain Collins fragmentation function
Anselmino et al (2007) Boffi et al (2009)
helicity-transversity=pretzelosity
CLAS E08-015
IWHSS09, Apr 12424
Measurement of Sivers function and GPD-E
DVCS Transverse asymmetry (function of momentum transfer to proton) is large and has strong sensitivity to GPD-E
CLAS will provide a measurements of Sivers asymmetry at large x, where the effect is large and models unconstrained by previous measurements.
Meissner, Metz & Goeke (2007)
GPD-E=0
(DVCS) (SIDIS)CLAS E08-015
IWHSS09, Apr 125
Summary
Significant azimuthal moments in pion production in SIDIS are measured using CLAS with longitudinally polarized target.
Measurements of azimuthal dependences of double and single spin asymmetries indicate that correlations between spin and transverse motion of quarks may be significant.
PT-dependences of the double and single-spin asymmetries provide important input for studies of flavor and helicity dependence of quark transverse momentum dependent distributions.
Upcoming CLAS SIDIS experiments at 6 GeV will significantly improve the statistical precision of longitudinally polarized target data, and will provide new data on transversely polarized target
IWHSS09, Apr 126
Support slides….
IWHSS09, Apr 127
IWHSS09, Apr 128
Factorization studies
Rpd+ for any z, pt (if d and u have same pt dependence)!
Simple LO picture in valence region:
Rpd- for any z, x!
IWHSS09, Apr 129
The CLAS Detector
~ 200 physicists37 institutions
large kinematical coverage high luminositymulti-particle final states
charged particles:p>0.2 GeV/c8o<<140o
p/p~0.5% (<30o)p/p~1-2%(>30o)=1mrad=4mrad
IWHSS09, Apr 13030
Sivers effect: protonSivers effect: proton
•CLAS will provide a superior measurements of Sivers asymmetry at large x, where the effect is large and models unconstrained by previous measurements. •Measure also asymmetries in target fragmentation region and for exclusive channels (background)
Vogelsang & YuanSchweitzer et al
CLAS E08-015
IWHSS09, Apr 131
Collins fragmentation: Longitudinally polarized target
•Study the Collins function of kaons•Provides independent information on the RSMT TMD
Kotzinian-Mulders Asymmetry
proton deuteron
Pasquini et al.
IWHSS09, Apr 132
Collins Effect: azimuthal modulation of the fragmentation function
D(z,PT)=D1(z,PT)+H1┴(z,PT) sin(hS’)
spin of quark flips wrt y-axisS’ = -S sin(hS)
C
S
STy
x
h
PT sT
S’
C
FUT∞h1H1┴
S
y
x
h
PT
sT(p×kT)↔ h1┴
FUU∞h1 ┴ H1┴
S = +h
sT(q×PT)↔ H1┴
x
sin(2h)
PT
h
S=h
y
FUL∞h1L H1┴┴
(sTkT)(pSL)↔ h1L┴sin(h+S)
cos(2h)
IWHSS09, Apr 133
JLab, Nov 2533
Hall A E06-010Hall A E06-010: Neutron (3He) Transversity : Neutron (3He) Transversity
Collins: transversity Sivers: Orbital Angular Momentum
First JLab transverse SSA measurement: running now to 2/09 First world neutron(3He) measurement
IWHSS09, Apr 134
Contributions to in Double Polarized SIDIS
TMDsMulders et al
IWHSS09, Apr 135
Spin densities in transverse proton from Lattice(QCDSF/UKQCD)
G.Miller/”pretzelosity”
u-quark
d-quark
Spin of quark
Boer-Mulders TMD
IWHSS09, Apr 136
SSA with unpolarized target
quark polarization
IWHSS09, Apr 137
SSA with unpolarized target
quark polarization
IWHSS09, Apr 138
SSA with long. polarized target
quark polarization
IWHSS09, Apr 139
SSA with long. polarized target
quark polarization
IWHSS09, Apr 140
CLAS: Fraction from baryonic decays in SIDIS
Significant fraction from target fragmentation at pion momenta below 2 GeV
IWHSS09, Apr 141
Dilution factor in SIDIS
Multiple scattering and attenuation in nuclear environment introduces
additional PT-dependence for hadrons
Fraction of events from polarized hydrogen in NH3
Nu,Np -total counts from NH3 and carbon normalized by lumi
u, p -total areal thickness of hydrogen (in NH3), and carbon target
Cn=Nitr/Carbon ratio (~0.98)Diff. symbols for diff x-bins
-
IWHSS09, Apr 142
Collins Effect: from asymmetries to distributions
Combined analysis of Collins fragmentation asymmetries from SIDIS and e+e- (BELLE) would allow separation of transverse spin distributions (Anselmino et al., arXiv:0707.1197 )
need
Brodsky & Yuan (2006)
CLAS12
IWHSS09, Apr 143
JLab@12GeV: Inclusive DIS
BBS/LSS no OAM
PDF measurements at large x provide additional information on OAM
BBS/LSS with OAM
IWHSS09, Apr 144
Azimuthal Asymmetries in SIDIS
Due to color coherence the configuration with gluon inside the quark cone is more probable
Why <cos> < 0 ? Chay,Ellis,Stirling-1991
x
=180
=0
IWHSS09, Apr 145
HT and Semi-Exclusive Pion Production E. Berger, S. Brodsky 1979 (DY), E.Berger 1980,A.Brandenburg, V. Khoze, D. Muller 1995
A.Afanasev, C.Carlson, C. Wahlquist Phys.Lett.B398:393-399,1997
+
Fragmentation +
0
• Azimuthal asymmetries with opposite sign from HT effects
• Effect may be suppressed for semi-exclusive 0 compared to +/-