Studies of TMDs with CLAS & CLAS12 P. Rossi Laboratori Nazionali di Frascati - INFN On behalf of the CLAS Collaboration Introduction SIDIS experiments @ JLab with CLAS Results @ 6 GeV CLAS12 and TMDs studies @ 12 GeV Conclusions May 18-21, 2010TJNAF-Newport News, Virginia USA
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Studies of TMDs with CLAS & CLAS12 P. Rossi Laboratori Nazionali di Frascati - INFN On behalf of the CLAS Collaboration Introduction SIDIS experiments.
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Studies of TMDs with CLAS & CLAS12
P. Rossi Laboratori Nazionali di Frascati - INFNOn behalf of the CLAS Collaboration
IntroductionSIDIS experiments @ JLab
with CLASResults @ 6 GeVCLAS12 and TMDs studies @ 12
GeVConclusions
May 18-21, 2010TJNAF-Newport News, Virginia USA
Introduction
Nucleon is a complex object
Our goal is:
Study its STRUCTURE
3D image (coord. &
mom.) Spin origin Flavor content
Understand CONFINEMENT
Transverse Momentum dependent parton Distribution functions (TMDs) are relevant for all these issues
SIDIS experiments and SSAs
Inclusive DIS experiments- 2D image (collinear approx.)- unable to account for all the nucleon spin
k’, E’k, E
DF
€
1
2=
1
2ΔΣ + ΔG + Lq
Observable are Single Spin Asymmetry (SSAs) which are due to correlations between transverse momentum of quarks (k) and the spin of the quark/nucleon
moments of s
Semi-Inclusive DIS experiments- 3D image in momentum space- Access quark orbital momentum Lq
ep e’X DIS kinematics: Q2>1 GeV2, W2>4 GeV2, y<0.85
1) Longitudinally Polarized NH3/ND3 (no IC, ~5 days) 20012) Longitudinally Polarized NH3/ND3 with IC 60 days
20093) Unpolarized H
with IC ~60 days 20054) Transversely Polarized HD-
Ice (no IC, 25 days)
2011 (?)
AUL, ALL: arXiv:1003.4549Submitted to PRLNew data under analysisExperiment E05-113 0 BSA Analysis completedAnalysis note under coll. reviewExperiment in preparation
Q2
SIDIS with CLAS @ 6 GeV
CLAS program: extraction of leading twist and higher twist TMDs
quark-gluon-quark correlations responsible for azimuthal moments of h.t.
€
ALUsin(φ ) 0 BSA
UU
U U
€
AULsin(2φ )0/+/- TSA
LL
L L
€
ALLPT-dependence
Pion SSA with unpol./long. Polarized target
Transversely polarized quarks in a longitudinally polarized nucleon
Different width of TMDs of quarks with different flavor and polarizations
€
R =k⊥width dist(g1)
k⊥width dist( f1)
R=0.40
R=0.68
R=1.0
f1=0.25 GeV2
• Data shows slight preference for R<
H. Avakian et al. arXiv:1003.4549
+ 0 -
• New experiment with 10 times more data will study the PT-dependence for different quark helicities and flavors for bins in x
Projected results for Exp. E05-113
Longitudinal pol. Target: A1-PT dependence
( ) −+
−+
+−
=NN
NN
PALU
1φ
€
ALUsin(φ )e p e’ X
BSA ~ sin insensitive to other harmonics
BSA: Asymmetry extraction and fitting for 0
M Aghasyan, LNF-INFN
• Drop with PT below 1 GeV/c
• ALU in agreement with HERMES data
M Aghasyan, LNF-INFN
• Comparable BSA for 0 and +
Small Collins type contributions for +?M Aghasyan, LNF-INFN
⎪⎪⎩
⎪⎪⎨
⎧
⊗+⊗
⊗−⊗∝
⊥⊥
⊥⊥
z
EhHxe
z
Gf
M
MDxg
M
M
F
h
hLU
1
1
1
1
Main contribution?
0 BSA Asymmetry results
Target used by LEGS at BNL with photon beamPros
• Small field (∫Bdl~0.005-0.05Tm)• Small dilution factor• Less radiation length• Less nuclear background • Wider acceptance• much better FOM, especially for deuteron
Cons• HD target is highly complex and there is a need for
redundancy due to the very long polarizing times (months). • Need to demonstrate that the target can remain polarized
for long periods with an electron beam with currents of order of 1-2 nA
• HDice installation in the Hall January 2011• photon run with HD-ice March 2011• test run with e- end of Apr 2011• physics run with e- t.b.d.
The target is now at Jlab and all equipment moved to the new HDice lab
Transversely polarized HD-ice target
Tentative schedule
⊥⊥ ⊗∝11
)3( HhF TUT
11)1( DfF TUT ⊗∝ ⊥
Sivers
⊥⊗∝11
)2( HhFUT Collins
Sivers TMD
transversity TMD
Collins FF
pretzelosity TMD
Collins FF
( )STUT DfF φφ −⊗∝ ⊥ sin11)1(
Projected results for 30 days of CLAS at 6 GeV in 2011 (PT=75% L=5.1033cm-2s-1 )
CLAS will provide a superior measurements of Sivers asymmetry at large x, where the effect is large and models unconstrained by previous measurements.
curves from Yuan, Efremov,Collins
TMDs with transversly polarized target
Hall A
•Beam: 6 GeV, 15 A (target limit)•Neutron Target: High pressure polarized 3He, 50 mg/cm2, Pol. ~
60%•Hadron Detection: HRS Left Ph = 2.4 GeV/c, /K ID•Kinematic Region<Q2> = 2.2 GeV2, x = 0.130.4, z ~ 0.5
e-
+/-
1 month data taking:
statistical errors comparable to
HERMES(3 years)/COMPASS(2 years)
•Analysis underway
TMDs on a transversely pol. neutron in HALL A
Transverse degrees of freedom led to a bunch of new, more complex, distribution and fragmentation functions
Unpolarized and polarized data from different Laboratories are giving a first look at these new functions
A new generation of experiments is necessary to fully exploit the properties of TMDs, with
- wide kinematic coverage- high luminosity- high polarization- high capability of final hadron separation
Complete program of TMDs studies for pions and kaons
Kaon measurements crucial for a better understanding of the TMDs “kaon puzzle”
Kaon SIDIS program requires an upgrade of the CLAS12
detector PID RICH detector to replace LTCCProject under development
TMDs program @ 12 GeV in Hall B
Kaon TMDs program @ 12 GeV in Hall B
K+
K--
+
• K+ ampl. > + ampl. Unespected from u-quark dominance!
• How large can the effect of s quarks be?
HERMES coll. PRL 103 (2009)
/K measurement @ CLAS12 will provide a more detailed knowledge of Sivers effect
epe’K+X
S.Arnold et al.0805.2137
M. Anselmino et al.0805.2677
Measurements of azimuthal dependences of single and double spin asymmetries indicate that correlations between spin and transverse motion of quarks may be significant
CLAS in Hall B at Jlab is playing a major role in these studies
The new CLAS experiment with longitudinally polarized NH3 and ND3 targets provides superior sample of events allowing multidimensional binning to study:
- SSAs for and in SIDIS- Higher Twists and quark-gluon correlations - Double spin asymmetries and flavor
decomposition of helicity dist.
Studies of the spin-structure of the nucleon is one of the main driving forces behind the upgrade of Jefferson Lab
JLab12 with wide kinematic coverage, high luminosity, high polarizationis essential for high precision measurements of 3D PDFs in the valence region