1. Transverse distributions of polarized quarks
Harut Avakian (JLab)
January 22-24, 2015
Thomas Jefferson National Accelerator Facility
H. Avakian, JLab, Jan 23

2. 3D structure of the nucleon
TMDs
Semi-Inclusive processes and transverse momentum distributions up
down
Hard exclusive processes and spatial distributions of partons
Pasquini & Yuan
g,h
GPDs
Combination of polarized and unpolarized targets and large acceptance coverage of CLAS12 allows studies of GPDs in a wide kinematic range.
(QCDSF)
H. Avakian, JLab, Jan 23

3. Quark distributions at large kT: lattice
B.Musch et al arXiv:
g1q=Dq=(q+-q-)/2
B.Pasquini et al
arXiv:
One of the biggest surprises from lattice was significant dependence of transverse momentum distributions on the spin orientation. You can see that ratio of u+(quark spin aligned with proton)/u- and quark spin antialigned is going down with K_T of the quark.
distributions of PDFs may depend on flavor and spin (lower fraction aligned with proton spin at large kT,bT) 3
Avakian, Jlab May 28

4. Flavor separation of form factors
Quark transverse charge densities inside an unpolarized proton arXiv:
G. Cates et al. PRL 106 (2011)
Q4F2q/k
Q4 F1q
space distributions depend on flavor and spin (modify in medium)
G. Miller et al (2011 )
form factors of the nucleon fell off faster in nuclear matter
H. Avakian, JLab, Jan 23

5. 3D structure: GPDs epe’pp0
CLAS e1dvcs
Lattice (QCDSF)
DVCS asymmetries measured at HERMES & JLAB
More measurements at
JLab, Compass
using the handbag approach based on factorization in hard parton subprocesses and soft generalized parton distributions (GPDs)
GPDs describing unpolarized and longitudina;ly polarized quarks can be accessed in the DVCS process.
Transverse photon dominates the x-section for exclusive p0 production
Spin-azimuthal asymmetries in hard exclusive production of photons and pions give access to underlying GPDs
H. Avakian, JLab, Jan 23

6. Unpolarized beam, longitudinal target (TSA) :~
t-dependence of H
Unpolarized beam, longitudinal target (TSA) :
DsUL ~ sinfIm{F1H +x(F1+F2)(H + xB/2E) –xkF2 E+…}df ~
Im{Hp, Hp}
H. Avakian, JLab, Jan 23

7. t-dependences of HT epe’pp0 Goldstein, Liuti et al
P.Kroll & S. Goloskokov
The production amplitude at large Q2 factorizes into the hard subprocess and GPDs
Within the handbag approach g*Tp transitions are related to transversity (helicity-flip) GPDs accompanied by a twist-3 pion wave function
Hard partonic subprocess
A.Kim’s talk
CLAS12 can measure Q2 dependence of HT SSAs significantly extending the range of CLAS
H. Avakian, JLab, Jan 23

8. Studies of Chiral-Odd GPDs in Hard Exclusive Pseudoscalar Meson Production Using the CLAS12 Detector
PAC42 LoI
H. Avakian, JLab, Jan 23

9. flavor decomposition of underlying chiral-odd GPDs.
Outline
We propose a combination of measurements of cross sections, spin and azimuthal asymmetries with a longitudinally polarized beam and both unpolarized and longitudinally polarized proton target providing a
flavor decomposition of underlying chiral-odd GPDs.
Exclusive production of pseudoscalar mesons
Chiral-Odd GPDs and transverse photon
Studies of Transversity and GPD ET
Exclusive kaon production and separation of different channels _
H. Avakian, JLab, Jan 23

10. Exclusive kaon production
Unlike p+ the K+ x-section is totally dominated by the transverse photon
pole contribution negligible
Exclusive production of KL and KS provide access to different combinations of chiral-odd GPDs
H. Avakian, JLab, Jan 23

11. SSAs in exclusive kaon production
Goloskokov&Kroll
KS asymmetries are predicted to be large and with opposite sign to KL
Goldstein, Hernandez, & Liuti
Beam and target asymmetries in exclusive production of KL and KS are very sensitive to chiral-odd GPDs.
H. Avakian, JLab, Jan 23

12. K/K* and L/S separation
Due to detector resolution clean separation of different channels (L,S,K*) will require detection of 4 particles
H. Avakian, JLab, Jan 23

13. K+ L/S separation K+
Detection of K+ p and p- would allow to separate of different final states (L,S,K*) q L
H. Avakian, JLab, Jan 23

14. Exclusive L/S separation
Detection of the complete final sate allow separation of exclusive Ss
H. Avakian, JLab, Jan 23

15. GPDs from cross section ratios
M.Diehl et al. hep-ph/
K*+ K+
Study ratio observables: K/K*/r+,polarization transfer
Different final state mesons filter out different combinations of unpolarized (H,E) and polarized (H,E) GPDs.
H. Avakian, Glasgow, May 13

16. Summary
Understanding of transverse space distributions of polarized quarks is crucial for interpretation of exclusive production of photons and pions
Identification of Kaons will significantly enhance CLAS12 capabilities to study exclusive processes involving kaons.
Combination of DVCS measurements from CLAS12 with unpolarized, longitudinally and transversely polarized targets would allow studies of chiral-odd GPDs
Measurements of hard-exclusive production of photons and pseudoscalar mesons will help to accomplish the CLAS12 program of studies of the 3D structure of the nucleon
Nead GPD/CFF extraction framework with controlled systematics.
H. Avakian, JLab, Jan 23

17. Support slides….
H. Avakian, JLab, Jan 23

18. Exclusive p0 rates higher for small W sT – dominates for p0. dsT /dt
dsL /dt
K2⊥/Q2 corrections in the propagators of the hard subprocess amplitude are essential in the description of the cross section at low Q2. They decrease s
by a factor of about 10 at Q2 ∼ 3GeV2
M 0+,++ amplitude is important in s T .
H. Avakian, JLab, Jan 23

19. Exclusive p+ cross sections in modified perturbative approach
For π+ production the p → n transition GPDs are required which are given by the isovector combination of proton GPDs F(3) = Fu − Fd .
The γ∗q → πq subprocess amplitudes within the modified perturbative approach is defined
Fourier transform to b space
momentum fraction of the quark defined with respect to the meson momentum
transverse cross section for large t
(−t>∼ 0.2 GeV2) is larger than the longitudinal one
H. Avakian, JLab, Jan 23

20. Transverse densities in the nucleon in nuclear matter
Quark transverse charge densities inside an unpolarized proton arXiv:
Skyrme model
proton
medium
in-medium modied Skyrme model.
form factors of the nucleon fell off faster in nuclear matter
the size of the nucleon tends to bulge out in nuclear matter.
H. Avakian, JLab, Jan 23

21. Exclusive p+/p0
arXiv:
Different transverse moments will give access to different combinations of GPDs
H. Avakian, JLab, Feb 24