1. Spokespersons P. Bosted, R. Ent,, E. Kinney and H. Mkrtchyan
Transverse Momentum Dependence of Semi-Inclusive Pion and Kaon Production E
Spokespersons P. Bosted, R. Ent,, E. Kinney and H. Mkrtchyan
Not much is known about the orbital motion of partons
Significant net orbital angular momentum of valence quarks implies significant transverse momentum of quarks
Main goal: Map the pT dependence (pT ~ L < 0.5 GeV) of p+ and p- production off proton and deuteron targets to study the kT dependence of (unpolarized) up and down quarks
Beam Time Request: days at 8.8 GeV
25.5 days at 11.0 GeV
Total: days
About 2/3 of running time scheduled for 2017 in Hall C

2. Transverse Momentum Dependence of Semi-Inclusive Pion and Kaon Production
Outline:
SIDIS: general remarks and framework
Transverse momentum dependence of charged pions
- Results from E & simple model analysis
E Kinematics and Projected Results
Spin-off relevant for the general SIDIS program
Radiative correction modeling: linking to z = 1
Single-spin asymmetries
Low-energy (x,z) factorization for charged kaons
The upcoming run preparations

3. Semi-Inclusive Deep-Inelastic Scattering
Use advantages of multi-hall approach!
Hall B: Large acceptance (CLAS12), polarized H and D targets
 azimuthal distributions of final-state particles
 cross sections, single & double-spin asymmetries
 start kaon SIDIS program with RICH detector
Hall A: Large acceptance in forward region with SOLID, Polarized 3He target
 longitudinal & transversely polarized 3He
 pion & kaon run with BigBite and SBS
 Access to n structure at high-x and high-Q2
Hall C: Precision magnetic-spectrometer setup, p and K, high luminosity
 L/T separations in SIDIS
 precision cross sections and ratios of p+ and p- (and K+, K-)

4. SIDIS – kT Dependence Pt = pt + z kt + O(kt2/Q2) TMDu(x,kT)
Final transverse momentum of the detected pion Pt arises from convolution of the struck quark transverse momentum kt with the transverse momentum generated during the fragmentation pt.
Pt = pt + z kt + O(kt2/Q2)
Linked to framework of Transverse Momentum Dependent Parton Distributions
TMDu(x,kT)
f1,g1,f1T ,g1T
h1, h1T ,h1L ,h1 p m x
TMD

5. Transverse momentum dependence of SIDIS
Linked to framework of Transverse Momentum Dependent Parton Distributions p m X
TMD
N q U L T f1 h1 g1
h1 L
f1T
g1T
h1 h1T
Unpolarized target
Longitudinally pol. target
TMDq(x,kT)
Transversely pol. target
Unpolarized kT-dependent SIDIS: in framework of Anselmino et al. described in terms of convolution of quark distributions q and (one or more) fragmentation functions D, each with own characteristic (Gaussian) width  Emerging new area of study
I. Integrated over pT and f
Hall C: PRL 98: (2007)
Hall B: PRD 80: (2009)
II. PT and f dependence
Hall B: PRD 80: (2009)
Hall C: PL B665 (2008) 20
Hall C: PR C85 (2012)  

6. SIDIS Formalism
General formalism for (e,e’h) coincidence reaction w. polarized beam:
[A. Bacchetta et al., JHEP 0702 (2007) 093]
(Y = azimuthal angle of e’ around the electron beam axis w.r.t. an arbitrary fixed direction)
Use of polarized beams will provide useful azimuthal beam asymmetry measurements (FLU) at low pT complementing CLAS12 data

7. Transverse momentum dependence of SIDIS
General formalism for (e,e’h) coincidence reaction w. polarized beam:
[A. Bacchetta et al., JHEP 0702 (2007) 093]
(Y = azimuthal angle of e’ around the electron beam axis w.r.t. an arbitrary fixed direction)
Azimuthal fh dependence crucial to separate out kinematic effects (Cahn effect) from twist-2 correlations and higher twist effects.
data fit on EMC (1987) and Fermilab (1993) data assuming Cahn effect → <m02> = 0.25 GeV2
(assuming m0,u = m0,d)

8. Transverse momentum dependence of SIDIS
Pt dependence very similar for proton and deuterium targets
Pt dependence very similar for proton and deuterium targets, but deuterium slopes systematically smaller?

9. Unpolarized SIDIS – JLab E00-108 data
Constrain kT dependence of up and down quarks separately
1) Probe p+ and p- final states
2) Use both proton and neutron (d) targets
3) Combination allows, in principle, separation of quark width from fragmentation widths
Example
1st example: Hall C, PL B665 (2008) 20
Numbers are close to expectations! But, simple model only with many assumptions (factorization valid, fragmentation functions do not depend on quark flavor, transverse momentum widths of quark and fragmentation functions are gaussian and can be added in quadrature, sea quarks are negligible, assume Cahn effect, etc.), incomplete cos(f) coverage, uncertainties in exclusive event & diffractive r contributions.
<pt2> (favored)
<kt2> (up)
x = 0.32
z = 0.55
Example

10. Transverse Momentum Dependence: E00-108 Summary
E results were only suggestive at best:
limited kinematic coverage
- assumed (PT,f) dependency ~ Cahn effect
very simple model assumptions
but PT dependence off D seems shallower than H
Many limitations could be removed with 12 GeV:
wider range in Q2, higher W, Mx
improved/full coverage in f (at low pT)
larger range in PT
wider range in x and z (to separate quark from fragmentation widths)
possibility to check various model assumptions
Power of (1-z) for D-/D+, quantitative contribution of Cahn term
Dup+ = Ddp-, Higher-twist contributions
consistency of various kinematics (global fit vs. single-point fits)

11. Choice of E12-09-017 Kinematics
W2 = 5.08 GeV2 and larger (up to GeV2)
Use SHMS angle down to 5.5 degrees (for p detection)
HMS angle down to 10.5 degrees (e- detection)
separation HMS-SHMS > 17.5 degrees
MX2 = Mp2 + Q2(1/x – 1)(1 – z) > 2.9 GeV2 (up to 7.8 GeV2)
Choice to keep Q2/x fixed  qg ~ constant
exception are data scanning Q2 at fixed x
All kinematics both for p+ (and K+) and p- (and K-), both for LH2 and LD2 (and Al dummy)
Choose z > 0.3 (pp > 1.7 GeV) to be able to neglect
differences in s(p+N) and s(p-N)

12. Choice of Kinematics
HMS + SHMS Accessible Phase Space for Deep Exclusive Scattering
All together: data base of precise SIDIS cross sections over nice range of x and Q2!
11 GeV phase space E
Scan in (z,pT)
No scan in Q2 at fixed x: RDIS(Q2) known
6 GeV phase space E
Scan in (x,z,pT)
E00-108
+ scan in Q2
at fixed x C
+ scans in z
For semi-inclusive, less Q2 phase space at fixed x due to:
i) MX2 > 2.5 GeV2; and ii) need to measure at both sides of Qg

13. Choice of Kinematics – cont.x
Q2 (GeV2) Z
Pp (GeV)
Qp (deg) I
0.2
2.0
1.7 – 3.3
8.0 – 23.0 II
0.3
3.0
1.7 – 3.4
5.5 – 25.5
III
0.4
4.0 IV
0.5
5.0
1.7 – 3.5
8.0 – 28.0 V
1.8
1.1 – 2.1
8.0 – 30.5 VI
4.5
2.5 – 5.0
5.5 – 20.5
Map of pT dependence in x and z,
in Q2 to check (pT/Q) and (pT2/Q2) behavior
Kinematics I, II, III, and IV are identical to those where this collaboration also plans to map R (= sL/sT) in SIDIS in E These are the priority for 2017 run.

14. E12-09-017: PT coverage f = 90o Excellent f coverage
Can do meaningful measurements at low pT (down to 0.05 GeV) due to excellent momentum and angle resolutions!
f = 90o
Excellent f coverage
up to pT = 0.2 GeV
Sufficient f coverage
up to pT = 0.4 GeV
(compared to the E00-108
case below, now also good
coverage at f ~ 0o)
Limited f coverage
up to pT = 1 GeV
pT = 0.6
pT = 0.4
f = 180o
f = 0o
E00-108
f = 270o
PT ~ 0.5 GeV: use f dependencies measured in CLAS12 experiments (Run group A in particular)

15. C12-09-017 Projected Results - I
III IV II VI I V

16. Kaon Identification Particle identification in SHMS:
0) TOF at low momentum (~1.5 GeV)
Heavy (C4F8O) Gas Cherenkov
to select p+ (> 3 GeV)
60 cm of empty space can be used
for two aerogel detectors, e.g.:
- n = to select p+ (> 1 GeV)
select K+ (> 3 GeV)
- n = to select K+ (>1.5 GeV)
NSF-MRI grant to
Catholic U (lead)
U South Carolina
Mississippi State
Florida Intern. U
(+ Yerevan + JLab)

17. Spin-off: study x-z Factorization for kaons
P.J. Mulders, hep-ph/ (EPIC Workshop, MIT, 2000)
At large z-values easier to separate current and target fragmentation region  for fast hadrons factorization (Berger Criterion) “works” at lower energies
If same arguments as validated for p apply to K:
At W = 2.5 GeV: z > 0.6
(but, z < 0.65 limit may not apply for kaons!)

18. E12-09-017 Projected Results - Kaons
III IV II VI I V

19. Systematic Uncertainties – the z  1 Limit
From: G. Huber’s presentation on PR “Measurement of the Charged Pion Form Factor to High Q2”
Projected Systematic
Uncertainty
Source
Pt-Pt
ε-random
t-random
ε-uncorrelated
common to all t-bins
Scale
ε-global
t-global
Spectrometer Acceptance
0.4%
1.0%
Target Thickness
0.2%
0.8%
Beam Charge -
0.5%
HMS+SHMS Tracking
0.1%
1.5%
Coincidence Blocking
PID
Pion Decay Correction
0.03%
Pion Absorption Correction
MC Model Dependence
Radiative Corrections
2.0%
Kinematic Offsets
Added in quadrature: 1.8%

20. The beam helicity asymmetry
Proportional to sin(f), must go to zero at Pt=0
Interference term (L-T prime)
Very sensitive to details of interactions
Example: dramatic influence of Roper resonance in exclusive p+ electroproduction
Typical asymmetry 0.05: need lots of statistics

21. Run Preparations Re-optimize run plan taking into account:
2x higher accidental rates than in proposal
Data at 4-pass and maybe 3-pass for
radiative correction modeling. Also,
Need some data at 0.6<z<1 at 5-pass.
Difficulties in going to small SHMS angles
5 pass energy of 10.6 GeV

22. Adding option of measurements w/Carbon
Run Preparations
Adding option of measurements w/Carbon
Plan to add to “dummy” target and
Use z-resolution of HMS to distinguish
Needed for CLAS12 analysis with
polarized ammonia
Physics: Propogation of quarks through nuclei

23. Personael and Collaboration
Run Preparations
Personael and Collaboration
Great opportunity for PhD thesis!
Great opportunity for post-docs!
And for young faculty members too.