29 March 2017 CLAS Collaboration Meeting 1

Semi-Inclusive π0 target and beam-target asymmetries from 6 GeV electron scattering with CLAS

Keith Griffioen William & Mary

for the EG1-DVCS Analysis Group 29 March 2017

29 March 2017 CLAS Collaboration Meeting

TMDs

2

• Any confined quark must have transverse momentum • Therefore, colinear PDFs cannot give the whole story • Transverse momentum is related to Lz • There has been much recent work trying to understand

transverse momentum distributions (TMDs)

29 March 2017 CLAS Collaboration Meeting

Semi-Inclusive DIS

3

29 March 2017 CLAS Collaboration Meeting

SIDIS Cross Section

4

Bacchetta, et al., JHEP 2(2007)093

Leading Twist

Sub-Leading Twist (extra factor of 1/Q)

0 (i.e. R=σL/σT=0)

AUL = {UL terms} / {UU terms}

ALL = {LL terms} / {UU terms} etc.

29 March 2017 CLAS Collaboration Meeting

TMD Structure Functions

5

The Sivers structure function

Unpolarized structure function; integrates to F1(x,Q2)

Unpolarized fragmentation function; integrates to D1(z,Q2)

Polarized structure function; integrates to g1(x,Q2)

The Collins fragmentation function

And there are more...

29 March 2017 CLAS Collaboration Meeting

Primary TMDs

6

Red: T-odd Yellow box: chiral-odd

Black: survive pT integration

Helicity

SiversTransversity

Pretzelocity

Boer-Mulders

Worm Gear

29 March 2017 CLAS Collaboration Meeting

Collins Fragmentation

7

Artru, Acta Phys. Polon. B39(1998)2115

• Imagine that the qq pair is created in a 3P0 spin state with vacuum quantum numbers JPC=0++

• Quark spins are opposite the orbital ang. mom. L=1 • Pion (with no spin) acquires transverse momentum • This simple model breaks down if the fragmentation

string does not conserve J (i.e. if there are torques)

X

Struck quark

π

pT

29 March 2017 CLAS Collaboration Meeting

• Beam time: February to September 2009 • ~6 GeV Polarized electron beam (Pb~85%) • Frozen 14NH3 target (Pt~75%) • CEBAF large acceptance spectrometer

(CLAS) plus Inner Calorimeter • ~19 billion electron triggers on NH3 target

EG1-DVCS at JLab

86

Hall B

Hall BHall B

xπ+ π- π00.6

0.1

Q2 (GeV2) 0 6

29 March 2017 CLAS Collaboration Meeting

Inner Calorimeter

9

π0→γγ

29 March 2017 CLAS Collaboration Meeting

Polarized Target

10

14NH3, 14DH3, C Targets

Dynamic Nuclear Polarization

29 March 2017 CLAS Collaboration Meeting

Asymmetries

11

29 March 2017 CLAS Collaboration Meeting

ALU, AUL, ALL

12

29 March 2017 CLAS Collaboration Meeting

π0 Reconstruction

13

4ns 40 MeV

60 MeV45

MeV

IC IC-IC

EC-IC EC-EC

29 March 2017 CLAS Collaboration Meeting

π0: IC-IC & EC-EC

14IC-IC EC-EC

29 March 2017 CLAS Collaboration Meeting

PbPt

15

PbPt for bottom target in Part B of Experiment deduced from polarized elastic asymmetries

Pb measured using Moller Scattering

29 March 2017 CLAS Collaboration Meeting

Dilution Factor

16

29 March 2017 CLAS Collaboration Meeting

Radiative Corrections

17

Complete lowest order radiative corrections to five-fold differential cross-section of hadron leptoproduction I. Akushevich (Duke U.), A. Ilyichev (Minsk, High Energy Phys. Ctr.), M. Osipenko (INFN, Genoa & SINP, Moscow). Nov 2007. 15 pp. Published in Phys.Lett. B672 (2009) 35-44 DOI: 10.1016/j.physletb.2008.12.058

Radiative effects in the processes of exclusive photon electroproduction from polarized protons Igor Akushevich (Duke U. & Jefferson Lab), Alexander Ilyichev (Fermilab & Minsk, High Energy Phys. Ctr.). Jan 2012. 11 pp. Published in Phys.Rev. D85 (2012) 053008 JLAB-PHY-11-1475 DOI: 10.1103/PhysRevD.85.053008

CLAS Collaboration (P.E. Bosted (William-Mary Coll.) et al.). Nov 15, 2016. 12 pp. Published in Phys.Rev. C95 (2017) no.3, 035207 JLAB-PHY-16-2388 DOI: 10.1103/PhysRevC.95.035207

CLAS Collaboration (P.E. Bosted (William-Mary Coll.) et al.). Jul 25, 2016. 12 pp. Published in Phys.Rev. C95 (2017) no.3, 035206 JLAB-PHY-16-2294 DOI: 10.1103/PhysRevC.95.035206

CLAS Collaboration (P.E. Bosted (William-Mary Coll.) et al.). Apr 15, 2016. 25 pp. Published in Phys.Rev. C94 (2016) no.5, 055201 JLAB-PHY-16-2294 DOI: 10.1103/PhysRevC.94.055201

SIDIS radiative corrections are dominated by exclusive processes that radiate into the deep-inelastic region

29 March 2017 CLAS Collaboration Meeting

ALU

18

29 March 2017 CLAS Collaboration Meeting

AUL

19

29 March 2017 CLAS Collaboration Meeting

ALL

20

29 March 2017 CLAS Collaboration Meeting

Monte Carlo Simulations

21

29 March 2017 CLAS Collaboration Meeting

g1/f1

22

29 March 2017 CLAS Collaboration Meeting

g1/f1 vs. PT

23

29 March 2017 CLAS Collaboration Meeting

AUL Sin(2Φ) Moments

24

Collins fragmentation function H1⊥ is large and has opposite sign for the favored and unfavored cases. This suggests a significant suppression of the Collins fragmentation function for π0

29 March 2017 CLAS Collaboration Meeting

AUL Sin(Φ) Moments

25

. Data suggest that a Sivers-type contribution coming from the convolution of fL⊥ and D1

29 March 2017 CLAS Collaboration Meeting

Conclusions

26

29 March 2017 CLAS Collaboration Meeting

Fine

27

End

29 March 2017 CLAS Collaboration Meeting

EG1-DVCS Experiment

28

Ran February through September 200914NH3 and 14ND3 Targets

80% and 30% polarizations, respectively