- 139 Views
- Uploaded on

Download Presentation
## Spin and azimuthal asymmetries in SIDIS at JLAB

**An Image/Link below is provided (as is) to download presentation**

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript

### Spin and azimuthal asymmetries in SIDIS at JLAB

P. Bosted *

Jefferson Lab

SIR-2005

Physics Motivation

Jlab kinematics and factorization

Double spin asymmetries

Single Spin Asymmetries

Future measurements

Summary

* In collaboration with H. Avakian, V.Burkert and L.Elouadrhiri

kT-dependentparton distributions

Semi-Inclusive Deep Inelastic Scattering (SIDIS):

- Probes orbital motion of quarks through quark transverse momentum distribution
- Access to new PDFs not accessible in inclusive DIS.

Off-diagonal PDFs vanish if quarks only in s-state!

In addition T-odd PDFs require FSI

(Brodsky et al., Collins, Ji et al. 2002)

Mulders,

This talk

transversity

Sivers

This talk

P. Bosted, SIR-2005

SIDIS kinematic plane and relevant variables

P. Bosted, SIR-2005

JLab Kinematics and Facorization

- Traditional DIS: W>2 GeV, Q2>1.1 GeV2
- Berger criteriium for current fragmentation

dominance is z>0.4

- Require z<0.7 to avoid diffractive rho meson

contributions (and keep Mx>1.4 GeV)

- Pt<1 GeV (approximately exponential region)
- Study if factorization broken for these cuts using

unpolarized data from E00-108 in Hall C

P. Bosted, SIR-2005

- Close-to-final data analysis
- Small Q2 variation not corrected yet

Hall C E00-108 data

x = 0.32

PRELIMINARY

No visual “bumps and valleys” in pion ratios off deuterium

x = 0.32

PRELIMINARY

P. Bosted, SIR-2005

From E00-108 deuterium data: D-/D+ = (4 – Np+/Np-)/(4Np+/Np- - 1)

z = 0.55

PRELIMINARY

- D-/D+ ratio should be independent of x, and data supports this for W=2.5 GeV, Q2=2.5 GeV2, pt<0.3 GeV
- but should depend on z
- Find similar slope versus z as HERMES, but slightly larger values (could be due to lower average photon energy)

x = 0.32

PRELIMINARY

P. Bosted, SIR-2005

CLAS Experiment Setup and Kinematics

Scattering of 5.7 GeV polarized electrons off polarized NH3, ND3

- ~8M p+ in SIDIS kinematics

x

x

Determination of g1/F1 (approximately A1)

- Target polarization PT about 0.7 (0.3) for NH3 (ND3)
- Beam polarization PB about 0.7
- Dilution factor f varies from 0.1 to 0.3: used Lund
- model for n/p ratio and preliminary Hall B data
- for A-dependence
- Depolarization factor DLL(y) evaluated assuming R
- same as for inclusive.
- Assumed Aperp=0 (not measured)
- No radiative corrections applied
- “p+” and “p-” include some K+, K- for P>1.5 GeV
- p0 events cleanly identified with two photons

x-depenence of SIDIS g1/F1

- Good agreement with
- HERMES p+ data at
- 3x higher Q2
- x-dependence follows PEPSI
- (Lund) Monte Carlo using
- GRSV polarized PDFs (LO)
- Magnitude also in good
- agreement with simulation

P. Bosted, SIR-2005

SIDIS: factorization studies

GRVS

g1/F1 inclusive, for the sum of p+ ,p-, and for p0 are consistent with each other in the range 0.4<z<0.7, as expected in LO with factorization

and current fragmentation dominance

P. Bosted, SIR-2005

z-depenence of SIDIS g1/F1

No significant z-dependence

seen 0.3<z<0.7, as expected

for factorization and current

fragmentation dominance

Good agreement with PEPSI

predictions (including dropoff

at high z for p-)

CLAS 5.7 GeV

PRELIMINARY

P. Bosted, SIR-2005

pt-depenence of SIDIS g1/F1

No pt dependence expected

in LO if current fragmentation

dominance and factorization

Slight pt dependence seen

(but results quite sensitive

to pt dependence of

A-dependence needed

for dilution factor)

Reasonable agreement with

PEPSI predictions.

CLAS 5.7 GeV

PRELIMINARY

P. Bosted, SIR-2005

SIDIS g1/F1 for Deuteron

CLAS 5.7 GeV

PRELIMINARY

Results don’t agree as well with PEPSI using GRSV, more sensitive to un-favored fragmentation function

and NLO corrections than proton (although errors

are about a factor of two larger)

NLO QCD fits including new SIDIS CLAS data can

help constrain polarized PDFs in valence region

Longitudinally Polarized Target SSA

- Clear fdependence

seen for proton

target and p+, p0

- Fit A*sin(f) + B*sin(2f)

for Twist-3 and Twist-2

respectively

P. Bosted, SIR-2005

SSA: x-dependence

Twist-2

Higher Twist

Data in rough

agreement with

Efremov et al.

predictions, except

for p0 sin(f) term

(evidence for terms

not involving Collins

fragmentation?)

5.7 GeV

PRELIMINARY

P. Bosted, SIR-2005

First glimpse of Twist-2 TMD h1L┴

For Collins fragmentation function use HERMES data

Distribution functions from cQSM from Efremov et al

PRELIMINARY

CLAS-5.7GeV

Systematic error only from unknown ratio of favored and unfavored Collins functions (R= H1d→p+/H1u→p+), band correspond to -2.5<R<0

- More data required with p- & p0
- Exclusive 2 pion background may be important

P. Bosted, SIR-2005

Future: more p0 data in SIDIS

advantages:

- SIDIS p0 production is not contaminated by diffractive r
- HT effects and exclusive p0 suppressed
- Simple PID by p0-mass (no kaon contamination)
- Provides complementary to p+/- information on PDFs

disadvantages:

reconstruction efficiency (requires detection of 2g)

P. Bosted, SIR-2005

CLAS+Inner Calorimeter (IC)

IC

IC sE/E=0.0034/E+0.038/√E+0.022

CLAS+IC

CLAS

Reconstruction efficiency of high energy p0 with IC increases ~ 4 times due to small angle coverage

CLAS

IC at CLAS opens new avenue for studies of spin and azimuthal asymmetries of exclusive and semi-inclusiveg, p0,h,r+

P. Bosted, SIR-2005

KM

Longitudinally polarized target SSA using CLAS+IC50 days of CLAS+IC

curves, cQSM from Efremov et al

Hunf=-5Hfav

Hunf=-1.2Hfav

Hunf=0

- Provide measurement of SSA for all 3 pions, extract the Mulders TMD and study Collins fragmentation with longitudinally polarized target
- Allows also measurements of 2 pion asymmetries

Summary

- Spin and azimuthal asymmetries measured at 5.7 GeV with longitudinally polarized target.
- Double spin asymmetries of pions are consistent with factorization and partonic picture: may be used in future NLO QCD fits.
- sinf andsin2f SSA measured, providing access to the twist-2 TMD h1L distribution and testing the Collins fragmentation function
- Future measurements with IC, if approved, will greatly improve p0 data. Much greater improvements for all reactions possible with 12 GeV upgrade due to much larger coverage of DIS kinematics.

P. Bosted, SIR-2005

support slides…..

P. Bosted, SIR-2005

Collins effect and 2 pion production

Sub-leading pion opposite to leading (into page)

Simple string fragmentation (Artru model)

L=1

Leading r opposite to leading p(into page)

r production may produce an opposite sign AUT

r

r+

Understanding of 2 pion asymmetries will help to understand single pion mesurements

r0

P. Bosted, SIR-2005

AULSSA: PT-dependence

HT –SSA significant for p + and p 0

CLAS PRELIMINARY

- sinf SSA p + increases with PT and is consistent with HERMES measurement.

P. Bosted, SIR-2005

Missing mass of pions in ep→e’pX

p0

D++

p-

p+

n

D0

In accessible kinematics (Q2>1.5,W2>4) low MX(large z) for p0 are suppressed by current CLAS acceptance.

P. Bosted, SIR-2005

Download Presentation

Connecting to Server..