# Presentation: 664926

## Spin-Flavor Decomposition

**J. P. Chen, Jefferson Lab**
*** ******PVSA Workshop,  April 26-27, 2007, Brookhaven National Lab***

-  Polarized Inclusive DIS,  ***u/u* and ***d/d* from *A**1**n**/A**1**p*
-  Spin-Flavor decomposition in high-*x* (valence) region
- Polarized Semi-Incluisve DIS
-  Spin-Flavor decomposition in moderate-*x* region
- Polarized Parity-Violating DIS
-  A new window to study sea quark polarization
- JLab 12 GeV upgrade and a large acceptance solenoid detector
- A powerful tool for nucleon spin-flavor decomposition

## Unpolarized and Polarized Structure Functions 

##  Unpolarized Parton Distributions (CTEQ6)

- After 40 years DIS experiments, unpolarized structure of the nucleon reasonably well understood.
- High *x*  valence quark dominating

## NLO Polarized Parton Distributions (AAC06)

## Polarized Inclusive DIS

- Valence Quark Spin-Flavor decomposition at high *x*

## World data for A1  

- Proton

- Neutron

## Precision A1n at High x from Hall AE99-117

- First precision *A**1**n* data at high x
- Extracting valence quark spin distributions
- Test our fundamental understanding of valence quark picture
- SU(6) symmetry
- Valence quark models
- pQCD (with HHC) predictions
- Quark orbital angular momentum
- Crucial input for pQCD fit to PDF
**PRL 92, 012004 (2004)**
**PRC 70, 065207 (2004)**

##  A1p/A1d Results from CLAS

- Proton

- Deuteron

## Naïve Extraction of Polarized Quark Distributions

- Combining *A**1**n* and *A**1**p* results
- Valence quark dominating at high *x*
- u quark spin as expected
- d quark spin stays negative!
- Disagree with pQCD model calculations assuming HHC (hadron helicity conservation)
- Quark orbital angular momentum
- Consistent with valence quark models, pQCD PDF fits without HHC constraint, statistic model
- Consistent with a new model from Feng Yuan *et al.* including OAM

## Projections for JLab at 11 GeV 

**Projections for JLab at 11 GeV **

- A1n at 11 GeV

## Spin Structure with the Solenoid at JLab 12 GeV

- Program on spin structure with polarized target(s) and a solenoid
- highest polarized luminosity: ~1036
**A solenoid with detector package (GEM, Lead-glass+ Cherenkov)**
-             large acceptance: ~700 msr for polarized
-       high luminosity and large acceptance
**Inclusive DIS: improve by a factor of 10-100**
*            **A**1* at high-x: 200 hours, high precision
-             parity violating spin structure *g**3**/g**5* : first significant measurement
**SIDIS: improve by a factor of 100-1000**
-             spin-flavor decomposition (~2 orders improvement)
-             transversity and TMDs,

## Solenoid detector for (SI)DIS

- 3He target

**Solenoid detector for (SI)DIS**

- GEMs

- Gas Cerenkov

- Calorimeter

- GEMs

- With Standard HMS+SHMS,
-      1800 hours
-      (X. Zheng)
- With Solenoid,
-      200 hours

## Polarized Semi-inclusive DIS

- Spin-Flavor decomposition at moderate *x*

## Flavor decomposition with SIDIS

- With standard HMS+SHMS(see X. Jiang’s Talk)     compared with HERMESWith Solenoid,   2 orders of magnitude    improvement

## Polarized Sea with SIDIS

- Polarized Sea

- With standard  HMS+SHMS (X. Jiang’s talk)   compared with HERMESWith Solenoid,   2 orders of magnitude    improvement

## Polarized Parity Violating DIS

- Sea quark polarization

## Longitudinal Target Single Spin Asymmetry

- Unpolarized beam on longitudinally polarized target
-     keep *Z* interference terms, neglect *Z**2* terms

- g1Z term can be eliminated by using positron beam

## PV-SSF in Naïve Parton Model

- Naïve Parton Model:

- Put back into the general formula, we get

*g*3 provides access to polarized sea quark distributions.
- Potential access to polarized strange quark distributions.

## Measure PV-TSSA with the Selonoid 

- At *x*=0.2, *Q**2*=2.4, *y*=0.58,  *A*~ 10-5-10-4
- Need high luminosity and large acceptance
- Rate estimation with the Solenoid detector:
-    1000 hours beam, statistical precision for asymmetry
-       will be a few x 10-5.
-              A significant first measurement (~ a few )

## Projection of Collins/Sivers Asymmetries vs PT and x for + (60 days)

- For one z bin
-      (0.5-0.6)
- Will obtain 4
-      z bins (0.3-0.7)
- Also - at same
-      time
- With upgraded
-     PID for K+ and K-

## Summary

-     Spin-Flavor decomposition:
- Polarized inclusive DIS in high-x region
-   Valence quark polarization
- Polarized semi-inclusive DIS in moderate-x region
-   Valence and sea quark polarization
- Polarized parity violating DIS
-   A new tool to study sea quark polarization
- A large acceptance solenoid with high luminosity
-   700 msr, 1036 polarized (n) luminosity
-   Improvement of a factor of 10-100 in acceptance*luminosity