Min HuangDuke University, TUNL

For the Jefferson Lab Hall A E08-027 (g2p) collaboration

APS A il M i A il 16 h 2013APS April Meeting, April 16th, 2013

E08‐027E08‐027 g2p & the LT Spin Polarizabilityg2 p y Spokespeople

Alexandre Camsonne Graduate Students

Toby Badman Alexandre Camsonne(JLab)

Jian-Ping Chen (JLab)

Toby Badman Melissa Cummings Chao Gu

Don Crabb (UVA) Karl Slifer (UNH)

Post Docs

Min Huang Jie Liu

P ji Zh Post Docs Kalyan Allada James Maxwell

Pengjia Zhu Ryan Zielinski

James Maxwell Vince Sulkosky Jixie Zhang

APS April Meeting 2013   Min Huang 2

Outline Introduction

Physics Motivation

Experimental Setup

Status of Data AnalysisStatus of Data Analysis

APS April Meeting 2013   Min Huang 3

Electron Scattering I l i l i d diff ti l ti

Nevzat Guler’sTalk in G3

Inclusive polarized differential cross section

e (E,k) e’ (E’,k’)θ

( , )

* ( )γ* (ν,q)

P (M 0)W g1, g2: polarized nucleon 

spin structure functionsP (M,0)

4APS April Meeting 2013   Min Huang

How to Obtain gHow to Obtain g2e‐ e‐

e‐

e‐

measured by g2p experiment, essential contribution to g2 in this kinematic region

For the kinematic region not measure for

JLab Hall B EG42 2

2 2d d

d d

, JLab Hall B EG4 data will be combined 2 2

2 2' '

' '' '

td dd dE d dE Ad dE d dEd d

d dE d dE

Will measure both asymmetry and cross section5APS April Meeting 2013   Min Huang

Motivation Measure the proton spin structure function g2 in the low 2

Q2 region (0.02<Q2<0.2 GeV2) for the first time Extract δLT to be a benchmark test of χPT calculationsLT χ Unique opportunity to test the Burkhardt-Cottingham sum

rule Crucial inputs for hydrogen hyperfine splitting and proton

charge radius measurementsgJudith Mcgovern’stalk in Q5

6APS April Meeting 2013   Min Huang

S i LT P l i bilitSpin LT Polarizability

Can be calculated via χPT δ it bl t t t th hi l δLT more suitable to test the chiral

dynamics of QCD (in comparison to the forward spin polarizabilityγ0)

Neutron data show large deviation Neutron data show large deviation from χPT calculations

No proton data yet

7APS April Meeting 2013   Min Huangplot courtesy of V. Sulkosky

lBC Sum Rule2 j t d

H. Burkhardt and W. N. Cottingham, Annals. Phys., 56(1970)453

P

g2p projected

BC satisfied within errors for Neutron

Inconsistency seen in proton data

Mostly unmeasured forN

Mostly unmeasured for proton

8APS April Meeting 2013   Min Huang

Experimental SetupExperimental Setup Large Scale Installation in Hall A Large Scale Installation in Hall A

Transverse polarized NH3 target (2.5/5T field) Low beam current (<100 nA) > new beamline diagnostics

Septa

Low beam current (<100 nA) -> new beamline diagnostics Rasters

S t t

Hall A High Resolution

Septa Septum magnets

BCM Rasters Chicane BPM

L l

Hall A High Resolution Spectrometer (HRS)

LocalDump

Polarized NH3 Target

9APS April Meeting 2013   Min Huang

Achievements DAQ rate is Hall A record Achievements 6~7 kHz/HRS with <30% deadtime

Polarized target performance has been outstanding <PT> >30% @ 2.5T <PT> >75% @ 5T T @

BCM Rasters Chicane BPM

Polarized NH3 TargetTarget Talk by

Melissa

10APS April Meeting 2013   Min Huang

Cummings X15

kinematics Coveragerun concurrently with G prun concurrently with Ge

p

Mp < W < 2 GeV0.02 < Q2 < 0.2 GeV2

Beam E Target Energy /GeV

a geField /T

2 254 2 52.254 2.51.706 2.51.158 2.52.254 5.03.352 5.0

11APS April Meeting 2013   Min Huang

ProjectionsProjections

12APS April Meeting 2013   Min Huang

Status of AnalysisStatus of Analysis

courtesy K. Allada13APS April Meeting 2013   Min Huang

Status of AnalysisStatus of Analysis

Complete! Run Database

Optics Talk by Chao Gu X15u atabase

HRS optics w/o target field Detector calibrations

S l T T lk b

Chao Gu X15

Scalers Offline target polarization calibration

Underway

Target Talk by Melissa Cummings X15y

HRS optics with target field Systematic uncertainty study of target polarization

B iti & t lib ti Beam position & raster calibrations

14APS April Meeting 2013   Min Huang

Online ResultsYield

Y

APS April Meeting 2013   Min Huang 15courtesy R. Zielinski

Online ResultsLongitudinal 5T Asymmetry at E=2.254 GeV

APS April Meeting 2013   Min Huang 16courtesy T. Badman

Summary The g2p experiment ran in spring of 2012 took data The g2p experiment, ran in spring of 2012, took data

covering Mp < W < 2 GeV, 0.02 < Q2 < 0.2 GeV2

A first pass replay of production data is now complete A first pass replay of production data is now complete, and data quality checks are underway!

Will provide a precision measurement of g p in the low Q2 Will provide a precision measurement of g2p in the low Q2

region for the first time Results will shed light on several physics puzzles Results will shed light on several physics puzzles

Thanks to the g2p and Hall A collaboration!Thanks to the g2p and Hall A collaboration!

17APS April Meeting 2013   Min Huang

Backupp

APS April Meeting 2013   Min Huang 18

H d H fi St tHydrogen Hyperfine Structure Hydrogen hyperfine splitting in the ground state has been measuredHydrogen hyperfine splitting in the ground state has been measured

to a relative high accuracy of 10-13

∆S is the proton structure correction and has the largest uncertainty

6 ∆Z can be determined from elastic scattering, -41.0±0.5×10-6

∆pol involves contributions of the inelastic part (excited state), and can be extracted to 2 terms corresponding to 2 different spin-can be extracted to 2 terms corresponding to 2 different spindependent structure function of proton

APS April Meeting 2013   Min Huang 19

H d H fi St tHydrogen Hyperfine Structure

Integrand of ∆2

g2p Experiment

B2 is dominated by low Q2 part

g2p is unknown in this region, so there may be huge eg o , so e e ay be ugeerror when calculating ∆2

This experiment will provide a constrainta constraint

APS April Meeting 2013   Min Huang 20