A Parasitic Measurement During E03-004 for Target Single-Spin

Asymmetry in Inclusive DIS n↑(e,e Reaction on a Vertically Polarized

3He Target

Tim Holmstromwith Xiaodong Jiang, Todd Averett, Ron Gilman

Hall A Meeting

December 6, 2005

Introduction

• E03-004 plans to measure SIDIS n↑(e,e asymmetry on a transversely polarized 3He target.

• We seek to parasitically measure the inclusive DIS n↑(e,e vertical single-spin asymmetry.

PkkAT

•This will require a change to the BigBite detector package and DAQ.•One day of dedicated beam time for:

• Detector tests and • Systematic studies

Theory• It was shown in the 60’s, by Christ and Lee,

that an inclusive DIS target single-spin asymmetry would be T-violating under these assumptions:

1. One photon exchange.2. No quark mass.3. Other particle exchanges are ignored.

Strong interactions can create T-odd effects in SIDIS, but they are still T-violating in inclusive DIS.

Non-strong interaction T-odd effects that are not T-violating.

exchange

Two-Photon Effects

• For the neutron the net asymmetry due to mass effects must be zero for symmetric u- and d-quark distributions.

mq≠0

uss

qmQQ

QmQ

meeA

q

qqT ˆˆˆ

/4

/41

12

24

222

22

2

If ATn ≠0

Would require chiral symmetry breaking,through a previously unobserved interaction, beyond the leading twist QCD picture of DIS.

Previous Measurement• There is only one previous measurement of the

vertical target single spin asymmetry by S. Rock et al. in 1970.

• Using a vertically polarized butanol target and a 18 GeV electron beam.

• The average for all DIS measurements gives the proton asymmetry is AT

p = ±%. • No new measurement has been published in 35

years.

Goals of this Proposal

Measure the vertical target single-spin asymmetry on the neutron to 104 level.

Control systematic uncertainty to the 104 level.

Provide tight limits on target single spin asymmetries.

DIS ParityAy

Search for new chiral symmetry breaking interactions.

Two order of magnitude improvement First neutron measurement

Big Bite Spectrometer

E03-004 plans to use the standard BigBite electron detector package:

Scintillator trigger plane Three wire chambersLead glass calorimeter

Better particle ID neededfor SSA!

We purpose to add a new Cherenkov Detector

Aerogel CherenkovAn Aerogel (n=1.03) Cherenkov detector can be placed between wire chambers 2 and 3.

A tentative agreement has been reachedwith MIT-Bates and Arizona State to ship parts of the BLAST Aerogel Detector.

Only good for low energy pions

If analysis of the GeN data shows:center wire chamber is not needed by E03-004

Remove that chamber and build a gas cherenkov.

Good for all momentum pions

Trigger DAQ

Single arm trigger

Scintillator plane hit

Number of photons in the Cherenkov

Energy threshold in the calorimeter

Trigger rate of less then 5kHzDeadtime less then 5%.

Aggressive in setting the calorimeter threshold If necessary prescalling the trigger.

Hall A Lumis

• The HAPPEX experiments have built and installed luminosity monitors (Lumis) in the Hall A beam pipe.

• These detectors worked very well at 30 Hz for HAPPEX.

1 Slug of HAPPEX data14 minute time window

A systematic bias of only 5105

3He Polarized Target• E03-004 will use the new

potassium/ rubidium hybrid 3He target.

• These cells will be used for the first time in GeN, and preliminary studies suggest that PT>50%.

• The target will be flipped every 10~20 minutes.

Target densities will need to be monitored.

Spin Duality saw 8104 differences

Expected Results

• E= 6 GeV, target polarization = 42%.• f is the neutron dilution factor.• One Big Bite Setting gets all x bins at once.

<x> E

Gev

e

Deg.

Q2

GeV2

W

GeV

EGeV

d(e,e)

nb/GeV/sr

f Rate

Hz

NDIS

106

ATn

104

0.135 0.815 30.0 1.310 3.050 0.431 29.6 0.350 817.49 776.9 2.44

0.225 1.246 30.0 2.003 2.793 0.398 19.4 0.366 493.42 468.9 3.00

0.315 1.612 30.0 2.592 2.554 0.340 13.0 0.380 281.82 267.8 3.82

0.405 1.925 30.0 3.095 2.331 0.381 8.4 0.391 204.14 194.0 4.37

Kinematics Bite

Results Compared to SLAC proton.

Two order of magnitude improvement!

Systematic UncertaintiesThis measurement will be dominated by systematic uncertainty.

1. Relative luminosity2 background3. Quasi-elastic background

½ of the E03-004 data will be taken with beam in the scattering plane

AT=0 Clear measurement of our total systematic bias

Random quad run structure of target polarization or

Better control of Systematic drifts

Relative Luminosities

L

LNN

L

LNN

Ameas

meassysmeas A

L

LNN

L

LN

A

1

51052

1

L

L

L

L

A sysmeas

After neutron dilution (Aphys)sys= 3.4 10-4

The Hall A Lumis are accurate to 5105 in our time scale.

Luminosity enters directly

as an asymmetry systematic.

Backgrounds: Quasi-Elastic

• The modified Regge GPD model predicts a quasi-elastic signal spin asymmetry Ay=5103, with a 30% uncertainty.

• The Ay experiment E05-015 will test this model giving us a better correction.

For the highest x bin radaitive background is less then 1%.

For the lowest x bin quasi-elastic background of 10%.

Backgrounds: Pions

The p/e ratio:less then 10:1 for the two high x binsless then 100:1 for the lowest x.

Lead glass calorimeter rejection 100 to 1.

Aerogel Cherenkov rejection of 10 to 1 for lowest x Gas Cherenkov rejection of 10 to 1 for all x

The large background will give us the Avery accurately.

Special Run

Reverse BigBite Polarity

Change L-HRS momentum

Coincidence

Clean signal

Relation with other ExperimentsJefferson Lab is unique

High luminosity polarized 3He target

Large acceptance of the BigBite spectrometer

+

Unique Physics reach=

HERMES has data with the target spin normal to the scattering angle

But few polarization flips a year leads to large systematic errors

Systematic Check for these experiments:

Ay, and 12 GeV target single-spin PV

Beam Time Request

• Cherenkov Commissioning, Lumi Check Out, and PID Study.

• Density tests, position measurements, and linearity studies.

Time (Hours)

Production on Pol. 3He 528 (Shared with E03-004)

Reference Cell Runs Optics and Detector Checks

16 (Shared with E03-004)

Target Overhead: Spin Rotation and Polarization

32 (Shared with E03-004)

Systematic Tests, PID Study 24

Total 1 Day (24 hours)

SummaryWe intend to measure the targetsingle-spin asymmetry AT

n on the neutron.In a parasitic experiment to E03-004.

We ask for one day of dedicated beam time:

Checkout of the LumisCheckout of the Aerogel DetectorSpecial systematic measurements 2 hour delta run to get a clean in PID

A large asymmetry would be a signal for previously unseenchiral symmetry breaking beyond the leading twist QCD picture of DIS

Two order of magnitude improvement

First neutron measurement

Overall Systematic Cancellation

• Half of the E03-004 beam time will be spent with target spin left and right of the beamline. Since:

• A full analysis will be done of this data, which will give us a clean measure of our systematic bias.

• The quad run structure of target polarization, the random sequence of orruns will also to better cancel slow drifts in the spectrometer or beam.

• Periodic special runs will be done to understand the behavior of the Lumi and detectors such as:– Target density runs– Beam position off runs– Linearity studies.

0 TT SeeA

Target Polarization Differences

• Polarization differences do not cause asymmetries they only change the size of the asymmetry.

• NMR and EPR will be used to measure the polarization to a relative 4%.

10

10

P

P

0

1

2

PPAmeas

%4. measmeassysT AP

PAA