A Parasitic Measurement During E03004 for Target SingleSpin Asymmetry in Inclusive DIS ne,e Reaction

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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 Holmstrom
• with Xiaodong Jiang, Todd Averett, Ron Gilman
• Hall A Meeting
• December 6, 2005

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Introduction

• E03-004 plans to measure SIDIS n?(e,p-e?)
  asymmetry on a transversely polarized 3He target.
• We seek to parasitically measure the inclusive
  DIS n?(e,e?) vertical single-spin asymmetry.

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

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Theory

• It was shown in the 60s, by Christ and Lee, that
  an inclusive DIS target single-spin asymmetry
  would be T-violating under these assumptions

• One photon exchange.
• No quark mass.
• Other particle exchanges are ignored.

Strong interactions can create T-odd effects in
SIDIS, but they are still T-violating in
inclusive DIS.
gg exchange
Non-strong interaction T-odd effects that are not
T-violating.
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Two-Photon Effects
mq?0

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

Would require chiral symmetry breaking, through a
previously unobserved interaction, beyond the
leading twist QCD picture of DIS.
If ATn ?0
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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 ATp -1.63.5.
• No new measurement has been published in 35
  years.

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Goals of this Proposal

• Measure the vertical target single-spin
  asymmetry on the neutron to 10-4 level.

Two order of magnitude improvement
First neutron measurement
Control systematic uncertainty to the 10-4 level.
Provide tight limits on target single spin
asymmetries.
DIS Parity Ay
Search for new chiral symmetry breaking
interactions.
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Big Bite Spectrometer
E03-004 plans to use the standard BigBite
electron detector package
Scintillator trigger plane Three wire
chambers Lead glass calorimeter
Better particle ID needed for SSA!
We purpose to add a new Cherenkov Detector
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Aerogel Cherenkov
An Aerogel (n1.03) Cherenkov detector can be
placed between wire chambers 2 and 3.
A tentative agreement has been reached with
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
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Trigger DAQ
Scintillator plane hit
Single arm trigger
Energy threshold in the calorimeter
Number of photons in the Cherenkov
Trigger rate of less then 5kHz Deadtime less then
5.
Aggressive in setting the calorimeter threshold
If necessary prescalling the trigger.
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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 data? 14 minute time window A
systematic bias of only 5?10-5
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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
  PTgt50.
• The target will be flipped every 1020 minutes.

Target densities will need to be monitored. Spin
Duality saw 8?10-4 differences
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Expected Results

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

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Kinematics Bite
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Results Compared to SLAC proton.
Two order of magnitude improvement!
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Systematic Uncertainties
This measurement will be dominated by systematic
uncertainty.

• Relative luminosity
• p background
• Quasi-elastic background

½ of the E03-004 data will be taken with beam in
the scattering plane
AT0
Clear measurement of our total systematic bias
Random quad run structure of target polarization
???? or ????
Better control of Systematic drifts
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Relative Luminosities
Luminosity enters directly as an asymmetry
systematic.
The Hall A Lumis are accurate to 5?10-5 in our
time scale.
After neutron dilution d(Aphys)sys 3.4 ?10-4
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Backgrounds Quasi-Elastic
For the highest x bin radaitive background is
less then 1.
For the lowest x bin quasi-elastic background of
10.

• The modified Regge GPD model predicts a
  quasi-elastic signal spin asymmetry Ay5?10-3,
  with a 30 uncertainty.
• The Ay experiment E05-015 will test this model
  giving us a better correction.

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Backgrounds Pions
The p/e ratio less then 101 for the two high x
bins less then 1001 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 p background will give us the Ap very
accurately.
Reverse BigBite Polarity
D Coincidence
Special Run
Change L-HRS momentum
Clean p signal
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Relation with other Experiments
Jefferson 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
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Beam Time Request

• Cherenkov Commissioning, Lumi Check Out, and PID
  Study.
• Density tests, position measurements, and
  linearity studies.

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Summary
We intend to measure the target single-spin
asymmetry ATn on the neutron. In a parasitic
experiment to E03-004.
Two order of magnitude improvement
We ask for one day of dedicated beam time
Checkout of the Lumis Checkout of the Aerogel
Detector Special systematic measurements 2 hour
delta run to get a clean p in PID
First neutron measurement
A large asymmetry would be a signal for
previously unseen chiral symmetry breaking beyond
the leading twist QCD picture of DIS
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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 ???? or ???? runs 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.

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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.