SANE HMS Report
Status of Elastic and Inclusive Asymmetries
Hall C Summer Workshop, 2009
For the SANE Collaboration,
Narbe Kalantarians
University of Virginia
Outline
SANE Experiment
Physics
HMS Coverage
Analysis Status
Summary
See Previous Talk by Hovhaness
SANE-HMS Inclusive
2
2
• Complementary to RSS(<Q >=1.3GeV , 0.3<xBj<0.8, 0.8<W<1.8GeV).
Extended coverage in lower xBj (~0.2) for DIS. Fit A1 and A2 for
resonances, at higher Q².
• Reduce error in moments of g1 and g2.
• HMS information necessary for packing fraction.
SANE-HMS Inclusive (Asymmetries)
(measured) Am = Apar, Aperp = Araw / (f(pf)PbPt)
Araw =(N+ - N-)/(N+ + N-)
Pb, Pt Beam and Target polarization, respectively
f dilution factor from N, He, ...
pf packing fraction (amount of target material).
SANE-HMS Elastic
• Perpendicular e-p coincidence data
sensitive to form factor ratio (GEp/GMp)
• Electron detected in BETA, proton in HMS.
2
2
• Took data at 2 Q : 5.2GeV (Ebeam=4.7GeV)
& 6.2GeV2 (Ebeam=5.9GeV).
• Coincidence e-p elastic asymmetry
Ael = Am / ( PbPt f).
• For coincidences f~1.
SANE HMS Data Summary
Color-coded data useful for A1 & A2
Data with Wmin = elastic for Ael
SANE HMS Incl. Kinematic Coverage
Elastic Asymmetries
• Approximately 1800+ good events.
• Work to be done on tracking. There were some issues with HMS drift chambers.
• Very preliminary result, assuming <Pb>=<Pt>~0.7: error ~ 0.051*.
• Difference in predicted result between polarized transfer and Rosenbluth for
Gep/GMp ~ 0.13*
• Errors for data expected to be small enough to allow for distinguishing between
Gep/GMp models*.
• A. Liyanage (Hampton, +HMS calibrations)
* P. Bosted www.jlab.org/~bosted/EPANAL.pdf
Inclusive Asymmetries
Approximately ~105 good events.
Comparison to models underway.
Aperp in progress.
Apar
H. Kang (Seoul National, +BETA
calibrations)

Very Preliminary
W
Apar 4.7GeV E'HMS=3.2GeV, HMS=200, Q2= 1.8GeV2
SANE-HMS, CLAS-eg1b
(Minor fraction of data shown)
Inclusive
12
C(e,e')X
●
Take ratio of data to Monte Carlo to get agreement (flat ratio), using 4.7GeV parallel data.
●
Check on 12C model and understanding HMS acceptance, detector efficiencies, and Ibeam calibration.
●
Need to resolve acceptance from MC side (be sure of cross-section models).
●
Will be useful for determining pf.
data/MC
Packing Fraction (pf)
●
Qualitative: Actual amount of target material used. Ratio of data to MC as function of W.
●
Determined by linear relation YT=mpf+b, YT(yield)~ 1.
●
Will need a pf for each of the NH3 loads used during data taking.
●
Expecting pf ~ 0.55 +/- 0.02.
Liquid 4He
NH3 beads
Target Wall
HMS Calibrations

E/p
Slow Raster calibration in progress
(L. Ndukum, MSU).
npe
HMS Data Summary
• (HMS) Calibrations almost complete.
• Taken 1st step towards Packing fractions, crucial for f. Still have
some work remaining on this.
• Working on resolving acceptances.
• Looking to obtain physics asymmetries soon.
Support Slides
Inclusive Asymmetries
Aperp as function of run number.
Packing Fraction
Using 4.7GeV Parallel Carbon data.
Taking ratio of Data to Monte Carlo.
Expecting approximately 0.55-0.57.
Packing Fraction
DC Calibrations
Assume particles are equally distributed
in both sides of the wire and so there
should be equal numbers of events
particular to each distance from the wire.
At DC1, at 0, it gives us a little peak. At
shorter drift distances,we have higher
number of events implying there are some
drift time offsets.
After setting scintillator and DC TDC
window,determine the DC time offsets and
correct it.
Calorimeter Calibrations
hsshtrk is the total energy sum
for each event
hse is the momentum of that
particle.
After calibration, the peak
should be around 1.
ToF Calibrations
Peak for hbeta plot should be at 1 for
electron.
hbeta notrk plot based on the all hits on
scintillators w/o corrections or selection
criteria.
hbeta uses tracking selection criteria
that involves checking for hits on each
scintillator padels for each track.
Cerenkov Calibrations
ADC plots for top and bottom
mirrors separately and convert to
number of photo- electrons.
The first clear peak at the ADC
plots belong to the 1 photoelectron (exclude 0).
Divide all ADC values by the
ADC value pertaining to 1 photoelectron.
We use 1/ADC for 1 photoelectron in our PARAM files.