1.  contribution of s-quarks to 4He nucleus
E01-003: E Update Parity Violation in 4He(e,e’) at Q2 = 0.6 (GeV/c)2
E. Beise PAC19
Hall A collaboration experiment
approved in 1992 for 85 days of beam, “A” rating
 contribution of s-quarks to 4He nucleus
Physics overview and update
Comparison w/ other experiments
Experiment update/status
target
DAQ
test data
Updated Beam request:
65 days at I=100 mA, Pe =0.80

2. E91-004 History Conditionally approved by PAC 5 (Jan 92)
Endorsed as Hall A collab. Experiment (June 92)
Reviewed by “Parity Technical Committee” (July 92)
(chair: B. Barish)
“The proponents have made a convincing argument that the systematic effects… are under control.”
“The real running conditions at forward angles must be investigated.”
“The main challenge is attaining the required statistical precision. It would not make sense to attempt this experiment if the conditions are significantly less than those proposed.”
“The critical piece of apparatus is the high density helium target…”
Full approval by PAC 7 (85 days): “A” rating (Dec 93)
Technical Requirements
spectrometers commissioned  Pmax = 3.2 GeV/c
high current pol’d beam (1998)
high power 4He target (2000)
 to be upgraded 2001/2002
Expected performance of pol’d beam  reduction in required beam hours for same measurement.
Ready to request scheduling if reapproved by PAC19

3. Measurement of Strange Quark Effects Using Parity Violating
Update to JLAB Experiment E
Measurement of Strange Quark Effects Using Parity Violating
Elastic Electron Scattering from 4He at Q2 = 0.6 (GeV/c)2
E.J. Beise, H. Breuer, C.C. Chang, N. Chant, J.J. Kelly, P. King, and P.G. Roos
University of Maryland, College Park MD 20742
B. Filippone, J. Gao, K. Gustafsson, T. Ito, J. Martin, and R.D. McKeown
W.K. Kellogg Radiation Laboratory, Caltech, Pasadena, CA 91125
J.P. Chen, O. Hansen, K. deJager, J. Gomez, J.H. Mitchell,
J.J. LeRose, N. Liyanage, R. Michaels, S. Nanda, A. Saha, and B. Wojtsekhowski
Thomas Jefferson National Accelerator Facility, Newport News, VA 23606
G.G. Petratos, M. Katramatou, and K. McCormick
Kent State University, Kent, OH 44242
D.S. Armstrong, T. Averett, J.M. Finn, and J. Roche
College of William and Mary, Williamsburg, VA 23187
W. Korsch and D. Dale
University of Kentucky, Lexington, KY 40506
K. Aniol, M. Epstein, and D. Margaziotis
California State University at Los Angeles, Los Angeles, CA 90032
M. Pitt
Virginia Polytechnic Institute, Blacksburg, VA 24061
J.A. Templon
The University of Georgia, Athens, GA 30602
J. Calarco
The University of New Hampshire, Durham, NH 03824
P. Markowitz
Florida International University, Miami, FL 33199
X. Jiang
Rutgers University, New Brunswick, NJ 08854
P. Ulmer
Old Dominion University, Norfolk, VA 23529
R. Wilson
Harvard University, Cambridge, MA 02138
A Hall A Collaboration Experiment

4. Parity Violating Electron Scattering
polarized electrons
unpolarized target
for a proton:
forward angles
backward angles
electroweak radiative corrections
Z exchange
anapole

5. Proton experiments and strange form factors
SAMPLE: Q2 = 0.1
HAPPEX:
rules out pure
pole-type models
now limited by
neutron EM form factors
Mainz PVA4 (in progress) :
HAPPEX II: Q2 = 0.1
G0: complete separation of GMs, GEs, and GAe
0.12  Q2  1.0
total program ( 40 days each):
1 forward angle
3 backward angle H2
3 backward angle D2 quasielastic

6. Heavy Baryon Chiral PT
constrained
by SAMPLE 97
constrained by
HAPPEX 98
at Q2 = 0.5 (GeV/c)2

7. 4He: PV in a J=0,T=0 System dGsE   0.06  0.02
M.J. Musolf, et al., Phys. Rep. 239 (1994) 1.
G(q)  isospin breaking contribution < 1%
Ramavataram, Hadjimichael + Donnelly, PRC50 (1994) 1175.
RV  vector weak radiative corrections  1%
M.J.M., et al., PR 239
Fs  nuclear strangeness form factor
nuclear structure largely cancels in APV
in “1-body” limit:
E00-114: Q2 = 0.1 (GeV/c)2 GsE(t)  rst drs   0.5
theory:
this exp (E91-004): 0.6 (GeV/c)2
dFs   3.5  10-3
dGsE   0.06  0.02
Contribution from meson exchange
Musolf, Schiavilla+Donnelly, PRC 50 (94) 2173

8. E91-004: 4He(e,e’) elastic scattering
sensitive only to GEs
potential probe of non-nucleonic strangeness
at Q2 = 0.6 (GeV/c)2
w/ 60 days production beam (100 mA, 80% pol’n)
dAexp = 17 ppm
dFs   3.5  10-3
dGsE (stat)   0.06

9. Meson Exchange and Nuclear Strangeness
1-p exchange violates G-parity
dominant 2-body contributions from pair + transition currents
low Q2: Musolf+ Donnelly, PLB 318 (1993) 263
Q2 > 0.5 : Musolf,Schiavilla+Donnelly, PRC 50 (1994) 2173
could contribute as much as 15% to APV
first term depends on value of ms
sign of grps uncertain
grps(Q2) unknown
Goity+Musolf, PRC 53 (1996) 399
Ito+Ramsey-Musolf, PRC 58 (1998) 2595

10. Musolf, Schiavilla + Donnelly, PRC 50 (1994) 2173
assumes
rs = -2.0
ms = -0.20
grps = +0.26
location of minimum
in Fs largely determined by
non-strange MEC
contributions
If assume 100% uncertainty
in grps contribution, then
(dGsE)MEC   0.02
(dGsE)EXP   0.06

11. Experimental Requirements
Q2 = 0.6 (GeV/c)2
Ebeam = 3.3 GeV
q = 13.5°
HRS2 in single-arm
d/d = 1 nb/sr
elastic rate = 780 Hz
(per arm)
tracking preferable
add small trigger scintillator to minimize QE rate
use two separate DAQ systems to minimize dead time
DW = 6.5 msr per arm w/ no spectrometer collimators
from G.G. Petratos

12. Helium Target (Cal State LA group)
Cell in house (7075-T6 Al, 13 mil walls)
pressure tested to 30 atm
operate at 5.8 K, 15 atm
will also be used for E00-114, E00-118
To Be Done:
target manifold
collimators for windows
upgrade loop for higher power
Existing (10 cm “tuna can”) cell has been tested to 100 mA:
E scaler data 6%
drop

13. Data Acquisition Test setup July 2000: (R. Michaels)
(run 2 independent DAQs for each spectrometer)
20% dead at 2.5 kHz per spect.
Rate dependence well understood
use addt’l trigger scintillator to minimize rate from QE events

14. Tracking tracking desired for background reduction
total triggered rate into VDCs < 10 kHz
from study of high rate (70  300 kHz) data (E94-004), rate dependence would result in negligible false asymmetry (but overall tracking efficiency was low…)
want tracking efficiency  90% to minimize loss of statistics
E data: y vs. x at focal plane
added trigger scint
target walls not subtracted

15. 4He(e,e’) data from 97-111 Oct 2000 10 cm “tuna can” cell
no collimation of target windows
E kinematics
S1-S2 trigger, no particle ID
all data
empty subtracted
cut on S1
diagonal
cut

16. Beam Properties and Systematic Errors
Flip helicity at 30 Hz: dAmeas in 30 msec = 18%
HAPPEX achieved results far better than required for E91-004
Run HAPPEX DAQ simultaneously to feedback on intensity
potential issue: how to synch different DAQ systems
will be tested during pol’d 3He run summer 2001
(overall dAmeas (pol’d 3He)  100 ppm at some kinematics…)
Parameter
measurement
req’d in 30 msec
HAPPEX
Energy
dE/E
110-3
10-6
Position dx
0.5 mm
20 mm
Angle dq
0.3 mrad
30 mrad
Intensity
dI/I
0.5 %
30 ppm