Transcript Document

Cultural Interlude
Final Results from
SLAC Experiment E158
“Measurement of the Electroweak Mixing Angle”
Emlyn Hughes
Caltech DOE HEP Review
July 21, 2004
TODAY...
LEP and SLC e+e- collider
Dsin2qw = 0.00017 (PDG2002) from Z pole measurements
Status in 1999
sin2qw
~5%
Q
(GeV)
Parity Violation in
Electron-Electron Scattering
e-
e-
g
Z
e-
eParity conserving
e-
e-
e-
eParity violating
SLAC Experiment E158
Detector
e
50 GeV
APV
Liquid
Hydrogen
=
e-escattering
s -s
s +s
Without electroweak radiative corrections,
APV
=
m E GF
2p 
In practice:
16 sin q2
(
2
2
(3 + cos q)
1
4
- sin2qw )
APV ~ 1.5 x 10-7
E158 Collaboration
•UC Berkeley
•Caltech
•Jefferson Lab
•Princeton
•Saclay
Sept 97:
1998-99:
2000:
2001:
2002:
2003:
•SLAC
•Smith College
•Syracuse
•UMass
•Virginia
EPAC approval
Design and Beam Tests
Funding and construction
Engineering run
Physics Runs 1 (Spring), 2 (Fall)
Physics Run 3 (Summer)
Spokespeople: K. Kumar, EWH, P. Souder
EndStation
Station
End
A A
Challenges
I.
Statistics
II. Beam monitoring & resolution

III.
Beam systematics

IV.
jitter vs. statistics
false asymmetries
Backgrounds
STATISTICS
# electrons per pulse
107
Rep rate (120 Hz)
109
Seconds/day
1014
100 days
1016
DA ~ 10-8
II. BEAM MONITORING
Beam Monitoring Correlations
senergy  1 MeV
sBPM  2 microns
BPM24 X (MeV)
storoid  30 ppm
Agreement (MeV)
Resolution
1.05 MeV
BPM12 X (MeV)
III. False Asymmetries
*
Halfwaveplate @ source
~few hours
*
48 vs. 45 GeV energy
~ few days
IV. BACKGROUNDS
*
electron-proton elastic scattering
*
pion production
*
radiative inelastic electron-proton scattering
W2 > 3 GeV2
*
2 photon events with transverse polarization
*
*
*
APV vs. time
ppb
Asymmetry Results
All E158 Data
At Q2 = 0.027 (GeV/c)2….
APV = -128  14 (stat)  12 (syst) ppb
sin2
MS
qw =
0.2330 ± 0.0011 (stat) ±0.0010 (syst)
Theory:
sin2
MS
qw =
0.2311 ± 0.00016
Status in 1999
sin2qw
Q
(GeV)
sin2qw
0.240
0.238
Cesium Atomic Parity Violation Result vs. Time
(Colorado measurement)
Standard Model
0.236
0.234
0.232
0.230
Wieman et al.
1997
1998
Bennett
Wieman
1999
Derevianko
Kozlov
Porsev
Tupitsyn
Dzuba
Flambaum
2000
2001
Kuchiev
Flambaum
Johnson
Bednyhakov
Soff
2002
Modifications in the theoretical corrections to the
atomic structure
2003
Status Today
sin2qw
7s
Beyond Standard Model Implications...
(95% confidence level)
*
Limit on LLL ~ 10 TeV
*
Limit on SO(10) Z’ ~ 900 GeV
*
Limit on lepton flavor
violating coupling ~ 0.01GF
SUMMARY
*
Performed a first measurement
of parity violation in e-e- scattering
Final published results in ~ 1/2 year
*
*
Future parity experiments active
Complementary to collider experiments