paul e. reimer
DESCRIPTION
DIS-Parity: Measuring sin 2 θ W with Parity Violation in Deep Inelastic Scattering using Baseline Spectrometers at JLab 12 GeV. Paul E. Reimer. Charge. Standard Model parameters: Charge, e , a em g , G F m lifetime. Vector: g i V = t 3L (i) – 2q i sin 2 ( q W ) - PowerPoint PPT PresentationTRANSCRIPT
DIS-Parity: Measuring sin2θW with Parity Violation in Deep Inelastic Scattering using Baseline
Spectrometers at JLab 12 GeV
Paul E. Reimer
2
Unification of Weak and E&M Force•SU(2)—weak isospin—Triplet of gauge bosons•U(1)—weak hypercharge—Single gauge boson
Electroweak Lagrangian:
J, JYisospin and hypercharge currents
g, g0 couplings between currents and fields
Weinberg-Salam model and sin2(W)
Rem
embe
r—I’
m n
ot t
he e
xper
t he
re. Gary Larson, The Far Side
Vector: giV= t3L(i) – 2qi sin2(W)
Axial: giA = t3L(i)
Charge
Weak isospin
Standard Model parameters:• Charge, e , em
• g , GF lifetime• MZ
• sin2(W)
3
Running of sin2(W)
Measurements of sin2(W)
– APV Cs– Møller Scattering (SLAC E-158)– DIS (NuTeV)
Clear indication of running of sin2(W)
Future Experiments– Q-Weak (JLab)– Møller (JLab 12 GeV)
DIS-Parity at JLab 12 GeV
4
DIS Formalism on unpolarized Deuterium Target
Note that each of the Cia are sensitive to different possible S.M. extensions.
Longitudinally polarized electrons on unpolarized deuterium target—Cahn and Gilman, PRD 17 1313 (1978).
C1q ) NC vector coupling to q £ NC axial coupling to eC2q ) NC axial coupling to q £ NC vector coupling to e
Cia provide sensitivity to sin2(W)e e
5
Sensitivity to sin2(W)
Large asymmetryQ2 = 3.7 GeV2, Ad = 0.0003
“Easy experiment”Gain factor of 2 in sin2(W)
over Ad
Look for interference between large photon term and New Physics
APV ~
e e
e
?
e
+
e e
Z
6
How does DIS-Parity fit in?
e e
Zp
n
W
Z+
e e
ee
Z
Møller Scattering
• Purely Leptonic—no quark interactions
• K Kumar/D. Mack
e e
Z
Q-Weak (JLab)
• Coherent quarks in Proton• Results in ~2008• 2(2C1u+C1d)• S Page
e
Z
Cs133
Atomic Parity Violation
• Coherent quarks in entire nucleus• Nuclear structure uncertainties• -376 C1u – 422 C1d
• A. Derevianko and Other talks
DIS-ParityNeutrino Scattering
• Isoscaler quark scattering• (2C1u-C1d)+Y(2C2u-C2d)• X Zheng/P. Souder
• Quark scattering (from nucleus)• Weak charged and neutral
current difference• Tim Londergan
Expt. Probe different parts of Lagrangian
7
Jefferson Lab at 12 GeV Upgrade
Currently:• 6 GeV CW beam• 3 exp. Halls (A, B, C)• 80% polarized beam
Upgrade (Completion date?):• 12 GeV (11 GeV to Hall A, B, C)• Addition of Hall D• 85A to Hall A, C
Figures from JLab web site
8
Criteria for DIS-Parity with baseline equipment
General Experimental Criteria: DIS regime:
– Maximize Q2 (3.0-4.0 GeV2)– Large W2 ( > 4GeV2)
Minimize uncertainty from parton distributions:– Deuterium target
(d/u ratio vs nuclear effects)– x<0.7
Maximize sensitivity to sin2W
– Large Y
Expt. Assumptions: 60 cm liquid deuterium target 11 GeV beam @ 90mA 85% polarization § 0.5% Rates which can be handled:
– 1MHz DIS– /e ¼ 1 ) 1 MHz pions– 2 MHz Total rate
Implementation /e separation ) gas Cherenkov
counters ¼ 6 GeV thresh. Rate requires flash ADC’s or
Scaler-based DAQ on Cherenkov and Calorimeters—this is a counting experiment!!
9
Hall C at 11 GeV
HMS spectrometer• Pmax¼ 7.4 GeV/c §10%• = 8.1 msr
SHMS spectrometer:• Design in progress• Pmax ¼ 11 GeV § 10% • = 5.2 msr
Figures from Hall C CDR
HMS
SHMS
10
JLab Hall C SHMS/HMS combination
Large asymmetry (3£ 10-4) implies short runtime
13 “perfect” days E0 = 7 GeV
(scattered electron momentum) = 13o
Average Range
x 0.51 0.41-0.68
Y 0.44 0.35-0.50
Q2 3.9 GeV2 3.5-4.3 GeV2
W2 4.7 GeV2 2.9-6.0 GeV2
General experimental criteria are met.
Statistical Precision Two independent spectrometer
measurements Combined statistical precision
– A/A = 0.5%
– sin2W/sin2W = 0.26%
What about Hall A? Smaller solid angle and lower E0
Ready for 11 GeV yearsyears sooner!
What about systematics?
11
Uncertainties in Ad
Beam Polarization:
– Q-Weak also needs 1% polarization accuracy.
– Hall C Møller has achieved 0.5% polarization accuracy at low intensity
Determination of Q2 significant Higher Twist will be studied by
– PV-DIS at 6 GeV
– Res-Parity
Source Uncertainty
Source A sin2W
Statistical 0.5% 0.26%
Beam polarization 0.5% 0.26%
Deadtime 0.3% 0.15%
Q2 0.2%
R = (L/T) 0.01%
Parton Distributions
0.05%
Radiative corr. ??
Higher Twist PV-DIS@ 6GeV
Res-Parity
EMC/Nuclear Effects in 2H Parity Violation
Res-Parity
Total Uncertainty 0.8% 0.45%
12
Expected sin2(W) Results (JLab)
Ad/Ad = §0.50% (stat) §0.58% (syst) (§ 0.78% combined)
sin2(W)/sin2W= § 0.26% (stat) § 0.36% (sys) (§ 0.45% combined)
What about Ciq’s?
13
Extracted Signal—It’s all in the binning
Fit Asymmetry data as fn. of Y
A = A0 [ (2C1u – C1d) + Y(2C2u – C2d
)]
intercept = 2C1u – C1d (QWeak) slope = 2C2u – C2d
14
Exp. Constraints on C1u, C1d, C2u and C2d
Present experimental constraints are wide open, except for APV(1 standard deviation limits shown)
Combined result significantly constrains 2C2u–C2d. PDG 2C2u–C2d = –0.08 § 0.24 Combined (2C2u–C2d) = § 0.014
15
DIS-Parity: Conclusions
Measurements of sin2(W) below MZ provide strict tests of the Standard Model.
DIS-Parity provides complementary sensitivity to other measurements.
DIS-Parity Violation measurements can be carried out in at Jefferson Lab– Asymmetry is Large!
Jefferson Lab:
sin2(W) = 0.0011
(2C2u – C2d) = 0.014
Waiting for 12 GeV upgrade!