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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 )

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Paul E. Reimer


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DIS-Parity: Measuring sin2θW with Parity Violation in Deep Inelastic Scattering using Baseline Spectrometers at JLab 12 GeV

Paul E. Reimer

weinberg salam model and sin 2 q w

Charge

  • Standard Model parameters:
  • Charge, e ,aem
  • g , GF m lifetime

Vector: giV= t3L(i) – 2qi sin2(qW)

Axial: giA = t3L(i)

  • MZ
  • sin2(qW)

Weak isospin

Weinberg-Salam model and sin2(qW)
  • Unification of Weak and E&M Force
  • SU(2)—weak isospin—Triplet of gauge bosons
  • U(1)—weak hypercharge—Single gauge boson
  • Electroweak Lagrangian:
  • Jm, JmYisospin and hypercharge currents
  • g, g0 couplings between currents and fields

Gary Larson, The Far Side

Remember—I’m not the expert here.

running of sin 2 w
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
dis formalism on unpolarized deuterium target

e

e

DIS Formalism on unpolarized Deuterium Target

Longitudinally polarized electrons on unpolarized deuterium target—Cahn and Gilman, PRD 17 1313 (1978).

C1q) NC vector coupling to q

£ NC axial coupling to e

C2q) NC axial coupling to q

£ NC vector coupling to e

Cia provide sensitivity to sin2(qW)

Note that each of the Cia are sensitive to different possible S.M. extensions.

sensitivity to sin 2 q w

Gain factor of 2 in dsin2(qW)

over dAd

Large asymmetry

Q2 = 3.7 GeV2, Ad = 0.0003

“Easy experiment”

e

e

e

e

e

e

+

?

g

Z

APV ~

Sensitivity to sin2(qW)

Look for interference between large photon term and New Physics

how does dis parity fit in

Q-Weak (JLab)

Møller Scattering

Atomic Parity Violation

e

g

e

e

e

e

e

e

Z

Z

g

g

Cs133

Z

g

e

p

e

  • Coherent quarks in Proton
  • Results in ~2008
  • 2(2C1u+C1d)
  • S Page

Z

  • Purely Leptonic—no quark interactions
  • K Kumar/D. Mack

n

  • Coherent quarks in entire nucleus
  • Nuclear structure uncertainties
  • -376 C1u – 422 C1d
  • A. Derevianko and Other talks

n

n

n

m

Z

W

+

How does DIS-Parity fit in?

Neutrino Scattering

DIS-Parity

Expt. Probe different parts of Lagrangian

  • Quark scattering (from nucleus)
  • Weak charged and neutral current difference
  • Tim Londergan
  • Isoscaler quark scattering
  • (2C1u-C1d)+Y(2C2u-C2d)
  • X Zheng/P. Souder
jefferson lab at 12 gev upgrade
Jefferson Lab at 12 GeV Upgrade
  • Upgrade (Completion date?):
  • 12 GeV (11 GeV to Hall A, B, C)
  • Addition of Hall D
  • 85mA to Hall A, C
  • Currently:
  • 6 GeV CW beam
  • 3 exp. Halls (A, B, C)
  • 80% polarized beam

Figures from JLab web site

criteria for dis parity with baseline equipment
Criteria for DIS-Parity with baseline equipment

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

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 sin2W
    • Large Y

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!!
hall c at 11 gev
Hall C at 11 GeV
  • HMS spectrometer
  • Pmax¼ 7.4 GeV/c §10%
  • W = 8.1 msr
  • SHMS spectrometer:
  • Design in progress
  • Pmax¼ 11 GeV § 10%
  •  = 5.2 msr

SHMS

HMS

Figures from Hall C CDR

jlab hall c shms hms combination
JLab Hall C SHMS/HMS combination

Statistical Precision

  • Two independent spectrometer measurements
  • Combined statistical precision
    • A/A = 0.5%
    • sin2W/sin2W = 0.26%

What about Hall A?

  • Smaller solid angle and lower E0
  • Ready for 11 GeV years sooner!

What about systematics?

  • Large asymmetry (3£ 10-4) implies short runtime
  • 13 “perfect” days
  • E0 = 7 GeV

(scattered electron momentum)

  •  = 13o

General experimental criteria are met.

uncertainties in a d
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
expected sin 2 q w results jlab
Expected sin2(qW) Results (JLab)

dAd/Ad = §0.50% (stat)

§0.58% (syst)

(§ 0.78% combined)

dsin2(qW)/sin2W= § 0.26% (stat)

§ 0.36% (sys)

(§ 0.45% combined)

What about Ciq’s?

extracted signal it s all in the binning
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

exp constraints on c 1u c 1d c 2u and c 2d
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 § 0.24Combined d(2C2u–C2d) = § 0.014

dis parity conclusions
DIS-Parity: Conclusions
  • Measurements of sin2(qW) 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:

d sin2(qW) = 0.0011

d(2C2u – C2d) = 0.014

Waiting for 12 GeV upgrade!