Searches for Physics beyond the Standard Model

Conference · Sun May 01 00:00:00 EDT 2011 · J.Phys.Conf.Ser.

DOI:https://doi.org/10.1088/1742-6596/295/1/012028· OSTI ID:1023904

H van Oers, Willem T

The Thomas Jefferson National Accelerator Laboratory has the demonstrated ability to test the fundamental symmetries of nature to very great precision and thereby probe for new physics beyond the Standard Model (SM). In the following objectives and descriptions will be given of three Jefferson Laboratory (JLab) experiments: Qweak, MOLLER, and PVDIS. The Qweak experiment is to measure the weak charge of the proton (via the vector coupling of the Z0 boson to the proton). The MOLLER experiment is to measure the weak charge of the electron. The PV-DIS experiment will measure combinations of vector couplings and axial-vector couplings to the quarks of the nucleons. These three experiments follow from the advances made in precision parity-violating electron scattering measurements at the CEBAF of JLab. The Standard Model makes accurate predictions of the 'running' of the electroweak mixing angle or sin2(θw) from the Z0 pole down to low energies and therefore of the weak charges of the proton and electron. The Qweak experiment will make the first precision determination of the weak charge of the proton, Qpw = 1 – 4 sin2 (θw), from a measurement of the parity-violating asymmetry in the elastic scattering of longitudinally polarized electrons from the protons in a liquid hydrogen target at very low momentum transfer. The projected result will determine the proton's weak charge with a 4.1% total error and consequently sin2 (θw) with a 0.3% error. The Qweak experiment is at present three months into its commissioning run. The MOLLER experiment is to measure the parity-violating asymmetry in the scattering of 11 GeV longitudinally polarized electrons from the atomic electrons in a liquid hydrogen target. The longitudinal analyzing power Az is predicted to be 35.6 ppb at the kinematics of the experiment and is to be determined with a precision of 0.73 ppb, which would make the MOLLER experiment the most precise parity-violation experiment ever undertaken. The result would yield a measurement of the weak charge of the electron to 2.3% at an average Q2 value of 0.0056 (GeV/c)2 and in turn a determination of the electroweak mixing angle sin2(θw) with an uncertainty of ±0.00026 (stat) ±0.00013 (syst), comparable to the accuracy of the two best determinations at the Z0 pole. The PVDIS experiment is to measure the parity-violating asymmetry in deep inelastic scattering of longitudinally polarized electrons from an unpolarized deuterium target. The longitudinal analyzing power can be expressed in terms of the quark distribution functions of the deuterium target and the couplings C1q (axial electron x vector quark) and C2q (vector electron x axial quark), which in the Standard Model can be expressed in terms of sin2(θw).

• Research Organization: Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
• Sponsoring Organization: USDOE Office of Science (SC)
• DOE Contract Number: AC05-06OR23177
• OSTI ID: 1023904
• Report Number(s): JLAB-PHY-11-1411; DOE/OR/23177-1805; TRN: US1104618
• Journal Information: J.Phys.Conf.Ser., Vol. 295, Issue 01; Conference: 19th International Spin Physics Symposium (SPIN 2010), Julich, Germany, Sep 27- Oct 2, 2010
• Country of Publication: United States
• Language: English

Related Subjects

43 PARTICLE ACCELERATORS
08 HYDROGEN
ASYMMETRY
BOSONS
CEBAF ACCELERATOR
DEEP INELASTIC SCATTERING
DEUTERIUM TARGET
ELASTIC SCATTERING
ELECTRONS
FERMILAB ACCELERATOR
HYDROGEN
MOMENTUM TRANSFER
NUCLEONS
PHYSICS
POLARIZATION-ASYMMETRY RATIO
PROBES
PROTONS
QUARKS
SCATTERING
SPIN
STANDARD MODEL
TARGETS
WEINBERG ANGLE