A. Narayan

First Determination of the Weak Charge of the Proton

The Q(weak) experiment has measured the parity-violating asymmetry in ep elastic scattering at Q(2)=0.025(GeV/c)(2), employing 145 μA of 89% longitudinally polarized electrons on a 34.4 cm long liquid hydrogen target at Jefferson Lab. The results of the experiments commissioning run, constituting approximately 4% of the data collected in the experiment, are reported here. From these initial results, the measured asymmetry is A(ep)=-279±35 (stat) ± 31 (syst) ppb, which is the smallest and most precise asymmetry ever measured in ep scattering. The small Q(2) of this experiment has made possible the first determination of the weak charge of the proton Q(W)(p) by incorporating earlier parity-violating electron scattering (PVES) data at higher Q(2) to constrain hadronic corrections. The value of Q(W)(p) obtained in this way is Q(W)(p)(PVES)=0.064±0.012, which is in good agreement with the standard model prediction of Q(W)(p)(SM)=0.0710±0.0007. When this result is further combined with the Cs atomic parity violation (APV) measurement, significant constraints on the weak charges of the up and down quarks can also be extracted. That PVES+APV analysis reveals the neutrons weak charge to be Q(W)(n)(PVES+APV)=-0.975±0.010.

High resolution spectroscopic study of Be Λ10

Spectroscopy of a

A novel comparison of Møller and Compton electron-beam polarimeters

^{10}_{\Lambda}

Precision Electron-Beam Polarimetry using Compton Scattering at 1 GeV

Be hypernucleus was carried out at JLab Hall C using the

Precision measurement of the weak charge of the proton

(e,e^{\prime}K^{+})

Precision Electron-Beam Polarimetry at 1 GeV Using Diamond Microstrip Detectors

reaction. A new magnetic spectrometer system (SPL+HES+HKS), specifically designed for high resolution hypernuclear spectroscopy, was used to obtain an energy spectrum with a resolution of 0.78 MeV (FWHM). The well-calibrated spectrometer system of the present experiment using the

High resolution spectroscopic study of

p(e,e^{\prime}K^{+})\Lambda,\Sigma^{0}

^{10}_{\Lambda}

reactions allowed us to determine the energy levels, and the binding energy of the ground state peak (mixture of 1

Be

^{-}

Early Results from the Qweak Experiment

and 2