Strange-Quark Contributions to Parity-Violating Asymmetries in the Forward G0 Electron-Proton Scattering Experiment

Abstract

We have measured parity-violating asymmetries in elastic electron-proton scattering over the range of momentum transfers 0.12 < or =Q2 < or =1.0 GeV2. These asymmetries, arising from interference of the electromagnetic and neutral weak interactions, are sensitive to strange-quark contributions to the currents of the proton. The measurements were made at Jefferson Laboratory using a toroidal spectrometer to detect the recoiling protons from a liquid hydrogen target. The results indicate nonzero, Q2 dependent, strange-quark contributions and provide new information beyond that obtained in previous experiments.

On the strangeness -1 S-wave meson-baryon scattering

“…Apart from that, these interactions are interrelated with many other interesting areas, as listed in ref. [21], e.g., possible kaon condensation in neutron-proton stars [26,27,28,29], large yields of K − in heavy ions collisions [30,31], kaonic atoms [32] or non-zero strangeness content of the proton [33,34].…”

Parity violation in electron scattering

“…Four experimental programs in three laboratories, the Generation II PVES experiments, followed. The experiments were SAMPLE at the MIT Bates laboratory [16][17][18], the HAPPEX program at JLab [19][20][21], G0 at JLab [22,23], and the A4 program at Mainz [24][25][26]. By the time these programs were well underway, PVES had become accepted as a standard technique in electromagnetic facilities.…”

A Measurement of the Weak Charge of the Proton through Parity Violating Electron Scattering using the Qweak Apparatus: A 21% Result

“…The weak charge of the proton measurement is only possible because of the successful PVES physics programs conducted by SAMPLE [24], A4 [25,26], HAPPEX [27,28], and G0 collaborations [29] whose goal were to study the electroweak neutral currents of the nucleons in order to measure the strange quark contribution to nucleon structure. The success of the Q weak experiment will provide the technical expertise for the next generation of the PV physics program starting with the proposed 12 GeV Møller experiment [30] whose goal is to measure the weak mixing angle three times more precisely than the Q weak experiment.…”