[Triumf-seminars] TRIUMF Colloquium today at 14:00

[TRIUMF Seminars]

Date/Time: Thu 2012-08-02 at 14:00

Location:  Auditorium          

Speaker:   Roger Carlini (Thomas Jefferson National Accelerator Facility)

Title:     A Search for New Physics via the Proton Weak- Charge Measurement

Abstract: The Qweak Collaboration consisting of US and Canadian researchers has recently completed at Jefferson Lab the first direct measurement of the proton's weak charge, QpW, to a precision of approximately 4% by measuring the parity-violating asymmetry in elastic polarized-electron-proton scattering. The measurement is now in the analysis phase. This asymmetry is small (of scale 250 ppb) and is proportional to the proton's weak charge. At tree level, the weak mixing angle is related to the weak charge of the proton by QpW=1-4sin2 ThetaW, leading to a ~0.3% measurement of sin2 ThetaW at low energy - making this the best low energy measurement to date. The Standard Model makes a firm prediction of the proton's weak charge, based on the running of the weak mixing angle from the Z0 pole down to low energies, corresponding to a 10 sigma effect in our experiment. This measurement will test that prediction and thus be sensitive to new parity violating physics at the several TeV scale. The required hadronic corrections have now been determined from a combination of recently completed strange quark search parity violation measurements, DIS measurements and theoretical calculations. The status, methodology, systematic uncertainties and interpretation of the measurement will be discussed. In addition, a brief summary of ancillary physics measurements will be presented.

Stimulants available 15 minutes before the talk.

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