[Jlabsa_gs] **Today** Pizza Seminar - Wednesday, June 19, 2013 - A message from Hari Areti

Jodi Patient patient at jlab.org
Wed Jun 19 08:31:16 EDT 2013


Thank you to all of those who RSVP'd.  See you at noon today.


Jefferson Lab's Graduate Student and Post-Doc Association Wiki:
  https://gspda.jlab.org/wiki/index.php/Main_Page

   Please RSVP to:  patient at jlab.org by COB on June 17, 2013

                    Wednesday, June 19, 2013

                          ***F113***

                        12:00-1:00 pm


"The Q_weak Experiment: A Search for New Physics at the TeV Scale
         via a Measurement of the Proton's Weak Charge"



                     Rakitha Beminiwattha

               Syracuse University, Syracuse, NY
                    


Abstract:  After a decade of preparations, the Qweak experiment at Jefferson
Lab is making the first direct measurement of the weak charge of the proton,
Q^p_W. Because this quantity is suppressed in the Standard Model, a 4% result
will significantly constrain new physics at the TeV scale while providing the
most precise measurement of sin^2theta_W at low energies.  Operationally, we
measure the small (about -0.200 ppm) parity-violating asymmetry in electron-
proton scattering in integrating mode while flipping the longitudinal polarization
of the electrons up to 1000 times per second. Potential sources of new, parity
violating interactions between electrons and light quarks include a Z', lepto-quarks,
and R-parity violating SUSY.

Commissioning took place in Fall 2010, and we finished taking data in early summer 2012.
Result presented is based on the data taken during an initial two weeks period which
included a 16% measurement of the parity violating electron-proton scattering asymmetry,
A = -0.2788 +/- 0.0348 (stat.) +/- 0.0290 (syst.) ppm at Q^2 = 0.0250 +/- 0.0006 (GeV)^2.
>From this result a 21% measurement of the weak charge of the proton and constraints on
isoscalar/isovector effective coupling constants of the weak neutral hadronic currents
are extracted. The latter are nearly orthogonal to, and thus completely complementary
to atomic parity violation data, e.g. Cs. The result is a proof of principle for the
analysis of the full Qweak data to be completed in the near future.


 


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