Professor Kent Paschke

I'm an Assistant Professor of Physics at University of Virginia, with an active research program at TJNAF in Newport News, Virginia.

My recent research activity has focused on the measurement of parity violation in electron scattering for the study of the structure of nucleons and nuclei and as a sensitive search for physics beyond the Standard model of electroweak physics. Presently, I am involved in four separate experiments which will run over the next 3 years in both Halls A and C at the Thomas Jefferson National Accelerator Facility (Jefferson Lab). I have assembled a laboratory at the University of Virginia to support these experiments, and in particular to continue research on the laser optics used in the Jefferson Lab polarized electron source.

Experimental Program

• I serve as co-spokesman for the HAPPEX-III experiment which seeks to further limit possible strange quark contributions to the charge and magnetic distributions of the proton. Recent measurements at Jefferson Lab have placed a tight constraint on the strange charge and magnetic distributions at very low momentum-transfer. HAPPEX-III will provide a high-precision test of the remaining suggestion that significant, non-zero contributions may still be visible at higher momentum transfer.


• The PREx experiment will measure the neutral-weak form-factor of the Lead-208 nucleus at very low momentum transfer, which is highly sensitive to the thickness of the neutron "skin". This neutron skin is expected in heavy, neutron-rich nuclei, but existing measurements of the skin thickness are clouded by uncertainties from the structure of hadronic probes. A measurement of parity violation in elastic electron-²⁰⁸Pb scattering will provide an independent measurement of this important physical feature of heavy nuclei. Furthermore, the skin thickness is closely related to the symmetry energy of neutron-rich, dense matter, which is a critical parameter for understanding the structure of neutron stars.


• The QWeak experiment will measure the parity-violating scattering asymmetry from the proton; any deviation from the Standard Model expectation for this asymmetry suggests contributions from new physics. This high-precision measurement is complementary to the recently published SLAC E-158 measurement of parity-violation in electron-electron scattering. The QWeak experiment will open exploration of Terascale physics at Jefferson Lab.


• The measurement of parity-violating scatting from deuterium in the Deep Inelastic Scattering regime (PV-DIS) provides a unique sensitivity to the weak axial-vector coupling of the quarks, but also samples the underlying nucleonic structure of the target. A rich program of study is being designed for JLab-12GeV to explore both important topics in hadronic structure (i.e. coherent quark-quark correlations and charge symmetry violation at high momentum fraction) and potential variations from Standard Model expectations for the weak axial charge of the quarks.


• Parity-violation in Moller scattering at JLab-12GeV holds the promise of a weak mixing angle measurement with precision directly comparable to colliders at the Z-pole, but in a kinematic regime sensitive to new physics through interference with the WNC amplitude. This translates to a senstivity to new phyics with axial-vector couplings to a scale of 25 TeV. World data on the weak mixing angle is presently dogged by a 3-sigma deviation between leptonic and semi-leptonic measurements, and a variation in the mean value across that range would have important consequences for global electroweak fits. The statistical impact from this measurement would have the power to convincingly resolve (or to make unambiguous) this possible inconsistency.

Researchers

• Graduate Student Researchers
  
  • Tharanga Jinasundera

• Undergraduate Student Researchers
  
  • Wes Regimbal
  • Tom Dudley
  • Daren Wang

• Postgraduate (non-thesis) Student Researchers
  
  • Mehrdad Adibzadeh
  • Ryan de Ridder

Selected Publications

Precision Measurements of the Nucleon Strange Form Factors at Q² ~ 0.1 GeV² , Physical Review Letters 98 , 032301 (2007).

Helicity Correlated Asymetries in a Polarized e- Beam, European Physics Journal A 32 (4) 549-553 (2007).

Constraints on the Nucleon Strange Form Factors at Q² ~ 0.2 GeV², Physic Letters B 635 , 275 (2006).

Parity-Violating Electron Scattering from ⁴He and the Strange Electric Form Factor of the Nucleon, Physical Review Letters 96 , 022003 (2006).

Precision Measurement of the Weak Mixing Angle in Moller Scattering, Physical Review Letters 95 , 081601 (2005).

Experimental Determination of the Complete Spin Structure for Anti-proton proton -> Anti-Lambda Lambda at beam momentum of 1.637 GeV/c, Physical Review C 74 015206 (2006).

Maintained by paschke@virginia.edu
Last Modified: Aug 20, 2007