Undergraduate Research at Jefferson Lab

Spin-Polarization of Helium-3 Target Cell

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Pretzelosity Distribution

Formulism for R, the Longitudinal to Transverse
Momenta Ratio, Within the Quark Parton Model

Student: Daniel Koch

School: San Jose State University

Mentored By: Wally Melnitchouk

When nucleons are struck by a beam of electrons, the scattering process is a combination of the beam's energy as well as the primordial motion of the quarks within the nucleon. Until recently, it has been assumed that at high Q2, the transverse moment kT of the parton was negligible. However, new experiments at low Q2 suggest that kT dependence may indeed play a significant role. The exact kT dependence based on theoretical grounds is still unknown, and is the major objective of this project. We examined previously laid theoretical groundwork for R (R = σL/σT) and improved them. In particular, we updated several of their formulas using modern techniques and distribution functions. If our theoretical models match well with the data, it will prove that kT dependence can no longer be ignored. At low Q2, this primordial transverse momentum will need to be more accurately studied.
Formulism for R, the Longitudinal to Transverse<br>Momenta Ratio, Within the Quark Parton Model