Wai Kin "Sam" Lai


Allen 411 Desk #1
(412) 648-8345
Graduate Student , Graduate Student Mentor 2010


Applications of effective theories of QCD in collider physics.

In this thesis, we apply eective theories of Quantum Chromodynamics (QCD) in collider physics.
First, we apply heavy quark eective theory (HQET) on the production asymmetries of heavy hadrons in collider experiments. Asymmetries of the partial widths of a heavy hadron and its anti-particle contain information about CP-violation. In collider experiments, Partial widths are inevitably entangled with production rates. Therefore, understanding production asymmetries is essential in extracting information about CP-violation from collider experi-
ments. At leading twist in perturbative QCD, such production asymmetries are absent. Using heavy quark eective theory (HQET), we examine the subleading-twist processes which can produce the productions asymmetries. By tting several non-perturbative parameters
to data, the production asymmetries of D+/D- measured at LHCb can be explained reasonably well. We also make predictions on production asymmetries of Q=Q at the LHC.  The asymmetries are found to be signicant in the forward region and should be measurable by LHCb. In addition, for further investigation in the future, we compute the partonic cross sections for P waves.

Second, we apply soft-collinear eective theory (SCET) to resum large logarithms ln(1m2H/s) in the threshold region m2H → s for the associated production of the Higgs boson with a vector boson at the LHC. The effect of NNNLL resummation on the total cross section at NNLO is found to be negligible. For the distribution in   =M2vH/s, the NNLL resummation increases the xed-order NLO result by ~ 10% at ~ 0:1, suggesting the
importance of threshold resummation at of moderate size.



Graduate Advisor

Adam K Leibovich