Junegone Chay

Collinear effective theory at subleading order and its application to heavy - light currents

We consider a collinear effective theory of highly energetic quarks with energy E, interacting with collinear and soft gluons by integrating out collinear degrees of freedom to subleading order. The collinear effective theory offers a systematic expansion in power series of a small parameter lambda ~ p_{\perp}/E, where p_{\perp} is the transverse momentum of a collinear particle. We construct the effective Lagrangian to first order in

Factorization of B decays into two light mesons in soft collinear effective theory

\lambda

Soft Wilson lines in the soft-collinear effective theory

, and discuss its features including additional symmetries such as collinear gauge invariance and reparameterization invariance. Heavy-light currents can be matched from the full theory onto the operators in the collinear effective theory at one loop and to order lambda. We obtain heavy-light current operators in the effective theory, calculate their Wilson coefficients at this order, and the renormalization group equations for the Wilson coefficients are solved. As an application, we calculate the form factors for decays of B mesons to light energetic mesons to order lambda and at leading-logarithmic order in alpha_s.

Bounds of the mass of [formula presented] and the neutral mixing angles in general [formula presented] models

We show that the amplitudes for B decays into two light mesons at leading order in soft-collinear effective theory are factorized to all orders in alpha_s. We construct gauge-invariant four-quark operators by employing the effective theories SCET_I for sqrt{m_b \Lambda} <\mu<m_b, and SCET_II for \mu <sqrt{m_b \Lambda} with Lambda ~0.5 GeV. These operators do not allow gluon exchanges between different sectors of the current and the matrix elements are reduced to the products of current matrix elements. The spectator interactions are also factorized at leading order in SCET and to all orders in alpha_s.

Factorization of the dijet cross section in electron-positron annihilation with jet algorithms

The effects of the soft gluon emission in hard scattering processes at the phase boundary are resummed in the soft-collinear effective theory (SCET). In SCET, the soft gluon emission is decoupled from the energetic collinear part, and is obtained by the vacuum expectation value of the soft Wilson-line operator. The form of the soft Wilson lines is universal in deep inelastic scattering, in the Drell-Yan process, in the jet production from e{sup +}e{sup -} collisions, and in the {gamma}*{gamma}*{yields}{pi}{sup 0} process, but its analytic structure is slightly different in each process. The anomalous dimensions of the soft Wilson-line operators for these processes are computed along the lightlike path at leading order in SCET and to first order in {alpha}{sub s}, and the renormalization group behavior of the soft Wilson lines is discussed.

Structure of divergences in the Drell-Yan process with small transverse momentum

We consider phenomenological constraints on the mass MZ′ and the two mixing angles θR and ξ of the neutral sector in a very general class of SU(2)L×SU(2)R×U(1) models using electroweak data. We do not make any specific assumptions such as left-right symmetry or the Higgs structure. The analysis of the neutral sector has the advantage that it has relatively fewer parameters compared to the charged sector since the Cabibbo-Kobayashi-Maskawa (CKM) matrix elements in the right-handed sector do not enter into the analysis, hence the number of various possibilities from a big parameter space is reduced. We utilize theoretical considerations on the masses of the gauge particles and the mixing angles. We combine the precision electroweak data from LEP I and the low-energy neutral-current experimental data to constrain the parameters introduced in the model. It turns out that MZ′ > 400 GeV, −0.0028 < ξ < 0.0065 with little constraint on θR. In the left-right symmetric theory, MZ′ should be larger than 900 GeV. With these constraints, we compare the values for σ(ee → μμ), σ(ee → bb) and AFB at LEP II with experimental values.

Quark mass effects in the soft-collinear effective theory and B{yields}X{sub s}{gamma} in the end point region

We analyze the effects of jet algorithms on each factorized part of the dijet cross sections in

Azimuthal asymmetry in lepton-proton scattering at high energies

e^+ e^-

Factorization theorem for high-energy scattering near the end point.

scattering using the soft-collinear effective theory. The jet function and the soft function with a cone-type jet algorithm and the Sterman-Weinberg jet algorithm are computed to next-to-leading order in

Azimuthal correlation in lepton-hadron scattering via charged weak-current processes

\alpha_s