최준곤 교수

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 $\ensuremath{\lambda}\ensuremath{\sim}{p}_{\ensuremath{\perp}}/E,$ where ${p}_{\ensuremath{\perp}}$ is the transverse momentum of a collinear particle. We construct the effective Lagrangian to first order in

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 ${e}^{+}{e}^{\ensuremath{-}}$ collisions, and in the ${\e

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 ${\ensuremath{\alpha}}_{s}.$ We construct gauge-invariant four-quark operators by employing the effective theories ${\mathrm{SCET}}_{\mathrm{I}}$ for $\sqrt{{m}_{b}\ensuremath{\Lambda}}<\ensuremath{\mu}<{m}_{b},$ and ${\mathrm{SCET}}_{\mathrm{II}}$ for $\ensuremath{\mu}<\sqrt{{m}_{b}\ensuremath{\Lambda}}$ with $\ensuremath{\Lambda}\ensuremath

We consider rare radiative B decays such as $\overline{B}\ensuremath{\rightarrow}{K}^{*}\ensuremath{\gamma}$ or $\overline{B}\ensuremath{\rightarrow}\ensuremath{\rho}\ensuremath{\gamma}$ in soft-collinear effective theory (SCET) and show that the decay amplitudes are factorized to all orders in ${\ensuremath{\alpha}}_{s}$ and at leading order in ${\ensuremath{\Lambda}}_{\mathrm{QCD}}{/m}_{b}.$ By employing two-step matching, we classify the operators for radiative B decays in powers of a small p

We consider the azimuthal angular dependence of the distribution of final-state hadrons in high-energy lepton-proton scattering. The distribution displays an azimuthal asymmetry due to both perturbative and nonperturbative effects. At the large momentum transfers attainable, for example, at the DESY $\mathrm{ep}$ collider HERA we expect the perturbative effects to dominate and constitute a clear test of QCD.

We apply the soft-collinear effective theory to deep inelastic scattering near the endpoint region. The forward scattering amplitude and the structure functions are shown to factorize as a convolution of the Wilson coefficients, the jet functions, and the parton distribution functions. The behavior of the parton distribution functions near the endpoint region is considered. It turns out that it evolves with the Altarelli-Parisi kernel even in the endpoint region, and the parton distribution func

We consider phenomenological constraints on the mass ${M}_{{Z}^{\ensuremath{'}}}$ and the mixing angles ${\ensuremath{\theta}}_{R}$ and $\ensuremath{\xi}$ of the neutral sector in general $\mathrm{SU}{(2)}_{L}\ifmmode\times\else\texttimes\fi{}\mathrm{SU}{(2)}_{R}\ifmmode\times\else\texttimes\fi{}\mathrm{U}(1)$ models using electroweak data. The analysis of the neutral sector has the advantage that it has relatively fewer parameters compared to the charged sector since the Cabibbo-Kobayashi-Maska

We consider the effects of a light quark mass in the soft-collinear effective theory (SCET) and we apply them to $\overline{B}\ensuremath{\rightarrow}{X}_{s}\ensuremath{\gamma}$ in the end point region. We find that the reparameterization invariance can be extended by including the collinear quark mass in the SCET Lagrangian. This symmetry constrains the theory with the quark mass terms, and we present explicit results at one loop. It also relates the Wilson coefficients of some mass operators t

We point out that a strong phase from the penguin annihilation channel in $B$ meson decays is sensitive to the treatment of subleading terms with physical $b$ quark mass ${m}_{b}$. In the limit of infinite heavy-quark mass, both the soft-collinear effective theory and the perturbative QCD approach based on the ${k}_{T}$ factorization theorem agree that the strong phase is suppressed. For finite heavy-quark mass, the two approaches predict different results, which are related to the treatment of

We analyze the effects of jet algorithms on each factorized part of the dijet cross sections in ${e}^{+}{e}^{\ensuremath{-}}$ annihilation 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 ${\ensuremath{\alpha}}_{s}$, and are shown to be infrared finite using pure dimensional regularization. The integrated and unintegrated jet functions are presented, and

Using soft-collinear effective theory we describe at leading order in $1/{m}_{b}$ all the semi-inclusive hadronic $B\ensuremath{\rightarrow}XM$ decays near the endpoint, where an energetic light meson $M$ recoils against an inclusive jet $X$. Here we extend to the decays in which spectator quarks go into the jet $X$, and also include the decays involving $\ensuremath{\eta}$, ${\ensuremath{\eta}}^{\ensuremath{'}}$ mesons that receive additional contributions from gluonic operators. The predicted