119523786
Particle Physics Experiments at JLC
ACFA Linear Collider Working Group report
16486400
The resummation approach to evolution equations
We derive the evolution equations of parton distribution functions appropriate in different kinematic regions in a unified and simple way using the resummation technique. They include the Gribov-Lipatov-Altarelli-Parisi equation for large momentum transfer $Q$, the Balitskii-Fadin-Kuraev-Lipatov equation for a small Bjorken variable $x$, and the Ciafaloni-Catani-Fiorani-Marchesini equation which unifies the above two equations. We propose a modified Balitskii-Fadin-Kuraev-Lipatov equation from the view point of the resummation. This modified version possesses an intrinsic $Q$ dependence and its predictions for the structure function $F_2(x,Q^2)$ are consistent with the HERA data.
124014107
Extraction of V(ub) from decay B ---> pi lepton neutrino
108240
Fat penguins and imaginary penguins in perturbative QCD
Abstract We evaluate B → Kπ decay amplitudes in perturbative QCD picture. It is found that penguin contributions are dynamically enhanced by nearly 50% compared to those assumed in the factorization approximation. It is also shown that annihilation diagrams are not negligible, and give large strong phases. Our results for branching ratios of B → Kπ decays for a representative parameter set are consistent with data.
5428879
Origin of the $k_{T}$ smearing in direct photon production
We show that the Sudakov factor from the resummation of double logarithms $\ln(s/k_T^2)$ contained in the distribution functions is responsible for the $k_T$ smearing mechanism employed in the next-to-leading-order QCD ($\alpha\alpha_s^2$) calculations of direct photon production. $s$ is the center-of-mass energy, and $k_T$ the transverse momentum carried by a parton in a colliding hadron. This factor exhibits the appropriate $s$-dependent Gaussian width in $k_T$, such that our predictions are in good agreement with experimental data.
7999949
Factorization theorems, effective field theory, and nonleptonic heavy meson decays
The nonleptonic heavy meson decays B → D (∗) π(ρ), J/ψK (∗) and D → K (∗) π are studied based on the three-scale perturbative QCD factorization theorem developed recently. In this formalism the Bauer-Stech-Wirbel parameters a1 and a2 are treated as the Wilson coefficients, whose evolution from the W boson mass down to the characteristic scale of the decay processes is determined by effective field theory. The evolution from the characteristic scale to a lower hadronic scale is formulated by the Sudakov resummation. The scale-setting ambiguity, which exists in the conventional approach to nonleptonic heavy meson decays, is moderated. Nonfactorizable and nonspectator contributions are taken into account as part of the hard decay subamplitudes. Our formalism is applicable to both bottom and charm decays, and predictions, including those for the ratios R and RL associated with the B → J/ψK (∗) decays, are consistent with experimental data.
119523786
Particle Physics Experiments at JLC
ACFA Linear Collider Working Group report