Yoshio Kitadono

Heavy Quark Effects in the Virtual Photon Structure Functions

2 ,P 2 )a ndF γ L (x,Q 2 ,P 2 ) in the framework of the mass-independent renormalization group equation (RGE). We study a formalism in which the heavy quark mass effects are treated based on parton picture as well as on the operator product expansion (OPE), and perform the numerical evaluation of F γ eff (x,Q 2 ,P 2 ) to the next-leading order (NLO) in QCD. Subject Index: 165

Target mass corrections for the virtual photon structure functions to the next-to-next-to-leading order in QCD

2 � x;Q 2 ;P 2 � and F � Lx;Q 2 ;P 2 � in perturbative QCD for the kinematical region � 2 � P 2 � Q 2 , whereQ 2 �� P 2 � is the mass squared of the probe (target) photon andis the QCD scale parameter. We obtain the Nachtmann moments for the structure functions and then, by inverting the moments, we get the expressions in closed form for F � � x;Q 2 ;P 2 � up to the next-to-next-to-leading order and for F �� x;Q 2 ;P 2 � up to the next-to-leading order, both of which include the target mass corrections. Numerical analysis exhibits that target mass effects appear at large x and become sizable near xmax�� 1=� 1 � P 2

Jet substructures of boosted polarized top quarks

We study jet substructures of a boosted polarized top quark, which undergoes the semileptonic decay

Heavy quark effects on parton distribution functions in the unpolarized virtual photon up to the next-to-leading order in QCD

t\to b\ell\nu

Spin analyzing power for polarized top decays with jets

, in the perturbative QCD framework. The jet mass distribution (energy profile) is factorized into the convolution of a hard top-quark decay kernel with the bottom-quark jet function (jet energy function). Computing the hard kernel to leading order in QCD and inputting the latter functions from the resummation formalism, we observe that the jet mass distribution is not sensitive to the helicity of the top quark, but the energy profile is: energy is accumulated faster within a left-handed top jet than within a right-handed one, a feature related to the

Photon structure function in supersymmetric QCD revisited

V-A

Resummation of large logarithms in the heavy-quark effects on the parton distributions inside the virtual photon

structure of weak interaction. It is pointed out that the energy profile is a simple and useful jet observable for helicity discrimination of a boosted top quark, which helps identification of physics beyond the Standard Model at the Large Hadron Collider. The extension of our analysis to other jet substructures, including those associated with a hadronically decaying polarized top quark, is proposed.

Top quark effects on the virtual photon structure function at ILC

We investigate the heavy-quark mass effects on the parton distribution functions in the unpolarized virtual photon up to the next-to-leading order in QCD. Our formalism is based on the QCD-improved parton model described by the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi evolution equation as well as on the operator product expansion supplemented by the mass-independent renormalization group method. We evaluate the various components of the parton distributions inside the virtual photon with the massive quark effects, which are included through the initial condition for the heavy-quark distributions, or equivalently from the matrix element of the heavy-quark operators. We discuss some features of our results for the heavy-quark effects and their factorization-scheme dependence.

NNLO QCD analysis of the virtual photon structure functions

We perform perturbative QCD factorization of infrared radiations associated with an energetic b quark from a polarized top quark decay, taking the semi-leptonic channel as an example. The resultant formula is expressed as a convolution of an infrared-finite heavy-quark kernel with a bquark jet function. Evaluating the heavy-quark kernel up to leading order in the coupling constant and adopting the jet function from QCD resummation, we predict the dependence of the spin analyzing power for a polarized top quark on the invariant mass of the b-quark jet. It is observed that the spin analyzing power could be enhanced by a factor 2 compared to the inclusive case with the jet mass being integrated over. It is worthwhile to test experimentally the enhancement of the spin analyzing power due to the inclusion of jet dynamics.

Jet substructures of boosted polarized hadronic top quarks

Abstract We investigate the virtual photon structure function in the supersymmetric QCD (SQCD), where we have squarks and gluinos in addition to the quarks and gluons. Taking into account the heavy particle mass effects to the leading order in QCD and SQCD we evaluate the photon structure function and numerically study its behavior for the QCD and SQCD cases.