arXiv subjects

Tsuneo Uematsu

Publications and source records attributed to Tsuneo Uematsu.

At least 37 records · Page 2Linked to original sources

arXiv2002

Virtual photon structure functions and positivity constraints

We study the three positivity constraints among the eight virtual photon structure functions, derived from the Cauchy-Schwarz inequality and which are hence model-independent. The photon structure functions obtained from the simple parton model show quite different behaviors in a massive quark or a massless quark case, but they satisfy, in both cases, the three positivity constraints. We then discuss an inequality which holds among the unpolarized and polarized photon structure functions $F_1^γ$, $g_1^γ$ and $W_{TT}^τ$, in the kinematic region $Λ^2\ll P^2 \ll Q^2$, where $-Q^2 (-P^2)$ is the mass squared of the probe (target) photon, and we examine whether this inequality is satisfied by the perturbative QCD results.

hep-ph↗

arXiv2002

Twist-3 Effects in Polarized Photon Structure

The polarized photon structure is described by two spin structure functions $g_1^γ$ and $g_2^γ$ which can be studied in the future polarized ep or e$^+$e$^-$ colliders. Here we investigate the QCD twist-3 effects in $g_2^γ$ to the leading order in QCD.

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arXiv2002

Polarized Photon Structure: $g_1^γ$ and $g_2^γ$

We investigate the polarized photon structure functions $g_1^γ$ and $g_2^γ$ which can be studied in the future polarized version of ep or e$^+$e$^-$ colliders. The NLO QCD calculations of $g_1^γ$ and the possible twist-3 effects in $g_2^γ$ are discussed.

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arXiv2002

Polarized Virtual Photon Structure Function $g_2^γ$ and Twist-3 Effects in QCD

We investigate the twist-3 effects in the polarized virtual photon structure. The structure functions $g_1^γ$ and $g_2^γ$ of polarized photon could be experimentally studied in the future polarized $ep$ or $e^+e^-$ colliders. The leading contributions to $g_1^γ$ are the twist-2 effects, while another structure function $g_2^γ$, which only exists for the virtual photon target, receives not only the twist-2 but also twist-3 contributions. We first show that the twist-3 effects actually exist in the box-diagram contributions and we extract the twist-3 part, which can also be reproduced by the pure QED operator product expansion. We then calculate the non-trivial lowest moment ($n=3$) of the twist-3 contribution to $g_2^γ$ in QCD. For large $N_c$ (the number of colors), the QCD analysis of the twist-3 effects in the flavor nonsinglet part of $g_2^γ$ becomes tractable and we can obtain its moments in a compact form for all $n$.

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arXiv2001

Generating All Wigner Functions

In the context of phase-space quantization, matrix elements and observables result from integration of c-number functions over phase space, with Wigner functions serving as the quasi-probability measure. The complete sets of Wigner functions necessary to expand all phase-space functions include off-diagonal Wigner functions, which may appear technically involved. Nevertheless, it is shown here that suitable generating functions of these complete sets can often be constructed, which are relatively simple, and lead to compact evaluations of matrix elements. New features of such generating functions are detailed and explored for integer-indexed sets, such as for the harmonic oscillator, as well as continuously indexed ones, such as for the linear potential and the Liouville potential. The utility of such generating functions is illustrated in the computation of star functions, spectra, and perturbation theory in phase space.

hep-th↗

arXiv2000

Factorization Scheme and Parton Distributions in the Polarized Virtual Photon Target

We investigate spin-dependent parton distributions in the polarized virtual photon target in perturbative QCD up to the next-to-leading order (NLO). In the case $Λ^2 \ll P^2 \ll Q^2$, where $-Q^2$ ($-P^2$) is the mass squared of the probe (target) photon, parton distributions can be predicted completely up to NLO, but they are factorization-scheme-dependent.We analyze parton distributions in six different factorization schemes and discuss their scheme dependence. We study, in particular, the QCD and QED axial anomaly effects on the first moments of parton distributions to see the interplay between the axial anomalies and factorization schemes. We also show that the factorization-scheme dependence is characterized by the large-$x$ behaviors of quark distributions in the virtual photon. Gluon distribution is predicted to be the same up to NLO among the six factorization schemes examined. In particular, the first moment of gluon distribution is found to be factorization-scheme independent up to NLO.

hep-ph↗

arXiv2000

Nonlinear Realization of Partially Broken N=2 AdS Supersymmetry in Two and Three Dimensions

We investigate the nonlinear realization of partially broken $N$=2 global supersymmetry in the D=2 and 3 anti de-Sitter (AdS) space. We particularly study Nambu-Goldstone degrees of freedom for the $N$=2 AdS supersymmetry partially broken down to $N$=1 AdS supersymmetry, where we observe a NG fermion of the broken supersymmetry and a NG boson of the internal symmetry which form a NG multiplet. Based on the nonlinear realization method, we construct a superspace formalism for 2 and 3 dimensional AdS space and evaluate the covariant derivatives and supervielbeins for the AdS superspace. Finally we obtain the nonlinear transformation laws and the lowest order of effective Lagrangians.

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arXiv2000

Polarized and Unpolarized Structures of the Virtual Photon

We discuss the structure functions and the parton distributions in the virtual photon target, both polarized and unpolarized, beyond the leading order in QCD. We study the factorization-scheme dependence of the parton distributions.

hep-ph↗

arXiv2000

Parton Distributions in the Virtual Photon Target and Factorization Scheme Dependence

We investigate parton distributions in the virtual photon target, both polarized and unpolarized, up to the next-leading order (NLO) in QCD. Parton distributions can be predicted completely up to NLO, but they are factorization-scheme-dependent. We analyze parton distributions in several factorization schemes and discuss their scheme dependence. Particular attentions are paid to the axial anomaly effect on the first moments of the polarized quark parton distributions, and also to the large-$x$ behaviors of polarized and unpolarized parton distributions.

hep-ph↗

arXiv1999

Polarized Parton Distributions in the Photon and Factorization Scheme Dependence

Spin-dependent parton distributions in the polarized virtual photon are investigated in QCD up to the next-to-leading order (NLO). In the case $Λ^2 \ll P^2 \ll Q^2$, where $-Q^2$ ($-P^2$) is the mass squared of the probe (target) photon, parton distributions can be predicted completely up to the NLO, but they are factorization-scheme-dependent. Parton distributions are analyzed in four different factorization schemes and their scheme dependence are discussed. Particular attentions are paid to the axial anomaly effect on the first moments of quark parton distributions, and also to the large-$x$ behaviors of the parton distributions. Gluon distribution in the virtual photon is found to be factorization-scheme independent up to the NLO.

hep-ph↗

arXiv1999

Spin structure function of the virtual photon

We investigate the spin structure of the virtual photon beyond the leading order in QCD. The first moment of the virtual photon spin structure function $g_1^γ(x,Q^2,P^2)$ with QCD effects turns out to be non-vanishing in contrast to the real photon case. Numerical analysis for virtual as well as real photon case is presented.

hep-ph↗

arXiv1998

Spin Structure Function of the Virtual Photon Beyond the Leading Order in QCD

Polarized photon structure can be studied in the future polarized $e^{+}e^{-}$ colliding-beam experiments. We investigate the spin-dependent structure function of the virtual photon $g_1^γ(x,Q^2,P^2)$, in perturbative QCD for $Λ^2 \ll P^2 \ll Q^2$, where $-Q^2$ ($-P^2$) is the mass squared of the probe (target) photon. The analysis is performed to next-to-leading order in QCD. We particularly emphasize the renormalization scheme independence of the result.The non-leading corrections significantly modify the leading log result, in particular, at large $x$ as well as at small $x$. We also discuss the non-vanishing first moment sum rule of $g_1^γ$, where ${\cal O}(α_s)$ corrections are computed.

hep-ph↗

arXiv1998

Polarized Virtual Photon Structure Function in the Next-to-leading Order in QCD

The virtual photon structure function $g_1^γ(x,Q^2,P^2)$, which can be obtained in polarized $e^{+}e^{-}$ colliding-beam experiments, is investigated for $Λ^2 \ll P^2 \ll Q^2$, where $-Q^2$ ($-P^2$) is the mass squared of the probe (target) photon. The analysis is made to next-to-leading order in QCD, in the framework of the QCD improved parton model with the DGLAP evolution equations. The non-leading corrections significantly modify the leading log result, in particular, at large $x$ as well as at small $x$.

hep-ph↗

arXiv1997

Nonlinear Realization of Partially Broken N=2 Superconformal Symmetry in Four Dimensions

We investigate the nonlinear realization of spontaneously broken N=2 superconformal symmetry in 4 dimensions. We particularly study Nambu-Goldstone degrees of freedom for the partial breaking of N=2 superconformal symmetry down to N=1 super-Poincar{é} symmetry, where we get the chiral NG multiplet of dilaton and the vector NG multiplet of NG fermion of broken Q-supersymmetry. Evaluating the covariant differentials and supervielbeins for the chiral as well as the full superspace, we obtain the nonlinear effective lagrangians.

hep-th↗

arXiv1996

Renormalization of Twist-4 Operators in QCD Bjorken and Ellis-Jaffe Sum Rules

The QCD effects of twist-4 operators on the first moment of nucleon spin-dependent structure function $g_1(x, Q^2 )$ are studied in the framework of operator product expansion and renormalization group method. We investigate the operator mixing through renormalization of the twist-4 operators including those proportional to the equation of motion by evaluating off-shell Green's functions in the usual covariant gauge as well as in the background gauge. Through this procedure we extract the one-loop anomalous dimension of the spin 1 and twist-4 operator which determines the logarithmic correction to the $1/Q^2$ behavior of the contribution from the twist-4 operators to the first moment of $g_1(x,Q^2)$.

hep-ph↗

arXiv1996

Higher-twist Effects in Spin Structure Functions

We discuss the QCD effects of the higher-twist operators in the nucleon spin-dependent structure functions measured by the polarized deep inelastic leptoproduction. We particularly study the renormalization of the twist-3 and twist-4 operators within the framework of operator product expansions and renormalization group methods in perturbative QCD. Emphasis will be placed on the role of the operators proportional to equation of motion which appear in the mixing of the higher-twist operators through renormalization. The logarithmic and power corrections in $Q^2$ due to the lowest spin higher-twist operators are discussed for the first moment of $g_1$ structure function, Bjorken and Ellis-Jaffe sum rules, as well as the lower moments of $g_2$ structure function.

hep-ph↗

arXiv1996

QCD Corrections to the nucleon's spin structure function $G_2(x,Q^2)$

We investigate the renormalization of the twist-3 operators which are relevant for the spin-dependent structure function $g_{2}(x, Q^{2})$. We derive the anomalous dimension for the non-singlet part by calculating the off-shell Green's functions of the twist-3 operators including the operators which are proportional to the equation of motion.

hep-ph↗

arXiv1996

Geometry and Duality in Supersymmetric sigma-Models

The Supersymmetric Dual Sigma Model (SDSM) is a local field theory introduced to be nonlocally equivalent to the Supersymmetric Chiral nonlinear sigma-Model (SCM), this dual equivalence being proven by explicit canonical transformation in tangent space. This model is here reconstructed in superspace and identified as a chiral-entwined supersymmetrization of the Dual Sigma Model (DSM). This analysis sheds light on the Boson-Fermion Symphysis of the dual transition, and on the new geometry of the DSM.

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