arXiv subjects

T. Hatsuda

Publications and source records attributed to T. Hatsuda.

108 records · Page 6Linked to original sources

arXiv1996

Tensor Charge of the Nucleon in Lattice QCD

First results of lattice QCD simulation on the nucleon tensor-charge $δq$ are presented. From the quenched QCD simulations with the Wilson quark action at $β= 5.7$ on a 16$^3\times$ 20 lattice and on a $12^3\times 20$ lattice, we find (i) the connected part $δq_{con.}$ is determined with small statistical error, (ii) the disconnected part $δq_{dis.}$, which violates the OZI rule, is consistent with zero, and (iii) the flavor-singlet tensor charge $ δΣ(μ^2 = 2 {\rm GeV}^2) = δu + δd + δs$ takes 0.562(88) at $β=5.7$, which is in contrast with the flavor-singlet axial charge $ΔΣ= 0.1-0.3$.

hep-lat↗

arXiv1996

Light Vector Mesons at Finite Baryon Density

We summarize the current theoretical and experimental status of the spectral changes of vector mesons ($ρ$, $ω$, $ϕ$) at finite baryon density. Various approaches including QCD sum rules, effective theory of hadrons and bag models show decreasing of the vector meson masses in nuclear matter. Possibility to detect the mass shift through lepton pairs in $γ-A$, $p-A$ and $A-A$ reactions are also discussed.

nucl-th↗

arXiv1996

Tensor Charge of the Nucleon on the Lattice

Tensor charge of the nucleon, which will be measured in Drell-Yan processes in polarized proton-proton collisions at RHIC, are studied in quenched lattice QCD simulation. On the 16$^3\times$ 20 lattice with $β=5.7$, connected parts of the tensor charge are determined with small statistical error, while the disconnected parts are found to be small with relatively large error bars. Flavor-singlet tensor charge ($δΣ= δu + δd + δs$) is not suppressed as opposed to the flavor singlet axial charge ($ΔΣ= Δu + Δd + Δs$).

hep-lat↗

arXiv1996

Light Vector Mesons in Nuclear Matter

We summarize the current theoretical and experimental status of the spectral changes of vector mesons ($ρ$, $ω$, $ϕ$) in nuclear medium. Various approaches including QCD sum rules, effective theory of hadrons and bag models show decreasing of the vector meson masses in nuclear matter. Possibility to detect the mass shift through lepton pairs in $γ-A$, $p-A$ and $A-A$ reactions are also discussed.

nucl-th↗

arXiv1996

$U_A(1)$ symmetry restoration in QCD with $N_f$ flavors

Recently, there have been reports that the chirally restored phase of QCD is effectively symmetric under $U(N_f) \times U(N_f)$ rather than $SU(N_f)\times SU(N_f)$. We supplement their argument by including the contributions from topologically nontrivial gauge field configurations and discuss how the conclusions are modified. General statements are made concerning the particle spectrum of QCD with light $N_f$ flavors in the high temperature chirally restored phase.

hep-ph↗

arXiv1995

What Thermodynamics tells about QCD Plasma near Phase Transition

Due to a rapid change of the entropy density $s(T)$ across the critical temperature $T_c$ of the QCD phase transition, the pressure $P(T)$ and the energy density $e(T)$ above $T_c$ generally deviate from their Stefan-Boltzmann values. We shall demonstrate this both analytically and numerically for a general class of $s(T)$ consistent with thermodynamical constraints and make a qualitative comparison of the result with the lattice QCD data. Quantities related to $ds(T)/dT$ such as the specific heat and sound velocity are also discussed.

hep-ph↗

arXiv1995

phi-meson in Nuclear Matter

$ϕ$-meson mass in nuclear matter ($m_ϕ^*$) is investigated using an effective Lagrangian of $ϕ$ interacting with octet baryons. $m_ϕ^*$ decreases by a few \% in nuclear matter due to the current conservation and effective nucleon/hyperon masses. Its implication to the p-A and A-A collisions are briefly discussed.

nucl-th↗

arXiv1995

The Pion-Nucleon Coupling Constant in QCD Sum Rules

The pion-nucleon coupling constant $g_{πN}$ is studied on the basis of the QCD sum rules. Both the Borel sum rules and the finite energy sum rules for $g_{πN}$ are used to examine the effects of higher dimensional operators (up to dim. 7) and $α_s$ corrections in the operator product expansion. Agreement with the experimental number is reached only when $S_π/S_N$ is greater than one, where $S_π$ ($S_N$) is the continuum threshold for the $g_{πN}$ (nucleon) sum rule.

hep-ph↗

arXiv1994

Gauge Fields Emerging From Extra Dimensions a Born-Oppenheimer approach

We propose a dynamical mechanism to induce gauge fields in four dimensional space-time from a single scalar field or a spinor field in higher dimensions. The Born-Oppenheimer treatment of the extra dimensions is an essential ingredient in our approach. A possible applications of the idea to low dimensional condensed matter systems and high temperature field theory are also pointed out. This paper is an extended version of our previous unpublished work (SUNY-NTG-89-48, Jan. 1990).

hep-th↗

arXiv1994

Hadronic screening masses and the magnetic gluon condensate at high temperature

The hadronic screening mass at high temperature ($T$) in QCD$_4$ is examined on the basis of the QCD sum rules in (2+1) dimensions. Due to the magnetic gluon condensate at high $T$ which is expected to be nonvanishing, the screening mass deviates from the asymptotic value $2πT$. Also, the screening mass in the vector (pseudo-vector) channel turns out to be heavier than that in the scalar (pseudo-scalar) channel.

hep-ph↗

arXiv1994

Vector Mesons in Nuclear Medium -- an Effective Lagrangian Approach --

Effective masses of $ρ$ and $ω$ mesons in nuclear medium are studied in a hadronic effective theory. Both the pole position and the screening mass decrease in nuclear matter due to the polarization of the nucleon Dirac sea. The physical origin of the decrease is a reduction of the wave function renormalization constant induced by the tensor (vector) interaction of the $ρ$ ($ω$) with the nucleon. Relation to the results of the QCD sum rules is also discussed.

hep-ph↗

arXiv1994

H dibaryon in the QCD sum rule

The QCD sum rule is applied to the H dibaryon and is compared to the flavor non-singlet di-nucleon. We find that the H dibaryon is almost degenerate to the di-nucleon in the $SU(3)_{flavor}$ limit and therefore is not deeply bound as far as th\ e threshold parameter is adjusted not to have a di-nucleon bound state. After introducing the $SU(3)_{f}$ breaking effects, the H dibaryon is found to be bound by $40 MeV$ below the $ΛΛ$ threshold.

hep-ph↗

arXiv1994

QCD and Quark/Hadron Matter

A brief review on the recent theoretical progress in hot/dense QCD is given. Special emphasis is put on the non-perturbative aspects of QCD plasma and the modification of hadron proporties near the critical temperature of chiral transition.

hep-ph↗

arXiv1994

QCD Phenomenology based on a Chiral Effective Lagrangian

We review the Nambu-Jona-Lasinio (NJL) approach to the dynamical breaking of chiral symmetry in Quantum Chromodynamics (QCD). The subjects treated in Part I include the vacuum structure of QCD, mass spectra and coupling constants of hadrons, flavor mixing in mesons, the violation of the OZI rule in baryons, and the validity of the chiral perturbation in QCD. A subtle interplay between the axial anomaly and the current-quark masses is shown to play important roles, and a realistic evaluation of the strangeness and heavy quark contents of hadrons is given. In Part II, the NJL model is applied to the system at finite temperature ($T$) and density ($ρ$) relevant to the early universe, interior of the neutron stars and the ultra-relativistic heavy ion collisions. The subjects treated here include the quark condensates in the medium, meson properties at finite $T$ ($ρ$) and their experimental implications. A special attention is paid to fluctuation phenomena near the critical temperature. (to be published in Physics Reports)

hep-ph↗

arXiv1993

Comment on: "Nucleon-nucleon scattering lengths in QCD sum rules,"

In a recent Physical Review Letter, Kondo and Morimatsu present a QCD sum rule calculation of nucleon-nucleon scattering lengths. They also relate the empirical scattering lengths to the nucleon mass shift in nuclear matter to cast doubt on the "linear density approximation." In this Comment, we point out flaws in both parts of their analysis and draw very different conclusions.

hep-ph↗

arXiv1993

Transverse Quark Distribution in Mesons - QCD Sum Rule Approach -

QCD sum rules are used to compute the first few moments of the mesonic quark momentum. Transverse, longitudinal and mixed transverse-longitudinal components are examined. The transverse size of the pion is shown to be dictated by the gluon condensate, even though the mass and the longitudinal distribution are dominated by the quark condensate. The implications of our results for color transparency physics and finite temperature QCD are discussed.

hep-ph↗

arXiv1993

The Off Shell $ρ$-$ω$ Mixing in the QCD Sum Rules

The $q^2$ dependence of the $ρ-ω$ mixing amplitude is analyzed with the use of the QCD sum rules and the dispersion relation. Going off shell the mixing decreases, changes sign at $q^2 \simeq 0.4 m_ρ^2 > 0$ and is negative in the space like region. Implications of this result to the isospin breaking part of the nuclear force are discussed.

nucl-th↗

arXiv1993

Twist-4 Matrix Elements of the Nucleon from Recent DIS Data at CERN and SLAC

We analyse the recent precision measurements of the lepton-hadron deep inelastic scattering at CERN and SLAC to extract model independent constraints among the nucleon matrix elements of the twist-4 operators. We also study a parameterization of these matrix elements and point out the possibility that the matrix elements of the quark-gluon mixed operator has a negative value of the order of $- (400 \pm 100\ {\rm MeV})^2$ at 5 GeV$^2$ renormalization scale.

hep-ph↗