arXiv subjects

Noriyoshi Ishii

Publications and source records attributed to Noriyoshi Ishii.

79 records · Page 5Linked to original sources

arXiv2002

A statistical approach to the QCD phase transition --A mystery in the critical temperature

We study the QCD phase transition based on the statistical treatment with the bag-model picture of hadrons, and derive a phenomenological relation among the low-lying hadron masses, the hadron sizes and the critical temperature of the QCD phase transition. We apply this phenomenological relation to both full QCD and quenched QCD, and compare these results with the corresponding lattice QCD results. Whereas such a statistical approach works well in full QCD, it results in an extremely large estimate of the critical temperature in quenched QCD, which indicates a serious problem in understanding of the QCD phase transition. This large discrepancy traces back to the fact that enough number of glueballs are not yet thermally excited at the critical temperature T_c \simeq 280 MeV in quenched QCD due to the extremely small statistical factor as exp(-m_G/T_c) \simeq 0.00207. This fact itself has a quite general nature independent of the particular choice of the effective model framework. We are thus arrive at a mystery, namely, what is really the trigger of the deconfinement phase transition.

hep-ph↗

arXiv2002

Glueball Properties at Finite Temperature in SU(3) Anisotropic Lattice QCD

The thermal properties of the glueballs are studied using SU(3) anisotropic lattice QCD with beta=6.25, the renormalized anisotropy xi=a_s/a_t=4 over the lattice of the size 20^3\times N_t with N_t = 24, 26, 28, 30, 33, 34, 35, 36, 37, 38, 40, 43, 45, 50, 72 at the quenched level. To construct a suitable operator on the lattice, we adopt the smearing method, and consider its physical meaning in terms of the operator size. First, we construct the temporal correlators G(t) for the 0^{++} and 2^{++} glueballs, using more than 5,000 gauge configurations at each temperature. We then measure the pole-mass of the thermal glueballs from G(t). For the lowest 0^{++} glueball, we observe a significant pole-mass reduction of about 300 MeV near T_c or m_G(T\simeq T_c) \simeq 0.8 m_G(T\sim 0), while its size remains almost unchanged as rho(T) \simeq 0.4fm. Finally, for completeness, as an attempt to take into account the effect of thermal width Gamma(T) at finite temperature, we perform a more general new analysis of G(t) based on its spectral representation. By adopting the Breit-Wigner form for the spectral function rho(omega), we perform the best-fit analysis as a straightforward extension to the standard pole-mass analysis. The result indicates a significant broadening of the peak as Gamma(T) \sim 300 MeV as well as rather modest reduction of the peak center of about 100 MeV near T_c for the lowest 0^{++} glueball. The temporal correlators of the color-singlet modes corresponding to these glueballs above T_c are also investigated.

hep-lat↗

arXiv2002

The Thermal Width of the Glueball at Non-Zero Temperature

We use SU(3) anisotropic lattice QCD at quenched level to study the 0++ glueball correlator at various temperature taking into account the possible existence of the thermal width in the ground-state peak. For this purpose, we adopt the Breit-Wigner ansatz for the appropriate fit-function for the lattice data obtained with 5,500-9,900 gauge configurations at each T. The results show the significant thermal width broadening as Gamma(T_c) \sim 300 MeV with a reduction in the peak center as Delta omega_0(T_c) \sim 100 MeV near the critical temperature T_c.

hep-lat↗

arXiv2002

Scalar Glueball Mass Reduction at Finite Temperature in SU(3) Anisotropic Lattice QCD

We report the first study of the glueball properties at finite temperatures below T_c using SU(3) anisotropic lattice QCD with beta=6.25, the renormalized anisotropy xi \equiv a_s/a_t = 4 and 20^3 \times N_t (N_t=35,36,37,38,40,43,45,50,72) at the quenched level. From the temporal correlation analysis with the smearing method, about 20 % mass reduction is observed for the lowest scalar glueball as m_G(T)=1250 \pm 50MeV for 0.8 T_c < T < T_c in comparison with m_G \simeq 1500 \sim 1700MeV at T \simeq 0.

hep-lat↗

arXiv2001

Glueball Properties at Finite Temperature

We study the glueball properties at finite temperature below T_c using SU(3) anisotropic quenched lattice QCD with beta=6.25, the renormalized anisotropy gamma = a_s/a_t = 4 and 20^3 \times N_t (N_t = 35, 36, 37, 38, 40, 43, 45, 50, 72). From the temporal correlation analysis with the smearing method, we observe the mass reduction of about 20 % for the lowest 0^{++} glueball as m_G(T) = 1.25 \pm 0.1 GeV for 0.8 T_c < T < T_c in comparison with m_G \simeq 1.5 \sim 1.7 GeV at T \sim 0.

hep-lat↗

arXiv2001

Glueball properties in anisotropic SU(3) lattice QCD with improved action

We study the glueballs properties at finite temperature using SU(3) lattice QCD at the quenched level with the anisotropic lattice. We use the tree-level Symanzik O(a^2) improved action. We present our preliminary results which shows the slight reduction of the scalar glueball mass near T_c

hep-lat↗

arXiv2000

Goldberger-Treiman Relation and g_piNN from the Three Quark BS/Faddeev Approach in the NJL Model

A systematic evaluation method of matrix elements of quantum one-body operators between nucleon states in the three-quark Bethe-Salpeter(3qBS)/Faddeev approach in the NJL model is reviewed. We do not confine ourselves to a particular truncation scheme of the 3qBS kernel. One of our main aims is to derive a general condition to be imposed on a given BS kernel in order that the PCAC relation is satisfied correctly. We apply this condition to some particular 3qBS kernels. We numerically calculate g_piNN in the 3qBS/Faddeev approach to estimate the violation of the Goldberger-Treiman/PCAC relation due to the UV-regularization scheme. We finally consider the non-vanishing current quark mass effects on the Goldberger-Treiman relation.

nucl-th↗