arXiv subjects

Tetsuo Hatsuda

Publications and source records attributed to Tetsuo Hatsuda.

At least 145 records · Page 8Linked to original sources

arXiv2009

Electron-muon correlation as a new probe to strongly interacting quark-gluon plasma

As a new and clean probe to the strongly interacting quark-gluon plasma (sQGP), we propose an azimuthal correlation of an electron and a muon which originate from the semileptonic decay of charm and bottom quarks. By solving the Langevin equation for the heavy quarks under the hydrodynamic evolution of the hot plasma, we show that substantial quenching of the away-side peak in the electron-muon correlation can be seen if the sQGP drag force acting on heavy quarks is large enough as suggested from the gauge/gravity correspondence. The effect could be detected in high-energy heavy-ion collisions at the Relativistic Heavy Ion Collider and the Large Hadron Collider.

hep-ph↗

arXiv2008

Energy dependence of nucleon-nucleon potentials

We investigate the energy dependence of potentials defined through the Bethe-Salpeter wave functions. We analytically evaluate such a potential in the Ising field theory in 2 dimensions and show that its energy dependence is weak at low energy. We then numerically calculate the nucleon-nucleon potential at non-zero energy using quenched QCD with anti-periodic boundary condition. In this case we also observe that the potentials are almost identical at $E\simeq 0$ and $E\simeq 50$ MeV, where $E$ is the center of mass kinetic energy.

hep-lat↗

arXiv2008

Heavy Quark Diffusion with Relativistic Langevin Dynamics in the Quark-Gluon Fluid

The relativistic diffusion process of heavy quarks is formulated on the basis of the relativistic Langevin equation in Itô discretization scheme. The drag force inside the quark-gluon plasma (QGP) is parametrized according to the formula for the strongly coupled plasma obtained by the AdS/CFT correspondence. The diffusion dynamics of charm and bottom quarks in QGP is described by combining the Langevin simulation under the background matter described by the relativistic hydrodynamics. Theoretical calculations of the nuclear modification factor R_{AA} and the elliptic flow v_{2} for the single electrons from the charm and bottom decays are compared with the experimental data from the relativistic heavy ion collisions. The R_{AA} for electrons with large transverse momentum (p_{T} > 3 GeV) indicates that the drag force from the QGP is as strong as the AdS/CFT prediction.

hep-ph↗

arXiv2008

Spectral Continuity in Dense QCD

The vector mesons in three-flavor quark matter with chiral and diquark condensates are studied using the in-medium QCD sum rules. The diquark condensate leads to a mass splitting between the flavor-octet and flavor-singlet channels. At high density, the singlet vector meson disappears from the low-energy spectrum, while the octet vector mesons survive as light excitations with a mass comparable to the fermion gap. A possible connection between the light gluonic modes and the flavor-octet vector mesons at high density is also discussed.

hep-ph↗

arXiv2008

The axial anomaly and the phases of dense QCD

The QCD axial anomaly, by coupling the chiral condensate and BCS pairing fields of quarks in dense matter, leads to a new critical point in the QCD phase diagram \cite{HTYB,chiral2}, which at sufficiently low temperature should terminate the line of phase transitions between chirally broken hadronic matter and color superconducting quark matter. The critical point indicates that matter at low temperature should cross over smoothly from the hadronic to the quark phase, as suggested earlier on the basis of symmetry. We review here the arguments, based on a general Ginzburg-Landau effective Lagrangian, for the existence of the new critical point, as well as discuss possible connections between the QCD phase structure and the BEC-BCS crossover in ultracold trapped atomic fermion systems at unitarity. and implications for the presence of quark matter in neutron stars.

nucl-th↗

arXiv2007

Phase structure, collective modes, and the axial anomaly in dense QCD

Using a general Ginzburg-Landau effective Lagrangian, we study the topological structure and low-lying collective modes of dense QCD having both chiral and diquark condensates, for two and three massless flavors. As we found earlier, the QCD axial anomaly acts as an external field applied to the chiral condensate in a color superconductor and, as a new critical point emerges, leads to a crossover between the broken chiral symmetry and color superconducting phases. At intermediate densities where both chiral and diquark condensates are present, we derive a generalized Gell-Mann- Oakes-Renner relation between the masses of pseudoscalar bosons and the magnitude of the chiral and diquark-condensates. We show explicitly the continuity of the ordinary pion at low densities to a generalized pion at high densities.

hep-ph↗

arXiv2007

Bulk and Spectral Observables in Lattice QCD

We review recent developments in lattice siumulations of the equation of state, order of the thermal phase transition and the determination of the pseudo-critical temperature in (2+1)-flavor QCD. Owing to the increasing computer power, new argothithms, and improved fermion formulations, studies of bulk QCD matter are approaching to the stage of precision science. We also review recent lattice studies on the spectral properties of heavy quarkoniums inside the quark-gluon plasma (QGP). Although they are still in an exploratory stage, interesting physics in relation to the strongly correlated QGP is being extracted.

hep-ph↗

arXiv2006

New Critical Point Induced by the Axial Anomaly in Dense QCD

We study the interplay between chiral and diquark condensates within the framework of the Ginzburg-Landau free energy, and classify possible phase structures of two and three-flavor massless QCD. The QCD axial anomaly acts as an external field applied to the chiral condensate in a color superconductor and leads to a crossover between the broken chiral symmetry and the color superconducting phase, and, in particular, to a new critical point in the QCD phase diagram.

hep-ph↗

arXiv2006

First lattice study of low-energy charmonium-hadron interaction

We study the scattering lengths of charmonia (J/psi and eta_c) with light hadrons (pi, rho and N) by the quenched lattice QCD simulations on 24x24x24x48, 32x32x32x48 and 48x48x48x48 lattices with the lattice spacing a = 0.068 fm. The scattering length is extracted by using the Luscher's phase-shift formula together with the measurement of the energy shift Delta E of two hadrons on the lattice. We find that there exist attractive interactions in all channels, J/psi(eta_c)-pi, J/psi(eta_c)-rho and J/psi(eta_c)-N: The s-wave J/psi-pi (eta_c-pi) scattering length is determined as 0.0119+-0.0039 fm (0.0113+-0.0035 fm) and the corresponding elastic cross section at the threshold becomes 0.018+0.013-0.010 mb (0.016+0.011-0.008 mb). Also, the J/psi-N (eta_c-N) spin-averaged scattering length is 0.71+-0.48 fm (0.70+-0.66 fm), which is at least an order of magnitude larger than the charmonium-pion scattering length. The volume dependence of the energy shifts is also investigated to check the expected 1/L^3 behavior of Delta E at a large spatial size L.

hep-lat↗

arXiv2005

Study of color superconductivity with Ginzburg-Landau effective action on the lattice

We study thermal phase transitions of color superconductivity by the lattice simulations of the Ginzburg-Landau (GL) effective theory. The theory is equivalent to the SU_ f(3) cross SU_c(3) Higgs model coupled to SU_c(3) color gauge fields. From the eigenvalues of a 3-by-3 gauge-invariant diquark composite, a clear distinction between the 2-flavor color superconductivity (2SC) and the color flavor locking (CFL) phase is made in a gauge invariant manner. The thermal transitions between the normal phase and the superconducting phases are found to be first-order due to thermal gluons. The phase structure in the coupling-constant space is numerically explored and three patterns of phase transition, i.e., normal to 2SC, normal to CFL and normal to CFL via 2SC, are found in the chiral limit. These results agree qualitatively with the weak-coupling analysis of the GL theory.

hep-lat↗

arXiv2005

Hadrons Above T_c

Hadronic modes in the quark-gluon plasma and their spectral properties are discussed on the basis of the lattice QCD data.

hep-ph↗

arXiv2005

QCD Level Density from Maximum Entropy Method

We propose a method to calculate the QCD level density directly from the thermodynamic quantities obtained by lattice QCD simulations with the use of the maximum entropy method (MEM). Understanding QCD thermodynamics from QCD spectral properties has its own importance. Also it has a close connection to phenomenological analyses of the lattice data as well as experimental data on the basis of hadronic resonances. Our feasibility study shows that the MEM can provide a useful tool to study QCD level density.

hep-lat↗

arXiv2005

Spectral Analysis of Excited Nucleons in Lattice QCD with Maximum Entropy Method

We study the mass spectra of excited baryons with the use of the lattice QCD simulations. We focus our attention on the problem of the level ordering between the positive-parity excited state N'(1440) (the Roper resonance) and the negative-parity excited state N^*(1535). Nearly perfect parity projection is accomplished by combining the quark propagators with periodic and anti-periodic boundary conditions in the temporal direction. Then we extract the spectral functions from the lattice data by utilizing the maximum entropy method. We observe that the masses of the N' and N^* states are close for wide range of the quark masses (M_pi=0.61-1.22 GeV), which is in contrast to the phenomenological prediction of the quark models. The role of the Wilson doublers in the baryonic spectral functions is also studied.

hep-lat↗

arXiv2005

Strange Tribaryons as Nona-quark States

Strange tribaryons as nona-quark (9 quark) states is studied to describe the S=-1 resonance S^0(3115) recently discovered in the reaction K- + ^4 He -> S^0 + p. We have identified S^0(3115) as a member of the flavor 27-plet, in particular, (F_{flavor},I_{isospin},J_{spin})=(27,1,1/2) or (27,1,3/2). The color-magnetic interaction between quarks favors small multiplets in flavor and spin, which leads to a natural explanation that I=1 is the lowest state among the S=-1 tribaryons with J=1/2. Classification of the S^+ -state recently reported as well as possible locations of other light strange tribaryons such as (10*,0,3/2) with S=-1, (8,1/2,1/2) with S=-2 and (1,0,3/2) with S=-3 are also discussed.

hep-ph↗

arXiv2005

Wandering in Color-Space -- why the life of pentaquark is so long ? --

The problem of the long life time of the pentaquark $Θ^+$ is investigated on the basis of the color molecular dynamics simulation. We find that it takes a long time (typically of 50-100 fm/c) for the initial pentaquark-state to rearrange its color and spatial positions to decay into the nucleon + kaon final state. Structure of the potential surface in the color and position spaces also supports this picture. Pentaquark wanders on the potential surface to find a narrow channel to decay.

hep-ph↗

arXiv2004

Thermal fluctuations of gauge fields and first order phase transitions in color superconductivity

We study the effects of thermal fluctuations of gluons and the diquark pairing field on the superconducting-to-normal state phase transition in a three-flavor color superconductor, using the Ginzburg-Landau free energy. At high baryon densities, where the system is a type I superconductor, gluonic fluctuations, which dominate over diquark fluctuations, induce a cubic term in the Ginzburg-Landau free energy, as well as large corrections to quadratic and quartic terms of the order parameter. The cubic term leads to a relatively strong first order transition, in contrast with the very weak first order transitions in metallic type I superconductors. The strength of the first order transition decreases with increasing baryon density. In addition gluonic fluctuations lower the critical temperature of the first order transition. We derive explicit formulas for the critical temperature and the discontinuity of the order parameter at the critical point. The validity of the first order transition obtained in the one-loop approximation is also examined by estimating the size of the critical region.

hep-ph↗

arXiv2004

Thermodynamics of strong coupling 2-color QCD with chiral and diquark condensates

2-color QCD (quantum chromodynamics with N_c=2) at finite temperature T and chemical potential μis revisited in the strong coupling limit on the lattice with staggered fermions. The phase structure in the space of T, μ, and the quark mass m is elucidated with the use of the mean field approximation and the 1/d expansion (d being the number of spatial dimensions). We put special emphasis on the interplay among the chiral condensate <\bar{q}q>, the diquark condensate , and the quark density in the T-μ-m space. Simple analytic formulae are also derived without assuming μnor m being small. Qualitative comparisons are made between our results and those of recent Monte-Carlo simulations in 2-color QCD.

hep-ph↗

arXiv2003

Order parameters with higher dimensionful composite fields

We discuss the possibility of the spontaneous symmetry breaking characterized by order parameters with higher dimensionful composite fields. By analyzing general Ginzburg-Landau potential for a complex scalar field ϕ=ϕ_1 + i ϕ_2 with O(2) symmetry, we demonstrate that a phase characterized by < ϕ_1^2 - ϕ_2^2 > \neq 0 with < ϕ_1 >=< ϕ_2 >=0 is realized in a certain parameter region. To clarify the driving force to favor this phase, we study the O(2) ϕ^6 theory in three dimensions.

hep-th↗