Searcharxiv⌕ Search

arXiv subjects

T. Hirano

Publications and source records attributed to T. Hirano.

65 records · Page 4Linked to original sources
arXiv2008

Topological Identification of Spin-1/2 Two-Leg Ladder with Four-Spin Ring Exchange

A spin-1/2 two-leg ladder with four-spin ring exchange is studied by quantized Berry phases, used as local order parameters. Reflecting local objects, non-trivial ($π$) Berry phase is founded on a rung for the rung-singlet phase and on a plaquette for the vector-chiral phase. Since the quantized Berry phase is topological invariant for gapped systems with the time reversal symmetry, topologically identical models can be obtained by the adiabatic modification. The rung-singlet phase is adiabatically connected to a decoupled rung-singlet model and the vector-chiral phase is connected to a decoupled vector-chiral model. Decoupled models reveals that the local objects are a local singlet and a plaquette singlet respectively.

cond-mat.str-el↗
arXiv2008

Search for a Ridge Structure Origin with Shower Broadening and Jet Quenching

We investigate the role of jet and shower parton broadening by the strong colour field in the $Δη$-$Δϕ$ correlation of high $p_T$ particles. When anisotropic momentum broadening ($Δp_z > Δp_T$) is given to jet and shower partons in the initial stage, a ridge-like structure is found to appear in the two hadron correlation. The ratio of the peak to the pedestal yield is overestimated.

nucl-th↗
arXiv2008

Hadronic dissipative effects on transverse dynamics at RHIC

We simulate the dynamics of Au+Au collisions at the Relativistic Heavy Ion Collider (RHIC) with a hybrid model that treats the quark-gluon plasma macroscopically as an ideal fluid, but models the hadron resonance gas microscopically using a hadronic cascade. We find that much of the mass-ordering pattern for v_2(p_T) observed at RHIC is generated during the hadronic stage due to build-up of additional radial flow. We also find that the mass-ordering pattern is violated for phi meson due to small interaction cross section in the hadron resonance gas.

nucl-th↗
arXiv2007

Onset of $J/ψ$ Melting in Quark-Gluon Fluid at RHIC

A strong $J/ψ$ suppression in central Au+Au collisions has been observed by the PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC). We develop a hydro+$J/ψ$ model in which hot quark-gluon matter is described by the full (3+1)-dimensional relativistic hydrodynamics and $J/ψ$ is treated as an impurity traversing through the matter. The experimental $J/ψ$ suppression pattern in mid-rapidity is reproduced well by the sequential melting of $χ_{\rm c}$, $ψ'$, and $J/ψ$ in dynamically expanding fluid. The melting temperature of directly produced $J/ψ$ is well constrained by the participant-number dependence of the $J/ψ$ suppression and is found to be about $2.T_{\rm c}$ with $T_{\rm c}$ being the pseudo-critical temperature.

hep-ph↗
arXiv2007

Jet-fluid string formation and decay in high-energy heavy-ion collisions

We propose a new hadronization mechanism, jet-fluid string (JFS) formation and decay, to understand observables in intermediate to high-$p_{T}$ regions comprehensively. In the JFS model, hard partons produced in jet lose their energy in traversing the QGP fluid, which is described by fully three-dimensional hydrodynamic simulations. When a jet parton escapes from the QGP fluid, it picks up a partner parton from a fluid and forms a color singlet string, then it decays to hadrons. We find that high-$p_T$ $v_2$ values in JFS are about two times larger than in the independent fragmentation model.

nucl-th↗
arXiv2005

Hadron-string cascade versus hydrodynamics in Cu+Cu collisions at $\sqrt{s_{NN}}=200$ GeV

Single particle spectra as well as elliptic flow in Cu+Cu collisions at $\sqrt{s_{NN}}=200$ GeV are investigated within a hadronic cascade model and an ideal hydrodynamic model. Pseudorapidity distribution and transverse momentum spectra for charged hadrons are surprisingly comparable between these two models. However, a large deviation is predicted for the elliptic flow. The forthcoming experimental data will clarify the transport and thermalization aspects of matter produced in Cu+Cu collisions.

nucl-th↗
arXiv2005

3D Jet Tomography of the Twisted Color Glass Condensate

Jet Tomography is proposed as a new test of Color Glass Condensate (CGC) initial conditions in non-central $A+A$ collisions. The $k_{T}$ factorized CGC formalism is used to calculate the rapidity twist in the reaction plane of both the bulk low $p_T< 2$ GeV matter as well as the rare high $p_T> 6$ GeV partons. Unlike conventional perturbative QCD, the initial high $p_{T}$ CGC gluons are shown to be twisted even further away from the beam axis than the the low $p_T$ bulk at high rapidities $|η|>2$. Differential directed flow $v_{1}(p_{T}>6,|η|>2)$ is proposed to test this novel high $p_T$ rapidity twist predicted by the CGC model.

nucl-th↗
arXiv2002

The effect of early chemical freeze out on radial and elliptic flow from a full 3D hydrodynamic model

We investigate the effect of early chemical freeze-out on radial and elliptic flow by using a fully three dimensional hydrodynamic model. We find that the time evolution of temperature and the thermal freeze-out temperature dependence of average radial flow are different from the results by using a conventional hydrodynamic model in which chemical equilibrium is always assumed. We also analyse the p_t spectrum and v_2(p_t) at the RHIC energy and consistently reproduce experimental data by choosing the thermal freeze-out temperature T_th = 140 MeV.

nucl-th↗
arXiv1997

Electromagnetic Spectrum from QGP Fluid

We calculate thermal photon and electron pair distribution from hot QCD matter produced in high energy heavy-ion collisions, based on a hydrodynamical model which is so tuned as to reproduce the recent experimental data at CERN SPS, and compare these electromagnetic spectra with experimental data given by CERN WA80 and CERES. We investigate mainly the effects of the off-shell properties of the source particles on the electromagnetic spectra.

nucl-th↗
arXiv1996

Thermal Photon Emission from QGP fluid

We compare the numerical results of thermal photon distribution from the hot QCD matter produced by high energy nuclear collisions, based on hydrodynamical model, with the recent experimental data obtained by CERN WA80. Through the asymptotic value of the slope parameter of the transverse momentum distribution, we discuss the characteristic temperature of the QCD fluid.

hep-ph↗