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H. Masui

Publications and source records attributed to H. Masui.

6 recordsLinked to original sources
arXiv2020

Two-neutron halo structure of $^{31}$F and a novel pairing anti-halo effect

Background: A newly identified dripline nucleus $^{31}$F offers a unique opportunity to study the two-neutron ($2n$) correlation at the east shore of the island of inversion where the $N = 28$ shell closure is lost. Purpose: We aim to present the first three-body theoretical results for the radius and total reaction cross sections of $^{31}$F. This will further help to investigate how the pairing and breakdown of the $N = 28$ shell closure influence the formation of the $2n$-halo structure and the anti-halo effect in this mass region. Methods: A $^{29}$F$+n+n$ three-body system is described by the cluster orbital shell model, and its total reaction cross section is calculated by the Glauber theory. Results: Our three-body calculations predict 3.48-3.70 fm for the root-mean-square radius of $^{31}$F, which corresponds to the total reaction cross section of 1530 (1410)-1640 (1500) mb for a carbon target at 240 (900) MeV/nucleon. The binding mechanism and halo formation in $^{31}$F are discussed. Conclusions: The present study suggests a novel anti-halo effect in this mass region: When the pairing overcome the energy gap between the $p_{3/2}$ and $f_{7/2}$ orbits, the inversion of the occupation number of these orbits takes place, and it diminishes the $2n$-halo structure.

nucl-th↗
arXiv2014

Blast Wave Fits to Elliptic Flow Data at $\sqrt{s_{\rm NN}} =$ 7.7--2760 GeV

We present blast wave fits to elliptic flow ($v_{2}(p_{\rm T})$) data in minimum bias collisions from the $\sqrt{s_{\rm NN}} =$ 7.7--200 GeV at RHIC, and 2.76 TeV at LHC. The fits are performed separately for particles and corresponding anti-particles. The mean transverse velocity parameter $\beta$ shows an energy dependent difference between particles and corresponding anti-particles, which increases as the beam energy decreases. Possible effects of feed down, baryon stopping, anti-particle absorption, and early production times for anti-particles are discussed.

hep-ph↗
arXiv2009

The centrality dependence of v2/epsilon: the ideal hydro limit and eta/s

The large elliptic flow observed at RHIC is considered to be evidence for almost perfect liquid behavior of the strongly coupled quark-gluon plasma produced in the collisions. In these proceedings we present a two parameter fit for the centrality dependence of the elliptic flow scaled by the spatial eccentricity. We show by comparing to viscous hydrodynamical calculations that these two parameters are in good approximation proportional to the shear viscosity over entropy ratio and the ideal hydro limit of the ratio v2/epsilon.

nucl-ex↗
arXiv2009

System size, energy and centrality dependence of strange hadron elliptic flow at STAR

The elliptic flow (v2) pattern in terms of hadron mass and transverse momentum pT is qualitatively described for pT < 2 GeV/c by ideal hydrodynamics in Au + Au collisions at RHIC. In addition, for pT = 2 - 6 GeV/c the measured v2 follow a universal scaling by the number of quarks explained by quark coalescence/recombination models. These observations suggest that a partonic collectivity develops in the matter in early stage of heavy ion collisions. Centrality as well as system size and energy dependence of the v2 is important to shed light on the underlying collision dynamics in heavy ion collisions. We present the measurements of centrality dependence of v2 at sqrt{sNN} = 200 and 62.4 GeV in Au + Au and Cu + Cu collisions for K0S, phi, Lambda, Xi and Omega at STAR experiment. We focus on the recent Cu + Cu results and discuss the centrality dependence of v2 as well as the number of quark scaling as a function of transverse kinetic energy at different system size and energies. We also discuss the eccentricity scaled v2 for identified hadrons and implications that ideal hydrodynamical limit has not been reached at RHIC.

nucl-ex↗
arXiv2005

Anisotropic Flow in sqrt(s_NN) = 200 GeV Cu+Cu and Au+Au collisions at PHENIX

We report the measurement of anisotropic flow at RHIC - PHENIX experiment. We present the v_4 results at sqrt(s_NN) = 200 GeV in Au+Au collision. The scaling ratio of v_4/(v_2)^2 is about 1.5 and it is found to be smaller than the prediction from simple coalescence model. The v_2 for high p_T identified particles ($\sim$ 5 GeV/c) measured with Aerogel Cherenkov Counter are presented. We discuss the constituent quark scaling of v_2 for identified particles. We also report the first observation of v_2 for inclusive charged hadrons as well as identified hadrons at sqrt(s_NN) = 200 GeV in Cu+Cu collisions. The system size dependence of v_2 and scaling properties are discussed.

nucl-ex↗