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Minoru Biyajima

Publications and source records attributed to Minoru Biyajima.

31 records · Page 2Linked to original sources
arXiv2008

Diffusion or bounce back in relativistic heavy-ion collisions?

The time evolution of pseudorapidity distributions of produced charged hadrons in d+Au collisions at sqrt(s_NN) = 200 GeV is investigated. Results of a nonequilibrium-statistical Relativistic Diffusion Model with three sources are compared with a macroscopic "bounce back" model that does not allow for statistical equilibration at large times, but instead leads to motion reversal. When compared to the data, the results of the diffusion approach are more precise, thus emphasizing that the system is observed to be on its way to thermal equilibrium.

hep-ph↗
arXiv2006

Third order Bose-Einstein correlations by means of Coulomb wave function revisited

In previous works, in order to include correction by the Coulomb wave function in Bose-Einstein correlations (BEC), the two-body Coulomb scattering wave functions have been utilized in the formulation of three-body BEC. However, the three-body Coulomb scattering wave function, which satisfies approximately the three-body Coulomb scattering Schrodinger equation, cannot be written by the product of the two-body scattering wave functions. Therefore, we reformulate the three-body BEC, and reanalyze the data. A set of reasonable parameters is obtained.

hep-ph↗
arXiv2006

Time evolution of relativistic d + Au and Au + Au collisions

The evolution of charged-particle production in collisions of heavy ions at relativistic energies is investigated as function of centrality in a nonequilibrium-statistical framework. Precise agreement with recent d + Au and Au + Au data at sqrt(s_NN) = 200 GeV is found in a Relativistic Diffusion Model with three sources for particle production. Only the midrapidity source comes very close to local equilibrium, whereas the analyses of the overall pseudorapidity distributions show that the systems remain far from statistical equilibrium.

hep-ph↗
arXiv2005

Local Thermalization in the d + Au System

The extent of a locally equilibrated parton plasma in d + Au collisions at sqrt(s_NN) = 200 GeV is investigated as a function of collision centrality in a nonequilibrium-statistical framework. Based on a three-sources model, analytical solutions of a relativistic diffusion equation are in precise agreement with recent data for charged-particle pseudorapidity distributions. The moving midrapidity source indicates the size of the local thermal equilibrium region after hadronization. In central d + Au collisions it contains about 19% of the produced particles, and its relative importance rises with decreasing centrality.

hep-ph↗
arXiv2005

Analyses of third order Bose-Einstein correlation by means of Coulomb wave function

In order to include a correction by the Coulomb interaction in Bose-Einstein correlations (BEC), the wave function for the Coulomb scattering were introduced in the quantum optical approach to BEC in the previous work. If we formulate the amplitude written by Coulomb wave functions according to the diagram for BEC in the plane wave formulation, the formula for $3π^-$BEC becomes simpler than that of our previous work. We re-analyze the raw data of $3π^-$BEC by NA44 and STAR Collaborations by this formula. Results are compared with the previous ones.

hep-ph↗
arXiv2005

Relativistic diffusion model and analysis of large transverse momentum distributions

In order to describe large transverse momentum ($p_T$) distributions observed in high energy nucleus-nucleus collisions, a stochastic model in the three dimensional rapidity space is introduced. The fundamental solution of the radial symmetric diffusion equation is Gaussian-like in radial rapidity. We can also derive a $p_T$ or radial rapidity distribution function, where a distribution of emission center is taken into account. It is applied to the analysis of observed large $p_T$ distributions of charged particles. It is shown that our model approaches to a power function of $p_T$ in the high transverse momentum limit.

hep-ph↗
arXiv2004

Analytic solution for Brownian motion in three dimensional hyperbolic space

Brownian motion in the three dimensional Lobachevsky space or hyperbolic space is considered in the paper written by F.I.Karpelevich, V.N.Tutubalin and M.G.Shur. A solution for radial symmetric diffusion equation in the three dimensional hyperbolic space is given in that paper. However, derivation of it is not explicitly shown. Therefore, the diffusion equation is solved analytically with an initial condition corresponding to non-zero space variable at the initial stage.

math-ph↗
arXiv2003

Description of η-distributions at RHIC energies in terms of a stochastic model

To explain η-distributions at RHIC energies we consider the Ornstein-Uhlenbeck process. To account for hadrons produced in the central region, we assume existence of third source located there (y \approx 0) in addition to two sources located at the beam and target rapidities (\pm y_{max} = \pm \ln[\sqrt{s_{NN}}/m_{N}]). This results in better χ^2/n.d.f. than those for only two sources when analysing data.

nucl-th↗
arXiv2002

Analysis of solar neutrino problem by means of Nötzold and Nakagawa's approach including the interference term- Hyperbolic-tangent profile for electron density in the sun and exact solution -

Using an exact solution with the hyperbolic-tangent profile for the electron density in the sun, which is developed by Nötzold and later modified by Nakagawa, we have analyzed the solar neutrino problem. An interference term in their approach is correctly taken into account. Combining the hyperbolic-tangent profile with the BP2000, we obtain a phenomenological fitting in the analytic form. Combining recent observed results for survival probability $P(ν_e \to ν_e)$ by the SNO, SK, SAGE, Gallex, GNO and Homestake Collaborations, we obtain a large mixing angle (LMA) whose figure is looking like a shoulder.

hep-ph↗
arXiv1995

Wavelet Spectra of JACEE Events

Pseudo-rapidity distributions of two high multiplicity events Ca-C and Si-AgBr observed by the JACEE are analysed by the wavelet transform. Wavelet spectra of those events are calculated and compared with the simulation calculations. The wavelet spectrum of Ca-C event somewhat resembles to that simulated with the uniform random numbers. That of Si-AgBr event is not reproduced by simulation calculations with Poisson random numbers, uniform random numbers, or a p-model.

hep-ph↗