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M. Biyajima

Publications and source records attributed to M. Biyajima.

At least 19 recordsLinked to original sources
arXiv2020

Multiplicity distribution in pseudo-rapidity windows and charge conservation

Charged multiplicity distribution in a pseudo-rapidity window is formulated under the assumption that the charge conservation is satisfied in the full phase space. At first, we analyze measured charged particle multiplicity distributions in pseudo-rapidity windows in LHC by CMS and ALICE collaborations with the two probability distributions. One is the convolution of negative binomial and Poisson distributions, and the other is the Glauber-Lachs formula. Each distribution is considered as an analogy of the quantum optics. Next, we analyze the data with the double GL formulae for $|η|<2.4$ at 7 TeV by the CMS collaboration and for $|η|<1.5$ at 8 TeV by the ALICE collaboration to describe the global structure of measured distributions.

hep-ph↗
arXiv2013

Analysis of Bose-Einstein correlations at fixed multiplicities in TeV energy $pp$ collisions in the quantum optical approach

The multiplicity distribution and the two-particle Bose-Einstein correlations at fixed multiplicities observed in $pp$ collisions at $\sqrt{s}=7$ TeV by the ALICE Collaboration are analyzed by the formulae obtained in the quantum optical approach. The chaoticity parameters in the inclusive and semi-inclusive events are estimated from the analysis. Multiplicity or $k_T$ dependence of longitudinal and transverse source radii are also estimated.

hep-ph↗
arXiv2009

A potential including Heaviside function in 1+1 dimensional hydrodynamics by Landau

In 1+1 dimensional hydrodynamics originally proposed by Landau, we derive a new potential and distribution function including Heaviside function and investigate its mathematical and physical properties. Using the original distribution derived by Landau, a distribution function found by Srivastava et al., our distribution function, and the Gaussian distribution proposed by Carruthers et al., we analyze the data of the rapidity distribution on charged pions and K mesons at RHIC energies (sqrt(s_NN) = 62.4 GeV and 200 GeV). Three distributions derived from the hydrodynamics show almost the same chi-squared values provided the CERN MINUIT is used. We know that our calculations of hadron's distribution do not strongly depend on the range of integration of fluid rapidity, contrary to that of Srivastava et al. Finally the roles of the Heaviside function in concrete analyses of data are investigated.

hep-ph↗
arXiv2006

Modified Hagedorn formula including temperature fluctuation - Estimation of temperatures at RHIC experiments -

We have systematically estimated the possible temperatures obtained from an analysis of recent data on $p_t$ distributions observed at RHIC experiments. Using the fact that observed $p_t$ distributions cannot be described by the original Hagedorn formula in the whole range of transverse momenta (in particular above 6 GeV/c), we propose a modified Hagedorn formula including temperature fluctuation. We show that by using it we can fit $p_t$ distributions in the whole range and can estimate consistently the relevant temperatures, including their fluctuations.

hep-ph↗
arXiv2005

Local thermalization in d + Au collisions

The extent of a locally equilibrated parton plasma in d + Au collisions at sqrt(s_NN) = 200 GeV is investigated as a function of 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 19% of the produced particles.

hep-ph↗
arXiv2005

Transverse momentum distribution with radial flow in relativistic diffusion model

Large transverse momentum distributions of identified particles observed at RHIC are analyzed by a relativistic stochastic model in the three dimensional (non-Euclidean) rapidity space. A distribution function obtained from the model is Gaussian-like in radial rapidity. It can well describe observed transverse momentum $p_T$ distributions. Estimation of radial flow is made from the analysis of $p_T$ distributions for $\bar{p}$ in Au + Au Collisions. Temperatures are estimated from observed large $p_T$ distributions under the assumption that the distribution function approaches to the Maxwell-Boltzmann distribution in the lower momentum limit. Power-law behavior of large $p_T$ distribution is also derived from the model.

hep-ph↗
arXiv2004

Analyses of two and three pion Bose-Einstein Correlations using Coulomb wave functions

Using effective formulas we analyze the Bose-Einstein correlations (BEC) data corrected for Coulomb interactions provided by STAR Collaboration and the quasi-corrected data (raw data with acceptance correction etc) on 2πand 3πBEC by using Coulomb wave function with coherence parameter included. The corresponding magnitudes of the interaction regions turn out to be almost the same: R_{Coul}(2π) \simeq \frac 32R_{Coul}(3π). R_{Coul} means the size of interaction region obtained in terms of Coulomb wave function. This approximate relation is also confirmed by the core-halo model. Moreover, the genuine 3rd order term of BEC has also been investigated in this framework and its magnitude has been estimated both in the fully corrected data and in the quasi-corrected data.

nucl-th↗
arXiv2004

Analysis of distribution of cosmic microwave background photon in terms of non-extensive statistics and formulas with temperature fluctuation

To take into account the temperature fluctuation in the Planck distribution, we calculate convolution integral with several probability distributions. Using these formula as well the Planck distribution and a formula in the non-extensive statistics, we analyze the data measured by the Cosmic Background Explorer (COBE). Our analysis reveals that the derivation from the Planck distribution is estimated as |q-1| = 4.4\times 10^{-5}, where q means the magnitude of the non-extensivity or the temperature fluctuation, provided that the dimensionless chemical potential proposed by Zeldovich and Sunyaev exists. Comparisons of new formulas and the Planck distribution including the Sunyaev-Zeldovich (S-Z) effect are made.

cond-mat.stat-mech↗
arXiv2003

Possible formulations for three-charged particles correlations in terms of Coulomb wave functions

The recent data for Bose-Einstein Correlations (BEC) of three-charged particles obtained by NA44 Collaboration have been analysed using theoretical formula with Coulomb wave functions. It has been recently proposed by Alt et al. It turns out that there are discrepancies between these data and the respective theoretical values. To resolve this problem we seek a possibly modified theoretical formulation of this problem by introducing the degree of coherence for the exchange effect due to the BEC between two-identical bosons. As a result we obtain a modified formulation for the BEC of three-charged particles showing good agreement with the data. Moreover, we investigate physical connection between our modified formulation and the core-halo model proposed by Csorgo et al. Our study indicates that the interaction region estimated by the BEC of three-charged particles in the S + Pb collisions at 200 GeV/c per nucleon is equal to about 1.5 fm~1.8 fm.

hep-ph↗
arXiv2003

A formulation for description of pi^+(2pi^-) and pi^-(2pi^+) channels in Bose-Einstein correlation by Coulomb wave function

In order to analyze data on charged pions correlation channels, pi^+(2pi^-) and pi^-(2pi^+), we propose new interferometry approach using the Coulomb wave function. We show that to describe adequately data we have to introduce new parameter describing the contribution of pi^-(k_1) pi^+(k_2) --> pi^-(k_2) pi^+(k_1) process. Using this new formula we analyze data on pi^+(2pi^-) and pi^-(2pi^+) channels at sqrt(s) = 91 GeV by DELPHI Collaboration, and estimate the magnitude of this new parameter as well as the degree of coherence.

hep-ph↗
arXiv2003

Analyses of $dN_{ch}/dη$ and $dN_{ch}/dy$ distributions of BRAHMS Collaboration by means of the Ornstein-Uhlenbeck process

Interesting data on $dN_{\rm ch}/dη$ in Au-Au collisions ($η=-\ln \tan (θ/2)$) with the centrality cuts have been reported by BRAHMS Collaboration. Using the total multiplicity $N_{\rm ch} = \int (dN_{\rm ch}/dη)dη$, we find that there are scaling phenomena among $(N_{\rm ch})^{-1}dN_{\rm ch}/dη= dn/dη$ with different centrality cuts at $\sqrt{s_{NN}} =$ 130 GeV and 200 GeV, respectively. To explain these scaling behaviors of $dn/dη$, we consider the stochastic approach named the Ornstein-Uhlenbeck process with two sources. The following Fokker-Planck equation is adopted for the present analyses, $$ \frac{\partial P(x,t)}{\partial t} = γ[\frac{\partial}{\partial x}x + \frac 12\frac{σ^2}γ\frac{\partial^2}{\partial x^2}] P(x, t) $$ where $x$ means the rapidity (y) or pseudo-rapidity ($η$). $t$, $γ$ and $σ^2$ are the evolution parameter, the frictional coefficient and the variance, respectively. Introducing a variable of $z_r = η/η_{\rm rms}$ ($η_{\rm rms}=\sqrt{< η^2 >}$) we explain the $dn/d z_r$ distributions in the present approach. Moreover, to explain the rapidity (y) distributions from $η$ distributions at 200 GeV, we have derived the formula as $$ \frac{dn}{dy}=J^{-1}\frac{dn}{d η}, $$ where $J^{-1}=\sqrt{M(1+\sinh^2 y)}/\sqrt{1+M\sinh^2 y}$ with $M = 1 + (m/p_{\rm t})^2$. Their data of pion and all hadrons are fairly well explained by the O-U process. To compare our approach with another one, a phenomenological formula by Eskola et al. is also used in calculations of $dn/dη$.

nucl-th↗
arXiv2002

Scaling Behavior of $(N_{ch})^{-1}dN_{ch}/dη$ at $\sqrt{s_{NN}} = 130$ GeV by the PHOBOS Collaboration and Its Implication --A Possible Explanation Employing the Ornstein-Uhlenbeck Process--

Recently, interesting data concerning $dN_{ch}/dη$ in Au-Au collisions [$η=-\ln \tan (θ/2)$] with centrality cuts have been reported from the PHOBOS Collaboration. In most treatment these data are divided by the number of participants (nucleons) in collisions. Instead of this method, we use the total multiplicity $N_{ch} = \int (dN_{ch}/dη)dη$ and find that there is scaling phenomenon among $(N_{ch})^{-1}dN_{ch}/dη= dn/dη$ with different centrality cuts at $\sqrt{s_{NN}} = 130$ GeV. To explain this scaling behavior of $dn/dη$, we employ a stochastic approach using the Ornstein-Uhlenbeck process with two sources. A Langevin equation is adopted for this explanation. Moreover, comparisons of $dn/dη$ at $\sqrt{s_{NN}} = 130$ GeV with that at $\sqrt{s_{NN}} = 200$ GeV are made, and no significant difference is found. A possible method fot the detection of the quark-gluon plasma (QGP) through $dN_{ch}/dη$ is presented.

nucl-th↗
arXiv2001

Scaling behavior of $(N_{ch})^{-1}dN_{ch}/dη$ at $\sqrt{s_{NN}} = 130$ GeV by PHOBOS Collaboration and its analyses in terms of stochastic approach

Recently interesting data on $dN_{ch}/dη$ in Au-Au collisions ($η=-\ln \tan (θ/2)$) with the centrality cuts have been reported by PHOBOS Collaboration. Their data are usually divided by the number of participants (nucleons) in collisions. Instead of this way, using the total multiplicity $N_{ch} = \int (dN_{ch}/dη)dη$, we find that there is scaling phenomenon among $(N_{ch})^{-1}dN_{ch}/dη= dn/dη$ with different centrality cuts at $\sqrt{s_{NN}} = 130$ GeV. To explain this scaling behavior of $dn/dη$, we consider the stochastic approach called the Ornstein-Uhlenbeck process with two sources. Moreover, comparisons of $dn/dη$ at $\sqrt{s_{NN}} = 130$ GeV with that at $\sqrt{s_{NN}} = 200$ GeV have been made. A possible detection method of the quark-gluon plasma (QGP) thorough $dn/dη$ is presented.

hep-ph↗
arXiv2001

Analyses of multiplicity distributions at Tevatron by a two-component stochastic model --- No leading particle effect in E735 Experiment ---

Comparisons of multiplicity distributions at sqrt(s) = 1.8 TeV (E735 Experiment and CDF Collaboration) with our predictions by a two-component stochastic model have been made. This stochastic model is described by the pure-birth and Poisson processes. It is found that there are discrepancies among data at the CERN Sp-bar-pS collider and those at the Tevatron collider. The latter data by E735 do not contain the leading particle effect described by the Poisson process, providing that the view of the two-component stochastic model is correct. The data by CDF contain small leading particle effect. The reason is probably attributed to the correction made by E735, which is necessary to make the data of the full phase space from the restricted rapidity |eta|<3.25.

hep-ph↗
arXiv2001

Fractional Fokker-Planck Equation and Oscillatory Behavior of Cumulant Moments

The Fokker-Planck equation is considered, which is connected to the birth and death process with immigration by the Poisson transform. The fractional derivative in time variable is introduced into the Fokker-Planck equation. From its solution (the probability density function), the generating function (GF) for the corresponding probability distribution is derived. We consider the case when the GF reduces to that of the negative binomial distribution (NBD), if the fractional derivative is replaced to the ordinary one. Formulas of the factorial moment and the $H_j$ moment are derived from the GF. The $H_j$ moment derived from the GF of the NBD decreases monotonously as the rank j increases. However, the $H_j$ moment derived in our approach oscillates, which is contrasted with the case of the NBD. Calculated $H_j$ moments are compared with those given from the data in $p\bar{p}$ collisions and in $e^+e^-$ collisions.

hep-ph↗
arXiv2001

Fractional Fokker-Planck Equation in Time Variable and Oscillation of Cumulant Moments

Fractional derivative in time variable is introduced into the Fokker-Planck equation of a population growth model. It's solution, the KNO scaling function, is transformed into the generating function for the multiplicity distribution. Formulas of the factorial moment and the $H_j$ moment are derived from the generating function, which reduces to that of the negative binomial distribution (NBD), if the fractional derivative is replaced to the ordinary one. In our approach, oscillation of $H_j$ moment appears contrary to the case of the NBD. Calculated $H_j$ moments are compared with those given from the data in $p\bar{p}$ collisions and in $e^+e^-$ collisions.

hep-ph↗