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M. Biyajima

Publications and source records attributed to M. Biyajima.

At least 37 records · Page 2Linked to original sources
arXiv1999

Oscillations of Cumulant Moments - Universality of Amplitudes

We demonstrate on simple examples that oscillatory behaviour of moments of multiplicity distributions P(n) observed in e^+e^- annihilations, in hadronic pp collisions and in collisions on nuclei, p+A, is to a large extend caused by the experimental artifact of measuring only limited range of P(n). In particular we show that by applying a suitable universal cutt-off procedure to the measured P(n) one gets for reactions mentioned before oscillations of similar magnitude. The location of zeros of oscillations as a function of the rank of moments and their shapes remain, however, distinctively different for different types of reactions considered. This applies to some extend also to collisions of nuclei, which otherwise follow their own pattern of behaviour.

hep-ph↗
arXiv1999

Multiplicity dependence of identical particle correlations in the quantum optical approach

Identical particle correlations at fixed multiplicity are consideres in the presence of chaotic and coherent fields. The multiplicity distribution, one-particle momentum density, and two-particle correlation function are obtained based on the diagrammatic representation for cmulants in semi-inclusive events. Our formulation is applied to the analysis of the experimental data on the multiplicity dependence of correlation functions reported by the UA1 and the OPAL Collaborations.

hep-ph↗
arXiv1999

Analysis of correlation data of pi^+pi^- pair in p + Ta reaction using Coulomb wave function including momentum resolution and strong interaction effect

We have proposed a new method for the Coulomb wave function correction which includes the momentum resolution for charged hadron pairs and applied it to the precise data on pi^+pi^- correlations obtained in p + Ta reaction at 70 GeV/c. It is found that interaction regions of this reaction (assuming Gaussian source function) are 9.8+-5.8 fm and 7.7+-4.8 fm for the thicknesses of the target 8 micro m and 1.4 micro m, respectively. We have also analyzed the data by the formula including strong interaction effect. The physical picture of the source size obtained in this way is discussed.

nucl-th↗
arXiv1998

Analysis of Bose-Einstein correlations in e+e- -> W+W- events including final state interactions

Recently DELPHI Collaboration reported new data on Bose-Einstein correlations (BEC) measured in e+e- -> W^+W^- events. Apparently no enhancement has been observed. We have analyzed these data including final state interactions (FSI) of both Coulomb and strong (s-wave) origin and found that there is enhancement in BEC but it is overshadowed by the FSI which are extremely important for those events. We have found the following values for the size of the interaction range beta and the degree of coherence lambda: beta=0.87 +/- 0.31fm and lambda=1.19 +/- 0.48, respectively.

hep-ph↗
arXiv1998

Analyses of multiplicity distributions of e^+e^- and e-p collisions by means of modified negative binomial distribution and Laguerre-type distribution: Interrelation of solutions in stochastic processes

A pure birth stochastic process with several initial conditions is considered.We analyze multiplicity distributions of e^+e^- collisions and e-p collisions, usigthe Modified Negative Binomial Distribution (MNBD) and the Laguerre-type distribution. Several multiplicity distributions show the same minimum χ^2's values in analyses by means of two formulas: In these cases, we find that a parameter N contained in the MNBD becomes to be large. Taking large N limit in the MNBD, we find that the Laguerre-type distribution can be derived from it. Moreover, from the generalized MNBD we can also derive the generalized Glauber-Lachs formula. Finally stochastic properties of QCD and multiparticle dynamics are discussed.

hep-ph↗
arXiv1998

Analyses of multiplicity distributions by means of the Modified Negative Binomial Distribution and its KNO scaling function

We analyze various data of multiplicity distributions by means of the Modified Negative Binomial Distribution (MNBD) and its KNO scaling function, since this MNBD explains the oscillating behavior of the cumulant moment observed in e^+e^- annihilations, h-h collisions and e-p collisions. In the present analyses, we find that the MNBD(discrete distributions) describes the data of charged particles in e^+e^- annihilations much better than the Negative Binomial Distribution (NBD). To investigate stochastic property of the MNBD, we derive the KNO scaling function from the discrete distribution by using a straightforward method and the Poisson transform. It is a new KNO function expressed by the Laguerre polynomials. In analyses of the data by using the KNO scaling function, we find that the MNBD describes the data better than the gamma function.Thus, it can be said that the MNBD is one of useful formulas as well as NBD.

hep-ph↗
arXiv1997

Isotopic Spin Conservation Effect in Bose-Einstein Correlations

Bose-Einstein correlations of pions have been calculated in the presence of both statistical and coherent pion production with isotopic spin conservation taken into account.An additional contribution to pion correlation function has been found arising due to isospin effect

hep-ph↗
arXiv1997

Comparative Analysis of Multiplicity Distributions in Inelastic Processes for Different Colliding Particles and Nuclei

Theoretical prediction of oscillations of cumulant moments of parton multiplicity distributions inside a jet supported by experimental data in some multiple production processes asks for analysis of the phenomenon for the whole set of available reactions. We have found out that the oscillations persist in any kind of processes and increase for particles with more complicated structure i.e. in the order of ee, eh, hh, hA, AA. The effect is not strongly dependent on the available phase space. Theoretical values of moments for quark and gluon jets up to 5th rank are shown. Zeros of the truncated generating function and singularities of the total generating function are discussed.

hep-ph↗
arXiv1997

Final State Interactions in Bose-Einstein Correlations

We are presenting here the new formulae for Bose-Einstein correlations (BEC) which contain effects of final state interactions (FSI) of both strong (in $s$-wave) and electromagnetic origin. We demonstrate the importance of FSI in BEC by analysing data for $e^+e^-$ annihilation and for heavy collisions. The inclusion of FSI results in the practical elimination (at least in $e^+e^-$ data) of the so called degree of coherence parameter $λ$ (which becomes equal unity) and the long range parameter $γ$ (which is now equal zero).

hep-ph↗
arXiv1997

Wavelet Analyses of High Multiplicity Events

Pseudo-rapidity distributions of high multiplicity JACEE events ( Ca-C, Si-AgBr and G27) and Texas Lone Star (TLS) event are analysed by the wavelet transform method. Using the Daubechies' waveltes, $D_4, D_6, D_8,$ and $ D_{10} $, wavelet spectra of those events are calculated. Two JACEE events are compared with the simulation calculations. We discuss how to distinguish prominent peak from apparent peaks. The wavelet spectrum of Ca-C event seems to resemble that simulated with the Poisson random number distributions. The wavelet spectrum of TLS event shows an oscillatory behavior. It is found that the wavelet spectra of JACEE G27 event are different from those of Arizona group.

hep-ph↗
arXiv1997

Quasiscaling in the analysis of the yield ratio $π^-/π^+$: Mathematical structure and estimation of source size

Recently we have found that integral of the squared Coulomb wave function describing systemcomposed of charged pion and central charged fragment $Z_{eff}$ protons, $|ψ_r(r)|^2$, times pion source function $ρ(r)$ (of the size $β$), $\intdr |ψ_r(r)|^2 ρ(r)$, shows a quasiscaling behavior. This is approximately invariant under the following transformation: $(β,Z_{eff}) \to (λβ,λZ_{eff})$; $λ>0$. We called such behavior $β-Z_{eff}$ quasiscaling. We examine this quasiscaling behavior in detail. In particular we provide a semi-analytical examination of this behavior and confirm it for the exponential pionic source functions in addition to the Gaussian ones and for the production of K mesons as well. When combined with the results of the HBT, a result of the yield ratio allows us to estimate the size of the central charged fragment (CCF) to be $125\le Z_{eff}\le 150$ for Pb+Pb collisions at energy 158 GeV/nucleon. From our estimation, the baryon number density $0.024 \le n_{B}\le0.036$ [1/fm^3] is obtained.

hep-ph↗
arXiv1996

Charge Distribution in Soft Chiral Pion Bremsstrahlung

Bremsstrahlung of soft chiral pions in high-energy processes is considered. The distribution over number of neutral and charged pions is shown to obey the inverse square root law. This law is argued to be generic for multiple coherent production of soft chiral pions.

hep-ph↗
arXiv1996

KNO scaling function of modified negative binomial distribution

We investigate the KNO scaling function of the modified negative binomial distribution (MNBD), because this MNBD can explain the oscillating behaviors of the cumulant moment observed in $e^+e^-$ annihilations and in hadronic collisions. By using a straightforward method and the Poisson transform we derive the KNO scaling function from the MNBD. The KNO form of experimental data in $e^{+}e^{-}$ collisions and hadronic collisions are analyzed by the KNO scaling function of the MNBD and that of the negative binomial distribution (NBD). The KNO scaling function of the MNBD describes the data as well as that of the NBD.

hep-ph↗
arXiv1996

Final state interactions for Bose-Einstein correlations in S+Pb $\to$ $π^+$$π^+$ +X reaction at energy 200GeV/nucleon

We applied an analytical formula for Bose-Einstein correlations (BEC) developed by us recently to high-energy heavy ion collisions, in particular to data on S+Pb$\toπ^+$-$π^+$+X reaction at energy $200$ GeV/nucleon reported by the NA44 Collaboration. It takes into account both Coulomb and strong ($π$-$π$~s-wave; I=2) final state interactions (FSI). We have found that inclusion of the strong interaction in addition to Coulomb correction affects significantly the extracted parameters of the BEC like the source size $R$, the degree of coherence $λ$ and the long-range correlation parameter $γ$. In particular, the $λ$ parameter of the BEC is increased by about 20\%. Our results differ from those obtained in $e^+e^-$ annihilation in the following way: the $λ$ parameter does not reach `chaotic limit' and the $γ$ parameter does not approach to zero.

hep-ph↗
arXiv1996

Coulomb and strong interactions for Bose-Einstein correlations

We present an analytical formula for the Bose-Einstein correlations (BEC) which includes effects of both Coulomb and strong final stateinteractions (FSI). It was obtained by using Coulomb wave function together with the scattering partial wave amplitude of the strong interactions describing data on the $s$-wave phase shift. We have proved numerically that this method is equivalent to solving Schrödinger equation with Coulomb and the $s$-wave strong interaction potentials. As an application we have analysed, using our formula which includes the degree of coherence and the long range correlation, the data for $e^+e^-$ annihilations. We have found that the degree of coherence present in our formula approaches approximately unity whereas the long range correlation parameter becomes approximately zero. These results suggest that the physical meanings of the fractional degree of coherence and the long range correlation observed in various other analyses can most probably be attributed to FSI.

hep-ph↗
arXiv1996

What information can we obtain from the yield ratio $π^-/π^+$ in heavy-ion collisions ?

The recently reported data on the yield ratio $π^-/π^+$ in central rapidity region of heavy-ion collisions are analyzed by theoretical formula which accounts for Coulomb interaction between central charged fragment (CCF) consisting of nearly stopped nucleons with effective charge $Z_{\mbox{\scriptsize eff}}$ and charged pions produced in the same region of the phase space. The Coulomb wave function method is used instead of the usual Gamow factor in order to account for the finite production range of pions, $β$. For Gaussian shape of the pion production sources it results in a quasi-scaling in $β$ and $Z_{\mbox{\scriptsize eff}}$ which makes determination of parameters $β$ and $Z_{\mbox{\scriptsize eff}}$ from the existing experimental data difficult. Only sufficiently accurate data taken in the extreme small $m_{\scriptscriptstyle T}$-$m_π$ region, where this quasi-scaling is broken, could be used for this purpose.

hep-ph↗
arXiv1996

Analysis of Cumulant Moments in High Energy Hadron-Hadron Collisions by Truncated Multiplicity Distributions

Oscillatory behavior of cumulant moments obtained from the experimental data in $pp$ collisions and $\bar{p}p$ collisions are analyzed by the modified negative binomial distribution (MNBD) and the negative binomial distribution (NBD). Both distributions well describe the cumulant moments obtained from the data. This fact shows sharp contrast to the result in $e^+e^-$ collisions, which is described by the the MNBD much better than by the NBD.

hep-ph↗