arXiv subjects

T. Osada

Publications and source records attributed to T. Osada.

25 records · Page 2Linked to original sources

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

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

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↗

arXiv1995

Coulomb corrections for Bose-Einstein correlations in whole momentum transfer region: Proposal of seamless fitting

We applied an improved Coulomb correction method developed by us recently to data on identical KK-pairs production in S + Pb and p + Pb reactions at 200 GeV/c obtained by NA44 Collaboration. To analyse the whole range of the momentum transfers measured the method of "seamless fitting" has been proposed and used together with the asymptotic expansion formula for the Coulomb wave function. We found that such Coulomb corrections lead sometimes to different than previously reported (by NA44 Collaboration) interaction region and strongly influence the long range correlations.

hep-ph↗

arXiv1995

Improved Coulomb Correction Formulae for Bose-Einstein Correlations

We present improved Coulomb correction formulae for Bose-Einstein correlations including also exchange term and use them to calculate appropriate correction factors for several source functions. It is found that Coulomb correction to the exchange function in the Bose-Einstein correlations cannot be neglected.

hep-ph↗