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Register a new userFluctuations and Fermi-Dirac Correlations in e+e- annihilation
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Gosta Gustafson
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In this talk I first present a short review of fluctuations in $e^+e^-$-annihilations. I then describe some new results on FD correlations. Experimental analyses of $pp$ and $LambdaLambda$ correlations indicate a very small production radius. This result relies very strongly on comparisons with MC simulations. A study of the approximations and uncertainties is these simulations imply that it is premature to draw such a conclusion from the data.
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Results on Bose-Einstein correlations in e+e- ==> hadrons are reviewed.
We present the full O(alpha_s) longitudinal spin-spin correlations for heavy-quark pair production at e+ e- high-energy colliders in closed analytical form. In such reactions, quark and antiquark have strongly correlated spins, and the longitudinal components are dominant. For the explicit computation of the QCD bremsstrahlung contributions, new phase-space integrals are derived. Explicit numerical estimates are given for t t_bar and b b_bar production. Around the Z-peak, QCD one-loop corrections depolarize the spin-spin asymmetry for bottom quark pairs by approximately -4%. For top pair production, we find at 350GeV a 0.6% increased polarization over a value of 0.4 in the longitudinal correlation. For more than 1 TeV the O(alpha_s) corrections enhance depolarization to -2% in the top-pair case.
We examine the processes $e^+ e^-longrightarrow W^+ W^-$ and $Z^0 Z^0$ in the context of the $SP(6)_Lotimes U(1)_Y$ model. We find that there are significant deviations in the total cross sections $sigma (s)$ from the standard model results due to the presence of additional gauge bosons $Z^prime$ and $W^prime$ in the model. These deviations could be detected at LEP.
Bose-Einstein correlations of pairs of identical charged pions produced in hadronic Z decays are analyzed for both two- and three-jet events. A parametrization suggested by the tau-model is used to investigate the dependence of the Bose-Einstein correlation function on track multiplicity, number of jets, and transverse momentum.
We study, at leading order in the large number of colours expansion and within the Resonance Chiral Theory framework, the odd-intrinsic-parity $e^+ e^- rightarrow pi^+ pi^- (pi^0, eta)$ cross-sections in the energy regime populated by hadron resonances, namely $3 , m_{pi} lsim E lsim 2 , mbox{GeV}$. In addition we implement our results in the Monte Carlo generator PHOKHARA 7.0 and we simulate hadron production through the radiative return method.
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