A completely relativistic quark model in the Bethe-Salpter framework is employed to calculate the exclusive production ratio of the neutral over charged Kaon pair in $e^+e^-$ annihilation continuum region for center of mass energies smaller than the $J/Psi$ mass. The valence quark charge plays the key r^{o}le. The cancellation of the diagrams for the same charge case (in $K_S + K_L$) and the non-cancellation of the diagrams for the different charge case (in $K^-+K^+$) lead to the ratio as $(m_s-m_d)^2/M_{Kaon}^2 sim 1/10$.
A vector-dominance two-photon exchange model is proposed to explain the recently observed production of $rho^0rho^0$ and $rho^0phi$ pairs in $e^+e^-$ annihilation at 10.58 GeV with the BaBar detector. All the observed features of the data --angular a
nd decay distributions, rates-- are in agreement with the model. Predictions are made for yet-unobserved final states.
We compute the inclusive unpolarized dihadron production cross section in the far from back-to-back region of $e^+ e^-$ annihilation in leading order pQCD using existing fragmentation function fits and standard collinear factorization, focusing on th
e large transverse momentum region where transverse momentum is comparable to the hard scale (the center-of-mass energy). We compare with standard transverse-momentum-dependent (TMD) fragmentation function-based predictions intended for the small transverse momentum region with the aim of testing the expectation that the two types of calculation roughly coincide at intermediate transverse momentum. We find significant tension, within the intermediate transverse momentum region, between calculations done with existing non-perturbative TMD fragmentation functions and collinear factorization calculations if the center-of-mass energy is not extremely large. We argue that $e^+ e^-$ measurements are ideal for resolving this tension and exploring the large-to-small transverse momentum transition, given the typically larger hard scales ($gtrsim 10$ GeV) of the process as compared with similar scenarios that arise in semi-inclusive deep inelastic scattering and fixed-target Drell-Yan measurements.
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 th
e presence of additional gauge bosons $Z^prime$ and $W^prime$ in the model. These deviations could be detected at LEP.
We describe how to use ZFITTER, a program based on a semi-analytical approach to fermion pair production in e+e- annihilation and Bhabha scattering. A flexible treatment of complete ${cal O}(alpha)$ QED corrections, also including higher orders, allo
ws for three calculational {bf chains} with different realistic sets of restrictions in the photon phase space. {tt ZFITTER} consists of several {bf branches} with varying assumptions on the underlying hard scattering process. One includes complete ${cal O}(alpha)$ weak loop corrections with a resummation of leading higher-order terms. Alternatively, an ansatz inspired from S-matrix theory, or several model-independent effective Born cross sections may be convoluted. The program calculates cross sections, forward-backward asymmetries, and for $tau$~pair production also the final-state polarization. Various {bf interfaces} allow fits to be performed with different sets of free parameters.
We perform a systematic analysis of exclusive hadronic channels in e+e- collisions at centre-of-mass energies between 2.1 and 2.6 GeV within the statistical hadronization model. Because of the low multiplicities involved, calculations have been carri
ed out in the full microcanonical ensemble, including conservation of energy-momentum, angular momentum, parity, isospin, and all relevant charges. We show that the data is in an overall good agreement with the model for an energy density of about 0.5 GeV/fm^3 and an extra strangeness suppression parameter gamma_S ~ 0.7, essentially the same values found with fits to inclusive multiplicities at higher energy.
Yi Jin
,Shi-Yuan Li
,Yan-Rui Liu
.
(2019)
.
"Exclusive Production Ratio of Neutral over Charged Kaon Pair in $e^+e^-$ Annihilation Continuum via `Straton Model"
.
Shi-Yuan Li
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