Chiral gauge leptoquark mass limits and branching ratios of KL0,B0,Bs → li+lj− decays with account of the general fermion mixing in leptoquark currents

The contributions of the chiral gauge leptoquarks [Formula: see text] induced by the chiral four-color quark–lepton symmetry to the branching ratios of [Formula: see text] decays are calculated and analyzed using the general parametrizations of the fermion mixing matrices in the leptoquark currents. From the current experimental data on these decays under assumption [Formula: see text], the lower mass limit [Formula: see text] is found, which in particular case of equal gauge coupling constants gives [Formula: see text]. The branching ratios of the decays under consideration predicted by the chiral gauge leptoquarks are calculated and analyzed in dependence on the leptoquark masses and the mixing parameters. It has shown that in consistency with the current experimental data, these branching ratios for [Formula: see text] decays can be close to their experimental limits and those for [Formula: see text] decays can be of order of [Formula: see text]. The calculated branching ratios will be useful in the further experimental searches for these decays.

Evolution of primordial black hole spin due to Hawking radiation

ABSTRACT Near extremal Kerr black holes (BHs) are subject to the Thorne limit $a\lt a^*_{\rm lim}=0.998$ in the case of thin disc accretion, or some generalized version of this in other disc geometries. However, any limit that differs from the thermodynamics limit a* < 1 can in principle be evaded in other astrophysical configurations, and in particular if the near extremal BHs are primordial and subject to evaporation by Hawking radiation only. We derive the lower mass limit above which Hawking radiation is slow enough so that a primordial black hole with a spin initially above some generalized Thorne limit can still be above this limit today. Thus, we point out that the observation of Kerr BHs with extremely high spin should be a hint of either exotic astrophysical mechanisms or primordial origin.

SEARCH FOR A HIGGS BOSON DECAYING INTO TWO PHOTONS WITH THE L3 DETECTOR AT LEP

A search is performed for a Higgs boson, decaying into two photons, using the L3 data collected at centre of mass energies between [Formula: see text] and 202 GeV, corresponding to an integrated luminosity of 400 pb -1. The processes [Formula: see text], [Formula: see text], e+e-→ Zh → ℓ+ℓ-γγ are considered. The observed data are found to be consistent with the expected background from standard physics processes. Limits on the branching fraction of the Higgs boson decay into two photons as a function of the Higgs mass are shown and a lower mass limit on a fermiophobic Higgs is derived.