Ken-ichi Hikasa

Note on QCD corrections to hadronic Higgs decay

Abstract The O( α s ) QCD correction to the hadronic decay of a scalar Higgs boson, for which contradicting results have been reported, is calculated. Our result is in agreement with that of Braaten and Leveille but disagrees with that of Janot. The possible origin of the discrepancy is discussed. The total hadronic decay rate and the differential rate to q q ¯ g of a pseudoscalar Higgs boson are also presented.

Scalar top production in e+ e- annihilation

Abstract We discuss the pair production of light scalar top quarks in e + e − annihilation. The lighter mass eigenstate t 1 is a mixture of SU(2) doublet and singlet t states and can have a vanishing coupling to the Z boson. We show that the present data on the total decay width of the Z 0 can put a bound on the t 1 mass for some values of the mixing angle, but even existing dedicated search for squarks leaves a large portion of the parameter space unconstrained. We include both initial-state QED and final-state QCD corrections in our results for the cross section; even quite far away from the threshold the total corrections can lie between −15% and +70%.

A limit on massive neutrino dark matter from Kamiokande

Abstract We have searched for possible high-energy neutrino signals expected from massive neutrino dark matter captured by the earth and the sun, by making use of upward-going muon samples collected in the seven years of operation of the Kamiokande detector. No excess of events was found from the earth or the sun, thus giving an excluded mass range of Dirac-(Majorana-) type neutrinos, 6 (24) ⩽ m ν ⩽ several hundred GeV, as the dark matter which consitutes the halo of the galaxy. The upper bounds extend to a mass range never before analyzed in previous indirect searches.

Strongly interacting WW sector with a scalar resonance

Abstract We construct unitary partial-wave amplitudes for longitudinal WW scattering from general requirements of scalar dominance and the low-energy theorem of broken chiral symmetry. The amplitude is uniquely determined by specifying the mass of the scalar particle. For small masses, the amplitude in the minimal standard model is reproduced. For small masses above 1 TeV, the amplitude shows saturation behavior above the mass, and the scattering cross section is a few times larger than the extrapolation of the low-energy theorem.

Particle Physics Implications of the “Neutrino” Burst from the LMC Supernova

Three high energy events in the neutrino burst observed by Kamiokande II are interpreted to be caused by the arrival of SUSY particles, the photino or the scalar neutrino, with a mass of ~ 30 e V. Shortly after the discovery of the supernova explosion!) (SN1987 A) in the Large Magellanic Cloud (LMC) it was reported 2 ) by th~ Kamiokande II Collaboration that a neutrino burst preceded many hours before the optical brightening. A global feature of the twelve neutrino-like events reported there, their average energy of ~15 MeV, event rate and time span of several seconds, roughly agrees with what is expected 3 ) in a Type II supernova explosion, in which an inner core of about one solar mass (1.4 Me) gravitationally collapses and binding energy of ~ 3 X 10 53 erg is released.