The calculation of the ionization probability and of the ionization coefficients of the holes of the spin split-off valence band in Ga1- x Al x Sb has been made for various compositions 0<x<0.08. This range allows us to obtain the situations in which the ratio of spin orbit splitting Δ to the energy gap E g decreases from 1.05 to 0.89. It is shown that if the alloy disorder is neglected, the hole ionization coefficient k p exhibits a continuous variation with Δ/E g (or x); if not, k p is strongly increased and shows a maximum for x=0.02 in the composition range in which Δ≥E g (Δ/E g=1.006). The comparison with experimental results is presented and allows an estimation of the mean free path of the holes; the strong influence of this parameter on the k p values is discussed.

The validity of the determination of the ionization coefficients deduced from the experimental measurement of photocurrent multiplication Mph in GaAlSb diodes, in which the electric-field profile is nonlinear and successive pure hole and pure electron injections cannot be made, are compared and discussed. Three methods for determining ionization coefficients kp and kn are discussed: (i) adjusting kp and kn in order to fit the experimentally observed Mph values using an approximated linear electric field; (ii) the same method applied to a more realistic electric-field profile; (iii) the Grant method in which kp and kn are calculated from the results of multiplication measurements in the case of pure injections and using this last electric-field profile. It is concluded that when the condition of pure injection is not fulfilled the Grant method may lead to erroneous k values and the adjustment method is more valid.

Weak boson fusion is a copious source of intermediate mass Higgs bosons at the LHC, with a rate σB(H → γγ) of up to 9 fb. The additional very energetic forward jets in these events provide for a unique signature. A parton level analysis of the dominant backgrounds demonstrates that this channel allows the observation of H → γγ in a low background environment, with modest luminosity.