High Energy Physics, Cavendish Laboratory, University of Cambridge
Abstract
Considering the cascade decay D → cC → cbB → cbaA in which D,C,B,A are
massive particles and c, b, a are massless particles, we determine for the shape of the
distribution of the invariant mass of the three massless particles mabc for the sub-set
of decays in which the invariant mass mab of the last two particles in the chain is (optionally)
constrained to lie inside an arbitrary interval, mab ∈ [mcut min
ab ,mcut max
ab ].
An example of an experimentally important distribution of this kind is the “mqll
threshold” – which is the distribution of the combined invariant mass of the visible
standard model particles radiated from the hypothesised decay of a squark to
the lightest neutralino via successive two body decay,: ˜q → q ˜ 02
→ ql˜l → qll ˜ 01
, in
which the experimenter requires additionally that mll be greater than mmax
ll /√2.
The location of the “foot” of this distribution is often used to constrain sparticle
mass scales. The new results presented here permit the location of this foot to be
better understood as the shape of the distribution is derived. The effects of varying
the position of the mll cut(s) may now be seen more easily