Transverse masses and kinematic constraints: from the boundary to the crease
Abstract
We reexamine the kinematic variable m_{T2} and its relatives in the light of recent work by Cheng and Han. Their proof that m_{T2} admits an equivalent, but implicit, definition as the `boundary of the region of parent and daughter masses that is kinematically consistent with the event hypothesis' is farreaching in its consequences. We generalize their result both to simpler cases (m_{T}, the transverse mass) and to more complex cases (m_{TGen}). We further note that it is possible to recast many existing and unpleasant proofs (e.g. those relating to the existence or properties of ``kink'' and ``crease'' structures in m_{T2}) into almost trivial forms by using the alternative definition. Not only does this allow us to gain better understanding of those existing results, but it also allows us to write down new (and more or less explicit) definitions of (a) the variable that naturally generalizes m_{T2} to the case in which the parent or daughter particles are not identical, and (b) the inverses of m_{T} and m_{T2} — which may be useful if daughter masses are known and bounds on parent masses are required. We note the implications that these results may have for future matrixelement likelihood techniques.
 Publication:

Journal of High Energy Physics
 Pub Date:
 November 2009
 DOI:
 10.1088/11266708/2009/11/096
 arXiv:
 arXiv:0908.3779
 Bibcode:
 2009JHEP...11..096B
 Keywords:

 High Energy Physics  Phenomenology
 EPrint:
 7 pages, 2 figures v2 has a modified introduction which attempts to explain more clearly both the mathematical purpose of and experimental limits to the analysis presented