1. Measuring masses of semi-invisible decays
W mass measurement at Tevatron uses transverse mass:
Where
All events have mT < mW
(If W on-mass shell)
mT is an event-by-event lower limit on mW
Use to measure mW
Neutrino mass known to be small.
No issue as to what to use for it’s mass

2. SUSY case For SUSY we have pairs of decays, e.g.
Don’t know PT of invisibles individually
Define:
“Split missing transverse momentum in all possible ways consistent with observed ptmiss. Find best lower limit on parent mass”
NB – need to input the LSP mass – which we don’t know

3. Use to measure parent mass
(Input) LSP mass 100
(Output)
slepton mass
300
Slepton pair  lepton, lepton, MET
Plot mT2 with “true” LSP mass

4. Dependence on LSP mass?
“Not the end of the world if you don’t know mass of LSP well”

5. Measuring WIMP mass
arXiv: v2

6. Their plots…
Kink in mT2 max value as a function of chi at LSP mass  information on LSP mass

7. Analysis
Ben Gripaios
Shows that the events which are at the edge of the mT distribution are different if we guess the LSP mass above vs below the true value Shows that the gradient of the edge has a kink at m_LSP

8. In pictures…
2-d distributions only show kinks if initial state very boosted in lab frame

9. 3-body decay (gluinos)
Now extra extremum exisits at finite initial state energy
More work in progress…