MT2-assisted on-shell reconstruction of missing momenta and its application to spin measurement at the LHC

Abstract

We propose a scheme to assign a 4-momentum to each WIMP in new physics event producing a pair of mother particles each of which decays to an invisible weakly interacting massive particle (WIMP) plus some visible particle(s). The transverse components are given by the value that determines the event variable M T 2 , while the longitudinal component is determined by the on-shell condition on the mother particle. Although it does not give the true WIMP momentum in general, this M T 2 -assisted on-shell reconstruction of missing momenta provides kinematic variables well correlated to the true WIMP momentum, and thus can be useful for an experimental determination of new particle properties. We apply this scheme to some processes to measure the mother particle spin, and find that spin determination is possible even without a good knowledge of the new particle masses. PACS numbers:1 The Large Hadron Collider (LHC) at CERN will explore soon the TeV energy scale where new physics beyond the Standard Model (SM) is likely to reveal itself. There are two major motivations for new physics at the TeV scale, one is the hierarchy problem and the other

Probing the two light Higgs scenario in the NMSSM with a low-mass pseudoscalar

“…We impose a cut, requiring the invariant mass to be larger than 40 GeV, which accommodates to the possible spread of the invariant mass distribution. Another possible collider variable is the invariant mass reconstructed by the M T2 -assisted on-shell approximation of the invisible momenta [95], which has been found to be useful for reconstructing the resonance mass peak in the similar decay topology [96]. However, by definition, we would need to sacrifice a certain signal statistics by imposing a strong M T2 cut to attain a good accuracy.…”

Resonant Higgs boson pair production in the h h → b b ¯ W W → b b ¯ ℓ + ν ℓ − ν ¯ $$ hh\to b\overline{b}\ WW\to b\overline{b}{\ell}^{+}\nu {\ell}^{-}\overline{\nu} $$ decay channel

“…Then, by adopting the M T2 solution of the invisible transverse momenta in conjunction with known on-shell mass relations, one can calculate the longitudinal and energy components of the invisible four-momenta. This is so-called M T2 -assisted on-shell (MAOS) approximation scheme [85]. One drawback of this scheme is that it cannot be applied if any of the parent particles are off-shell.…”

Identifying the production process of new physics at colliders; symmetric or asymmetric?

“…The reason is that the strict convexity makes the solution unique, and thus, the true momenta are the solution when the event have the µ p,2 value of saturated kinematic endpoint. Like M T 2 -assisted on-shell reconstruction [45][46][47], events near the saturated kinematic endpoint can be used for measuring the new particle properties.…”