Chan Beom Park

Measuring superparticle masses at hadron collider using the transverse mass kink

We present a detailed study of the collider observable mT2 applied for pair-produced superparticles decaying to visible particles and a pair of invisible lightest supersymmetric particles (LSPs). Analytic expressions of the maximum of mT2 over all events (mT2max) are derived. It is noticed that if the decay product of each superparticle involves more than one visible particle, mT2max being a function of the trial LSP mass mχ has a kink structure at mχ = true LSP mass, which can be used to determine the mother superparticle mass and the LSP mass simultaneously. To see how well mT2max can be constructed from collider data, a Monte-Carlo analysis of the gluino mT2 is performed for some superparticle spectra.

Transverse mass for pairs of gluinos.

We introduce a new observable, ’gluino stransverse mass’, which is an application of the Cambridge mT2 variable to the process where gluinos are pair produced in proton-proton collision and each gluino subsequently decays into two quarks and one LSP, i.e. g̃g̃ → qqχ̃01 qqχ̃ 0 1. We show that the gluino stransverse mass can be utilized to measure the gluino mass and the lightest neutralino mass separately, and also the 1st and 2nd generation squark masses if squarks are lighter than gluino, thereby providing a good first look at the pattern of sparticle masses experimentally.

M(T2)-assisted on-shell reconstruction of missing momenta and its application to spin measurement at the LHC

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{sub T2}, 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{sub T2}-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 good knowledge of the new particle masses.

LHC signature of mirage mediation

We study LHC phenomenology of mirage mediation scenario in which anomaly and modulus contributions to soft SUSY breaking terms are comparable to each other. A Monte Carlo study of mirage mediation, with model parameters α = 1, M0 = 500 GeV, nM = 1/2, nH = 1 and tan β = 10, is presented. It is shown that masses of supersymmetric particles can be measured in a model independent way, providing information on SUSY breaking sector. In particular, the mass ratio of gluino to the lightest neutralino for the benchmark scenario is determined to be 1.9 m/m10 3.1, well reproducing theoretical input value of m/m10 2.5 which is quite distinctive from the predictions m/m10 6 of other SUSY scenarios in which gaugino masses are unified at the GUT scale. The model parameters of mirage mediation can be also determined from various kinematic distributions.

Reconstructing the Higgs boson in dileptonic W decays at hadron colliders

We examine the prospect to measure the Higgs boson mass using the recently introduced kinematic variable, the

Measuring the top quark mass with m_T2 at the LHC

{M}_{T2}

Measuring the top quark mass with m(T2) at the LHC

-assisted on-shell (MAOS) momentum, that provides a systematic approximation to the invisible neutrino momenta in dileptonic decays of a

Mass and Spin Measurement with M(T2) and MAOS Momentum

W

Measuring the top quark mass with the m(T2) variable

-boson pair. For this purpose, we introduce a modified version of the MAOS momentum that is applicable even when one or both of the

Measuring the top quark mass with the m{sub T2} variable

W