119258320
Supersymmetric Higgs-portal and X-ray lines
Abstract We consider a Dirac singlet fermion as thermal dark matter for explaining the X-ray line in the context of a supersymmetric Higgs-portal model or a generalized Dirac NMSSM. The Dirac singlet fermion gets a mass splitting due to their Yukawa couplings to two Higgs doublets and their superpartners, Higgsinos, after electroweak symmetry breaking. We show that a correct relic density can be obtained from thermal freeze-out, due to the co-annihilation with Higgsinos for the same Yukawa couplings. We discuss the phenomenology of the Higgsinos in this model such as displaced vertices at the LHC.
14332037
Mass and Spin Measurement with M(T2) and MAOS Momentum
We discuss the M T 2 -kink method to determine the masses of both the dark matter WIMP and its mother particle produced at the LHC. We then introduce a new kinematic variable, the M T 2 -Assisted-On-Shell (MAOS) momentum, that provides a systematic approximation to the invisible particle momenta in hadron collider events producing a pair of invisible particles, and apply it to certain SUSY processes and their UED equivalents to determine the spin of gluino/KK-gluon and of slepton/KK-lepton. An application of the MAOS momentum to the SM Higgs mass measurement is briefly discussed also.
119286463
Peccei-Quinn NMSSM in the light of 125 GeV Higgs
A bstractWe study the phenomenology of the Peccei-Quinn invariant extension of the next-to-minimal supersymmetric standard model (NMSSM) in view of the recent discovery of a 125 GeV Higgs boson. The minimal model having no quadratic and cubic terms of the NMSSM singlet field predicts a light singlino-like lightest supersymmetric particle (LSP). The model is strongly constrained by the Higgs invisible decay and the dark matter characteristic of the LSP, while some constraints can be relaxed by assuming that the saxion, the CP-even companion of the axion in the Peccei-Quinn sector, causes a late-time entropy production diluting the thermal LSP density. The collider signal of the model contains multi-jet and h/W/Z plus missing energy, which can be discovered in the early stage of the 14 TeV LHC running.
119231164
Reconstructing the heavy resonance at hadron colliders
We investigate the method for constructing the invariant mass using the M{sub T2}-assisted on-shell (MAOS) approximation to the invisible particle momenta in the cascade decays of a new particle resonance produced at hadron colliders. We note that the MAOS reconstruction can be defined in several different ways, while keeping the efficiency of approximation at a similar level, and one of them provides a unique solution for each event. It is shown that the invariant mass distribution constructed with the MAOS momenta exhibits a peak at the heavy resonance mass, regardless of the chosen MAOS scheme and the detailed mass spectrum of the particles in the cascade. We stress that the MAOS invariant mass can be used as a clean signal of new particle resonance produced at the Large Hadron Collider, as well as a model-independent method to measure the masses of new particles involved in the event.
55429027
Sparticle masses from transverse mass kinks at the LHC: the case of Yukawa-unified SUSY GUTs
We explore, in a concrete example, to which extent new particle mass determinations are practicable with LHC data. Our chosen example is that of Yukawa-unified SUSY GUTs, whose viability has been recently studied for two general patterns of soft SUSY-breaking terms. We note that both patterns of SUSY spectra do not admit long decay chains, which would make it possible to determine the masses of the SUSY particles involved using endpoints or mass relations. We thus take the so-called mT2-kink method as our key strategy, since it does not rely on the presence of long decay chains. We then discuss a procedure allowing to determine the masses of the gluino, of the lightest chargino as well as of the first two neutralinos and, for the scenario where a stop is lighter than the gluino, the mass of the light stop too. Our worked example of Yukawa-unified SUSY GUTs may offer a useful playground for dealing with other theories which predict similar patterns of SUSY spectra.
119163667
MT2-reconstructed invisible momenta as spin analizers, and an application to top polarization
A bstractFull event reconstruction is known to be challenging in cases with more than one undetected final-state particle, such as pair production of two states each decaying semi-invisibly. On the other hand, full event reconstruction would allow to access angular distributions sensitive to the spin fractions of the decaying particles, thereby dissecting their production mechanism. We explore this possibility in the case of Standard-Model $ t\overline{t} $ production followed by a leptonic decay of both W bosons, implying two undetected final-state neutrinos. We estimate the t and $ \overline{t} $ momentum vectors event by event using information extracted from the kinematic variable MT2. The faithfulness of the estimated momenta to the true momenta is then tested in observables sensitive to top polarization and $ t\overline{t} $ spin correlations. Our method thereby provides a novel approach towards the evaluation of these observables, and towards testing $ t\overline{t} $ production beyond the level of the total cross section. While our discussion is confined to $ t\overline{t} $ production as a benchmark, the method is applicable to any process whose decay topology allows to construct MT2.
204002512
a Search for Strange B Meson in UPSILON(5S) Decay