The mass-constraining variable M 2 , a (1 + 3)-dimensional natural successor of extremely popular M T 2 , possesses an array of rich features having the ability to use on-shell mass constraints in semi-invisible production at a hadron collider. In this work, we investigate the consequence of applying a heavy resonance mass-shell constraint in the context of a semi-invisible antler decay topology produced at the LHC. Our proposed variable, under additional constraint, develops a new kink solution at the true masses. This enables one to determine the invisible particle mass simultaneously with the parent particle mass from these events. We analyze in a way to measure this kink optimally, exploring the origin and the properties of such interesting characteristics. We also study the event reconstruction capability inferred from this new variable and find that the resulting momenta are unique and well correlated with true invisible particle momenta.

Mass variable Ŝ min and its variants [1,2] were constructed by minimising the parton level center of mass energy that is consistent with all inclusive measurements. They were proposed to have the ability to measure mass scale of new physics in a fully model independent way. In this work we relax the criteria by assuming the availability of partial informations of new physics events and thus constraining this mass variable even further. Starting with two different classes of production topology, i.e. antler and non-antler, we demonstrate the usefulness of these variables to constrain the unknown masses. This discussion is illustrated with different examples, from the standard model Higgs production and beyond standard model resonance productions leading to semi-invisible production. We also utilise these constrains to reconstruct the semi-invisible events with the momenta of invisible particles and thus improving the measurements to reveal the properties of new physics.

The ongoing perplexing scenario with no hints of new physics at the Large Hadron Collider can be elucidated amicably if the exotic particle spectrum in many of the well-motivated theoretical models possesses degenerate mass. We investigate the usefulness of different kinematic variables sensitive to the compressed mass region, and propose a search strategy considering a phenomenological supersymmetric scenario where the top squark undergoes a four-body decay due to its extremely narrow mass difference with the lightest supersymmetric particle. Considering a challenging but relatively clean dileptonic decay channel, we demonstrate that one can effectively restrain the significant background from the top quark, which provides a complementary approach to the present CMS analysis. With the new strategic approach the current limit can be extended to a phase-space region that was not explored before.

One of the most popular models that is known to be able to solve the lepton flavour universality violating charged (b → c) and neutral current (b → s) anomalies is the Leptoquark Model. However, collider searches for such leptoquarks till date are only restricted towards their scalar counterpart. In this work we examine the multijet + E T / collider signatures of a vector leptoquark (U 1 ) which has the potential to mediate both the charged and neutral current processes at tree level. From our collider analysis we derive the exclusion mass limits for the U 1 leptoquark at 95% C.L. at the current and future experiment of Large Hadron Collider. We also calculate the effect of such a leptoquark in B → π observables. These can be used as further benchmarks if a hint towards the presence of such a leptoquark is discovered.

Presence of nonholomorphic soft SUSY breaking terms is known to be a possibility in the popular setup of the Minimal Supersymmetric Standard Model (MSSM). It has been shown that such a scenario known as NonHolomorphic Supersymmetric Standard Model (NHSSM) could remain 'natural' (i.e., not fine-tuned) even in the presence of a rather heavy higgsino-like LSP. However, it turns out that distinguishing such a scenario from the MSSM is unlikely to be an easy task, in particular at the Large Hadron Collider (LHC). In a first study of such a scenario at colliders (LHC), we explore a possible way that focuses on the sbottom phenomenology. This exploits the usual tan β-dependence (enhancement) of the bottom Yukawa coupling but reinforced/altered in the presence of non-vanishing nonholomorphic soft trilinear parameter A b . For a given set of masses of the sbottom(s) and the light electroweakinos (LSP, lighter chargino etc.) which are known from experiments, the difference between the two scenarios could manifest itself via event rate in the 2b-jets + / E T final state, which could be characteristically different from its MSSM expectation. Impact on the phenomenology of the stops at the LHC is also touched upon.