Search

Abstract We study the prospect of heavy singlet neutrinos as a dark matter (DM) candidate within a neutrinophilic U(1) model, where the Standard Model (SM) is extended with a U(1) gauge symmetry, and neutrino mass and oscillation parameters are explained through an inverse see-saw mechanism. The lightest of the heavy neutrinos plays the role of the DM, while the newly introduced scalars and the extra gauge boson $$Z'$$ Z ′ act as mediators between the dark sector and the SM sector. We show the range of model parameters where this DM candidate can be accommodated in the Weakly Interacting Massive Particle (WIMP) or Feebly Interacting Massive Particle (FIMP) scenario. The observed DM relic density (DMRD) is achieved via the new gauge boson and singlet scalar portals in the WIMP scenario, whereas within the FIMP scenario, these two particles assume a distinct yet pivotal role in generating the observed DMRD.

The exotic decay modes of the already discovered 125-GeV scalar into a pair of light pseudoscalars are a good probe of those new physics scenarios where such pseudoscalars exist. Searches in the mass region where the pseudoscalar (A) is lighter than 62.5 GeV have yielded null findings so far. No search has yet examined mA>62.5 GeV where the cross section is suppressed by the off-shell pseudoscalar. We point out a possible enhancement of the sensitivity of probing hAA coupling in the context of a Type-X two Higgs doublet model. We focus on h→AA(⁎)→4τ, and select events with two same-sign τ-jets along with a pair of same-sign leptons. This enables much more effective background elimination than in the erstwhile proposed channels. Taking two values of the ττA coupling into account, we obtain limits on the hAA coupling that can be probed at 2σ and 3σ significance, for mA ranging up to 85 GeV. For mA

The proposal for a high-energy muon collider offers many opportunities in the search for physics beyond the Standard Model (BSM). The collider by construction is likely to be more sensitive to the muon-philic models, primarily motivated by the BSM explanation of muon (g−2) excess and quark flavor anomalies. In this work, we explore the potential of the proposed muon collider in the context of such models and focus on one such model that extends the Standard Model (SM) with a leptoquark, a vector-like lepton, and a real scalar. In this model, we propose searches for TeV scale leptoquarks in 2μ+2b+E̸T channel. Notably, the leptoquark can be produced singly at the muon collider with a large cross-section. We have shown that a significant signal in this channel can be detected at a 3 TeV muon collider even with an integrated luminosity as low as ∼10 fb−1.

Abstract The study of the polarization of heavy particles is an important branch of research in today’s collider physics. The massive W boson has two types of polarization states, which usually are studied via the angular distribution of its decay products. We present a jet substructure-based study on the polarization of a boosted W boson decaying hadronically, which forms a fat jet, in pp collision at the $$\sqrt{s}$$ s = 14 TeV at the LHC. Two different methods, viz. N-subjettiness and Soft Drop, were used to find the subjets, which are approximately considered to be the two hadronic decay products of W, inside boosted W jets. These subjets were then used to calculate two variables $$p_\theta =|E_1-E_2|/p_T^W$$ p θ = | E 1 - E 2 | / p T W and $$z_j=\max (p_{T_1},p_{T_2})/p_T^W$$ z j = max ( p T 1 , p T 2 ) / p T W , where the subscripts 1 and 2 are for two subjets and W represents the reconstructed W jet. We then prepared the templates for longitudinally and transversely polarized W. These templates were used to extract the fractions of different W polarization in a mixed sample with relatively good accuracy.

Abstract The study of standard QCD jets produced along with fat jets, which may appear as a result of the decay of a heavy particle, has become an essential part of collider studies. Current jet clustering algorithms, which use a fixed radius parameter for the formation of jets from the hadrons of an event, may be inadequate to capture the differing radius features. In this work, we develop an alternative jet clustering algorithm that allows the radius to vary dynamically based on local kinematics and distribution in the η-ϕ plane inside each evolving jet. We present the usefulness of this dynamic radius clustering algorithm through two Standard Model processes, and thereafter illustrate it for a scenario beyond the Standard Model at the 13 TeV LHC.

Abstract We study thermalization of charged SYK model in two different phases. We show that both the highly chaotic liquid phase and the dilute gas phase thermalize. Surprisingly the dilute gas state thermalizes instantaneously. We argue that this phenomenon arises because the system in this phase consists of only long-lived quasi-particles at very low density. The liquid state thermalizes exponentially fast. We also show that the additional introduction of random mass deformation (q = 2 SYK term) slows down thermalization but the system thermalizes exponentially fast. This is observed despite the fact that the addition of large q = 2 SYK interaction forces spectral statistics to obey Poisson statistics. An interesting new observation is that the effective temperature is non-monotonic during thermalization in the liquid state. It has a bump at relatively long time before settling down to the final value. With non-zero chemical potential, the effective temperature oscillates noticeably before settling down to the final value.

Abstract The search for new physics at high energy accelerators has been at the crossroads with very little hint of signals suggesting otherwise. The challenges at a hadronic machine such as the LHC is compounded by the fact that final states are swamped with jets which one needs to understand and unravel. A positive step in this direction would be to separate the jets in terms of their gluonic and quark identities, much in a similar spirit of distinguishing heavy quark jets from light quark jets that has helped in improving searches for both neutral and charged Higgs bosons at the LHC. In this work, we utilise this information using the jet substructure techniques to comment on possible improvements in sensitivity as well as discrimination of new resonances in the all hadronic mode that would be crucial in pinning down new physics signals at HL-LHC, HE-LHC and any future 100 TeV hadron collider.

Light radions constitute one of the few surviving possibilities for observable new particle states at the sub-TeV level which arise in models with extra spacetime dimensions. It is already known that the 125 GeV state discovered at CERN is unlikely to be a pure radion state, since its decays resemble those of the Standard Model Higgs boson too closely. However, due to experimental errors in the measured decay widths, the possibility still remains that it could be a mixture of the radion with one (or more) Higgs states. We use the existing LHC data at 8 and 13 TeV to make a thorough investigation of this possibility. Not surprisingly, it turns out that this model is already constrained quite effectively by direct LHC searches for an additional scalar heavier than 125 GeV. We then make a detailed study of the so-called ‘conformal point’, where this heavy state practically decouples from (most of) the Standard Model fields. Some projections for the future are also included.