Search

We consider the most general set of SU(2)×U(1) invariant CP-violating operators of dimension six, which contribute to VVh interactions (V=W, Z, γ). Our aim is to constrain any CP-violating new physics above the electroweak scale via the effective couplings that arise when such physics is integrated out. For this purpose, we use, in turn, electroweak precision data, global fits of Higgs data at the Large Hadron Collider and the electric dipole moments of the neutron and the electron. We thus impose constraints mainly on two-parameter and three-parameter spaces. We find that the constraints from the electroweak precision data are the weakest. Among the existing Higgs search channels, considerable constraints come from the diphoton signal strength. We note that potential contribution to h&→#947;Z may in principle be a useful constraining factor, but it can be utilized only in the high energy run. The contributions to electric dipole moments mostly lead to the strongest constraints, though somewhat fine-tuned combinations of more than one parameter with large magnitudes are allowed. We also discuss constraints on gauge boson trilinear couplings which depend on the parameters of the CP-violating operators. [ABSTRACT FROM AUTHOR]

We perform a thorough analysis of the parameter space of the minimal left-right supersymmetric model in agreement with the LHC data. The model contains left- and right-handed fermionic doublets, two Higgs bidoublets, two Higgs triplet representations, and one singlet, insuring a charge-conserving vacuum. We impose the condition that the model complies with the experimental constraints on supersymmetric particles masses and on the doubly charged Higgs bosons and require that the parameter space of the model satisfies the LHC data on neutral Higgs signal strengths at 2σ. We choose benchmark scenarios by fixing some basic parameters and scanning over the rest. The lightest supersymmetric particle in our scenarios is always the lightest neutralino. We find that the signals for H→γγ and H→VV are correlated, while H→bb is anticorrelated with all of the other decay modes, and also that the contribution from singly charged scalars dominates that of the doubly charged scalars in H→γγ and H→Zγ loops, contrary to type II seesaw models. We also illustrate the range for mass spectrum of the LRSUSY model in light of planned measurements of the branching ratio of H→γγ to 10% level. [ABSTRACT FROM AUTHOR]

We investigate how far a new physics scenario affecting primarily the third-generation fermions can ameliorate the tension between B decay observables and Standard Model expectations. Adopting a model-independent approach, we find that among the three observables that show signs of such a tension, viz., the branching fractions for B+ →τνBdD →(D*) τν, and the like-sign dimuon anomaly in neutral B decays, the first two can be explained adequately, while there is only a marginal improvement for the third. As a spin-off, it is shown that one can also accommodate a change in the branching fraction of the Higgs boson to a ν lepton pair from the Standard Model expectation, if such a change is established in future data. [ABSTRACT FROM AUTHOR]

Recently, a new mechanism has been proposed to cure the problem of fermion mass hierarchy in the standard model (SM) model. In this scenario, all SM charged fermions other than top quark arise from higher dimensional operators involving the SM Higgs field. This model also predicted some interesting phenomenology of the Higgs boson. We generalize this model to accommodate neutrino masses (Dirac and Majorana) and also obtain the mixing pattern in the leptonic sector. To generate neutrino masses, we add extra three right-handed neutrinos (NiR) in this model. [ABSTRACT FROM AUTHOR]

Sneutrino-antisneutrino oscillation can be a very useful probe to look for signatures of lepton number violation (ΔL = 2) at the Tevatron. Here, we discuss a scenario where the total decay width of the sneutrino is very small, producing interesting signals at the Tevatron for a mass splitting Δm as small as 10-14 GeV between the sneutrino mass eigenstates. [ABSTRACT FROM AUTHOR]

Recently the CDF Collaboration reported a statistically significant excess in the distribution of the dijet invariant mass between 120-160 GeV in Wjj event sample in 4.3 fb-1 of data and later confirmed with 7.3 fb-1 of data, which has generated considerable interest. We offer a possible explanation of this observation in the general framework of minimal supersymmetric standard model with R-parity violation through resonance production of ṽτ decaying into the LSP τ̃1 and W boson. We also give the predictions of this scenario for the LHC operating at 7 TeV center of mass energy. [ABSTRACT FROM AUTHOR]

The fermionic Z-portal dark matter model suffers from severe constraints from direct detection experiments. However, a narrow parameter space around the Z-funnel region is beyond the present reach due to the resonance annihilation. In this paper, we provide an intriguing collider prospect for probing the Z-funnel dark matter mass range at the future lepton colliders including the beam polarization feature. We have done a comprehensive analysis for monophoton signal at the colliders for such a dark matter. A realistic estimation for the 90% C.L. constraints with the systematic beam uncertainties has also been provided. [ABSTRACT FROM AUTHOR]

We explore a minimal supersymmetric standard model scenario extended by one pair of gauge singlets per generation. In the model, light neutrino masses and their mixings are generated via the inverse seesaw mechanism. In such a scenario, a right-handed sneutrino can be the lightest supersymmetric particle and a cold dark matter (DM) candidate. If the Casas-Ibarra parametrization is imposed on the Dirac neutrino Yukawa coupling matrix (Yv) to fit the neutrino oscillation data, the resulting Yv is highly constrained from the lepton-flavor-violating decay constraints. The smallness of Y? requires the sneutrino DM to coannihilate with other sparticle(s) in order to satisfy the DM relic density constraint. We study sneutrino coannihilation with winos and observe that this sneutrino-wino compressed parameter space gives rise to a novel same-sign trilepton signal for the top squark, which is more effective than the conventional top squark search channels in the present framework. We show that the choice of neutrino mass hierarchy strongly affects the signal event rate, making it easier to probe the scenario with the inverted mass hierarchy. [ABSTRACT FROM AUTHOR]

The extension of the standard model (SM) with two complex SU(2) L scalar triplets enables one to have the Type II seesaw mechanism operative consistently with texture-zero neutrino mass matrices. This framework predicts additional doubly charged, singly charged and neutral spinless states. We show that, for certain values of the model parameters, there is sufficient mass splitting between the two doubly charged states (H1±±, H2±±) that allows the decay H1±± → H2±±h, and thus leads to a unique signature of this scenario. We show that the final state 2(ℓ±ℓ±) + 4b + ET arising from this mode can be observed at the high energy, high luminosity (HE-HL) run of the 14 TeV Large Hadron Collider (LHC), and also at a 100 TeV Future Circular Collider (FCC-hh). [ABSTRACT FROM AUTHOR]

The type II seesaw model is a well-motivated new physics scenario to address the origin of the neutrino mass issue. We show that this model can easily accommodate an absolutely stable vacuum until the Planck scale, however with strong limit on the exotic scalar masses and the corresponding mixing angle. We examine the model prediction at the current and future high luminosity run of the Large Hadron Collider (LHC) for the scalar masses and mixing angles fixed at such high-scale valid region. Specifically, we device the associated and pair production of the charged scalars as a new probe of the model at the LHC. We show that for a particular signal process the model can be tested with 5s signal significance even at the present run of the LHC. [ABSTRACT FROM AUTHOR]

Higgs signatures from the cascade decays of light top squarks are an interesting possibility in the next-to-minimal supersymmetric standard model (NMSSM). We investigate the potential reach of the light top-squark mass at the 13 TeV run of the LHC by means of five NMSSM benchmark points where this signature is dominant. These benchmark points are compatible with current Higgs coupling measurements, LHC constraints, dark matter relic density and direct-detection constraints. We consider single and dilepton search strategies, as well as the jet-substructure technique to reconstruct the Higgs bosons. We find that one can probe top-squark masses up to 1.2 TeV with 300 fb-1 luminosity via the dilepton channel, while with the jet-substructure method, top-squark masses up to 1 TeV can be probed with 300 fb-1 luminosity. We also investigate the possibility of the appearance of multiple Higgs peaks over the background in the fat-jet mass distribution, and conclude that such a possibility is viable only at the high-luminosity run of the 13 TeV LHC. [ABSTRACT FROM AUTHOR]

The CP-violating version of the Minimal Supersymmetric Standard Model is an example of a model where experimental data do not preclude the presence of light Higgs bosons in the range around 10-110 GeV. Such light Higgs bosons, decaying almost wholly to b... pairs, may be copiously produced at the LHC but would remain inaccessible to conventional Higgs searches because of intractable QCD backgrounds. We demonstrate that a significant number of these light Higgs bosons would be boosted strongly enough for the pair of daughter b-jet pairs to appear as a single 'fat' jet with substructure. Tagging such jets could extend the discovery potential at the LHC into the hitherto-inaccessible region for light Higgs bosons. [ABSTRACT FROM AUTHOR]

We study the implications of the searches based on H →&Tgr;+&Tgr;- by the ATLAS and CMS collaborations on the parameter space of the two-Higgs-doublet model (2HDM). In the 2HDM, the scalars can decay into a tau pair with a branching ratio larger than the SM one, leading to constraints on the 2HDM parameter space. We show that in model II, values of tan&bgr; > 1.8 are definitively excluded if the pseudoscalar is in the mass range 110 GeV < mA> < 145 GeV. We have also discussed the imphcations for the 2HDM of the recent dimuon search by the ATLAS collaboration for a CP-odd scalar in the mass range 4-12 GeV. [ABSTRACT FROM AUTHOR]

We investigate the possibility of probing an anomalous CP-violating coupling in the HWW vertex at the LHC. We consider the production of the Higgs boson in association with a W and then decay via the H→WW channel taking into account the limits on the Higgs production cross section from the Tevatron. We select the same-sign dilepton final state arising from leptonic decays of two of the three Ws and apply cuts required to suppress the standard model background. Several kinematical distributions and asymmetries that can be used to ascertain the presence of a nonzero anomalous coupling are presented. We find that, for Higgs mass in the range 130-150 GeV and anomalous couplings allowed by the Tevatron data, these distributions can be studied with an integrated luminosity of 30-50??fb-1 at the 14 TeV run. Attention is specifically drawn to some asymmetries that enable one to probe the real and imaginary parts (as well as their signs) of the anomalous coupling, in a complementary manner. We also explicitly demonstrate that showering and hadronization do not affect the utility of these variables, thus affirming the validity of parton-level calculations. [ABSTRACT FROM AUTHOR]

In the context of a left-right symmetric model, we introduce one full generation of vectorlike lepton doublets (both left- and right-handed) together with their mirror doublets. We show that the lightest vectorlike neutrino in the model is right-handed, and can serve as the dark matter candidate. We find that the relic density as well as the direct and indirect DM detection bounds are satisfied for a large range of the parameter space of the model. In accordance with the parameter space, we then explore the possibility of detecting signals of the model at both the LHC and the ILC, in the pair production of the associated vectorlike charged leptons which decay into final states including dark matter. A comprehensive analysis of signal and backgrounds shows that the signals at the ILC, especially with polarized beams, are likely to be visible for light vectorlike leptons, even with low luminosity, rendering our model highly predictable and experimentally testable. [ABSTRACT FROM AUTHOR]

The ATLAS and CMS Collaborations have observed independently at the LHC a new Higgs-like particle with a mass Mh ~ 125 GeV and properties similar to that predicted by the Standard Model (SM). Although the measurements indicate that this Higgs-like boson is compatible with the SM hypothesis, due to large uncertainties in some of the Higgs detection channels, one still has the possibility of testing this object as being a candidate for some beyond the SM physics scenarios, for example, the minimal supersymmetric Standard Model (MSSM), in the CP-conserving version (CPC-MSSM). In this paper, we evaluate the modifications of these CPC-MSSM results when CP-violating (CPV) phases are turned on explicitly, leading to the CP-violating MSSM (CPV-MSSM). We investigate the effect of the CPV phases in (some of) the soft supersymmetry (SUSY) terms on both the mass of the lightest Higgs boson h1, and the rates for the processes gg → h¹ → yy, gg → h1 → ZZ* -> 41, gg → h1 → WW* → lulu, pp → Vh¹ → Vbb and pp → Vh1 → Vτ++-, (V = W±, Z) at the LHC, considering the impact of the flavor constraints as well as the constraints coming from the electric dipole moment measurements. We find that it is possible to have a Higgs mass of about 125 GeV with relatively small tan β, large At, and a light top squark, which is consistent with the current SUSY particle searches at the LHC. We obtain that the imaginary part of the top and bottom Yukawa couplings can take very small but nonzero values even after satisfying the recent updates from both the ATLAS and CMS Collaborations within 1-2σ uncertainties which might be an interesting signature to look for at the future run of the LHC. Our study shows that the CPV-MSSM provides an equally possible solution (like its CP-conserving counterpart) to the recent LHC Higgs data, in fact offering very little in the way of distinction between these two SUSY models (CPC-MSSM and CPV-MSSM) at the 7 and 8 TeV runs of the LHC. Improvement in different Higgs coupling measurements is necessary in order to test the possibility of probing the small dependence on these CPV phases in the Higgs sector of the MSSM. [ABSTRACT FROM AUTHOR]

We discuss both the minimal supersymmetric Standard Model (MSSM) and next to MSSM scenarios in which the lightest Higgs boson with mh=98 GeV is consistent with the small excess (~2.3σ) observed at the LEP in e+e-→Zh, with the h→bb process and the heavier Higgs boson of mass close to 125 GeV as the observed candidate of the SM Higgs-like particle at the LHC. We show the allowed regions in the nondecoupling Higgs zone of MSSM parameter space which are consistent with several low energy constraints coming from heavy flavor physics, the latest experimental data on Higgs signals, and the lower limit on superparticle masses from 7 and 8 TeV LHC runs. We also implement the constraints from the relic density of the cold dark matter as obtained from the recent PLANCK data. Additionally, we discuss the possibility of observing the light Higgs boson of mass 98 GeV at the 14 TeV LHC run via pp→Vh, with h→bb using the technique of jet substructure. Our analysis shows that at a 14 TeV LHC run with 300 fb-1 luminosity the signal efficiency of such a light Higgs boson is at most 2.5σ. Finally, we make a comment on the prospect of the proposed e+e- International Linear Collider to discover/exclude this light Higgs boson. [ABSTRACT FROM AUTHOR]

We consider a scenario of a minimal supersymmetric standard model with R-parity violation, where the lightest supersymmetric particle is the lighter bottom squark (b1). We study the production of a bottom squark pair at the LHC and their subsequent decays through the baryon number violating operators leading to a top pair with two light quarks. Looking for both semileptonic and fully hadronic (no leptons) final states, we perform cut-based as well as multivariate analyses (MVA) to estimate the signal significance at the 13 TeV run of the LHC. We find that a cut-based analysis can probe bottom squark mass up to ~750 GeV, which may be extended up to ~850 GeV using MVA with 300 fb-1 integrated luminosity. The fully hadronic final state, however, is not as promising. [ABSTRACT FROM AUTHOR]