Tirtha Sankar Ray

UV descriptions of composite Higgs models without elementary scalars

A bstractWe consider four-dimensional UV descriptions of composite Higgs models without elementary scalars, in which four-fermion interactions are introduced to an underlying gauge theory like in the gauged NJL model. When the anomalous dimension of the fermion bilinear is large, these interactions drive the spontaneous global symmetry breaking in the model, with the Higgs identified as a Nambu-Goldstone boson. The UV descriptions support composite top partner operators, also with large anomalous dimensions, thereby providing an explicit realisation of the idea of partial compositeness. In particular, the composite SO(6)/SO(5) model can be described by an Sp gauge theory with four flavours of fermion, together with a vector-like pair of fermions transforming in the antisymmetric representation and charged under SU(3) colour. These fermions confine to produce both the Higgs and top partner bound states. Our methods can also be applied to different coset groups, suggesting that four-fermion operators can describe the underlying UV dynamics of other composite Higgs models.

Burgeoning the Higgs mass to 125 GeV through messenger-matter interactions in GMSB models

A bstractA 125 GeV Higgs renders the simpler GMSB models unnatural, essentially pushing the soft spectrum beyond the LHC reach. A direct coupling of the matter and messenger fields, that facilitates an enhanced mixing in the squark sector, is a way to ameliorate this deficiency. We construct all possible messenger-matter interaction terms considering the messenger multiplets in 1, 5 and 10 dimensional representations of the SU(5). A Froggatt-Nielsen like flavor framework connected with the origin of fermion mass hierarchy is utilized to control the interaction terms and suppress FCNC. We perform a detailed comparative study of the efficiency of such interaction terms to boost the Higgs mass keeping the soft spectrum light. We identify the more promising models and comment on their status in present and future collider studies.

Constraining minimal and nonminimal universal extra dimension models with Higgs couplings

Early indications from the LHC for the observed scalar boson imply properties close to the Standard Model Higgs, putting considerable constraints on TeV scale new physics scenarios. In this letter we consider flat extra dimensional scenarios with the fifth spatial dimen sion compactified on an S 1 /Z2 orbifold. We find in the minimal model the experimentally preferred effective Higgs couplings to gluon and photon at 95% confidence level disfavor the New Physics scale below 1.3 TeV. We demonstrate that a generalization of these models to include brane localized kinetic terms can relieve the tension to accommodate scales as low as 0.4 TeV.

The unnatural composite Higgs

A bstractComposite Higgs models can trivially satisfy precision-electroweak and flavour constraints by simply having a large spontaneous symmetry breaking scale, f ≳ 10 TeV. This produces a ‘split’ spectrum, where the strong sector resonances have masses greater than 10 TeV and are separated from the pseudo Nambu-Goldstone bosons, which remain near the electroweak scale. Even though a tuning of order 10−4 is required to obtain the observed Higgs boson mass, the big hierarchy problem remains mostly solved. Intriguingly, models with a fully-composite right-handed top quark also exhibit improved gauge coupling unification. By restricting ourselves to models which preserve these features we find that the symmetry breaking scale cannot be arbitrarily raised, leading to an upper bound f ≲ 100-1000 TeV. This implies that the resonances may be accessible at future colliders, or indirectly via rare-decay experiments. Dark matter is identified with a pseudo Nambu-Goldstone boson, and we show that the smallest coset space containing a stable, scalar singlet and an unbroken SU(5) symmetry is SU(7)/SU(6) × U(1). The colour-triplet pseudo Nambu-Goldstone boson also contained in this coset space is metastable due to a residual symmetry. It can decay via a displaced vertex when produced at colliders, leading to a distinctive signal of unnaturalness.

Radion/dilaton-Higgs mixing phenomenology in light of the LHC

A bstractMotivated by the bulk mixing ξR5H†H between a massive radion and a bulk scalar Higgs in warped extra dimensions, we construct an effective four dimensional action that — via the AdS/CF T correspondence — describes the most general mixing between the only light states in the theory, the dilaton and the Higgs. Due to conformal invariance, once the Higgs scalar is localized in the bulk of the extra-dimension the coupling between the dilaton and the Higgs kinetic term vanishes, implying a suppressed coupling between the dilaton and massive gauge bosons. We comment on the implications of the mixing and couplings to Standard Model particles. Identifying the recently discovered 125 GeV resonance with the lightest Higgs-like mixed state ϕ−, we study the phenomenology and constraints for the heaviest radion-like state ϕ+. In particular we find that in the small mixing scenario with a radion-like state ϕ+ in the mass range [150, 250] GeV, the diphoton channel can provide the best chance of discovery at the LHC if the collaborations extend their searches into this energy range.

On Composite Two Higgs Doublet Models

A bstractWe investigate the issue of anomalous contribution to the T parameter and to Flavor Changing Neutral Currents in models with two Higgs doublets arising as composite pseudo Nambu-Goldstone modes. The non linear Lagrangians of several models are explicitly derived and the anomalous contributions to T are identified. The breaking patterns SU(5) → SU(4) × U(1) and SU(5) → SU(4), are analyzed first and we show how anomalous contributions to T arise in both models. Apart from that, the embedding of the Standard Model fermions in a 10 of SU(5) avoids at the same time large corrections to the

Probing warped extra dimension via gg→h and h→γγ at LHC

Zb\overline{b}

Same sign di-lepton candles of the composite gluons

coupling and Flavor Changing Neutral Current transitions. Finally, we propose a model based on the breaking SO(9)/SO(8) that is free from anomalous contributions to T and in which the problems of the

Radiative corrections to the composite Higgs mass from a gluon partner

Zb\overline{b}

Naturally split supersymmetry

coupling and of Flavor Changing Neutral Currents can be simultaneously solved.