1,721,014 research outputs found
The Higgs boson beyond Standard Model
Full text linkWe will review the status of the Higgs boson beyond Standard Model. This proceeding will be focused on the experimental and theoretical status of the Higgs boson in the Composite Higgs models. In particular we will discuss implications on the beyond Standard Model (BSM) Higgs coming from the observed excess at 125 GeV
Challenges of EFT at the LHC
Full text linkI will discuss the difficulties of putting constraints on the Effective Field Theories (EFT) at the Large Hadron Collider (LHC). In particular, I will analyse the generic properties of the 2 ! 2 scattering in the presence of the higher dimensional operators indicating that some of the beyond Standard Model effects are parametrically smaller than naive expectations
Light custodians and Higgs physics in composite models
No full textComposite Higgs models involving partial compositeness of standard model fermions typically require the introduction of fermionic partners which are relatively light in realistic scenarios. In this paper, we analyze the role of these light custodian fermions in the phenomenology of the composite Higgs models and show that they significantly modify couplings of the Higgs field. We focus on the coupling to gluons, in particular, which is of central importance for Higgs production at the LHC. We show that this coupling can be increased as well as decreased depending on the standard model fermion embedding in the composite multiplets. We also discuss modification of the Higgs couplings to bottom and top quarks and show that modifications to all three couplings-Hgg, H (t) over bart, and H (b) over barb-are generically independent parameters
Bubble wall velocity: heavy physics effects
Full text linkWe analyse the dynamics of the relativistic bubble expansion during the first order phase transition focusing on the ultra relativistic velocities γ 1. We show that fields much heavier than the scale of the phase transition can significantly contribute to the friction and modify the motion of the bubble wall leading to interesting phenomenological consequences. NLO effects on the friction due to the soft vector field emission are reviewed as well
Dark Matter production from relativistic bubble walls
Full text linkIn this paper we present a novel mechanism for producing the observed Dark Matter (DM) relic abundance during the First Order Phase Transition (FOPT) in the early universe. We show that the bubble expansion with ultra-relativistic velocities can lead to the abundance of DM particles with masses much larger than the scale of the transition. We study this non-thermal production mechanism in the context of a generic phase transition and the electroweak phase transition. The application of the mechanism to the Higgs portal DM as well as the signal in the Stochastic Gravitational Background are discussed. © 2021, The Author(s)
Electroweak Symmetry Breaking and the Higgs Boson: Confronting Theories at Colliders
No full textIn this review, we discuss methods of parsing direct information from collider experiments regarding the Higgs boson and describe simple ways in which experimental likelihoods can be consistently reconstructed and interfaced with model predictions in pertinent parameter spaces. We review prevalent scenarios for extending the electroweak symmetry breaking sector and emphasize their predictions for nonstandard Higgs phenomenology that could be observed in large hadron collider (LHC) data if naturalness is realized in particular ways. Specifically we identify how measurements of Higgs couplings can be used to imply the existence of new physics at particular scales within various contexts. The most dominant production and decay modes of the Higgs-like state observed in the early data sets have proven to be consistent with predictions of the Higgs boson of the Standard Model, though interesting directions in subdominant channels still exist and will require our careful attention in further experimental tests. Slightly anomalous rates in certain channels at the early LHC have spurred effort in model building and spectra analyses of particular theories, and we discuss these developments in some detail. Finally, we highlight some parameter spaces of interest in order to give examples of how the data surrounding the new state can most effectively be used to constrain specific models of weak scale physics
Higgs mediated flavor changing neutral currents in warped extra dimensions
No full textIn the context of a warped extra dimension with standard model fields in the bulk, we obtain the general flavor structure of the Higgs couplings to fermions. These couplings will be generically misaligned with respect to the fermion mass matrix, producing large and potentially dangerous flavor changing neutral currents. As recently pointed out [K. Agashe and R. Contino, arXiv:0906.1542.], a similar effect is expected from the point of view of a composite Higgs sector, which corresponds to a four-dimensional theory dual to the five-dimensional setup by the AdS/CFT correspondence. We also point out that the effect is independent of the geographical nature of the Higgs (bulk or brane localized), and specifically that it does not go away as the Higgs is pushed towards the IR boundary. The flavor changing neutral currents mediated by a light enough Higgs (especially their contribution to epsilon(K)) could become of comparable size as the ones coming from the exchange of Kaluza-Klein gluons. Moreover, both sources of flavor violation are complementary since they have inverse dependence on the five-dimensional Yukawa couplings, such that we cannot decouple the flavor violation effects by increasing or decreasing these couplings. We also find that for Kaluza-Klein scales of a few TeV, the Higgs couplings to third generation fermions could experience suppressions of up to 40% while the rest of diagonal couplings would suffer much milder corrections. Potential LHC signatures like the Higgs flavor violating decays h -> mu tau or h -> tc, or the exotic top decay channel t -> ch, are finally addressed
Superconformal Technicolor
No full textIn supersymmetric theories with a strong conformal sector, soft supersymmetry breaking at the TeV scale naturally gives rise to confinement and chiral symmetry breaking at the same scale. We consider two such scenarios, one where the strong dynamics induces vacuum expectation values for elementary Higgs fields, and another where the strong dynamics is solely responsible for electroweak symmetry breaking. In both cases, the mass of the Higgs boson can exceed the LEP bound without tuning, solving the supersymmetry naturalness problem. A good precision electroweak fit can be obtained, and quark and lepton masses are generated without flavor-changing neutral currents. In addition to standard supersymmetry signals, these models predict production of multiple heavy standard model particles (t, W, Z, and b) from decays of resonances in the strong sector
Radion Mediated Flavor Changing Neutral Currents
No full textIn the context of a warped extra dimension with standard model fields in the bulk, we obtain the general flavor structure of the radion couplings to fermions and show that the result is independent of the particular nature of the Higgs mechanism (bulk or brane localized). These couplings will be generically misaligned with respect to the fermion mass matrix when the fermion bulk mass parameters are not all degenerate. When the radion is light enough, the generic size of these tree-level flavor changing couplings will be strongly constrained by the experimental bounds on Delta F = 2 processes. At the LHC the possibility of a heavier radion decaying into top and charm quarks is then considered as a promising signal to probe the flavor structure of both the radion sector and the whole scenario
Four-fermion operators at dimension 6: dispersion relations and UV completions
Full text linkA major task in phenomenology today is constraining the parameter space of
SMEFT and constructing models of fundamental physics that the SM derives from.
To this effect, we report an exhaustive list of sum rules for 4-fermion
operators of dimension 6, connecting low energy Wilson coefficients to
cross-sections in the UV. Unlike their dimension 8 counterparts which are
amenable to a positivity bound, the discussion here is more involved due to the
weaker convergence and indefinite signs of the dispersion integrals. We
illustrate this by providing examples with weakly coupled UV completions
leading to opposite signs of the Wilson coefficients for both convergent and
non-convergent dispersion integrals. We further decompose dispersion integrals
under weak isospin and color groups which lead to a tighter relation between IR
measurements and UV models. These sum rules can become an effective tool for
constructing consistent UV completions for SMEFT following the prospective
measurement of these Wilson coefficients.Comment: 24 page
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