We study the Higgs portal from the Standard-Model to a hidden sector and examine which elements of the extended theory can be discovered and explored at the LHC. Our model includes two Higgs bosons ...covering parameter regions where the LHC will be sensitive to two, one or none of the particles at typical discovery luminosities for Standard Model Higgs production.
LHC: Standard Higgs and hidden Higgs Englert, Christoph; Plehn, Tilman; Rauch, Michael ...
Physics letters. B,
02/2012, Letnik:
707, Številka:
5
Journal Article
Recenzirano
Odprti dostop
Interpretations of Higgs searches critically involve production cross sections and decay probabilities for different analysis channels. Mixing effects can reduce production rates, while invisible ...decays can reduce decay probabilities. Both effects may transparently be quantified in Higgs systems where a visible Higgs boson is mixed with a hidden sector Higgs boson. Recent experimental exclusion bounds can be re-interpreted in this context as a sign for non-standard Higgs properties. Should a light Higgs boson be discovered, then our analysis will quantify how closely it may coincide with the Standard Model.
The Higgs boson spectrum of the next-to-minimal supersymmetric standard model is examined. The model includes a singlet Higgs field
S in addition to the two Higgs doublets of the minimal extension. ...‘Natural’ values of the parameters of the model are motivated by their renormalization group running and the vacuum stability. The qualitative features of the Higgs boson masses are dependent on how strongly the Peccei–Quinn
U(1) symmetry of the model is broken, measured by the self-coupling of the singlet field in the superpotential. We explore the Higgs boson masses and their couplings to gauge bosons for various representative scenarios.
The basic structure of top-quarks as spin-1/2 particles is characterized by the radius Rt and the intrinsic magnetic dipole moment κt, both individually associated with gauge interactions. They are ...predicted to be zero in pointlike theories as the Standard Model. We derive upper limits of these parameters in the color sector from cross sections measured at Tevatron and LHC in top pair production pp¯/pp→tt¯, and we predict improved limits expected from LHC in the future, especially for analyses exploiting boosted top final states. An additional method for measuring the intrinsic parameters is based on tt¯+jet final states.
Higgs bosons can be searched for in the channels pp macro/pp-->tt macro H + X at the Fermilab Tevatron and the Cern Large Hadron Collider (LHC). We have calculated the QCD corrections to these ...processes in the standard model at next-to-leading order. The higher-order corrections reduce the renormalization and factorization scale dependence considerably and stabilize the theoretical predictions for the cross sections. At the central scale mu = (2m(t)+M(H))/2 the properly defined K factors are slightly below unity for the Tevatron (K approximately 0.8) and slightly above unity for the LHC (K approximately 1.2).
The color gauge hyper-multiplet in N=2 supersymmetry consists of the usual N=1 gauge vector/gaugino super-multiplet, joined with a novel gaugino/scalar super-multiplet. Large cross sections are ...predicted for the production of pairs of the color-octet scalars σ sgluons at the LHC: gg, qq¯→σσ*. Single σ production is possible at one-loop level, but the gg→σ amplitude vanishes in the limit of degenerate L and R squarks. When kinematically allowed, σ decays predominantly into two gluinos, whose cascade decays give rise to a burst of eight or more jets together with four LSP's as signature for σ pair events at the LHC. σ can also decay into a squark–antisquark pair at tree level. At one-loop level σ decays into gluons or a tt¯ pair are predicted, generating exciting resonance signatures in the final states. The corresponding partial widths are very roughly comparable to that for three body final states mediated by one virtual squark at tree level.
Higgs couplings can be affected by physics beyond the Standard Model. We study modifications through interactions with a hidden sector and in specific composite Higgs models accessible at the LHC. ...Both scenarios give rise to congruent patterns of universal, or partially universal, shifts. In addition, Higgs decays to the hidden sector may lead to invisible decay modes which we also exploit. Experimental bounds on such potential modifications will measure the concordance of an observed Higgs boson with the Standard Model.
The Higgs sector is extended in R-symmetric supersymmetry theories by two iso-doublets Rd,u which complement the standard iso-doublets Hd,u. We have analyzed masses and interactions of these novel ...states and describe their non-standard decay modes and their production channels at the LHC and e+e− colliders.
Multiple Higgs-portal and gauge-kinetic mixings Choi, S. Y.; Englert, C.; Zerwas, P. M.
The European physical journal. C, Particles and fields,
12/2013, Letnik:
73, Številka:
12
Journal Article
Recenzirano
Odprti dostop
We develop a phenomenological formalism for mixing effects between the Standard Model and hidden-sector fields, motivated by dark matter in the Universe as well as string theories. The scheme ...includes multiple Higgs-portal interactions in the scalar sector as well as multiple gauge-kinetic mixings in the abelian gauge sector. While some of the mixing effects can be cast in closed form, other elements can be controlled analytically only by means of perturbative expansions in the ratio of standard scales over large hidden scales. Higgs and vector-boson masses and mixings are illustrated numerically for characteristic processes.
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