Pseudo-Higgs Signals a the LHC

Abstract

We consider general fermi-phobic scenarios in which excess events in diphoton or WW/ZZ resonances may be seen at LHC. These Higgs like signals do not necessarily suggest that the new resonance is a particle with Yukawa couplings nor do we know that it is responsible for electroweak symmetry breaking. We can, however, extract two facts from it, this particle couples to pairs of SU(2) and U(1) gauge bosons and it must be a scalar, pseudoscalar, or tensor. We consider the signals of general operators up to effective dimension 5 in which a new scalar, psuedo-scalar, or tensor particle may couple to pairs of standard model gauge bosons. This particle may or may not be charged under the standard model gauge groups, and may be produced via gluon fusion or EW vector boson fusion. I. INTRODUCTIONThe Standard Model (SM) has been amazingly successful in describing fundamental interactions however, it remains incomplete. The Higgs boson is most likely the particle responsible for electroweak symmetry breaking, though it has yet to be discovered. The Higgs mass is not a known quantity however, its production cross sections and branching fractions to SM particles are well known [1][2][3]. At the LHC both the production and the decay of the Higgs boson are dominated by processes in which the Higgs has effective couplings to pairs of SM gauge bosons. While Higgs production is dominated by gluon fusion [4], it does not couple directly to gluons but has a large effective coupling them through a loop of heavy quarks. At low masses (m H 130GeV), the Higgs decays predominately to b b however, large QCD backgrounds at LHC make this channel difficult to see. Thus, the Higgs decays to pairs of electroweak gauge bosons are crucial for Higgs searches. In fact one of the most important channels for Higgs discovery is h → γγ. Again, the Higgs does not couple directly to photons but it has an effective coupling brought about by loops of charged W bosons and heavy third generation quarks. In fact, decays to weak boson pairs become dominate once we reach the kinematic threshold since the leading term in the partial width of Higgs to diboson is cubic in Higgs mass versus linear in Higgs mass for partial width to fermion pairs. LEP, Tevatron, and now ATLAS and CMS have been chipping away at Higgs mass parameter space leaving only a small window for the SM Higgs to hide [5][6]. Recent search results from both ATLAS and CMS have reported a small excess in the WW channel and a slightly larger excess in the ZZ and γγ channels around 125GeV [7][8]. While this excess may be the first hint at the SM Higgs, it is not yet a discovery.However, seeing a mass resonance in a diboson channel does not necessarily mean that the particle being produced is a Higgs. One would still be lacking evidence that the particle has the standard Yukawa couplings, or that it is responsible for electro-weak symmetry breaking. In fact, if a mass resonance is seen in and EW boson channel the new state may not have effective couplings to gluons as the Higgs does, unlike the Higg...

LEX-EFT: The light exotics effective field theory

“…We note that in addition to coupling directly to pairs of gauge field-strength tensors, LEX states may couple to pairs of weak gauge bosons by coupling to the Higgs kinetic term 𝐷 𝜇 𝐻 𝐷 𝜇 𝐻 † [17].…”

Strange couplings to the Higgs

“…Some interesting studies in a similar spirit (but asking different questions) can be found in Refs. [10][11][12][13][14][15].…”

“…FIG.3: log 10 of the fractional difference in the rate of pp → φ → γγ between a model with κ s = 1 and κ s = 50(10), indicated by the upper (lower) curve, with κ g adjusted such that the over-all rate at √ s = 7 TeV is SM-like.…”