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Register a new userReview of Higgs-to-light-Higgs searches at the LHC
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We review the most relevant LHC searches at $sqrt{s}$ = 8 TeV looking for low mass bosons arising from exotic decay of the Standard Model Higgs and highlighting their impact on both supersymmetric and not supersymmetric Beyond the Standard Model scenarios.
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Nobody knows exactly what kind of Higgs physics will be unveiled when the Large Hadron Collider is turned on. There could be one Standard Model Higgs boson or five Higgs bosons as is the case in two-Higgs-doublet models; there could be more exotic or even completely unexpected scenarios. In order to be prepared for the LHC era, a solid understanding of Standard Model or Standard-Model-like Higgs physics is necessary. The first goal is to discover the Higgs boson. Afterwards it has to be proven that the new particle is indeed a Higgs boson. The Higgs boson has to couple to mass and its spin has to be zero. Additional observables, such as decay width or CP eigenvalue, help to distinguish between different models. Due to an almost infinite variety of models, another important goal is to prepare for all possible situations. For example, Higgs bosons could be produced in decays of heavier particles, or could decay to invisible particles. In the following, a selection of mainly new studies by ATLAS and CMS is presented.
The goal of this report is to summarize the current situation and discuss possible search strategies for charged scalars, in non-supersymmetric extensions of the Standard Model at the LHC. Such scalars appear in Multi-Higgs-Doublet models (MHDM), in particular in the popular Two-Higgs-Doublet model (2HDM), allowing for charged and additional neutral Higgs bosons. These models have the attractive property that electroweak precision observables are automatically in agreement with the Standard Model at the tree level. For the most popular version of this framework, Model~II, a discovery of a charged Higgs boson remains challenging, since the parameter space is becoming very constrained, and the QCD background is very high. We also briefly comment on models with dark matter which constrain the corresponding charged scalars that occur in these models. The stakes of a possible discovery of an extended scalar sector are very high, and these searches should be pursued in all conceivable channels, at the LHC and at future colliders.
We study the Higgs boson $(h)$ decay to two light jets at the 14 TeV High-Luminosity-LHC (HL-LHC), where a light jet ($j$) represents any non-flavor tagged jet from the observational point of view. The decay mode $hto gg$ is chosen as the benchmark since it is the dominant channel in the Standard Model (SM), but the bound obtained is also applicable to the light quarks $(j=u,d,s)$. We estimate the achievable bounds on the decay branching fractions through the associated production $Vh (V=W^pm,Z)$. Events of the Higgs boson decaying into heavy (tagged) or light (un-tagged) jets are correlatively analyzed. We find that with 3000 fb$^{-1}$ data at the HL-LHC, we should expect approximately $1sigma$ statistical significance on the SM $Vh(gg)$ signal in this channel. This corresponds to a reachable upper bound ${rm BR}(hto jj) leq 4~ {rm BR}^{SM}(hto gg)$ at $95%$ confidence level. A consistency fit also leads to an upper bound ${rm BR}(hto cc) < 15~ {rm BR}^{SM}(hto cc)$ at $95%$ confidence level. The estimated bound may be further strengthened by adopting multiple variable analyses, or adding other production channels.
Vector-boson pair production is an important background for Higgs boson and new physics searches at the Large Hadron Collider LHC. We have calculated the loop-induced gluon-fusion process gg -> WW -> leptons, allowing for arbitrary invariant masses of the intermediate W bosons. This process contributes at O(alpha_s^2) relative to quark-antiquark annihilation, but its importance is enhanced by the large gluon flux at the LHC and by experimental cuts employed in Higgs boson searches. We find that gg -> WW provides only a moderate correction (ca. 5%) to the inclusive W-pair production cross section at the LHC. However, after taking into account realistic experimental cuts, the gluon-fusion process becomes significant and increases the theoretical WW background estimate for Higgs searches in the pp -> H -> WW -> leptons channel by approximately 30%.
A summary of the Higgs boson searches by the ATLAS and CMS collabrations using 1 f b-1 of LHC data is presented, concentrating on the Standard Model Higgs boson. Both experiments have the sensitivity to exclude at 95% CL a Standard Model Higgs boson in most of the Higgs boson mass region between about 130 GeV and 400 GeV. The observed data allow the exclusion of a Higgs Boson of mass 155 GeV to 190 GeV and 295 GeV to 450 GeV (ATLAS) and 149 GeV to 206 GeV and 300 GeV to 440 GeV (CMS). The lower limits are not as constraining as might be expected due to an excess in both experiments of order 2-3{sigma} which could be related to a low mass Higgs boson or to a statistical fluctuation.
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