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Register a new userThe compatibility of LHC Run 1 data with a heavy scalar of mass around 270,GeV
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The first run of the LHC was successful in that it saw the discovery of the elusive Higgs boson, a particle that is consistent with the SM hypothesis. There are a number of excesses in Run 1 ATLAS and CMS results which can be interpreted as being due to the existence of another heavier scalar particle. This particle has decay modes which we have studied using LHC Run 1 data. Using a minimalistic model, we can predict the kinematics of these final states and compare the prediction against data directly. A statistical combination of these results shows that a best fit point is found for a heavy scalar having a mass of 272$^{+12}_{-9}$,GeV. This result has been quantified as a three sigma effect, based on analyses which are not necessarily optimized for the search of a heavy scalar. The smoking guns for the discovery of this new heavy scalar and the prospects for Run 2 are discussed.
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In recent years, hints for multi-lepton anomalies have been accumulated by the analysis of Large Hadron Collider (LHC) data, pointing towards the existence of beyond the Standard Model (SM) Higgs bosons: a new scalar particle $S$ with a mass $m_S$ in the range between $130,$GeV and $160,$GeV, produced from the decay of a heavier new scalar particle, $H$. Motivated by this observation, we perform a search for the signatures of $S$ within this mass region, which has been studied by CMS and ATLAS as a by-product of the SM Higgs searches in the side-bands of the kinematic regions. Combining the $gammagamma$ and $Zgamma$ channels, with associated leptons, di-jets, bottom quarks and missing energy, we obtain a local (global) significance of 5.1$sigma$ (4.8$sigma$) for a mass of $m_S= 151.5$,GeV and provide the preferred ranges for the corresponding (fiducial) cross sections. This is a strong indication for a scalar resonance $S$ decaying into photons, and, to a lesser extent to $Zgamma$, in association with missing energy, jets or leptons. Hints for the decays into, or production in association with, bottom quarks are statistically less significant. In order to test this hypothesis, we propose a search for $Hrightarrow gammagamma boverline{b},tau^+tau^- boverline{b}$ in asymmetric configurations that has not yet been performed by ATLAS and CMS.
The Madala hypothesis postulates a new heavy scalar, H, which explains several independent anomalous features seen in ATLAS and CMS data simultaneously. It has already been discussed and constrained in the literature by Run 1 results, and its underlying theory has been explored under the interpretation of a two Higgs doublet model coupled with a scalar singlet, $S$. When applying the hypothesis to Run 2 results, it can be shown that the constraints from the data are compatible with those obtained using Run 1 results.
We make a frequentist analysis of the parameter space of the NUHM2, in which the soft supersymmetry (SUSY)-breaking contributions to the masses of the two Higgs multiplets, $m^2_{H_{u,d}}$, vary independently from the universal soft SUSY-breaking contributions $m^2_0$ to the masses of squarks and sleptons. Our analysis uses the MultiNest sampling algorithm with over $4 times 10^8$ points to sample the NUHM2 parameter space. It includes the ATLAS and CMS Higgs mass measurements as well as their searches for supersymmetric jets + MET signals using the full LHC Run~1 data, the measurements of $B_s to mu^+ mu^-$ by LHCb and CMS together with other B-physics observables, electroweak precision observables and the XENON100 and LUX searches for spin-independent dark matter scattering. We find that the preferred regions of the NUHM2 parameter space have negative SUSY-breaking scalar masses squared for squarks and sleptons, $m_0^2 < 0$, as well as $m^2_{H_u} < m^2_{H_d} < 0$. The tension present in the CMSSM and NUHM1 between the supersymmetric interpretation of $g_mu - 2$ and the absence to date of SUSY at the LHC is not significantly alleviated in the NUHM2. We find that the minimum $chi^2 = 32.5$ with 21 degrees of freedom (dof) in the NUHM2, to be compared with $chi^2/{rm dof} = 35.0/23$ in the CMSSM, and $chi^2/{rm dof} = 32.7/22$ in the NUHM1. We find that the one-dimensional likelihood functions for sparticle masses and other observables are similar to those found previously in the CMSSM and NUHM1.
The Standard Model (SM) Higgs boson, with its experimental discovery in 2012, has long been an interesting particle to study with the intention of exploring new physics ideas beyond the SM (BSM). Its properties are still not well understood, and there are several features in LHC Run 1 and Run 2 data which point at the possibility of extensions to the SM Higgs sector. This work explores the Madala hypothesis, which is the introduction of a heavy scalar (the Madala boson) to the SM, in addition to a real scalar $S$ and dark matter (DM) candidate $chi$. This hypothesis has previously been used to explain several anomalous features observe in the LHC Run 1 data. This work extends the study to Run 2 data, and shows that the particle spectrum predicted in the Madala hypothesis is indeed compatible with LHC data. Further study prospects and striking signatures for searches are presented.
In some extensions of the Standard Model, Yukawa couplings of the physical Higgs boson can be deviated from those in the Standard Model. We study a possibility whether or not such anomalous Yukawa couplings are consistent with the LHC Run 1 data. It is found that sizable deviations of top and bottom (and tau) Yukawa couplings from the Standard Model predictions can nicely fit the data. New physics beyond the Standard Model can be revealed through more precise measurements of such anomalous Yukawa couplings at the LHC Run 2 in the near future. We also discuss a simple setup which can leads to anomalous Yukawa couplings.
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