Friday, May 10, 2019

Pheno papers on \(96\GeV\) Higgs, trilepton excess, and \(60\GeV\) dark matter

I want to mention two new hep-ph papers about supersymmetry-like anomalies seen by the accelerators. In the paper
An N2HDM Solution for the possible \(96\GeV\) Excess,
B+C+Heinemeyer discuss some detailed models for the apparent weak signals indicating a new Higgs boson of mass around \(96\GeV\). Recall that the only well-established Higgs boson has the mass of \(125\GeV\).

Concerning the \(96\GeV\) little brother, the CMS has seen an excess in the diphoton channel; and decades ago, LEP has seen an excess in the bottom quark pair channel. Heinemeyer and friends say that these excesses may be explained by a two-Higgs model with an extra Higgs singlet. Is that surprising at all? There seems to be a lot of freedom to accommodate two independent excesses, right?

At any rate, concerning supersymmetric models, the NMSSM – next-to-minimal supersymmetric standard model – and its extension, µνSSM seem like aesthetically pleasing completions of the two-Higgs-plus-a-singlet models. In the model with the two Greek letters, the singlet is interpreted as a right-handed neutrino superfield and the seesaw mechanism is incorporated. These models look OK for the excesses – there are other reasons to prefer NMSSM over MSSM. But they're also less constrained and predictive than the MSSM, so I think the good news isn't remarkably victorious.

Another paper on the excesses is
The Return of the WIMP: Missing Energy Signals and the Galactic Center Excess
by Carena+Osborne+Shah+Wagner. They promote a model with the dark matter of mass \(m_\chi = 60\GeV\) and its justification by anomalies that exist out there.

The dark matter of that mass would be the lightest neutralino. It could naturally agree with the 3-sigma trilepton ATLAS excess (and a confirmation by GAMBIT), the gamma ray excess at the center of our galaxy seen by Fermi-LAT, as well as the antiproton excess observed by AMS-02.

In their model, the LSP is a bino-like neutralino and another, wino-like neutralino should exist with the mass of \(160\GeV\). \(\tan\beta\) should be greater than ten. This paper may be viewed as a counter-argument against the recent efforts to claim that the central galactic gamma-ray excess was "due to some boring pulsars" only.

At any rate, dark matter of mass \(60\GeV\) within supersymmetry is still plausible and somewhat recommended by some observations, much like the NMSSM-like new Higgs of mass \(96\GeV\). I can't tell you the probability that these particles exist – it depends on lots of priors and methodology – but I am sure that it is just wrong and prejudiced to behave as if these probabilities were zero.

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