Friday, 24 May 2013

Planck 2013 Day Five Live Blog 3

Lunch ran long, so I missed the first  two talks.

3:00pm: Leszek Roszkowski, "Status of constrained SUSY in light of LHC data"

To quote one of the slides: "SUSY cannot be experimentally ruled out."

Do I really need to say any more?

Oh, another good quote.  On the topic of fine tuning/naturalness: "I prefer to follow what  the data implies, rather than theoretical prejudice."  Really.

An argument that there are GUT relationships among the parameters that take a very simple form, in a sense allowing more freedom at the high scale.  That's not a ridiculous point of view, indeed it is worth looking at, but with the current status it doesn't excite me.

Q&A: Some discussion on the question of chi-squared fits in the presence of fine tuning.  I think I remember a paper from a few weeks ago arguing, essentially, that all SUSY chi-squared estimates were wrong as they did not include setting the electroweak scale, which I think is what was being asked here.

3:30pm: Alberto Casas, "Charginos and neutralinos, Higgs physics and LHC"

It looks like that last point might actually be addressed in this talk.

Indeed, the idea is to use Bayesian analysis, which automatically penalises fine tuning.  Rather than treat the SM parameters as inputs, in particular solving the μ parameter from the Z mass, include the μ parameter in the fit.  This introduces a Jacobian term that is the fine tuning.  This gives us some universal factors for all MSSM models, including a penalty for large tan β.

Beyond the CMSSM, there is the question of light fermions (relative to the scalars).  In particular, look at the phenomenology of light charginos and neutralinos.

Light charginos can enhance Higgs to diphotons.  Constrained to be no more than 10% for tan β > 5; but larger at smaller values.  Such regimes have been traditionally disfavoured, but might still be worth considering; indeed might be less explored.

Some examination of DM and LHC constraints on five benchmark points.  The results are not clear from the slides.  Light charginos can be relevant to the WW excess.  Conclusion seems to be that light inos can be probed either by Xenon1Ton, WW measurements or like-sign lepton searches.  But the extent to which this is true is fuzzy.

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