Friday, 30 May 2014

Planck 2014 Liveblog: Day Four Session 4

I had to miss the first session after lunch.  For the last parallel session of the conference, I've decided to attend the session with the very general title, "SUSY and non-SUSY phenomenology".

4:40 pm: The price of being SM-like in SUSY, Benedict von Harling

This talk covers an important lower bound on fine-tuning in SUSY models from Higgs couplings.  Specifically, in NMSSM models, the fine tuning is proportional to |1 - r|-1, as Tony mentioned this morning.  So we have a short derivation of this fact, followed by a consideration on what happens at the LHC and ILC, assuming no deviations are seen.

The derivation comes from the fact that the fine-tuning is proportional to the mass of the non-SM like Higgs (the VEV-free one), which needs to be large to suppress mixing.  The mixing is proportional to the off-diagonal mass terms over the diagonal one, and the deviation in the coupling is proportional to the mixing.  As the coupling deviation becomes small, the diagonal mass terms must be large and hence the fine tuning gets worse.

The limits from the LHC are not that great, fine tuning at percent level from Higgs measurements.  Probably worse than direct FT.  From ILC, Higgs measurements can constrain FT to O(0.0005) or so, probably better than any direct measurement.

5:00 pm: Full-Hierarchy Quiver Theories, Leonardo de Lima

RS-type theory, decomposed to multi-site models.

Interestingly, with relatively few sites the coupling of the fermion zero modes to the KK gauge bosons is weaker than the full 5D theory.  This will ease constraints from flavour and EWPO, which are pretty serious.  It also means the resonances are more weakly coupled, but narrower, so not sure what this means for LHC limits.

Indirect limits down to 3 TeV for KK gluon.

5:20 pm: Dilaton domination in the MSSM and its singlet extensions, Lucila Zarate

Theory motivated by string theory: SUSY is broken by the dilaton and mediated by Planck-suppressed operators.  Not a top-down theory, "model independent".  Dilaton breaking is universal (flavour safe) and common in heterotic strings.

For MSSM, theory nicely predictive: it will likely be found or ruled out by LHC14.  Upper bound on soft masses from DM relic density.

MSSM model is two-parameter; GNMSSM is seven.  Unsurprisingly, it is less constrained.

Question: large A-terms leading to charge/colour breaking vacuu?  Checked, but decay time is larger than age of Universe.

5:40 pm: Generation of non-SUSY two-loop RGEs: Automation, Florian Lyonnet

RGEs for general gauge theories have been known for a while, but still difficult to go from general expressions to explicit cases.  Hence full 2-loop RGEs known only for a handful of cases.  Hence a desire to automate this process.

Non-SUSY models are more complicated, due to the lack of SUSY.

My laptop is almost out of power, so I need to truncate this now.

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