Thursday, 29 May 2014

Planck 2014 Liveblog: Day Four Session 1

While I still have things on my mind, I am ready to resume my liveblog of Planck 2014.  Unfortunately I overslept this morning and so missed the first talk of the day.  It looks like we had a talk trying to put axions into models with classically scale-invariant electroweak Lagrangians.  The model involves, in addition to the axion, a pseudo-dilaton and two Higgs doublets.  The main lesson is that in such models, one must address the strong CP problem which requires ultra-weakly coupled scalars.

9:30 am: Naturally light uncoloured but heavy coloured super-particles, Gautam Bhattacharyya

Aim: motivate a spectra of this form to fit the LHC constraints combined with DM/muon magnetic moment/possibly the Higgs diphoton rate.

Usually, I complain about people shouting with microphones.  But this has happened so often here, I think the problem is the sound is just too large.  Gautam's every utterance is reverberating around the room, it would probably be easier to hear him without the mike.

Model uses incomplete GUT multiplets at intermediate scale.  For certain special choices, still get unification.  Intermediate scale relates to SUSY breaking; similar to gauge mediation, but mediation comes not through GUT multiplets but through a colour octet and electroweak triplet.  These choices split the generation of soft masses for coloured and uncoloured particles.

Unification requires the triplet to be heavier than the octet.  Because soft masses go like <F>/M, this means that the coloured soft masses are generically heavier.

Bino and right-handed slepton get no mass from these mechanisms, so must be generated by Planck-suppressed operators.  Then naturally of same order as each other and gravitino.  Large slepton mixing leads to stau NLSP (and gravitino LSP).  Then LHC limits force smuon to be too heavy to explain muon g-2.

For this reason, add standard GUT multiplet messengers.  Give new source of mass for bino, sleptons,  so heavier than gravitino.  But I have to say this rather loses the elegance of the original idea.

10:00 am: Symmetry breaking and light scalars in realistic supergravities, Fabio Zwirner

Goal: study of simultaneous spontaneous breaking of both SUSY and the EW group, and without taking the rigid (non-supergravity) limit too early.  Hope that doing so can address both the various hierarchy problems, and inflation.

No-scale supergravity models: spontaneous SUSY breaking yet zero vacuum energy.  Simplest model has singlet chiral superfield; potential vanishes identically, despite F-term.  Over 30 years old.  In last year, new model that also includes D-term breaking; one chiral and one vector superfield.  Requires appropriate choice of (constant) superpotential.  Not a fine-tuning; related to N=2 theories.

Extension of this theory to include EW gauge group and Higgses.  Model still has SUSY breaking with zero vacuum energy.  Higgs mass vanishes before quantum corrections.  Of course, need corrections for Higgs mass but then get standard contribution to vacuum energy below mass scale of other Higgses, not a complete solution to CC problem.

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