Tuesday, 21 May 2013

Planck 2013 Day One, Live Blog 2

A fourth parallel session of the day.  Conference website.

4:30 pm: Howie Haber, "The MSSM Higgs Mass Revisited"

Based, it seems, on a misunderstanding extant in the literature.  This could be fun!  How robust is the Higgs mass calculation in the MSSM?

Of course, the low tree-level mass in the MSSM is because the quartic couplings are related to gauge couplings.  The famous tree-level problem!

The role of loop corrections realised as early as 1991!  Two loops now done.  Plenty of plots in the literature showing the implications of the measured Higgs mass on MSSM parameters.  In particular, a light stop is acceptable for TeV-scale heavy stop and mixing parameters.  But this is still in tension with naturalness, and only gets worse in specific models.

Hah, looks like we just killed the speakers with feedback.  That's funny in a depressing way.  Okay, fixed now.

Problems include the need for tachyonic squark masses in GMSB at high scales, or just getting the mass at all in the CMSSM; this comes back to the problems with At.  At heart, this all relies on the loop corrections; are they well understand?

Heinemeyer et al in 2011 analysed that the seesaw-extended MSSM corrections to the Higgs mass.  Some people have interpreted there results as suggesting the very heavy right-handed neutrinos could contribute corrections of a few up to 5 GeV; the claim of this talk is that this in not true, decoupling works as you would expect.

In particular, for the seesaw-extended MSSM the correction of the right-handed neutrinos is negligible.

One relevant point already seems to be the need to be consistent in the use of scales in these loop calculations.  This means most parameters in the one-loop expressions take their tree-level values.  In general, we've quickly moved deep into the subtleties of renormalisation group theory.  But the point seems to be that since the Higgs mass is a physical observable, we should use a renormalisation scheme that is defined in terms of observables; not DRbar, a commonly used choice.

Q&A: Another simple approach is to integrate out the heavy neutrinos, and get the same result.  In such a mechanism, you can use DRbar, which seems to fit with the general correct approach in such a renormalisation scale.

5:00 pm: Martti Raidal, "Fermi 130 GeV gamma ray line as an indirect signal of DM"

DM is an unambiguous solution of BSM physics.

Cosmology has the same problem as particle physics: the standard model is too good!  (Thanks, Planck satellite!)

The possible DM candidates cover a huge range of masses, 30 to 40 orders of magnitude.  That's just silly.  We don't even know how DM is generated; is there an asymmetry?  Is it thermal?  We just don't yet know.

Detection methods... getting close to the Fermi signal of the title.

A loose/lose error, but that's more acceptable from a Finn than an American.

Fermi-LAT's data is publicly available, which of course how Weniger found the signal.

A quick detour into the AMS-02 confirmation of the PAMELA positron excess.  Some interpretations I have not seen before, which show that 
  • DM must be leptophilic, well known;
  • DM must annihilate to muons (or other dark-sector particles);
  • Profile must be cored.
Would be useful to see results with more modern halo profiles, rather than Isothermal/NFW.

Back to the Fermi signal, the double-peak structure increases the significance significantly.  The claimed global significance here is 4.5 to 6.5σ; that seems pretty dubious to me.

Now, we can contrast DM vs astrophysical interpretations by looking at other possible sources; in this case, galaxy clusters.  The same double-peak structure is observed, at lower statistical significance but above 3σ; and the observed flux correlates with the expectations.  I again doubt the claimed significance, given that only a few photons make up the signal.  This test also will not discriminate vs systematic problems with the detector that have attracted a lot of attention later.

Looks like that last point will be addressed; in essence, that is a question more for the Fermi collaboration.  As theorists outside the group, we have access to the public data but not all the details of the detector response.  We should look for consistencies in the data.  The double-peak structure is being  strongly emphasised here.  Of course, the collaboration has been pessimistic, and may well have good reasons.

It is useful to compare, then, with other data.  HESS-II will get there soon; this talk is playing the AMS-02 card.

Q: What about trial factors?  A: Essentially, no.  It seems that the significances are local, which does explain what we saw above.  I think this is Dan Hooper, who has different irons in the fire for indirect dark matter signals.

Q: Sharp dips in signal just before/after double-peak structure.  Is this relevant?  A: No, background is estimated as simple power law and significance taken relative to that.

5:30 pm: Anupam Mazumdar, "Visible sector models of inflation and curvaton"

Another inflation talk.  I didn't have enough coffee during the break.

Inflation must end, and then we must create SM degrees of freedom.  How?  There must be a connection to particle physics somehow.

ΛCDM, simple model with 6 parameters, is still the best description we have.  Sure, there's a small tension at for multipoles, but it's not big.

The generic predictions of inflation from all the way back to the 1980s have been stunningly confirmed.    There does not seem to be any reason to go beyond single-field inflation in the data beyond the low-multipole anomalies.  Nor is there any evidence for dark/hidden radiation.  All of this is very useful but does not shed light on the creation of matter and the end of inflation.

In particular, while it is possible to fit the Planck data with an arbitrary inflaton field (for a suitably chosen potential), the production of SM states cannot.  For example, a singlet in String theory can and will couple to one of the many, many hidden sectors; and produce too much energy in those sectors on reheating.

The model details are rushed from lack of time, but it all seems to be a bit arbitrary to me.  But apparently they can be tested/ruled out both from cosmological and LHC observations.

Q: What about gauge singlets?  A: You need to know the full gravity sector.  Ooh, disagreement!

Q: Initial condition problem?  A: Need quantum gravity to properly answer that question.

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