Wednesday, 27 May 2015

Planck 2015 Liveblog: Day Three Session Three

Today was the day of the conference excursion, to the Dodona archeological site/amphitheatre.  So we have only three sets of talks, finishing with the second set of parallel talks.  Thanks to the excursion, we're back on schedule, more or less, and I'm going to try changing sessions after three talks.

5:00 pm: "Supersymmetry and Naturalness", Csaba Balazs

Observable evidence of SUSY: got a job!

Why are we obsessed with SUSY?  Are we really obsessed with naturalness, and have just mistaken SUSY as the best example of that?

Naturalness is simply the statement that physics at different scales are well-separated.  To be quantitative, we must define a fine-tuning measure.  Use Barbieri-Ellis-Giudice measure for concreteness, to match with literature.  Important questions though; why is it a derivative?  What are we taking the derivative of (mZ, mH, v, ...)?  What are we taking the derivative with respect to (tan β, B, ...)?  Derivative or logarithmic derivative or ... ?

Bayesian motivation and answer for all these questions.  If e.g. theory predicts mZ (μ), this function is invertible: μ (mZ).  In Baysian analysis, using delta-function likelihood (since mZ well-measured) then evidence is just BEG measure.  This also makes it easy to generalise to multi-parameter theories (inputs and outputs), since replace derivative with Jacobean.

Result is that even CMSSM has ~few percent fine tuning regions.  CNMSSM is even better.  Extends up even to m0 ~ 10 TeV.

Why truncate plots at 16 TeV?  Limits of scan.  No fundamental reason.  Question remains how high this can go.
Regions of low fine tuning at EW scale fine tuned at high scales?  Likely.  Some degree of subjectivity in formalism.
Comment: frequentist interpretation: Jacobean is covariance matrix.
Low fine-tuning is focus point, small μ - yes.
Additional data would make fine tuning worse, remove these low-tuned regions - yes, upcoming work.

5:25 pm: "What is a Natural SUSY scenario?", Jesus Moreno

Ten minutes late already, which will make switching to the next session later trickier.

Naturalness given as caused by top loops.

Standard Lore is that stops should be light to have natural SUSY.  Also very light Higgsinos, not too heavy gluinos.  However, these are done in various approximations that are not robust.  We should not restrict ourselves to the leading-log approximation.  We also want limits in terms of physical masses, not Lagrangian parameters.

As known, focus point has heavy stops without paying much of a price in naturalness; Higgs runs insensitively to m0, while stop mass much more dependent.

Should also consider other fine tunings, e.g. that associated with large tan β.

Scan spectrum and express limits by computing BEG fine tuning.

I kind of lost interest in the second half of this talk.

6:10 pm: "Particle Cosmological Probes on Light Dark Matter", Kenji Kadota

I skipped a talk to get here on time.  Dark matter below DD range, with an electric dipole moment.  Constraints exist for LEP/LHC; consider extension to ILC and also supernovae.

ILC search based on clean mono-photon search.  Backgrounds (invisible Z, W) controllable.  SNe based on cooling constraints.  Collider gives upper bound of ~ 0.01 for dipole moment (in TeV-1),  Supernovae constraints exist at much lower moments, excluding between 10-5 and 10-6.

Also constraints from helioseismology.  Uncertainties not trivial, but easy to exceed them with DM so constraints can be made.

There's too much text on the slides that I literally cannot read, because it is too small.

I'm skipping the next talk, which is about inflation.

6:50 pm: "Classification of Non-Thermal Dark Matter Production Mechanisms", B Zheng

7:10 pm: "Higgs Dark Matter from Warped Extra Dimensions", A Ahmed

7:25 pm: "Interplay and Scale Dependence of Neutralino (Co)Annihilation", P Steppeler

Planck 2015 Liveblog: Day Three Session Two

The second session today is ahead of the curve, with two talks I'm somewhat interested in.  Unfortunately the exception is the middle talk.  We are, of course, almost 30 minutes over time.

Planck 2015 Liveblog: Day Three Session One

Day three starts with a slightly odd session (for me); one talk I am interested in followed by three I am not.  I didn't finish writing my own talk yesterday, so I guess that works out for me.

Plank 2015 Liveblog: Day Two Session Four

The final session of the day is the first parallel session of the conference.  According to the conference timetable, the first talk was supposed to be at 5pm.  Even if we hadn't been running late, that would have left us with no time for the coffee break; or to put it another way, the schedule had an error.  Which isn't exactly a surprise for thie conference.  As it is, it looks like this session will start at 5:40pm, and so probably not finish till 8.

Given how bad timekeeping has been at this conference, I'll mostly stay in this session.  There is one talk at the end of another session I want to attend, though.

Tuesday, 26 May 2015

Planck 2015 Liveblog: Day Two Session Three

The first session after lunch looks pretty dull too.  Also, we are already starting five minutes later.

Planck 2015 Liveblog: Day Two Session Two

We progress to the second day of the conference.  I decided to skip the first session of the morning, as none of the talks interested me and I'm still writing my talk.  The second session, however, has some stuff on neutrinos and unification that could be interesting.

Planck 2015 Liveblog: Day One, Session Four

The final session of the first day is back to technical subjects.