Magic Monday Journal Club

1st December 2014

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That was the nice articles we discussed this Monday, after having watched nice photos of my African Safari, and a video of my Bungee Jump in Victoria Falls (110 meters!!!!). Yes yes, not only Physics count in life!!!

Postinflationary Higgs relaxation and the origin of matter-antimatter asymmetry

by  A. Kusenko, L. Pearce and L. Yang

The paper presents a novel mechanism for baryogenesis. The non-equilibrium condition is ensured by the Higgs field relaxing down to its minimum after inflation. Coupling to the heavy right handed neutrino to the Higgs field sources lepton number generation in the early universe. One can obtain the correct baryon abundance for a reasonable choice of parameters. 

Rare exclusive decays of the Z-boson revisited

by  T.-C. Huang and F. Petriello

There's been a lot of interest lately in exclusive Higgs decay to quarkonium states, e.g. h -> J/psi + photon. This paper makes precise computations of the branching fractions for related processes of Z exclusive decays to quarkonium + photon. It's not a fascinating read, but a useful reference to learn the relevant formalism.  

A Tale of Tails: Dark Matter Interpretations of the Fermi GeV Excess in Light of Background Model Systematics

by F. Calore, I. Cholis, C. McCabe and C. Weniger

The «tale» of the Galactic Center continues his road, opening everytime new perspectives.  This time, Christoph (Weniger) et al. drive us toward new final states, mainly WW and hh which can fit this Galactic Center, especially if they are produced almost at rest in the neighborhood of the Galaxy Center (so near their mass threshold) from annihilating dark matter. Indeed, in this case, the phioton produced by the subsequent decays of hh or WW are quite soft, and seems to have features corresponding the observation made by FERMI. The authors also took into consideration the effect of bremsstrahlung  which can affect considerably the result. You can just jump on their Fig.3, and you will see the new open world.. For an annotated version of the paper, just have a look there.

Z’ Mediated Dark Matter Models for the Galactic Center Gamma-Ray Excess

by D. Hooper

I am glad that Dan thanks me in this paper (with an approximate syntax, but ok) as this paper came from a discussion we had in a workshop in Korea about the limits of his previous paper on vectorial/scalar/pseudoscalar mediators to explain the GC excess. In 2 words, when you exchange a vectorial mediator, to avoid limits from LUX, one have to look for axial couplings (only Spin Dependent interactions). But, the price to pay is that the cross section is mass reduced, and the velocity part (p-wave) dominates the annihilation channel at decoupling time, rendering impossible to fit the GC excess and the PLANCK data. The way to escape it? Complicated, Dan proposes in this paper a leptophylic (to avoid LHC constraint) axial Z’ coupling to third generation of quarks (to avoid LUX constraint). He also proposed some anomaly-free realization of such constructions, but honestly.. Hard to believe in such a strange Z’ (my two cents..). You can find an annotated vzersion of the paper there.

Stability constraints of the scalar potential in extensions of the Standard Model with TeV scale right handed neutrinos

by C. Coriano, L. Delle Rose and C. Marzo

Ok. Bha. Something maybe not so useful but who knows.. In any case, I like the work and their recipe: You take a right handed neutrino, and couple it to a scalar whose vev will generate the Majorana mass. Up to now all is perfect. You generate the see-saw mechanism and  want to know if for a TeV mass for the vev of this new scalar (TeV see-saw) up to which scale the Higgs potential is still stable. As you can understand easily, two mechanisms going in opposite directions : the scalar (hmmm, good!!) and the right handed neutrino (hmmm bad!!) compete to increase/decrease the value of the quartic coupling. At the end? Few parameter space allowed, just look at their Fig.1. For an annotated version of the paper, run there.

Energy Neutrinos from Astrophysical Sources

by S. Razzaque

Veryyyyyy good experimental talk about the stauts/results/issues/prospects of Icecube by Soebur Razzaque I saw at the Dark Side of the Universe conference in Cape Town last month.. Just read it with pleasure before sleeping.

Neutrinos on Ice: Detection Balloon Heads to Antarctica

by Katie Mulrey

This Katie Mulrey is a PhD student in the ANITA project whose aim is to measure unltra energetic neutrino «a la» Pierre Auger experiment, (which means reaching energies of the order of 10^10 GeV) from their interaction with the ice. Ultra High Energy neutrinos should emit a radio-wave signal which will be measured by a baloon, launched on top of the South pole this Month. Katie is making a blog of the adventure, and it is at the same time very instructive and quite funny, especially their life with the pinguins. So contrarily to PINGU, the Icecube extension that should look for ~100 GeV neutrino, ANITA will help covering the ultra High energy range. PINGU +  Icecube + ANITA = 1 GeV - 10^10 GeV spectrum of neutrino in the next 3 years!!