Magic Monday Journal Club

March the 14th  2014

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The coffee was soooo great!! I cannot even talk about the cakes!!!! Thank you a lot Mark for having replaced with sucess the role of our missing magician..

The quest for an intermediate-scale accidental axion and further ALPs

by A. G. Dias, A.C.B. Machado, C.C. Nishi, A. Ringwald and P. Vaudrevange

This paper proposes models of a QCD-axion and/or axion-like particles (ALPs) from breaking several (approximate) global symmetries at an intermediate scale, in order to fit dark matter, the 3.55 keV line, and other astrophysical hints. After BICEP, this is the only scale that remains plausible for axion dark matter. By imposing discrete symmetries ?? la Heterotic orbifold models (however without a string in sight in this paper) they determine the first terms in the lagrangian at which the U(1) symmetries are broken and thus predict the mass of the axions once the vevs of extra Higgsing fields are set.  However, the most striking thing about the paper are the plots, which include constraints on the ALP parameter space that were previously missed or ignored from Quasar polarisation in 1204.6187 -- and claim to effectively rule out the ALP explanation of the gamma-ray transparency of the universe and also the X-ray excess in the coma cluster: disaster!

Generating X-ray lines from annihilating dark matter

by E. Dudas, L. Heurtier and Y. Mambrini

Hey, hey hey.. It is not because it is one of the magician’s work that we should omit it!! Honestly, that’s a cool one. The idea that all the  model presented to fit with the 3.56 keV line from XMM Newton observations were based on unstable dark matter with a lifetime of around 10^28 seconds (except for an «eXciting DM). Annihilating DM were pushed away on effective arguments which are simply too naive.  We showed in this work that an approach with the exchange of a (pseudo)scalar of around 1-30 MeV is completely possible and can also give the right amout of cosmological DM through its equilibrium with a right handed neutrino. We even give a dynamical version of the model. The annotated version of the paper can be found around there.

Millisecond pulsar interpretation of the Galactic center gamma-ray excess

by Q. Yuan and B. Zhang

Bha, at least an alternative for the Hooperon, we cannot complaint. Whereas the authors of the DM interpretation of the FERMI bump around 1-3 GeV turn on TV shows, media, even Huffington Post and Le Monde claiming that we «discovered the dark matter», and even knowing the USA system and its necessity for quick (and easily forgetable) claims, we have to admit that an alternative of astrophysics nature is a piece of holidays. The Chinese origin team proposed that a population of millisecond pulsar (MSP) can fit the excess observed by FERMI if they have a softer spectrum that the one took by Hooper et al. to affirm that  MSP cannot explain it. Around 13 000 of them are necessary to have the sufficient total luminosity, but this seems apparently quite reasonable given  other  population of X-binaries system around. The population could also respect a spatial distribution respecting the one observed by FERMI. So let’s stay tuned!!! You can find an annotated version of the paper here.

1403.4852, 1403.7028 and 1403.8049

These papers all claim to reconcile the Planck and BICEP2 constraint on/detection of r by adding extra radiation at the CMB era, variously interpreted as "sterile" neutrinos (that are nevertheless thermalised) or thermal axions. The data can apparently be matched by adding the equivalent of one effective extra neutrino -- from either a sterile neturino of 0.5 eV or an axion -- and the best-fit value becomes r ~ 0.2, ns ~ 1: i.e. a scale-invariant spectrum!

First Axion results from the XENON100 experiment

by XENON collaboration

Nice limit released by the XENON100 team. They succeed in giving the strongest constraint on the electric axion-like coupling gAe. Their limits is gAe < 7.7 10^-12 at 90% CL for the solar axions and less than 10^-12 for the cosmological ones. Let’s wait for the LUX results on the subject!! You can find an annotated version of the paper around there.