Magic Monday Journal Club

March the 31st  2014

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Thank you for all of you for your participation, and special thanks to PLANCK members Olivier Perdereau for his presentation and Francois Couchot for its very useful comments and discussions..

Comments on BICEP2 B modes results

by O. Perdereau (PLANCK/LAL)

Olivier gave us a very nice critical (in a positive way) presentation on the BICEP2 results and the possible loopholes of the analysis. Wit F. Couchot (LAL) the discussion was animated, and conclusion was that we should wait the PLANCK results at the end of the year (specially concerning dust measurement) to have any kind of definitive conclusion on BICEP claims (especially on the specific value on r). Do not hesitate to have a look on the slides.

Constraints on the Higgs boson width from off-shell production and decay to ZZ -> lll’l’ and ll νν

by CMS collaboration

CMS puts the 95% limit on the total Higgs width at 4.2 the SM width. This is surprisingly strong, give the SM Higgs width is only a few MeV. At present,  this result is not  constraining  seriously theories beyond the SM, however in the future this kind of analysis may become very important to put limits on exotic Higgs decays. 

The 3.5 keV X-ray line from decaying gravitino dark matter

by N.-E. Bomark and L. Roszkowski

So, after the sterile neutrino, the axion, axino, ALP, non-thermal, moduli, eXciting DM... candidates, the Gravitino comes back. Using R-parity couplings (listed in their formula (2)) the authors showed that indeed, a 7 keV gravitino can lived with the correct lifetime (around 10^28 seconds) to fit the excess of the XMN Newton data measuring a 3.6 keV line from different clusters of galaxies. The price to pay? A relatively low reheating temperature (170 GeV) to ensure that the Universe is at least not overclosed. I would say another decaying candidate which works, waiting for other ones to come for sure. You can find an annotated version of the paper here.

Search for top quark decays t -> qH with H -> γγ  using the ATLAS detector

by ATLAS - de Vivie collaboration

ATLAS puts the 95% limit on the branching ratio of the top quark to the Higgs boson plus light quark at 0.79%.   At present,  this result is not  constraining  seriously theories beyond the SM, however in the future this kind of analysis may become very important to put limits on new sources of flavor changing neutral currents. 

Unitarity Bounds on Dark Matter Effective Interactions at LHC

by M. Endo, Y. Yamamoto

Since several papers (see for instance the Zurek et al of the preceding MMJC) several works insist on the limitation of the effective approach when one wants to give some constraints from the BSM scale. It is true when you have Yukawa like couplings, exchange of a Z’, non-universal couplings, presence of a pole, t-channel exchanged of colored particles, s-channel pole processes etc etc.. and of course, the unitary bounds which are sometimes overlook, should give stringent constraints too. In this paper, the authors shows that indeed, in monojet searches, the unitary bounds should be the one to look at if dark matter mass lies below ~100 GeV. Just a look at their Eq.(3.5) and Fig.(4.1) should be sufficient to catch their results. The annotated version of the paper can be found around there.

Ondes et quantas

by L. de Broglie


The first paper presented in Académie des Sciences, where de Broglie proposed the wave-particle duality. Its way of thinking is tricky but he recovered the quantified of the Bohr-Sommerfeld’s atom making the hypothesis that the electron should behave like a stable wave on a circular orbit. One of the first article combining special relativity and quanta theory. You can find the annotated original paper here, even the original handwritten manuscript there or in the historical section.