Magic Monday Journal Club

7th October 2014

Back to the  main page

 



Haaaa, was great to see all of you around after the world trip of your favorite Magicians. A lot of discussion, and participations. So thank you to Roberto, Ulrich and Giorgio for having presenting papers, it gave us some fortunate holidays!!! Here are the works we presented



NMSSM with a singlino LSP: possible challenges for searches for supersymmetry at the LHC

by U. Ellwanger and A. M. Teixeira


What????? A paper about the NMSSM with Ulrich as an author?? Are ypou kidding me?? (that was the cynical par Ulrich asked me to contribute). More seriously, a solid and interesting work, and professor Ellwanger himself will be the best to describe it. in his words:

A light singlino with a mass of only a few GeV in the NMSSM can reduce considerably the missing transverse energy at the end of sparticle decay  cascades, if the NLSP (typically a bino-like neutralino) decays into such  a light singlino and a Higgs boson with a mass just below the NLSP mass. Then all sparticle decay cascades end up in a Higgs boson (a lighter  NMSSM-specific scalar, or the SM-like Higgs) plus a soft singlino. First, in this scenario constraints from present searches for supersymmetry  and/or for events with several hard b-jets still allow for squarks and gluinos both with masses below 1 TeV. Second, boosted Higgs pairs can then be visible at the 13/14 TeV LHC in bb/tautau final states..


Testing Electroweak Baryogenesis with Future Colliders

by  D. Curtin, P. Meade, C.-T. Yu


The authors examine the possibility of testing electroweak baryogenesis at colliders. In particular they study whether signs of a strongly first order phase transition can be uncovered even in the most pessimistic scenario. To do this they construct a "nightmare scenario" that generates a strong first-order phase transition as required by EWBG, but is very difficult to test experimentally where only a heavy singlet scalar is added to the Standard Model. They show that a 100 TeV hadron collider is both necessary and possibly sufficient for testing the parameter space of the nightmare scenario that is consistent with EWBG.



LHC prospects for minimal decaying Dark Matter

by G. Arcadi, L. Covi and F. Dradi


The prospect of LHC detection of a simple scenario of decaying DM, coupled with a scalar field charged under the SM group have been discussed. This simple model can be embedded in theoretically motivated frameworks, like SUSY models with gravitino or singlino DM. For masses of the scalar field in the TeV range limits from DM Indirect Detection impose very suppressed coupling for these interactions such that the DM is produced by the decays of the scalar field, either in equilibrium (freeze- in) or out-of-equilibrium. The scalar field can be efficiently pair produced at the LHC such that it results long-lived with respect to detector scales and thus can be detected through displaced vertices and/or metastable tracks. A systematic approach, altough not yet relying on a detector simulation, for determining the number of expected events of this type is shown. In particular the prospects of a contemporary LHC detecion of the decays of the scalar field and Indirect Detection of the DM decays is investigated, since in this scenario is possible to completely predict the parameters of the model. This result can be achieved for masses of DM below 10 GeV and mass of the scalar up to 2.2 TeV, in case the latter is color charged. In the case that the scalar interacts only electroweakly is mass reach decreases to 1.4 TeV and ID constraints already exclude DM masses above 1 GeV.




Planck intermediate results. XXX. The angular power spectrum of polarized dust emission at intermediate and high Galactic latitudes

by PLANCK collaboration


Planck finally came out of the closet.  They show that the galactic dust polarization fraction in the BICEP window is larger than estimated by BICEP, as previously suggested by some theorists. This implies that the dust alone can account for the signal strength reported by BICEP, without invoking gravitational waves from inflation.



No role for neutrons, muons and solar neutrinos in the DAMA annual modulation results

by DAMA collaboration

and

Comment on “Fitting the annual modulation in DAMA with neutrons from muons and neutrinos”

by  P.S. Barbeau , J.I. Collar , Yu. Efremenko, and K. Scholberg


Life was great. Flowers were smiling. Birds were singing Celine Dion. The DAMA result was explained whil my granny finished putting in pot her last strawberry marmalade. And suddenly. The word went to hell when DAMA collaboration and Collar’s friends come to explain us that the nice explanation of the combined muon/solar neutrino double modulation proposed by the young J. Davis 2 months ago is in fact not at all realistic. Indeed, he supposed a 1000 m3 environment around the shield of DAMA that could be source of neutrons expulsed by cosmic muons, or induced solar neutrino. In fact, the effective area is less than 1 m3 as confirmed these two papers. So, some 4 orders of magnitude  missing to explain their effect.  In any case, as underlined professor Goodsell in our last meeting, a conjunction pointing EXACTLY to the 2nd of June, dates when the earth and sun reaches their maximal relative velocity can be dubious. I admit too. Explanation should be Galactic one. You can find the annotated papers here and there.




Quantitative study of the AMS-02 electron/positron spectra: implications for the pulsar and dark matter properties

by S-J. Lin, Q. Yuan, and X.-J. Bi


So. «This is exciting as it is the first time in the history of High Energy Cosmic Rays (sic!) that we observe a decrease in the the positron fraction spectrum» [Ling, this Nobel prize who now spoke for AMS]. Of course, nobody could avoid last week the AMS seminar at CERN, where you can find here a nice summary with plots even not presenting in the published PRL paper. So, this chinese group jumped on the opportunity to tell us (what we already knew) with real equations and real codes and plots that is is quite impssible to distinguish this source as a pulsar source or a DM interpretation. A glance at their Fig. 2 should be sufficient to understand the situation. Look at the annotated version there.



Stellar Evolution Bounds on the ALP-Photon Coupling: new Results and Perspectives

by Maurizio Giannotti


Axion-Like Particles (ALPs) searches are of course of primordial importance, especially nowadays when some alternative scenario for dark matter (and even some dark matter signals, cf. the 3.5 keV line) can imply the presence of such element in a minimal extension of the SM. In this work, the authors give the best limit to an Axion-like coupling , coming from the Helium Burning (HB, or Hyperblic Branch) stars. Just have a look at its Fig.1 and should be sufficient. An annotated version of the paper can be found there.



COMMENT ON \DARK MATTER SEARCHES GOING BANANAS: THE CONTRIBUTION OF POTASSIUM (AND CHLORINE) TO THE 3.5 KEV LINE"

by E. Bulbul, M. Markevitch, A. R. Foster, R. K. Smith, M. Loewenstein, S.W. Randall


Our field is beginning to full itself of comments, comments on comments and all this «physics2.0-poke-me-if-you-like» stuff. I have to admit I am far to be a big fan of that (no twitter, and a dead facebook page). However, we have to follow what is rolling around if one has to have something to say at the cafeteria (except the Polish victory on Germany-football). In this paper, in one word, the Bulbul team claims that the Profumo analysis use an approximation (her formulae (1)) clearly not valid in the present case. I heard around me (Hooper + Weniger in my last workshop after some beers) that Profumo study indeed does not really seems reliable. So, in other words, stay tuned (or not). You can find an annotated version of the paper there.