Magic Monday Journal Club

12th November 2013

Back to the  main page


A family of WISPy Dark Matter Candidates

by J. Jaeckel

Joerg makes a summary of models where the dark matter emerge from a massive Goldstone boson. Its relic is given by a non-thermal mechanism (called «misalignment mechanism»). When the symmetry in play is a family symmetry (the goldston bosons are then called «familons») there are other constraints arising from its lifetime, rare decay processes or thermal processes. I let you go directly to the Figure 3 that is a good summary of the work.  As you can see, dark matter has to be quite light in this case, and generating quite a large vev. You can find the annoted version of the paper here.

Impersonating the Standard Model Higgs Boson: Alignment without Decoupling

by M. Carena, I. Low, N.R. Shah, C. Wagner

In models with an extended Higgs sector there exists an alignment limit, in which the lightest CP-even Higgs boson mimics the Standard Model Higgs. The alignment limit is commonly associated with the decoupling limit, where all non-standard scalars are significantly heavier than the Z boson. However, alignment can occur irrespective of the mass scale of the rest of the Higgs sector. In this work we discuss the general conditions that lead to "alignment without decoupling", therefore allowing for the existence of additional non-standard Higgs bosons at the weak scale. The values of tanβ for which this happens are derived in terms of the effective Higgs quartic couplings in general two-Higgs-doublet models as well as in supersymmetric theories, including the MSSM and the NMSSM. Moreover, we study the information encoded in the variations of the SM Higgs-fermion couplings to explore regions in the m A −tanβ parameter space.

Searching for Dark Matter at LHC with mono-Higgs production

by A.A. Petrov and W. Shepherd

The authors consider LHC searches for dark matter in the mono-Higgs channel using the tools of effective field theory. This channel takes unique advantage of the presence of SU(2)L breaking in those operators to avoid the need for any initial-state radiation, usually necessary to tag the production of invisible particles. They find that sensitivities to parameters describing dark matter interactions with standard model particles are comparable to those from monojet searches for a subset of the usually-considered operators, and we present for the first time bounds from collider searches on operators which couple DM to only the Higgs field or its covariant derivatives.

Electric Dipole Moments as Probe of New Physics

by M. Pospelov and A. Ritz

The authors review several aspects of flavour-diagonal CP violation, focussing on the role played by the electric dipole moments (EDMs) of leptons, nucleons, atoms and molecules, which consitute the source of several stringent constraints on new CP-violating physics. We dwell specifically on the calculational aspects of applying the hadronic EDM constraints, reviewing in detail the application of QCD sum-rules to the calculation of nucleon EDMs and CP-odd pion-nucleon couplings. they also consider the current status of EDMs in the Standard Model, and on the ensuing constraints on the underlying sources of CP-violation in physics beyond the Standard Model, focussing on weak-scale supersymmetry.

Possible Evidence of Thermodynamic Equilibrium in Dark Matter Haloes

by J. Davidson, S.K. Sarker and A. Stern

The authors took 8 galaxies and infer a fit of rho(phi) [density as function of the gravitational potential] from the velocity curves extracted from the THINGS data. Surprisingly (or not) the observe a behavior in agreement with the description of a single-component Boltzmann gas.A look at formulae (1) and (2) and then directly the figure 4 give you the main point of their work. They also compare their fit with an effective theory in the table 1 and their results seems quite interesting. They do not need to make any hypothesis on the DM distribution or baryonic content of the galaxies. It could be the first hint of a self interacting dark matter bath.

You can find the annoted version of the paper here.

Reflections on the direct detection of particle dark matter

by R.H. Sanders

R.H. Sanders (a MOND afficionado) explains in this 4 pages why the «dark matter paradigm» is not a «scientific theory» because not falsifiable. Philisophical discussion, some interesting points cocnerning the sociology of Physics community (there is something «a la « Peter Woit in the Stirng field, same arguments used against the stringy guys). A little recreation for your metro transport.  You can find the annoted version of the paper here.

Isospin-violating dark matter from a double portal

by G. Bélanger, A. Goudelis, J.C. Park, A. Pukhov

As predicted in the last Journal Club, one of (the first in fact) the several paper that will appear trying to conciliate LUX and CDMSSi/CoGENT/DAMA/CRESST signals (even if the authors concentrated only on CDMSSi in their work). Due to the quick released of their manuscript, I suspect the authors to have work on the XENON/CDMSSi reconcilation and then decided to publish it after the LUX results. Indeed, you can directly jump on their figure 4 which is a good summary of their work: light dots are XENON compatible (some points survives) dark dots the LUX ones... Tensions are quite imortant now (unfortunateley for light DM fans). The interesting point of the paper it is that contrary to preceeding isospin violation papers, they build a coherent model with two portal (Higgs and Z’) and their interference plus specific properties of each of the portal (especially how they act on neutron vs proton) makes the miracle (fn/fp=-0.69, Xenophobic DM). They took serioulsy into consideration the isotopic composition of the experiments. You can find the annoted version of the paper here.

Planck’s law and the light quantum hypothesis

by S. Bose (1924)

In 1923 Bose submitted this paper to «Philosophical Magazine» which were the PRL of the time. It was rejected immediately. In despair, he wrote to Einstein and asked to him if he can translate it in german as he wrote «I do not know sufficient German to translate the paper» and submit it to «Zeitschrift fur Physik». In this paper, he rederivates the Planck formula without any pseudo-classical interpretation or motivation (Wien’s law..) but only  with pure quantum considerations. The article is incredibly modern and can be considered as the first quantum-thermodynamics paper. The help of Einstein can justify the name «Bose-Einstein statistics» to the last equation of the paper.  You can find the original paper here.