MeV-GeV γ-ray telescopes probing axino LSP/gravitino NLSP as dark matter in the μνSSM

Abstract

In R-parity violating supersymmetry, the gravitino as the lightest supersymmetric particle (LSP) is a good candidate for dark matter, with the interesting characteristic to be detectable through γ-ray telescopes. We extend this analysis considering an axino next-to-LSP (NLSP) as a coexisting dark matter particle contributing with a detectable signal in the γ-ray spectrum. The analysis is carried out in the framework of the µνSSM, which solves the µ problem reproducing simultaneously neutrino data only with the addition of right-handed neutrinos. We find that important regions of the parameter space can be tested by future MeV-GeV γ-ray telescopes through the line signal coming from the decay of the axino NLSP into photon-neutrino. In a special region, a double-line signal from axino NLSP and gravitino LSP is possible with both contributions detectable. IntroductionGravitino (ψ 3/2 ) LSP or axino (ã) LSP are interesting candidates for dark matter (DM) in the framework of supersymmetry (SUSY). In addition, in SUSY models where there is Rparity violation (RPV) these particles decay with a lifetime longer than the age of the Universe, producing a line signal potentially detectable in γ-ray telescopes. This was analyzed for the gravitino LSP in Refs. [1][2][3][4][5][6][7][8][9][10][11] in the context of bilinear/trilinear RPV models [12], and in Refs. [13][14][15][16] in the 'µ from ν' supersymmetric standard model (µνSSM) [17]. Similar analyses for axino LSP in bilinear/trilinear RPV models were carried out in Refs. [18][19][20][21][22][23][24][25][26][27].In a recent work [28], we analyzed a multicomponent DM scenario with axino LSP and gravitino NLSP. This is a decaying dark matter (DDM) scenario, where the gravitino in addition to the RPV decay channel into photon-neutrino, also undergoes an R-parity conserving (RPC) decay into axion-axino. The analysis was carried out in the framework of the µνSSM, where couplings involving right-handed neutrinos are introduced solving the µ-problem and reproducing simultaneously the neutrino data [17,[29][30][31][32]. A brief discussion and bibliography about the interesting phenomenology associated to the µνSSM, can be found in Ref. [28], where it was shown that significant regions of the parameter space of the model can be probed through a line signal coming from the axino decay. A doubleline signal as smoking gun through the further contribution of the gravitino decay is also possible in a subset of those regions.Here we want to extend our previous work, analyzing the opposite DDM scenario where the gravitino is the LSP and the axino the NLSP. Their masses, although model dependent can be of the same order in several realistic scenarios [33][34][35][36][37] such as in supergravity, and therefore if the axino (gravitino) is the LSP the gravitino (axino) becomes naturally the NLSP. As a consequence, the NLSP decays into the LSP plus an axion. In this not yet explored RPV scenario with gravitino LSP and axino NLSP, we will study its cosmological properties as well as the associa...

Portal Effective Theories. A framework for the model independent description of light hidden sector interactions

“…Axinos can be produced for instance by gluon fusion or in neutralino decays, which are useful mechanisms for searches in beam dump experiments or at colliders, and can be naturally in the MeV mass range, see e.g. [280].…”

Searching for supersymmetry: the μνSSM

“…In the case of the most popular axion models, KSVZ [110,111] and DFSZ [112,113], this scenario was analyzed in Ref. [32]. The conclusions using Fermi -LAT constraints are that axino masses must be smaller than about 3 GeV.…”

“…In Refs. [31,32], the interesting possibility of a multicomponent DM scenario made of gravitino and axino was analyzed. If the axino is the LSP, interestingly a gravitino NLSP can live enough as to contribute to the relic density.…”

“…Actually, it is also related to the existence of SUSY decaying DM candidates in the model. This is the case of the gravitino [27][28][29][30][31], or the axino [32], with lifetimes greater than the age of the Universe. The key to this is that gravitino (axino) interactions are suppressed not only by the Planck (Peccei-Quinn) scale, but also by the small RPV parameters.…”

The new $$(g-2)_\mu $$ result and the $$\mu \nu $$SSM

“…The low decay width of the LSP due to the smallness of neutrino masses is also related to the existence of possible candidates for decaying dark matter in the model. This is the case of the gravitino [68][69][70][71][72], or the axino [73], with lifetimes greater than the age of the Universe. It is also worth mentioning concerning cosmology, that baryon asymmetry might be realized in the μνSSM through EW baryogenesis [74].…”