Light scalar WIMP through the Higgs portal and CoGeNT

Abstract

If dark matter (DM) simply consists in a scalar particle interacting dominantly with the Higgs boson, the ratio of its annihilation cross section -which is relevant both for the relic abundance and indirect detection-and its spin-independent scattering cross section on nuclei depends only on the DM mass. It is an intriguing result that, fixing the mass and direct detection rate to fit the annual modulation observed by the DAMA experiment, one obtains a relic density in perfect agreement with its observed value. In this short letter we update this result and confront the model to the recent CoGeNT data, tentatively interpreting the excess of events in the recoil energy spectrum as being due to DM. CoGeNT, as DAMA, points toward a light DM candidate, with somewhat different (but not necessarily incompatible) masses and cross sections. For the CoGeNT region too, we find an intriguing agreement between the scalar DM relic density and direct detection constraints. We also give the one σ region favoured by the CDMS-II events, that suggest a light DM candidate too, and the limits from Xenon10 2009 data, which, depending on the assumed scintillation efficiency, may exclude both CoGeNT and DAMA. Assuming CoGeNT and/or DAMA to be due to DM leads to definite predictions regarding indirect detection and Higgs search at the LHC.Recently, there has been some effervescence regarding what may be first hints of direct detection of dark matter (DM) from the galactic halo. The most recent is related to the CoGeNT experiment, a low background germanium crystal based detector, with a rather modest exposure time and detector mass, but very low threshold energy, which has announced an anomaly in the form of an excess of events at low recoil energies [1]. Although the collaboration clearly leans toward natural radioactivity as the cause for the observed excess, they do put forward the possibility that the events may be explained by the elastic collisions of DM from the galactic halo, with a mass in the ∼ 7 − 10 GeV range, and a rather large spin independent (SI) cross section on nuclei, σ SI ∼ 7 × 10 −41 cm 2 . Surprizingly, these values for the mass and scattering cross section are not too different from those required to fit the DAMA/Libra and DAMA/NaI (DAMA in the sequel) events. DAMA has observed 11 successive cycles of annual modulation in the rate of nuclear recoils, with a statistical significance of 8.2σ [2]. These measurements are consistent with the signal that would arise from elastic scattering of a WIMP from the galactic halo with the nuclei in the detectors, the flux of DM particles being modulated by the periodic motion of the Earth around the Sun [3,4].There has been much work on the DM interpretation of the recent DAMA data (see e.g. [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]). In [21] (see also [22]), it has been shown that the DAMA results may be explained as being caused by the elastic scattering of a singlet scalar DM candidate interacting through the Higgs portal. This particle may be a true singl...

Gamma ray line constraints on effective theories of dark matter

“…In recent years, several have reported anomalous results that are consistent with a light dark matter particle with mass of order 10 GeV [1][2][3] (however, see [4][5][6] as well), leading to a surge of interest in the possibility of light dark matter [7][8][9][10][11][12][13][14][15]. Another experimental probe which is particularly effective for light dark matter is to look for signals of dark matter production at colliders.…”

The Inert Doublet Model and its Phenomenology

“…A continuum of gamma-ray energies are produced mainly due to the quarks hadronization processes, where pions are created and subsequently decay into photons. The Fermi-LAT gamma-ray telescope sets gamma-ray flux limits that are in tension with the expected IDM signals in this mass regime [23,29,30]. Similarly, annihilations inject electrons and positrons, which in a radiation and magnetic-field environment, lead to additional gamma ray, X-ray and radio signals due to e.g.…”

“…The annihilations of H 0 can therefore only be through the second process in (b) -annihilation via the Higgs boson into massive fermions. This mimics singlet scalar models [22,23]. To have correct cross section (∝σ ≡ λ 2 L m 2 f /m 4 h ) at freeze-out the coupling between H 0 and the Higgs boson (∝ λ L ) must be fairly large.…”

“…This type of light scalar DM models has been shown to automatically fit into disputed DAMA/Libra [45] and CoGeNT [49] preferred signal regions when the cross section is fixed by requiring correct amount of thermally produced DM (e.g. [23]). This attractive possibility is however challenged by the CDMS data [50] and the reanalysis of XENON10 data [48].…”

Light neutrinos from a mini-seesaw mechanism in warped space

“…We also note that an order GeV hidden sector has been invoked in connection with some recent experimental anomalies [21,22]. A GeV scale mediator may be motivated by the leptonic cosmic ray anomalies 1 [22], or the dark matter may itself be ∼ GeV (see, e.g., [24]). It is sensible to ask what consequences a sub-weak hidden sector may have in the neutrino sector.…”