Stringent Constraint on Galactic Positron Production

Beacom, J. F.; Yüksel, Hasan

doi:10.1103/physrevlett.97.071102

Cited by 226 publications

(316 citation statements)

References 46 publications

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“…At first, this result may seem surprising, given that the twophoton annihilation process is higher order in e , but this suppression is counteracted by the helicity suppression of the cross section for annihilation of Majorana fermions to electron-positron pairs. References [28,29] considered also gamma rays from in-flight annihilation from e e ÿ pairs, but their analysis was restricted to energies <100 MeV.…”

Section: Discussionmentioning

confidence: 99%

Search with EGRET for a gamma ray line from the Galactic center

2007

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We search data from the Energetic Gamma Ray Experiment Telescope (EGRET) for a gamma-ray line in the energy range 0.1-10 GeV from the 10 10 region around the Galactic center. Our null results lead to upper limits to the line flux from the Galactic center. Such lines may have appeared if the dark matter in the Galactic halo is composed of weakly interacting massive particles (WIMPs) in the mass range 0.1-10 GeV. For a given dark-matter-halo model, our null search translates to upper limits to the WIMP two-photon annihilation cross section as a function of WIMP mass. We show that, for a toy model in which Majorana WIMPs in this mass range annihilate only to electron-positron pairs, these upper limits supersede those derived from measurements of the 511-keV line and continuum photons from internal bremsstrahlung at the Galactic center.

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Section: Discussionmentioning

confidence: 99%

Search with EGRET for a gamma ray line from the Galactic center

2007

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“…The upper line a ≃ 10 −25 cm 3 s −1 corresponds to a purely S-wave cross-section, and the lower part of the diagram to a P -wave dominated one (a being negligible). As mX cannot be too large, in order not to overproduce gamma and radio continuum from the galactic center, we limit ourselves, conservatively, to the interval 0.511 to 100 MeV (the actuallyallowed mass interval could in fact be significantly smaller [33,45,46,47] depending on how seriously these other constraints are taken). The grey region is the one compatible with the galactic constraint, based on the total level of emission, using the (Moore or NFW) dark-matter distributions of Table I (its upper part corresponds to a Milky-Way emission that would-be S-wavedominated, with a behaving like 1/m 2 X ).…”

Section: Constraints On Dark Matter Candidatesmentioning

confidence: 99%

Soft gamma-ray background and light dark matter annihilation

et al. 2006

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The bulk of the extragalactic background between 10 keV and 10 GeV is likely to be explained by the emission of Seyfert galaxies, type Ia supernovae, and blazars. However, as revealed by the INTEGRAL satellite, the bulge of our galaxy is an intense source of a 511 keV gamma-ray line, indicating the production of a large number of positrons that annihilate. The origin of the latter is debated, and they could be produced, in particular, by the (S-or P -wave) annihilation of light Dark Matter particles into e + e − . In any case, the cumulated effect of similar sources at all redshifts could lead to a new background of hard X-ray and soft gamma-ray photons. On the basis of the hierarchical model of galaxy formation, we compute analytically the SNIa contribution to the background, and add it to Seyfert and blazars emission models. Confronting these expected contributions to observation, we find that any extra contribution to this unresolved background around 511 keV should be lower than about 4 keV cm −2 s −1 sr −1 . We also estimate analytically the extragalactic background due to Dark Matter annihilation, increasing the accuracy of the earlier computations. Indeed, we take into account the large positron escape fraction from low mass dark matter halos, unable to confine a dense and magnetized interstellar medium. Our new background estimate turns out to be one order of magnitude lower so that the hypothesis of a light Dark Matter candidate remains compatible with the observed extragalactic background for a wider range of particle masses and cross-sections.PACS numbers: 95.35.+d, 95.85.Nv, 95.85.Pw, 97.60.Bw

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“…Only velocity-dependent cross sections would be able to accommodate both evidences, but provide a bad fit to the Integral/SPI data for masses below ∼100 MeV [13,14]. In addition, higher order processes would lead to gamma ray production via internal bremsstrahlung [15,16,17] and positron annihilations in flight with the electrons in the interstellar medium [17,18]. The COMPTEL and EGRET data constrain either the cross section to be smaller than what is required to explain the 511 keV line or the DM mass to be smaller than a few MeV.…”

Section: Introductionmentioning

confidence: 99%

Testing MeV dark matter with neutrino detectors

2008

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MeV particles have been advocated as Dark Matter (DM) candidates in different contexts. This hypothesis can be tested indirectly by searching for the Standard Model (SM) products of DM self-annihilations. As the signal from DM self-annihilations depends on the square of the DM density, we might expect a sizable flux of annihilation products from our galaxy. Neutrinos are the least detectable particles in the SM and a null signal in this channel would allow to set the most conservative bound on the total annihilation cross section. Here, we show that neutrino detectors with good energy resolution and low energy thresholds can not only set bounds on the annihilation cross section but actually test the hypothesis of the possible existence of MeV DM, i.e. test the values of the cross section required to explain the observed DM density. At present, the data in the (positron) energy interval MeV of the Super-Kamiokande experiment is already able to put a very stringent bound on the annihilation cross section for masses between ∼15-130 MeV. Future large experiments, like megaton water-Čerenkov or large scintillator detectors, will improve the present limits and, if MeV DM exists, would be able to detect it.PACS numbers: 14.60. St, 95.35.+d, 95.55.Vj

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Stringent Constraint on Galactic Positron Production

Cited by 226 publications

References 46 publications

Search with EGRET for a gamma ray line from the Galactic center

Search with EGRET for a gamma ray line from the Galactic center

Soft gamma-ray background and light dark matter annihilation

Testing MeV dark matter with neutrino detectors

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