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Register a new userNew limits on dark photons from solar emission and keV scale dark matter
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We provide updates to the limits on solar emission of dark photons, or more generally any light vector particle coupled to the electron vector current. The recent 2019 and 2020 electronic recoil data from XENON1T now provides more stringent constraints on these models than stellar energy loss in the sub-keV mass region. We also show that solar emission of dark photons does not provide a good fit to the recent XENON1T excess in the 2-5 keV energy bins. In contrast, the absorption of 2-4 keV mass dark photons that saturate the local dark matter mass density does provide a good fit to the excess, for mixing angles in the range $epsilon in (4-12)times 10^{-16}$, while satisfying astrophysical constraints. Similarly, other models utilizing the vector portal can fit the excess, including those with operators that directly couple the dark photon field strength to electron spin.
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We study the interaction of an electrically charged component of the dark matter with a magnetized galactic interstellar medium (ISM) of (rotating) spiral galaxies. For the observed ordered component of the field, $Bsim mu$G, we find that the accumulated Lorentz interactions between the charged particles and the ISM will extract an order unity fraction of the disk angular momentum over the few Gyr Galactic lifetime unless $q/e lesssim 10^{-13pm 1},m,c^2/$ GeV if all the dark matter is charged. The bound is weakened by factor $f_{rm qdm}^{-1/2}$ if only a mass fraction $f_{rm qdm}gtrsim0.13$ of the dark matter is charged. Here $q$ and $m$ are the dark matter particle mass and charge. If $f_{rm qdm}approx1$ this bound excludes charged dark matter produced via the freeze-in mechanism for $m lesssim$ TeV/$c^2$. This bound on $q/m$, obtained from Milky Way parameters, is rough and not based on any precise empirical test. However this bound is extremely strong and should motivate further work to better model the interaction of charged dark matter with ordered and disordered magnetic fields in galaxies and clusters of galaxies; to develop precise tests for the presence of charged dark matter based on better estimates of angular momentum exchange; and also to better understand how charged dark matter might modify the growth of magnetic fields, and the formation and interaction histories of galaxies, galaxy groups, and clusters.
If the present dark matter in the Universe annihilates into Standard Model particles, it must contribute to the gamma ray fluxes detected on the Earth. The magnitude of such contribution depends on the particular dark matter candidate, but certain features of the produced spectra may be analyzed in a rather model-independent fashion. In this communication we briefly revise the complete photon spectra coming from WIMP annihilation into Standard Model particle-antiparticle pairs obtained by extensive Monte Carlo simulations and consequent fitting functions presented by Dombriz et al. in a wide range of WIMP masses. In order to illustrate the usefulness of these fitting functions, we mention how these results may be applied to the so-called brane-world theories whose fluctuations, the branons, behave as WIMPs and therefore may spontaneously annihilate in SM particles. The subsequent $gamma$-rays signal in the framework of dark matter indirect searches from Milky Way dSphs and Galactic Center may provide first evidences for this scenario.
We present limits on the WIMP-nucleon cross section for inelastic dark matter derived from the 2008 run of ZEPLIN-III. Cuts, notably on scintillation pulse shape and scintillation-to-ionisation ratio, give a net exposure of 63 kg.days in the range 20-80keV nuclear recoil energy, in which 6 events are observed. Upper limits on signal rate are derived from the maximum empty patch in the data. Under standard halo assumptions a small region of parameter space consistent, at 99% CL, with causing the 1.17 ton.year DAMA modulation signal is allowed at 90% CL: it is in the mass range 45-60 GeV with a minimum CL of 88%, again derived from the maximum patch. This is the tightest constraint on that explanation of the DAMA result yet presented using a xenon target.
We propose a possible explanation for the recently observed anomalous 511 keV line with a new millicharged fermion. This new fermion is light [${cal O}({rm MeV})$]. Nevertheless, it has never been observed by any collider experiments by virtue of its tiny electromagnetic charge $epsilon e$. In particular, we constrain parameters of this millicharged particle if the 511 keV cosmic $gamma$-ray emission from the galactic bulge is due to positron production from this new particle.
We derive 95% CL lower limits on the lifetime of decaying dark matter in the channels $Z u$, $Well$ and $h u$ using measurements of the cosmic-ray antiproton flux by the PAMELA experiment. Performing a scan over the allowed range of cosmic-ray propagation parameters we find lifetime limits in the range of $8 times 10^{28}$s to $5 times 10^{25}$s for dark matter masses from roughly 100 GeV to 10 TeV. We apply these limits to the well-motivated case of gravitino dark matter in scenarios with bilinear violation of R-parity and find a similar range of lifetime limits for the same range of gravitino masses. Converting the lifetime limits to constraints on the size of the R-parity violating coupling we find upper limits in the range of $10^{-8}$ to $8 times 10^{-13}$.
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