14 research outputs found
A fussy revisitation of antiprotons as a tool for Dark Matter searches
Antiprotons are regarded as a powerful probe for Dark Matter (DM) indirect
detection and indeed current data from PAMELA have been shown to lead to
stringent constraints. However, in order to exploit their
constraining/discovery power properly and especially in anticipation of the
exquisite accuracy of upcoming data from AMS, great attention must be put into
effects (linked to their propagation in the Galaxy) which may be perceived as
subleasing but actually prove to be quite relevant. We revisit the computation
of the astrophysical background and of the DM antiproton fluxes fully including
the effects of: diffusive reacceleration, energy losses including tertiary
component and solar modulation (in a force field approximation). We show that
their inclusion can somewhat modify the current bounds, even at large DM
masses, and that a wrong interpretation of the data may arise if they are not
taken into account. The numerical results for the astrophysical background are
provided in terms of fit functions; the results for Dark Matter are
incorporated in the new release of the PPPC4DMID.Comment: v3: small comments and references added, matches journal versio
PPPC 4 DM secondary: A Poor Particle Physicist Cookbook for secondary radiation from Dark Matter
We enlarge the set of recipes and ingredients at disposal of any poor
particle physicist eager to cook up signatures from weak-scale Dark Matter
models by computing two secondary emissions due to DM particles annihilating or
decaying in the galactic halo, namely the radio signals from synchrotron
emission and the gamma rays from bremsstrahlung. We consider several magnetic
field configurations and propagation scenarios for electrons and positrons. We
also provide an improved energy loss function for electrons and positrons in
the Galaxy, including synchrotron losses in the different configurations,
bremsstrahlung losses, ionization losses and Inverse Compton losses with an
updated InterStellar Radiation Field.Comment: 25 pages, many figures. v2: a small clarification on the use of
custom galactic magnetic fields added, matches version published on JCAP. All
results are available at http://www.marcocirelli.net/PPPC4DMID.htm
Antiproton constraints on the GeV gamma-ray excess: a comprehensive analysis
A GeV gamma-ray excess has possibly been individuated in Fermi-LAT data from
the Galactic Center and interpreted in terms of Dark Matter (DM) annihilations,
either in hadronic (essentially ) or leptonic channels. In order to
test this tantalizing interpretation, we address two issues: (i) we improve the
computation of secondary emission from DM (Inverse Compton and Bremsstrahlung)
with respect to previous works, confirming it to be very relevant for
determining the DM spectrum in the leptonic channels, so that any conclusion on
the DM nature of the signal critically depends on this contribution; (ii) we
consider the constraints from antiprotons on the DM hadronic channel, finding
that the uncertainties on the propagation model, and in particular on the halo
height, play a major role. Moreover, we discuss the role of solar modulation,
taking into account possible charge dependent effects whose importance is
estimated exploiting detailed numerical tools. The limits that we obtain
severely constrain the DM interpretation of the excess in the hadronic channel,
for standard assumptions on the Galactic propagation parameters and solar
modulation. However, they considerably relax if more conservative choices are
adopted.Comment: 22 pages, 6 figures, 2 table
AMS-02 antiprotons, at last! Secondary astrophysical component and immediate implications for Dark Matter
Using the updated proton and helium fluxes just released by the AMS-02
experiment we reevaluate the secondary astrophysical antiproton to proton ratio
and its uncertainties, and compare it with the ratio preliminarly reported by
AMS-02. We find no unambiguous evidence for a significant excess with respect
to expectations. Yet, some preference for a flatter energy dependence of the
diffusion coefficient starts to emerge. Also, we provide a first assessment of
the room left for exotic components such as Galactic Dark Matter annihilation
or decay, deriving new stringent constraints.Comment: 12 pages, 5 figures; Comments and clarifications added (including an
appendix), matches version published on JCA
CMB photons shedding light on dark matter
The annihilation or decay of Dark Matter (DM) particles could affect the
thermal history of the universe and leave an observable signature in Cosmic
Microwave Background (CMB) anisotropies. We update constraints on the
annihilation rate of DM particles in the smooth cosmological background, using
WMAP7 and recent small-scale CMB data. With a systematic analysis based on the
Press-Schechter formalism, we also show that DM annihilation in halos at small
redshift may explain entirely the reionization patterns observed in the CMB,
under reasonable assumptions concerning the concentration and formation
redshift of halos. We find that a mixed reionization model based on DM
annihilation in halos as well as star formation at a redshift z~6.5 could
simultaneously account for CMB observations and satisfy constraints inferred
from the Gunn-Peterson effect. However, these models tend to reheat the
inter-galactic medium (IGM) well above observational bounds: by including a
realistic prior on the IGM temperature at low redshift, we find stronger
cosmological bounds on the annihilation cross-section than with the CMB alone.Comment: 35 pages, 14 figures; version accepted in JCAP after minor revision
Antiprotons from Dark Matter: current constraints and future sensitivities
A few references added and a few typos corrected, matches version published on JCAPInternational audienceWe systematically analyze the impact of current and foreseen cosmic ray antiproton measurements on the properties of Dark Matter (DM). We find that: 1) The current data from PAMELA impose constraints on annihilating and decaying DM which are similar to (or even slightly stronger than) the most stringent bounds coming from Fermi gamma rays, for hadronic channels and with fiducial choices for the astrophysical parameters. 2) The upcoming data from AMS-02 have the power to improve these constraints by slightly less than one order of magnitude and even to probe the thermal relic DM in the range 30-200 GeV, for hadronic channels. However, with wider choices for the astrophysical parameters the uncertainty on the constraints spans between one and two orders of magnitude. We then explore the capabilities of early AMS-02, data to reconstruct the underlying DM properties in the case of a positive detection of a significant excess (attributed to DM annihilations) over the background. For hadronic channels, we find that AMS-02 should be able to somewhat determine the DM mass and the cross-section, but not the specific annihilation channel nor the branching ratios. If other more exotic annihilation channels are allowed, the reconstruction will be more challenging