43 research outputs found
Model-independent implications of the e+, e-, anti-proton cosmic ray spectra on properties of Dark Matter
Taking into account spins, we classify all two-body non-relativistic Dark
Matter annihilation channels to the allowed polarization states of Standard
Model particles, computing the energy spectra of the stable final-state
particles relevant for indirect DM detection. We study the DM masses,
annihilation channels and cross sections that can reproduce the PAMELA
indications of an e+ excess consistently with the PAMELA p-bar data and the
ATIC/PPB-BETS e++e- data. From the PAMELA data alone, two solutions emerge: (i)
either the DM particles that annihilate into W,Z,h must be heavier than about
10 TeV or (ii) the DM must annihilate only into leptons. Thus in both cases a
DM particle compatible with the PAMELA excess seems to have quite unexpected
properties. The solution (ii) implies a peak in the e++e- energy spectrum,
which, indeed, seems to appear in the ATIC/PPB-BETS data around 700 GeV. If
upcoming data from ATIC-4 and GLAST confirm this feature, this would point to a
O(1) TeV DM annihilating only into leptons. Otherwise the solution (i) would be
favored. We comment on the implications of these results for DM models, direct
DM detection and colliders as well as on the possibility of an astrophysical
origin of the excess.Comment: Version 4: addendum about the 2013 AMS positron data (version 5: just
refinements and additions to fig. 14
Multi-muon events at the Tevatron: a hidden sector from hadronic collisions
Intrigued by some features of a small but significant fraction of the
multi-muon events recently published by the CDF collaboration, we show an
explicit attempt to describe them in terms of a light scalar singlet
which communicates with the standard quarks either through a heavy scalar or a
heavy fermion exchange. As suggested in arXiv:0810.7530, the singlet has
a chain decay into a final state made of four pairs. We can
simulate most of the muon properties of the selected sample of events. Some of
these properties adhere rather well to the already published data; others
should allow a decisive test of the proposed interpretation. Assuming that the
test is positively passed, we show how the PAMELA excess can be fitted by the
annihilation of a TeV Dark Matter particle that communicates with the Standard
Model via the new light singlet(s).Comment: 19 pp, v2: small changes, agrees with the published versio
Robust implications on Dark Matter from the first FERMI sky gamma map
We derive robust model-independent bounds on DM annihilations and decays from
the first year of FERMI gamma-ray observations of the whole sky. These bounds
only have a mild dependence on the DM density profile and allow the following
DM interpretations of the PAMELA and FERMI electron/positron excesses: primary
channels mu+ mu-, mu+ mu-mu+mu- or e+ e- e+ e-. An isothermal-like density
profile is needed for annihilating DM. In all such cases, FERMI gamma spectra
must contain a significant DM component, that may be probed in the future.Comment: 16 pages, 8 figures. Final versio
Decaying Dark Matter can explain the electron/positron excesses
PAMELA and ATIC recently reported excesses in e+ e- cosmic rays. Since the
interpretation in terms of DM annihilations was found to be not easily
compatible with constraints from photon observations, we consider the DM decay
hypothesis and find that it can explain the e+ e- excesses compatibly with all
constraints, and can be tested by dedicated HESS observations of the Galactic
Ridge. ATIC data indicate a DM mass of about 2 TeV: this mass naturally implies
the observed DM abundance relative to ordinary matter if DM is a quasi-stable
composite particle with a baryon-like matter asymmetry. Technicolor naturally
yields these type of candidates.Comment: 20 pages, 7 figure
Cosmology of neutrinos and extra light particles after WMAP3
We study how present data probe standard and non-standard properties of
neutrinos and the possible existence of new light particles, freely-streaming
or interacting, among themselves or with neutrinos. Our results include: sum
m_nu < 0.40 eV at 99.9% C.L.; that extra massless particles have abundance
Delta N_nu = 2 pm 1 if freely-streaming and Delta N_nu = 0 pm 1.3 if
interacting; that 3 interacting neutrinos are disfavored at about 4 sigma. We
investigate the robustness of our results by fitting to different sub-sets of
data. We developed our own cosmological computational tools, somewhat different
from the standard ones.Comment: 18 pages, 8 figures. Added in v2: an explicit comparison of our code
with CAMB, some clarifications on the statistical analysis and some
references. Matches version published in JCA
Dirac Neutrinos, Dark Energy and Baryon Asymmetry
We explore a new origin of neutrino dark energy and baryon asymmetry in the
universe. The neutrinos acquire small masses through the Dirac seesaw
mechanism. The pseudo-Nambu-Goldstone boson associated with neutrino
mass-generation provides a candidate for dark energy. The puzzle of
cosmological baryon asymmetry is resolved via neutrinogenesis.Comment: 6 pages, 1 figure. Accepted by JCAP (only minor rewordings, refs
added
Gamma-ray and radio tests of the e+e- excess from DM annihilations
PAMELA and ATIC recently reported an excess in e+e- cosmic rays. We show that
if it is due to Dark Matter annihilations, the associated gamma-ray flux and
the synchrotron emission produced by e+e- in the galactic magnetic field
violate HESS and radio observations of the galactic center and HESS
observations of dwarf Spheroidals, unless the DM density profile is
significantly less steep than the benchmark NFW and Einasto profiles.Comment: 16 pages, 4 figures; v2: normalizations fixed in Table 2 and typos
corrected (no changes in the analysis nor the results), some references and
comments added; v3: minor additions, matches published versio
Large Lepton Mixings from Continuous Symmetries
Within the broad context of quark-lepton unification, we investigate the
implications of broken continuous family symmetries which result from requiring
that in the limit of exact symmetry, the Dirac mass matrices yield hierarchical
masses for the quarks and charged leptons, but lead to degenerate light
neutrino masses as a consequence of the seesaw mechanism, without requiring
hierarchical right-handed neutrino mass terms. Quark mixing is then naturally
small and proportional to the size of the perturbation, but lepton mixing is
large as a result of degenerate perturbation theory, shifted from maximal
mixing by the size of the perturbation. Within this approach, we study an
illustrative two-family prototype model with an SO(2) family symmetry, and
discuss extensions to three-family models.Comment: 23 page
Constraining Very Heavy Dark Matter Using Diffuse Backgrounds of Neutrinos and Cascaded Gamma Rays
We consider multi-messenger constraints on very heavy dark matter (VHDM) from
recent Fermi gamma-ray and IceCube neutrino observations of isotropic
background radiation. Fermi data on the diffuse gamma-ray background (DGB)
shows a possible unexplained feature at very high energies (VHE), which we have
called the "VHE Excess" relative to expectations for an attenuated power law
extrapolated from lower energies. We show that VHDM could explain this excess,
and that neutrino observations will be an important tool for testing this
scenario. More conservatively, we derive new constraints on the properties of
VHDM for masses of 10^3-10^10 GeV. These generic bounds follow from cosmic
energy budget constraints for gamma rays and neutrinos that we developed
elsewhere, based on detailed calculations of cosmic electromagnetic cascades
and also neutrino detection rates. We show that combining both gamma-ray and
neutrino data is essential for making the constraints on VHDM properties both
strong and robust. In the lower mass range, our constraints on VHDM
annihilation and decay are comparable to other results; however, our
constraints continue to much higher masses, where they become relatively
stronger.Comment: 33 pages, 21 figures, accepted for publication in JCA