6,332 research outputs found
On decays of Z' into unparticle stuff
We study the decay of a Z' - boson into U -unparticle and a photon. The
extended Landau-Yang theorem is used. The clear photon signal would make the
decay Z' \rightarrow \gamma U as an additional contribution mode for study of
unparticle physics.Comment: 11 pages, 3 figures, paper accepted for publication by Advances in
High Energy Physics journa
Dark matter component decaying after recombination: lensing constraints with Planck data
It has been recently suggested~\cite{Berezhiani:2015yta} that emerging
tension between cosmological parameter values derived in high-redshift (CMB
anisotropy) and low-redshift (cluster counts, Hubble constant) measurements can
be reconciled in a model which contains subdominant fraction of dark matter
decaying after recombination. We check the model against the CMB Planck data.
We find that lensing of the CMB anisotropies by the large-scale structure gives
strong extra constraints on this model, limiting the fraction as at
2\, confidence level. However, investigating the combined data set of
CMB and conflicting low- measurements, we obtain that the model with
\% exhibits better fit (by 1.5-3\, depending on the
lensing priors) compared to that of the concordance CDM cosmological
model.Comment: 5 pages, 4 figures; v2: journal version, pages++, figures+
Evidence for a connection between the gamma-ray and the highest energy cosmic-ray emissions by BL Lacertae objects
A set of potentially gamma-ray--loud BL Lac objects is selected by
intersecting the EGRET and BL Lac catalogs. Of the resulting 14 objects, eight
are found to correlate with arrival directions of ultra--high-energy cosmic
rays (UHECRs), with significance of the order of 5 sigma. This suggests that
gamma-ray emission can be used as a distinctive feature of those BL Lac objects
that are capable of producing UHECR.Comment: 11 pages, 1 figure, version published in APJ Letter
Estimate of the correlation signal between cosmic rays and BL Lacs in future data
The existing correlation between BL Lacertae objects (BL Lacs) and cosmic-ray
events observed by HiRes experiment provide sufficient information to formulate
quantitatively the hypothesis about the flux of neutral cosmic-ray particles
originated from BL Lacs. We determine the potential of future cosmic ray
experiments to test this hypothesis by predicting the number of coincidences
between arrival directions of cosmic rays and positions of BL Lacs on the
celestial sphere, which should be observed in the future datasets. We find that
the early Pierre Auger data will not have enough events to address this
question. On the contrary, the final Pierre Auger data and the early Telescope
Array data will be sufficient to fully test this hypothesis. If confirmed, it
would imply the existence of highest-energy neutral particles coming from
cosmological distances.Comment: 5 page
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