739 research outputs found
A Possible Detection of the Cosmic Antineutrino Background in the Presence of Flavor Effects
Lusignoli and Vignati have recently pointed out that it is in principle
possible to directly detect the cosmic antineutrino background by using the
rather stable isotope holmium-163 as a target, which can decay into
dysprosium-163 via electron capture (EC) with a very small energy release. In
this paper we calculate the rate of the relic antineutrino capture on
holmium-163 nuclei against the corresponding EC decay rate by taking account of
different neutrino mass hierarchies and reasonable values of theta_13. We show
that such flavor effects are appreciable and even important in some cases, and
stress that a calorimetric measurement of the cosmic antineutrino background
might be feasible in the far future.Comment: 13 pages, 5 figures, revised version, accepted for publication in
Phys. Lett.
Direct Detection of the Cosmic Neutrino Background Including Light Sterile Neutrinos
Current cosmological data drop an interesting hint about the existence of
sub-eV sterile neutrinos, which should be a part of the cosmic neutrino
background (CB). We point out that such light sterile neutrinos may leave
a distinct imprint on the electron energy spectrum in the capture of relic
electron neutrinos by means of radioactive beta-decaying nuclei. We examine
possible signals of sterile neutrinos relative to active neutrinos,
characterized by their masses and sensitive to their number densities, in the
reaction against the
corresponding tritium beta decay. We stress that this kind of direct laboratory
detection of the CB and its sterile component might not be hopeless in the
long term.Comment: Minor changes. Accepted for publication in Phys. Lett.
Possible Capture of keV Sterile Neutrino Dark Matter on Radioactive beta-decaying Nuclei
There exists an observed "desert" spanning six orders of magnitude between
O(0.5) eV and O(0.5) MeV in the fermion mass spectrum. We argue that it might
accommodate one or more keV sterile neutrinos as a natural candidate for warm
dark matter. To illustrate this point of view, we simply assume that there is
one keV sterile neutrino nu_4 and its flavor eigenstate nu_s weakly mixes with
three active neutrinos. We clarify different active-sterile neutrino mixing
factors for the radiative decay of nu_4 and beta decays in a self-consistent
parametrization. A direct detection of this keV sterile neutrino dark matter in
the laboratory is in principle possible since the nu_4 component of nu_e can
leave a distinct imprint on the electron energy spectrum when it is captured on
radioactive beta-decaying nuclei. We carry out an analysis of its signatures in
the capture reactions nu_e + ^{3}H \to ^{3}He + e^- and nu_e + ^{106}Ru \to
^{106}Rh + e^- against the beta-decay backgrounds, and conclude that this
experimental approach might not be hopeless in the long run.Comment: 14 pages, 3 figures, more discussions and references added. To appear
in PL
Modeling realistic Earth matter density for CP violation in neutrino oscillation
We examine the effect of a more realistic Earth matter density model which
takes into account of the local density variations along the baseline of a
possi ble 2100 km very long baseline neutrino oscillation experiment. Its
influence to the measurement of CP violation is investigated and a comparison
with the commonly used global density models made. Significant differences are
found in the comparison of the results of the different density models.Comment: 16 pages, 8 figure
Chern-Simons Term for BF Theory and Gravity as a Generalized Topological Field Theory in Four Dimensions
A direct relation between two types of topological field theories,
Chern-Simons theory and BF theory, is presented by using ``Generalized
Differential Calculus'', which extends an ordinary p-form to an ordered pair of
p and (p+1)-form. We first establish the generalized Chern-Weil homomormism for
generalized curvature invariant polynomials in general even dimensional
manifolds, and then show that BF gauge theory can be obtained from the action
which is the generalized second Chern class with gauge group G. Particularly
when G is taken as SL(2,C) in four dimensions, general relativity with
cosmological constant can be derived by constraining the topological BF theory.Comment: Improved abstract and introduction with 11 references added. Accepted
for publication in Physical Review
Measurements of the observed cross sections for exclusive light hadrons containing at , 3.650 and 3.6648 GeV
By analyzing the data sets of 17.3, 6.5 and 1.0 pb taken,
respectively, at , 3.650 and 3.6648 GeV with the BES-II
detector at the BEPC collider, we measure the observed cross sections for
, , ,
and at the three energy
points. Based on these cross sections we set the upper limits on the observed
cross sections and the branching fractions for decay into these
final states at 90% C.L..Comment: 7 pages, 2 figure
Partial wave analysis of J/\psi \to \gamma \phi \phi
Using events collected in the BESII detector, the
radiative decay is
studied. The invariant mass distribution exhibits a near-threshold
enhancement that peaks around 2.24 GeV/.
A partial wave analysis shows that the structure is dominated by a
state () with a mass of
GeV/ and a width of GeV/. The
product branching fraction is: .Comment: 11 pages, 4 figures. corrected proof for journa
Direct Measurements of Absolute Branching Fractions for D0 and D+ Inclusive Semimuonic Decays
By analyzing about 33 data sample collected at and around 3.773
GeV with the BES-II detector at the BEPC collider, we directly measure the
branching fractions for the neutral and charged inclusive semimuonic decays
to be and , and determine the ratio of the two branching
fractions to be
Direct Measurements of the Branching Fractions for and and Determinations of the Form Factors and
The absolute branching fractions for the decays and
are determined using singly
tagged sample from the data collected around 3.773 GeV with the
BES-II detector at the BEPC. In the system recoiling against the singly tagged
meson, events for and events for decays are observed. Those yield
the absolute branching fractions to be and . The
vector form factors are determined to be
and . The ratio of the two form
factors is measured to be .Comment: 6 pages, 5 figure
Measurements of J/psi Decays into 2(pi+pi-)eta and 3(pi+pi-)eta
Based on a sample of 5.8X 10^7 J/psi events taken with the BESII detector,
the branching fractions of J/psi--> 2(pi+pi-)eta and J/psi-->3(pi+pi-)eta are
measured for the first time to be (2.26+-0.08+-0.27)X10^{-3} and
(7.24+-0.96+-1.11)X10^{-4}, respectively.Comment: 11 pages, 6 figure
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