846 research outputs found
Heavy sterile neutrinos: Bounds from big-bang nucleosynthesis and SN 1987A
Cosmological and astrophysical effects of heavy (10 - 200 MeV) sterile Dirac
neutrinos, mixed with the active ones, are considered. The bounds on mass and
mixing angle from both supernovae and big-bang nucleosynthesis are presented.Comment: 19 pages, 5 figures, 1 table. Some references adde
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O-3, NOY, AND NOX/NOY IN THE UPPER TROPOSPHERE OF THE EQUATORIAL PACIFIC
Low Energy Neutrino Physics after SNO and KamLAND
In the recent years important discoveries in the field of low energy neutrino
physics (E in the MeV range) have been achieved. Results of the
solar neutrino experiment SNO show clearly flavor transitions from to
. In addition, the long standing solar neutrino problem is
basically solved. With KamLAND, an experiment measuring neutrinos emitted from
nuclear reactors at large distances, evidence for neutrino oscillations has
been found. The values for the oscillation parameters, amplitude and phase,
have been restricted. In this paper the potential of future projects in low
energy neutrino physics is discussed. This encompasses future solar and reactor
experiments as well as the direct search for neutrino masses. Finally the
potential of a large liquid scintillator detector in an underground laboratory
for supernova neutrino detection, solar neutrino detection, and the search for
proton decay is discussed.Comment: Invited brief review, World Scientific Publishing Compan
Ozonesonde profiles from the West Pacific Warm Pool: measurements and validation
© Author(s) 2016. CC Attribution 3.0 LicenseWe present a series of ozonesonde profiles measured from Manus Island, Papua New Guinea, during February 2014, with new insights on the calibration of ozonesondes for measurements in the tropical troposphere. The experiment formed a part of a wider airborne campaign involving three aircraft based in Guam, to characterise the atmospheric composition above the tropical West Pacific in unprecedented detail. Thirty-nine ozonesondes were launched between 2 and 25 February of which 34 gave good ozone profiles. Particular attention was paid to evaluating the background current of the ozonesondes, as this can amount to half the measured signal in the tropical tropopause layer (TTL). An unexpected contamination event affected the measurements and required a departure from standard operating procedures for the ozonesondes. The most significant departure was not exposing the sondes to ozone during preparation, which meant that the background current remained stable before launch. Comparison with aircraft measurements allows validation of the measured ozone profiles and confirms that for well-characterized sondes (background current ∼  50 nA) a constant background current could be assumed throughout the profile, equal to the minimum value measured during preparation just before launch. From this set of 34 ozonesondes, the minimum reproducible ozone concentration measured in the TTL was 12–13 ppbv; no examples of ozone concentrations  <  5 ppbv, as reported by other recent papers, were measured. The lowest ozone concentrations coincided with outflow from extensive deep convection to the east of Manus, consistent with uplift of ozone-poor air from the boundary layer. However, these minima were lower than the ozone concentration measured through most of the boundary layer, and were matched only by measurements at the surface in Manus.Peer reviewe
-Decay Spectrum, Response Function and Statistical Model for Neutrino Mass Measurements with the KATRIN Experiment
The objective of the Karlsruhe Tritium Neutrino (KATRIN) experiment is to
determine the effective electron neutrino mass with an
unprecedented sensitivity of (90\% C.L.) by precision electron
spectroscopy close to the endpoint of the decay of tritium. We present
a consistent theoretical description of the electron energy spectrum in
the endpoint region, an accurate model of the apparatus response function, and
the statistical approaches suited to interpret and analyze tritium
decay data observed with KATRIN with the envisaged precision. In addition to
providing detailed analytical expressions for all formulae used in the
presented model framework with the necessary detail of derivation, we discuss
and quantify the impact of theoretical and experimental corrections on the
measured . Finally, we outline the statistical methods for
parameter inference and the construction of confidence intervals that are
appropriate for a neutrino mass measurement with KATRIN. In this context, we
briefly discuss the choice of the energy analysis interval and the
distribution of measuring time within that range.Comment: 27 pages, 22 figures, 2 table
Global Analysis of Neutrino Data
In this talk I review the present status of neutrino masses and mixing and
some of their implications for particle physics phenomenology. I first discuss
the minimum extension of the Standard Model of particle physics required to
accommodate neutrino masses and introduce the new parameters present in the
model and in particular the possibility of leptonic mixing. I then describe the
phenomenology of neutrino masses and mixing leading to flavour oscillations and
present the existing evidence from solar, reactor, atmospheric and
long-baseline neutrinos as well as the results from laboratory searches at
short distances. I derive the allowed ranges for the mass and mixing parameters
when the bulk of data is consistently analyzed in the framework of mixing
between the three active neutrinos and obtain as a result the most up-to-date
determination of the leptonic mixing matrix. Then I briefly summarize the
status of some proposed phenomenological explanations to accommodate the LSND
results: the role of sterile neutrinos and the violation of CPT. Finally I
comment how within the present experimental precision it is possible to use the
observation of oscillation patterns to impose severe constraints on the
possible violation of fundamental symmetries in particle physics such as
Lorentz invariance or the weak equivalence principle.Comment: Talk given at the Nobel Symposium on Neutrino Physics, Haga Slott,
Enkoping, Swede
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