163 research outputs found
Two particle states, lepton mixing and oscillations
Discussions of lepton mixing and oscillations consider generally only flavor
oscillations of neutrinos and neglect the accompanying charged leptons. In
cases of experimental interest like pion or nuclear beta decay an oscillation
pattern is expected indeed only for neutrinos if only one of the two produced
particles is observed. We argue that flavor oscillations of neutrinos without
detecting the accompanying lepton is a peculiarity of the two-particle states
produced in pion or nuclear beta decay. Generally, an oscillation
pattern is only found if both particles are detected. We discuss in a
pedagogical way how this distinction of the neutrinos arises, although on the
level of the Lagrangian lepton mixing does not single them out against charged
leptons. As examples, we discuss the difference between the state
produced by the decay of real boson and a originating from pion decay
On the Underground Production of High Purity Germanium Detectors
Detectors based on high purity germanium (HPGe) are used in numerous deep underground experiments world-wide aiming at detecting rare events like double beta decay and interactions of dark matter. These detectors require the lowest possible background. A significant part of the background is due to radionuclides produced by cosmic-ray interactions with the germanium crystal. This report gives quantitative data on this activation and discusses the possible solutions. The first solution is to optimise the logistics during the crystal and detector fabrication so that the germanium spends a minimum time above ground. The second solution is to implement one or several (up to 12) production steps underground. The report also makes estimates on the future needs for germanium produced underground and the costs involved.JRC.D.4-Isotope measurement
Nuclear Propelled Vessels and Neutrino Oscillation Experiments
We study the effect of naval nuclear reactors on the study of neutrino
oscillations. We find that the presence of naval reactors at unknown locations
and times may limit the accuracy of future very long baseline reactor-based
neutrino oscillation experiments. At the same time we argue that a nuclear
powered surface ship such as a large Russian ice-breaker may provide an ideal
source for precision experiments. While the relatively low reactor power would
in this case require a larger detector, the source could be conveniently
located at essentially any distance from a detector built at an underground
location near a shore in a region of the world far away from other nuclear
installations. The variable baseline would allow for a precise measurement of
backgrounds and greatly reduced systematics from reactor flux and detector
efficiency. In addition, once the oscillation measurement is completed, the
detector could perform geological neutrino and astrophysical measurements with
minimal reactor background.Comment: 4 pages, 2 figure
Astrophysical Neutrino Telescopes
This review describes telescopes designed to study neutrinos from
astrophysical sources. These sources include the Sun and Supernovae emitting
neutrino energies up to tens of MeV, atmospheric neutrino sources caused by
cosmic ray interactions and other sources generating neutrino energies ranging
up to eV. Measurements with these telescopes also provide
information on neutrino properties including clear evidence for neutrino flavor
change. Telescopes in operation in the past and present are described, along
with plans for future instruments to expand this rapidly growing field of
particle astrophysics.Comment: 28 pages, 31 figures, Invited review article submitted to Review of
Scientific Instruments May 19, 200
Reactor-based Neutrino Oscillation Experiments
The status of neutrino oscillation searches employing nuclear reactors as
sources is reviewed. This technique, a direct continuation of the experiments
that proved the existence of neutrinos, is today an essential tool in
investigating the indications of oscillations found in studying neutrinos
produced in the sun and in the earth's atmosphere. The low-energy of the
reactor \nuebar makes them an ideal tool to explore oscillations with small
mass differences and relatively large mixing angles.
In the last several years the determination of the reactor anti-neutrino flux
and spectrum has reached a high degree of accuracy. Hence measurements of these
quantities at a given distance L can be readily compared with the expectation
at L = 0, thus testing \nuebar disappearance.
While two experiments, Chooz and Palo Verde, with baselines of about 1 km and
thus sensitive to the neutrino mass differences associated with the atmospheric
neutrino anomaly, have collected data and published results recently, an
ambitious project with a baseline of more than 100 km, Kamland, is preparing to
take data. This ultimate reactor experiment will have a sensitivity sufficient
to explore part of the oscillation phase space relevant to solar neutrino
scenarios. It is the only envisioned experiment with a terrestrial source of
neutrinos capable of addressing the solar neutrino puzzle.Comment: Submitted to Reviews of Modern Physics 34 pages, 39 figure
A New 76Ge Double Beta Decay Experiment at LNGS
This Letter of Intent has been submitted to the Scientific Committee of the
INFN Laboratori Nazionali del Gran Sasso (LNGS) in March 2004. It describes a
novel facility at the LNGS to study the double beta decay of 76Ge using an
(optionally active) cryogenic fluid shield. The setup will allow to scrutinize
with high significance on a short time scale the current evidence for
neutrinoless double beta decay of 76Ge using the existing 76Ge diodes from the
previous Heidelberg-Moscow and IGEX experiments. An increase in the lifetime
limit can be achieved by adding more enriched detectors, remaining thereby
background-free up to a few 100 kg-years of exposure.Comment: 67 pages, 19 eps figures, 17 tables, gzipped tar fil
Complete results for five years of GNO solar neutrino observations
We report the complete GNO solar neutrino results for the measuring periods
GNO III, GNO II, and GNO I. The result for GNO III (last 15 solar runs) is
[54.3 + 9.9 - 9.3 (stat.)+- 2.3 (syst.)] SNU (1 sigma) or [54.3 + 10.2 - 9.6
(incl. syst.)] SNU (1 sigma) with errors combined. The GNO experiment is now
terminated after altogether 58 solar exposure runs that were performed between
May 20, 1998 and April 9, 2003. The combined result for GNO (I+II+III) is [62.9
+ 5.5 - 5.3 (stat.) +- 2.5 (syst.)] SNU (1 sigma) or [62.9 + 6.0 - 5.9] SNU (1
sigma) with errors combined in quadrature. Overall, gallium based solar
observations at LNGS (first in GALLEX, later in GNO) lasted from May 14, 1991
through April 9, 2003. The joint result from 123 runs in GNO and GALLEX is
[69.3 +- 5.5 (incl. syst.)] SNU (1 sigma). The distribution of the individual
run results is consistent with the hypothesis of a neutrino flux that is
constant in time. Implications from the data in particle- and astrophysics are
reiterated.Comment: 22 pages incl. 9 Figures and 8 Tables. to appear in: Physics Letters
B (accepted April 13, 2005) PACS: 26.65.+t ; 14.60.P
Recent Borexino results and prospects for the near future
The Borexino experiment, located in the Gran Sasso National Laboratory, is an
organic liquid scintillator detector conceived for the real time spectroscopy
of low energy solar neutrinos. The data taking campaign phase I (2007 - 2010)
has allowed the first independent measurements of 7Be, 8B and pep fluxes as
well as the first measurement of anti-neutrinos from the earth. After a
purification of the scintillator, Borexino is now in phase II since 2011. We
review here the recent results achieved during 2013, concerning the seasonal
modulation in the 7Be signal, the study of cosmogenic backgrounds and the
updated measurement of geo-neutrinos. We also review the upcoming measurements
from phase II data (pp, pep, CNO) and the project SOX devoted to the study of
sterile neutrinos via the use of a 51Cr neutrino source and a 144Ce-144Pr
antineutrino source placed in close proximity of the active material.Comment: 8 pages, 11 figures. To be published as proceedings of Rencontres de
Moriond EW 201
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