32 research outputs found
The KATRIN Experiment
The KArlsruhe TRitium Neutrino mass experiment, KATRIN, aims to search for
the mass of the electron neutrino with a sensitivity of 0.2 eV/c^2 (90% C.L.)
and a detection limit of 0.35 eV/c^2 (5 sigma). Both a positive or a negative
result will have far reaching implications for cosmology and the standard model
of particle physics and will give new input for astroparticle physics and
cosmology. The major components of KATRIN are being set up at the Karlsruhe
Institut of Technology in Karlsruhe, Germany, and test measurements of the
individual components have started. Data taking with tritium is scheduled to
start in 2012.Comment: 3 pages, 1 figure, proceedings of the TAUP 2009 International
Conference on Topics in Astroparticle and Underground Physics, to be
published in Journal of Physics, Conference Serie
Monitoring of tritium purity during long-term circulation in the KATRIN test experiment LOOPINO using laser Raman spectroscopy
The gas circulation loop LOOPINO has been set up and commissioned at Tritium
Laboratory Karlsruhe (TLK) to perform Raman measurements of circulating tritium
mixtures under conditions similar to the inner loop system of the neutrino-mass
experiment KATRIN, which is currently under construction. A custom-made
interface is used to connect the tritium containing measurement cell, located
inside a glove box, with the Raman setup standing on the outside. A tritium
sample (purity > 95%, 20 kPa total pressure) was circulated in LOOPINO for more
than three weeks with a total throughput of 770 g of tritium. Compositional
changes in the sample and the formation of tritiated and deuterated methanes
CT_(4-n)X_n (X=H,D; n=0,1) were observed. Both effects are caused by hydrogen
isotope exchange reactions and gas-wall interactions, due to tritium {\beta}
decay. A precision of 0.1% was achieved for the monitoring of the T_2
Q_1-branch, which fulfills the requirements for the KATRIN experiment and
demonstrates the feasibility of high-precision Raman measurements with tritium
inside a glove box
Theory of neutrinoless double beta decay
Neutrinoless double beta decay, which is a very old and yet elusive process,
is reviewed. Its observation will signal that lepton number is not conserved
and the neutrinos are Majorana particles. More importantly it is our best hope
for determining the absolute neutrino mass scale at the level of a few tens of
meV. To achieve the last goal certain hurdles have to be overcome involving
particle, nuclear and experimental physics. Nuclear physics is important for
extracting the useful information from the data. One must accurately evaluate
the relevant nuclear matrix elements, a formidable task. To this end, we review
the sophisticated nuclear structure approaches recently been developed, which
give confidence that the needed nuclear matrix elements can be reliably
calculated. From an experimental point of view it is challenging, since the
life times are long and one has to fight against formidable backgrounds. If a
signal is found, it will be a tremendous accomplishment. Then, of course, the
real task is going to be the extraction of the neutrino mass from the
observations. This is not trivial, since current particle models predict the
presence of many mechanisms other than the neutrino mass, which may contribute
or even dominate this process. We will, in particular, consider the following
processes: (i)The neutrino induced, but neutrino mass independent contribution.
(ii)Heavy left and/or right handed neutrino mass contributions.
(iii)Intermediate scalars (doubly charged etc). (iv)Supersymmetric (SUSY)
contributions. We will show that it is possible to disentangle the various
mechanisms and unambiguously extract the important neutrino mass scale, if all
the signatures of the reaction are searched in a sufficient number of nuclear
isotopes.Comment: 104 pages, 6 tables, 25 figures.References added. To appear in ROP
(Reports on Progress in Physics), copyright RO
Revisiting Bimaximal Neutrino Mixing in a Model with S4 Discrete Symmetry
In view of the fact that the data on neutrino mixing are still compatible
with a situation where Bimaximal mixing is valid in first approximation and it
is then corrected by terms of order of the Cabibbo angle, arising from the
diagonalization of the charged lepton masses, we construct a model based on the
discrete group S4 where those properties are naturally realized. The model is
supersymmetric in 4-dimensions and the complete flavour group is S4 x Z4 x
U(1)_FN, which also allows to reproduce the hierarchy of the charged lepton
spectrum. The only fine tuning needed in the model is to reproduce the small
observed value of r, the ratio between the neutrino mass squared differences.
Once the relevant parameters are set to accommodate r then the spectrum of
light neutrinos shows a moderate normal hierarchy and is compatible, within
large ambiguities, with the constraints from leptogenesis as an explanation of
the baryon asymmetry in the Universe.Comment: 30 pages, 5 figures; added reference
A UV LED-based fast-pulsed photoelectron source for time-of-flight studies
We report on spectroscopy and time-of-flight measurements using an 18 keV
fast-pulsed photoelectron source of adjustable intensity, ranging from single
photoelectrons per pulse to 5 photoelectrons per microsecond at pulse
repetition rates of up to 10 kHz. Short pulses between 40 ns and 40
microseconds in length were produced by switching light emitting diodes with
central output wavelengths of 265 nm and 257 nm, in the deep ultraviolet (or
UV-C) regime, at kHz frequencies. Such photoelectron sources can be useful
calibration devices for testing the properties of high-resolution electrostatic
spectrometers, like the ones used in current neutrino mass searches.Comment: 16 pages, 11 figure
Persistent neuropsychiatric symptoms after COVID-19: a systematic review and meta-analysis.
The nature and extent of persistent neuropsychiatric symptoms after COVID-19 are not established. To help inform mental health service planning in the pandemic recovery phase, we systematically determined the prevalence of neuropsychiatric symptoms in survivors of COVID-19. For this pre-registered systematic review and meta-analysis (PROSPERO ID CRD42021239750), we searched MEDLINE, EMBASE, CINAHL and PsycINFO to 20 February 2021, plus our own curated database. We included peer-reviewed studies reporting neuropsychiatric symptoms at post-acute or later time-points after COVID-19 infection and in control groups where available. For each study, a minimum of two authors extracted summary data. For each symptom, we calculated a pooled prevalence using generalized linear mixed models. Heterogeneity was measured with I 2. Subgroup analyses were conducted for COVID-19 hospitalization, severity and duration of follow-up. From 2844 unique titles, we included 51 studies (nâ=â18â917 patients). The mean duration of follow-up after COVID-19 was 77 days (range 14-182 days). Study quality was most commonly moderate. The most prevalent neuropsychiatric symptom was sleep disturbance [pooled prevalenceâ=â27.4% (95% confidence interval 21.4-34.4%)], followed by fatigue [24.4% (17.5-32.9%)], objective cognitive impairment [20.2% (10.3-35.7%)], anxiety [19.1% (13.3-26.8%)] and post-traumatic stress [15.7% (9.9-24.1%)]. Only two studies reported symptoms in control groups, both reporting higher frequencies in COVID-19 survivors versus controls. Between-study heterogeneity was high (I 2â=â79.6-98.6%). There was little or no evidence of differential symptom prevalence based on hospitalization status, severity or follow-up duration. Neuropsychiatric symptoms are common and persistent after recovery from COVID-19. The literature on longer-term consequences is still maturing but indicates a particularly high prevalence of insomnia, fatigue, cognitive impairment and anxiety disorders in the first 6 months after infection
Topical Review on "Beta-beams"
Neutrino physics is traversing an exciting period, after the important
discovery that neutrinos are massive particles, that has implications from
high-energy physics to cosmology. A new method for the production of intense
and pure neutrino beams has been proposed recently: the ``beta-beam''. It
exploits boosted radioactive ions decaying through beta-decay. This novel
concept has been the starting point for a new possible future facility. Its
main goal is to address the crucial issue of the existence of CP violation in
the lepton sector. Here we review the status and the recent developments with
beta-beams. We discuss the original, the medium and high-energy scenarios as
well as mono-chromatic neutrino beams produced through ion electron-capture.
The issue of the degeneracies is mentioned. An overview of low energy
beta-beams is also presented. These beams can be used to perform experiments of
interest for nuclear structure, for the study of fundamental interactions and
for nuclear astrophysics.Comment: Topical Review for Journal of Physics G: Nuclear and Particle
Physics, published version, minor corrections, references adde
Viscerotropic disease: case definition and guidelines for collection, analysis, and presentation of immunization safety data
Viscerotropic disease (VTD) is defined as acute multiple organ system dysfunction that occurs following vaccination. The severity of VTD ranges from relatively mild multisystem disease to severe multiple organ system failure and death. The term VTD was first used shortly after the initial published reports in 2001 of febrile multiple organ system failure following yellow fever (YF) vaccination. To date, VTD has been reported only in association with YF vaccine and has been thus referred to as YF vaccine-associated viscerotropic disease (YEL-AVD)
Measurement of the cosmic ray spectrum above eV using inclined events detected with the Pierre Auger Observatory
A measurement of the cosmic-ray spectrum for energies exceeding
eV is presented, which is based on the analysis of showers
with zenith angles greater than detected with the Pierre Auger
Observatory between 1 January 2004 and 31 December 2013. The measured spectrum
confirms a flux suppression at the highest energies. Above
eV, the "ankle", the flux can be described by a power law with
index followed by
a smooth suppression region. For the energy () at which the
spectral flux has fallen to one-half of its extrapolated value in the absence
of suppression, we find
eV.Comment: Replaced with published version. Added journal reference and DO