2,048 research outputs found
Neutrino Oscillations at Reactors: What Next?
We shortly review past and future experiments at reactors aimed at searches
for neutrino masses and mixing. We also consider new idea to search at
Krasnoyarsk for small mixing angle oscillations in the atmosheric neutrino mass
parameter region.Comment: 9 pages, LaTeX 2.09, 6 Postscript figures. Talk given at
Non-Accelerator New Physics Conference, Dubna, 28.06-03.07.199
The Search for Neutrino Oscillations numubar->nuebar with KARMEN
The neutrino experiment KARMEN is situated at the beam stop neutrino source
ISIS. It provides numu's, nue's and numubar's in equal intensities from the pi+
mu+ decay at rest (DAR). The oscillation channel numub->nueb is investigated in
the appearance mode with a 56t liquid scintillation calorimeter at a mean
distance of 17.7m from the nu source looking for p(nue,e+)n reactions. The
cosmic induced background for this oscillation search could be reduced by a
factor of 40 due to an additional veto counter installed in 1996. In the data
collected through 1997 and 1998 no potential oscillation event was observed.
Using a unified approach to small signals this leads to an upper limit for the
mixing angle of sin**2(2t) < 1.3x10^{-3} (90%CL) at large Dm**2. The excluded
area in (sin**2(2t),Dm**2) covers almost entirely the favored region defined by
the LSND numub->nueb evidence.Comment: Proceedings Contribution to Neutrino98 in Takayama, Japan, June 4-9,
1998; 13 pages, including 4 figure
Constraints from Neutrino Oscillation Experiments on the Effective Majorana Mass in Neutrinoless Double -Decay
We determine the possible values of the effective Majorana neutrino mass in the different phenomenologically viable three
and four-neutrino scenarios. The quantities () denote the elements of the neutrino mixing matrix and the
Majorana neutrino masses () are ordered as Assuming in the three-neutrino case and in the
four-neutrino case, we discuss, in particular, how constraints on
depend on the mixing angle relevant in solar neutrino oscillations and on the
three mass-squared differences obtained from the analyses of the solar,
atmospheric and LSND data. If neutrinoless double -decay proceeds via
the mechanism involving , conclusions about neutrinoless double
-decay can be drawn. If one of the two viable four-neutrino schemes
(Scheme A) is realized in nature, can be as large as 1 eV and
neutrinoless double -decay could possibly be discovered in the near
future. In this case a Majorana CP phase of the mixing matrix could be
determined. In the other four-neutrino scheme (Scheme B) there is an upper
bound on of the order of eV. In the case of three-neutrino
mixing the same is true if the neutrino mass spectrum is hierarchical, however,
if there exist two quasi-degenerate neutrinos and the first neutrino has a much
smaller mass, values of as large as eV are possible.Comment: 15 pages, REVTEX, 2 figures, final version to be published in Phys.
Lett.
The Cr neutrino source and Borexino: a desirable marriage
Exposure to a Cr neutrino source as that used in Gallex will provide
an excellent overall performance test of Borexino, which should collect about
1400 source induced events, with an initial rate of about 35 counts per day.
This will be particularly important if MSW-small-angle turns out to be the
solution of the solar neutrino problem. In addition, if an independent,
accurate calibration is available, one will have an interesting experiment on
neutrino properties: as an example, a neutrino magnetic moment of the order
could be detected/excluded at the 90\% C.L.Comment: 7 pages, RevTeX, plus 3 postscripts figures, tarred, compresse
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
Inverse Beta Decay in a Nonequilibrium Antineutrino Flux from a Nuclear Reactor
The evolution of the reactor antineutrino spectrum toward equilibrium above
the inverse beta-decay threshold during the reactor operating period and the
decay of residual antineutrino radiation after reactor shutdown are considered.
It is found that, under certain conditions, these processes can play a
significant role in experiments seeking neutrino oscillations.Comment: 8 pages including 5 ps figure
Billing by residents and attending physicians in family medicine: the effects of the provider, patient, and visit factors
BACKGROUND:
Medical billing and coding are critical components of residency programs since they determine the revenues and vitality of residencies. It has been suggested that residents are less likely to bill higher evaluation and management (E/M) codes compared with attending physicians. The purpose of this study is to assess the variation in billing patterns between residents and attending physicians, considering provider, patient, and visit characteristics.
METHOD:
A retrospective cohort study of all established outpatient visits at a family medicine residency clinic over a 5-year period was performed. We employed the logistic regression methodology to identify residents' and attending physicians' variations in coding E/M service levels. We also employed Poisson regression to test the sensitivity of our result.
RESULTS:
Between January 5, 2009 and September 25, 2015, 98,601 visits to 116 residents and 18 attending physicians were reviewed. After adjusting for provider, patient, and visit characteristics, residents billed higher E/M codes less often compared with attending physicians for comparable visits. In comparison with attending physicians, the odds ratios for billing higher E/M codes were 0.58 (p = 0.01), 0.56 (p = 0.01), and 0.63 (p = 0.01) for the third, second, and first years of postgraduate training, respectively. In addition to the main factors of patient age, medical conditions, and number of addressed problems, the gender of the provider was also implicated in the billing variations.
CONCLUSION:
Residents are less likely to bill higher E/M codes than attending physicians are for similar visits. While these variations are known to contribute to lost revenues, further studies are required to explore their effect on patient care in relation to attendings' direct involvement in higher E/M-coded versus their indirect involvement in lower E/M-coded visits
The Kr2Det project: Search for mass-3 state contribution |U_{e3}|^2 to the electron neutrino using a one reactor - two detector oscillation experiment at Krasnoyarsk underground site
The main physical goal of the project is to search with reactor antineutrinos
for small mixing angle oscillations in the atmospheric mass parameter region
around {\Delta}m^{2}_{atm} ~ 2.5 10^{-3} eV^2 in order to find the element
U_{e3} of the neutrino mixing matrix or to set a new more stringent constraint
(U_{e3} is the contribution of mass-3 state to the electron neutrino flavor
state). To achieve this we propose a "one reactor - two detector" experiment:
two identical antineutrino spectrometers with 50 ton liquid scintillator
targets located at ~100 m and ~1000 m from the Krasnoyarsk underground reactor
(~600 mwe). In no-oscillation case ratio of measured positron spectra of the
\bar{{\nu}_e} + p \to e^{+} + n reaction is energy independent. Deviation from
a constant value of this ratio is the oscillation signature. In this scheme
results do not depend on the exact knowledge of the reactor power, nu_e
spectra, burn up effects, target volumes and, which is important, the
backgrounds can periodically be measured during reactor OFF periods. In this
letter we present the Krasnoyarsk reactor site, give a schematic description of
the detectors, calculate the neutrino detection rates and estimate the
backgrounds. We also outline the detector monitoring and calibration
procedures, which are of a key importance. We hope that systematic
uncertainties will not accede 0.5% and the sensitivity U^{2}_{e3} ~4 10^{-3}
(at {\Delta}m^{2} = 2.5 10^{-3} eV^2) can be achieved.Comment: Latex 2e, 9 pages and 5 ps figure
Lepton Mixing Matrix in Standard Model Extended by One Sterile Neutrino
We consider the simplest extension of the standard electroweak model by one
sterile neutrino that allows for neutrino masses and mixing. We find that its
leptonic sector contains much less free physical parameters than previously
realized. In addition to the two neutrino masses, the lepton mixing matrix in
charged current interactions involves (n-1) free physical mixing angles for n
generations. The mixing matrix in neutral current interactions of neutrinos is
completely fixed by the two masses. Both interactions conserve CP. We
illustrate the phenomenological implications of the model by vacuum neutrino
oscillations, tritium beta decay and neutrinoless double beta decay. It turns
out that, due to the revealed specific structure in its mixing matrix, the
model with any n generations cannot accommodate simultaneously the data by
KamLAND, K2K and CHOOZ.Comment: 14 pages, no figures; version 2: (1) added a short paragraph at the
end of subsec 2.2 to record the counting of physical parameters for any
numbers of generations and sterile neutrinos for completeness; (2) added a
note in ref list, item [18] to quote and comment on an earlier work; (3)
added the second paper to ref list, item [17]; (4) fixed typo
The symmetry of charge order in cuprates
Charge-ordered ground states permeate the phenomenology of 3d-based
transition metal oxides, and more generally represent a distinctive hallmark of
strongly-correlated states of matter. The recent discovery of charge order in
various cuprate families fueled new interest into the role played by this
incipient broken symmetry within the complex phase diagram of high-Tc
superconductors. Here we use resonant X-ray scattering to resolve the main
characteristics of the charge-modulated state in two cuprate families: Bi2201
and YBCO. We detect no signatures of spatial modulations along the nodal
direction in Bi2201, thus clarifying the inter-unit-cell momentum-structure of
charge order. We also resolve the intra-unit-cell symmetry of the charge
ordered state, which is revealed to be best represented by a bond-order with
modulated charges on the O-2p orbitals and a prominent d-wave character. These
results provide insights on the microscopic description of charge order in
cuprates, and on its origin and interplay with superconductivity.Comment: A high-resolution version with supplementary material can be found
at:
http://www.phas.ubc.ca/~quantmat/ARPES/PUBLICATIONS/Articles/CDW_symmetry.pd
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