200 research outputs found
Large mixing angle solution to the solar neutrino problem and random matter density perturbations
There are reasons to believe that mechanisms exist in the solar interior
which lead to random density perturbations in the resonant region of the Large
Mixing Angle solution to the solar neutrino problem. We find that, in the
presence of these density perturbations, the best fit point in the
(sin^2(2\theta), Delta_m^2) parameter space moves to smaller values, compared
with the values obtained for the standard LMA solution. Combining solar data
with KamLAND results, we find a new compatibility region, which we call
VERY-LOW LMA, where sin^2(2\theta) ~ 0.6 and Delta_m^2~2e-5 eV^2, for random
density fluctuations of order 5% < \xi< 8%. We argue that such values of
density fluctuations are still allowed by helioseismological observations at
small scales of order 10 - 1000 km deep inside the solar core.Comment: References and discussion added, with some small numerical
corrections implemente
Effects of magnetohydrodynamics matter density fluctuations on the solar neutrino resonant spin-flavor precession
Taking into account the stringent limits from helioseismology observations on
possible matter density fluctuations described by magnetohydrodynamics theory,
we find the corresponding time variations of solar neutrino survival
probability due to the resonant spin-flavor precession phenomenon with
amplitude of order O(10%). We discuss the physics potential of high statistics
real time experiments, like as Superkamiokande, to observe the effects of such
magnetohydrodynamics fluctuations on their data. We conclude that these
observations could be thought as a test of the resonant spin-flavor precession
solution to the solar neutrino anomaly.Comment: 16 pages, 3 figure
Influence of the solar and density perturbations on the neutrino parameters
There are reasons to believe that the solar matter density fluctuates around an equilibrium profile. One of these reasons is a resonance between the Alfvén waves and the g-modes inside the Sun that creates spikes in the density profile. The neutrinos are created in the solar core and passing through these spikes feel them as a noisy perturbation, whose correlation length is given by the distance between the spikes. When we consider these perturbations on the density profile, the values of the neutrino parameters necessary to obtain a solution to the solar neutrino problem are affected. In particular, in the present work, we show that the values of the parameters of mass and mixing angle that satisfy both the Large Mixing Angle solution to the solar neutrinos and the data from KamLAND - that observes neutrinos created in earth nuclear reactors - are shifted in the direction of lower values as the amplitude of the density noise increases. This means that, depending on the new data of KamLAND and other detectors, it can be necessary to invoke random perturbations in the Sun to recover compatibility with solar neutrino observations. In this case, the neutrino observations will be used as a real probe of the solar interior, giving information of the density profile in the central part of the Sun, which can not be observed directly.1729173
Measurement of the (, Ar) total hadronic cross section at the LArIAT experiment
We present the first measurement of the negative pion total hadronic cross
section on argon, which we performed at the Liquid Argon In A Testbeam (LArIAT)
experiment. All hadronic reaction channels, as well as hadronic elastic
interactions with scattering angle greater than 5~degrees are included. The
pions have a kinetic energies in the range 100-700~MeV and are produced by a
beam of charged particles impinging on a solid target at the Fermilab Test Beam
Facility. LArIAT employs a 0.24~ton active mass Liquid Argon Time Projection
Chamber (LArTPC) to measure the pion hadronic interactions. For this
measurement, LArIAT has developed the ``thin slice method", a new technique to
measure cross sections with LArTPCs. While generally higher than the
prediction, our measurement of the (,Ar) total hadronic cross section is
in agreement with the prediction of the Geant4 model when considering a model
uncertainty of 5.1\%.Comment: 15 pages, 15 figures, 3 tables, accepted by PR
The Liquid Argon In A Testbeam (LArIAT) Experiment
The LArIAT liquid argon time projection chamber, placed in a tertiary beam of
charged particles at the Fermilab Test Beam Facility, has collected large
samples of pions, muons, electrons, protons, and kaons in the momentum range
300-1400 MeV/c. This paper describes the main aspects of the detector and
beamline, and also reports on calibrations performed for the detector and
beamline components
Search for heavy neutral leptons in electron-positron and neutral-pion final states with the MicroBooNE detector
We present the first search for heavy neutral leptons (HNL) decaying into
or final states in a liquid-argon time projection
chamber using data collected with the MicroBooNE detector. The data were
recorded synchronously with the NuMI neutrino beam from Fermilab's Main
Injector corresponding to a total exposure of protons on
target. We set upper limits at the confidence level on the mixing
parameter in the mass ranges MeV for the channel and MeV for
the channel, assuming . These limits represent the most stringent constraints in the
mass range MeV and the first constraints from a direct
search for decays.Comment: Version as accepted by Physical Review Letters, some presentational
changes and updated references, no changes to result
First measurement of quasi-elastic baryon production in muon anti-neutrino interactions in the MicroBooNE detector
We present the first measurement of the cross section of Cabibbo-suppressed
baryon production, using data collected with the MicroBooNE detector
when exposed to the neutrinos from the Main Injector beam at the Fermi National
Accelerator Laboratory. The data analyzed correspond to
protons on target of neutrino mode running and protons on
target of anti-neutrino mode running. An automated selection is combined with
hand scanning, with the former identifying five candidate production
events when the signal was unblinded, consistent with the GENIE prediction of
events. Several scanners were employed, selecting between three
and five events, compared with a prediction from a blinded Monte Carlo
simulation study of events. Restricting the phase space to only
include baryons that decay above MicroBooNE's detection thresholds,
we obtain a flux averaged cross section of
cmAr, where statistical and systematic uncertainties are combined
First Measurement of Differential Cross Sections for Muon Neutrino Charged Current Interactions on Argon with a Two-proton Final State in the MicroBooNE Detector
We present the first measurement of differential cross sections for
charged-current muon neutrino interactions on argon with one muon, two protons,
and no pions in the final state. Such interactions leave the target nucleus in
a two-particle two-hole state; these states are of great interest, but
currently there is limited information about their production in
neutrino-nucleus interactions. Detailed investigations of the production of
two-particle two-hole states are vital to support upcoming experiments
exploring the nature of the neutrino, and the development of the liquid-argon
time-projection-chamber has made possible the isolation of such final states.
The opening angle between the two protons, the angle between the total proton
momentum and the muon, and the total transverse momentum of the final state
system are sensitive to the underlying physics processes as embodied in a
variety of models. Realistic initial-state momentum distributions are shown to
be important in reproducing the data.Comment: To be submitted to PR
- âŠ