661 research outputs found
No collective neutrino flavor conversions during the supernova accretion phase
The large neutrino fluxes emitted with a distinct flavor hierarchy from
core-collapse supernovae (SNe) during the post-bounce accretion phase, offer
the best opportunity to detect effects from neutrino flavor oscillations. We
perform a dedicated study of the SN neutrino flavor evolution during the
accretion phase, using results from recent neutrino radiation hydrodynamics
simulations. In contrast to what expected in the presence of only
neutrino-neutrino interactions, we find that the multi-angle effects associated
with the dense ordinary matter suppress collective oscillations. This is
related to the high matter densities during the accretion phase in
core-collapse SNe of massive iron-core progenitors. The matter suppression
implies that neutrino oscillations will start outside the neutrino transport
region and therefore will have a negligible impact on the neutrino heating and
the explosion dynamics. Furthermore, the possible detection of the next
galactic SN neutrino signal from the accretion phase, based on the usual
Mikheyev- Smirnov-Wolfenstein effect in the SN mantle and Earth matter effects,
can reveal the neutrino mass hierarchy in the case that the mixing angle
is not very small.Comment: (4 pages, 4 eps figures, v2 revised version. Discussion clarified.
Matches the version published on PRL
Stability analysis of collective neutrino oscillations in the supernova accretion phase with realistic energy and angle distributions
We revisit our previous results on the matter suppression of self-induced
neutrino flavor conversions during a supernova (SN) accretion phase, performing
a linearized stability analysis of the neutrino equations of motion, in the
presence of realistic SN density profiles. In our previous numerical study, we
used a simplified model based on an isotropic neutrino emission with a single
typical energy. Here, we take into account realistic neutrino energy and angle
distributions. We find that multi-energy effects have a sub-leading impact in
the flavor stability of the SN neutrino fluxes with respect to our previous
single-energy results. Conversely, realistic forward-peaked neutrino angular
distributions would enhance the matter suppression of the self-induced
oscillations with respect to an isotropic neutrino emission. As a result, in
our models for iron-core SNe, collective flavor conversions have a negligible
impact on the characterization of the observable neutrino signal during the
accretion phase. Instead, for a low-mass O-Ne-Mg core SN model, with lower
matter density profile and less forward-peaked angular distributions,
collective conversions are possible also at early times.Comment: v2: 8 pages, 3 eps figures. Revised version. Minor changes.
References updated. Matches the version published on PR
Fiber Bragg Grating sensors for deformation monitoring of GEM foils in HEP detectors
Fiber Bragg Grating (FBG) sensors have been so far mainly used in high energy
physics (HEP) as high precision positioning and re-positioning sensors and as
low cost, easy to mount, radiation hard and low space- consuming temperature
and humidity devices. FBGs are also commonly used for very precise strain
measurements. In this work we present a novel use of FBGs as flatness and
mechanical tensioning sensors applied to the wide Gas Electron Multiplier (GEM)
foils of the GE1/1 chambers of the Compact Muon Solenoid (CMS) experiment at
Large Hadron Collider (LHC) of CERN. A network of FBG sensors has been used to
determine the optimal mechanical tension applied and to characterize the
mechanical stress applied to the foils. The preliminary results of the test
performed on a full size GE1/1 final prototype and possible future developments
will be discussed.Comment: Four pages, seven figures. Presented by Michele Caponero at IWASI
2015, Gallipoli (Italy
An Introduction to the Viable Systems Approach and its Contribution to Marketing
Organizations are increasingly challenged by dynamism and turbulence that determine conditions of complexity in decision making. The aim of this paper is to highlight the need for a general frame of reference for management and marketing and to justify why adopting a systems approach is adequate at both theoretical and practical level. Specifically, the purpose of this paper is to explain why a systems approach is needed to understand business and market dynamics, and why the VSA
may represent a good integrator of management and marketing theories and practices. The paper begins with a brief review of systems theories that have been
proposed in the general context of management and marketing. It proceeds by illustrating the fundamental principles and concepts of the VSA and its contribution to
marketing. The paper closes by discussing future research avenues and suggesting implications for researchers and practitioners
Analysis of matter suppression in collective neutrino oscillations during the supernova accretion phase
The usual description of self-induced neutrino flavor conversions in core
collapse supernovae (SNe) is based on the dominance of the neutrino density
n_nu over the net electron density n_e. However, this condition is not met
during the post-bounce accretion phase, when the dense matter in a SN is piled
up above the neutrinosphere. As recently pointed-out, a dominant matter term in
the anisotropic SN environment would dephase the flavor evolution for neutrinos
traveling on different trajectories, challenging the occurrence of the
collective behavior in the dense neutrino gas. Using the results from recent
long term simulations of core-collapse SN explosions, based on three flavor
Boltzmann neutrino transport in spherical symmetry, we find that both the
situations of complete matter suppression (when n_e >> n_nu) and matter-induced
decoherence (when n_e \gtrsim n_nu) of flavor conversions are realized during
the accretion phase. The matter suppression at high densities prevents any
possible impact of the neutrino oscillations on the neutrino heating and hence
on the dynamics of the explosion. Furthermore, it changes the interpretation of
the Earth matter effect on the SN neutrino signal during the accretion phase,
allowing the possibility of the neutrino mass hierarchy discrimination at not
too small values of the leptonic mixing angle \theta_{13} (i.e.
\sin^2{\theta}_{13} \gtrsim 10^{-3}).Comment: Revised version (15 pages, 13 eps figures) published on Physical
Review D. Discussion enlarged, references update
Light sterile neutrino production in the early universe with dynamical neutrino asymmetries
Light sterile neutrinos mixing with the active ones have been recently
proposed to solve different anomalies observed in short-baseline oscillation
experiments. These neutrinos can also be produced by oscillations of the active
neutrinos in the early universe, leaving possible traces on different
cosmological observables. Here we perform an updated study of the neutrino
kinetic equations in (3+1) and (2+1) oscillation schemes, dynamically evolving
primordial asymmetries of active neutrinos and taking into account for the
first time CP-violation effects. In the absence of neutrino asymmetries,
eV-mass scale sterile neutrinos would be completely thermalized creating a
tension with respect to the CMB, LSS and BBN data. In the past literature,
active neutrino asymmetries have been invoked as a way to inhibit the sterile
neutrino production via the in-medium suppression of the sterile-active mixing
angle. However, neutrino asymmetries also permit a resonant sterile neutrino
production. We find that if the active species have equal asymmetries L, a
value |L|=10^{-3} is required to start suppressing the resonant sterile
production, roughly an order of magnitude larger than what previously expected.
When active species have opposite asymmetries the sterile abundance is further
enhanced, requiring an even larger |L|\simeq 10^{-2} to start suppressing their
production. In the latter case, CP-violation (naturally expected) further
exacerbates the phenomenon. Some consequences for cosmological observables are
briefly discussed: for example, it is likely that moderate suppressions of the
sterile species production are associated with significant spectral distortions
of the active neutrino species, with potentially interesting phenomenological
consequences especially for BBN.Comment: (v2: 22 pages, 10 eps figures. Revised version. Typos removed,
reference updated. Matches the version published on PRD.
Properties of potential eco-friendly gas replacements for particle detectors in high-energy physics
Gas detectors for elementary particles require F-based gases for optimal performance.
Recent regulations demand the use of environmentally unfriendly F-based gases to be limited or
banned. This work studies properties of potential eco-friendly gas replacements by computing the
physical and chemical parameters relevant for use as detector media, and suggests candidates to be
considered for experimental investigation
Candidate eco-friendly gas mixtures for MPGDs
Modern gas detectors for detection of particles require F-based gases for optimal performance.Recent regulations demand the use of environmentally unfriendly F-based gases t o be limited or banned. This review studies properties of potential eco-friendly gas candidate replacements
Properties of potential eco-friendly gas replacements for particle detectors in high-energy physics
Modern gas detectors for detection of particles require F-based gases for
optimal performance. Recent regulations demand the use of environmentally
unfriendly F-based gases to be limited or banned. This review studies
properties of potential eco-friendly gas candidate replacements.Comment: 38 pages, 9 figures, 8 tables. To be submitted to Journal of
Instrumentatio
An integrated reconstruction of the multiannual wave pattern in the gulf of naples (South-Eastern Tyrrhenian Sea, Western Mediterranean Sea)
Surface gravity waves retrieved by a network of HF (High Frequency) radars and measured in situ by an ADCP (Acoustic Doppler Current Profiler) current meter connected to an elastic beacon were used to carry out a multiple-year characterization of the wave field of the Gulf of Naples (south-eastern Tyrrhenian Sea, western Mediterranean). The aim of the work was to create a climatology of the study area and to demonstrate the potential of an integrated platform for coastal studies. The patterns recorded by the different instruments were in agreement with the wave climatology of the southern Tyrrhenian Sea as well as with previous scores for the same area. The results presented in this work also highlight seasonal and interannual consistency in the wave patterns for each site. In a wider context, this study demonstrates the potential of HF radars as long-term monitoring tools of the wave field in coastal basins, and supports the development of integrated observatories to address large-scale scientific challenges such as coastal ocean dynamics and the impact of global change on the local dynamics
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