5,374 research outputs found
Neutrino mass hierarchy and precision physics with medium-baseline reactors: Impact of energy-scale and flux-shape uncertainties
Nuclear reactors provide intense sources of electron antineutrinos,
characterized by few-MeV energy E and unoscillated spectral shape Phi(E).
High-statistics observations of reactor neutrino oscillations over
medium-baseline distances L ~ O(50) km would provide unprecedented
opportunities to probe both the long-wavelength mass-mixing parameters (delta
m^2 and theta_12) and the short-wavelength ones (Delta m^2 and theta_13),
together with the subtle interference effects associated with the neutrino mass
hierarchy (either normal or inverted). In a given experimental setting - here
taken as in the JUNO project for definiteness - the achievable hierarchy
sensitivity and parameter accuracy depend not only on the accumulated
statistics but also on systematic uncertainties, which include (but are not
limited to) the mass-mixing priors and the normalizations of signals and
backgrounds. We examine, in addition, the effect of introducing smooth
deformations of the detector energy scale, E -> E'(E), and of the reactor flux
shape, Phi(E) -> Phi'(E), within reasonable error bands inspired by
state-of-the-art estimates. It turns out that energy-scale and flux-shape
systematics can noticeably affect the performance of a JUNO-like experiment,
both on the hierarchy discrimination and on precision oscillation physics. It
is shown that a significant reduction of the assumed energy-scale and
flux-shape uncertainties (by, say, a factor of 2) would be highly beneficial to
the physics program of medium-baseline reactor projects. Our results also shed
some light on the role of the inverse-beta decay threshold, of geoneutrino
backgrounds, and of matter effects in the analysis of future reactor
oscillation data.Comment: 13 pages, including 17 figures. Minor changes in the text, references
added. To appear in Phys. Rev.
Probing the neutrino mass ordering with KM3NeT-ORCA: Analysis and perspectives
The discrimination of the two possible options for the neutrino mass ordering
(normal or inverted) is a major goal for current and future neutrino
oscillation experiments. Such goal might be reached by observing
high-statistics energy-angle spectra of events induced by atmospheric neutrinos
and antineutrinos propagating in the Earth matter. Large volume water-Cherenkov
detectors envisaged to this purpose include the so-called KM3NeT-ORCA project
(in seawater) and the IceCube-PINGU project (in ice). Building upon a previous
work focused on PINGU, we study in detail the effects of various systematic
uncertainties on the ORCA sensitivity to the mass ordering, for the reference
configuration with 9 m vertical spacing. We point out the need to control
spectral shape uncertainties at the percent level, the effects of better priors
on the theta-23 mixing parameter, and the benefits of an improved flavor
identification in reconstructed ORCA events.Comment: 15 pages, including 7 figures. A few paragraphs and references added.
Invited contribution to appear in the JPG Focus Issue on "Neutrino Mass and
Mass Ordering
Self-induced temporal instability from a neutrino antenna
It has been recently shown that the flavor composition of a self-interacting
neutrino gas can spontaneously acquire a time-dependent pulsating component
during its flavor evolution. In this work, we perform a more detailed study of
this effect in a model where neutrinos are assumed to be emitted in a
two-dimensional plane from an infinite line that acts as a neutrino antenna. We
consider several examples with varying matter and neutrino densities and find
that temporal instabilities with various frequencies are excited in a cascade.
We compare the numerical calculations of the flavor evolution with the
predictions of linearized stability analysis of the equations of motion. The
results obtained with these two approaches are in good agreement in the linear
regime, while a dramatic speed-up of the flavor conversions occurs in the
non-linear regime due to the interactions among the different pulsating modes.
We show that large flavor conversions can take place if some of the temporal
modes are unstable for long enough, and that this can happen even if the matter
and neutrino densities are changing, as long as they vary slowly.Comment: v2: revised version, 15 pages, 6 figures. Minor changes. Typos
removed, figures improved. Matches the version accepted on JCA
Joint short- and long-baseline constraints on light sterile neutrinos
Recent studies provide evidence that long-baseline (LBL) experiments are sensitive to the extra CP phases involved with light sterile neutrinos, whose existence is suggested by several anomalous short-baseline (SBL) results. We show that, within the 3+1 scheme, the combination of the existing SBL data with the LBL results coming from the two currently running experiments, NO\u3bdA and T2K, enables us to simultaneously constrain two active-sterile mixing angles, \u3b814 and \u3b824, and two CP phases, \u3b413 61\u3b4 and \u3b414, although the information on the second CP phase is still weak. The two mixing angles are basically determined by the SBL data, while the two CP phases are constrained by the LBL experiments, once the information coming from the SBL setups is taken into account. We also assess the robustness or fragility of the estimates of the standard 3-flavor parameters in the more general 3+1 scheme. To this regard we find that (i) the indication of CP violation found in the 3-flavor analyses persists also in the 3+1 scheme, with \u3b413 61\u3b4 having still its best-fit value around 12\u3c0/2, (ii) the 3-flavor weak hint in favor of the normal hierarchy becomes even less significant when sterile neutrinos come into play, (iii) the weak indication of nonmaximal \u3b823 (driven by NO\u3bdA disappearance data) persists in the 3+1 scheme, where maximal mixing is disfavored at almost the 90% C.L. in both normal and inverted mass hierarchy, and (iv) the preference in favor of one of the two octants of \u3b823 found in the 3-flavor framework (higher octant for inverted mass hierarchy) is completely washed out in the 3+1 scheme
Computer Science Begins at Fisher
In lieu of an abstract, below is the essay\u27s first paragraph.
Dr. Rev. Michael Costanzo asked me to write an article for Verbum 2012. I know Father Costanzo as my family is a member of the Church of the Holy Spirit in Penfield where Father Costanzo often helps out. I thought I would write a little about my experience at St. John Fisher College for the Alumni Corner. It has been over 30 years since I first walked onto the St. John Fisher College campus in the fall of 1979 as an incoming freshman, but it doesn’t seem that long ago. I wasn’t sure what I wanted to do with my life as I entered college, but was excited about beginning college. It wasn’t easy for me choosing a college when I didn’t know what I wanted to do with my life. I was from Rochester and I chose Fisher because I decided to stay local, Fisher had a very good reputation in many different academic disciplines, and I liked the fact that, at Fisher, religion would be a part of the academic life. At that time, Fisher was mainly a commuter school with over 60% of the students commuting. There wasn’t much dorm space at that time. A main reason I commuted was to save money. To this day I regret that decision as I didn’t get the full experience of college life by living on campus. I came for my classes and immediately left after my last class each day to head to a part-time job or to return home
Neutrino masses and mixings: Status of known and unknown parameters
Within the standard 3nu mass-mixing framework, we present an up-to-date
global analysis of neutrino oscillation data (as of January 2016), including
the latest available results from experiments with atmospheric neutrinos
(Super-Kamiokande and IceCube DeepCore), at accelerators (first T2K anti-nu and
NOvA nu runs in both appearance and disappearance mode), and at short-baseline
reactors (Daya Bay and RENO far/near spectral ratios), as well as a reanalysis
of older KamLAND data in the light of the "bump" feature recently observed in
reactor spectra. We discuss improved constraints on the five known oscillation
parameters (delta m^2, |Delta m^2|, sin^2theta_12, sin^2theta_13,
sin^2theta_23), and the status of the three remaining unknown parameters: the
mass hierarchy, the theta_23 octant, and the possible CP-violating phase delta.
With respect to previous global fits, we find that the reanalysis of KamLAND
data induces a slight decrease of both delta m^2 and sin^2theta_12, while the
latest accelerator and atmospheric data induce a slight increase of |Delta
m^2|. Concerning the unknown parameters, we confirm the previous intriguing
preference for negative values of sin(delta) [with best-fit values around
sin(delta) ~ -0.9], but we find no statistically significant indication about
the theta_23 octant or the mass hierarchy (normal or inverted). Assuming an
alternative (so-called LEM) analysis of NOvA data, some delta ranges can be
excluded at >3 sigma, and the normal mass hierarchy appears to be slightly
favored at 90% C.L. We also describe in detail the covariances of selected
pairs of oscillation parameters. Finally, we briefly discuss the implications
of the above results on the three non-oscillation observables sensitive to the
(unknown) absolute nu mass scale: the sum of nu masses, the effective nu_e
mass, and the effective Majorana mass.Comment: 15 pages, 9 figures, 2 tables. Invited contribution prepared for the
Nuclear Physics B Special Issue on "Neutrino Oscillations" celebrating the
Nobel Prize in Physics 201
Fast flavor conversions of supernova neutrinos: Classifying instabilities via dispersion relations
Supernova neutrinos can exhibit a rich variety of flavor conversion
mechanisms. In particular, they can experience "fast" self-induced flavor
conversions almost immediately above the core. Very recently, a novel method
has been proposed to investigate these phenomena, in terms of the dispersion
relation for the complex frequency and wave number (,) of
disturbances in the mean field of the flavor coherence. We discuss
a systematic approach to such instabilities, originally developed in the
context of plasma physics, and based of the time-asymptotic behavior of the
Green's function of the system. Instabilities are typically seen to emerge for
complex , and can be further characterized as convective (moving away
faster than they spread) and absolute (growing locally), depending on
-dependent features. Stable cases emerge when (but not ) is
complex, leading to disturbances damped in space, or when both and
are real, corresponding to complete stability. The analytical classification of
both unstable and stable modes leads not only to qualitative insights about
their features but also to quantitative predictions about the growth rates of
instabilities. Representative numerical solutions are discussed in a simple
two-beam model of interacting neutrinos. As an application, we argue that
supernova and binary neutron star mergers exhibiting a "crossing" in the
electron lepton number would lead to an absolute instability in the flavor
content of the neutrino gas.Comment: (v2, revised version: 25 pages, 15 pdf figures. Minor changes.
Figures improved. Matches the version published on PRD
Joycean Babeling: Scattered Language in \u27Oxen of the Sun\u27
This paper considers James Joyce\u27s Ulysses. It focuses specifically on Joyce\u27s use of language in Oxen of the Sun. I interpret the episode, which figures the conception, gestation, and birth of language alongside a literal birth, as a construction and deconstruction of the English language that suggests its ultimate inefficacy. I framed my close reading of the chapter with theoretical work by Thomas Aquinas, Ferdinand de Saussure, Walter Benjamin, and Jacques Derrida. I argue that Joyce, by acknowledging the limits of language even as he continues to write, reaffirms and reinscribes the role of the Artist. I contend that Joyce premeditates the theoretical trajectory of the twentieth-century deconstruction in his Babelian scattering of language. To develop this argument, I delve into the theoretical work of Thomas Aquinas\u27 Compendium Theologaie and Summa Theologaie, Ferdinand de Saussure\u27s Courses in General Linguistics, Walter Benjamin\u27s on Languages as Such and the Nature of Man, and Jacques Derrida\u27s Differance. The bulk of my paper consists of a formal analysis of central passages in the text, which revolves around one key passage concerning the utterance of the Word. I deal specifically with Benjamin\u27s considerations on naming, Saussurian semiotics, and Derridean differance
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