17,899 research outputs found
The Effects of Inlet Flow Modification on Cavitating Inducer Performance
This paper explores the effect of inlet flow modification on the cavitating and noncavitating performance of two cavitating inducers, one of simple helical design and the other a model of the low-pressure LOX pump in the Space Shuttle Main Engine. The modifications were generated by sections of honeycomb, both uniform and nonuniform. Significant improvement in the performance over a wide range of flow coefficients resulted from the use of either honeycomb section. Measurements of the axial and swirl velocity profiles of the flows entering the inducers were made in order to try to understand the nature of the inlet flow and the manner in which it is modified by the honeycomb sections
Global status of neutrino oscillation parameters after Neutrino-2012
Here we update the global fit of neutrino oscillations in arXiv:1103.0734 and
arXiv:1108.1376 including the recent measurements of reactor antineutrino
disappearance reported by the Double Chooz, Daya Bay and RENO experiments,
together with latest MINOS and T2K appearance and disappearance results, as
presented at the Neutrino-2012 conference. We find that the preferred global
fit value of is quite large: for
normal and inverted neutrino mass ordering, with now excluded
at more than 10. The impact of the new measurements over
the other neutrino oscillation parameters is discussed as well as the role of
the new long-baseline neutrino data and the atmospheric neutrino analysis in
the determination of a non-maximal atmospheric angle .Comment: Note added, matches published version in Physical Review
Neutrino oscillations refitted
Here we update our previous global fit of neutrino oscillations by including
the recent results which have appeared since the Neutrino-2012 conference.
These include the measurements of reactor anti-neutrino disappearance reported
by Daya Bay and RENO, together with latest T2K and MINOS data including both
disappearance and appearance channels. We also include the revised results from
the third solar phase of Super-Kamiokande, SK-III, as well as new solar results
from the fourth phase of Super-Kamiokande, SK-IV. We find that the preferred
global determination of the atmospheric angle is consistent with
maximal mixing. We also determine the impact of the new data upon all the other
neutrino oscillation parameters with emphasis on the increasing sensitivity to
the CP phase, thanks to the interplay between accelerator and reactor data. In
the appendix we present the updated results obtained after the inclusion of new
reactor data presented at the Neutrino 2014 conference. We discuss their impact
on the global neutrino analysis.Comment: 13 pages, 5 figures, 2 tables. An appendix providing updated results
after Neutrino-2014 Conference is added. Matches published version in
Physical Review
Lepton Flavour Violation in a Left-Right Symmetric Model
We consider in this paper a Left-Right symmetric gauge model in which a
global lepton-number-like symmetry is introduced and broken spontaneously at a
scale that could be as low as 10^4 GeV or so. The corresponding physical
Nambu-Goldstone boson, which we call majoron and denote J, can have tree-level
flavour-violating couplings to the charged fermions, leading to sizeable
majoron-emitting lepton-flavour-violating weak decays. We consider explicitly a
leptonic variant of the model and show that the branching ratios for \mu ->
e+J, \tau -> e + J and \tau -> \mu + J decays can be large enough to fall
within the sensitivities of future \mu and \tau factories. On the other hand
the left-right gauge symmetry breaking scale may be as low as few TeV.Comment: LaTeX, 16 pages, 3 PS figures, uses JHEP.cls, published versio
A Radial Velocity Survey for LMC Microlensed Sources
We propose a radial velocity survey with the aim to resolve the current
dispute on the LMC lensing: in the pro-macho hypothesis the lenses are halo
white dwarfs or machos in general; in the pro-star hypothesis both the lenses
and the sources are stars in various observed or hypothesized structures of the
Magellanic Clouds and the Galaxy. Star-star lensing should prefer sources at
the backside or behind the LMC disc because lensing is most efficient if the
source is located a few kpc behind a dense screen of stars, here the thin disc
of the LMC. This signature of self-lensing can be looked for by a radial
velocity survey since kinematics of the stars at the back can be markedly
different from that of the majority of stars in the cold, rapidly rotating disc
of the LMC. Detailed simulations of effect together with optimal strategies of
carrying out the proposed survey are reported here. Assuming that the existing
30 or so alerted stars in the LMC are truely microlensed stars, their
kinematics can test the two lensing scenarios; the confidence level varies with
the still very uncertain structure of the LMC. Spectroscopy of the existing
sample and future events requires about two or three good-seeing nights per
year at a 4m-8m class southern telescope, either during the amplification phase
or long after.Comment: minor changes of text, ApJ accepte
Bound-state dark matter with Majorana neutrinos
We propose a simple scenario in which dark matter (DM) emerges as a stable
neutral hadronic thermal relics, its stability following from an exact
symmetry. Neutrinos pick up radiatively induced
Majorana masses from the exchange of colored DM constituents. There is a common
origin for both dark matter and neutrino mass, with a lower bound for
neutrinoless double beta decay. Direct DM searches at nuclear recoil
experiments will test the proposal, which may also lead to other
phenomenological signals at future hadron collider and lepton flavour violation
experiments.Comment: 9 pages, 4 figures. arXiv admin note: text overlap with
arXiv:1803.0852
Hydrodynamic fluctuations in relativistic superfluids
The Hamiltonian formulation of superfluids based on noncanonical Poisson
brackets is studied in detail. The assumption that the momentum density is
proportional to the flow of the conserved energy is shown to lead to the
covariant relativistic theory previously suggested by Khalatnikov, Lebedev and
Carter, and some potentials in this theory are given explicitly. We discuss
hydrodynamic fluctuations in the presence of dissipative effects and we derive
the corresponding set of hydrodynamic correlation functions. Kubo relations for
the transport coefficients are obtained.Comment: 13 pages, no figures, two references adde
Calculable inverse-seesaw neutrino masses in supersymmetry
We provide a scenario where naturally small and calculable neutrino masses
arise from a supersymmetry breaking renormalization-group-induced vacuum
expectation value. We adopt a minimal supergravity scenario without ad hoc
supersymmetric mass parameters. The lightest supersymmetric particle can be an
isosinglet scalar neutrino state, potentially viable as WIMP dark matter
through its Higgs new boson coupling. The scenario leads to a plethora of new
phenomenological implications at accelerators including the Large Hadron
Collider.Comment: LaTeX, 5 pages, 4 figures. Comments and references added. Final
version to appear in PR
Lepton flavor violation and non-unitary lepton mixing in low-scale type-I seesaw
Within low-scale seesaw mechanisms, such as the inverse and linear seesaw,
one expects (i) potentially large lepton flavor violation (LFV) and (ii)
sizeable non-standard neutrino interactions (NSI). We consider the interplay
between the magnitude of non-unitarity effects in the lepton mixing matrix, and
the constraints that follow from LFV searches in the laboratory. We find that
NSI parameters can be sizeable, up to percent level in some cases, while LFV
rates, such as that for \mu -> e \gamma, lie within current limits, including
the recent one set by the MEG collaboration. As a result the upcoming long
baseline neutrino experiments offer a window of opportunity for complementary
LFV and weak universality tests.Comment: 14 pages, 14 composite figures and 1 table. v2: minor changes,
references added. Accepted for publication in JHE
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