25 research outputs found
Probing neutrino nature at Borexino detector with chromium neutrino source
In this paper, we indicate a possibility of utilizing the intense chromium
source () in probing the neutrino nature in low energy neutrino
experiments with the ultra-low threshold and background real-time Borexino
detector located near the source (). We analyze the elastic
scattering of electron neutrinos (Dirac or Majorana, respectively) on the
unpolarized electrons in the relativistic neutrino limit. We assume that the
incoming neutrino beam is the superposition of left-right chiral states. Left
chiral neutrinos may be detected by the standard and non-standard scalar
, tensor interactions, while right chiral ones partake only in the
exotic and interactions. Our model-independent study is
carried out for the flavour (current) neutrino eigenstates. We compute the
expected event number for the standard interaction of the left chiral
neutrinos using the current experimental values of standard couplings and in
the case of left-right chiral superposition. We show that the significant
decrement in the event number due to the interference terms between the
standard and exotic interactions for the Majorana 's may appear. The C. L. sensitivity contours in the planes of corresponding exotic couplings
are also found. The presence of interferences in the Majorana case gives the
stronger constraints than for the Dirac neutrinos, even if the neutrino source
is placed outside the detector.Comment: 8 pages, 7 eps figure
Neutrino elastic scattering on polarized electrons as a tool for probing the neutrino nature
Possibility of using the polarized electron target (PET) for testing the
neutrino nature is considered. One assumes that the incoming electron neutrino
() beam is the superposition of left chiral states with right chiral
ones. Consequently the non-vanishing transversal components of spin
polarization may appear, both T-even and T-odd. s are produced by the
low energy monochromatic (un)polarized emitter located at a near distance from
the hypothetical detector which is able to measure both the azimuthal angle and
polar angle of the recoil electrons, and/or also the energy of the outgoing
electrons with a high resolution. A detection process is the elastic scattering
of s (Dirac or Majorana) on the polarized electrons. Left chiral (LC)
s interact mainly by the standard interaction, while right
chiral (RC) ones participate only in the non-standard , scalar ,
pseudoscalar and tensor interactions. All the interactions are of
flavour-conserving type (FC). We show that a distinction between the Dirac and
the Majorana s is possible both for the longitudinal and the
transversal polarizations. In the first case a departure from the
standard prediction of the azimuthal asymmetry of recoil electrons is caused by
the interferences between the non-standard complex S and T couplings. Such a
deviation would indicate the Dirac nature and the presence of time
reversal symmetry violation (TRSV) interactions. In the second case the
azimuthal asymmetries, polar distribution and energy spectrum of scattered
electrons are sensitive to the interference terms between the standard and
exotic interactions, proportional to the various angular correlations. Our
model-independent study is carried out for the flavour eigenstates in
the relativistic limit.Comment: 10 pages, 10 figures, published versio
Mock LISA data challenge for the galactic white dwarf binaries
We present data analysis methods used in detection and the estimation of parameters of gravitational wave signals from the white dwarf binaries in the mock LISA data challenge. Our main focus is on the analysis of challenge 3.1, where the gravitational wave signals from more than 50 mln. Galactic binaries were added to the simulated Gaussian instrumental noise. Majority of the signals at low frequencies are not resolved individually. The confusion between the signals is strongly reduced at frequencies above 5 mHz. Our basic data analysis procedure is the maximum likelihood detection method. We filter the data through the template bank at the first step of the search, then we refine parameters using the Nelder-Mead algorithm, we remove the strongest signal found and we repeat the procedure. We detect reliably and estimate parameters accurately of more than ten thousand signals from white dwarf binaries
Detecting white dwarf binaries in Mock LISA Data Challenge 3
We present a strategy for detecting gravitational wave signals from the Galactic white dwarf binaries in the Mock LISA Data Challenge 3 (MLDC3) and estimate their parameters. Our method is based on the matched filtering in the form of the {\mathcal F} -statistic. We perform the search on three-dimensional space (sky coordinate and frequency of gravitational wave) below 3 mHz and include the fourth parameter (frequency derivative) at high frequencies. A template bank is used to search for the strongest signal in the data, then we remove it and repeat the search until we do not have signals in the data above a preselected threshold. For the template bank, we construct an optimal grid that realizes the best lattice covering with a constraint such that the nodes of the grid coincide with the Fourier frequencies. This enables the use of the fast Fourier transform algorithm to calculate the {\mathcal F} -statistic
Searching for Galactic White Dwarf Binaries in Mock LISA Data using an F-Statistic Template Bank
We describe an F-statistic search for continuous gravitational waves from
galactic white-dwarf binaries in simulated LISA Data. Our search method employs
a hierarchical template-grid based exploration of the parameter space. In the
first stage, candidate sources are identified in searches using different
simulated laser signal combinations (known as TDI variables). Since each source
generates a primary maximum near its true "Doppler parameters" (intrinsic
frequency and sky position) as well as numerous secondary maxima of the
F-statistic in Doppler parameter space, a search for multiple sources needs to
distinguish between true signals and secondary maxima associated with other,
"louder" signals. Our method does this by applying a coincidence test to reject
candidates which are not found at nearby parameter space positions in searches
using each of the three TDI variables. For signals surviving the coincidence
test, we perform a fully coherent search over a refined parameter grid to
provide an accurate parameter estimation for the final candidates. Suitably
tuned, the pipeline is able to extract 1989 true signals with only 5 false
alarms. The use of the rigid adiabatic approximation allows recovery of signal
parameters with errors comparable to statistical expectations, although there
is still some systematic excess with respect to statistical errors expected
from Gaussian noise. An experimental iterative pipeline with seven rounds of
signal subtraction and re-analysis of the residuals allows us to increase the
number of signals recovered to a total of 3419 with 29 false alarms.Comment: 29 pages, 11 figures; submitted to Classical and Quantum Gravit
Solutions of Quantum Gravity Coupled to the Scalar Field
We consider the Wheeler-De Witt equation for canonical quantum gravity
coupled to massless scalar field. After regularizing and renormalizing this
equation, we find a one-parameter class of its solutions.Comment: 8 pages, LaTe
Kappa - Poincare dispersion relations and the black hole radiation
Following the methods developed by Corley and Jacobson, we consider
qualitatively the issue of Hawking radiation in the case when the dispersion
relation is dictated by quantum kappa-Poincare algebra. This relation
corresponds to field equations that are non-local in time, and, depending on
the sign of the parameter kappa, to sub- or superluminal signal propagation. We
also derive the conserved inner product, that can be used to count modes, and
therefore to obtain the spectrum of black hole radiation in this case.Comment: 11 pages, 2 figure
The Mock LISA Data Challenges: from Challenge 3 to Challenge 4
The Mock LISA Data Challenges are a program to demonstrate LISA data-analysis
capabilities and to encourage their development. Each round of challenges
consists of one or more datasets containing simulated instrument noise and
gravitational waves from sources of undisclosed parameters. Participants
analyze the datasets and report best-fit solutions for the source parameters.
Here we present the results of the third challenge, issued in Apr 2008, which
demonstrated the positive recovery of signals from chirping Galactic binaries,
from spinning supermassive--black-hole binaries (with optimal SNRs between ~ 10
and 2000), from simultaneous extreme-mass-ratio inspirals (SNRs of 10-50), from
cosmic-string-cusp bursts (SNRs of 10-100), and from a relatively loud
isotropic background with Omega_gw(f) ~ 10^-11, slightly below the LISA
instrument noise.Comment: 12 pages, 2 figures, proceedings of the 8th Edoardo Amaldi Conference
on Gravitational Waves, New York, June 21-26, 200
The Mock LISA Data Challenges: from Challenge 1B to Challenge 3
The Mock LISA Data Challenges are a programme to demonstrate and encourage
the development of LISA data-analysis capabilities, tools and techniques. At
the time of this workshop, three rounds of challenges had been completed, and
the next was about to start. In this article we provide a critical analysis of
entries to the latest completed round, Challenge 1B. The entries confirm the
consolidation of a range of data-analysis techniques for Galactic and
massive--black-hole binaries, and they include the first convincing examples of
detection and parameter estimation of extreme--mass-ratio inspiral sources. In
this article we also introduce the next round, Challenge 3. Its data sets
feature more realistic waveform models (e.g., Galactic binaries may now chirp,
and massive--black-hole binaries may precess due to spin interactions), as well
as new source classes (bursts from cosmic strings, isotropic stochastic
backgrounds) and more complicated nonsymmetric instrument noise.Comment: 20 pages, 3 EPS figures. Proceedings of the 12th Gravitational Wave
Data Analysis Workshop, Cambridge MA, 13--16 December 2007. Typos correcte