Search results for "Oscillations"
showing 10 items of 238 documents
Performance of long modules of silicon microstrip detectors
1998
This note describes the performance of modules assembled with up to twelve silicon microstrip detectors. These modules were built for the instrumented Silicon Target (STAR) that has been installed in the NOMAD spectrometer. Laboratory and test beam results are compared with model predictions. For a module of nine detectors, test beam results indicate a signal--to--noise ratio of 19, a hit finding efficiency of 99.8\% and a spatial resolution of 6.0 $\mu$m. Laboratory measurements indicate that modules of twelve detectors exhibit a signal--to--noise ratio of the order of 16.
Unveiling ν secrets with cosmological data: Neutrino masses and mass hierarchy
2017
Using some of the latest cosmological datasets publicly available, we derive the strongest bounds in the literature on the sum of the three active neutrino masses, $M_\nu$, within the assumption of a background flat $\Lambda$CDM cosmology. In the most conservative scheme, combining Planck cosmic microwave background (CMB) temperature anisotropies and baryon acoustic oscillations (BAO) data, as well as the up-to-date constraint on the optical depth to reionization ($\tau$), the tightest $95\%$ confidence level (C.L.) upper bound we find is $M_\nu0.06\,{\rm eV}$ from oscillations data would raise the quoted upper bounds by ${\cal O}(0.1\sigma)$ and would not affect our conclusions.
Non-standard interactions: Atmospheric versus neutrino factory experiments
2001
We consider the potential of a generic neutrino factory (NUFACT) in probing non-standard neutrino-matter interactions (NSI). We find that the sensitivity to flavour-changing (FC) NSI can be substantially improved with respect to present atmospheric neutrino data, especially at energies higher than approximately 50 GeV, where the effect of the tau mass is small. For example, a 100 GeV NUFACT can probe FC neutrino interactions at the level of few $|\epsilon| < {few} \times 10^{-4}$ at 99 % C.L.
Ultralight dark photon as a model for early universe dark matter
2019
Dark photon is a massive vector field which interacts only with the physical photon through the kinetic mixing. This coupling is assumed to be weak so that the dark photon becomes almost unobservable in processes with elementary particles, but can serve as a dark matter particle. We argue that in very early Universe ($z>3000$) this vector field may have the equation of state of radiation ($w=1/3$) but later behaves as cold dark matter ($w=0$). This may slightly change the expansion rate of the Universe at early time and reduce the value of the sound horizon of baryon acoustic oscillations (standard ruler). As a result, in this model the value of the Hubble constant appears to be larger than…
Constraints on electromagnetic form factors of sub-GeV dark matter from the cosmic microwave background anisotropy
2021
We consider dark matter which have non-zero electromagnetic form factors like electric/magnetic dipole moments and anapole moment for fermionic dark matter and Rayleigh form factor for scalar dark matter. We consider dark matter mass $m_\chi > \cal{ O}({\rm MeV})$ and put constraints on their mass and electromagnetic couplings from CMB and LSS observations. Fermionic dark matter with non-zero electromagnetic form factors can annihilate to $e^+ e^-$ and scalar dark matter can annihilate to $2\gamma$ at the time of recombination and distort the CMB. We analyze dark matter with multipole moments with Planck and BAO observations. We find upper bounds on anapole moment $g_{A}<7.163\times 10^{3} …
A non-resonant dark-side solution to the solar neutrino problem
2001
We re-analyse spin-flavour precession solutions to the solar neutrino problem in the light of the recent SNO CC result as well as the 1258--day Super-Kamiokande data and the upper limit on solar anti-neutrinos. In a self-consistent magneto-hydrodynamics approach the resulting scheme has only 3 effective parameters: $\Delta m^2$, $\mu B_\perp$ and the neutrino mixing angle $\theta$. We show how a rates-only analysis for fixed $\mu B_\perp$ slightly favours spin-flavour precession (SFP) solutions over oscillations (OSC). In addition to the resonant solution (RSFP for short), there is a new non-resonant solution (NRSFP) in the ``dark-side''. Both RSFP and NRSFP lead to flat recoil energy spect…
Determination of the θ23 octant in long baseline neutrino experiments within and beyond the standard model
2018
The recent data indicate that the neutrino mixing angle $\theta_{23}$ deviates from the maximal-mixing value of 45$^\circ$, showing two nearly degenerate solutions, one in the lower octant (LO) ($\theta_{23}45^\circ$). We investigate, using numerical simulations, the prospects for determining the octant of $\theta_{23}$ in the future long baseline oscillation experiments. We present our results as contour plots on the ($\theta_{23}-45^\circ$, $\delta$)--plane, where $\delta$ is the $CP$ phase, showing the true values of $\theta_{23}$ for which the octant can be experimentally determined at 3$\,\sigma$, 2$\,\sigma$ and 1$\,\sigma$ confidence level. In particular, we study the impact of the p…
Analysis of oscillations in discontinuous Lurie systems via LPRS method
2019
We discuss advantages and limitations of the harmonic balance method and the locus of a perturbed relay system (LPRS) method in the problem of finding periodic oscillations. In this paper we present the results of using harmonic balance method and LPRS method while investigating a 3rd order dynamic system in Lurie form. In this system a symmetric periodic oscillation is found, while other two asymmetric periodic motions are not found using both methods.
Acoustic Wave Properties in Footpoints of Coronal Loops in 3D MHD Simulations
2021
Acoustic waves excited in the photosphere and below might play an integral part in the heating of the solar chromosphere and corona. However, it is yet not fully clear how much of the initially acoustic wave flux reaches the corona and in what form. We investigate the wave propagation, damping, transmission, and conversion in the lower layers of the solar atmosphere using 3D numerical MHD simulations. A model of a gravitationally stratified expanding straight coronal loop, stretching from photosphere to photosphere, is perturbed at one footpoint by an acoustic driver with a period of 370 seconds. For this period acoustic cutoff regions are present below the transition region (TR). About 2% …
A dynamical dark energy model with a given luminosity distance
2011
It is assumed that the current cosmic acceleration is driven by a scalar field, the Lagrangian of which is a function of the kinetic term only, and that the luminosity distance is a given function of the red-shift. Upon comparison with Baryon Acoustic Oscillations (BAOs) and Cosmic Microwave Background (CMB) data the parameters of the models are determined, and then the time evolution of the scalar field is determined by the dynamics using the cosmological equations. We find that the solution is very different than the corresponding solution when the non-relativistic matter is ignored, and that the universe enters the acceleration era at larger red-shift compared to the standard $\Lambda CD…