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P. I. Krastev

Publications and source records attributed to P. I. Krastev.

27 records · Page 2Linked to original sources
arXiv1995

What Can Be Learned with an Iodine Solar-Neutrino Detector?

We study the potential benefits of an iodine-based solar-neutrino detector for testing hypotheses that involve neutrino oscillations. We argue that such a detector will have a good chance of distinguishing the two allowed regions of $Δm^2$ -- $\sin^22θ$ parameter space if neutrino conversion is occurring in the sun. It should also be able to detect seasonal variations in the signal due to vacuum oscillations and might be sensitive enough to detect day/night variations due to MSW transitions in the earth. Although it would need to be calibrated, a working iodine detector could be completed before more ambitious projects that seek to accomplish the same things.

hep-ph↗
arXiv1994

Limits on Electron-Neutrino Oscillations from the GALLEX $^{51}$Cr Source Experiment

The recent result from the chromium source experiment carried out by the GALLEX collaboration implies interesting limits on the parameters $Δm^2$ and $\sin^22θ$ describing neutrino oscillations. Values of $Δm^2~>~0.17$ eV$^2$ for maximal mixing and of $\sin^22θ> 0.38$ for $Δm^2 > 1$~eV$^2$ are ruled out at 90\% C.L. This result improves by more than an order of magnitude previous limits on $Δm^2$ derived from electron-neutrino oscillation experiments at accelerators.

hep-ph↗
arXiv1994

Spectral Analysis of Neutrino Mixing Mechanisms

The prospects of using spectral measurements of solar neutrinos to distinguish different mechanisms of neutrino flavor mixing are analyzed. The mechanisms studied include the conventional mass mixing mechanism and an alternative mechanism which assumes a flavor nondiagonal neutrino-gravity coupling.

hep-ph↗
arXiv1994

Solar Neutrinos and the Principle of Equivalence

We study the proposed solution of the solar neutrino problem which requires a flavor nondiagonal coupling of neutrinos to gravity. We adopt a phenomenological point of view and investigate the consequences of the hypothesis that the neutrino weak interaction eigenstates are linear combinations of the gravitational eigenstates which have slightly different couplings to gravity, $f_1G$ and $f_2G$, $|f_1-f_2| << 1$, corresponding to a difference in red-shift between electron and muon neutrinos, $Δz/(1+z) \sim |f_1 - f_2|$. We perform a $χ^2$ analysis of the latest available solar neutrino data and obtain the allowed regions in the space of the relevant parameters. The existing data rule out most of the parameter space which can be probed in solar neutrino experiments, allowing only $|f_1 - f_2| \sim 3 \times 10^{-14}$ for small values of the mixing angle ($2 \times 10^{-3} \le \sin^2(2θ_G) \le 10^{-2}$) and $10^{-16} \stackrel{<}{\sim} |f_1 - f_2| \stackrel{<}{\sim}10^{-15}$ for large mixing ($0.6 \le \sin^2(2θ_G) \le 0.9$). Measurements of the $^8{\rm B}$-neutrino energy spectrum in the SNO and Super-Kamiokande experiments will provide stronger constraints independent of all considerations related to solar models. We show that these measurements will be able to exclude part of the allowed region as well as to distinguish between conventional oscillations and oscillations due to the violation of the equivalence principle.

hep-ph↗
arXiv1994

Testing the Vacuum Oscillation and the MSW Solutions of the Solar Neutrino Problem

Solar model independent tests of the vacuum oscillation and MSW solutions of the solar neutrino problem are considered. Detailed predictions for time (seasonal) variations of the signals in the future solar neutrino detectors (SNO, Super Kamiokande, BOREXINO, HELLAZ), if solar neutrinos take part in vacuum oscillations, are given. Results on the distortions of the spectra of boron neutrinos, and of electrons from the neutrino-electron scattering induced by boron neutrinos, in the cases of vacuum oscillations or MSW transitions are presented for a large number of values of the relevant parameters. The possibilities to distinguish between the vacuum oscillation, the MSW adiabatic, and the MSW nonadiabatic transitions (solutions) in the future solar neutrino experiments are discussed.

hep-ph↗
arXiv1994

Boron neutrino flux and the MSW solution of the solar neutrino problem

There are large uncertainties in the predictions of the boron neutrino flux from the Sun which cannot be considered as being of purely statistical origin. We treat the magnitude of this flux, $Φ_B$, as a parameter to be found from experiment. The properties of the MSW solution to the solar neutrino problem for different values of $Φ_B$ are studied. Present data give the bounds: $0.38 < Φ_B/ Φ_B^0 < 3.1$ (2$σ$), where $Φ_B^0 \equiv 5.7 \cdot 10^6$ cm$^{-2}$s$^{-1}$ is the flux in the reference SSM. The variations of the flux in this interval enlarge the allowed region of mixing angles: $\sin^2 2θ= 8\cdot 10^{-4} ÷2\cdot 10^{-2}$ (small mixing solutions) and $\sin^2 2θ= 0.2 ÷0.85$ (large mixing solution). If the value of the original boron neutrino flux is about that measured by Kamiokande, a consistent description of the data is achieved for $\sin^2 2θ\sim (0.8 ÷2)\cdot 10^{-3}$ (``very small mixing solution"). The solution is characterized by a strong suppression of the beryllium neutrino line, a weak distortion of the high energy part of the boron neutrino spectrum and a value of the double ratio $(CC/NC)^{exp}/(CC/NC)^{SSM}$ at $E > 5$ MeV close to 1. We comment on the possibility to measure the neutrino parameters and the original boron neutrino flux in future experiments.

hep-ph↗
arXiv1994

New Constraints on Neutrino Oscillations in Vacuum as a Possible Solution of the Solar Neutrino Problem

Two-neutrino oscillations in vacuum are studied as a possible solution of the solar neutrino problem. New constraints on the parameter sn2, characterizing the mixing of the electron neutrino with another active or sterile neutrino, as well as on the mass--squared difference, dm2, of their massive neutrino components, are derived using the latest results from the four solar neutrino experiments. Oscillations into a sterile neutrino are ruled out at 99 % C.L. by the observed mean event rates even if one includes the uncertainties of the standard solar model predictions in the analysis.

hep-ph↗
arXiv1992

Time Variations of Solar Neutrino Signals and the RSFCN Hypothesis

Resonant spin--flavour conversion of neutrinos (RSFCN) in twisting magnetic fields might be at the origin of the apparent anticorrelation between the $^{37}$Ar production--rate in the Homestake solar neutrino detector and the solar activity. Moreover, it can account for the results of all solar neutrino experiments reported so far including the recent results of GALLEX and SAGE.

hep-ph↗