arXiv subjects

J. Pulido

Publications and source records attributed to J. Pulido.

8 recordsLinked to original sources

arXiv2009

Neutrino Dipole Moments and Solar Experiments

First we investigate the possibility of detecting solar antineutrinos with the KamLAND experiment. Then we analyze the first Borexino data release to constrain the neutrino magnetic moment. Finally we investigate the resonant spin flavour conversion of solar neutrinos to sterile ones, a mechanism which is added to the well known LMA one. In this last condition, we show that the data from all solar neutrino experiments except Borexino exhibit a clear preference for a sizable magnetic field. We argue that the solar neutrino experiments are capable of tracing the possible modulation of the solar magnetic field. In this way Borexino alone may play an essential role although experimental redundancy from other experiments will be most important.

hep-ph↗

arXiv2008

Probing neutrino magnetic moment and unparticle interactions with Borexino

We discuss the limits on the neutrino magnetic moment and hypothetical interactions with a hidden unparticle sector, coming from the first neutrino data release of the Borexino experiment. The observed spectrum in Borexino depends weakly on the solar model used in the analysis, since most of the signal comes from the mono-energetic 7Be neutrinos. This fact allows us to calibrate the nu-e scattering cross section through the spectral shape. In this way, we have derived a limit on the magnetic moment for the neutrinos coming from the Sun (in which a nu_mu and nu_tau component is present): mu_nu<8.4E-11 mu_B (90%CL) which is comparable with those obtained from low energy reactor experiments. Moreover, we improve the previous upper limit on magnetic moment of the nu_tau by three orders of magnitude and the limit on the coupling constant of the neutrino with a hidden unparticle sector.

hep-ph↗

arXiv2004

SNO, SuperKamiokande data, antineutrinos and sterile neutrinos

Allowing for antineutrinos ($\barν_x$) and sterile neutrinos ($ν_s$) to accompany LMA oscillations, we derive in a model independent way, upper bounds on their components in the solar flux, using the recent data from SNO and SuperKamiokande. Along with the general case (LMA + $\barν_x$ + $ν_s$) we consider the special cases where only $\barν_x$ or $ν_s$ are present. We obtain an upper bound on $\barν_x$ which is independent of the $ν_s$ component. In the no sterile case we obtain upper and lower bounds on $f_B$, the SSM normalization factor. We also investigate in the general case the common parameter range for $f_B$ and the $\barν_x$, $ν_s$ components and find that the upper bound on $ν_s$ is hardly sensitive to the $\barν_x$ component. In the absence of $\barν_x$ we recover the $ν_s$ upper bound existing in the literature. We finally present a simple $χ^2$ analysis of all four cases considered.

hep-ph↗

arXiv2003

Neutrino transition magnetic moments and the solar magnetic field on the light of the Kamland evidence

We present here a recopilation of recent results about the possibility of detecting solar electron antineutrinos produced by solar core and convective magnetic fields. These antineutrinos are predicted by spin-flavor oscillations at a significant rate even if this mechanism is not the leading solution to the SNP. Using the recent Kamland results and assuming a concrete model for antineutrino production by spin-flavor precession in the convective zone based on chaotic magnetic fields,we obtain bounds on the flux of solar antineutrinos, on the average conversion neutrino-antineutrino probability and on intrinsic neutrino magnetic moment. In the most conservative case, $μ\lsim 2.5\times 10^{-11} μ_B$ (95% CL). When studying the effects of a core magnetic field, we find in the weak limit a scaling of the antineutrino probability with respect to the magnetic field profile in the sense that the same probability function can be reproduced by any profile with a suitable peak field value. In this way the solar electron antineutrino spectrum can be unambiguosly predicted. We use this scaling and the negative results indicated by the KamLAND experiment to obtain upper bounds on the solar electron antineutrino flux. We find that, for a wide family of magnetic field profiles in the sun interior, the antineutrino appearance probability is largely determined by the magnetic field intensity but not by its shape. Explicit limits on neutrino transition moments are also obtained consistent with the convective case. These limits are therefore largerly independent of the detailed structure of the magnetic field in the solar interior.

hep-ph↗

arXiv2002

Solar neutrino oscillations and bounds on neutrino magnetic moment and solar magnetic field

If the observed deficit of solar neutrinos is due to neutrino oscillations, neutrino conversions caused by the interaction of their transition magnetic moments with the solar magnetic field (spin-flavour precession) can still be present at a subdominant level. In that case, the combined action of neutrino oscillations and spin-flavour precession can lead to a small but observable flux of electron antineutrinos coming from the sun. Non-observation of these nuebar's could set limits on neutrino transition moment μand the strength and coordinate dependence of the solar magnetic field B_\perp. The sensitivity of the nuebar flux to the product μB_\perp is strongest in the case of the vacuum oscillation (VO) solution of the solar neutrino problem; in the case of the LOW solution, it is weaker, and it is the weakest for the LMA solution. For different solutions, different characteristics of the solar magnetic field B_\perp(r) are probed: for the VO solution, the nuebar flux is determined by the integral of B_\perp(r) over the solar convective zone, for LMA it is determined by the magnitude of B_\perp in the neutrino production region, and for LOW it depends on the competition between this magnitude and the derivative of B_\perp(r) at the surface of the sun.

hep-ph↗

arXiv2002

Distinguishing magnetic moment from oscillation solutions of the solar neutrino problem with Borexino

Assuming that the observed deficit of solar neutrinos is due to the interaction of their transition magnetic moment with the solar magnetic field we derive the predictions for the forthcoming Borexino experiment. Three different model magnetic field profiles which give very good global fits of the currently available solar neutrino data are used. The expected signal at Borexino is significantly lower than those predicted by the LMA, LOW and VO neutrino oscillation solutions of the solar neutrino problem. It is similar to that of the SMA oscillation solution which, however, is strongly disfavoured by the Super-Kamiokande data on day and night spectra and zenith angle distribution of the events. Thus, the neutrino magnetic moment solution of the solar neutrino problem can be unambiguously distinguished from the currently favoured oscillation solutions at Borexino.

hep-ph↗

arXiv2000

SNO and the neutrino magnetic moment solution of the solar neutrino problem

Assuming that the solar neutrino deficit observed in the Homestake, SAGE, Gallex, Kamiokande and Super-Kamiokande experiments is due to the interaction of the neutrino transition magnetic moment with the solar magnetic field, we calculate the expected values of a number of observables to be measured by SNO. For three model solar magnetic field profiles that produce the best fits of the previous data we calculate the charged current event rate, the (neutral current)/(charged current) event ratio and the charged current electron spectrum as well as its first and second moments. We study the dependence of the calculated observables on the choice of the magnetic field profile and on the value of the solar $hep$ neutrino flux. We also compare our results with those obtained assuming that the solar neutrino problem is due to neutrino oscillations in vacuum or in matter. We show that there is an overlap or partial overlap between our predictions and those found for each of the oscillation solutions (SMA, LMA, LOW and VO). Given the uncertainties in the calculations and the expected uncertainties in the experimental results, the unambiguous discrimination between the two types of solutions to the solar neutrino problem (neutrino oscillations and magnetic moments) on the basis of the average rates and electron spectrum distortions appears to be difficult. The possible time dependence of the charged current signal and spectrum distortion in the case of the magnetic moment solution therefore remains the best hope for such a discrimination. For a hybrid solution (neutrino magnetic moment plus flavour mixing) the smoking gun signature would be an observation of $\barν_e$'s from the sun.

hep-ph↗

arXiv1999

Resonance spin flavour precession and solar neutrinos

We examine the prospects for the resonance spin flavour precession as a solution to the solar neutrino problem. We study seven different realistic solar magnetic field profiles and, by numerically integrating the evolution equations, perform a fit of the event rates for the three types of solar neutrino experiments (Ga, Cl and SuperKamiokande) and a fit of the energy spectrum of the recoil electrons in SuperKamiokande. A $χ^2$ analysis shows that the quality of the rate fits is excellent for two of the field profiles and good for all others with $χ^2 /d.o.f.$ always well below unity. Regarding the fits for the energy spectrum, their quality is better than that for the small mixing angle MSW solution of the solar neutrino problem, at the same level as that for the large mixing angle MSW solution but worse than that for the vacuum oscillations one. The experimental data on the spectrum are however largely uncertain especially in the high energy sector, so that it is too early yet to draw any clear conclusions on the likeliest type of particle physics solution to the solar neutrino problem.

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