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M. Picariello

Publications and source records attributed to M. Picariello.

27 records · Page 2Linked to original sources
arXiv2002

KamLAND, solar antineutrinos and their magnetic moment

We investigate the possibility of detecting solar antineutrinos with the KamLAND experiment. These antineutrinos are predicted by spin-flavor oscillations at a significant rate even if this mechanism is not the leading solution to the SNP. The recent evidence from SNO shows that a) the neutrino oscillates, only around 34% of the initial solar neutrinos arrive at the Earth as electron neutrinos and b) the conversion is mainly into active neutrinos, however a non e, mu, tau component is allowed: the fraction of oscillation into non-mu-tau neutrinos is found to be cos^2(alpha) = 0.08^{+0.20}_{-0.40}. This residual flux could include sterile neutrinos and/or the antineutrinos of the active flavors. KamLAND is potentially sensitive to antineutrinos derived from solar ^8 B neutrinos. In case of negative results, we find that KamLAND could put strict limits on the flux of solar antineutrinos, Phi(^8 B) < 1.0 times 10^4 cm^{-2} s^{-1}, more than one order of magnitude smaller than existing limits, and on their appearance probability P < 0.20-0.15% (95% CL) after 1-3 years of operation. Assuming a concrete model for antineutrino production by spin-flavor precession, this upper bound implies an upper limit on the product of the intrinsic neutrino magnetic moment and the value of the solar magnetic field mu B < 10^{-21} MeV (95% CL). For B ~ 10-100 kG, we would have mu < 10^{-11}-10^{-12} mu_B (95% CL). In the opposite case, if spin-flavor precession is indeed at work even at a non-leading rate, the additional flux of antineutrinos could strongly distort the signal spectrum seen at KamLAND at energies above 4-5 MeV and their contribution should properly be taken into account.

hep-ph↗
arXiv2002

KamLAND potentiality on the determination of Neutrino mixing parameters in the post SNO-NC era

We study in detail the power of the reactor experiment kamLAND for discriminating existing solutions to the SNP and giving accurate information on neutrino masses and mixing angles. Assuming the expected signal corresponding to various ``benchmark'' points in the 2 dimensional $(Δm^2,\tan^2 θ)$ mixing plane, we develop a full-fledged $χ^2$ analysis which includes KamLAND spectrum and all the existing solar evidence. A complete modelling of statistical and known systematics errors for 1 and 3 years of data taking is also included, exclusion plots are presented. We find a much higher sensitivity especially for values of $Δm^2$ lying in the central part of the LMA region. The situation would be more complicate for values closer to the border of the LMA region (the so called HLMA region, i.e. $Δm^2 \leq 2 \times 10^{5}$ and $Δm^2 \geq 8-9 \times 10^{-5}$ or $tan^2 θ$ far from $\tan^2 θ= 0.5$). In this case kamLAND, with or without solar evidence, will be able only to select multiple regions in the parameter space, in the sense that different possible values of the parameters would produce the same signal.

hep-ph↗
arXiv2002

The solar neutrino puzzle: present situation and future scenarios

We present a short review of the existing evidence in favor of neutrino mass and neutrino oscillations which come from different kinds of experiments. We focus our attention in particular on solar neutrinos, presenting a global updated phenomenological analysis of all the available data and we comment on different possible future scenarios.

hep-ph↗
arXiv2002

Determination of Neutrino mixing parameters after SNO oscillation evidence

An updated analysis of all available neutrino oscillation evidence in Solar experiments (SK day and night spectra, global rates from Homestake, SAGE and GALLEX) including the latest SNO CC and NC data is presented. Assuming that the shape of the SNO CC energy spectrum is undistorted and using the information provided by SNO we obtain, for the fraction of electron neutrinos remaining in the solar beam at energies $\gsim 5$ MeV: $ϕ_{CC}/ϕ_{NC}=0.34^{+0.05}_{-0.04},$ which is nominally $\sim 30σ$ away from the standard value. The fraction of oscillating neutrinos which into active ones is computed to be: $ (Φ_{NC}-Φ_{CC})/(Φ_{SSM}-Φ_{CC})=0.92^{+0.39}_{-0.20} $ nearly $5σ$ deviations from the pure sterile oscillation case. The data is still compatible with an important fraction of sterile component in the solar beam (up to 20% of the total). In the framework of two active neutrino oscillations we determine individual neutrino mixing parameters and their errors in the region of no spectrum distortion ($Δ< T_e> <1%$), we obtain $Δm^2= 4.5^{+2.7}_{-1.4}\times 10^{-5} \eV^2, \quad \tan^2θ=0.40^{+0.10}_{-0.08}. $ This is in agreement with the best $chi^2$ solution in the LMA region.

hep-ph↗
arXiv2002

Solving the solar neutrino problem with kamLAND and BOREXINO

We analyze the expected signals of two future neutrino experiments, kamLAND and BOREXINO. We show that with just these experiments, we will hopefully be able to determine which of the existing solutions to the solar neutrino problem is the real solution. We also analyze existing solar neutrino data and determine the best-fit points in the oscillation-parameter space finding that with the inclusion of SNO-charged current, the global-rates analysis gives a favored LMA solution with a goodness of fit (g.o.f) of just 32.63%, whereas the g.o.f of the SMA solution is 9.83%. Nonetheless, maximal and quasi-maximal mixing is not favored. If we include the Superkamiokande spectrum in our χ^2 analysis, we obtain a LMA solution with a g.o.f. of 84.38%.

hep-ph↗
arXiv2002

Global analysis of Solar neutrino oscillation evidence including SNO and implications for Borexino

An updated analysis of all available neutrino oscillation evidence in Solar experiments including the latest $SNO$ data is presented. Predictions for total rates and day-night asymmetry in Borexino are calculated. Our analysis features the use of exhaustive computation of the neutrino oscillation probabilities and the use of an improved statistical $χ^2$ minimization. In the framework of two neutrino oscillations we conclude that the best fit to the data is obtained in the LMA region with parameters $(Δm^2, \tan^2θ) = (5.2 \times 10^{-5} \eV^2, 0.47)$, ($χ^2_{min}/n=0.82$, $n=38$ degrees of freedom). Although less favored, solutions in the LOW and VAC regions are still possible with a reasonable statistical significance. The best possible solution in the SMA region gets as maximum a statistical significance as low as $\sim 3%$. We study the implications of these results for the prospects of Borexino and the possibility of discriminating between the different solutions. The expected normalized Borexino signal is 0.62 at the best fit LMA solution while the DN asymmetry is negligible (approximately $10^{-5}$). In the LOW region the signal is in the range $\sim 0.6-0.7$ at 90% confidence level while the asymmetry is $\simeq 1-20%$. As a consequence, the combined Borexino measurements of the total event rate with a error below $\pm 5-10%$ and day-night total rate asymmetry with a precision comparable to the one of SuperKamiokande, will have a strong chance of distinguishing or at least strongly favoring one of the Solar neutrino solutions provided by present data.

hep-ph↗
arXiv2001

Solar neutrino experiments and Borexino perspectives

We present an updated analysis of all the data available about solar neutrinos, including the charged current SNO results. The best fit of the data is obtained in the Large Mixing Angle region, but different solutions are still possible. We also study the perspectives of Borexino and conclude that this experiment, with a parallel analysis of total rate and day-night asymmmetry, should be able to discriminate between the different possible solutions.

hep-ph↗
arXiv2001

Algebraic Aspects of the Background Field Method

We discuss some algebraic properties of the background field method. We introduce an extra gauge-fixing term for the background gauge field right at the beginning in the action in such a way that BRST invariance is preserved. The background effective action is considered and it is shown to satisfy both the Slavnov-Taylor identities and the Ward identities. This allows to prove the background equivalence theorem by means of the standard techniques. We show that the Legendre transform W_{bg} of the background gauge invariant action gives the same physical amplitudes as the original one we started with. Moreover, we point out that W_{bg} cannot in general be derived from a classical action by the Gell-Mann-Low formula. Finally, we show that the BRST doublet generated from the background field does not modify the anomaly of the original underlying gauge theory. The proof is algebraic and makes no use of arguments based on power-counting.

hep-th↗