arXiv subjects

E. Torrente-Lujan

Publications and source records attributed to E. Torrente-Lujan.

At least 37 records · Page 2Linked to original sources

arXiv2004

The Classification of the Simply Laced Berger Graphs from Calabi-Yau $CY_3$ spaces

The algebraic approach to the construction of the reflexive polyhedra that yield Calabi-Yau spaces in three or more complex dimensions with K3 fibres reveals graphs that include and generalize the Dynkin diagrams associated with gauge symmetries. In this work we continue to study the structure of graphs obtained from $CY_3$ reflexive polyhedra. The objective is to describe the ``simply laced'' cases, those graphs obtained from three dimensional spaces with K3 fibers which lead to symmetric matrices. We study both the affine and, derived from them, non-affine cases. We present root and weight structurea for them. We study in particular those graphs leading to generalizations of the exceptional simply laced cases $E_{6,7,8}$ and $E_{6,7,8}^{(1)}$. We show how these integral matrices can be assigned: they may be obtained by relaxing the restrictions on the individual entries of the generalized Cartan matrices associated with the Dynkin diagrams that characterize Cartan-Lie and affine Kac-Moody algebras. These graphs keep, however, the affine structure present in Kac-Moody Dynkin diagrams. We conjecture that these generalized simply laced graphs and associated link matrices may characterize generalizations of Cartan-Lie and affine Kac-Moody algebras.

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arXiv2004

Analysis of Neutrino oscillation data with the recent KamLAND results

We present an updated analysis of all available solar and reactor neutrino data, emphasizing in particular the totality of the KamLAND results and including the SNO phase III spectrum data. In a two active-neutrino framework, we determine the solutions in the $Δm_{\odot}^2, \tan^2θ_{\odot}$ parameter space compatible with experimental data. Combining all data, we obtain the following best-fit parameters: $Δm_{\odot}^2 =8.17*10^-5$, $\tan^2θ_{\odot}=0.40$

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arXiv2004

Root systems from Toric Calabi-Yau Geometry. Towards new algebraic structures and symmetries in physics?

The algebraic approach to the construction of the reflexive polyhedra that yield Calabi-Yau spaces in three or more complex dimensions with K3 fibres reveals graphs that include and generalize the Dynkin diagrams associated with gauge symmetries. In this work we continue to study the structure of graphs obtained from $CY_3$ reflexive polyhedra. We show how some particularly defined integral matrices can be assigned to these diagrams. This family of matrices and its associated graphs may be obtained by relaxing the restrictions on the individual entries of the generalized Cartan matrices associated with the Dynkin diagrams that characterize Cartan-Lie and affine Kac-Moody algebras. These graphs keep however the affine structure, as it was in Kac-Moody Dynkin diagrams. We presented a possible root structure for some simple cases. We conjecture that these generalized graphs and associated link matrices may characterize generalizations of these algebras.

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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.

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arXiv2003

The Neutrino mass matrix after Kamland and SNO salt enhanced results

An updated analysis of all available neutrino oscillation evidence in Solar experiments including the latest SNO ES,CC and NC data (254d live time, NaCL enhanced efficiency) is presented. We obtain, for the fraction of active oscillating neutrinos: sin^2alpha=(Φ_{NC}-Φ_{CC})/(Φ_{SSM}-Φ_{CC})=0.94^{+0.0.065}_{-0.060} nearly 20σfrom the pure sterile oscillation case. The fraction of oscillating sterile neutrinos cos^2α\lsim 0.12 (1 sigma CL). At face value, these results might slightly favour the existence of a small sterile oscillating sector. In the framework of two active neutrino oscillations we determine individual neutrino mixing parameters and their errors we obtain Delta m^2= 7.01\pm 0.08 \times 10^{-5} eV^2, tan^2 theta=0.42^{+0.12}_{-0.07}. The main difference with previous analysis is a better resolution in parameter space. In particular the secondary region at larger mass differences (LMAII) is now excluded at 95% CL. The combined analysis of solar and Kamland data concludes that maximal mixing is not favoured at 4-5 sigma. This is not supported by the antineutrino reactor results alone. We estimate the individual elements of the two neutrino mass matrix, writing M^2=m^2 I+M_0^2, we obtain (1 sigma errors): M_0^2=10^{-5} eV^2\pmatrix{ 2.06^{+0.29}_{-0.31} & 3.15^{+0.29}_{-0.35} \cr 3.15^{+0.29}_{-0.35} & 4.60^{+0.56}_{-0.44} }.

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arXiv2003

KamLAND and Solar Antineutrino Spectrum

We use the recent KamLAND observations to predict the solar antineutrino spectrum at some confidence limits. We find that 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-- can be utilised to obtain a general shape of the solar antineutrino spectrum. This scaling and the upper bound on the solar antineutrino event rate, that can be derived from the data, lead to: 1) an upper bound on the solar antineutrino flux, 2) the prediction of their energy spectrum, as the normalisation of the spectrum can be obtained from the total number of antineutrino events recorded in the experiment. We get $ϕ_{\barν}<3.8\times 10^{-3}ϕ(^8B)$ or $ϕ_{\barν} <5.5\times 10^{-3}ϕ(^8B)$ at 95% CL, assuming Gaussian or Poissonian statistics, respectively. And for 90% CL these become $ϕ_{\barν}<3.4 \times 10^{-3}ϕ(^8B)$ and $ϕ_{\barν}<4.9\times 10^{-3}ϕ(^8B)$. It shows an improvement by a factor of 3-5 with respect to existing bounds. These limits are quite general and independent of the detailed structure of the magnetic field in the solar interior.

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arXiv2003

Neutrino mass parameters from Kamland, SNO and other solar evidence

An updated analysis of all available neutrino oscillation evidence in Reactor (Kamland, first 145 days of data) and Solar experiments (SK day and night spectra, global rates from Homestake, SAGE and GALLEX) including the $SNO CC$ and $NC$ data is presented. In the framework of two active neutrino oscillations we determine the allowed regions in neutrino parameter space, we obtain, from the Kamland spectral shape and global signal, the following antineutrino best solution parameters, $ Δm^2_{kl}= 7.7\times 10^{-5} \eV^2, \tan^2θ_{kl}= 0.98.$ The overall effect of the measured observed ratio $R\sim 0.6$ is that the LMA region remains the only one which is still favored. Combining Kamland and Solar data and assuming CPT invariance, i.e. the same mass matrix for neutrino and antineutrinos, we obtain the following antineutrino best solution parameters (LMAI solution), $ Δm^2= 7.1\times 10^{-5} \eV^2,\tan^2θ= 0.47.$ A second solution (LMAII) appears for values $ Δm^2= 1.5\times 10^{-4} \eV^2, \tan^2θ= 0.48.$ We determine additionally individual neutrino mixing parameters and their errors from fits to marginal likelihood distributions, the values are compatible with previous results. In both methods, $χ^2$ minimization and marginal likelihood, the combined analysis of solar and Kamland data concludes that maximal mixing is not favored at the $\sim 3σ$ level at least.

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arXiv2003

KamLAND Bounds on Solar Antineutrinos and neutrino transition magnetic moments

We investigate the possibility of detecting solar electron antineutrinos with the KamLAND experiment. These electron antineutrinos are predicted by spin-flavor oscillations at a significant rate even if this mechanism is not the leading solution to the SNP. KamLAND is sensitive to antineutrinos originated from solar ${}^8$B neutrinos. From KamLAND negative results after 145 days of data taking, we obtain model independent limits on the total flux of solar electron antineutrinos $Φ({}^8 B)< 1.1-3.5\times 10^4 cm^{-2}\ s^{-1}$, more than one order of magnitude smaller than existing limits, and on their appearance probability $P<0.15%$ (95% CL). 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 $μB< 2.3\times 10^{-21}$ MeV 95% CL (for LMA $(Δm^2, \tan^2θ)$ values). Limits on neutrino transition moments are also obtained. For realistic values of other astrophysical solar parameters these upper limits would imply that the neutrino magnetic moment is constrained to be, in the most conservative case, $μ\lsim 3.9\times 10^{-12} μ_B$ (95% CL) for a relatively small field $B= 50$ kG. For higher values of the magnetic field we obtain: $μ\lsim 9.0\times 10^{-13} μ_B$ for field $B= 200$ kG and $μ\lsim 2.0\times 10^{-13} μ_B$ for field $B= 1000$ kG at the same statistical significance.

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arXiv2003

KamLAND, solar antineutrinos and the solar magnetic field

In this work the possibility of detecting solar electron antineutrinos produced by a solar core magnetic field from the KamLAND recent observations is investigated. We find 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 get $ϕ_{\barν}<3.8\times 10^{-3}ϕ(^8B)$ at 95% CL. For 90% CL this becomes $ϕ_{\barν}<3.4\times 10^{-3}ϕ(^8B)$, an improvement by a factor of 3-5 with respect to existing bounds. These limits are independent of the detailed structure of the magnetic field in the solar interior. We also derive upper bounds on the peak field value which are uniquely determined for a fixed solar field profile. In the most efficient antineutrino producing case, we get (95% CL) an upper limit on the product of the neutrino magnetic moment by the solar field $μB< 2.8\times 10^{-19}$ MeV or $B_0 \leq 4.9 \times 10^7 G$ for $μ_ν=10^{-12}μ_B$.

hep-ph↗

arXiv2002

After Sno and Before Kamland: Present and Future of Solar and Reactor Neutrino Physics

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 review of some recent analysis of all available neutrino oscillation evidence in Solar experiments including the recent $SNO CC$ and $NC$ data. We present 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.

hep-ph↗

arXiv2002

Neutralino relic density from direct non-equilibrium production and intermediate scales

We review the calculation of the LSP relic density in alternative cosmological scenarios where contributions from direct decay production are important. We study supersymmetric models with intermediate unification scale. We find concrete scenarios where the reheating temperature is of order one GeV ($M_I\sim 10^{12}$) and below. If the case that this reheating temperature is associated to the decay of oscillating moduli fields appearing in string theories, we show that the LSP relic density considerably increases with respect to the standard radiation-dominated case by the effect of the direct non-thermal production by the modulus field. The LSP can become a good dark matter candidate ($0.01-0.1 \gsim Ωh^2 \lsim 0.3-1$) for $M_I\sim 10^{12}-10^{14}$ Gev and $m_ϕ\sim 1-10$ TeV.

hep-ph↗

arXiv2002

Particle oscillations in external chaotic fields

We review here the development of the general formalism for the study of fermion propagation in the presence of stochastic media. This formalism allows the systematic derivation of evolution equations for averaged quantities as survival probabilities and higher order distribution moments. The formalism equally applies to any finite dimensional Schrödinger equation in the presence of a stochastic external field. New integrodifferential equations valid for finite correlated processes are obtained for the first time. For the particular case of exponentially correlated processes a second order ordinary equation is obtained. As a consequence, the Redfield equation valid for Gaussian delta-correlated noise is rederived in a simple way: it has been obtained directly and as the zero-order term of an asymptotic expansion in the inverse of the correlation length. The formalism, together with the quantum correlation theorem is applied to the computation of higher moments and correlation functions. It is shown that equal and unequal time correlators follow similar differential equations.

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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.

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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.

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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.

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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%.

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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.

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