Detecting matter effects in long baseline experiments

Experiments strongly suggest that the flavour mixing responsible for the atmospheric neutrino anomaly is very close to being maximal. Thus, it is of great theoretical as well as experimental importance to measure any possible deviation from maximality. In this context, we reexamine the effects of matter interactions in long baseline neutrino oscillation experiments. Contrary to popular belief, the muon neutrino survival probability is shown to be quite sensitive to matter effects. Moreover, for moderately long baselines, the difference between the survival probilities for $\nu_\mu$ and $\bar\nu_\mu$ is shown to be large and sensitive to the deviation of $|U_{\mu 3}|$ from maximality. Performing a realistic analysis, we demonstrate that a muon-storage ring $\nu$-source alongwith an iron calorimeter detector can measure such deviations. (Contrary to recent claims, this is not so for the NuMI--{\sc minos} experiment.) We also discuss the possible correlation in measuring $U_{\mu 3}$ and $U_{e3}$ in such experiment.Comment: 18 pages, LaTe

Antineutrinos from Earth: A reference model and its uncertainties

We predict geoneutrino fluxes in a reference model based on a detailed description of Earth's crust and mantle and using the best available information on the abundances of uranium, thorium, and potassium inside Earth's layers. We estimate the uncertainties of fluxes corresponding to the uncertainties of the element abundances. In addition to distance integrated fluxes, we also provide the differential fluxes as a function of distance from several sites of experimental interest. Event yields at several locations are estimated and their dependence on the neutrino oscillation parameters is discussed. At Kamioka we predict N(U+Th)=35 +- 6 events for 10^{32} proton yr and 100% efficiency assuming sin^2(2theta)=0.863 and delta m^2 = 7.3 X 10^{-5} eV^2. The maximal prediction is 55 events, obtained in a model with fully radiogenic production of the terrestrial heat flow.Comment: 24 pages, ReVTeX4, plus 7 postscript figures; minor formal changes to match version to be published in PR

On the Size of the Dark Side of the Solar Neutrino Parameter Space

We present an analysis of the MSW neutrino oscillation solutions of the solar neutrino problem in the framework of two-neutrino mixing in the enlarged parameter space $(\Delta m^2, \tan^2\theta)$ with $\theta \in (0,\frac{\pi}{2})$. Recently, it was pointed out that the allowed region of parameters from a fit to the measured total rates can extend to values $\theta \geq \frac{\pi}{4}$ (the so called ``dark side'') when higher confidence levels are allowed. The purpose of this letter is to reanalize the problem including all the solar neutrino data available, to discuss the dependence on the statistical criteria in the determination of the CL of the ``dark side'' and to extract the corresponding limits on the largest mixing allowed by the data. Our results show that when the Super-Kamiokande data on the zenith angle distribution of events and the spectrum information is included, the regions extend more into the dark side.Comment: 5 pages,latex file using RevTex. Two-layer aproximation for the Earth density replaced by numerical integration with PREM. Latest parametrization of the sun matter density (BP2000) is included. Misprints corrected. Conclusions unchanged. 5 postscript figures (bitmapped for compression). A full version of the paper can be found at http://ific.uv.es/~penya/papers/ To appear in Phys. Rev.

Measuring CP violation and mass ordering in joint long baseline experiments with superbeams

We propose to measure the CP phase $\delta_{\rm CP}$, the magnitude of the neutrino mixing matrix element $|U_{e3}|$ and the sign of the atmopheric scale mass--squared difference $\Delta{\rm m}^2_{31}$ with a superbeam by the joint analysis of two different long baseline neutrino oscillation experiments. One is a long baseline experiment (LBL) at 300 km and the other is a very long baseline (VLBL) experiment at 2100 km. We take the neutrino source to be the approved high intensity proton synchrotron, HIPA. The neutrino beam for the LBL is the 2-degree off-axis superbeam and for the VLBL, a narrow band superbeam. Taking into account all possible errors, we evaluate the event rates required and the sensitivities that can be attained for the determination of $\delta_{\rm CP}$ and the sign of $\Delta m^2_{31}$. We arrive at a representative scenario for a reasonably precise probe of this part of the neutrino physics.Comment: 25 RevTEX pages, 16 PS figures, revised figure captions and references adde

Present and Future Bounds on Non-Standard Neutrino Interactions

We consider Non-Standard neutrino Interactions (NSI), described by four-fermion operators of the form $(\bar{\nu}_{\alpha} \gamma {\nu}_{\beta}) (\bar{f} \gamma f)$, where $f$ is an electron or first generation quark. We assume these operators are generated at dimension $\geq 8$, so the related vertices involving charged leptons, obtained by an SU(2) transformation $\nu_{\delta} \to e_{\delta}$, do not appear at tree level. These related vertices necessarily arise at one loop, via $W$ exchange. We catalogue current constraints from $\sin^2 \theta_W$ measurements in neutrino scattering, from atmospheric neutrino observations, from LEP, and from bounds on the related charged lepton operators. We estimate future bounds from comparing KamLAND and solar neutrino data, and from measuring $\sin^2 \theta_W$ at the near detector of a neutrino factory. Operators constructed with $\nu_\mu$ and $\nu_e$ should not confuse the determination of oscillation parameters at a $\nu$factory, because the processes we consider are more sensitive than oscillations at the far detector. For operators involving $\nu_\tau$, we estimate similar sensitivities at the near and far detector.Comment: Erratum added at the end of the documen

Geophysical constraints on mirror matter within the Earth

We have performed a detailed investigation of geophysical constraints on the possible admixture of mirror matter inside the Earth. On the basis of the Preliminary Reference Earth Model (PREM) -- the `Standard Model' of the Earth's interior -- we have developed a method which allows one to compute changes in various quantities characterising the Earth (mass, moment of inertia, normal mode frequencies etc.)due to the presence of mirror matter. As a result we have been able to obtain for the first time the direct upper bounds on the possible concentration of the mirror matter in the Earth. In terms of the ratio of the mirror mass to the Earth mass a conservative upper bound is $3.8\times 10^{-3}$. We then analysed possible mechanisms (such as lunar and solar tidal forces, meteorite impacts and earthquakes) of exciting mirror matter oscillations around the Earth centre. Such oscillations could manifest themselves through global variations of the gravitational acceleration at the Earth's surface. We conclude that such variations are too small to be observed. Our results are valid for other types of hypothetical matter coupled to ordinary matter by gravitation only (e.g. the shadow matter of superstring theories).Comment: 25 pages, in RevTeX, to appear in Phys.Rev.

Atmospheric Neutrino Oscillations and New Physics

We study the robustness of the determination of the neutrino masses and mixing from the analysis of atmospheric and K2K data under the presence of different forms of phenomenologically allowed new physics in the nu_mu--nu_tau sector. We focus on vector and tensor-like new physics interactions which allow us to treat, in a model independent way, effects due to the violation of the equivalence principle, violations of the Lorentz invariance both CPT conserving and CPT violating, non-universal couplings to a torsion field and non-standard neutrino interactions with matter. We perform a global analysis of the full atmospheric data from SKI together with long baseline K2K data in the presence of nu_mu -> nu_tau transitions driven by neutrino masses and mixing together with sub-dominant effects due to these forms of new physics. We show that within the present degree of experimental precision, the extracted values of masses and mixing are robust under those effects and we derive the upper bounds on the possible strength of these new interactions in the nu_mu--nu_tau sector.Comment: 22 pages, LaTeX file using RevTEX4, 5 figures and 4 tables include

Iron under Earth's core conditions: Liquid-state thermodynamics and high-pressure melting curve

{\em Ab initio} techniques based on density functional theory in the projector-augmented-wave implementation are used to calculate the free energy and a range of other thermodynamic properties of liquid iron at high pressures and temperatures relevant to the Earth's core. The {\em ab initio} free energy is obtained by using thermodynamic integration to calculate the change of free energy on going from a simple reference system to the {\em ab initio} system, with thermal averages computed by {\em ab initio} molecular dynamics simulation. The reference system consists of the inverse-power pair-potential model used in previous work. The liquid-state free energy is combined with the free energy of hexagonal close packed Fe calculated earlier using identical {\em ab initio} techniques to obtain the melting curve and volume and entropy of melting. Comparisons of the calculated melting properties with experimental measurement and with other recent {\em ab initio} predictions are presented. Experiment-theory comparisons are also presented for the pressures at which the solid and liquid Hugoniot curves cross the melting line, and the sound speed and Gr\"{u}neisen parameter along the Hugoniot. Additional comparisons are made with a commonly used equation of state for high-pressure/high-temperature Fe based on experimental data.Comment: 16 pages including 6 figures and 5 table

The role of matter density uncertainties in the analysis of future neutrino factory experiments

Matter density uncertainties can affect the measurements of the neutrino oscillation parameters at future neutrino factory experiments, such as the measurements of the mixing parameters $\theta_{13}$ and \deltacp. We compare different matter density uncertainty models and discuss the possibility to include the matter density uncertainties in a complete statistical analysis. Furthermore, we systematically study in which measurements and where in the parameter space matter density uncertainties are most relevant. We illustrate this discussion with examples that show the effects as functions of different magnitudes of the matter density uncertainties. We find that matter density uncertainties are especially relevant for large \stheta \gtrsim 10^{-3}. Within the KamLAND-allowed range, they are most relevant for the precision measurements of \stheta and \deltacp, but less relevant for ``binary'' measurements, such as for the sign of \ldm, the sensitivity to \stheta, or the sensitivity to maximal CP violation. In addition, we demonstrate that knowing the matter density along a specific baseline better than to about 1% precision means that all measurements will become almost independent of the matter density uncertainties.Comment: 21 pages, 7 figures, LaTeX. Final version to be published in Phys. Rev.