Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userOscillations of the $^7$Be solar neutrinos inside the Earth
215
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We explore in detail oscillations of the solar $^7$Be neutrinos in the matter of the Earth. The depth of oscillations is about $(0.1 - 0.2)%$ and the length $approx 30$ km. The period of the oscillatory modulations in the energy scale is comparable with the width of the line determined by the temperature in the center of the Sun. The latter means that depending on the length of trajectory (nadir angle) one obtains different degree of averaging of oscillations. Exploring these oscillations it is possible to measure the width of the $^7$Be line and therefore the temperature of the Sun, determine precisely $Delta m^2_{21}$, perform tomography of the Earth, in particular, measure the deviation of its form from sphere, and detect small structures. Studies of the Be neutrinos open up a possibility to test quantum mechanics of neutrino oscillations and search for the sterile neutrinos. Accuracy of these measurements with future scintillator (or scintillator uploaded) detectors of the $sim 100$ kton mass scale is estimated.
rate research
Read More
The Sun is a source of high energy neutrinos (E > 10 GeV) produced by cosmic ray interactions in the solar atmosphere. We study the impact of three-flavor oscillations (in vacuum and in matter) on solar atmosphere neutrinos, and calculate their observable fluxes at Earth, as well as their event rates in a kilometer-scale detector in water or ice. We find that peculiar three-flavor oscillation effects in matter, which can occur in the energy range probed by solar atmosphere neutrinos, are significantly suppressed by averaging over the production region and over the neutrino and antineutrino components. In particular, we find that the relation between the neutrino fluxes at the Sun and at the Earth can be approximately expressed in terms of phase-averaged ``vacuum oscillations, dominated by a single mixing parameter (the angle theta_23).
We explore oscillations of the solar $^8$B neutrinos in the Earth in detail. The relative excess of night $ u_e$ events (the Night-Day asymmetry) is computed as function of the neutrino energy and the nadir angle $eta$ of its trajectory. The finite energy resolution of the detector causes an important attenuation effect, while the layer-like structure of the Earth density leads to an interesting parametric suppression of the oscillations. Different features of the $eta-$ dependence encode information about the structure (such as density jumps) of the Earth density profile; thus measuring the $eta$ distribution allows the scanning of the interior of the Earth. We estimate the sensitivity of the DUNE experiment to such measurements. About 75 neutrino events are expected per day in 40 kt. For high values of $Delta m^2_{21}$ and $E_ u > $11 MeV, the corresponding D-N asymmetry is about 4% and can be measured with $15%$ accuracy after 5 years of data taking. The difference of the D-N asymmetry between high and low values of $Delta m^2_{21}$ can be measured at the $4sigma$ level. The relative excess of the $ u_e$ signal varies with the nadir angle up to 50%. DUNE may establish the existence of the dip in the $eta-$ distribution at the $(2 - 3) sigma$ level.
Atmospheric neutrinos at low energies, $E lsim 500$ MeV, is known to be a rich source of information of lepton mixing parameters. We formulate a simple perturbative framework to elucidate the characteristic features of neutrino oscillation at around the solar-scale enhancement due to the matter effect. The clearest message we could extract from our perturbation theory is that CP violation in the appearance oscillation probability is large, a factor of $sim 10$ times larger than CP violation at around the atmospheric-scale oscillation maximum. Underlying mechanism for it is that one of the suppression factors on the CP phase dependent terms due to smallness of $Delta m^2_{21} / Delta m^2_{31}$ are dynamically lifted by the solar-scale enhancement. Our framework has a unique feature as a perturbation theory in which large $Delta m^2_{31}$ term outside the key 1-2 sector for the solar-scale resonance does not yield sizeable corrections. On the contrary, the larger the $Delta m^2_{31}$, the smaller the higher order corrections.
We consider a solution of the atmospheric neutrino problem based on oscillations of muon neutrinos to sterile neutrinos: $ u_{mu}$ $leftrightarrow$ $ u_s$. The zenith angle ($Theta$) dependences of the neutrino and upward-going muon fluxes in presence of these oscillations are studied. The dependences have characteristic form with two dips: at $cos Theta = -0.6 div -0.2$ and $cos Theta = -1.0 div -0.8$. The latter dip is due to parametric resonance in oscillations of neutrinos which cross the core of the earth. A comparison of predictions with data from the MACRO, Baksan and Super-Kamiokande experiments is given.
Flavour oscillations of sub-GeV atmospheric neutrinos and antineutrinos, traversing different distances inside the Earth, are a promising source of information on the leptonic CP phase $delta$. In that energy range, the oscillations are very fast, far beyond the resolution of modern neutrino detectors. However, the necessary averaging over the experimentally typical energy and azimuthal angle bins does not wash out the CP violation effects. In this paper we derive very accurate analytic compact expressions for the averaged oscillations probabilities. Assuming spherically symmetric Earth, the averaged oscillation probabilities are described in terms of two analytically calculable effective parameters. Based on those expressions, we estimate maximal magnitude of CP-violation effects in such measurements and propose optimal observables best suited to determine the value of the CP phase in the PMNS mixing matrix.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
