Neutrino Tomography of the Earth with ORCA Detector

Abstract

Using PREM as a reference model for the Earth density distribution we investigate in the present article the sensitivity of the ORCA detector to deviations of the Earth i) outer core (OC) density, ii) inner core (IC) density, iii) total core density, and iv) mantle density, from their respective PREM densities. The analysis is performed by studying the effects of the Earth matter on the oscillations of atmospheric ν µ , ν e , νµ and νe . We present results which, in particular, illustrate the dependence of the ORCA sensitivity to the OC, IC, core and mantle densities on the type of systematic uncertainties used in the analysis, on the value of the atmospheric neutrino mixing angle θ 23 , on whether the Earth mass constraint is implemented or not, and on the way it is implemented, and on the type -with normal ordering (NO) or inverted ordering (IO) -of the light neutrino mass spectrum. We show, in particular, that in the "most favorable" NO case of implemented Earth mass constraint, "minimal" systematic errors and sin 2 θ 23 = 0.58, ORCA can determine, e.g., the OC (mantle) density at 3σ C.L. after 10 years of operation with an uncertainty of (-18%)/+15% (of (-6%)/+8%). In the "most disfavorable" NO case of "conservative" systematic errors and sin 2 θ 23 = 0.42, the uncertainty reads (-43%)/+39% ((-17%/+20%), while for for sin 2 θ 23 = 0.50 and 0.58 it is noticeably smaller: (-37)%/+30% and (-30%)/+24% ((-13%)/+16% and (-11%/+14%)). We find also that the sensitivity of ORCA to the outer core, core and mantle densities is significantly worse for IO neutrino mass spectrum.

Locating the Core-Mantle Boundary using Oscillations of Atmospheric Neutrinos

“…The possibility of probing the internal structure of Earth using these density-dependent matter effects is known as "neutrino oscillation tomography". These studies have been performed using man-made neutrino beams [59][60][61][62][63][64][65][66][67][68][69], supernova neutrinos [70,71], solar neutrinos [70,[72][73][74][75][76][77], and atmospheric neutrinos [78][79][80][81][82][83][84][85][86][87][88][89][90][91][92]. In the sub-GeV and multi-GeV energy ranges, atmospheric neutrinos are the best source of neutrinos to probe the internal structure of Earth because they have access to a wide range of baselines starting from about 15 km to 12750 km which cover all the layers of Earth.…”

“…Sensitivity studies for current and future atmospheric neutrino experiments like IceCube [79], Oscillation Research with Cosmics in the Abyss (ORCA) [93], Deep Underground Neutrino Experiment (DUNE) [94], Hyper-Kamiokande (Hyper-K) [95], and Iron Calorimeter (ICAL) detector [85] have been performed. These studies have shown how to detect the presence of core-mantle boundary (CMB) using ICAL [85], constrain the average densities of the core, and the mantle using ORCA [80,87,88,92] and DUNE [86], determine the position of the core-mantle boundary using DUNE [89], and explore the chemical composition of the Earth core using Hyper-K and IceCube [79] as well as ORCA [81-83, 87, 91, 92].…”

Neutrino oscillations in Earth for probing dark matter inside the core

“…The advancement in the precision of oscillation parameters with non-zero value of reactor mixing angle θ 13 has opened the door for Earth tomography based on matter effects on the oscillations of neutrinos in the multi-GeV energy range, which easily penetrate through the core. The possibility of such a "neutrino oscillation tomography" has been studied using man-made neutrino beams [36][37][38][39][40][41][42][43][44][45][46], solar neutrinos [47][48][49][50][51][52][53], supernova neutrinos [49,54], and atmospheric neutrinos [55][56][57][58][59][60][61][62][63][64][65][66]. During this propagation, neutrinos undergo charged-current interactions with ambient electrons and experience an effective Earth matter potential…”

“…Since atmospheric neutrinos have energies in the multi-GeV range where the Earth matter effects are significant, and since about ∼ 20% of the upward-going atmospheric neutrinos observed at a detector would have passed through the core, this would be the best source of neutrinos to probe the core of the Earth. The use of atmospheric neutrinos for constraining the average densities of the core and the mantle using ORCA [57,63,66] and DUNE [64], for detecting the core-mantle boundary (CMB) using ICAL [62], and for determining the position of the core-mantle boundary using DUNE [65] has already been proposed. Note that the Earth matter effects on neutrinos depend on the electron density, as opposed to the matter density that the seismic waves are mainly sensitive to.…”