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Register a new userDetermination of the Source Flavor Ratio of Ultrahigh Energy Neutrinos
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We discuss the reconstruction of neutrino flavor neutrino at a distant source in the very high en- ergy regime. This reconstruction procedure is relevant to the confirmation of detecting cosmogenic neutrinos, for example. To facilitate such a reconstruction, it is imperative to achieve effective flavor discriminations in terrestrial neutrino telescopes. We note that, for energies beyond few tens of PeV, a tau-lepton behaves like a track similar to a muon. Hence, while it is rather challenging to separate { u}{mu} from { u}{tau} in this case, one can expect to isolate { u}e from the rest by a distinctive shower signature. We present the result of flavor ratio reconstruction given the anticipated accuracies of flavor measurement in neutrino telescopes and current uncertainties of neutrino mixing parame- ters. It is shown that the further separation between { u}{mu} and { u}{tau} events does not improve the flavor reconstruction due to the approximate { u}{mu} - { u}{tau} symmetry.
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We discuss the reconstruction of neutrino flavor ratios at astrophysical sources through the future neutrino-telescope measurements. Taking the ranges of neutrino mixing parameters $theta_{ij}$ as those given by the current global fit, we demonstrate by a statistical method that the accuracies in the measurements of energy-independent ratios $Requivphi ( u_{mu})/(phi ( u_{e})+phi ( u_{tau}))$ and $Sequivphi ( u_e)/phi ( u_{tau})$ among integrated neutrino flux should both be better than 10% in order to distinguish between the pion source and the muon-damped source at the $3 sigma$ level. The 10% accuracy needed for measuring $R$ and $S$ requires an improved understanding on the background atmospheric neutrino flux to a better than 10% level in the future. We discuss the applicability of our analysis to practical situations that the diffuse astrophysical neutrino flux arises from different types of sources and each point source has a neutrino flavor ratio varying with energies. We also discuss the effect of leptonic CP phase on the flavor-ratio reconstruction.
In this paper, we propose a hexagonal description for the flavor composition of ultrahigh-energy (UHE) neutrinos and antineutrinos, which will hopefully be determined at the future large neutrino telescopes. With such a geometrical description, we are able to clearly separate the individual flavor composition of neutrinos from that of antineutrinos in one single regular hexagon, which can be regarded as a natural generalization of the widely-used ternary plot. For illustration, we consider the $pp$ or $pgamma$ collisions as the dominant production mechanism for UHE neutrinos and antineutrinos in the cosmic accelerator, and investigate how neutrino oscillations in the standard picture and in the presence of Lindblad decoherence could change the flavor composition of neutrinos and antineutrinos at neutrino telescopes.
The muon charge ratio of ultrahigh energy cosmic rays may provide information to detect the composition of the primary cosmic rays. We propose to extract the charge information of high energy muons in very inclined extensive air showers by analyzing their relative lateral positions in the shower transverse plane.
The texture zero mass matrices for the quarks and leptons describe very well the flavor mixing of the quarks and leptons. We can calculate the angles of the unitarity triangle. We expect the angle alpha of the unitarity triangle to be 90 degrees. The masses of the neutrinos can be calculated - they are very small, the largest neutrino mass is 0.05 eV. We calculated the matrix element of the mixing matrix, relevant for the reactor mixing angle. It can be measured in the near future in the DAYA BAY experiment.
A diffuse flux of astrophysical neutrinos above $100,mathrm{TeV}$ has been observed at the IceCube Neutrino Observatory. Here we extend this analysis to probe the astrophysical flux down to $35,mathrm{TeV}$ and analyze its flavor composition by classifying events as showers or tracks. Taking advantage of lower atmospheric backgrounds for shower-like events, we obtain a shower-biased sample containing 129 showers and 8 tracks collected in three years from 2010 to 2013. We demonstrate consistency with the $(f_e:f_{mu}:f_tau)_oplusapprox(1:1:1)_oplus$ flavor ratio at Earth commonly expected from the averaged oscillations of neutrinos produced by pion decay in distant astrophysical sources. Limits are placed on non-standard flavor compositions that cannot be produced by averaged neutrino oscillations but could arise in exotic physics scenarios. A maximally track-like composition of $(0:1:0)_oplus$ is excluded at $3.3sigma$, and a purely shower-like composition of $(1:0:0)_oplus$ is excluded at $2.3sigma$.
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