arXiv subjects

Petteri Keränen

Publications and source records attributed to Petteri Keränen.

6 recordsLinked to original sources

arXiv2001

Effects of periodic matter in kaon regeneration

We study the effects of periodic matter in kaon regeneration, motivated by the possibility of parametric resonance in neutrino oscillations. The large imaginary parts of the forward kaon-nucleon scattering amplitudes and the decay width difference $ΔΓ$ prevent a sizable enhancement of the $K_L\to K_S$ transition probability. However, some interesting effects can be produced using regenerators made of alternating layers of two different materials. Despite the fact that the regenerator has a fixed length one can obtain different values for the probability distribution of the $K_L$ decay into a final state. Using a two-arm regenerator set up it is possible to measure the imaginary parts of the $K^0(\bar{K}^0)$-nucleon scattering amplitudes in the correlated decays of the $ϕ$-resonance. Combining the data of the single-arm regenerator experiments with direct and reverse orders of the matter layers in the regenerator one can independently measure the CP violating parameter $δ$.

hep-ph↗

arXiv2000

Searching Scalar Resonances with Ultra-high Energy Neutrinos

We study the prospects of detecting signals of a resonant scattering of high-energy cosmic neutrinos on electrons in the atmosphere. Such a process is possible through an s-channel exchange of a isotriplet scalar particle predicted by some particle physics theories. We estimate the event rates for a reference detector setup with plausible assumptions on the interaction strengths and energy resolutions. We find as the most promising process the resonance production of tau neutrinos whose signature would be a "quiet" (in contrast with a hadronic "bang") production of the tau lepton followed by a more noisy decay in downstream.

hep-ph↗

arXiv2000

Neutrino mixing scenarios and AGN

Active galactic nuclei (AGN) have been suggested to be sources of very high energy neutrinos. We consider the possibility of using AGN neutrinos to test neutrino mixings. From the atmospheric, solar and laboratory data on neutrino oscillations we derive the flavour composition of the AGN neutrino flux in different neutrino mixing schemes. We show that most of the schemes considered can be distinguished from each other and the existence of a sterile neutrino can be specially tested. AGN neutrinos can also be used to test those four-neutrino scenarios where solar neutrinos oscillate into an arbitrary mixture of $ν_s$ and $ν_τ$.

hep-ph↗

arXiv1998

Testing neutrino magnetic moments with AGNs

We propose to test the magnetic transition moments of Majorana neutrinos by comparing the fluxes of different flavours of neutrinos coming from active galactic nuclei (AGN). We show that, with reasonable assumptions about the magnetic field of the AGN, it is possible to obtain limits on $ν_τν_{e}$ and $ν_τν_μ$ transition moments which are three to five orders of magnitude better than the laboratory limits. We also point out that with certain parameter values the ratio $ν_τ/ν_{e,μ}$, when measured from different sources, is expected to vary from zero to values somewhat higher than one, providing an unambigious signal of a magnetic transition within the AGN which cannot be explained by neutrino oscillations.

hep-ph↗

arXiv1997

Testing exotic neutrino-neutrino interactions with AGN neutrinos

We propose a test for non-standard neutrino-neutrino interactions by using ultrahigh energy AGN neutrinos. Such interactions would influence the AGN neutrino flux due to collisions with cosmic background neutrinos. For typical AGN neutrinos we obtain an upper limit for the coupling constant $g<6.4\cdot 10^{-3}$ if the mediator is light and $g/(M_X/MeV) <0.013$ if the mediator is heavy. We compare our results with constraints from other phenomena previously considered.

hep-ph↗

arXiv1996

Cosmological abundances of right-handed neutrinos

We study the equilibration of the right-helicity states of light Dirac neutrinos in the early universe by solving the momentum dependent Boltzmann equations numerically. We show that the main effect is due to electroweak gauge boson poles, which enhance thermalization rates by some three orders of magnitude. The right-helicity states of tau neutrinos will be brought in equilibrium independently of their initial distribution at a temperature above the poles if the tau neutrino mass is larger than about 10 keV.

hep-ph↗