An effective two-flavor approximation for neutrino survival probabilities in matter

Author(s)

Minakata, Hisakazu

• Document type: Journal article
• Source: Journal of High Energy Physics; v. N/A, n. 5, p. 26-pg., 2017-05-09.

Abstract

It is known in vacuum that the three-flavor neutrino survival probability can be approximated by the effective two-flavor form to first orders in epsilon equivalent to Delta m(21)(2)/Delta m(31)(2), with introduction of the effective Delta m(alpha alpha)(2) (alpha = e, mu, tau), in regions of neutrino energy E and baseline L such that Delta m(31)(2)L/2E similar to pi. Here, we investigate the question of whether the similar effective two-flavor approximation can be formulated for the survival probability in matter. Using a perturbative framework with the expansion parameters epsilon and s(13) proportional to root epsilon, we give an affirmative answer to this question and the resultant two-flavor form of the probability is valid to order epsilon. However, we observe a contrived feature of the effective Delta m(alpha alpha)(2)(a) in matter. It ceases to be a combination of the fundamental parameters and has energy dependence, which may be legitimate because it comes from the matter potential. But, it turned out that Delta m(mu mu)(2) (a) becomes L-dependent, though Delta m(ee)(2)(a) is not, which casts doubt on adequacy of the concept of effective Delta m(2) in matter. We also find that the appearance probability in vacuum admits, to order epsilon, the similar effective two-flavor form with a slightly different effective Delta m(beta alpha)(2) from the disappearance channel. A general result is derived to describe suppression of the matter effect in the oscillation probability. (AU)

• FAPESP's process: 15/05208-4 - Physics of neutrinos
• Grantee: Renata Zukanovich Funchal
• Support Opportunities: Research Grants - Visiting Researcher Grant - International