On the possible existence of a neutrino pulsar
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EMENTARY PARTICLES AND FIELDS Theory
On the Possible Existence of a Neutrino Pulsar R. A. Anikin* , A. V. Kuznetsov** , and N. V. Mikheev*** Yaroslavl State University, ul. Sovetskaya 14, Yaroslavl, 150000 Russia Received March 23, 2010
Abstract—If the neutrino has a magnetic moment in the interval 10−13 μB < μν < 10−12 μB and if a magnetic field of strength about 1014 G exists in the supernova envelope, the effect of a pulsation of a neutrino signal from a supernova may arise owing to a νL → νR resonance transition in the envelope magnetic field. DOI: 10.1134/S1063778810110189
Within the Standard Model extended to include neutrino masses mν , the neutrino possesses a magnetic moment [1, 2], m 3eGF mν ν √ = 3.20 × 10−19 μB , (1) μν(SM) = 1 eV 8π 2 2 where μB = e/2me is the Bohr magneton.1) However, this value can be considered as an unobservably small in view of the known constraints on the neutrino masses. On the other hand, various nontrivial extensions of the Standard Model, such as broken left–right symmetry [3–7], admit substantially larger values of the neutrino magnetic moment [8–10]. In general, it is reasonable to consider the magneticmoment matrix μνi νj ≡ μij (that is, both the diagonal and transition magnetic moments), where νi and νj are neutrino mass eigenstates. The neutrino states ν characterized by specific flavors and produced in weak processes are superpositions of the states νi ; that is, Ui∗ νi , (2) ν = i
where Ui is the Pontecorvo–Maki–Nakagawa– Sakata unitary lepton-mixing matrix. For the sake of simplicity, we will henceforth employ the effective value of the magnetic moment. By way of example, we indicate that, for processes involving an initial electron neutrino, we mean by μ2ν the quantity 2 2 2 . μ U (3) μν → μν e ≡ ij ej i j *
E-mail: [email protected] E-mail: [email protected] *** E-mail: [email protected] 1) We make use of a natural system of units where c = = 1; e > 0 is an elementary charge. **
For initial muon neutrinos and tau neutrinos, we will use the analogous definitions. Considerable interest in the neutrino magnetic moment arose after the spectacular event of an SN1987A supernova explosion [11–13] in connection with a simulation of the supernova explosion, where the giant outgoing neutrino flux does in fact determine the energy features of the process. This means that the magnetic moment, which is a microscopic feature of the neutrino, could have a crucial effect on macroscopic properties of such astrophysical events. In the present study, we consider the time evolution that may be induced in the neutrino signal from a supernova by neutrino-helicity oscillations in which active electron neutrinos and antineutrinos of the main neutrino flux go over in the magnetic field of the supernova-core envelope to a form that is sterile with respect to weak interaction, νL → νR , ν¯R → ν¯L . On the basis of an analysis performed with allowance for detailed data on radial distributions obtained for supernova physical parameters within a specific mode
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