2014: Electromagnetic properties of neutrino: new mechanism of generation of pulsar rotation and new bounds on neutrino electric millicharge

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The Neutrino Theory Group at the Faculty of Physics of Lomonosov Moscow State University headed by Prof. Alexander Studenikin received in 2014 a number of novel important results on neutrino electromagnetic properties and phenomenological applications: (i) a new neutrino mechanism of generation of a pulsar rotating that is termed Neutrino Star Turning mechanism has been predicted; (ii) the theory of neutrino-atom collisions has been developed; (iii) a new upper bound on a neutrino millicharge has been obtained.

The last two years has been celebrated by a reasonable step further in development of high energy physics. The prediction of the now-termed BEH symmetry breaking mechanism, attributed to Robert Brout, Francois Englert and Peter Higgs, recently supported by an excellent job done by two CERN collaborations for discovering of the Higgs boson, provides the final glorious triumph of the Standard Model. And now a question appears: does physics beyond the Standard Model exist? What is next?

The direct answer to these questions should be given by neutrinos. Within the initial formulation of the Standard Model neutrinos are massless particles. However, already now it is known that the Standard Model should be extended to some more general theory in particular because of neutrinos which are the only particles exhibiting experimentally well-confirmed properties beyond the Standard Model. This is because of neutrino mixing and oscillations supported by the discovery of flavour conversion of neutrinos from different sources, the effect that is not possible for massless neutrinos. In many extensions of the Standard Model, which account for neutrino masses and mixings, neutrinos acquire nontrivial electromagnetic properties that hence allow direct electromagnetic interactions of neutrinos with electromagnetic fields and charged particles or with particles which have magnetic moments. Unfortunately, in spite of reasonable efforts in studies of neutrino electromagnetic properties, up to now there is no experimental confirmation, neither from terrestrial laboratories studies nor from astrophysical observations, in favour of non-vanishing neutrino electromagnetic characteristics. However, experimentalists and theorists are eagerly searching for them and once being experimentally confirmed they will open a window to new physics beyond the Standard Model. It is expected that neutrino electromagnetic properties should have important consequences in astrophysics where dense media being under the influence of strong magnetic fields are present.

The up-dated and the most complete review on neutrino electromagnetic properties and phenomenological consequences is given in the paper recently published by the supervisor of the Neutrino Theory Group of MSU in co-operation with two INFN (Italy) members: C.Broggini, C.Giunti, A.Studenikin, Adv. High Energy Phys. 47, 459526 (2012).

The Neutrino Theory Group, headed by Prof. Alexander Studenikin, includes students, post-graduate student and a few staff members from the Faculty of Physics of Lomonosov Moscow State University, as well as from Moscow Physics and Engendering University, the Institute for Nuclear Research of the Russian Academy of Sciences and the Joint Institute for Nuclear Research (Dubna). For many years a systematic studies has been performed by the Neutrino Theory Group on the neutrino electromagnetic properties and interactions under the influence of extreme dense matter and strong electromagnetic fields. The following new important results have been obtained by the Neutrino Theory Group in 2014

  1. a new mechanism of changing a star rotation angular velocity (that is due to neutrinos motion on curved orbits inside a rotating and magnetized stars) has been predicted, the mechanism is termed «Neutrino Star Turning» mechanism (νST); it is predicted that this mechanism can explain the observed sudden shifts of the rotations frequencies of pulsars (the so called glitches of pulsars); on this bases the present world best astrophysical upper limit on the neutrino millicharge on the order of qν < 1.3*10-19 e0 (here e0 is the absolute value of an electron charge) has been obtained [A.Studenikin, I.Tokarev, Nucl. Phys. B 396, 884 (2014)], this limit is three orders of magnitude stronger than those available in literature and included by the Particle Data Group Collaboration to the Review of Particle Physics 2012;
  2. a new important contribution to the theory of neutrino-atom scattering has been made that enabled the authors to show that the existing in literature statement on possible many of orders magnitude increase of the neutrino-electron scattering cross section due to electron binding in atoms is erroneous [K.Kouzakov, A.Studenikin, Adv. High Energy Phys. 2014, 569409 (2014)]; this result is of particular importance for performing a correct analysis of experimental data of the GEMMA experiment on measurements of the reactor antineutrino-electron scattering now running at the Kalinin Power Plant (Russia) and really provides a proof that the obtained by the GEMMA Collaboration upper limit on the neutrino magnetic moment is indeed the world best upper bound on this neutrino electromagnetic characteristic;
  3. it has been proposed and realized a new approach for getting bounds on a neutrino millicharge from the experimental data on antineutrino-electron scattering obtained by the GEMMA Collaboration and a new limit on the millicharge has been obtained [A. Studenikin, Eur. Phys. Lett. 107, 21001 (2014)].