Plasma induced neutrino spin-flip in a supernova and new bounds on the neutrino magnetic moment
A. V. Kuznetsov, N. V. Mikheev
备注：
10 pages, LaTeX, 6 eps figures, based on the talk presented at the XIV International School ``Particles and Cosmology'', Baksan Valley, Kabardino Balkaria, Russia, April 16-21, 2007, to appear in the Proceedings
The neutrino chirality-flip process under the conditions of the supernova core is investigated in detail with the plasma polarization effects in the photon propagator taken into account in a more complete form than in earlier publications. It is shown in part that the contribution of the proton fraction of plasma is essential. New upper bounds on the neutrino magnetic moment are obtained: mu_nu < (0.5 - 1.1) 10^{-12} mu_B from the limit on the supernova core luminosity for nu_R emission, and mu_nu < (0.4 - 0.6) 10^{-12} mu_B from the limit on the averaged time of the left-handed neutrino washing out. The best upper bound on the neutrino magnetic moment from SN1987A is improved by the factor of 3 to 7.
We show that in a supernova core the longitudinal photon (plasmon) has a space-like dispersion and Cerenkov absorption and emission of such photons is kinematically allowed. If the neutrino has a non-zero magnetic moment, then helicity flipping Cerenkov absorption of a plasmon $ν_L+γ\toν_R$ is the most efficient cooling mechanism of the supernova core, and this allows us to put a restrictive bound on the neutrino magnetic moment $μ_ν~<~0.7\times 10^{-13}μ_B$.
The neutrino chirality-flip process under the conditions of the supernova core is investigated in detail with the plasma polarization effects in the photon propagator taken into account, in a more consistent way than in earlier publications. It is shown in part that the contribution of the proton fraction of plasma is essential. New upper bounds on the neutrino magnetic moment are obtained: mu_nu < (0.5 - 1.1) 10^{-12} mu_B from the limit on the supernova core luminosity for nu_R emission, and mu_nu < (0.4 - 0.6) 10^{-12} mu_B from the limit on the averaged time of the neutrino spin-flip. The …
The neutrino spin flip radiative conversion processes nu_L -> nu_R + gamma^* and nu_L + gamma^* -> nu_R in medium are considered. It is shown in part that an analysis of the so-called spin light of neutrino without a complete taking account of both the neutrino and the photon dispersion in medium is physically inconsistent.
The fermion spin-flip conversion $f_L \to f_R + γ$ is considered, caused by the difference of the additional energies of the electroweak origin, acquired by left- and right-handed fermions (neutrino, electron) in medium. An accurate taking account of the fermion and photon dispersion in medium is shown to be important.
The fermion spin-flip conversion f_L -> f_R + gamma is considered, caused by the difference of the additional energies of the electroweak origin, acquired by left- and right-handed fermions (neutrino, electron) in medium. An accurate taking account of the fermion and photon dispersion in medium is performed. It is shown that the threshold arises in the process, caused by the photon (plasmon) effective mass. This threshold leaves no room for the so-called ``spin light of neutrino'' and ``spin light of electron'' in the real astrophysical situations.
The neutrino chirality-flip process under the conditions of the supernova core is investigated in detail with the plasma polarization effects in the photon propagator taken into account. It is shown that the contribution of the proton fraction of plasma is essential. New upper bounds on the neutrino magnetic moment are obtained: mu_nu < (0.5 - 1.1) 10^{-12} mu_B from the limit on the supernova core luminosity for nu_R emission, and mu_nu < (0.4 - 0.6) 10^{-12} mu_B from the limit on the averaged time of the neutrino spin-flip. The best astrophysical upper bound on the neutrino magnetic moment …
Neutrino with magnetic moment can experience a chirality flip while scattering off charged particles. This effect may lead to important consequences for the dynamics and the neutrino signal of the core-collapse supernova. It is known that if neutrino is a Dirac fermion, then nu_L->nu_R transition induced by the chirality flip leads to the emission of sterile right-handed neutrinos. The typical energies of these neutrinos are rather high, E ~ (100-200)MeV. Neutrino spin precession in the magnetic field either inside the collapsing star or in the interstellar space may lead to the backward trans…
For neutrinos with a magnetic moment, we show that the collisions in a hot and dense plasma act as an efficient mechanism for the conversion of $ν_L$ into $ν_R$. The production rate for right-handed neutrinos is computed in terms of a resummed photon propagator which consistently incorporates the background effects. Assuming that the entire energy in a supernova collapse is not carried away by the $ν_R$, our results can be used to place an upper limit on the neutrino magnetic moment $μ_ν< (0.1-0.4)\times 10^{-11}μ_B$
The spin effects on electromagnetic waves in a strongly magnetized plasma with rare collisions is considered with the help of relativistic kinetic equations, which takes into account the electron spin dynamics in the selfconsistent electric and magnetic fields. It is shown that for electromagnetic waves propagating almost perpendicular to ambient magnetic field the spin effects become essential in the vicinity of electron gyrofrequency and the corresponding wave dispersion and growth rate of the electromagnetic spin waves in the presence of intense quasi monoenergetic fluxes of neutrino is det…
It is known that if neutrino is a Dirac fermion with magnetic moment, then ν_L -> ν_R -> ν_L transition of supernova neutrinos may occur. The first stage of such transition is due to the neutrino spin flip inside the hot dense supernova core, while the second one - due to the neutrino spin precession in the galactic magnetic field on the way from the supernova to terrestrial detectors. This can result in the detection of 60-200 MeV neutrinos simultaneously with the "normal" supernova neutrino signal, which would be a smoking gun for the Dirac neutrino magnetic moment, μ. We argue that in case …
The neutrino helicity-flip process under the conditions of the supernova core is reinvestigated. Instead of the uniform ball model for the SN core used in previous analyses, realistic models for radial distributions and time evolution of physical parameters in the SN core are considered. A new upper bound on the Dirac neutrino magnetic moment is obtained from the limit on the supernova core luminosity for nu_R emission.
We calculated the matter effect, including both the Earth and supernova, on the detection of neutrinos from type II supernovae at the proposed Daya Bay reactor neutrino experiment. It is found that apart from the dependence on the flip probability P_H inside the supernova and the mass hierarchy of neutrinos, the amount of the Earth matter effect depends on the direction of the incoming supernova neutrinos, and reaches the biggest value when the incident angle of neutrinos is around 93^\circ. In the reaction channel \barν_e + p --> e^+ + n the Earth matter effect can be as big as about 12%. For…
The electron screening strong effect on the electron energy and threshold energy of the beta decay reaction. in this paper, we study the $β^-$ decay rates of some iron isotopes. The electron screening beta decay rates increase by about two orders of magnitude. The strong screening beta decay rates due to Q-value correction are by more than one order of magnitude higher than those of without Q-value correction.
We show that the backreaction of left-handed neutrinos out of equilibrium on the matter sector induces an electric current proportional to a magnetic field even without a chiral imbalance for electrons in core-collapse supernovae. We derive the transport coefficient of this effect based on the recently formulated chiral radiation transport theory for neutrinos. This chiral electric current generates a strong magnetic field via the so-called chiral plasma instability, which could provide a new mechanism for the strong and stable magnetic field of magnetars. We also numerically study the physica…
One examines the interaction and possible resonances between supernova neutrinos and electron plasma waves. The neutrino phase space distribution and its boundary regions are analyzed in detail. It is shown that the boundary regions are too wide to produce non-linear resonant effects. The growth or damping rates induced by neutrinos are always proportional to the neutrino flux and $G_{\rm F}^{2}$.
Collective interactions of a beam of neutrinos/antineutrinos traversing a dense magnetized plasma of electrons/positrons, protons and neutrons are studied with particular reference to the case of a Supernova. We find that the ponderomotive force exerted by neutrinos gives, contrary to expectations, a negligible contribution to the revival of the shock for a successful Supernova explosion, although new types of convection and plasma cooling processes induced by the ponderomotive force could be, in principle, relevant for the dynamics itself.
For Dirac neutrinos with magnetic moment, we compute the production rate for right-handed neutrinos in a hot and dense QED plasma containing an initial population of left-handed neutrinos thermally distributed. The most important mechanisms for $ν_L$ depolarization, or production of right-handed neutrinos, are the $ν_L \to ν_R$ chirality flip and the plasmon decay to $\barν_L + ν_R$. The rates for these processes are computed in terms of a resummed photon propagator which consistently incorporates the background effects to leading order. Applying the results to the cases of supernovae core col…
Chirality of neutrinos modifies the conventional kinetic theory and hydrodynamics, leading to unusual chiral transport related to quantum anomalies in field theory. We argue that these corrections have new phenomenological consequences for hot and dense neutrino gases, especially in core-collapse supernovae. We find that the neutrino density can be converted to the fluid helicity through the chiral vortical effect. This fluid helicity effectively acts as a chiral chemical potential for electrons via the momentum exchange with neutrinos and induces a "helical plasma instability" that generates …
The active-sterile neutrino conversion is studied for neutrino propagating in the axial potential generated by magnetised electron plasma in the supernova medium. We consider the effect of random magnetic field $B_{rms}$ on the average neutrino conversion probability. We obtained the constraint on $Δm^2$ and $\sin^2 2θ$ for different strength of the random magnetic fields, by considering the positive definiteness of the average neutrino conversion probability inside the supernova core. Our calculation shows that, $B_{rms}\le 0.63\times 10^{14}$ Gauss is preferable so that small values of $Δm^2…
Mohanty and Samal have shown that the magnetic-moment interaction with nucleons contributes significantly to the photon dispersion relation in a supernova core, and with an opposite sign relative to the usual plasma effect. Because of a numerical error they overestimated the magnetic-moment term by two orders of magnitude, but it is still of the same order as the plasma effect. It appears that the Cherenkov processes gamma+nu -> nu and nu -> nu+gamma remain forbidden, but a final verdict depends on a more detailed investigation of the dynamical magnetic susceptibility of a hot nuclear medium.
We have recently proposed a mechanism of photon-axion oscillations as a way of rendering supernovae dimmer without cosmic acceleration. Subsequently, it has been argued that the intergalactic plasma may interfere adversely with this mechanism by rendering the oscillations energy dependent. Here we show that this energy dependence is extremely sensitive to the precise value of the free electron density in the Universe. Decreasing the electron density by only a factor of 4 is already sufficient to bring the energy dependence within the experimental bounds. Models of the intergalactic medium show…
Dark matter could have a small electromagnetic charge, provided the charge-to-mass ratio is much less than that of electrons or protons. This candidate, commonly known as millicharged dark matter (mDM), would form a plasma and interact with the interstellar medium and electromagnetic fields within galaxies. In general, understanding the dynamics of mDM requires consideration of collective plasma effects. It has been proposed that mDM can be accelerated in supernova remnants, forming a dark cosmic ray population that would leave distinct experimental signatures. In this work, we study a microph…
Neutrinos with a magnetic dipole moment propagating in a medium with a velocity larger than the phase velocity of light emit photons by the Cerenkov process. The Cerenkov radiation is a helicity flip process via which a left-handed neutrino in a supernova core may change into a sterile right-handed one and free-stream out of the core. Assuming that the luminosity of such sterile right-handed neutrinos is less than $10^{53}$ ergs/sec gives an upper bound on the neutrino magnetic dipole moment $μ_ν< 0.2 \times 10^{-13} μ_B$. This is two orders of magnitude more stringent than the previously esta…
The double conversion of the neutrino helicity $ν_L \to ν_R \to ν_L$ has been analyzed for supernova conditions, where the first stage is due to the interaction of the neutrino magnetic moment with plasma electrons and protons in the supernova core, and the second stage, due to the resonance spin flip of the neutrino in the magnetic field of the supernova envelope. It is shown that, in the presence of the neutrino magnetic moment in the range $10^{-13} μ_{\rm B} < μ_ν< 10^{-12} μ_{\rm B}$ and a magnetic field of $\sim 10^{13}$ G between the neutrinosphere and the shock-stagnation region, an ad…
Strong magnetic field inside degenerate relativistic plasma and the impacts on the neutrino transport in Core-Collapse Supernovae
Peking University（北京大学）；Yunnan Observatories, Chinese Academy of Sciences (CAS)（中国科学院云南天文台）；Beihang University（北京航空航天大学）；The University of Tokyo（东京大学）；National Astronomical Observatory of Japan（日本国立天文台）
We investigate the neutrino helicity-flip process under supernova core conditions, where the left-handed neutrinos being produced can be converted into right-handed neutrinos sterile with respect to the weak interaction due to the interaction of magnetic moments with plasma electrons and protons. Instead of the uniform ball model for the SN core used in previous analyses, realistic models for radial distributions and time evolution of physical parameters in the supernova core are considered. We have obtained new upper limits on the Dirac neutrino magnetic moment averaged over flavours and time…
We derive semiclassical neutrino-electron transport equations in the collisionless (Vlasov) limit from the coupled Dirac equations, incorporating the charged and neutral weak current-current as well as electromagnetic interactions. A corresponding linear response theory is derived. In particular, we calculate the response functions for a variety of beam-plasma geometries, which are of interest in a supernova scenario. We apply this to the study of plasmons and to a new class of collective {\it pharon} resonance modes, which are characterized by $ω< q$. We find that the growth rates of the unst…
We would like to discuss prospects for neutrino observations of the core-collapse supernova progenitor during neutrino-cooled stage. We will present new theoretical results on thermal neutrino and antineutrino spectra produced deep inside the pre-supernova core. Three competing processes: pair-, photo and plasma-neutrino production, are taken into account. The results will be used to estimate signal in existing and future neutrino detectors. Chance for supernova prediction is estimated, with possible aid to core-collapse neutrino and gravitational wave detectors in the form of early warning.
The process of the two-step conversion of the neutrino helicity, $ν_L \to ν_R \to ν_L$, is analysed in the supernova conditions, where the first stage is realized due to the interaction of the neutrino magnetic moment with the plasma electrons and protons in the supernova core. The second stage is caused by the neutrino resonant spin-flip in a magnetic field of the supernova envelope. Given the neutrino magnetic moment within the interval $10^{-13} μ_{\rm B} < μ_ν< 10^{-12} μ_{\rm B}$, and with the existence of the magnetic field at the scale $\sim 10^{13}$ G between the neutrinosphere and the…
Quantum field theory is applied to study the interaction of an electron plasma with an intense neutrino flux. A connection is established between the field theory results and classical kinetic theory. The dispersion relation and damping rate of the plasma longitudinal waves are derived in the presence of neutrinos. It is shown that Supernova neutrinos are never collimated enough to cause non-linear effects associated with a neutrino resonance. They only induce neutrino Landau damping, linearly proportional to the neutrino flux and $G_{\mathrm{F}}^{2}$.
Neutrino-nucleus elastic scattering is reduced in dense matter because of correlations between ions. The static structure factor for a plasma of electrons and ions is calculated from Monte Carlo simulations and parameterized with a least squares fit. Our results imply a large increase in the neutrino mean free path. This strongly limits the trapping of neutrinos in a supernova by coherent neutral current interactions.
Intensity interferometry is a technique that has been used to measure the size of sources ranging from the quark-gluon plasma formed in heavy ion collisions to the radii of stars. We investigate using the same technique to measure proto-neutron star (PNS) radii with the neutrino signal received from a core-collapse supernovae. Using a full wave-packet analysis, including the neutrino mass for the first time, we derive criteria where the effect can be expected to provide the desired signal, and find that neutrinos from the next Galactic supernova should contain extractable PNS radius informatio…
Axion-Like Particles (ALPs) coupled with electrons would be produced in a Supernova (SN) via electron-proton bremsstrahlung and electron-positron fusion. We evaluate the ALP emissivity from these processes by taking into account the ALP mass and thermal effects on electrons in the strongly degenerate and relativistic SN plasma. Using a state-of-the-art SN simulation, we evaluate the SN 1987A cooling bound on ALPs for masses in the range $1-200$ MeV, which excludes currently unprobed regions down to $g_{ae}\sim 2.5\times 10^{-10}$ at $m_a\sim 120$ MeV.
Unveiling Neutrino Nature with the Diffuse Supernova Background
Università del Salento（萨莱诺大学）；INFN-Istituto Nazionale di Fisica Nucleare, Sezione di Lecce（意大利国家核物理研究所莱切分部）；Niels Bohr International Academy and DARK, Niels Bohr Institute, University of Copenhagen（哥本哈根大学尼尔斯·玻尔研究所及尼尔斯·玻尔国际学院与DARK）
Axion-like particles (ALPs) are a class of hypothetical pseudoscalar particles which feebly interact with ordinary matter. The hot plasma of core-collapse supernovae is a possible laboratory to explore physics beyond the standard model including ALPs. Once produced, some of the ALPs can be absorbed by the supernova matter and affect energy transfer. In this study, we calculate the ALP emission in core-collapse supernovae and the backreaction on supernova dynamics consistently. It is found that the stalled bounce shock can be revived if the coupling between ALPs and photons is as high as g_{ag}…
We propose a possible new mechanism for a strong and stable magnetic field of compact stars due to an instability in the presence of a chirality imbalance of electrons---the chiral plasma instability. A large chirality imbalance of electrons inevitably occurs associated with the parity-violating weak process during core collapse of supernovae. We estimate the maximal magnetic field due to this instability to be of order 10^{18} G at the core. This mechanism naturally generates a large magnetic helicity from the chiral asymmetry, which ensures the stability of the large magnetic field.
Novel neutrino self-interaction can open up viable parameter space for the relic abundance of sterile-neutrino dark matter (S$ν$DM). In this work, we constrain the relic target using core-collapse supernova which features the same fundamental process and a similar environment to the early universe era when S$ν$DM is dominantly produced. We present a detailed calculation of the effects of a massive scalar mediated neutrino self-interaction on the supernova cooling rate, including the derivation of the thermal potential in the presence of non-zero chemical potentials from plasma species. Our res…
