A. V. Kuznetsov, N. V. Mikheev
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.
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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 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 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 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 washi…
We calculate the production of large mass dileptons from the passage of jets passing through the quark-gluon plasma. Using the relativistic kinetic theory, we rigorously derive the production rate for the jet-dilepton conversion in the hot medium. The jet-dilepton conversion is compared with the thermal dilepton emission and the Drell-Yan process. The contribution of the jet-dilepton conversion is not prominent for all values of the invariant mass $M$, and the Drell-Yan process is found to dominate over the thermal dilepton emission and the jet-dilepton conversion for $M>$2.5 GeV at RHIC. The …
We calculate the yield of lepton pair production from jet-plasma interaction where the plasma is anisotropic in momentum space. We compare both the $M$ and $p_T$ distributions from such process with the Drell-Yan contribution. It is observed that the invariant mass distribution of lepton pair from such process dominate over the Drell-Yan up to $3$ GeV at RHIC and up to $10$ GeV at LHC. Moreover, it is found that the contribution from anistropic quark gluon plasma (AQGP) increases marginally compared to the isotropic QGP. In case of $p_T$-distribution we observe an increase by a factor of $3-4$…
We study the effects of neutrino spin-flip in the magnetic field, B_{AGN}, of active galactic nuclei (AGN) for high-energy neutrinos (E > 10^{6} GeV) originating from AGN induced by an interplay of the violation of equivalence principle parameterized by $Δf$ and the twist in B_{AGN}. We point out that a conversion effect may exist for $Δf \sim 10^{-34} (δm^{2}/10^{-5} eV^{2})$ independent of gravity mixing angle. Observational consequences for this conversion effect are discussed.
We discuss the excitation of sterile neutrinos in the early universe using general quantum kinetic equations, which also incorporate a possible primordial magnetic field $B$. We find a new contribution to the excitation propability, which has its origin in the shrinkage of the spin vector. In the absence of $B$ nucleosynthesis implies the constraint $\mid Δm^2\mid\sin^22θ_0\lsim 1.6\times 10^{-6}~{\rm eV}^2$ which is more restrictive than previous estimates. We also present examples of possible stringent limits for $B\ne 0$.
Using a real-time formalism of equilibrium and nonequilibrium quantum-field theory, we derive the reaction-rate formula for neutrino-conversion ($ν\to ν'$) process and $ν\barν'$ annihilation process, which take place in a hot and dense QED plasma with background (anti)neutrinos out of equilibrium. Also derived is the formula for the inverse processes to the above ones. Using the hard-thermal-loop resummation scheme, we include the contribution from the coherent processes. The decay/production of a neutrino causes an evolution of its spatial distribution. A scheme for dealing with this evolutio…
If massive neutrinos possess magnetic moments, a magnetic field can cause a spin flip. In the case of Dirac neutrinos the spin flip converts an active neutrino into a sterile one and vice versa. By contrast, if neutrinos are Majorana particles, a spin flip converts them to a neutrino of a different flavor. We examine the behavior of neutrinos in a random magnetic field as it occurs, for instance, in certain astronomical objects, such as an active galactic nucleus. Both Dirac and Majorana neutrinos behave ergodically: independently of their initial density matrix, they tend towards an equiparti…
On the applicability of the Landau-Zener formula to axion-photon conversion
本文研究Landau-Zener公式在轴子-光子共振转换中的适用条件，推导了边界位于非均匀性尺度附近的广义LZ公式，揭示了振荡范围小于共振区域时公式失效及绝热极限下转换概率非最大的问题，并提出了互补适用范围的半经典近似方法。
Neutrino flavor conversion is assumed to be induced by right-handed neutrino flavor conversion via seesaw mechanism. Neutrino oscillation is the macroscopic phenomenon before all neutrino flavor-flip interactions reaching equilibrium. The model for the hypothesis is the extension by introducing large mass Majorana right-handed neutrino into the Standard Model and exerting horizontal symmetry only on the right-handed neutrino sector.
We calculate the production of large mass dileptons from the jet-dilepton conversion in the expanding quark-gluon plasma at Relativistic Heavy Ion Collider (RHIC) and Large Hadron Collider (LHC) energies. The jet-dilepton conversion exceeds the thermal dilepton production and Drell-Yan process in the large mass region of 3.9 GeV$<M<$5.8 GeV and 6.3 GeV$<M<$8.7 GeV in central Pb+Pb collisions at $\sqrt{s_{NN}}$=2.76 TeV and 5.5 TeV, respectively. We present the numerical solution of ideal fluid hydrodynamics. We find that the transverse flow leads to a rapid cooling of the fire ball. The suppre…
We consider active-sterile neutrino conversions in the early universe hot plasma in the presence of a random magnetic field generated at the electroweak phase transition. Within a random field domain the magnetization asymmetry of the lepton antilepton plasma produced by a uniform constant magnetic field is huge in contrast to their small density asymmetry, leading to a drastic change in the active-sterile conversion rates. Assuming that the random field provides the seed for the galactic field one can estimate the restrictions from primordial nucleosynthesis. Requiring that the extra sterile …
Loop quantum gravity theory incorporates a new scale length ${\cal L}$ which induces a Lorentz invariance breakdown. This scale can be either an universal constant or can be fixed by the momentum of particles (${\cal L}\sim p^{-1}$). Effects of the scale parameter ${\cal L}$ and helicity terms occurring in the dispersion relation of fermions are reviewed in the framework of spin-flip conversion of neutrino flavors.
No cosmological constraints on dark photon dark matter from resonant conversion: Impact of nonlinear plasma dynamics
该研究通过粒子网格模拟证明，早期宇宙中暗光子共振转换为朗缪尔波会因等离子体非线性而饱和，从而否定了相关暗光子暗物质约束，使其减弱3000至10^7倍。
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 …
Axion dark matter can resonantly convert to photons in the magnetosphere of neutron stars, possibly giving rise to radio signals observable on Earth. This method for the indirect detection of axion dark matter has recently received significant attention in the literature. The calculation of the radio signal is complicated by a number of effects; most importantly, the gravitational infall of the axions onto the neutron star accelerates them to semi-relativistic speed, and the neutron star magnetosphere is highly anisotropic. Both of these factors complicate the calculation of the conversion of …
Recently Csaki, Kaloper and Terning (hep-ph/0111311) suggested that the observed dimming of distant type Ia supernovae may be a consequence of mixing of the photons with very light axions. We point out that the effect of the plasma, in which the photons are propagating, must be taken into account. This effect changes the oscillation probability and renders the dimming frequency-dependent, contrary to observations. One may hope to accommodate the data by averaging the oscillations over many different coherence domains. We estimate the effect of coherence loss, either due to the inhomogeneities …
Axion-Photon Conversion in 3D Media and Astrophysical Plasmas
本文推导了磁化等离子体中轴子-光子转换的输运方程，完整描述三维介质中光子产生与传播，无发散且包含折射，为轴子暗物质间接探测提供关键计算基础。
The most promising indirect search for the existence of axion dark matter uses radio telescopes to look for narrow spectral lines generated from the resonant conversion of axions in the magnetospheres of neutron stars. Unfortunately, a large list of theoretical uncertainties has prevented this search strategy from being fully accepted as robust. In this work we attempt to address major outstanding questions related to the role and impact of the plasma, including: $(i)$ does refraction and reflection of radio photons in the magnetosphere induce strong inhomogeneities in the flux, $(ii)$ can ref…
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 $μ_ν< (0.1-0.4)\times 10^{-11}μ_B$
Plasma instability splits axion-photon conversion lines
本文研究轴子-光子转换在等离子体不稳定性下由单线分裂为多线，并指出蟹状星云脉冲星信号与此特征有定性相似但非证据。
We calculate the $p_T$ distributions of jet conversion photons from {\em Quark Gluon Plasma} with pre-equilibrium momentum-space anisotropy. A phenomenological model has been used for the time evolution of hard momentum scale $p_{\rm hard}(τ)$ and anisotropy parameter $ξ(τ)$. As a result of pre-equilibrium momentum-space anisotropy, we find significant modification of the jet conversion photon $p_T$ distribution. For example, with {\em fixed initial condition} (FIC) pre-equilibrium anisotropy, we predict significant enhancement of the jet-photon $p_T$ distribution in the entire region, whereas…
We propose a new strategy to search for dark matter axions using tunable cryogenic plasmas. Unlike current experiments, which repair the mismatch between axion and photon masses by breaking translational invariance (cavity and dielectric haloscopes), a plasma haloscope enables resonant conversion by matching the axion mass to a plasma frequency. A key advantage is that the plasma frequency is unrelated to the physical size of the device, allowing large conversion volumes. We identify wire metamaterials as a promising candidate plasma, wherein the plasma frequency can be tuned by varying the in…
We show that axion dark matter (DM) may be detectable through narrow radio lines emitted from neutron stars. The neutron star magnetosphere hosts a strong magnetic field and a plasma frequency that increases towards the neutron star surface. As the axions pass through the magnetosphere, they can resonantly convert into radio photons in a narrow region around the radius at which the plasma frequency equals the axion mass. The bandwidth of the signal is set by the small DM velocity dispersion far away from the neutron star. We solve the axion-photon mixing equations, including a full treatment o…
Photon conversion to axions and dark photons in magnetized plasmas: a finite-temperature field theory approach
本文提出有限温度场论框架，通过 $3\ imes3$ 混合矩阵描述磁化各向异性等离子体中光子与轴子、暗光子的模式耦合，并给出长波极限下响应张量推导及简正模式解析近似，为系统研究等离子体各向异性对 BSM 粒子产生的影响奠定基础。
Collective flavor conversion in dense neutrino plasmas
本文综述致密瞬变源中中微子等离子体的集体味转换，提出 flavomons 准粒子描述，并联系数值模拟进展，解释味不稳定性机制。
Axion-photon conversion down to the nonrelativistic regime
本研究突破轴子-光子转化研究的相对论近似限制，给出任意轴子能量下的精确解析解及微扰展开方法，并推导了适用于中子星磁层暗物质轴子转化的共振简化公式。
We present an extension to next-to-leading order in the strong coupling constant $g$ of the AMY effective kinetic approach to the energy loss of high momentum particles in the quark-gluon plasma. At leading order, the transport of jet-like particles is determined by elastic scattering with the thermal constituents, and by inelastic collinear splittings induced by the medium. We reorganize this description into collinear splittings, high-momentum-transfer scatterings, drag and diffusion, and particle conversions (momentum-preserving identity-changing processes). We show that this reorganized de…
Phenomenology of ultralight bosons around compact objects: in-medium suppression
本文研究等离子体介质对超轻玻色子与光子转换的抑制效应，发现高密度等离子体可显著降低甚至完全抑制转换率，并探讨其对黑洞超辐射和观测信号的影响。
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