arXiv subjects

A. Yu. Smirnov

Publications and source records attributed to A. Yu. Smirnov.

At least 19 recordsLinked to original sources

arXiv2025

Chiral interactions, chiral states and "chiral neutrino oscillations"

In vacuum the ``chiral neutrino oscillations'', i.e. the periodic transitions between the left- and right-handed states do not occur. The produced state differs from the chiral component that appear in the Lagrangian of interactions and should be computed for each specific process. The phase difference between components of a produced neutrino is space-time independent. This neutrino state consists of only positive energy solutions of the Dirac equation and therefore the energy splitting $2E_ν$ between the components with different helicities that would drive the chiral oscillations does not exist. Consideration in terms of neutrino propagators leads to the same conclusion. The situation is similar for the Majorana neutrinos and in the presence of flavor mixing. However, oscillations of the neutrino states produced in the chiral interactions are possible in matter with the length determined by the matter potential. Description of oscillations in terms of amplitudes of production and detection is elaborated that does not lead to any misconception. In the expanding Universe the relic neutrinos adiabatically convert to equal number densities of the left and right handed components.

hep-ph↗

arXiv2017

Solar neutrinos: Oscillations or No-oscillations?

The Nobel prize in physics 2015 has been awarded "... for the discovery of neutrino oscillations which show that neutrinos have mass". While SuperKamiokande (SK), indeed, has discovered oscillations, SNO observed effect of the adiabatic (almost non-oscillatory) flavor conversion of neutrinos in the matter of the Sun. Oscillations are irrelevant for solar neutrinos apart from small $ν_e$ regeneration inside the Earth. Both oscillations and adiabatic conversion do not imply masses uniquely and further studies were required to show that non-zero neutrino masses are behind the SNO results. Phenomena of oscillations (phase effect) and adiabatic conversion (the MSW effect driven by the change of mixing in matter) are described in pedagogical way.

hep-ph↗

arXiv2017

Attenuation effect and neutrino oscillation tomography

Attenuation effect is the effect of weakening of contributions to the oscillation signal from remote structures of matter density profile. The effect is a consequence of integration over the neutrino energy within the energy resolution interval. Structures of a density profile situated at distances larger than the attenuation length, $λ_{att}$, are not "seen". We show that the origins of attenuation are (i) averaging of oscillations in certain layer(s) of matter, (ii) smallness of matter effect: $ε\equiv 2EV/Δm^2 \ll 1$, where $V$ is the matter potential, and (iii) specific initial and final states on neutrinos. We elaborate on the graphic description of the attenuation which allows us to compute explicitly the effects in the $ε^2$ order for various density profiles and oscillation channels. The attenuation in the case of partial averaging is described. The effect is crucial for interpretation of oscillation data and for the oscillation tomography of the Earth with low energy (solar, supernova, atmospheric, {\it etc.}) neutrinos.

hep-ph↗

arXiv2015

Lepton mixing from the hidden sector

Experimental results indicate a possible relation between the lepton and quark mixing matrices of the form U_PMNS \approx V_CKM^\dagger U_X, where U_X is a matrix with special structure related to the mechanism of neutrino mass generation. We propose a framework which can realize such a relation. The main ingredients of the framework are the double seesaw mechanism, SO(10) Grand Unification and a hidden sector of theory. The latter is composed of singlets (fermions and bosons) of the GUT symmetry with masses between the GUT and Planck scale. The interactions in this sector obey certain symmetries G_hidden. We explore the conditions under which symmetries G_hidden can produce flavour structures in the visible sector. Here the key elements are the basis-fixing symmetry and mediators which communicate information about properties of the hidden sector to the visible one. The interplay of SO(10) symmetry, basis-fixing symmetry identified as Z2 x Z2 and G_hidden can lead to the required form of U_X. A different kind of new physics is responsible for generation of the CKM mixing. We present the simplest realizations of the framework which differ by nature of the mediators and by symmetries of the hidden sector.

hep-ph↗

arXiv2015

Super-PINGU for measurement of the leptonic CP-phase with atmospheric neutrinos

We explore a possibility to measure the CP-violating phase $δ$ using multi-megaton scale ice or water Cherenkov detectors with low, $(0.2 - 1)$ GeV, energy threshold assuming that the neutrino mass hierarchy is identified. We elaborate the relevant theoretical and phenomenological aspects of this possibility. The distributions of the $ν_μ$ (track) and $ν_e$ (cascade) events in the neutrino energy and zenith angle $(E_ν- θ_z)$ plane have been computed for different values of $δ$. We study properties and distinguishability of the distributions before and after smearing over the neutrino energy and zenith angle. The CP-violation effects are not washed out by smearing, and furthermore, the sensitivity to $δ$ increases with decrease of the energy threshold. The $ν_e$ events contribute to the CP-sensitivity as much as the $ν_μ$ events. While sensitivity of PINGU to $δ$ is low, we find that future possible upgrade, Super-PINGU, with few megaton effective volume at ($0.5 - 1$) GeV and e.g. after 4 years of exposure will be able to disentangle values of $δ= π/2,~ π,~ 3π/2$ from $δ= 0$ with "distinguishability" ($\sim$ significance in $σ$'s) $S_σ^{tot} = (3 - 8),~ (6 - 14),~(3 - 8)$ correspondingly. Here the intervals of $S_σ^{tot}$ are due to various uncertainties of detection of the low energy events, especially the flavor identification, systematics, {\it etc.} Super-PINGU can be used simultaneously for the proton decay searches.

hep-ph↗

arXiv2015

Oscillations of the $^7$Be solar neutrinos inside the Earth

We explore in detail oscillations of the solar $^7$Be neutrinos in the matter of the Earth. The depth of oscillations is about $(0.1 - 0.2)\%$ and the length $\approx 30$ km. The period of the oscillatory modulations in the energy scale is comparable with the width of the line determined by the temperature in the center of the Sun. The latter means that depending on the length of trajectory (nadir angle) one obtains different degree of averaging of oscillations. Exploring these oscillations it is possible to measure the width of the $^7$Be line and therefore the temperature of the Sun, determine precisely $Δm^2_{21}$, perform tomography of the Earth, in particular, measure the deviation of its form from sphere, and detect small structures. Studies of the Be neutrinos open up a possibility to test quantum mechanics of neutrino oscillations and search for the sterile neutrinos. Accuracy of these measurements with future scintillator (or scintillator uploaded) detectors of the $\sim 100$ kton mass scale is estimated.

hep-ph↗

arXiv2015

Riddle of the Neutrino Mass

We discuss some known approaches and results as well as few new ideas concerning origins and nature of neutrino mass. The key issues include (i) connections of neutrino and charged fermions masses, relation between masses and mixing, energy scale of new physics behind neutrino mass where possibilities spread from the Planck and GUT masses down to a sub-eV scale. The data hint two different new physics involved in generation of neutrino mass. Determination of the CP phase as well as mass hierarchy can play important role in identification of new physics. It may happen that sterile neutrinos provide the key to resolve the riddle.

hep-ph↗

arXiv2015

Super-PINGU for measuring CP violation

We propose to measure leptonic CP phase, after neutrino mass hierarchy is established, with an upgrade of the PINGU detector and using atmospheric neutrino flux. The upgrade, called super-PINGU, will require a few megaton effective volume at 0.5-1 GeV range to distinguish $δ$ in the range $π/2$-$3π/2$ from 0 after 4 years of operation. The distinguishability (similar to significance) of measuring $δ$ depends crucially on various flux, cross-section, event reconstruction (energy and angle) and flavor identification uncertainties. We explore effects of these uncertainties on the distinguishability of measuring CP phase and suggest possible ways to minimize their impact.

hep-ph↗

arXiv2014

Entanglement in a quantum annealing processor

Entanglement lies at the core of quantum algorithms designed to solve problems that are intractable by classical approaches. One such algorithm, quantum annealing (QA), provides a promising path to a practical quantum processor. We have built a series of scalable QA processors consisting of networks of manufactured interacting spins (qubits). Here, we use qubit tunneling spectroscopy to measure the energy eigenspectrum of two- and eight-qubit systems within one such processor, demonstrating quantum coherence in these systems. We present experimental evidence that, during a critical portion of QA, the qubits become entangled and that entanglement persists even as these systems reach equilibrium with a thermal environment. Our results provide an encouraging sign that QA is a viable technology for large-scale quantum computing.

quant-ph↗

arXiv2013

Relating neutrino masses and mixings by discrete symmetries

Lepton mixing can originate from the breaking of a flavor symmetry in different ways in the neutrino and the charged lepton sector. We propose an extension of this framework which allows to connect the mixing parameters with masses, and more precisely, with certain types of degeneracy of the neutrino mass spectrum. We obtain relations between the mixing parameters for the cases of partial degeneracy, m1 = m2, and complete degeneracy, m1 = m2 = m3. These relations determine also the Majorana phases. It is shown that relatively small corrections to these lowest order results can produce the required mass splitting and modify the mixing without significant changes of the other symmetry results.

hep-ph↗

arXiv2013

Hypermagnetic helicity evolution in early universe: leptogenesis and hypermagnetic diffusion

We study hypermagnetic helicity and lepton asymmetry evolution in plasma of the early Universe before the electroweak phase transition (EWPT) accounting for chirality flip processes via inverse Higgs decays and sphaleron transitions which violate the left lepton number and wash out the baryon asymmetry of the Universe (BAU). In the scenario where the right electron asymmetry supports the BAU alone through the conservation law $B/3 - L_{eR}=const$ at temperatures $T>T_{RL}\simeq 10 TeV$ the following universe cooling leads to the production of a non-zero left lepton (electrons and neutrinos) asymmetry. This is due to the Higgs decays becoming more faster when entering the equilibrium at $T=T_{RL}$ with the universe expansion, $Γ_{RL}\sim T> H\sim T^2$, resulting in the parallel evolution of both the right and the left electron asymmetries at $T<T_{RL}$ through the corresponding Abelian anomalies in SM in the presence of a seed hypermagnetic field. The hypermagnetic helicity evolution proceeds in a self-consistent way with the lepton asymmetry growth. The role of sphaleron transitions decreasing the left lepton number turns out to be negligible in given scenario. The hypermagnetic helicity can be a supply for the magnetic one in Higgs phase assuming a strong seed hypermagnetic field in symmetric phase.

astro-ph.CO↗

arXiv2013

Ground-state entanglement in coupled qubits

We study a system of qubits that are coupled to each other via only one degree of freedom represented, e.g., by $σ_z$-operators. We prove that, if by changing the Hamiltonian parameters, a non-degenerate ground state of the system is continuously transformed in such a way that the expectation values of $σ_z$ operators of at least two coupled qubits change, this ground state is entangled. Using this proof, we discuss connection between energy level anticrossings and ground state entanglement. Following the same line of thought, we introduce entanglement witnesses, based on cross-susceptibilities, that can detect ground state entanglement for any bipartition of the multi-qubit system. A witness for global ground state entanglement is also introduced.

quant-ph↗

arXiv2013

Mass hierarchy, 2-3 mixing and CP-phase with Huge Atmospheric Neutrino Detectors

We explore the physics potential of multi-megaton scale ice or water Cherenkov detectors with low ($\sim 1$ GeV) threshold. Using some proposed characteristics of the PINGU detector setup we compute the distributions of events versus neutrino energy $E_ν$ and zenith angle $θ_z$, and study their dependence on yet unknown neutrino parameters. The $(E_ν- θ_z)$ regions are identified where the distributions have the highest sensitivity to the neutrino mass hierarchy, to the deviation of the 2-3 mixing from the maximal one and to the CP-phase. We evaluate significance of the measurements of the neutrino parameters and explore dependence of this significance on the accuracy of reconstruction of the neutrino energy and direction. The effect of degeneracy of the parameters on the sensitivities is also discussed. We estimate the characteristics of future detectors (energy and angle resolution, volume, etc.) required for establishing the neutrino mass hierarchy with high confidence level. We find that the hierarchy can be identified at $3σ$ -- $10σ$ level (depending on the reconstruction accuracies) after 5 years of PINGU operation.

hep-ph↗

arXiv2013

Tunneling spectroscopy using a probe qubit

We describe a quantum tunneling spectroscopy technique that requires only low bandwidth control. The method involves coupling a probe qubit to the system under study to create a localized probe state. The energy of the probe state is then scanned with respect to the unperturbed energy levels of the probed system. Incoherent tunneling transitions that flip the state of the probe qubit occur when the energy bias of the probe is close to an eigenenergy of the probed system. Monitoring these transitions allows the reconstruction of the probed system eigenspectrum. We demonstrate this method on an rf SQUID flux qubit.

cond-mat.supr-con↗

arXiv2012

Discrete symmetries and model-independent patterns of lepton mixing

In the context of discrete flavor symmetries, we elaborate a method that allows one to obtain relations between the mixing parameters in a model-independent way. Under very general conditions, we show that flavor groups of the von Dyck type, that are not necessarily finite, determine the absolute values of the entries of one column of the mixing matrix. We apply our formalism to finite subgroups of the infinite von Dyck groups, such as the modular groups, and find cases that yield an excellent agreement with the best fit values for the mixing angles. We explore the Klein group as the residual symmetry of the neutrino sector and explain the permutation property that appears between the elements of the mixing matrix in this case.

hep-ph↗

arXiv2012

Neutrino 2012: Outlook - theory

Ongoing developments in theory and phenomenology are related to the measured large value of 1-3 mixing and indications of significant deviation of the 2-3 mixing from maximal one. "Race" for the mass hierarchy has started and there is good chance that multi-megaton scale atmospheric neutrino detectors with low threshold (e.g. PINGU) will establish the type of hierarchy. Two IceCube candidates of the PeV cosmic neutrinos if confirmed, is the beginning of new era of high energy neutrino astronomy. Accumulation of data on solar neutrinos (energy spectrum, D-N asymmetry, value of $Δm^2_{21}$) may uncover some new physics. The Tri-bimaximal mixing is disfavored and the existing discrete symmetry paradigm may change. The confirmed QLC prediction, $θ_{13} \approx θ_{C}/\sqrt{2}$, testifies for GUT, seesaw and some symmetry at very high scales. However, the same value of 1-3 mixing can be obtained in various ways which have different implications. The situation in lepton sector changes from special (with specific neutrino symmetries, etc.) to normal, closer to that in the quark sector. Sterile neutrinos are challenge for neutrino physics but also opportunity with many interesting phenomenological consequences. Further studies of possible connections between neutrinos and the dark sector of the Universe may lead to breakthrough both in particle physics and cosmology.

hep-ph↗

arXiv2012

Neutrino Velocity and Neutrino Oscillations

We study distances of propagation and the group velocities of the muon neutrinos in the presence of mixing and oscillations assuming that Lorentz invariance holds. Oscillations lead to distortion of the $ν_μ$ wave packet which, in turn, changes the group velocity and the distance $ν_μ$ travels. We find that the change of the distance, $d_{osc}$, is proportional to the length of the wave packet, $σ_x$, and the oscillation phase, $ϕ_p$, acquired by neutrinos in the $π-$ and $K-$ meson decay tunnel where neutrino wave packet is formed: $d_{osc} \propto σϕ_p$. Although the distance $d_{osc}$ may effectively correspond to the superluminal motion, the effect is too tiny ($\sim 10^{- 5}$ cm) to be reconciled with the OPERA result. We analyze various possibilities to increase $d_{osc}$ and discuss experimental setups in which $d_{osc}$ (corresponding to the superluminal motion) can reach an observable value $\sim 1$ m.

hep-ph↗

arXiv2012

Lepton mixing and discrete symmetries

The pattern of lepton mixing can emerge from breaking a flavor symmetry in different ways in the neutrino and charged lepton Yukawa sectors. In this framework, we derive the conditions imposed on the mixing matrix by the structure of discrete groups of the von Dyck type which include A4, S4 and A5. We show that, in general, these conditions reduce to two equations for the mixing parameters (angles and CP phase δ). These constraints, which correspond to unbroken residual symmetries, are consistent with non-zero 13 mixing and deviations from maximal 2-3 mixing. For the allowed values of mixing angles we predict δ= 60 - 90^{\circ}.

hep-ph↗