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A. I. Titov

Publications and source records attributed to A. I. Titov.

At least 19 recordsLinked to original sources
arXiv2025

High-resolution luminescence spectroscopy of CaWO$_4$:Ho$^{3+}$: Sensitive detection of internal strains, temperature, and magnetic field

We carried out high-resolution (0.02 cm-1) measurements of the photoluminescence (PL) spectra of CaWO4:Ho3+, including in magnetic field, and performed spectra modeling. Well-resolved hyperfine structure was observed in the luminescence spectra of CaWO4:Ho3+ for the first time. Energies of several crystal-field levels were specified, g-factors were determined. Variations of a magnetic field as small as several tenths of mT can be detected from the PL spectra. We show that the PL spectra are much more sensitive to lattice strains in CaWO4:Ho3+ than the absorption spectra. The spectra were simulated using refined crystal-field parameters and taking into account both hyperfine and deformation interactions. Here, we used the previously obtained distribution function of random strains induced by point lattice defects in an elastically anisotropic CaWO4 crystal. A luminescence thermometer for temperatures around 20 K based on CaWO4:Ho3+ is suggested.

physics.optics↗
arXiv2024

Polarization of recoil photon in non-linear Compton process

The polarization of recoil photon ($γ'$) in the non-linear Compton process $e + \vec L \to \vec γ' +e'$ in the interaction of a relativistic electron with a linearly polarized laser beam ($\vec L$) is studied within the Furry picture in the lowest-order, tree-level S matrix element. In particular, we consider the asymmetry of differential cross sections ${\cal A}$ for two independent axes describing the Compton process equal to the intrinsic spin variable $ξ^f_3$, that determines the polarization properties of $γ'$. The sign and absolute value of the asymmetry determine the direction and degree of $γ'$ polarization. We have analyzed the process in a wide range of laser intensity that covers existing and future experiments. Our results provide additional knowledge for studying nonlinear multi-photon effects in quantum electrodynamics and can be used in planning experiments at envisaged laser facilities.

hep-ph↗
arXiv2021

Positron energy distribution in factorized trident process

We estimate the energy distribution of positrons produced in the interaction of ultra-relativistic electrons with a high-intensity laser beam. The underlying trident process is factorized on the probabilistic level. That is, we deploy a two-step mechanism for the formation of electron-positron pairs. In the first step, a high-energy photon is produced as a result of nonlinear Compton scattering. In the second step, an electron-positron pair is created by the nonlinear (multi-photon) Breit-Wheeler process.

hep-ph↗
arXiv2021

Impact of laser polarization on q-exponential photon tails in non-linear Compton scattering

Non-linear Compton scattering of ultra-relativistic electrons traversing high-intensity laser pulses generates also hard photons. These photon high-energy tails are considered for parameters in reach at the forthcoming experiments LUXE and E-320. We consider the invariant differential cross sections $d σ/ du$ between the IR and UV regions and analyze the impact of the laser polarization and find q-deformed exponential shapes. (The variable $u$ is the light-cone momentum-transfer from initial electron to final photon.) Optical laser pulses of various durations are compared with the monochromatic laser beam model which uncovers the laser intensity parameter in the range $ξ= 1 \cdots 10$. Some supplementary information is provided for the azimuthal final-electron/photon distributions and the photon energy-differential cross sections.

hep-ph↗
arXiv2020

Multi-photon regime of non-linear Breit-Wheeler and Compton processes in short linearly and circularly polarized laser pulses

Non-linear Breit-Wheeler $e^+e^-$ pair production and its crossing channel - the non-linear Compton process - in the multi-photon regime are analyzed for linearly and circularly polarized short laser pulses. The contribution of multi-photon processes to total cross sections is determined and we also show that (i) the azimuthal angular distributions of outgoing electrons in these processes differ on a qualitative level, and (ii) they depend on the polarization properties of the pulses. A finite carrier envelope phase (CEP) leads to a non-trivial non-monotonic behavior of the azimuthal angle distributions of the considered processes. That effect can be used for the CEP determination.

physics.plasm-ph↗
arXiv2018

Non-linear Breit-Wheeler process in short laser double-pulses

The non-linear (strong-field) Breit-Wheeler $e^+e^-$ pair production by a probe photon traversing two consecutive short and ultra short (sub-cycle) laser pulses is considered within a QED framework. The temporal shape of the pulses and the distance between them are essential for the differential cross section as a function of the azimuthal angle distribution of the outgoing electron (positron). The found effect of a pronounced azimuthal anisotropy is important for sub-cycle pulses and decreases rapidly with increasing width of the individual pulses.

physics.plasm-ph↗
arXiv2016

Field induced phase transition in the few photon regime

Some features of the field induced phase transition accompanied by the vacuum creation of an electron-positron plasma (EPP) in strong time-dependent electric fields have been discussed in the work [1] in the domain of the tunneling mechanism ($ω\ll m$, where $ω$ is the characteristic frequency of the external field and $m$ is the electron mass). In the present contribution the features of the this process will be considered in the few photon domain where $ω\sim m$. We observe a narrowing of the transient domain of the fast oscillations and, mainly, a considerable growth of the effectiveness of the EPP production. Under these circumstances, we see an increase of the effectiveness of the EPP creation in the particular case of a bifrequent excitation, where both mechanisms (tunneling and few photon) act simultaneously [2,3].

physics.plasm-ph↗
arXiv2016

Laser assisted Breit-Wheeler and Schwinger processes

The assistance of an intense optical laser pulse on electron-positron pair production by the Breit-Wheeler and Schwinger processes in XFEL fields is analyzed. The impact of a laser beam on high-energy photon collisions with XFEL photons consists in a phase space redistribution of the pairs emerging in the Breit-Wheeler sub-process. We provide numerical examples of the differential cross section for parameters related to the European XFEL. Analogously, the Schwinger type pair production in pulsed fields with oscillating components referring to a superposition of optical laser and XFEL frequencies is evaluated. The residual phase space distribution of created pairs is sensitive to the pulse shape and may differ significantly from transiently achieved mode occupations.

hep-ph↗
arXiv2016

Pair production by Schwinger and Breit-Wheeler processes in bi-frequent fields

Counter-propagating and suitably polarized light (laser) beams can provide conditions for pair production. Here, we consider in more detail the following two situations: (i) In the homogeneity regions of anti-nodes of linearly polarized ultra-high intensity laser beams, the Schwinger process is dynamically assisted by a second high-frequency field, e.g. by a XFEL beam. (ii) A high-energy probe photon beam colliding with a superposition of co-propagating intense laser and XFEL beams gives rise to the laser assisted Breit-Wheeler process. Prospects of such bi-frequent field constellations with respect to the feasibility of conversion of light into matter are discussed.

hep-ph↗
arXiv2015

Spectral caustics in laser assisted Breit-Wheeler process

Electron-positron pair production by the Breit-Wheeler process embedded in a strong laser pulse is analyzed. The transverse momentum spectrum displays prominent peaks which are interpreted as caustics, the positions of which are accessible by the stationary phases. Examples are given for the superposition of an XFEL beam with an optical high-intensity laser beam. Such a configuration is available, e.g., at LCLS at present and at European XFEL in near future. It requires a counter propagating probe photon beam with high energy which can be generated by synchronized inverse Compton backscattering.

physics.plasm-ph↗
arXiv2013

Neutrino nuclear response and photo nuclear reaction

Photo nuclear reactions are shown to be used for studying neutrino/weak nuclear responses involved in astro-neutrino nuclear interactions and double beta decays. Charged current weak responses for ground and excited states are studied by using photo nuclear reactions through isobaric analog states of those states, while neutral current weak responses for excited states are studied by using photo nuclear reactions through the excited states. The weak interaction strengths are studied by measuring the cross sections of the photo nuclear reactions, and the spin and parity of the state are studied by measuring angular correlations of particles emitted from the photo nuclear reactions. Medium-energy polarized photons obtained from laser photons scattered off GeV electrons are very useful. Nuclear responses studied by photo nuclear reactions are used to evaluate neutrino/weak nuclear responses, i.e. nuclear beta and double beta matrix elements and neutrino nuclear interactions, and to verify theoretical calculations for them.

nucl-th↗
arXiv2013

Breit-Wheeler process in very short electromagnetic pulses

The generalized Breit-Wheeler process, i.e. the emission of $e^+e^-$ pairs off a probe photon propagating through a polarized short-pulsed electromagnetic (e.g.\ laser) wave field, is analyzed. We show that the production probability is determined by the interplay of two dynamical effects. The first one is related to the shape and duration of the pulse and the second one is the non-linear dynamics of the interaction of $e^\pm$ with the strong electromagnetic field. The first effect manifests itself most clearly in the weak-field regime, where the small field intensity is compensated by the rapid variation of the electromagnetic field in a limited space-time region, which intensifies the few-photon events and can enhance the production probability by orders of magnitude compared to an infinitely long pulse. Therefore, short pulses may be considered as a powerful amplifier. The non-linear dynamics in the multi-photon Breit-Wheeler regime plays a decisive role at large field intensities, where effects of the pulse shape and duration are less important. In the transition regime, both effects must be taken into account simultaneously. We provide suitable expressions for the $e^+e^-$ production probability for kinematic regions which can be used in transport codes.

hep-ph↗
arXiv2012

Subthreshold pair production in short laser pulses

The $e^+e^-$ pair production by a probe photon traversing a linearly polarized laser pulse is treated as generalized nonlinear Breit-Wheeler process. For short laser pulses with very few oscillations of the electromagnetic field we find below the perturbative weak-field threshold $\sqrt{s} = 2m$ a similar enhancement of the pair production rate as for circular polarization. The strong subthreshold enhancement is traced back to the finite bandwidth of the laser pulse. A folding model is developed which accounts for the interplay of the frequency spectrum and the intensity distribution in the course of the pulse.

hep-ph↗
arXiv2012

Enhanced subthreshold electron-positron production in short laser pulses

The emission of electron-positron pairs off a probe photon propagating through a polarized short-pulsed electromagnetic (e.g.\ laser) wave field is analyzed. A significant increase of the total cross section of pair production in the subthreshold region is found for decreasing laser pulse duration even in case of moderate laser pulse intensities.

hep-ph↗
arXiv2011

Exclusive $\barΞΞ$ and $\barΞ_cΞ_c$ production in $\bar pp$ collisions at $\sqrt{s}\leq 15$ GeV

Estimates of differential cross sections and longitudinal asymmetries are presented for the reactions $\bar pp\to \bar ΞΞ$ and $\bar pp\to \bar Ξ_cΞ_c$ at energies $\sqrt{s}\lesssim 15$ GeV. The $Ξ$ and $Ξ_c$ hyperons are assumed to be produced in two-step processes: first, intermediate $\barΛΛ$ and/or $\barΛ_cΛ_c$ states are created which are converted afterwards into final states $\bar ΞΞ$, $\bar Ξ_cΞ_c$ and $\bar Ξ_cΞ_c$. The full amplitudes are described by loop diagrams within a modified Regge model, based on the topological decomposition of planar quark diagrams. A strong sensitivity of the ratio of yields of $\bar Ξ_cΞ_c$ to $\bar ΞΞ$ and of $\bar Λ_cΛ_c$ to $\bar ΛΛ$ to the degree of SU(4) symmetry violation is found.

hep-ph↗
arXiv2010

Neutrino pair emission off electrons in a strong electromagnetic wave field

The emission of $ν\barν$ pairs off electrons in a polarized ultra-intense electromagnetic (e.g.\ laser) wave field is analyzed. We elaborate on the significance of non-linear electrodynamics effects (i.e., multi-photon processes) and the peculiarities of neutrino production. Special attention is devoted to the convergence of the reaction probabilities as a function of the number of absorbed photons. Expressions for large field intensities are provided. The asymmetry between the probabilities of electron and $μ+τ$ neutrino production depends on initial conditions such as energy of the wave field photons and the field intensity. These findings differ from the lowest order perturbative calculation of the reaction $γ+ e \to e' + ν\bar ν$.

hep-ph↗
arXiv2009

Dimuon production by laser-wakefield accelerated electrons

We analyze $μ^+μ^-$ pair production generated by high-energy electrons emerging from a laser-wakefield accelerator. The $μ^+μ^-$ pairs are created in a solid thick high-$Z$ target, following the electron accelerating plasma region. Numerical estimates are presented for electron beams obtained presently in the LBL TW laser experiment \cite{C2} and possible future developments. Reactions induced by the secondary bremsstrahlung photons dominate the dimuon production. According to our estimates, a 20 pC electron bunch with energy of 1 (10) GeV may create about 200 (6000) muon pairs. The produced $μ^\pm$ can be used in studying various aspects of muon-related physics in table top installations. This may be considered as an important step towards the investigation of more complicated elementary processes induced by laser driven electrons.

physics.acc-ph↗