Separation of pair and single top quark production in tWb-associated final state using a neural network
Separation of pair and single top quark production in tWb-associated final state using a neural network
E. E. Boos, V. E. Bunichev, P. V. Volkov, L. V. Dudko, M. A. Perfilov
The paper presents a method for separating the contribution of pair and single top quark production in tWb-associated final state using a neural network. The proposed method makes possible to calculate such processes in a gauge-invariant way with fully taking into account interference contributions and dividing the phase space into single-resonant and double-resonant regions, which is necessary to increase the accuracy of the search for possible deviations from the predictions of the Standard Model in these processes. To train the neural network, the optimized set of observables is used to separate single-resonance and double-resonance contributions to the overall process. The use of this method allows us to avoid the disadvantages inherent in the schemes used in collider physics for calculating the processes of tWb-associated top quark production with the removal of Feynman diagrams, which leads to violation of gauge invariance, or the addition of a subtraction scheme, which leads to the appearance of negative weights for the part of simulated events. The proposed method can be used to increase the efficiency of searching for deviations from the predictions of the Standard Model in the interaction of the top quark with the W boson and b quark.
Show AbstractThe Guggenheim equation for a system of hard spheres and its generalization
The Guggenheim equation for a system of hard spheres and its generalization
P. N. Nikolaev
In the present work, for the first time, the generalized Guggenheim equation for a system of hard spheres is obtained based on the use of the Euler accelerated convergence method. This equation allows taking into account an arbitrary number of known virial coefficients. For a metastable region, this equation is generalized to the case of taking into account the asymptotic behavior of the free energy at high densities. The resulting expression for the compressibility of the homogeneous phase of a system of hard spheres describes the data of a numerical experiment within their accuracy.
Show AbstractPhysical laboratory for students practical laboratory works of The Imperial Moscow University from the moment of foundation until 1917
Physical laboratory for students practical laboratory works of The Imperial Moscow University from the moment of foundation until 1917
A. A. Yakuta
The present survey, timed to a century and a half anniversary of practical laboratory works in Physics being introduced in the curriculum of The Imperial University of Moscow for the students of the Faculty of Physics, provides a broad coverage of its functioning in the period from 1873 to 1917. The author gives a brief overview of the history of its founding, includes the data concerning the development of its equipment infrastructure, stuffing and figures about the number of students who took physics labs in those years. The contents of practical laboratory works are being analysed. The author vividly shows that professor A.\,P.~Sokolov’s “Guide to exercises in general physics labs of Physical Institute of The Imperial University of Moscow” relies heavily on “Guide to Practical Classes in Physics” by F.~Kohlrausch. The author familiarizes the readers with some historical references, which enable to better enhance the readers’ understanding of the details of practical training of physics students in The Imperial University of Moscow at the end of the 19th and the beginning of the 20th century. The article also contains rare historical pictures, some of which are published for the first time.
Show AbstractReaction-diffusion systems with nonlinear sources of different intensity in the case of a multiple root without quasimonotonicity condition
Reaction-diffusion systems with nonlinear sources of different intensity in the case of a multiple root without quasimonotonicity condition
R. E. Simakov
We consider a boundary value problem for a singularly perturbed system of two second-order ordinary differential equations with different powers of a small parameter at the second derivatives without requiring the right-hand sides to be quasimonotonic. The specific feature of the problem is that one of the two equations in the degenerate system has a double root. It is proved that for sufficiently small values of a small parameter, the problem has a solution of the boundary layer type. A condition is obtained that replaces the quasimonotonicity condition and expands the class of problems to which the results of the work are applicable.
Show AbstractSuppressing even harmonics in free electron lasers by changing the energy spread of the beam
Suppressing even harmonics in free electron lasers by changing the energy spread of the beam
K. /. Zhukovsky
Using an analytical description of the evolution of the power of harmonics in free electron laser (FEL) undulators, we study the effect of electron beam parameters on the main characteristics of FEL radiation: the gain length, spectrum, and harmonic power. The possibility of suppressing even harmonics of the FEL as a light source in the study of materials and surfaces by analyzing the second harmonic nonlinear response (SHG) is being studied. The main factors influencing the radiation of even FEL harmonics are revealed; the influence of the beam cross section and the spread of electron energies on their radiation is analyzed. An example of a LEUTL FEL with visible light emission, which is used in studies of the optical properties of materials and the chemical state of molecules on surfaces and interfaces between media, is considered. In this context, the possibility of suppressing the second FEL harmonic is analyzed.
Show AbstractOn blow-up and on global existence of weak solutions to Cauchy problem for some nonlinear equation of the pseudoparabolic type
On blow-up and on global existence of weak solutions to Cauchy problem for some nonlinear equation of the pseudoparabolic type
I. K. Katasheva, M. O. Korpusov, A. A. Panin
It is a brief exposition of results of the investigation of Cauchy problem for some nonlinear equation of pseudoparabolic type that is a generalisation of some model of semiconductor theory.
Show AbstractExperimental study of the interaction of wind with a wave induced by a wave producer in a direct channel
Experimental study of the interaction of wind with a wave induced by a wave producer in a direct channel
I. N. Ivanova$^{1,2}$, O. N. Melnikova$^2$
An experimental study of the effect of wind blowing a wave induced by a wave generator in a direct channel has been carried out. It is shown that at low wave steepness ak < 0.1 and wind speed W < 2.3 m/s, a drift current occurs on the water surface due to the influence of viscous forces. A formula for calculating its velocity is proposed. It is found that the phase velocity of the wave increases with the appearance of a drift flow and can be calculated using the formula obtained for linear waves on a flow with a constant velocity shift. With an increase in the steepness of the wave ak > 0.19 and an increase in wind W > 2.3 m/s, the formation of a vortex deforming the water surface was detected in the air flow above the top of the wave crest. The vortex destroys the viscous layer, reducing the drift velocity. At the same time, the phase velocity and wavelength decrease. A mechanism explaining this process is proposed.
Show AbstractSeismotectonics of Russian segment of the Arctic
Seismotectonics of Russian segment of the Arctic
E. V. Vioronina
The paper considers the foci of the most severe earthquakes in the Russian segment of the Arctic that occurred during the entire observation period, from 1976 to the present. The stress and strain fields were studied by analyzing the tensor of the seismic moment of registered earthquakes. This analysis is being conducted for the first time. Spatial distributions of the Lode-Nadai coefficient and the rate of seismotectonic deformation are obtained.
Show AbstractElastic neutrino scattering on nucleons and neutrino electromagnetic properties
Elastic neutrino scattering on nucleons and neutrino electromagnetic properties
K. A. Kouzakov$^1$, F. M. Lazarev$^2$, A. I. Studenikin$^2$
We study the electromagnetic contribution to elastic neutrino-nucleon scattering processes. The neutrino electromagnetic charge, magnetic, electric, and anapole form factors of both diagonal and transition types in the mass basis are taken into account in the present formalism. When treating the nucleon electromagnetic vertex, we take into account not only the charge and magnetic form factors of a nucleon, but also its electric and anapole form factors. We examine the effects of the neutrino magnetic moment on elastic neutrino-nucleon scattering and how they can be disentangled from those of the strange form factors contributions to the nucleon’s weak neutral current.
Show AbstractInfluence of the Bound Electron-Hole Pairs Dissociation Probability Field Dependence Form on the Photocurrent and Spatial Resolution of Organic Field Phototransistors
Influence of the Bound Electron-Hole Pairs Dissociation Probability Field Dependence Form on the Photocurrent and Spatial Resolution of Organic Field Phototransistors
V. A. Trukhanov
In this work, numerical simulations are used to study ambipolar organic field-effect phototransistors, in which a spatially localized photoelectric effect can take place. This effect consists in the fact that there is a small spatially localized photosensitive region in the transistor channel, the position of which can be controlled by changing the gate voltage. The purpose of this work is to analyze the relationship between the form of the field dependence of the bound electron-hole pairs (e/h pairs) dissociation probability and characteristics of the studied ambipolar phototransistors such as normalized photocurrent, spatial resolution, and response time. It is shown that the optimal form of the field dependence of e/h pairs dissociation probability is stepwise-like form, which can provide a high spatial resolution at high values of the normalized photocurrent without degrading the response time of the phototransistor. This shape can be achieved when the organic semiconductor has an extremely narrow distribution of e/h pairs by size, described by the delta function.Also, on the example of several distributions of various shapes, it is shown that a decrease in the width of the distribution leads to an increase in the spatial resolution.Approaches to the selection and modification of organic semiconductor materials that would provide the most pronounced spatially localized photoelectric effect in ambipolar field-effect transistors are discussed.
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