Study of the event classification in liquid noble gas detectors is presented. The discrimination between different events usually done by prompt light fraction. To tackle this task we adopt the ...neural net classifier and use pulse shape as an input feature. The main difficulty comes from low-energy events that are difficult to separate. This is important because these events provide a background for dark matter searches. We find that neural networks are suitable for this task.
Abstract
Neural networks are currently used in various fields of science and technology, as well as in experiments related to particle physics. DarkSide-50 is a two-phase (liquid and gas) argon TPC ...which has two main signals: scintillation in LAr (S
1
signal) and electroluminescence in GAr (S
2
signal) 1. In the low-mass dark matter search only the more energetic second signal is used for position reconstruction 2. As a result only events detected by seven central photomultiplier tubes are used for the analysis. Here we attempt to improve reconstruction using the convolutional neural networks (CNN).
Machine learning (ML) has been widely applied in high energy physics to help the physical community in particle classification and data analysis. Here we describe the application of machine learning ...to solve the problem of classifying background and signal events for the DEAP-3600 dark matter search experiment (SNOLAB, Canada). We apply Boosted Decision Trees (BDT) algorithm of ML with improvements from Extra Trees and eXtra Gradient Boosting (XGBoost) methods 1, 2.
Origin of baryon asymmetry is studied in the framework of extra dimensional approach. Baryon excess production and the symmetrization of extra-space are performed simultaneously. Baryon number is ...conserved long after the inflationary stage when the U(1) symmetry is achieved.
A model describing the formation of protogalaxies is developed. Compact supermassive clusters of primordial black holes assumed to act as a nuclei for the galaxy formation. The mechanism of PBH ...formation based on a collapse of massive walls of scalar field due to second order phase transition. Mass spectra of PBH are obtained analytically and shown possibility of the formation of PBH clusters with a total mass of ∼ 105 - 108 M⊙, having a size of ∼ 10 parsec, in an amount of ∼ 1011, which corresponds to observational data on the value of galaxies on the visible Universe. The primary fractal structure of galaxies is naturally explained through the mechanism. Proposed approach is the cornerstone for a principally new scenario of the galaxy formation in the early Universe.
Highly sensitive microvolumometry at 323 K is used in combination with kinetic modeling to measure the rate constants (
k
4
) and kinetic coefficients of inhibition (
f
kin
) of the reaction of ...1,4-substituted butadiene oxidation by hydroperoxyl radicals (
) in the presence of antioxidants (InH): 1,4-hydroquinone and 1,4-benzoquinone. The cyclic mechanism of interaction between
and InH is confirmed: it leads to multiple chain termination, as is demonstrated by the observed long-term inhibition of the oxidation of substrates by hydroquinone and benzoquinone, and the obtained
f
kin
> 10
2
. It is shown that the drop in the value of
k
4
upon replacing –C
6
H
5
substituent at the double bond in 1,4-substituted butadiene with –COOCH
3
is due to the influence of specific solvation.
The rate constants and kinetic coefficients of inhibition (
f
kin
) for olefins oxidized with the transition metal compounds (M
n
) were measured by highly sensitive microvolumometry at 323 K in ...combination with kinetic modeling. The cyclic mechanism of the reactions of hydroxyl radicals with M
n
leading to the multiple chain termination was confirmed as indicated by the observed effect of long-term inhibition of the oxidation of the substrates with M
n
and obtained values of
f
kin
> 10
2
.
ABSTRACT
A combination of microcalorimetry, the rotating sector method, and ESR at 323 K in the environment of 10 solvents of different polarities was used to measure rate constants of addition of ...hydroperoxide radicals ( HO 2•) to π bonds of trans‐1,2‐diphenylethylene and trans,trans‐1,4‐diphenylbutadiene‐1,3 (k2) and disproportionation rate constants of these radicals (k3). With increasing dielectric constant of the medium, k2 values increase from 69 to 410 M−1 · s−1, and k3 values almost do not change and are in the range of (1.0 ± 0.2) × 108 M−1 · s−1. A linear dependence of logarithm values of rate constants from the dielectric constant of the medium in the coordinates of the Kirkwood–Onsager equation was found that allows to make a conclusion about the effect of nonspecific solvation in the studied systems. The quantum‐chemical analysis (NWChem, DFT B3LYP/6‐311G**) of the detailed mechanism for HO 2• addition shows that the influence of the medium polarity reflects the superposition of the effects of nonspecific and specific solvation. The scale of the polar effect will depend on how different solvation energies of the transition and the initial reaction complexes. If a value of the solvation energy of the transition complex is larger than the solvation energy of the initial reaction complex, then the reaction rate should increase with an increase of the solvent's polarity and decrease otherwise.
ABSTRACT
A combination of microvolumetry, the rotating sector method, ESR, 1H NMR, and IR allowed to establish a detailed mechanism of liquid‐phase oxidation of vinyl compounds X1CH=CHX2 and ...X1CH=CH–CH=CHX2 (X1 and X2—a polar substitute: С6Н5–, CO–, СOO–) initiated by azobisisobutyronitrile. A distinctive feature of the mechanism is the fact that the oxidation chain is carried out by a low‐molecular hydroperoxide radical joining the π‐bond. For nine compounds in the temperature range of 303–353 K, relative chain propagation and termination rate constants were measured (k2•k3−0.5). Absolute values of k2 were obtained for diphenylethylene (110 L·mol−1·s−1), ethyl ether of trans‐phenyl‐pentadiene acid (13 L·mol−1·s−1), and methyl ether of trans‐phenyl‐pentadiene acid (14.2 L·mol−1·s−1) at T = 323 K. For the same conditions, 10−8k3 were calculated for diphenylethylene (0.87 L·mol−1·s−1) and methyl ether of trans‐phenyl‐pentadiene acid (1.21 L·mol−1·s−1).
A cyclic mechanism of the oxidation chain termination on introduced antioxidants (stable nitroxyl radicals of the piperidine series (>NO●) and the transition metal compounds (Men)) was established. The inhibition factor (f) showing how many reaction chains are terminated by the one particle of the antioxidant is equal to 102. The cyclic chain termination is caused by the following reactions: HO2● + >NO● → NOH + O2, HO2● + NOH → >NO● + H2O2 (for >NO●) and HO2● + Men → Men+1 + HO2●−, HO2● + Men+1 → Men + H+ + O2 (for Men).
Cosmological implications of Higgs field fluctuations during inflation are considered. This study is based on the Standard Model and the standard quadratic model of chaotic inflation where the Higgs ...field is minimally coupled to gravity and has no direct coupling to the inflaton. In the Standard model the renormalisation group improved effective potential develops an instability (an additional minimum and maximum) at large field values. It is shown that such a new maximum should take place at an energy scale above 1014GeV, otherwise a universe like ours is extremely unlikely. The extension to the case of the Higgs field interacting with the inflaton field is discussed.
The discovery of the Higgs boson and measurements of its mass play an important role in our understanding of the early universe. They indicate that the Higgs potential becomes unstable at large energy scale and this instability is cosmologically relevant. Large quantum fluctuations during inflation could result in a universe landed in wrong vacuum. In this paper it is shown that depending on the instability scale the fate of the universe could be drastically different.
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