arXiv subjects

V. Uvarov

Publications and source records attributed to V. Uvarov.

8 recordsLinked to original sources

arXiv2019

Segmentation Criteria in the Problem of Porosity Determination based on CT Scans

Porous materials are widely used in different applications, in particular they are used to create various filters. Their quality depends on parameters that characterize the internal structure such as porosity, permeability and so on. Computed tomography (CT) allows one to see the internal structure of a porous object without destroying it. The result of tomography is a gray image. To evaluate the desired parameters, the image should be segmented. Traditional intensity threshold approaches did not reliably produce correct results due to limitations with CT images quality. Errors in the evaluation of characteristics of porous materials based on segmented images can lead to the incorrect estimation of their quality and consequently to the impossibility of exploitation, financial losses and even to accidents. It is difficult to perform correctly segmentation due to the strong difference in voxel intensities of the reconstructed object and the presence of noise. Image filtering as a preprocessing procedure is used to improve the quality of segmentation. Nevertheless, there is a problem of choosing an optimal filter. In this work, a method for selecting an optimal filter based on attributive indicator of porous objects (should be free from 'levitating stones' inside of pores) is proposed. In this paper, we use real data where beam hardening artifacts are removed, which allows us to focus on the noise reduction process

cs.CV↗

arXiv2010

Observation of the destructive interference in the radiative kaon decay K- --> mu-nugamma

Using data collected with the ISTRA+ spectrometer at U70 proton synchrotron of IHEP, we report the first measurement of the destructive interference in the radiative kaon cecay K- -->mu-nugamma. We find the difference of the vector and axial form factors Fv-Fa=0.126+/-0.027+/-0.043. The measured value is two standard deviations above the O(p**4) ChPT prediction equal to 0.055. Inclusion of exotic tensor interaction gives Fv-Fa=0.144+/-0.044+/-0.035 and Ft=-0.0079+/-0.0113+/-0.0073, i.e. -0.03<Ft<0.01 at 90% CL,consistent both with zero and with recent theoretical prediction equal to |Ft|=0.022.

hep-ex↗

arXiv2005

Observation of the radiative kaon decay K- --> mu-pi0gammanu

Using data collected with the ISTRA+ spectrometer during the 2001 run of the U-70 proton synchrotron in Protvino, we report the first observation of the radiative kaon decay K- -->mu-pi0gammanu. We find Br(Kmu3g)/Br(Kmu3) for two regions 5<Eg<30 and 30<Eg<60 MeV consistent with theoretical predictions. The measured angular distribution asymmetry for the first region, 0.093+/-0.141, is two standard deviations away from the theoretical prediction of 0.354. The measured asymmetry in the T-odd variable is -0.03+/-0.13.

hep-ex↗

arXiv2004

Search for light pseudoscalar sgoldstino in K- decays

A search for the light pseudoscalar sgoldstino production in the three body K- decay K-->pipi0P has been performed with the ISTRA+ detector exposed to the 25 GeV negative secondary beam of the U70 proton synchrotron. No signal is seen. An upper limit for the branching ratio Br(K->pipi0P), at 90% confidence level, is found to be around 9*10**-6 in the effective mass m(P) range from 0 till 200 MeV, excluding the region near m(pi0) where it degrades to 3.5*10**-5.

hep-ex↗

arXiv2001

Determination of the strangeness contents of light-flavour isoscalars from its production rates in hadronic Z decays measured at LEP

A new phenomenological approach is suggested to determine the strangeness contents of light-flavour isoscalars. This approach is based on phenomenological laws of hadron production related to the spin, isospin, strangeness content and mass of the particles. The ``effective'' numbers of s and \bar{s} quarks in the isoscalar partners i_1 and i_2 are given by the nonstrange-strange mixing angle ϕ: k(i_1)=2\sin^2ϕand k(i_2)=2\cos^2ϕ. From the total production rates per hadronic Z decay of all light-flavour hadrons measured so far at LEP the values for k are found to be: k(η) \equiv 2-k(η^{\prime}) = 0.91 \pm 0.12, k(ϕ) \equiv 2-k(ω) = 1.94 \pm 0.09, k(f_2^{\prime}) \equiv 2-k(f_2) = 1.84 \pm 0.21 and k(f_0) = 0.09 \pm 0.13. Our results on the η--η^{\prime}, ω--ϕand f_2--f_2^{\prime} isoscalar mixing are consistent with the present experimental evidence. Quite remarkably, our value for k(η) corresponds to the singlet-octet mixing angle θ_P = -12.4^{\circ} \pm 3.5^{\circ}. The obtained strangeness content of the f_0(980) scalar/isoscalar is not consistent with the values supported by different model studies. However, taking the f_0(980) in our analysis with the mass of the bare state (K-matrix pole) f_0^{bare}(720 \pm 100), the mixing angle is found to be: |ϕ_S^{bare}| = 73^{\circ} \pm 7^{\circ} \pm 24^{\circ}, in good agreement with the prediction of the K-matrix analysis.

hep-ph↗

arXiv2001

Vector-to-Pseudoscalar and Meson-to-Baryon Ratios in Hadronic Z Decays at LEP

Mass dependences of the total production rates per hadronic Z decay of all light-flavour hadrons measured so far at LEP are extrapolated to the zero mass limit (m=0) using phenomenological laws of hadron production related to the spin, isospin, strangeness content and mass of the particles. The vector-to-pseudoscalar and meson-to-baryon ratios at m=0 are found to be: rho^+ / 3 pi^+ = 1.2 +/- 0.3 and pi^+ / p = 2.9 +/- 0.3, in good agreement with the predictions of quark combinatorics.

hep-ph↗

arXiv2000

Production Properties of the Orbitally Excited Mesons f_0(980), f_2(1270), K^*0_2(1430) and f'_2(1525) in Z^0 Hadronic Decays

DELPHI results are presented on the inclusive production of the neutral mesons rho^0, f_0(980), f_2(1270), K^*0_2(1430) and f'_2(1525) in hadronic Z^0 decays. They are based on about 2 million multihadronic events collected in 1994 and 1995, using the particle identification capabilities of the DELPHI Ring Imaging Cherenkov detectors and measured ionization losses in the Time Projection Chamber. The total production rates per hadronic Z^0 decay have been determined to be: 1.19 +/- 0.10 for rho^0; 0.164 +/- 0.021 for f_0(980); 0.214 +/- 0.038 for f_2(1270); 0.073 +/- 0.023 for K^*0_2(1430); and 0.012 +/- 0.006 for f'_2(1525). The total production rates for all mesons and differential cross-sections for the rho^0, f_0(980) and f_2(1270) are compared with the results of other LEP experiments and with models.

hep-ex↗

arXiv2000

Inclusive Particle Production at LEP

New results on inclusive production of Sigma^- and Lambda(1520) and on proton production in quark and gluon jets are presented. These results are based on 2 million hadronic Z decays collected with the DELPHI detector at LEP. They are compared with the results of other LEP experiments and with models. It has been shown that the total production rates of all light-flavour hadrons measured so far at LEP 1 follow phenomenological laws related to the spin, isospin, strangeness and mass of the particles. A significant proton enhancement in gluon jets is observed, indicating that baryon production proceeds directly from colour objects.

hep-ex↗