arXiv subjects

V. Bytev

Publications and source records attributed to V. Bytev.

45 records · Page 3Linked to original sources

arXiv2012

First observation of $η(1405)$ decays into $f_{0}(980)π^0$

The decays $J/ψ\rightarrow γπ^+π^-π^0$ and $J/ψ\rightarrow γπ^0π^0π^0$ are analyzed using a sample of 225 million $\jpsi$ events collected with the BESIII detector. The decay of $η(1405)\ar f_{0}(980)π^0$ with a large isospin violation is observed for the first time. The width of the $f_{0}(980)$ observed in the dipion mass spectra is anomalously narrower than the world average. Decay rates for three-pion decays of the $η'$ are also measured precisely.

hep-ex↗

arXiv2012

Precision measurement of the branching fractions of J/psi -> pi+pi-pi0 and psi' -> pi+pi-pi0

We study the decays of the J/psi and psi' mesons to pi+pi-pi0 using data samples at both resonances collected with the BES III detector in 2009. We measure the corresponding branching fractions with unprecedented precision and provide mass spectra and Dalitz plots. The branching fraction for J/psi -> pi+pi-pi0 is determined to be (2.137 +- 0.004 (stat.) +0.058-0.056 (syst.) +0.027-0.026 (norm.))*10-2, and the branching fraction for psi' -> pi+pi-pi0 is measured as (2.14 +- 0.03 (stat.) +0.08-0.07 (syst.) +0.09-0.08 (norm.))*10-4. The J/psi decay is found to be dominated by an intermediate rho(770) state, whereas the psi' decay is dominated by di-pion masses around 2.2 GeV/c2, leading to strikingly different Dalitz distributions.

hep-ex↗

arXiv2008

Physics at BES-III

This physics book provides detailed discussions on important topics in $τ$-charm physics that will be explored during the next few years at \bes3 . Both theoretical and experimental issues are covered, including extensive reviews of recent theoretical developments and experimental techniques. Among the subjects covered are: innovations in Partial Wave Analysis (PWA), theoretical and experimental techniques for Dalitz-plot analyses, analysis tools to extract absolute branching fractions and measurements of decay constants, form factors, and CP-violation and \DzDzb-oscillation parameters. Programs of QCD studies and near-threshold tau-lepton physics measurements are also discussed.

hep-ex↗

arXiv2007

Double logarithmical corrections to beam asymmetry in polarized electron-proton scattering

The up-down asymmetry in transversally polarized electron proton scattering is induced by the interference between one and two photon exchange amplitudes. Inelastic intermediate hadronic states (different from one-proton state) of the two photon exchange amplitude give rise to contributions containing the square of "large logarithm" (logarithm of the ratio of the transferred momentum to the electron mass). We investigate the presence of such contributions in higher orders of perturbation theory. The relation with the case of zero transfer momentum is explicitly given. The mechanism of cancellation of infrared singularities is discussed.

hep-ph↗

arXiv2007

Muon multiplicity at high energy proton-nuclei collisions

Estimation of multiplicity of muons and pions production at high energy proton-nuclei collisions is given. Both QED and QCD contributions are considered for peripheral kinematics of muon pair and $σ$-meson production, keeping in mind it's final conversion to muons. An attempt to explain the excess of positive charged muons compared to negative one in cosmic muon showers is given. We derive the dependence of cross-section of $n$ pairs as a function of $n$ at large n as $d^n(n!n^2)^{-1}$.

hep-ph↗

arXiv2006

Radiative corrections to chiral amplitudes in quasiperipheral kinematics

Chiral amplitudes for two jets processes in quasi-peripheral kinematics are calculated at the Born and one loop correction level. The amplitudes of subprocesses describing interaction of virtual and real photon with creation of a charged fermion pair for various chiral states are considered in details. Similar results are presented for Compton subprocess with virtual photon. Contribution of emission of virtual, soft, and hard real additional photons are taken into account explicitly. The relevant cross sections expressed in terms of impact factors are in agreement with structure function approach in the leading logarithmical approximation. Contributions of the next to leading terms are presented in an analytical form. Accuracy estimation is discussed.

hep-ph↗

arXiv2005

Compton and double Compton scattering processes at colliding electron-photon beams

Radiative corrections (RC) to the Compton scattering cross section are calculated in the leading and next-to leading logarithmic approximation to the case of colliding high energy photon-electron beams. RC to the double Compton scattering cross section in the same experimental set-up are calculated in the leading logarithmic approximation. We consider the case when no pairs are created in the final state. We show that the differential cross section can be written in the form of the Drell-Yan process cross-section. Numerical values of the $K$-factor and the leading order distribution on the scattered electron energy fraction and scattering angle are presented.

hep-ph↗

arXiv2002

Radiative Corrections to the $K_{e3}^{\pm}$ Decay Revised

We consider the lowest order radiative corrections for the decay $K^{\pm}\to π^0 e^{\pm} ν$, usually referred as $K_{e3}^{\pm}$ decay. This decay is the best way to extract the value of the $V_{us}$ element of the CKM matrix. The radiative corrections become crucial if one wants a precise value of $V_{us}$. The existing calculations were performed in the late 60's \cite{B,G} and are in disagreement. The calculation in \cite{G} turns out to be ultraviolet cutoff sensitive. The necessity of precise knowledge of $V_{us}$ and the contradiction between the existing results constitute the motivation of our paper. We remove the ultraviolet cutoff dependence by using A.Sirlin's prescription; we set it equal to the $W$ mass. We establish the whole character of small lepton mass dependence based on the renormalization group approach. In this way we can provide a simple explanation of Kinoshita--Lee--Nauenberg cancellation of singularities in the lepton mass terms in the total width and pion spectrum. We give an explicit evaluation of the structure--dependent photon emission based on ChPT in the lowest order. We estimate the accuracy of our results to be at the level of 1%. The corrected total width is $Γ=Γ_0(1+δ)$ with $δ=0.02\pm0.0002$. Using the formfactor value $f_+(0)=0.9842\pm 0.0084$ calculated in \cite{CKNRT} leads to $|V_{us}|=0.2172 \pm0.0055$.

hep-ph↗

arXiv2000

P-violating effects in low-energy Compton scattering

Parity of effects induced by one loop corrections of Standard model of Compton scattering are considered. We note the main effects arise from W contributions. Keeping in the mind scheme independent gauge invariance amplitude we calculated the one spin asymmetries for the case when initial electron is polarized and the case of circular polarized photon. They are of order $10^{-13}$.

hep-ph↗