Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userSeparation of $e^+e^-to e^+e^-$ and $e^+e^-topi^+pi^-$ events using SND detector calorimeter
67
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
The technique of discrimination of the $e^+e^-to e^+e^-$ and $e^+e^-to pi^+pi^-$ events in energy range $0.5 < sqrt{s} < 1$ GeV by energy deposition in the calorimeter of SND detector was developed by applying machine learning method. Identification efficiency for $e^+e^-to e^+e^-$ and $e^+e^-to pi^+pi^-$ events in the range from 99.3 to 99.8 % has been achived.
rate research
Read More
Calibration of the three layer NaI(Tl) spherical calorimeter of the SND detector using electron -- positron scattering events is described. Energy resolution of $5 % (FWHM/2.36)$ for 500 MeV photons was achieved.
Results of the SND experiment at the VEPP-2M e+ e- collider on the QED processes e+ e- --> e+ e- gamma and e+ e- --> e+ e- gamma gamma with production at large angles are presented. Energy and angular distributions of the final particles were studied. No deviations from QED with an accuracy of 3.8% for the first process and 10.3% for the second were found.
In experiment with the SND detector at VEPP-2M $e^+e^-$ collider the $e^+e^-toetagamma$ cross section was measured in the energy range $E$=0.60--1.38 GeV with the integrated luminosity of 27.8 pb$^{-1}$. The measured cross section is well described by the vector meson dominance model with contributions from the $rho(770)$, $omega(783)$, $phi(1020)$, $rho^{prime}(1465)$ resonances and agrees with results of previous measurements. The decay probabilities $BR(phitoetagamma)$, $BR(omegatoetagamma)$ and $BR(rhotoetagamma)$ were measured with the accuracies better than or comparable to the world averages.
Neutrinoless double beta decay, if detected, would prove that neutrinos are Majorana fermions and provide the direct evidence for lepton number violation. If such decay would exist in nature, then $pi^-pi^-to ee$ and $pi^-topi^+ ee$ (or equivalently $pi^-e^+topi^+ e^-$) are the two simplest processes accessible via first-principle lattice QCD calculations. In this work, we calculate the long-distance contributions to the $pi^-topi^+ee$ transition amplitude using four ensembles at the physical pion mass with various volumes and lattice spacings. We adopt the infinite-volume reconstruction method to control the finite-volume effects arising from the (almost) massless neutrino. Providing the lattice QCD inputs for chiral perturbation theory, we obtain the low energy constant $g_ u^{pipi}(m_rho)=-10.89(28)_text{stat}(74)_text{sys}$, which is close to $g_ u^{pipi}(m_rho)=-11.96(31)_text{stat}$ determined from the crossed-channel $pi^-pi^-to ee$ decay.
The process $e^+e^-to K^+K^-pi^0$ is studied with the SND detector at the VEPP-2000 $e^+e^-$ collider. Basing on data with an integrated luminosity of 26.4~pb$^{-1}$ we measure the $e^+e^-to K^+K^-pi^0$ cross section in the center-of-mass energy range from 1.28 up to 2 GeV. The measured mass spectrum of the $Kpi$ system indicates that the dominant mechanism of this reaction is the transition through the $K^{ast}(892)K$ intermediate state. The cross section for the $phipi^0$ intermediate state is measured separately. The SND results are consistent with previous measurements in the BABAR experiment and have comparable accuracy. We study the effect of the interference between the $phipi^0$ and $K^ast K$ amplitudes. It is found that the interference gives sizable contribution to the measured $e^+e^- to phi pi^0to K^+K^-pi^0$ cross section below 1.7 GeV.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
