Separation ofe⁺e⁻→e⁺e⁻ande⁺e⁻→ π⁺π⁻events using SND detector calorimeter

Abstract

ABSTRACT:The technique of discrimination of the e + e − → e + e − and e + e − → π + π − events in energy range 0.5 < √ s < 1 GeV by energy deposition in the calorimeter of SND detector was developed by applying machine learning method. Identification efficiency for e + e − → e + e − and e + e − → π + π − events in the range from 99.3 to 99.8 % has been achived.

Measurement of the e+e− → π+π− process cross section with the SND detector at the VEPP-2000 collider in the energy region 0.525 < $$ \sqrt{s} $$ < 0.883 GeV

“…e + e − → π + π − events (R) in the energy region √ s = 0.5-1.0 GeV is based on the differences in the energy deposition profiles. It was developed using machine learning method [43]. The distribution of the separation parameter R is shown in figure 2.…”

“…To take this inaccuracy into account, the detection efficiency is multiplied by the correction coefficient. The correction coefficient is obtained by using pseudo ππ events, which are constructed using events of the processes e + e − → ω(φ) → π + π − π 0 and e + e − → π + π − [43]. The corrections obtained using different types of pseudo events differ less than 0.005, they do not depend on the pion energy and their average is equal to 0.992.…”

“…Uncertainties in simulation of energy depositions in the calorimeter can lead to an inaccuracy in e/π discrimination. The identification efficiency and related systematic error were studied in [43] using pseudo-ππ and pseudo-ee events. It varies with energy from JHEP01(2021)113 0.996 to 0.998 for the e + e − → e + e − events and from 0.994 to 0.998 for the e + e − → π + π − events.…”

Recent results from SND detector at VEPP-2000 collider

“…Using energy depositions in the calorimeter's counters the selected events were divided into two classes e + e − → e + e − and e + e − → π + π − , µ + µ − . The events separation was based on the machine learning approach [6]. The e + e − → e + e − events were used to obtain integrated luminosity.…”

Separation ofe+e−→e+e−ande+e−→ π+π−events based on the difference in the energy deposition profiles in SND detector calorimeter.

“…In order to perform the measurement with high accuracy the separation parameter of e + e − → e + e − and e + e − → π + π − events with the energy √ s = 0.5-1.0 GeV based on differences in energy deposition profiles in SND calorimeter has been developed [5].…”