Abstract
The cross section of the process e+e−→ π+π−π+π− has been measured using an integrated luminosity of 17 pb−1 collected with the CMD-3 detector in the center-of-mass energy range 650-1000 MeV. High-precision measurements of various hadronic cross sections are of great interest in relation with the problem of the muon anomalous magnetic moment g-2. This measurement can be also used to test the relation between the cross section of e+e−→ π+ π−π+ π− and the spectral function for the τ−→ π−π0π0π0 decay predicted by the conservation of vector current (CVC).
Highlights
The VEPP-2000 electron-positron collider has been oper√ated at Budker Institute of Nuclear Physics in the center-of-mass (c.m.) energy range from s = 320 MeV to 2000 MeV
We use ionization losses in DC to separate electrons and pions if the track momentum is below 100 MeV/c
If it is above 100 MeV/c and Ecal − 12/11 ∗ ptr + 70 < 0 we assume a pion hypothesis for such tracks
Summary
Production of four charged pions in e+e− annihilation has been studied before with rather high statistics at the CMD-2 [4] and SND detectors [5] as well as using initial-state radiation (ISR) with BaBar [6] at which a low systematic uncertainty of about 3% was achieved for the e+e− → π+π−π+π− cross section in the wide c.m. energy range. The background in the studied energy region comes from the processes e+e− → π+π−π0, e+e− → e+e−e+e− and e+e− → e+e− with extra tracks from decays or nuclear interaction of pions as well as from a conversion of the photons from the π0 decay in the detector material.
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