Initial-state radiation measurement of thee+e−→π+π−π+π−cross section

Abstract

We study the process e + e − → π + π − π + π − γ, with a photon emitted from the initial-state electron or positron, using 454.3 fb −1 of data collected with the BABAR detector at SLAC, corresponding to approximately 260 000 signal events. We use these data to extract the non-radiative σ(e + e − → π + π − π + π − ) cross section in the energy range from 0.6 to 4.5 GeV. The total uncertainty of the cross section measurement in the peak region is less than 3%, higher in precision than the corresponding results obtained from energy scan data.

Study of the process e+e−→π+π−η using initial state radiation

“…Structures near the nucleon-antinucleon threshold are observed in the e þ e − → 3ðπ þ π − Þ and 2ðπ þ π − π 0 Þ cross sections [31,32] as well as in the η 0 π þ π − mass spectrum in the decay J=ψ → γη 0 π þ π − [33]. A slope change near 1.9 GeV is seen in the [34]. The fit is also performed with another parametrization.…”

“…The ISR photon and charged-particle track reconstruction efficiencies are studied in Ref. [28]. The efficiency corrections and systematic uncertainties discussed in this section are summarized in Table II.…”

Serendipity in dark photon searches

“…Data used to determine the hadronic decay rates from: the PDG, for the total rate to hadrons [78]; BaBar, for [82] (i.e. the isoscalar component of the KKπ final state), 2(π + π − ) [83], and π + π − π 0 π 0 [84]; and from SND, the low-mass π + π − π 0 [85,86] (displayed as filled squares). See text for discussion on the solid lines.…”

Hadronic footprint of GeV-mass dark matter

“…For the 4π channel, we use the parametrization of Ref. [74] and fit it to more recent rate measurements for e + e − → 2π 0 π + π − and e + e − → 2π + 2π − from BaBar [72,73]. We obtain a χ 2 /n.d.f = 1.28 and the fit values are listed in Tab.…”