A. Calcaterra

Study of the J/ψ decay into five pions

Abstract A high statistics study of the J/ψ → π+π−π+π−π0 decay is performed from the 8.6 million J/ψs produced by the DM2 experiment at DCI. ϱ- and ω-associated production is evidenced and branching ratios for ϱa2(1320), inclusive ωπ+π−, ωf2(1270) and b1±(1235)π∓ dynamics are given. In the ωπ+π− final state a bump is observed at a low (π+π−) mass and a possible ωf0(975) contribution is discussed. Moreover first measurement of J/ψ → ωπ0π0 is reported and branching ratios for this decay and for ωf2(1270) and b1(1235)π0 dynamics are given. Evidence is found of the low (ππ) mass bump observed in the charged mode.

The pion electromagnetic form factor in the time-like energy range 1.35 ⩽ s ⩽ 2.4 GeV

Abstract The e+e− → π+π− cross section has been measured from about 280 events (an order of magnitude more than the previous world statistics) in the energy interval 1.35 ⩽ s ⩽ 2.4 GeV with the DM2 detector at DCI. The pion squared form factor |Fπ|2 shows a deep minimum around 1.6 GeV/c2 and is better fit under the hypothesis of two ϱ-like resonance ⋍0.25 GeV/c2 wide with 1.42 and 1.77 GeV/c2 masses.

Baryon pairs production ine+e− annihilation at\(\sqrt s = 2.4 GeV\)

AbstractSearch for baryon pairs production ine+e− annihilation at

Baryon pair production in Jψ decays

\sqrt s = 2386 MeV

Radiative decay of J /. psi. into. eta. (1430) and nearby states

is reported. The data relate to a luminosity of 161 nb−1 collected by the DM2 experiment at DCI, the Orsay colliding ring. First measurements of directe+e− annihilation into

Baryon pairs production in e + e - annihilation at <img src="/fullte

\Lambda \bar \Lambda