B. Stella

TOTAL CROSS-SECTION FOR HADRONIC PRODUCTION BY E+E- ANNIHILATION IN THE TOTAL CM ENERGY-RANGE 1.42-3.09 GEV

Abstract We report experimental results on the cross section for the reaction e + e − → hadrons as a function of the total c.m. energy in the range W = 1.42–3.09 GeV. The results, combined with those already existing below the charm threshold, clearly indicate a structure for R ( W ) = α ( e + e − → hadrons)/ α ( e + e − → μ + μ − ) in that energy region.

Multihadronic cross sections from e+e− annihilation at C.M. energies between 1.4 and 2.4 GeV

Abstract Multihadronic production has been observed at the Adone e + e − storage ring, in the c.m. energy range 1.4 - 2.4 GeV. The cross sections for the reactions e + + e − → 2 π ± + nπ o (1 ⩽ n ⩽ 4) and e + + e − → (4 π ± + nπ ± ) (0 ⩽ n ⩽ 2) have been measured, assuming that the produced particles are only pions with a pure phase space momentum distribution.

Measurement of hadronic exclusive cross sections in e+e− annihilation from 1.42 to 2.20 GeV

Abstract Total cross sections for reactions e+e−→π+π−π0, π+π−π0, 2π+2π−π0, 2π+2π−2π0, 3π+3π− have been measured in the total c.m. energy range 1.42–2.20 GeV. Partial R=σhad/σσ+μ− values for two and four produced charged pions, and cross sections for positive and negative G-parity states are also reported.

Multihadronic cross sections from e+ e− annihilation up to 3 GeV c.m. energy

Abstract With an apparatus slightly improved with respect to a previous one we have studied multihadronic production at the Adone e + e − storage ring up to a maximum center of mass energy of 3 GeV.

Measurement of the e+e-→π+π-π+π- cross section in the ϱ′(1600) energy region

Abstract The cross section for the reaction e + e - →π + π - π + π - has been measured at the e + e - storage ring Adone, in the to tal c.m. energy range 1.42–2.20 GeV. The peak and the following descent of the ϱ′(1600) resonance is observed. Using also lower energy data, and assuming that only one resonant amplitude contributes to the observed cross section, the parameters of the ϱ′(1600) are deduced.

Evidence for a resonant behaviour in e+e− annihilation into hadrons, around 1820 MeV, at adone

Abstract Multihadron production has been measured at the Adone e+e− storage ring in the c.m. energy region 1600 ÷ 1900 MeV. A resonant behaviour is observed, centered at 1819 ± 5 (±2) MeV, with a width of 24 ± 5 (±4) MeV. This effect is observed only in the events with 3 or 4 charged particles together with photons, but not in those without photons.

Experimental results on a search for narrow resonances in e+e- annihilation into hadrons in the mass region 2520–2990 MeV

Abstract A search for possible new resonances produced in e + e - annihilation at Adone has been performed in the mass region 2520–2990 MeV. No evidence has been found for new resonances. We obtain an upper limit on the energy integrated resonant cross section of about 6% of the J/ψ (3100) corresponding value.

Search for narrow resonances in e+e− annihilation into hadrons in the mass regions 1910–2545 MeV and 2970–3090 MeV

Abstract We have searched for possible narrow resonances produced in e + e − annihilation at Adone, in the mass regions 1910–2545 MeV and 2970–3090 MeV. No evidence has been found for narrow resonances, within the sensitivity of the present work: we deduce an upper limit on the energy integrated resonant cross section of about 10% of the J/ψ(3100) corresponding value.

Multihadronic decays and partial widths of the J/Ψ (3100) resonance produced in e+e− annihilation at adone

Abstract The reactions e+e−→ hadrons and e+e+e−→e+e− have been studied at the J/gY (3100) resonance). The relative weights of the topological cross sections for fixed charged multiplicity are σ2=(32±5)%, σ4=(49±8)%, σ6=(18±3)%, and σ8=(1±0.6)%. The average pion multiplicities are 〈nch〉=3.8±0.3 and 〈nπo〉=3.1±0.8. The decay widths are Γe=(4.6±0.8) keV, Γh=(59±24) keV, and Γ=(68±26) keV.

Experimental results on photon-photon interactions at adone

Abstract Experimental results for the reactions e + e − → e + e − + X are presented for X = e + e − , μ + μ − , π + π − , ″. A tagging technique has been used to detect final electrons and positrons. A QED test is performed and an upper limit of 20 keV is derived for the partial width Γ ( η ′ → γγ ).