Edward E.A. Knapp

Evidence for a 1-+ exotic meson

Abstract A non q q ,J PC = 1 −+ , I G =1 − meson has been observed in the study of the exclusive reaction π − p→π 0 ηn at 100 GeV. Its mass is (1406±20) MeV. Its width is (180±30) MeV.

Production of G(1590) and other mesons decaying into η pairs by 100 GeV/c π− on protons

Abstract New data on the scalar G(1590) meson which decays into ηη have been obtained in an experiment at the CERN SPS. η pairs are detected with the electromagnetic calorimeter GAMS both through their decay into 4γ and into 8γ. ϵ(1300), f(1270), f′(1525) as well as the spin-4 h(2030) mesons have also been observed to decay in the same mode. Their branching ratios have been evaluated. The presence of high-mass spin-0 and spin-2 structures is discussed.

Production of G(1590) in 300 GeV central

Abstract Significant production of G(1590), a scalar glueball candidate, is observed in a study of η pairs produced in π−N central collisions at 300 GeV/ c .

\pi^-

The decay η′ → ηπ0π0 → 6γ has been measured accurately with the GAMS-2000 spectrometer in a high statistics experiment performed at the 70 GeV IHEP accelerator. The parameters of a linear matrix element have been obtained which show that it is practically constant, with a slight dependence on only one of the Dalitz variables.

N collisions

Abstract The π − p→ ωω n reaction has been further studied at 38 GeV/ c with increased statistics. The peak at 2 GeV that has been previously observed in the ωω mass spectrum is due to two resonances. The first one is a tensor meson with a mass of 1920 MeV. The second is f 4 (2050). The branching ratio BR [f 4 (2050)→ ωω ] = 0.26±0.06 has been measured.

Matrix element of the η′(958) → ηπ0π0 decay

The partial widths of the η′(958) decays into 2γ, ωγ, 3π0 andηπ0π0 have been measured with the GAMS-2000 spectrometer at the 70 GeV IHEP accelerator. Upper limits for the η′ decays into 3γ, π0γγ, 2π0 and 4π0 have also been obtained. The slope of a linear matrix element for theG-parity violating decayη′→3π0 has been determined.

Further study of mesons which decay into ωω

A high-statistics study of the π0π0-system produced in the π-p→π0π0n reaction at 38GeV/c has been carried out at the IHEP accelerator using the GAMS-2000 multiphoton spectrometer. A partial-wave analysis which includesS, D0, D− andD+ waves has been performed in the |t|-range up to 1 (GeV/c)2. TheS*/f0(980) resonance is seen as a dip in theS-wave amplitude at small |t|. A distinct peak with a mass of 997±5MeV and a width of 48±10MeV is observed in theS-wave at |t|>0.3 (GeV/c)2. The production cross sections are measured.

Neutral decays ofη′(958)

Abstract The π − p→ ωω n reaction has studied for the first time at the 70 GeV IHEP accelerator. The six photons from the decay of the two ω mesons were detected in GAMS-2000, a hodoscope multi-photon spectometer. Two resonances decaying into ωω,X (1640) and X(1960), have been observed. Their quantum numbers are J PC =2 ++ , I G =0 + . The reaction is dominated by the one-pion exchange mechanism. The production cross sections σ. BR(X→ ωω ) are 0.65±0.15 μ b and 1.0±0.2 μ b, respectively.

Study offo (995) resonance in the π0π0 decay channel

Abstract Data on the 4π 0 decay mode of mesons have been obtained in a search for glueballs performed at the CERN SPS with the GAMS-4000 multiphoton spectrometer. A new tensor glueball candidate X(1810) appears as a clear peak in the 4π 0 mass spectrum. The 4π 0 decay of G(1590) is also observed. The measured value of BR(G→4 π 0 )/BR(G→ ηη )=0.8±0.3 further supports the glueball assignment of this scalar particle. The rate decay of f(1270) into 4π 0 has been measured: BR(f→4 π 0 ) = (3±1)×10 −3 .

Study of ωω systems produced in 38 GeV/c π- p collisions

Abstract A data acquisition system with high amplitude resolution (12 bits), high speed conversion (clock frequency 50 MHz), used in an experiment with a large number of counters (∼ 4200) is described. Physical quantities (masses and momentum transfer) are computed during data transmission itself, allowing improved trigger selectivity.