T. Degener

Observation of two JPC=0++ isoscalar resonances at 1365 and 1520 MeV

From a simultaneous analysis of data on pp → π0π0π0 and pp → ηηπ0 at rest, two I = 0, JPC = 0++ resonances are identified above 1 GeV. The first has mass M = 1365−55+20 MeV and width г = 268 ± 70 MeV, close to the ƒ0(1400) of the Particle Data Group. The second has M = 1520 ± 25 MeV, г = 148−25+20 MeV.

High-statistics study of f0(1500) decay into π0π0

Abstract A partial-wave analysis of the reaction p p →π 0 π 0 π 0 has been performed using a high-quality high-statistics data set of 712 000 events. In addition to the f0(975) and f0(1300), the scalar resonance with mass m = (1500 ± 15) MeV and width Γ = (120 ± 25) MeV is necessary to describe the data.

Coupled channel analysis of pp annihilation into π0π0π0, π0ηη and π0π0η

We confirm the existence of the two IG(JPC) = 0+(0++) resonances f0(1370) and f0(1500) reported by us in earlier analyses. The analysis presented here couples the final states π0π0π0, π0π0η and π0ηη of pp annihilation at rest. It is based on a 3 × 3 K-matrix. We find masses and widths of M = (1390±30) MeV, Γ = (380±80) MeV; and M = (1500±10) MeV, Γ = (154 ± 30) MeV, respectively. The product branching ratios for the production and decay into π0π0 and ηη of the f0(1500) are (1.27 ± 0.33) · 10−3 and (0.60 ± 0.17) · 10−3, respectively.

Observation of a new IG(JPC)=1−(0++) resonance at 1450 MeV

Abstract A new IG=1− JPC=0++πη resonance is observed in pp annihilation at rest into π0π0η. It has a mass M=(1450±40)MeV and a width Γ=(270±40)MeV.

ηη′ threshold enhancement in p̄p annihilations into π0ηη′ at rest

Abstract We report on the observation of an ηη′ threshold enhancement produced in pp annihilations at rest into π0ηη′, which we identify with the recently discovered ƒ 0 (1500) .

Observation of radiative pp annihilation into a Φ meson

Abstract The annihilation p p → Φγ has been investigated with the Crystal Barrel detector at LEAR for antiprotons stopped in liquid hydrogen. The observed branching ratio BR ( p p → Φγ = (1.7 ± 0.4) · 10 −5 is almost two orders of magnitude higher than expected from the OZI-rule. As a by-product, the branching ratios BR ( p p → K L K S ) = (9.0 ± 0.6) · 10 −4 and BR ( p p → Φπ 0 ) = (5.5 ± 0.7) · 10 −4 have been measured.

Measurement of the decay distribution of η′ → π+π−γ and evidence for the box anomaly

Abstract The distribution of m ( π + π − ) in the decay η ′ → π + π − γ has been measured with the Crystal Barrel detector. The results are based on a total of 7392 observed η′ decays. The box anomaly constant is extracted from this and its value is found to agree well with theoretical expectations. The pseudoscalar nonet parameters ( f 1 , f 8 and θ PS ) are determined. Finally, we find that there is a problem of consistency between QCD and the standard VDM assumption.

Observation of a scalar resonance decaying to π+π−π0π0 in pp annihilation at rest

Abstract We report an analysis of p p annihilation at rest into ϱ + ϱ − π 0 leading to the final state π + π − 3 π 0 . A strong signal is observed for a scalar resonance with mass 1374 ± 38 MeV/ c 2 and width 375 ± 61 MeV/ c 2 , decaying to ϱ + ϱ − . The resonance in ϱ + ϱ − represents 2.0 ± 0.3% of all p p annihilation at rest. It is also observed to decay into two S-wave dipions ( π + π − ) ( π 0 π 0 )). Under the assumption of isospin 0, this is probably ƒ 0 (1400) , seen for the first time in its 4 π decay mode.

High statistics study of ƒ0(1500)s decay into ηη

Abstract A partial wave analysis of the reaction p p →π o ηη has been performed, using a high quality, high statistics data set of 198,000 events. In addition to the ƒ 0 (1370), a second scalar resonance decaying into ηη, the ƒ 0 (1500), with mass m = (1505 ± 15) MeV and width Γ = (120 ± 30) MeV has to be introduced to describe the data.

E decays to ηππ in pp annihilation at rest

Abstract We have observed the ηπ + π − and ηπ 0 π 0 decay modes of the E meson in p p annihilation at rest into π + π − π 0 π 0 η . The mass and width of the E meson are 1409 ± 3 and 86 ± 10 MeV. The production and decay branching ratio is B( p p → Eππ)B(E → ηππ) = (3.3 ± 1.0) × 10 −3 . With a spin-parity analysis we determine that J P = 0 − . The observation of the ηπ 0 π 0 decay mode establishes that E is isoscalar ( C = +1). We find that E decays to η ( ππ ) s (where ( ππ ) s is an S-wave dipion) and πa 0 (980)(→ πη ) with a relative branching ratio of (78 ± 16) %. Using the K K π production and decay branching ratio measured earlier we determine that B[E → K K π] B[E → ηππ] = 0.61 ± 0.19 . A comparison with observations in radiative J Ψ decays suggests that E and ι η (1416) are identical.