S. Spanier

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.

Exotic eta pi state in anti-p d annihilation at rest into pi- pi0 eta p(spectator)

Abstract With antiprotons stopped in liquid deuterium, the p n annihilation channel π−π0η was studied using a final sample of 52xa0576 events obtained for a spectator proton momentum q q quantum numbers IG=1−, JPC=1−+. The extracted Breit-Wigner resonance parameters are m=(1400±20±20) MeV/c2 and Γ=(310±50+50−30) MeV/c2.

Evidence for a πη-P-wave in p̄p-annihilations at rest into π0π0η

Abstract A partial wave analysis is presented of two high-statistics data samples of protonium annihilation into π 0 π 0 η in liquid and 12xa0atm gaseous hydrogen. The contributions from the 1 S 0 xa0, 3 P 1 and 3 P 2 initial atomic fine structure states to the two data sets are different. The change of their fractional contributions when going from liquid to gaseous H 2 as calculated in a cascade model is imposed in fitting the data. Thus the uncertainty in the fraction of S-state and P-state capture is minimized. Both data sets allow a description with a common set of resonances and resonance parameters. The inclusion of a π η P-wave in the fit gives supportive evidence for the ρ (1405) , with parameters compatible with previous findings.

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.

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.

Observation of f0(1500) decay into KLKL

Abstract The f 0 (1500) is observed in its K K decay mode in an amplitude analysis of high statistics data in p p annihilation at rest into π 0 K L K L . The mass and width is found to be ( m , Γ ) = (1515 ± 20, 105 ± 15) MeV. A comparison of the decay rate into 2 π 0 shows that this state cannot be dominantly s s . The f ′ 2 (1525) has been observed for the first time in p p annihilation and its production rate is consistent with the expectation from the OZI rule.

A study of f0(1500) decays into 4π0 in pp → 5π0 at rest

Abstract Crystal Barrel data on p p → 5π 0 at rest are presented. Mass spectra for 2 π 0 combinations, 3 π 0 and 4 π 0 and decay angular distributions all differ significantly from phase space. We present several ways of fitting the data. All agree on the definite presence of the f 0 (1500), observed in its 4 π 0 decay mode. It can decay into ππ(1300) and into σσ where σ stands for the full ππ S-wave amplitude.

Decay dynamics of the process η→3π0

Abstract The parameter α =−0.052±0.020 describing the shape of the η →3 π 0 Dalitz plot has been determined using the data from the Crystal Barrel detector at LEAR. The value is compared to predictions of chiral perturbation theory.

Momentum dependence of the decay η→π+π−π0

Abstract The π 0 momentum dependence of the decay η → π + π − π 0 has been measured with the Crystal Barrel detector. The analysis is based on 3230 events. The results of this independent measurement are compared to new chiral perturbation theory calculations and previous measurements.