P. Kammel

A precision measurement of nuclear muon capture on 3He

In this article we report the results of an experiment performed in 1993 at PSI. The goal was to determine the absolute rate of nuclear muon capture by3He. In the experiment we used a new technique recently developed at Gatchina. As a preliminary result from this experiment we obtainedλc=(1496±3(stat)-3(syst)) s−1.

Measurement of the Rate of Muon Capture in Hydrogen Gas and Determination of the Proton's Pseudoscalar Coupling g P

The rate of nuclear muon capture by the proton has been measured using a new technique based on a time projection chamber operating in ultraclean, deuterium-depleted hydrogen gas, which is key to avoiding uncertainties from muonic molecule formation. The capture rate from the hyperfine singlet ground state of the microp atom was obtained from the difference between the micro(-) disappearance rate in hydrogen and the world average for the micro(+) decay rate, yielding Lambda(S)=725.0+/-17.4 s(-1), from which the induced pseudoscalar coupling of the nucleon, g(P)(q(2)=-0.88m(2)(micro))=7.3+/-1.1, is extracted.

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.

Measurement of muon capture on the proton to 1% precision and determination of the pseudoscalar coupling gP

The MuCap experiment at the Paul Scherrer Institute has measured the rate Λ(S) of muon capture from the singlet state of the muonic hydrogen atom to a precision of 1%. A muon beam was stopped in a time projection chamber filled with 10-bar, ultrapure hydrogen gas. Cylindrical wire chambers and a segmented scintillator barrel detected electrons from muon decay. Λ(S) is determined from the difference between the μ(-) disappearance rate in hydrogen and the free muon decay rate. The result is based on the analysis of 1.2 × 10(10) μ(-) decays, from which we extract the capture rate Λ(S) = (714.9 ± 5.4(stat) ± 5.1(syst)) s(-1) and derive the protons pseudoscalar coupling g(P)(q(0)(2) = -0.88 m(μ)(2)) = 8.06 ± 0.55.

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.

Experimental investigation of muon-induced fusion in liquid deuterium

Abstract The aim of this work was the accurate determination of the absolute values of the formation rates of muonic molecules from both hyperfine states of the muonic atoms in liquid deuterium (23.8 K) by measuring the absolute yield and time distribution of 2.45 MeV neutrons from dd fusion. The resulting dμd formation rates are λ 1 2 = [5.00 ± 0.34 (stat.) ± 0.22 (syst.)] × 10 4 s −1 and λ 1 2 = [3.25 ± 0.23 (stat.) ± 0.23 (syst.)]× 10 6 s −1 , respectively. In addition, the hyperfine transition rate between the upper and the lower hyperfine state was determined to be λhf = [3.05 ± 0.04(stat.) ± 0.06(syst.)]×107s−1. All results are normalized to the density of liquid hydrogen.

High precision study of muon catalyzed fusion in D2 and HD gas

Muon catalyzed dd fusion in D2 and HD gases in the temperature range from 28 to 350 K was investigated in a series of experiments based on a time-projection ionization chamber operating with pure hydrogen. All main observables in this reaction chain were measured with high absolute precision including the resonant and non-resonant ddμ formation rates, the rate for hyperfine transitions in dμ atoms, the branching ratio of the two charge symmetric fusion channels 3He + n and t + p and the muon sticking probability. The report presents the final analysis of the data together with a comprehensive comparison with calculations based on recent μCF theories. The energy of the loosely bound ddμ state with quantum numbers J = 1, ν = 1, which is central to the mechanism of resonant molecule formation, is extracted with precision ɛ11(fit) = −1.9651(7) eV. in impressive agreement with the latest theoretical results ɛ11(theory) = −1.9646 eV.

X-RAY EMISSION DURING THE MUONIC CASCADE IN HYDROGEN

We report our investigations of X rays emitted during the muonic cascade in hydrogen employing charge coupled devices as X-ray detectors. The density dependence of the relative X-ray yields for the muonic hydrogen lines (K_alpha, K_beta, K_gamma) has been measured at densities between 0.00115 and 0.97 of liquid hydrogen density. In this density region collisional processes dominate the cascade down to low energy levels. A comparison with recent calculations is given in order to demonstrate the influence of Coulomb deexcitation.

Further analysis of , ηηπ0 and ηπ0π0 at rest

Abstract A fresh analysis is reported of high statistics Crystal Barrel data on p p → 3π 0 , ηηπ 0 , ηπ 0 π 0 and ηη ′ π 0 at rest. This analysis is made fully consistent with CERN-Munich data on π + π − → π + π − up to a mass of 1900 MeV, with GAMS data on π + π − → π 0 π 0 , and with BNL and ANL data on π + π − → K K , which are fitted simultaneously. There is evidence for an I = 0, J PC = 2 ++ resonance with weak (≤ 7%) coupling to ππ, strong coupling to both ϱϱ and ωω and pole position 1534 - i90 MeV. This resonance agrees qualitatively with GAMS and VES data on ππ → ωω, previously interpreted in terms of a resonance at 1590–1640 MeV. New masses and widths for (A) ƒ 0 (1370) and (B) ƒ 0 (1500) , fitted to all eight data sets, are M A = 1300 ± 15 Mev, Γ A = 230 ± 15 MeV, M B = 1500 ± 8 MeV, Γ B = 132 ± 15 MeV. Branching ratios to ππ and ηη are given, and differ significantly from earlier determinations because of a new procedure.