Lifetimes of charged and neutralD mesons

We have measured the lifetimes of hadronically produced charged and neutralD mesons using silicon microstrip detectors and an active silicon target in the NA32 spectrometer at the CERN SPS. We obtainτ _D± = (10.9± _1.5 ^1.9 )·10^?13s andτ _D ^(?)10 = (4.2±0.5)·10^?13s based on 59 and 90 fully reconstructed decays respectively, giving a ratioτ _D±/τ _D ^(?)10 of 2.6 ±0.5.     

Radiative decay ofJ/ψ into γ π+ π−

The radiative decayJ/ψ → γ π⁺ π^? has been studied using the 8.6 millionJ/ψ produced in the DM2 experiment at the DCIe ⁺e^? storage rings at Orsay. The π⁺ π^? mass spectrum shows a cleanf ₂ (1270) signal, and the possible presence of two other states at thef ₂ (1720) andf ₄ (2030) masses. For thef ₂ (1270), the branching ratio BR(J/ψ →γf)xBR(f→π⁺ π^?) is measured to be (7.50±0.30±1.12)×10^?4, and the spin analysis prefers theJ=2 assignment, with helicity parametersx=0.83±0.06 andy=0.01±0.06. The existence of higher mass states is discussed.     

Microscopical studies at cadmium impurities in compound semiconductors

Molecule-like defect complexes have been studied at Cd acceptors in the III–V semiconductors GaAs, GaP, InP, InAs, and InSb by PAC spectroscopy. After hydrogen plasma treatment, the formation of Cd-H complexes was observed in all these compounds. Additionally, the formation and stability of Cd-S and Cd-Se pairs in GaAs have been analyzed.     

Hypernuclear production in the (K, π) reaction

Cross sections for the production of hypernuclei were measured in the reaction A(K⁻, π⁻) _ΛA. on light and heavy nuclear targets, using a separated K⁻ beam at the CERN Proton Synchrotron. The pions were detected in the forward direction. The results are compared with cross sections calculated under the assumption that the reaction took place on a single neutron. The good agreement between the measured and the calculated cross sections justifies the use of the (K⁻, π⁻) reaction in order to obtain spectroscopic information on hypernuclei.     

Inclusive production of non-strange resonances inK − p interactions at 32 GeV/c

New data on the inclusive production of the non-strange resonances ?⁰(770), ω(783), ?(1020) andf(1270) inK ^? p interactions at 32 GeV/c are presented. The inclusive production cross sections are equal to (4.32±0.72) mb, (3.7±1.4) mb, (0.65±0.10) mb and (0.91±0.35) mb respectively. Estimates of the topological cross sections are also obtained. The invariant and non-invariantx-distributions for the vector mesons ?⁰ and ? indicate the prevalence of forward resonance production in the c.m. system. For the tensorf-meson the rapidity andx-distributions are presented. Thet′-distributions for ?⁰, ?, andf have exponential slopes of 0.6±0.1 GeV^?2, 1.2±0.2 GeV^?2, and 0.8±0.5 GeV^?2 respectively. The exponential slope ofp _T ² -distribution of thef-meson is equal to (2.3±0.5) GeV^?2.     

Study of the charge-exchange reactions\pi ^ - p \to (\pi ^0 ,\eta ,\eta \prime )n at 63 GeV

Muon electron pairs were detected in an Al multiplate spark chamber, exposed to a neutrino beam from the CERN PS. The leptons were not accompanied by other particles, except occasionally by protons. The background came mainly from muon associated π⁰ production, with one decay gamma lost. It was determined empirically, together with the small contribution from υ _e reactions. For electron energies above 2 GeV the background is 5.7±1.5 events, whereas 18 (μe)-candidates have been observed. Hence the effect is established, with a rate of about 10^?4 as compared to the muonic reactions above 3 GeV. Charm creation as the origin of this (μe)-production process is excluded; heavy neutral lepton production does not fit the kinematics observed. Instead the events are compatible with the two-body decay of an object with variable invariant mass of order 1 GeV, possibly resulting from axion interactions.     

Experimental upper limits for hadronic and axion decays of the γ(1S)

A search for the decays γ→ρπ, γ→J/ψX and γ→γa (whereX is undetermined and a is an axion) has been completed using the LENA detector at the DORIS storage ring. No evidence for any of these processes was found. For these decay modes we set branching fraction upper limits (90% C.L.) of 2.1×10^?3, 2.0×10^?2 and 9.1×10^?4, respectively.     

Quadrupole interaction of8Li and9Li in LiNbO3 and the quadrupole moment of9Li

The quadrupole interaction of nuclear spin polarized⁸Li (I=2) and⁹Li (I=3/2) in LiNbO₃ has been studied at room temperature. The polarization was achieved by optical pumping of a fast atomic beam with circularly polarized laser light. The atoms were implanted into a hexagonal LiNbO₃ single crystal and the quadrupole splitting ofβ-NMR spectra was measured. A ratio of ¦Q(⁹Li)/Q(⁸Li)¦=0.88(4) for the nuclear quadrupole moments was deduced, yielding a new value of ¦Q(⁹Li)¦=25.3 (9) mb for the quadrupole moment of⁹Li.