Search

Charm data from 360 GeV/c π− p interactions are used to give results on D-meson branching ratios. The analysis is based on 114 charm events containing 183 observed charm particle decays. We present topological branching ratios and decay multiplicities, as well as the following inclusive branching ratios of D-mesons: B( D ± → K ∓ + anything ) = 0.16 −0.07 +0.08 , if B( D 0 → K ± + anything ) = 0.44 −0.10 +0.11 , ifB( D ± → e ± + 2,4 (rmcharged hadrons) = 0.07 −0.05 ++0.08 , B( D 0 → e ± + anything ) = 0.17 −0.06 +0.08 .

We report on a search for μ-e conversion in muonic gold performed with the SINDRUM II spectrometer at PSI. The measurement resulted in Γ(μ-Au→e-Aug.s.)/Γcapture(μ-Au)

The SINDRUM II spectrometer at PSI is used in searches for μ → e conversion in muonic atoms. Here we report on a search for the charge-changing μ − → e + conversion on titanium. The measurements yielded the new upper limits Γ ( μ − Ti → e + Ca GS )/ Γ ( μ − Ti capture) −12 (90% CL) for the ground state transition and Γ ( μ − Ti → e + Ca GDR )/ Γ ( μ − Ti capture) −11 (90% CL) for a giant dipole resonance excitation with both a mean energy and a width of 20 MeV. These results improve on our previous best limits by a factor of 2.5.

The SINDRUM II spectrometer at Paul Scherrer Institute is used in a search for coherent $\ensuremath{\mu}\ensuremath{\rightarrow}e$ conversion in muonic atoms. We report on a measurement on lead, which resulted in $\ensuremath{\gamma}({\ensuremath{\mu}}^{\ensuremath{-}}\mathrm{Pb}\ensuremath{\rightarrow}{e}^{\ensuremath{-}}{\mathrm{Pb}}^{\mathrm{g}.\mathrm{s}.})/\ensuremath{\gamma}({\ensuremath{\mu}}^{\ensuremath{-}}\mathrm{Pb}\mathrm{capture})l4.6\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}11}$ (90% C.L.). This upper limit improves on the previous value by an order of magnitude. Combined with the limit on titanium, it is interpreted in terms of phenomenological couplings between the lepton current and the isoscalar and isovector quark currents.

R A L A B ST R A C T S Methods: We collected injection dates of benzathine penicillin G for all patients from 80 clinics from 2012 – 2014 (36 months). Injection data were matched against a database of RHD patients diagnosed through screening and commenced on SAP from 2006 – 2012. The observation period was adjusted for known migration mortality and cessation of treatment. Patients with 12 months of observation were included. We calculated the proportion of recommended injections received per individual, and the proportion of patients receiving adequate SAP to prevent disease progression (defined as 80% of injections). Risk factors for complete non-adherence (zero injections) were identified on bivariate analysis, and multivariate linear regression was used to identify factors associated with adherence in patients with 1 injection. Results: 495 patients were included (mean age 13.9 years, SD 2.89). Overall, 41.2% of the cohort received no injections, and 6.3% received adequate SAP. There were significant associations between complete non-adherence and age (p1⁄40.003) and the number of years since diagnosis (p

A search for μ → e conversion in muonic atoms is being performed at PSI with the SINDRUM II spectrometer. A first measurement on Ti gives upper limits on the branching ratios for the ground-state transitions of Γ(μ − Ti → e − Ti g.s. ) Γ(μ − Ti capture ) −12 and Γ(μ − Ti → e + Ca g.s. ) Γ(μ − Ti capture ) −12 (90% confidence ) . With the assumption of a giant resonance excitation of the Ca nucleaus the limit on the total rate for μ − → e + conversion is Γ(μ − Ti → e + Ca ∗ ) Γ(μ − Ti capture ) −11 .

A status report is given on an experiment started in 1987 at PSI to search for the lepton flavour violating muon to electron conversion process. The motivation for this experiment, the design and performance of the detector (SINDRUM II), and results of a first run are presented. No candidate of the process mu -Ti to e-Ti was found, and, using two independent determinations of the muon stop rate, an upper limit for the branching ratio relative to muon capture Bmu e

Duringtheyear2000theSindrumIIcollaborationatthePaul-ScherrerInsti- tute,Switzerland(PSI)performedanalruninasearchforcoherent !e conversion on gold. An improvementin sensitivity by two ordersof magnitude wasachieved, but no candidate events for the conversionprocess have been seen.

The performance of absorption heat pump cycles is to a great degree dependent on the substances used as the working pair. It is therefore of great interest to know the influences of the pure component properties of the absorbent and the refrigerant, respectively, and the influence of a mixture of both on the performance parameters of an absorption heat pump. A methodological approach based on fundamental thermodynamic relations is proposed to estimate the influence of the working pair on heat pump performance. On this basis, criteria to preselect working media can be established. A thorough simulation of absorption heat pump cycles shows that three properties predominantly influence the COP of a heat pump. These are the heat of evaporation of the refrigerant at normal boiling point and the size and location of the extremum of the excess Gibbs free energy of mixing, gE. Of these three properties the two properties of mixing exert the greatest influence. Good performances can be expected for working pairs which show high heats of evaporation for the refrigerants at normal boiling point and the extrema of the excess Gibbs free energy of −1000–2000 kJ kmol−1. The extremum of gE should preferably be located at high concentrations of the refrigerant.

The application of absorption cycles for high temperature heat recovery systems calls for the investigation of new working pairs. To qualify as a potential working pair, a mixture of two substances has to fulfill stringent requirements with respect to thermodynamic properties, corrosion and safety hazards like toxicity and inflammability. Based on a thermodynamic analysis of an absorption heat pump cycle a systematic search for new working pairs has been conducted. The investigation dealt exclusively with organic compounds. To get a first estimate of the properties of mixing, a molecular group contribution model (UNIFAC) was employed. This method has so far been widely used for chemical engineering purposes and renders agreeable estimates for the thermodynamic behavior of organic mixtures. With the help of the UNIFAC method, various pairings of functional molecular groups have been investigated for their possible potential to form effective working pairs for medium and high temperature absorption heat pump cycles. As a consequence of this analysis, ten alternative working pairs are proposed and their respective theoretical performance data and their toxicity characteristics are given.

An amplitude analysis has been performed for the reaction π+ p → (π+ π−) Δ++ at 16 GeV/c, constraining the relative spin between the target proton and theΔ++ to be 1. For low π+ π− masses, only S- and P-waves of the π+ π− system contribute. From the seven amplitudes determined, it is found that at low t′ values, the natural parity exchange amplitude gives the main contribution. The results are compatible with the same production mechanism for S- and P-waves. A Regge-pole model with π and A2 exchange, as well as cut terms, gives a good description of the energy and t′ dependence of the magnitude of the amplitudes; discrepancies are observed, however, for the phases at small t′ values.

The low-mass (Kππ) system of the reaction K−p → K−pπ+π− at 8.25 GeV/c is studied. The cross-section of this reaction is (0.97± ±0.04) mb. The dependence of the cross-section on the proton-proton momentum transfer shows broadening of the diffraction peak with respect to increasing (Kππ) mass. The production of two-body and three-body resonances is discussed with respect to their occurrence in the four longitudinal-momentum phase space sectors ofpl(π+)vs.pl(π−). This allows to separate the three-body low-mass systems (Kππ) and (pππ), which can be produced diffractively, from the other quasi-two-body processes whose production mechanism is meson exchange. In order to discuss what spin-parity contributions can be distinguished in the lowmass (Kππ) system, theD-moments of the angular distributions of the (Kππ) system with respect to variation of its effective mass and to variation of the possible analyser directions are carried out. The result is that, in addition to the dominantJP=1+ content, there is a clearly identifiableJP=0− contribution to the low-mass (Kππ) system. This contribution can be estimated to be 10% by an analysis of the density of events in the Dalitz plot, which gives also that the ρ production amplitude with respect to the K*(890) production amplitude decreases with increasing (Kππ) mass. This result is in agreement with an analysis of the reaction K+p→ K+pπ+π−. In the Appendix are given the properties of theD-moments and their predictability or suppression with respect to various spin-parity contributions.

A partial-wave analysis has been performed on the (K − π − π + ) system produced in the reaction K − p → K − π − π + p at 10 and 16 GeV/ c . In the Q mass region it is found that the two dominant states, K ∗ π and Kπ, both in 1 + S wave, are produced with different polarisations, helicity being approximately conserved in the t -channel for K ∗ π and in the s -channel for Kπ. This is in contradiction with the assumption that the amplitude can be factorised into “production” and “decay” parts, and hence that the two amplitudes are fully coherent. The phase variation of the two states do not indicate simple resonance behaviour. It is concluded that the Q-mass enhancement is composite.

A partial-wave analysis has been made of the (3π) system produced in the reaction π + p → ( π + π + π − )p at 8, 16 and 23 GeV/ c using the Illinois partial-wave analysis program. The (3π) systems is in about 93% of the cases in the unnatural spin-parity states 0 − , 1 + , 2 − and 3 + and is produced in about 100% of the cases by natural parity exchange. For all J P states, the differential cross section d σ /d t ′ peaks at small tt ′, except for 2 + D which has a dip at t ′ ≈ 0. The cross sections for J P = 1 + , 2 + and 2 − in the A 1 , A 2 and A 3 regions, respectively, all have similar energy dependence, p lab − n , with n = 0.3 ± 0.2. The weak variation of the 1 + S phase across the 1.0–1.2 GeV mass region, suggests that A 1 cannot be considered as a single resonance, while the phase variation of 2 + D (ϱπ) in the A 2 mass region is consistent with resonance behaviour. In the A 3 region, the behaviour of the 2 − S and 2 − P phases is complex and further work is needed to understand the mechanisms involved there.

The dominant partial waves of the diffractively produced Nπ system at low Nπ masses (⩽ 1.4 GeV) are determined in the reactions π±p → π(Nπ) at 16 GeV/c. A satisfactory description of our data can only be obtained by strong contributions of both a 12− S-wave and a 32+ P-wave, violating the Gribov-Morrison rule. Spin and parity of the diffractively produced states are found from the interference between diffraction and Δ (1236) production. The interference term is obtained by an isospin analysis.

Charm-charm correlation properties are studied in detail for the first time using a sample of D D pairs produced in 360 GeV/c π−p interactions. The data are compared with various models of charm production.

A partial-wave analysis has been performed of the diffractively produced low-mass ( K 0 π − π 0 ) system in the reaction K − p → ( K 0 π − π 0 ) p at 10 and 16 GeV/c . Thus information complementary to that derived from the K−p → (K−π+π−)p) channel is obtained. The presence of the Kϱ decay mode, besides the dominant K ∗ (890)π mode, for the state JP = 1+, is confirmed. It is also confirmed that for this 1+ state the assumption of factorization of the amplitude into “production” and “decay” does not hold: the two decay modes K ∗ π and Kϱ have different polarisation properties (helicity is approximately conserved in the t-channel for the first, in the s-channel for the second). The assumption that the ( K 0 π − π 0 ) system has isospin I = 1 2 has been tested and found to hold. From the cross sections for the various JP states, assuming I = 1 2 , the cross sections for the (K− π+π−) system are predicted and compared with the experimental ones. In general, agreement is found.

Three- and four-body final states with strange particles are studied in π + p and π − p interactions at 16 GeV/ c . We present cross sections and investigate their energy dependence. Production mechanism, resonance production and quantum number transfer are discussed. Strong Y ∗ (1385) production is found in the reaction π + p → Λ K + π + , while the corresponding π − p reaction is dominated by production of K ∗ (890). In the NK K π channels, the K and K are produced mainly at the same vertex, i.e. non-strangeness exchange ΔS = 0 is dominant (about 75% of the cases), whereas in the Λ K ππ channels, the Λ and K are more frequently produced at opposite vertices, i.e. | ΔS | = 1 exchange is important (about 60% of the cases). Results on the polarization of the lambdas produced in the π + p reactions are given.

By means of kinematic cuts, we select 1 421 events of the reaction K−p→K−pπ+π− at 16 GeV/c which involve the diffractive excitation of the proton. Decay of the diffractive cluster is most simply described in the Gottfried-Jackson reference frame, where a highly anisotropic decay is observed. The cluster, containing spin components J ⩾ 52, has a dominant decay mode δ++ (1236) π−.

The reactions (1) K − p → K + K − Λ and (2) K − p → p p Λ have been studied on samples of 109 and 64 events, respectively, at 10 GeV/ c and 125 and 69 events at 16 GeV/ c , reasonably free from contaminations. The investigation of the first reaction uses also 84 events of the K 0 K 0 Λ final state at 10 GeV/ c . Analysis of the Van Hove plots indicates that the K + K − Λ and p p Λ final states are produced by two main mechanisms: (i) a ΔQ = 0 process, with a strong diffractive component near threshold, involving the dissociations p → K + Λ in reaction (1) and K − → p Λ in reaction (2) and (ii) a ΔQ = 1 process involving hypercharge exchange, and producing K + K − and p p systems in reactions (1) and (2), respectively, recoiling off the Λ. With increasing energy, this hypercharge exchange process decreases slowly when K + K − is produced, but fast where the production of p p , violating the Zweig rule, occurs.

Results are presented for p → (ΛK+) dissociation in the reactions K−p → ΛK+K− and and π±p → ΛK+π±at 10 and 16 GeV/c. The cross sections for the low-mass ΛK+ enhancement are compatible with the energy dependence σ ∝ plab−0.3. The t′ spectra or the (ΛK+) threshold enhancement are exponential in shape. Its decay angular distribution reveals neither s-channel nor t-channel helicity conservation. The relative probabilities of the processes p → p, p → ( N π) I= 1 2 and p → (Λ K + ) dissociation are in the ratios 100 : 10 : 0.2, independent of the nature of the incident particle.

A partial wave analysis of the non-diffractively produced ( K 0 π + π - system has been performed. The system was produced in the reaction K - p→ K 0 π + π - n at 10 GeV/c, measured in the CERN Omega spectrometer. Besides the well-known K∗(1420) resonance, we find good evidence for the production of Q2(1400) and some indication for Q1(1290) production in JP=1+. In addition we clearly observe a bump in the 1800 MeV region, the properties of which are discussed.

A method is presented for deriving channel cross sections for all multiplicities, considering both charged and neutral particles, for K − p reactions of pion production, Thus the “true”, rather than charged, multiplicity is obtained. The input data are the channel cross sections measured with four- and one-constraint fits. The model employed is the two-component one, so that for each reaction channel, separate cross sections are derived for kaon diffraction, proton diffraction and for non-diffractive processes. Results are obtained up to the highest energies at which data of channel cross sections are available, i.e. up to 16 GeV/ c incoming momentum, and some extrapolation is also made towards higher energies. It is found that the cross section for single kaon diffraction dissociation is equal to that for single proton diffraction dissociation. In the energy range considered, the sum of kaon and proton single diffraction processes has a cross section of (2.4 ± 0.3) mb, i.e., about 75% of the elastic cross section. The cross section for kaon diffraction dissociation into (Kπ) is consistent with zero.

The reactions K − p → K N 3π are studied at 10 and 16 GeV/ c . Evidence is presented for the diffractive dissociation processes K → K 3π and p → N 3π , based on the observation, in the reactions involving no exchange of charge, of threshold enhancements in the K 3π and N3 π mass spectra with cross sections weakly dependent on energy. In the charge exchange reactions, the K 3π and N 3π spectra increase smoothly from threshold, and their energy dependence is strong. The most important decay channels contributing to the K → K 3π diffractive systems are K ω, K 1420 ∗ π and the two-resonance channel K 890 ∗ ϱ . For p → N3 π , major decay channels are pω and Δππ. For a fixed mass, it is found that the slopes of the d σ /d t ′ distributions are approximately the same as those observed for diffractive dissociation into lower multiplicities.

Cross-section values or upper limits are presented for twenty-five two-body hypercharge-exchange reactions in K−p and π+p interactions at 10 and 16 GeV/c. The 16 GeV/c results are compared with some predictions of line-reversal plus exchange-degenerate Regge poles, of SU(3) and of the additive quark model. Agreement is found in all cases.

By means of an isospin analysis of the reaction π±p→π(Nπ) at 16 GeV/c we have determined the decay angular distributions of the Nπ system with I= 1 2 produced by isospin zero exchange. Helicity conservation is not observed in the t-channel for the Nπ mass region below 1.6 GeV, where diffraction dissociation of the proton is supposed to dominate. There are indications for approximate t-channel helicity conservation for N∗ (1690) production. In the helicity frame, the experimental data are not in agreement with s-channel helicity conservation over the whole Nπ mass range investigated. Thus the diffractive process N→Nπ differs both from the process N→Nππ (or π→πππ and K→Kππ) which approximately conserves t-channel helicity and from the elastic scattering N→N which conserves helicity in the s-channel.

We have performed a partial-wave analysis of the mainly diffractively produced low-mass (Kππ) system in the reactions K−p→K−π+π−p and K−p → K0π −π0p at 10, 14 and 16 GeV/c. We find that the dominant 1+S(K∗π) state has possibly a two-peak structure (around 1.27 and 1.37 GeV). In contrast the 1+S(Kϱ) state shows one narrow peak near thershold (around 1.27 GeV). These states are found to be of different origin. The results favour the interpretation of the 1+S(Kϱ) as a 1+ resonance below the (Kϱ) threshold. The t′pp dependence is found to be different for the 1+ and 0− states.

The reaction π−p → K+K− π− p at 16 GeV/c was studied in the CERN OMEGA spectrometer and a partial-wave analysis (PWA) of the low-mass (K+K−π−) system (1.3–2.0 GeV) was performed. Only states in the unnatural spin-parity series produced by natural parity exchange are important and they approximately conserve t-channel helicity. The 1+S K∗K wave dominates the low-mass (K+K−π−) region. We observe an enhancement in 2−P K∗K wave at a mass of 1.7 GeV, consistent with the decay of the A3 resonance.

The reaction K−p→K−K−K+p is shown to have properties similar to those of the diffractive reaction K−p→K−π−π+p. This is true, at least in first approximation, for (a) the energy dependence of the cross sections, (b) the shape of the three meson spectra and (c) the differential cross sections dσ/dtpp which have the same slope for the same mass of the three-meson system. Furthermore, the partial-wave composition of the (KKK) system is similar to that of the (Kππ) system, both systems being produced mostly in unnatural spin-parity states by natural parity exchange. In the KKK system, the JP = 1+ state with S-wave decay into Ko(1020) is dominant, (72 ± 11) % of all events with (KKK) masses below 2 GeV.

In the data taken for the μ + → e + e + e - and π + → e + ν e + e - experiments a search was made for neutral particles φ produced in the decay μ + → e + φ or π + → e + νφ with subsequent decay φ → e + e - . No candidates were found, Upper limits for the branching ratios are given as a function of their masses and lifetimes. For lifetimes below 10 −10 s limits down to 2 × 10 −12 are obtained.

The radiative pion decay π + →e + ν e e + e − has been measured and values for the weak form factors F V , F A and R have been obtained. The measured branching ratio is Λ ( π + →e + ν e e + e − )/ Λ ( π + → μ + ν μ )=(3.2±0.5)×10 −9 . A light Higgs boson h with standard couplings to quarks is excluded in the mass range 10 MeV/ c 2 ⩽ m h ⩽110 MeV/ c 2 at 90% CL.

A partial wave analysis of the 3π-system has been performed for the reaction π+p (π+π−π0) Δ++ (1232) at 16 GeV/c. Beside the well-established A20 (1300), the resonant state ω* with isospin I = 0 and spin-parity JP = 3− decaying mainly into (ϱπ) has been found. Its mass and width have been determined to be M = (1.71 ± 0.03) GeV and Γ = (0.22 ± 0.10) GeV. The cross section for the reaction π+p ω* (1700) Δ++ (1232) is σ = (12 ± 6) μb. Eine Partialwellenanalyse der Reaktion π+ P (π+π−π0) Δ++ bei 16 GeV/c Strahlimpuls Fur die Reaktion π+p (π+π−π0) Δ++ (1232) wurde bei 16 GeV/c eine Partialwellenanalyse des Dreipionsystems durchgefuhrt. Neben der gutbekannten Resonanz A20 (1300) wurde der Resonanzzustand ω* mit Isospin I = 0 und Spinparitat JP = 3− in seinem Hauptzerfallskanal (ϱπ) gefunden. Masse und Breite wurden zu M = (1,71 ± 0,03) GeV und Δ = (0,22 ± 0,10) GeV bestimmt. Der Wirkungsquerschnitt fur die Reaktion π+p ω* (1700) Δ++ (1232) betragt σ = (12 ± 6) μb.

The radiative pion decay π+ → e+νe+e- has been observed for the first time. Information on the form factors was obtained from the kinematical distribution of 79 events. The vector form factor has the same sign as the pion decay constant fπ. The ratios of axial-vector form factors to the vector form factor are γ = F A F V = 0.7 ± 0.5 and ξ = R F V = 2.3 ± 0.6. The value for γ is in agreement with the small positive value (0.53 ± 0.06) and excludes the large negative value (−2.49 ± 0.06) of γ obtained in π+ → e+νγ experiments.

A new method to calculate diffractive mass spectra has been developed. It is applied to K - p interactions at 10 and 16 GeV/ c . Cross sections and mass spectra are given for the difractive dissociation processes p→(N+ iπ ) and K - p→(K+ iπ ) for i = 1 to 5 and also summed over all multiplicities. In addition to the diffractive peak at low mass coming from low multiplicities, a long tail extending to high masses and high multiplicities has been found. The multiplicity structure of diffraction dissociation can be understood in the context of the two-step dynamical picture of Pokorsky and Van Hove.

A parital wave analysis of the (Kππ) system produced in K−p → (K−π−π+)p at 10 and 16 GeV/c has been performed. It is found that in 88% of the cases the Kππ) system is in unnatural spin-parity (JP) states 0−, 1+, 2− …, with contributions from many decay modes, κπ, K ∗ (890)π, K ∗ (1420)π, K ϵ, K ϱ and Kf . More than one decay m and JP state are required to describe the Q and L enhancements, suggesting a composite structure of these enhancements. The (Kππ) system is produced dominantly (∼95%) by natural parity exchange. Overall, the production mechanism of the (Kππ) system is remarkably similar to that of the 3π system in π−p → (π−π−π+)p, even i detailed spin-parity structure.

Evidence is examined for double diffraction dissociation in the reactions π±p → (3π)±(Nπ)+ with (3π)± masses between 1.0 and 1.2 GeV at 16 GeV/c incident beam momentum. The data considered are found to reveal: 1. (a) isospin zero exchange, 2. (b) the expected factorisation properties, 3. (c) a dσ/dt′ slope compatible with those deduced from single dissociation processes and elastic scattering, and (d) as shown by an analysis of D moments, (3π)± systems with the same typical spin-parity composition as observed in the diffractive single dissociation reactions π±p → (3π)±p. Comparison of the 16 GeV/c data with data of an 8 GeV/c experiment indicate an almost energy-independent cross section for the process investigated.

The reactions π±p→(π±K+K−)p are studied, at 16 GeV/c, and in particular the low-mass π±K+K− system is compared with the diffractively produced 3π system in the reactions π±p→(π±π+π−)p at the same energy. Similarities are found in (a) the weak energy dependence of their cross sections, (b) the shape of the three-meson mass spectra, (c) the differential cross sections which have the same slope for the same value of the three-meson invariant mass, (d) the general characteristics of the partial-wave composition of the low-mass three-meson systems (as for the 3π case, the πKK system is produced in unnatural spin-parity states with JP=1+ dominant at low πKK mass, the state JP=0−, however, may be relatively more abundant in the πKK than in the 3π case) and (e) the exchange which is almost entirely of natural parity. We conclude that the reaction π±p→(π±K+K−p, for low values of the πKK mass, represents the diffractive dissociation process π→πKK, which is less probable than π→πππ by one order of magnitude.

An experiment has been undertaken at the CERN SPS, using the Omega spectrometer, aimed at confirming the enhancement observed in a p p φ − mass spectrum at 2.95 GeV [1]. With statistics of twelve times the original experiment no signal is seen. In the reaction φ − p → p p φ − p , the upper limit (four standard deviations) for the production of a resonance in the p p φ − system at 2.95 GeV, with a width ⩽ 30 MeV, is 50 nb.

Results on K∗(890) production in K−p → NKπ reactions at 16 GeV/c are presented. Total cross sections, differential cross sections and density matrix elements are determined. It is found that: (i) The cross section for K∗−(890) p is consistent with containing two components, one due to natural parity exchange, falling slowly with increasing energy, the other, due to unnatural parity exchange, vanishing rapidly with increasing energy. For K∗o(890)n, the cross section decreases steadily as the energy increases. (ii) Natural spin-parity exchange dominates in the K∗−(890) p channel, the unnatural exchange contribution being approximately (5±4)%. In K∗o(890)n, natural spin-parity exchange is only about (30±10)%. (iii) The reacton K−p → K∗−(890)p is dominated (95±5)% by isoscalar exchange. (iv) The effective trajectory involved in the I = 0 natural parity exchange is consistent with the ω-f trajectory. (v) Interference terms between exchanges with positive (f, πo,…) and negative (ϱo, ω,…) C-conjugation amount to (23±12) μb at 16 GeV/c.

A comparison is made of the properties and production mechanisms of the π+ω and K−ω systems produced in the reactions π+p → π+ ωp at 4, 5, 8 and 16 GeV/c and K− p → K−ωp at 10 and 16 GeV/c. In the π+ω case apeak is observed at 1.23 GeV (the B meson), while the K−ω mass distribution has a threshold enhancement. The cross section of the low mass (

The reaction π − p → φφ n has been isolated at 16 GeV/ c and its cross section determined to be 40 ± 10 nb. The φφ mass spectrum shows a threshold enhancement between 2.1 and 2.5 GeV. A successful description of the angular content of the φφ system requires two interferingss J P = 2 + states.

A spin-parity analysis is presented of the (K−π+) system produced in the reaction K−p → (K−π+)n at 10 and 16 GeV/c for M(Kπ)

The inclusive cross sections for forward D meson production at s =26 GeV in π − p interactions have been measured to be: σ(π − p → D 0 / D 0 + X ) x F >0 = (10.1±2.2)μ b , σ(π − p → D ±+ X ) x F >0 = (5.7±1.6)μ b . The distribution in x F for all D and for x F >0 has the form d σ/ d x F =107 −37 +39 (1−x F ) 7.5 −1.7 +2.5 +5.4 −3.8 +6.0 (1−x F ) 0.7 −0.7 1.0 μ b , with evidence for leading D production. The p T 2 distribution is exponential with slope parameter [−1.18 −0.16 +0.18 ]( GeV / c) −2 . The data are compared with predictions from first-order quark/gluon fusion calculations.

A comparison is made of the low-mass three-meson systems (πππ), (Kππ), (π K K ) and ( K K K ) diffractively produced in the reaction meson + proton → three mesons + proton. Several striking similarities and a few important differences are observed: (i) the reactions are consistent with the assumption that the three mesons decay entirely into a 0− meson and a 0+, 1− or 2+ resonance; (ii) the three-meson mass spectra have a peak ≈ 250 MeV above the effective threshold Meff of the dominant decay mode and then fall off approximately as (mass)−3;(iii) the average spin 〈J〉 = 0.55 + 1.1 Qeff, where Qeff = M - Meff; (iv) the average orbital angular momentum 〈l〉 increases according to 〈l〉 = 0.75 Qeff; (v) the three-meson states are produced dominantly in unnatural spin-parity states and no evidence for their being resonant is found; (vi) the only natural spin-parity states found are the well-established 2+ resonances A2 and K∗ (1420); they have similar properties to the non-resonant unnatural parity states except for a dip at t = 0 in the dσ/dt distributions; (vii) both the unnatural and natural spin-parity states are produced mostly by an exchange of natural parity; (viii) there is evidence for two types of production mechanism with different polarization properties, one approximately conserving helicity in the t-channel and the other in the s-channel.

A study is presented of the reactions K+p→(K+ω)p at 8.25 and 16 GeV/c and K−p→(K−ω)p at 10 and 16 GeV/c and comparison is made with K+ results at 10 GeV/c and K− at 7.3 GeV/c. The (K+ω) and (K−ω) mass spectra both present a strong enhancement very near threshold, while a second peak at ∼1.7 GeV is evident only with incident K− at the lower energies. The threshold peak has very weak energy dependence and is mostly due to the 1+S state which is produced conserving s-channel helicity. It is suggested that this is another decay mode of the resonance Q1(1290) known to decay mainly into Kϱ. The ratio of the Q1 coupling constants to the Kω and Kϱ decay channels, Rω = gKω2/gKϱ2 is determined to be 0.21±0.04. The enhancement at 1.7 GeV is predominantly, but not exclusively, due to the 2− state. While the K+ and K− induced reactions give basically similar results, small differences are observed that can be qualitatively explained in the framework of the Deck model.

A partial-wave analysis of the K−π+π− system has been performed in the L-region of the Kgpg mass (1.5–2.0 GeV) in the reaction K−p → (K−gp+gp−)p. The unnatural spin-parity states 0−, 1+, 2−, 3+ are found to dominate over the natural states 1−, 2+, 3−. The 2−S(K∗(1420) gp) shows the characteristics of a threshold enhancement. There are indications for a 2− resonance (M ⋍ 1.58 GeV, Γ ⋍ 0.11 GeV) in the K∗(890) π P-wave system. The L-enhancement seen in the total Kππ mass spectrum at ∼1.75 GeV is a superposition of enhancements in several partial waves.

An enhancement in the (K−π+) mass distribution at 1871 ± 10 MeV with full width of 285 ± 40 MeV is observed in the charge-exchange reaction K−p → K−π+n at 10 and 16 GeV/c. The energy dependence of its cross section, the shape of the differential cross section dσ/dt and the decay angular distributions are consistent with a production mechanism by pion exchange. No significant enhancement at the same mass is seen in the non-charge exchange reaction K−p → (Kπ)−p. The experimental evidence is reviewed and it is suggested that there may be more than one K∗ enhancement in the 1700–1900 mass region.

The search for the decay μ+ → e+e+e− with the SINDRUM spectrometer has been continued. The result is a new upper limit for the branching ratio B μ→3 e = Γ(μ→3 e ) Γ(μ→ e 2ν) −12 (90% CL ) .