π+p and K+p elastic scattering at 250 GeV/c

Results are presented on π⁺p and K⁺p elastic scattering at 250 GeV/c, the highest momentum so far reached for positive meson beams. The experiment (NA22) was performed with the european hybrid spectrometer. The π⁺p elastic cross section stays constant with energy while the K⁺p cross section increases.     

A study ofK + p elastic scattering and reactionK + p→K + pπ+π− at 70 GeV/c

Results are presented onK ⁺ p elastic scattering and on the reactionK ⁺ p→K ⁺ pπ⁺π^? at 70 GeV/c. For the elastic channel, we measured the total ((2.29±0.04)mb) and differentialdσ/dt cross sections. The reactionK ⁺ p→K ⁺ pπ⁺π^? has a total cross section of (470±23) μb and is shown to be dominated by diffractive dissociation processes. The contributions of the quasi-two-body channels $$K^ + p \to K*^0 (890)\Delta ^{ + + } (1,236)$$ and $$K^ + p \to K*^0 (1,430)\Delta ^{ + + } (1,236)$$ and of the Double-Pomeron Exchange (DPE) processes are estimated.     

Breakup effects of 6,7li on elastic and inelastic scattering from 12C at 18–28 MeV/nucleon

The differential cross sections for elastic scattering of ^6,7Li from ¹²C and inelastic one from the lowest three excited states of ¹²C have been measured at bombarding energies of 18–28 MeV/nucleon. Theoretical analyses of the data have been performed in which consistent treatments of density distributions for the ground and excited states of both projectile and target nuclei are made in the framework of microscopic cluster models for ^6,7Li and ¹²C and projectile-target interactions are generated by the double folding of the M3Y effective nucleon-nucleon interaction. About 25% reduction of the real part of folded potentials is required both in the analyses of elastic scattering with the single-channel calculation and in those of inelastic scattering with the coupled-channel calculation including the excited states of ¹²C. This reduction can be explained as a projectile breakup effect on elastic and inelastic scattering in comparison with a coupled-discretized-continuum-channels (CDCC) calculation and an extended CDCC one which allows mutual excitations of both projectile and target nuclei for ⁶Li case, respectively. It is also seen that an effect due to the target excitation on elastic scattering is of less importance than that of the ^6,7Li projectile breakup processes even fora deformed nucleus like ¹²C. Discrepancy between the extended CDCC calculation and inelastic data for the 0⁺₂ state of ¹²C suggests a strong influence from the ¹²C → 3α breakup channels in the ⁶Li case.     

Measurements of π+p,K+p and pp elastic scattering)

The paper presents the results on differential cross sections for elastic scattering of 7⁺-, K⁺-mesons and protons on protons in the 4-momentum transfer squared range 0·08 ¦t¦ 1·0 (GeV/c)² and incident particle momentum of 29 and 43 GeV/c for pions and kaons and 29, 43, 50 and 65 GeV/c for protons. The measurements were taken with the spectrometer Sigma, installed in the positive beam of the IHEP accelerator.Presented by F. A. Yotch at the Symposium on Hadron-Hadron Scattering at High Energies, Liblice, Czechoslovakia, June 16–21, 1975.The authors would like to express their gratitude to A. A.Logunov, Yu. D.Prokoshkin, L. D.Soloviev and V. A.Yarba for their support of this experiment. We are indebted to CERN Administration for giving us a permission to use a part of equipment of the CIBS spectrometer and to W.Kienzle for useful discussions.     

Elastic and inelastic scattering of π mesons on 7Li nuclei

Within the diffraction theory of multiple scattering, the differential cross sections for elastic and inelastic pion scattering on a ⁷Li nucleus are calculated for the case where the final nucleus is either in the ground or in the first excited state. The nuclear wave function is set to that in the αt cluster model. The sensitivity of the calculated observables to variations in the type of the wave functions for the alpha-particle and the triton cluster and for their relative motion is investigated. Various multiplicities of scattering and rescattering on the clusters constituting the ⁷Li nucleus are taken into account, and their contributions to the cross section are revealed. The results of the calculations are compared with experimental data at E _π=143, 164, and 194 MeV.     

An improved upper limit on the ντ-mass from the decay π−→π−π−π−π+π+ντ

Using the ARGUS detector at the e⁺e⁻ storage ring DORIS II, we have observed the decay τ⁻→π⁻π⁻π⁻π⁺π⁺ν_τ in tau-pair events produced at center-or-mass energies between 9.4 and 10.6 GeV. From the 5π invariant mass distribution we derive an upper limit of m(ν_τ)<35 MeV/c² at the 95% confidence level. The branching ratio for this decay channel is found to be (0.064±0.023±0.01)%.     

Determination of the branching ratio ofρ 0→+μ− in the coherent dissociation π−→μ+μ−π− and π−→π+π−π−

In the diffraction dissociation of π^? into μ⁺μ^?π^? on a Cu nucleus at 50 GeV/c, the cross section \(\sigma _{\mu ^ + \mu ^ - \pi ^ - } \) for the 1⁺S(ρ⁰π) wave was measured. The branching ratio of ρ⁰→μ⁺μ^? could be calculated from the ratio of this and the corresponding cross sections in the diffraction dissociation of π^? into π⁺π^?π^?. The obtained value \(BR_{\rho ^0 \to \mu ^ + \mu ^ - } = (4.6 \pm 0.2_{stat^ \pm } \pm 0.2_{syst} )10^{ - 5} \) is in good agreement with the branching ratio \(BR_{\rho ^0 \to e^ + e^ - } \) , as expected ifeμ universality holds.     

Study of theK + K − π+ π− system centrally produced in the reactions π+ p→π+(K + K − π+ π−)p andpp→p(K + K − π+ π−)p at 85 GeV/c

The reactions π⁺ p→π⁺(K ⁺ K ^? π⁺ π^? p andpp→p(K ⁺ K ^? π⁺ π^?)p where the (K ⁺ K ^? π⁺ π^?) system is centrally produced have been studied at 85 GeV/c. 48% of the final state proceeds through single or double vector meson resonant production i.e.,K ^*0(890) (37%), ? (4%),ρ ⁰ (7%). Evidence is found for associatedK ^*0 (890) \(\bar K\) ^*o (890) production (6.4±1.1%) with a cross section ten times higher than that found for associated ? ? production in the same experiment.     

Search for the ϕ → π+π−γγ and ϕ → π+π−η decays with the CMD-2 detector

The ? → π⁺π^?γγ and ? → π⁺π^?η decays are sought in the experimental data obtained with the CMD-2 detector in the region of the ?-meson resonance. Upper limits ?(? → ππγγ)< 1.2 × 10^?4 and ?(? → ππη) < 6.1 × 10^?5 (both at a C.L. of 90%) are determined for the branching ratios of these decays.     

A potential description of α-particle elastic scattering by the 6Li and 7Li nuclei

The results of analytic and numerical calculations of the real part of the ??⁶Li interaction potential in the cluster folding model are reported. Elastic scattering phases in the ??+^6,7Li systems are calculated and constructed, a classification of multipole transitions for back photodisintegration reactions is given.     

A study of K−π+ scattering in the reaction K−p→K−π+n at 11 GeV/c

Results from a high statistics study of the reaction K⁻p→K⁻π⁺n are presented. These results are based on data obtained with an 11 GeV/c beam using the LASS spectrometer at SLAC. The mass dependence of the spherical harmonic moments provides clear evidence for the production of the complete leading orbitally excited K¹ series up through J^P = 5⁻. These moments are used to perform an energy independent partial wave analysis of the K⁻π⁺ system from threshold to 2.6 GeV/c² using a t-dependent parametrization of the production amplitudes. The amplitudes corroborate the leading K¹(892), K₂¹(1430), K₃¹(1780), K₄¹(2060), and K₅¹(2380) resonances observed directly in the moments, and also provide new evidence for underlying states. The 0⁺ amplitude contains the K₀¹(1350) and a second 0⁺K¹(1950) at higher mass. The 1⁻K¹(1790) seen earlier two and three-body analyses is confirmed, and evidence is provided for suppressed K⁻π⁺ decay mode of a second 1⁻ state, the K¹(1410), which has been seen in earlier three-body analyses.     

On the effect of the parallel velocity on Li− formation in Li+-surface scattering

Li⁻ formation is studied by scattering a Li⁺ beam from a cesium covered tungsten (110) surface. The primary energy ranges from 1000 to 3000 eV. The measurements show that variation of the velocity component of the scattered particles parallel to the surface, can either enhance or decrease the Li⁻ formation probability. The sign of this parallel velocity effect depends on the value of the normal velocity component. The experimental results are qualitatively explained by a semi-classical model.     

Global optical model potentials for symmetrical lithium systems: 6Li+6Li, 7Li+7Li at Elab = 5–40 MeV

Angular distributions of ⁶Li+⁶Li elastic scattering were measured for E_lab = 5–40 MeV. An optical model analysis of these data together with older data of ⁷Li+⁷Li elastic scattering taken at E_lab = 8–17 MeV was performed with the aim to search for a “global” OM potential which describes elastic scattering in both LiLi systems in a broad energy range. Both surface and volume absorbing potentials can be found which fulfill this requirement if a linear energy dependence is assumed of the depths of the real as well as the imaginary potential. These depths, if fitted to individual angular distributions, are found to vary in a correlated manner with the beam energy. This is taken as indication of strong coupling between elastic, inelastic, and reaction channels. This is corroborated by the existence of resonances in reaction channels at these energies where the potential depths are most pronouncedly changing.     

There is no equivalence between ϱ′(1250) and inelastic effects in e+e−→π+π−

The analysis of all existing pion form factor data by a model respecting the fundamental principles, including (770), (1250) and (1600) contributions without inelastic effects and depending just on the physical parameters is carried out. The comparison of the obtained results with a previous analysis performed by means of a model with only (770) and (1600) contributions and inelastic effects confirmes the conclusions of Novosibirsk experimental group that the (1250) contribution and inelastic effects in e⁺e^–+– are indistinguishable. However, theoretically predicted behaviours of the P-wave isovector phase shift and the inelasticity from both models and their comparison with existing data unambiguously favour the model with (770), (1600) and inelastic contributions.We are indebted to Dr. D. Krupa who called our attention to the concise (in comparison with our original diagrammatized presentation) and transparent algebraic proof, given in the text by (30)–(33). One of us (A. Z. D.) would like to thank Professor Abdus Salam, the International Atomic Energy Agency and UNESCO for hospitality at the International Centre for Theoretical Physics in Trieste.     

Spin observables for 208Pb(→p, →p) elastic scattering at 290 MeV

A newly constructed focal-plane polarimeter for the medium resolution spectrometer at TRIUMF has been used to measure polarizations and polarization transfer coefficients for protons elastically scattered from ²⁰⁸Pb at 290 MeV. These results combined with existing cross section data at 300 MeV completely determine the elastic scattering amplitudes for momentum transfers q<2.6 fm⁻¹. The data are in quantitative agreement with Dirac calculations which take the effects of Pauli blocking into account, but disagree at small momentum transfer with density-dependent Schrödinger calculations.