Recoil properties of27Mg from the27Al(γ, π+)27Mg reaction

The mean ranges of the recoil nuclei from the reaction²⁷Al(γ, π⁺)²⁷Mg have been measured at maximum bremsstrahlung energies of 250, 400 and 800 MeV using catcher-foil techniques. The experimentally-determined ranges in directions along and perpendicular to the photon beam are in good agreement with calculated values based on the Fermi gas model and the impulse approximation.     

Two-nucleon pion absorption in 3,4He

Results are presented for π⁺NN → Np yields in ^3,4He relative to πd → pp from (π, p) measurements at energies between 50 and 295 MeV and estimates are given for total cross sections. These yields are nearly proportional to the number of target NN pairs, which is not true for ⁶Li and heavier nuclei. This is believed to indicate that πNN → Np is sensitive to the NN short-range behavior which is deuteron-like for ^3,4He but not always so for NN pairs in other nuclei.     

Near-threshold pion production by protons on nuclei

The p + p → d + π⁺ process is considered in detail along with the p + N → N + N + π process. Such consideration makes it possible to show the difference in the production cross sections for π⁺ and π^? mesons on nuclei. In this case, experimental data can be reproduced both above the pion production threshold at a proton energy of 350 MeV and under the threshold at a proton energy of 180 MeV.     

Deuteron production in collisions of 250 GeV/c π+ andK + mesons with Al and Au nuclei

Experimental data are presented on deuteron production in the target fragmentation region for 250 GeV/c π⁺ interactions with Al and Au nuclei, and compared with analogous data on proton production. Indications are observed for narrow structures in the (dπ^-) effective mass system at ～2.04 and ～2.08 GeV.     

High transverse momentum π0 production by π− and π+ on protons at 280 GeV/c

The inclusive cross sections for π⁰ production by π^? and π⁺ on protons have been measured with a beam momentum of 280 GeV/c using a fine grained electromagnetic calorimeter and the CERN Omega spectrometer. The transverse momentum and Feynmanx _F ranges covered are 4.0<p _T <7.0 GeV/c and ?0.45<x _F <0.6 respectively. The data are compared with leading order QCD calculations.     

High transverse momentumη production in π− p, π+ p,andpp interactions at 280 GeV/c

The inclusive cross sections for η production by the interactions of 280 GeV/c momentum π^?, π⁺, and proton beams in hydrogen have been measured. The kinematical range covered is ?0.45<x _F <0.45, and 4.0<P _T <7.0 GeV/c for Feynmanx _F and transverse momentum respectively. The η to π⁰ cross section ratios are given for the three reactions. The ratio of π^? p to π⁺ p cross sections for η production in the above kinematic ranges is 1.22±0.08±0.11.     

Quasi-free interactions in (K−, π−) strangeness-exchange nuclear reactions at 0°

It is suggested that quasi-free (incoherent) processes dominate the hypernuclear spectra for (K^?, π^?) strangeness-exchange reactions on nuclei at 0° for momentum 900 MeV/c. With this hypothesis, the broad hump recently observed for nuclei from ¹²C to ⁴⁰Ca is fairly reproduced in location and shape, and total cross-sections are discussed.     

Pion bound states in nuclei

Bound π-nuclear states can appear under certain realistic conditions in finite nuclei. The best prospects are certain medium-weight nuclei with dense central regions and large neutron excess. Numerical illustrations are given for ¹⁶O, ²⁸Si, ³²Na and ²⁰⁸Pb with realistic parameters for the interaction. Further, we show that the usual low-energy π nuclear potential develops pathological features like an infinity of bound states beyond a certain critical strength. The natural remedies are indicated.     

Observation of the (π−, π−n) and (π+, π+p) reactions at 165 MeV

The (π^?, π^?n) and the (π⁺, π⁺p) reactions were studied on C, Fe, and Bi at 165 MeV by coincidence measurement o outgoing particles. The nucleon-knockout reaction is the dominant inelastic process at backward pion-scattering angles at this energy. The quasifree (π^?, π^?n) and (π⁺, π⁺p) cross sections were determined from the π-N an correlations. Their σ_qf(π^?, π^?n)/σ_qf(π⁺, π⁺p) ratio is consistent with unity for C and is larger than the N/Z ratio for the heavier nuclei.     

Analysis of elastic scattering of pi-mesons by nuclei within the microscopic optical potential

The microscopic pion-nucleus optical potential defined by the pion-nucleon scattering amplitude and the density distribution function of the target nucleus is applied to obtain the differential cross section of the elastic pion-nucleus scattering based on the solution to the relativistic wave equation. This allow one to account for effects of the relativization and distortion by the potential field. Data on π^±-meson scattering on ²⁸Si, ⁵⁸Ni, and ²⁰⁸Pb nuclei at T _lab = 291 MeV are analyzed and the parameters of the in-medium πN-amplitude are obtained. The parameters are compared with similar parameters for scattering on free nucleons.     

Coherent production of π+ mesons in ν-neon interactions

The coherent production of π⁺ mesons by charged current neutrino interactions on neon nuclei in BEBC is compared to the predictions of the PCAC hypothesis and the meson dominance model. Good agreement is observed.     

New limits on Primakoff production of hybrid mesons

I discuss constraints on properties of isoscalarJ ^PC =1^?+ exotic hybrid mesons, assuming their dominant decay mode is ηπ. This work expands on a similar study by the Rochester-Minnesota-Fermilab collaboration, which excluded ?π as the dominant decay channel for such hybrids. The experimental limits are based on Primakoff production of such states and on a VDM argument relating their radiative widths to their ?π decay modes. Using data on coherent production of ηπ⁺ systems in π⁺ collisions with nuclei, I obtain few percent limits on the ?π branching ratios for hybrid masses ?1.5 GeV.     

Analisis of inelastic scattering of π-mesons from nuclei within the microscopic optical potential

Cross sections of inelastic scattering of π-mesons from Si, Ni, and Pb nuclei at energy T _lab = 291 MeV are calculated using the distorted wave approximation. The microscopic direct and transition optical potentials are determined by specifying the pion-nucleon scattering amplitude and the nuclear density distribution, where we use the in-medium πN amplitude parameters obtained earlier by analyzing the elastic scattering data for the same nuclei. The cross sections are calculated on the basis of the relativistic wave equation. The deformation parameters of the nuclei are obtained by comparing inelastic scattering cross sections with the appropriate experimental data.     

Half-lives of the Tz=1/2 series nuclei, 81Zr and 85Mo

Excited states with spin larger than 5 were newly established in the ¹³²Cs nucleus via the ¹²⁴Sn(¹¹B,3n) reaction. Rotational bands built on the νh_11/2 ? πd_5/2, νh_11/2 ? πg_7/2 and νh_11/2 ? πh_11/2 configurations were observed up to spin I ～ 16. The νh_11/2 ? πh_11/2 band shows inverted signature splitting below I < 14. A dipole band was firstly observed in doubly odd Cs nuclei.     

Search for superdense nuclei of Rb and Cs among the products of 8 GeV proton interactions with Ta

Experimental searches for β-active superdense nuclei of Rb and Cs among the products of 8 GeV proton interactions with Ta are described. The method of selective off-line mass-separation with scanning of the β-activity distribution on the collector was used. According to π-condensation theory, the long-lived anomalous nuclei are expected to be more neutron-deficient than the usual ones. Moreover, their mass numbers may be significantly nonintegral measured on the normal mass scale, because of unusual binding energy. These predictions guided the present search. No anomalous nuclei were found. The upper limit for Rb nuclei in the range 69 ? A ? 78 is 10^?5 with respect to the yield for ⁸¹Rb; for Cs in the range 112 ? A ? 122 the limit is (5–10) × 10^?6 of the yield for ¹²⁷Cs. These estimations are based on the assumption that the half-life of superdense nuclei equals 5 h.     

Factorial moments and correlations in meson-nucleus interactions at 250 GeV/c

A sample of 8000 interactions of 250 GeV/c π⁺ andK ⁺ mesons on Al and Au nuclei, is used to search for intermittency effects by calculating the normalized factorial moments of order two to four. No significant effect is observed in the higher moments. Two-body rapidity correlations and Bose-Einstein correlations in these interactions are presented.     

The threshold photoproduction of π0 on nucleons and on few-nucleon systems

The absolute value of the π⁰ photoproduction cross section on the proton recently measured near threshold enables to reanalyze previous data collected on ²H, ³He, and ⁴He relatively to the proton. Absolute cross sections are presented for these nuclei in the energy region extending up to 10 MeV above threshold. The threshold s-wave amplitudes for ²H and ³He thus obtained are discussed in relation with the neutron threshold amplitude E^(nπ0)₀₊ value.     

Vector analyzing power of π+7Li scattering in the region of the Δ33 resonance

Within Glauber diffraction theory, the vector analyzing power iT ₁₁ is calculated at three energies of positively charged pions, 134, 164, and 194 MeV, incident to ⁷Li nuclei. These energy values lie in the region of the Δ₃₃ resonance in π^± N interaction, the resonance maximum being at 180 MeV. The calculation of iT ₁₁ was performed with several model ⁷Li wave functions, including the αt-cluster and shell-model ones. The properties of π⁺⁷Li scattering are found to be sensitive to the structural features of the target nucleus. A comparison of the results of the calculations with experimental data shows that the wave functions in question and the potentials used to calculate them are quite appropriate.     

Photoproduction of ϱ′(1.2) and ϱ′(1.6) in the final states π+ π− π+ π− and π+ π− π0 π0

The elastic photoproduction of four pions has been studied at incident photon energies between 2.8 and 4.8 GeV. Production cross-sections are presented and an analysis of the angular decay correlations is also described, indicating a large 1^? contribution in both final states, π⁺ π^? π⁺ π^? and π⁺ π^? π⁰ π⁰. A quantitative understanding of these and other available 4π photoproduction data in terms of the ρ′(～1.2GeV) and the ρ′(～1.6) is presented.     

Delta-isobar configurations in 12C and 16O nuclei

The differential yield of the reaction ¹⁶O(γ, π ⁺ p) at the maximum photon energy of 450 MeV was measured in the region of high momentum transfers to the residual nuclear system. The experimental results obtained for the ¹⁶O nucleus and the cross section measured earlier for the reaction ¹²C(γ, π ⁺ p) were analyzed on the basis of a model that takes into account the admixture of isobar states in the nuclear wave function. The probabilities for the delta-isobar configurations in the ground states of the carbon and oxygen nuclei per nucleon were estimated empirically at 0.012 ± 0.003 ± 0.002 and 0.019 ± 0.003 ± 0.003, respectively.