Analysis of the K S K S system from the reaction π − p → K S K S n at 40 GeV

On the basis of experimental data from the 6-m spectrometer of the Institute of Theoretical and Experimental Physics (ITEP, Moscow), an amplitude analysis of 40 553 events of the reaction π ^? p → K _S K _S n induced by a negatively charged pion of energy 40 GeV is performed over a broad momentumtransfer range by using a new procedure. The results for |t| > 0.1 GeV² are obtained for the first time. In particular, resonances of mass 1700 and 1900 MeV and width 120 MeV are discovered in the D ₊ wave (there were no such resonances for |t| < 0.1 GeV²). In the region of low momentum transfers, the S wave exhibits a structure that lies in the mass region around 1370 MeV and which requires three resonances for its explanation. Two of these (that of mass 1234 ± 6 MeV and width 47 ± 33 MeV and that of mass 1478 ± 6 MeV and width 119 ± 10 MeV) were found in the studies of A. Etkin et al. [Phys. Rev. D 25, 2446 (1982)] and O.N. Baloshin et al. {Yad. Fiz. 43, 1487 (1986) [Phys. At. Nucl. 43, 959 (1986)]}. The third has a mass of 1389 ± 9 MeV and a width of 30 ± 24 MeV. At high momentum transfers, the S wave is found to feature resonances that have the following parameters: M = 1328 ± 8 MeV and Γ = 237 ± 20 MeV, M = 1440 ± 6 MeV and Γ = 121 ± 15 MeV, and M = 1776 ± 15 MeV and Γ = 250 ± 30 MeV. For the D ₀ wave, it is found that, in addition to the well-known resonances f ₂, a ₂, and f′ ₂, there appear the following resonances in this wave: a resonance of mass 2005 ± 12 MeV and width 209 ± 32 MeV and a resonance of mass 2270 ± 12 MeV and width 90 ± 29 MeV at low |t| and a resonance of mass 1659 ± 6 and width 152 ± 18 and a resonance of mass 2200 ± 13 MeV and width 91 ± 62 MeV at high |t|.     

Investigation of the reaction 35Cl(τ, α)34Cl at Eτ = 15 MeV

The ³⁵Cl(τ, α)³⁴C reaction has been used to study the properties of ³⁴Cl levels up to an excitation energy of 5 MeV. Angular distributions of 37 levels were measured with a split-pole magnetic spectrograph, at a bombarding energy of 15 MeV. New levels have been found at 3847, 3964, 4206, 4321 and 4715 keV, all ± 10 keV. There is a strongly excited multiplet at E_x = 5.0 MeV with components at 4939 ± 11, 4958 ± 11, 4971 ± 11, 4998 ± 12 and 5010 ± 13 keV. A DWBA analysis of the α-particle angular distributions yielded l_n values and spectroscopic factors. New spin and parity assignments were obtained. The T = 1 character of the levels at E_x = 4.21 and 4.72 MeV has been determined. Experimental spectroscopic factors are compared with results from recent many-particle shell-model calculations.     

High-resolution (e,e') study of isovector M1 and M2 transitions in the oxygen isotopes: (I). 16O

The M1 and M2 transition strength distribution for ¹⁶O in the excitation energy range from 16 to 20 MeV has been measured in a high-resolution electron scattering experiment. The M1 strength is concentrated in three sharp states at E_x = 16.22, 17.14 and 18.79 MeV (± 0.01 MeV) with B(M1, k)↑ = 0.20 ± 0.02, 0.32 ± 0.03 and 0.13 ± 0.03 μ_N², respectively. An additional strength of 0.35 ± 0.09 μ_N², distributed over eight weakly excited states with excitation energies E_x = 17.4 to 18.0 MeV, brings the total measured M1 strength to B(M1, k)↑ = 1.0 ± 0.1 μ_N². The experimental M2 strength is distributed over states at E_x = 16.82, 17.78, 18.50 and 19.0 MeV (± 0.01 MeV) with B(M2, k)↑ = 19 ± 2, 13 ± 2, 59 ± 7 and 341 ± 51 μ_N² · fm², respectively. Electric transitions were also measured to states at E_x = 16.45 MeV (2⁺, E2), 17.30 MeV (1⁺, E1) and 18.20 MeV (2⁺, E2). Calculations were performed using the modified surface delta interaction in a 2p-2h shell model for the M1 transitions and the random phase approximation for the M2 transitions. The results show the sensitivity of the M1 strength as a measure of ground-state correlations and compare well with results from the ¹⁵N($\text{p}$, γ) reaction.     

Analysis of the Kω spectrum

We present results of a spin-parity analysis of the Kω system from threshold to 1.52 MeV based on 12 500 events of the type K^?p→K^?π⁺π^?π^op at 7.3 GeV/c. We also present evidence for a possible resonant state decaying into Kω at a mass 1710 ± 15 MeV and width 110 ± 50 MeV.     

Elastic scattering of15N on19F,19F on18O and19F on16O at low energies and elastic transfer

The reduced matrix elements for the ground state transitions to the first 2⁺, 3^? and 4⁺ states in¹⁴⁰Ce and¹⁴Ce were determined by DWBA analysis. In the giant resonance region of Ce, La and Pr three broad resonances at excitation energies of 9, 12 and 15 MeV have been found. They are interpreted asM1,E2 andE1 giant resonances. For Ce the total widths are (2.2±0.4) MeV (M1) and (2.8±0.3) MeV (E2) and the groundstate radiative widths (90±45) eV (M1), (100±30) eV (E2) and (5±1) · 10⁴ eV (E1).     

Search for 4H, 5H and 6H nuclei in the 11B-induced reaction on 9Be

In the reaction ¹¹B(88.0 MeV) + ⁹Be the energy spectra of the ¹⁴O, ¹⁵O and ¹⁶O nuclei have been measured to obtain some information about their partners in the exit channel — the neutron-rich hydrogen isotopes ⁴H, ⁵H and ⁶H. The unbound levels in the ⁴H and ⁶H systems have been observed at excitation energies of 3.5 ± 0.5 MeV (Γ ~1 MeV) and 2.6 ± 0.5 MeV (Γ = 1.5 ± 0.3 MeV), respectively. No evidence for the existence of any bound or unbound state in ⁵H has been found.     

Der Zerfall des In109m (0,21 sec)

In^109m(0,21±0,01 sec) was produced from natural Ag and enriched Ag¹⁰⁷ byα irradiation and investigated using scintillation spectrometers and coincidence techniques. The mass assignment follows from the excitation function for the (α, 2n) reaction on Ag¹⁰⁷. The following results were obtained: energy of the isomeric level (2,11±0,02) MeV, determined directly by summing up the cascade transitions in a well-type scintillator; four gamma transitions with energies (0,680±0,015) MeV, (0,405±0,015) MeV, (1,035±0,030) MeV and (1,435±0,020) MeV, respectively. The proposed decay scheme contains the isomeric level (19/2⁺) at 2,11 MeV and a further level (13/2⁺) at 1,435 MeV which decays either by the 1,435 MeV transition (80±3)% or by a 0,405–1,035 MeV cascade (20±3)% via an (11/2⁺) level at 1,035 MeV to the 9/2⁺-ground state of In¹⁰⁹.     

Differential cross section for elastic π± helium isotopes scattering from 25 to 65 MeV

Measurements of absolute elastic-scattering differential cross sections for π^±He at T^lab_π = 30.2 MeV, 45.1 MeV and 65.0 MeV and for π^±-⁴?⁴He at T^lab_π = 25.1 MeV and 51.1 MeV have been made in the angular range 40° to 145°. An overall accuracy of about ±5% was achieved. The results are compared with available theoretical calculations.     

Unelastische Elektronenstreuung an14N für Anregungsenergien zwischen 8,5 und 11,5 MeV

¹⁴N was investigated by inelastic scattering of 35... 58 MeV electrons (scattering angles 117 to 165°). For theM1-transitions to the 2⁺,T=1 levels at 9.17 and 10.43 MeV, ground state radiation widths of (7.7±0.9) eV, and (12.1±1.5) eV, respectively, were obtained. The ratio of these two widths is 1.57±0.07. The 3^?,T=1 level at 8.90 MeV is excited by anM2-transition withΓ _γ ⁰ =(6.6±2.2) · 10^?3 eV. An excitation of a level at (11.01±0.07) MeV is observed.     

The mass of 15B via a three-proton stripping reaction

The isotope ¹⁵B was produced via the reaction ⁴⁸Ca(¹⁸O, ¹⁵B)⁵¹V. The Q-value and mass excess were determined to be ?21.76 ± 0.05 MeV and 28.96 ± 0.05 MeV, respectively. A search for the isotope ¹⁴Be was unsuccessful.     

Mean lifetimes of levels in 55Co

The mean lifetimes of levels in ⁵⁵Co below 5.2 MeV have been investigated with the Doppler-shift attenuation method and the ⁵⁴Fe(³He, d)⁵⁵Co reaction at 12 MeV. Scattered particles were detected in two E-ΔE telescopes at ±55° with respect to the beam axis, in coincidence with γ-rays observed at 90° and 130° in a 50 cm³ Ge(Li) detector. Mean lifetimes are reported for the following levels (energy in keV, lifetime in fs): 2166 (139±18), 2566 (680±200), 2923 (>245), 2939 (190±65), 3303 (99±22), 3323 (54±15), 3642 (680_?300⁺⁴⁰⁰), 3943 (>170), 4164 (54±15), 4180 (<16), 4722 (<33), 4749 (<70) and 5174 (<40). The experimental results are compared with a detailed shell-model calculation.     

The gamma-decay of34Ar

States in³⁴Ar up to 5.5 MeV excitation energy, populated by the³²S(³He,nγ) reaction at 8–12 MeV bombarding energy, have been investigated with the Doppler shift attenuation method,nγ angular correlation andnγγ triple coincidence measurements. For the states at 2.09, 3.29 and 4.52 MeV the lifetimes 200±60 fs, 130±60 fs and 260±80 fs have been found, respectively. Thenγ correlations yielded the spin assignmentsJ ^μ=(2⁺) for the level at 4.13 MeV andJ ^μ=3^? for the 4.52 MeV state, and the mixing ratiosδ(3.29→2.09)=?0.12±0.05 andδ(4.13→3.29)=?0.52±0.15. The results are compared with shell model calculations and predictions from the weak coupling unified model.     

A study of excited states of5He by the7Li (d, α)5He-reaction

The interactions of deuterons with⁷Li, in which two α-particles and a neutron are produced in the final state are studied atE _d =1.2 MeV. The dual parameter α-α coincidence spectrum was analyzed with a search program. The results indicate two excited states of⁵He: One at excitation energy 2.9±0.1 MeV and with a reduced width of γ²=1.1±0.4 MeV, and the other at 4.8±0.4 MeV, with γ²=0.9±0.4 MeV. No contributions of sequential decay through the 4⁺ state in⁸Be or direct three body decay was observed.     

A study of the 99Tc(p,d)98Tc reaction

The energy levels of ⁹⁸Tc were studied with the ⁹⁹Tc(p, d)⁹⁸Tc reaction at a bombarding energy of 22.9 MeV and 15 keV resolution (FWHM). The Q-value for this reaction was found to be ?6.755 ± 0.009 MeV and the ⁹⁸Tc mass excess was calculated to be ?86.421 ± 0.011 MeV. This reaction provided the excitation energies for 49 neutron hole states below 1.5 MeV excitation. Comparison of experimental angular distributions with DWBA calculations permitted assignment of lf-values and the extraction of spectroscopic factors for 44 of these levels. Extensive configuration mixing is observed except in the low-lying multiplet. Effective proton-particle, neutron-hole interaction matrix elements were obtained from the low-lying positive-parity multiplet of ⁹⁸Tc.     

Lifetimes and branching ratios of excited states of 24Na

The decay of ²⁴Na levels below 4.3 MeV excitation was studied by means of the ²³Na(d, pγ)²⁴Na reaction at E_d = 2.45 MeV. Gamma-ray spectra were measured at three angles, in coincidence with proton groups detected around 180°. Excitation energies, branching ratios and Doppler shifts were determined. Mean lives were obtained for the levels at 1341 keV (62±15 fs), and 1846 keV (200±50 fs). The 1347 keV level has τ >3 ps. For other levels above 1 MeV upper limits of ≈ 60 fs are set. In some cases spin restrictions follow. In particular J = 2 is assigned to the 1341 keV level.     

Observation of the two-photon decay of a light penetrating particle

Coincident two-photon events, emerging from a 2 m long decay region, and pointing back to the SIN 590 MeV proton beam dump were detected in a thin-foil optical spark chamber. There was a significant excess of photons at small angles (<7°): 19 were observed, whereas (2.0 ± 0.5) were measured with cosmic rays, and additional (2.5 ± 1.0) were accelerator background. The visible γ-ray energies were estimated by multiple scattering to be 〉E_γ1〈 = (83 ± 20) MeV, 〉E_γ2〈 = (84 ± 15) MeV. The invariant 2γ mass is < 1 MeV. The 2γ event rate did not change significantly, when a 20 cm thick iron wall was placed in front of the decay region, but vanished with the wall put at its end. Presumably a light boson χ⁰ comes from the beam dump, penetrates the shielding, and decays: χ⁰ → 2_γ The measured rate of (14.5 ± 5.0) events in 129 Coulomb fixes a combination of production cross section and life-time. If the new boson χ⁰ was the axion, one can solve for the Higgs parameter X = 3.0 ± 0.3, and infer τ_a ≈ 7 ms, and m_a = (250 ± 25) keV.     

Energieverteilung und Wirkungsquerschnitt der Photoprotonen aus N15

The energy spectra of photo protons from highly enriched N¹⁵ were investigated with the bremsstrahlung from the Heidelberg betatron running at six different endpoint energies between 19 and 30.5 MeV. The protons were detected at 90° to theγ-beam by means of a CsJ-spectrometer with pulse shape discrimination. The energy spectra show pronounced maxima atE _p =3.2; 4.6; 9.5 and 13.3 MeV. Proton yields are given as a function of endpoint energy, the yield value atE ₀=30.5 MeV being (7.0±0.8) μb/MeV · ster. Because the first excited state in the daughter nucleus C¹⁴ lies 6.09 MeV above the groundstate, the cross section for groundstate transitions of the process N¹⁵(γ, p)C¹⁴ could be derived from the upper 6 MeV of the single proton spectra. The main contribution to the cross section comes from the region between 18 and 26 MeV excitation energy with maxima at 19.5; 20.4; 22.7 and 24.5 MeV. A “pygmy resonance” occurs at 15.2 MeV with further less pronounced structures at 13.6 and 17.0 MeV. The integrated cross section for groundstate transitions up to 30.5 MeV is (22±3) MeVmb assuming isotropic angular distribution. The ratios of protons from transitions to excited states and from the (γ, n p)-reaction to those of groundstate transitions rise from 0.45 atE ₀=24.5 MeV to 0.70 atE ₀=30.5 MeV.     

New measurements of the masses of 15B and 19N

The neutron-rich nuclei ¹⁵B and ¹⁹N have been produced in reactions between ¹⁸O and ⁴⁸Ca. Mass excesses of 28.968 ± 0.025 MeV and 15.872 ± 0.020 MeV respectively were deduced from the reaction Q-values. These results are compared with previous measurements and theoretical predictions. Updated predictions using two different mass formulae are presented.     

Copper ion induced reactions on110-108-106Cd,109-107Ag and110Pd. new rhenium,osmium and iridium isotopes

By⁶³Cu induced reactions on¹¹⁰Cd,¹⁰⁸Cd,¹⁰⁶Cd,¹⁰⁹Ag,¹⁰⁷Ag and¹¹⁰Pd targets, new isotopes were searched in the Ir, Os, Re region. Cross bombardments and excitation function measurements were used to identify newα emitting isotopes:¹⁷⁰Ir (E _α = 6.01 ±0.01 MeV?T _1/2=1.1±0.2s),¹⁶⁹Ir (E _α =6.11±0.01 MeV?T _1/2=0.4±0.1 s),¹⁶⁸Ir (E _α =6.22±0.02 MeV,¹⁶⁸Os (E _α =5.66±0.01 MeV?T _1/2=1.9±0.1 s),¹⁶⁷Os (E _α =5.84 ±0.01MeV ?T ^1/2=0.65±0.15s),¹⁶⁶Os (E _α =6.00±0.02 MeV?T _1/2=0.3 ±0.1 s),¹⁶⁵Os (E _α =6.20±0.02 MeV),¹⁶⁹Re (E _α =5.05±0.01 MeV),¹⁶⁸Re (5.26±0.01 MeV?T ^1/2=5.5 ±0.5 s). Theα-decay measurements are compared to theQ _α values obtained from different mass predictions.     

Measurements of the radiative widths of the first T = 1, 2+ state of 20Ne and their relationship to analog β-decays

The radiative widths for decays of the ²⁰Ne T = 1, 2⁺ (10.27 MeV) state were measured by resonance α-capture in the reaction ¹⁶O(α, γ)²⁰Ne. A special windowless gas-cell target yielded a low-background spectrum enabling six γ-branches to be observed with a Ge(Li) detector. The six branches correspond to decays from the 10.27 MeV level to the following levels: 2⁺(7.83 MeV), 2⁺(7.42 MeV), 3^?(5.62 MeV), 2^?(4.97 MeV), 2⁺(1.63 MeV) and 0⁺(g.s.). The branching ratios and radiative widths Γ_γ to these levels are: 7.83 MeV [(0.22 ± 0.06)%, 0.008 ± 0.002 eV], 7.42 MeV [(6.9 ± 0.4)%, 0.31 ± 0.04 eV], 5.62 MeV [(2.1 ± 0.2)%, 0.097 ± 0.014 eV], 4.97 MeV [(1.3 ± 0.1)%, 0.060 ± 0.008 eV], 1.63 MeV [(88.9 ± 0.5)%, 4.08 ± 0.43 eV] and 0.0 MeV [(0.64 ± 0.14)%, 0.029 ± 0.008 eV]. The radiative widths to the 1.63 MeV and 7.42 MeV levels are used to determine the CVC predictions of the weak magnetism form factors and their effects on certain β-decay observables are evaluated.