Lambda polarization in the K− fragmentation region

Results on Λ polarization in the inclusive reaction K^?p→Λ + X at 12 and 16 GeV/c for 0.6<x<1.0, are presented. These results, obtained with the CERN Omega Spectrometer, show that the polarization is important at large x and increases with p_t over the covered range 0<p_t<1.2 GeV/c. The average polarization for 31 857 lambdas with x>0.6 is P_Λ = 0.35 ± 0.02, along the direction $\text{K}{}^{\mathrm{?}}\text{×}\text{Λ}$. The polarization can be expressed as P(x, p_t) = (0.66±0.03)p_t independent of x in the range covered by the experiment.     

Evidence for two narrow pp resonances at 2020 MeV and 2200 MeV

From the study of the reaction $\text{π}{}^{\mathrm{?}}\text{p→p}{}_{\mathrm{F}}\text{p}\text{p}\text{π}{}^{\mathrm{?}}$ using a fast proton (p_F) trigger device in the CERN Omega spectrometer, we find evidence for two narrow $\text{p}\text{p}$ states produced mainly in association with a Δ° (1232) and a N° (1520). The statistical significance of each peak is greater than 6 standard deviations. Masses and natural widths of these resonances are respectively M = 2020 ± 3 MeV, Λ₁ = 24 ± 12 MeV and M₂ = 2204 ± 5 MeV, Λ₂ = 16_?16⁺²⁰ MeV. Our data are consistent with a small production of the narrow ～ 1935 MeV resonance already reported. Production cross sections for these new $\text{p}\text{p}$ resonances are given.     

Evidence for narrow bound states related to the pp system

The γ-ray spectrum accompanying the p$\text{p}$ annihilation at rest has been measured with a large NaI(Tl) spectrometer. Three γ-lines have been observed with energies of 183 ± 7 MeV, 216 ± 9 MeV, and 420 ± 17 MeV at confidence levels of 99.0%, 97.5%, and 98.2%, respectively. The width of the lines corresponds to the detector resolution.     

Observation of a narrow pp enhancement at 1940 MeV

A narrow enhancement is observed in $\text{p}\text{p}$ states produced inclusively in proton-proton interactions at 93 GeV. The mass 1940 ± 1 MeV is consistent with that of the S(1936).     

Inelastic electron scattering from 31P

Form factors for the electroexcitation of the $\text{3}\text{2}$⁺ (1.27 MeV), $\text{5}\text{2}$⁺ (2.23 MeV), and $\text{3}\text{2}$⁺ (3.51 MeV) states in ³¹P have been measured for momentum transfers from 0.36 to 0.80 fm^?1 at the NBS electron scattering facility. In addition, form factors for the 2.23 MeV state in the momentum transfer range 0.74 to 1.78 fm^?1 have been extracted from data obtained in a previous experiment. Using the DUELS distorted-wave code the B(E2, ω) ↓ were found to be 6.0 ± 0.9, 6.9 ± 0.3, and 2.7 ± 0.3 W.u. for the 1.27, 2.23, and 3.51 MeV states, respectively. The form factors for these states, calculated using wave functions derived in an intermediate-coupling vibrational calculation, are compared with the data.     

Isospin-forbidden particle decays in light nuclei: (II). Widths of T = 32 levels of 17O

The lowest four $\text{T =}\text{3}\text{2}$ levels of ¹⁷O have been observed as resonances in the ¹³C(α, n)¹⁶O reaction. Excitation energies and widths obtained for these levels are 11.076 ± 0.005 MeV, Γ_c.m. = 5.0 ± 1.1 keV; 12.458 ± 0.005 MeV, Γ_c.m. = 8 ± 2 keV; 12.944 ± 0.006 MeV, Γ_c.m. = 6 ± 2 keV; 12.993 ± 0.006 MeV, Γ_c.m. < 3 keV. The total and partial decay widths for the lowest $\text{T =}\text{3}\text{2}$ level are much larger than those of the analogue level in ¹⁷F, implying significant isotensor components in the $\text{T =}\text{1}\text{2}$ admixtures.     

Spin-parity of the Σ(1580)

A resonance with spin parity $\text{3}\text{2}{}^{\mathrm{?}}$ is observed in K^?p→Λπ with mass 1582±4 MeV, width 11±4 MeV and amplitude at resonance 0.10±0.02.     

Some studies of T = 32 states in 17F

Measurements have been made of some parameters of the second and sixth $\text{T =}\text{3}\text{2}$ states in ¹⁷F. For the second state, the resonance energy was found to be E_p = 12.707 ± 0.001 MeV (E_n = 12.550±0.001 MeV), which agrees with and improves on the accuracy of earlier work. For the sixth $\text{T =}\text{3}\text{2}$ state, at E_p = 14.435 MeV, the γ-decay was determined to be predominantly γ₀ with a branch to the first excited state of Γ(γ₁)/Γ(γ₀) ≦ 0.14. Together with other work, this determines J^π to be $\text{3}\text{2}{}^{\mathrm{?}}$. The capture strength is found to be (2J + 1)Γ_pΓ_γ/Γ = 11.4 ± 2.6 eV.     

Isomers in the N = 83 nucleus 149Dy

Energy levels in the N = 83 nucleus ¹⁴⁹Dy were studied by the reaction ¹⁵²Gd(α, 7n) at 106 MeV bombarding energy using in-beam γ-ray spectroscopy methods. The measurements identified three isomers in this nucleus, at 1073 keV (13 ± 3 ns), at 2700±150keV (5 μs < T_{$\text{1}\text{2}$} < 0.5 s), and above 3.5 MeV (50 ± 15 ns). The low-lying isomer is interpreted as i_{$\text{13}\text{2}$}. The configuration $\text{27}\text{2}$^?(πh_{$\text{11}\text{2}$}²)₁₀₊ ×vf_{$\text{7}\text{2}$} is suggested for the state at 2.7 MeV.     

Observation of a narrow resonance near the pp threshold

Annihilation and elastic cross-sections of $\text{p}$p have been measured between 400 and 850 MeV/c. In both cross-sections a resonance is observed at a mass of 1939 ± 3 MeV. For its natural width τ ? 4 MeV is obtained.     

Evidence for a narrow width boson of mass 2.95 GeV

In a search for resonances coupled to the $\text{p}$pπ^? system, we have studied π^?p interactions at 16 GeV/c giving a forward antiproton, using the Omega spectrometer at CERN. In the final states involving a $\text{p}$, p and π^? we observe a 5.6 (6.3) standard deviation enhancement in the $\text{p}$pπ^? mass spectrum at (2.95 ± 0.01) GeV with a width consistent with the resolution (σ = 15 MeV). The production cross section × branching ratio is estimated to be of the order 1 μb. The data are consistent with a resonance decaying partly via intermediate $\text{p}$p final states.     

Observation of a KK enhancement at 1.85 GeV in the reaction K−p → KKΛ at 8.25 GeV/c

In a high statistics $\text{(}\text{～150 eV}\text{μb}\text{)}$ bubble chamber experiment on K^?p interactions at 8.25 $\text{GeV}\text{c}$, the study of the reaction K^?p → KKΛ provides evidence for an enhancement in the KK system with a mass of (1850 ± 10) MeV and a width of (80_?30⁺⁴⁰) MeV. Its possible identification with the missing isosinglet of the 3^? nonet is discussed. A K¹$\text{K}$ decay mode is also observed.     

Accurate determination of the 13C-12C+n spectroscopic factor

We have measured ¹²C-¹³C elastic cross sections at 12 MeV between 40°–140° in 1° steps to ±1%. The observed oscillatory interference between Coulomb scattering and the neutron transfer process is analyzed using exact finite-range DWBA, and a model-independent value of C² = 2.55±0.10 for the asymptotic normalization of the $\text{1}\text{p}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ neutron wave function in ¹³C is obtained. Using radial wave functions determined by elastic electron scattering the spectroscopic factor is found to be S = 0.81±0.04.     

Proton-antiproton annihilations at rest into π0ω, π0η, π0γ, π0π0, and π0η′

Proton-antiproton annihilations at rest in liquid hydrogen were investigated through the inclusive γ spectrum, related to the annihilation. The high-energy part of the spectrum was used to deduce branching ratios for the so far unobserved annihilation channels: $\text{R(}\text{p}\text{p}\text{→π}{}^0\text{ω) = (2.38 ± 0.65)\%}$, $\text{R(}\text{p}\text{p}\text{→ π}{}^0\text{η) = (0.82 ± 0.10\%}$, $\text{R}\text{p}\text{p}\text{→π}{}^{\mathrm{0\gamma )}}\text{= (0.015 ± 0.007)\%}$, and $\text{R(}\text{p}\text{p}\text{→ π}{}^0\text{π}{}^0\text{= (0.06 ± 0.04)\%}$. An upper limit for the π⁰η^′ channel was deduced to be $\text{R(}\text{p}\text{p}\text{→ π}{}^0\text{η}{}^{\mathrm{\prime }}\text{) < 1.1\%}$.     

Isospin-forbidden particle decays in light nuclei: (I). T = 32 levels of 9Be, 9B

Absolute branching ratios have been measured for the isospin-forbidden nucleon decays of the lowest $\text{T =}\text{3}\text{2}$ levels of ⁹Be and ⁹B to the ground state and first excited state of ⁸Be. The $\text{T =}\text{3}\text{2}$ levels were populated by the ⁷Li(³He, n) and ⁷Li(³He, p) reactions. The subsequent decay products were observed in coincidence with the neutrons or protons, detected at 0°. Branching ratios of 0.028 ± 0.021 and 0.50 ± 0.11 were determined for the neutron decays of the 14.39 MeV, $\text{T =}\text{3}\text{2}$ level of ⁹Be to the ground state and 2.9 MeV, 2⁺ first excited state of ⁸Be, respectively. Branching ratios of 0.11 ± 0.04 and 0.33 ± 0.09 were determined for the analogous proton decays of the ⁹B, 14.67 MeV $\text{T =}\text{3}\text{2}$ level. The similarity of the decay properties of these analogue levels is in contrast to the large asymmetries observed for $\text{T =}\text{3}\text{2}$ levels in other A = 4N + 1 light nuclei.     

Search for substructure in pp total cross section in the 2200 MeV mass region

The $\text{p}$p total cross section was measured from 2130 to 2250 MeV with mass resolution 2.25 MeV (FW). No fine structure was found with σΓ above the statistical limit of 7 MeV mb. A spin J particle coupled to the $\text{p}$p system must have partial width less than $\text{1.8}\text{(2J+1)}$ MeV.     

The γ-decay of the 1g92 and 2p inner-hole states in 111Sn via the 112Sn(3He, αγ) reaction at 32 MeV

The γ-decay of the deeply-bound hole states in ¹¹¹Sn has been investigated at 32 MeV incident energy by means of the ¹¹²Sn(³He, αγ) reaction. The α-particles emitted near 0° were detected in a Si counter located at the image plan of the superconducting solenoidal spectrometer SOLENO. The γ-rays in coincidence with the α-particles were detected by two Ge(Li) detectors located at 90° and 142° with respect to the beam direction, respectively. Energies, spins and decay schemes have been established for the low-lying states up to 2.5 MeV excitation energy in ¹¹¹Sn. The γ-decay of the broad bump, located around 4.2 MeV and previously attributed to neutron pick-up from the inner $\text{1}\text{g}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}\text{, 2}\text{p}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{,}\text{and}\text{2}\text{p}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ neutron. Subshells, reveals the importance of quasiparticle-phonon m the spreading mechanism of the inner-hole strengths. The $\text{1}\text{g}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}$ and 2p strength functions have been deduced from the α-decay of the enhanced structures (3 ≦ E_x≦ 8 MeV). They are compared to the ones measured in previous inclusive neutron pick-up experiments and to those calculated in the framework of the quasiparticle-phonon nuclear model.     

Study of Kπ scattering using the reactions K±p → K±π+nand K±p → K±π−Δ ++at 13 GeV

An elastic Kπ partial-wave analysis is presented. It is based on high statistics data for the reactions $\text{K}{}^{\mathrm{\pm }}\text{p}\text{→}\text{K}{}^{\mathrm{\pm }}\text{π}{}^{\mathrm{+}}\text{n}\text{and K}{}^{\mathrm{\pm }}\text{p}\text{→}\text{K}{}^{\mathrm{\pm }}\text{π}{}^{\mathrm{?}}\text{Δ}{}^{\mathrm{++}}\text{at}\text{13}\text{GeV}$ obtained in a spectrometer experiment performed at SLAC. For each reaction, a t-dependent parametrization of the production amplitudes provides information on both the Kπ mass dependence of the production mechanisms and on Kπ scattering. Knowledge of the t-dependence then allows a calculation of the Kπ partial-wave amplitudes for Kπ masses from 0.7 to 1.9 GeV. The results of such analyses using data for (i) the neutral recoil reactions, (ii) the Δ⁺⁺ recoil reactions, and (iii) both neutron and Δ⁺⁺ recoil reactions simultaneously, are presented. Besides the leading J^P = 1^?, 2⁺, and 3^? resonances at M_Kπ = 0.896, 1.434, and 1.78 GeV, there is evidence in two of the four possible partial-wave solutions for a broad P-wave resonant-like structure in the region of 1700 MeV. The $\text{I =}\text{1}\text{2}$ S-wave magnitude rises slowly and smoothly to a maximum near 1400 MeV, but then decreases rapidly between 1400 and 1600 MeV. This structure is strongly indicative of an S-wave resonance near 1450 MeV. The charge-two Kπ reaction is dominated by S-wave scattering with a total cross section decreasing from 4 mb at 0.9 GeV to 2 mb at 1.5 GeV. Both the $\text{I =}\text{1}\text{2}$ S-wave below 1400 MeV and the $\text{I =}\text{3}\text{2}$ S-wave are well described by an effective range parametrization.     

Observation of proton emission following thermal neutron capture in 34.5 d 84Rb

Using a target prepared by on-line isotope separation, thermal neutron capture in ⁸⁴Rb (I^π = 2^?) has been shown to induce proton emission to the ground state (0⁺) and first excited state (2⁺) of ⁸⁴Kr. The branching ratio was measured as $\text{Γ}{}_{\mathrm{<mtext>p</mtext>}}\text{(0}{}^{\mathrm{+}}\text{)}\text{Γ}{}_{\mathrm{<mtext>p</mtext>}}\text{(2}{}^{\mathrm{+}}\text{)}\text{= 4.7 ± 0.7}$, favouring a $\text{3}\text{2}{}^{\mathrm{?}}$ assignment of the capturing state without excluding $\text{5}\text{2}{}^{\mathrm{?}}$, and the (n_th, p) cross section as 12 ± 2 b. The energy available for the process was determined to be 3.45 ± 0.01 MeV, in agreement with other mass data in the region.