Gamma-decay modes of Ne

The lifetimes of the 3376 and 3576 keV states in ¹⁸Ne have been investigated by the Doppler-shift recoil-distance method using the ¹⁶O(³He, n)¹⁸Ne reaction. The 3376 keV level has τ_m = 4.4 ± 0.6 ps and the 3576 keV level has τ_m < 6 ps. In addition the ground state branch of the 3616 keV level has been observed to be (12.5 ± 2.5) %. Furthermore it was found that δ(3616 → 1887) = +0.03 ± 0.09. These results are compared with theoretical predictions.     

Evidence for dipole-quadrupole-octupole mixing in the 902 keV 2 → 2 transition in W

From known conversion coefficients and angular correlations combined with the γ-ray decay deduced from the ¹⁸¹Ta(p, 2n¹⁸⁰W reaction it is found that the 1007 → 104 keV (2⁻ → 2⁺) transition in ¹⁸⁰W has mixing parameters δ₁ = −0.16 ± 0.07 and δ₂ = −0.64 ± 0.17 for M2/E1 and E3/E1, respectively     

Multipole mixing ratios of transitions in Te

Gamma-gamma directional correlation measurements were made on nine transitions in ¹²⁴Te with a NaI(Tl)-Ge(Li) detector arrangement and multichannel analysis. The multipole mixing ratios obtained were δ(646) = 0.000±0.001, δ(714) = 1.5_−0.3^+0.6, δ(723) = −3.3±0.2, δ(1437) = 3.7_−2.0^+2.7, δ(1489) = −3.4_−1.5^+0.9, δ(968) = −0.03_−0.05^+0.06, δ(1368) = −0.045±0.090, δ(1045) = 0.041_−0.041^+0.047, δ(1691) = −0.02±0.01, and δ(2091) = 0.00_−0.03^+0.02. The first δ is M3/E2, the next three are E2/M1, and the last five are M2/E1. The retardation (a factor of approximately 50) of the crossover to cascade transitions from the 2039 keV, third 2⁺ level to the second and first 2⁺ levels is essentially the same for both the M1 and E2 components. In addition, spin and parity assignments of 2⁺ were made for the 2039 and 2092 keV levels.     

The spin of the 1643 keV state and multipole mixing ratios of γ-transitions in Ba

Directional correlations of the ¹³⁴Ba γ-rays following the β-decay of ¹³⁴Cs have been measured using two high-resolution 30 cm³ coaxial Ge(Li) detectors. Particular attention was paid to the various corrections that must be applied in measuring γ-γ directional correlations in complex decays. It was clearly established that the spin-parity of the 1634 keV excited state of ¹³⁴Ba is 3⁺. The multipole mixing ratios (in the Krane-Steffen definition) of the ¹³⁴Ba γ-rays are (energies in keV): |δ(475)| = > 18, δ(563) = −7.4 ± 0.9, δ(569) = +0.29 ± 0.02, δ(1038) = 1.85 ± 0.15.     

ππ production by ee annihilation in the ϱ energy range with the Orsay storage ring

A large solid angle detector has been used to observe two body events produced by electron-positron collisions in the Orsay storage ring. From the π⁺π⁻ excitation curve in the ? region we have deduced the amplitude and the phase of the ω-? interference, and the ? resonance paramaters: M_? = (775.4±7.3) MeV, Γ_? = (149.6 ± 23.2) MeV, √B(ω→π⁺π⁻) = 0.19 ± 0.05, φ = (85.7 ± 15.3)⁰, σ(e⁺e⁻→?) = (1.00 ± 0.13) μb at S = M_?², B(?→e⁺e⁻ = (4.1 ± 0.5) × 10⁻⁵, Γ(?→e⁺e⁻) = (6.1 ± 0.7) keV, (g_?²/4π) = 2.26 ± 0.25, (g_?ππ²/4π) = 2.84 ± 0.50.     

Conversion-electron-gamma and gamma-gamma directional angular correlations in 160Dy

Gamma-gamma and conversion-electron-gamma angular correlations in ¹⁶⁰Dy have been measured for the 298 keV–966 keV and 298 keV–879 keV cascades. Particle parameters of the 966 keV E2 transition were determined to be b₂(E2; e_K) = +1.23±0.08 and b₂(E2; e_{ΣL + ΣM) = +1.27±0.23}. The multipole mixing ratio for the 298 keV radiation was determined to be δ(M2/E1) = +0.04±0.01 and we have confirmed the value δ(E2/M1) = ?13±2 for the 879 keV. The E0–E2 mixture parameter for the 879 keV transition was determined as q_K = ?0.03±0.09 assuming penetration effects to be negligible.     

Properties of the φ and f′ produced in the channel Kp → KpKK̄ at 10 GeV/c

Data are presented and cross sections given for ф and f′ production in the channel K⁺p → K⁺pKK? at 10 Gev/c. The resonance parameters obtained from a fit to the KK? effective mass distribution are M = (1020.4 ± 0.5) MeV/c² and Γ = (5.0 ± 1.3) MeV/c² for the ф meson and M = (1514 ± 4) MeV/c² and Γ = (28 ± 15) MeV/c² for the f′. The resonance widths are corrected for experimental resolution. The branching fraction for the rate (ф → K⁰₁K⁰₂)/(ф → K⁺K⁻) is determined to be 1.15 ± 0.15. The angular distributions for the decay of the f′ have unnormalized moments _H(2,0) and H(4,0) different from the values for the nearby background, indicating spin 2 or greater for the f′.     

ρ-ω mixing in J/ø→VP decays

The study of ρ-ω mixing has mainly focused on vector meson decays with isospin I=1, namely the ρ(ω)→π⁺π^- process. In this paper, we present a study of ρ-ω mixing in ρ(ω)→π⁺π^-π⁰ (I=0) using a flavor parameterization model for the J/ø→ VP process. By fitting a theoretical framework to PDG data, we obtain the SU(3)-breaking effect parameters s_V=0.03±0.12, s_P=0.17±0.17 and the ρ-ω mixing polarization operator ∏_ρω=(0.006±0.011) GeV². New values are found for the branching ratios when the mixing effect is incorporated: Br(J/ψ→ ωπ⁰) = (3.64 ±0.37)×10^-4, Br(J/ψ→ ωη) = (1.48 ±0.17)×10^-3, Br(J/ψ→ ωη') = (1.55±0.56)×10^-4, these are different from the corresponding PDG2012 values by 19%, 15% and 15%, respectively.     

Multipole mixing ratios of γ-transltions in 182W

γ-γ directional correlation experiments were performed on 14 cascades in ¹⁸²W populated from the β^? decay of ¹⁸²Ta(115 d). Two Ge(Li) detectors were used in a coincidence arrangement, and the ¹⁸²Ta sources were dissolved in HF acid to minimize extranuclear perturbations. For the 1189keV, 2^? → 2⁺ transition, the measured directional correlation coefficients are consistent only with multipole mixing ratios $\text{δ}\text{(}\text{M}\text{2}\text{E}\text{1)}\text{= 0.45 ± 0.03}\text{and}\text{δ}\text{(E3}\text{E1)}\text{= ?0.67 ± 0.07}$. These mixing ratios are discussed and compared with the known conversion coefficients for the 1189keV transition. The E2/M1 multipole mixing ratios determined are (energy in keV): δ(66) = 0.15 ± 0.15, δ(85) = 0.31 ± 0.05, δ(114) = 0.31 ± 0.05, 0.56 ≦ δ(179) ≦ 1.36, δ(1121) = 12⁺²_?1, and δ(1231) = ?(32⁺¹⁴²_?15). The measured M2/E1 mixing ratios are: δ(68) = 0.03 ± 0.02, δ(152) = 0.014 ± 0.013 and δ(156) = ?0.13 ± 0.19.     

Nuclear orientation study of the excited states of 129I populated in the decay of 129gTe and 129mTe

From the angular distributions of γ-rays emitted by oriented ^129gTe and ^129mTe nuclei implanted in iron by isotope separator, unique spin assignments could be made for the excited states of ¹²⁹I at 487.4 keV $\text{(}\text{5}\text{2}{}^{\mathrm{+}}\text{)}$, 696.0 keV $\text{(}\text{11}\text{2}{}^{\mathrm{+}}\text{)}$, 729.6 keV $\text{(}\text{9}\text{2}{}^{\mathrm{+}}\text{)}$, 768.9 keV $\text{(}\text{7}\text{2}{}^{\mathrm{+}}\text{)}$, 1050.4 keV $\text{(}\text{7}\text{2}{}^{\mathrm{+}}\text{)}$ and 1111.8 keV $\text{(}\text{5}\text{2}{}^{\mathrm{+}}\text{)}$. In addition, E2/M1 amplitude ratios for the following ¹²⁹I γ-rays (energies are in keV) are derived: δ(459.6) = ?(0.076^+0.037_?0.148); δ(487.4) = 0.50^+0.17_?0.10 or δ^? = 0.35^+0.15_?0.09; δ(556.7) = 0.06±0.02 or δ^? = ?(0.10±0.02); δ(624.4) = 0.10±0.26 or δ^? > 0.4; the 696.0 keV γ-ray is pure E2; δ(729.6) = ?(0.34±0.06) or δ^?1 = 0.55±0.05; δ(741.1) = ?(0.27±0.10) or δ^?1 = ?(0.43±0.12); δ(817.2) = 0.46±0.04 or δ^?1 =0.20±0.03 if $\text{I}{}^{\mathrm{\pi }}\text{(845}\text{keV}\text{) =}\text{7}\text{2}{}^{\mathrm{+}}$; δ(1022.6) = ?(0.02 ±0.02) or δ^?1 = ?(0.23±0.02); $\text{δ(1084) = 0.56}{}^{\mathrm{+0.04}}{}_{\mathrm{?0.14}}$; δ(1111.8) = 0.06±0.05 or δ^?1 = ?(0.08±0.05). The anisotropy of the 531.8 keV γ-ray excludes $\text{1}\text{2}{}^{\mathrm{+}}$ as a possible spin assignment for the 559.6 keV level, so that no $\text{1}\text{2}{}^{\mathrm{+}}$ level is fed in the decay from ¹²⁹Te. Anisotropies for the 209, 250.7, 278.4 and 281.1 keV γ-rays are also measured. Comparison of the level scheme is made with theoretical predictions from both the pairing-plus-quadrupole model and the intermediate coupling unified model.     

Angular correlation measurements in 131Xe

An experiment is described determining the angular correlations of five γ-γ cascades in ¹³¹Xe appearing in the decay of ¹³¹I. Using a 12-channel goniometer the following results were obtained: 325.8–177.2 keV, A₂ = 0.018(11), A₄ = ?0.003(10); 318.1–404.8 keV, A₂ = ?0.18(4), A₄ = ?0.05(3); 272.5–364.5 keV, A₂ = 0.15(4), A₄ = ?0.03(3); 284.3–80.2 keV, A₂ = ?0.005(7), A₄ = 0.005(15); 318.1–324.6 keV, A₂ = 0.24(5), A₄ = ?0.01(5). The result for the 318.1–324.6 keV cascade has not been corrected for a small influence from the 318.1–404.8 keV cascade. Four E2/M1 mixing ratios are deduced from the angular correlation coefficients (energies in keV): $\text{?0.28 ≦ δ(325.8) ≦}\text{t}\text{?}\text{0.20}$, ?0.19 ≦ δ(318.1) ≦ ?0.035, ?1.5 ≦ δ (324.6) ≦ ?0.05, δ(272.5) = ?0.38(17). Transition strengths and limits to transition strengths are calculated for several transitions. The properties of negative parity states in ¹³¹Xe are investigated theoretically in a model where three neutron holes in the $\text{h}{}_{\mathrm{<mtext>11</mtext><mtext>2</mtext>}}$ orbit are coupled to the quadrupole vibrations of the even core. The experimental energies of the lowest negative parity states and the strengths of the transitions between these states are very well accounted for by the calculation.     

Conductivite electrique des magnetites faiblement substituees a l'aluminium ou au chrome et faiblement oxydees au voisinage de la temperature de transition de Verwey

The electrical conductivity of aluminum or chromium slightly substituted and slightly oxidized magnetites (0 < x < 0.27; 0 < δ 0.040) whose formula is Fe³⁺[□_δFe_(1?3δ)²⁺Fe_(1?x) + 28³⁺M_x³⁺]O₄^2? over the temperature range 300-77°K is affected by the composition of octahedral sites. In particular the Verwey transition temperature and its magnitude decrease with x and δ while the electrical conductivity and activation energy evolve differently on either side of this discontinuity.     

Measurement of the branching ratio Λ(X→γγ)/Λ(X→ total)

(68 ± 12) events of the type X⁰ → γγ yield the following branching ratio: Λ(X⁰ → γγ)/Λ(X⁰ → total = (1.71 ± 0.33)%.     

Coulomb excitation in 180Hf

Coulomb excitation studies have been performed to measure transition probabilities of collective quadrupole vibrational states in ¹⁸⁰Hf. The I = 2 level of the K^π = 2⁺ collective γ-band is established at 1200.5 keV with B(E2)_exc = (11.0 ± 1.1) × 10^?50e² · cm⁴ (3.6 ± 0.4 s.p.u.). The angular distribution of the de-exciting γ-rays from this level yields δ = 9.6⁺²²_?5.8 or, less likely, 0.7 ± 0.2 for the 1107.2 keV 2_γ⁺ → 2_g⁺ transition. The B(E2)_exc for any K^πI = 0⁺2 stateorother 2⁺ states up to 1500 keV is less than 5 × 10^?51e² · cm⁴ (< 0.2. s.p.u.).     

The O first rotational band from the C(Li,d)O reaction

The most prominent peaks in the ¹²C(⁶Li, d)¹⁶O spectra at energies up to 32 MeV correspond to levels in ¹⁶O at 6.910 ± 0.006 MeV (J^π = 2⁺), 10.346 ± 0.006 MeV (τ_CM < 50 keV, J^π = 4⁺), 16. 304 ± 0.020 MeV (τ_CM = 360 ± 40 keV) and 20.88 ± 0.06 MeV (λ_CM = 720 ± 100 keV). The last two states are probably the higher members of the first rotational band with J^π = 6⁺ and 8⁺, respectively. A comparison with recent theoretical calculations is given.     

Study of the production of Λb0 and B0 hadrons in pp collisions and first measurement of the Λb0→J/ψpK- branching fraction

The product of the Λ_b⁰(B⁰) di erential production cross-section and the branching fraction of the decay Λ_b⁰→J/ψpK^- (B⁰→J/ψpK^*(892)⁰) is measured as a function of the beauty hadron transverse momentum, pT, and rapidity, y. The kinematic region of the measurements is p_T <20 GeV/c and 2.0< y< 4.5. The measurements use a data sample corresponding to an integrated luminosity of 3fb^-1 collected by the LHCb detector in pp collisions at centre-of-mass energies √s= 7 TeV in 2011 and √s= 8 TeV in 2012. Based on previous LHCb results of the fragmentation fraction ratio, f_Λb⁰/f_d, the branching fraction of the decay Λ_b⁰→J/ψpK^- is measured to be
B(Λ_b⁰→J/ψpK^-)=(3.17±0.04±0.07±0.34_-0.28^+0.45)×10^-4,
where the rst uncertainty is statistical, the second is systematic, the third is due to the uncertainty on the branching fraction of the decay B⁰→J/ψpK^*(892)⁰, and the fourth is due to the knowledge of f_Λb⁰/f_d. The sum of the asymmetries in the production and decay between Λ_b⁰ and Λ_b⁰ is also measured as a function of p_T and y. The previously published branching fraction of Λ_b⁰→J/ψpπ^-, relative to that of Λ_b⁰→J/ψpK^-, is updated. The branching fractions of Λ_b⁰→P_c⁺(→J/ψp)K^- are determined.     

Electric monopole component in the 2+' → 2+ transition in 192Pt

Angular correlation measurements of K- and L-conversion electrons following the decay ¹⁹²Ir → ¹⁹²Pt have been made using a spectrometer with Ge(Li) and Si (Li) detectors. Absolute and relative internal conversion coefficients of transitions in ¹⁹²Pt were measured, using an ICC and prism β-spectrometers, to ≈ 2 % and values of δ_γ determined from the relative ICC. The experimental values measured in the study, A₂₂(K296γ316) = 0.138 ± 0.010, A₂₂(L296γ316) = 0.125 ± 0.013, α_K(296) = 0.0711 ± 0.0011, K/L_III = 9.65 ± 0.13. With δ_γ = + 5.4 ± 0.2, were employed for determining the E0/E2 amplitude ratios of conversion transitions, q(E0/E2), and the penetration parameter λ of the Ml component for the 2⁺' → 2⁺ (296 keV) transition in ¹⁹²Pt. The angular correlation measurements of L-conversion electrons enabled the elimination of one of two ranges of values of q and λ usually obtained. For the first time in our work, analysis of the e_Lγ angular correlation for the determination of the E0 component in the transition was carried out. As a result, q = +0.04 ± 0.05 with λ = ?4.5 ± 3.5 was obtained for the 296 keV transition. In this case, _ρ(E0) = 0.004 ± 0.005 agrees with _ρ(E0) = +0.006 determined theoretically by Kumar and Baranger for the 2⁺' → 2⁺ transition     

Measurement of H2CO hyperfine structure with a two-cavity maser

Hyperfine structure on the 1₁₀ → 1₁₁ rotational transition in H₂CO was measured using a two-cavity maser spectrometer with 0.3 kHz resolution. The measured spin-rotation constants are C(1₁₀) = −0.80 ± 0.05 kHz and C(1₁₁) = −3.07 ± 0.05 kHz. The hydrogen spin-spin interaction strength is D = 17.74 ± 0.10 kHz. The line center is at 4 829 659.89 ± 0.12 kHz. Properties of the beam source and computer line resolving methods are discussed briefly.     

Levels and transitions in 131Xe studied by the decay of oriented 131I

Sources of ¹³¹I were prepared by implantation in iron foils. Nuclear orientation of these sources was obtained by cooling them to temperatures of 30 to 50 mK using a dilution refrigerator and saturating the iron by an external magnetic field. Anisotropies of angular distributions of eleven γ-transitions in ¹³¹Xe have been measured, yielding the following results: the levels at 405 and 637 keV are $\text{3}\text{2}$⁽⁺⁾ and $\text{7}\text{2}$⁽⁺⁾ states and the assignment $\text{5}\text{2}$⁽⁺⁾ for the level a keV is confirmed. Deduced values of E2/M1 multipole mixing ratios are (energies in keV): ?0.5 ≦ δ(318) ≦ + 0.2; δ(364) = ?4.53±0.12; + 0.2 ≦ δ(405) ≦ +2.0; δ(723) = +0.207 ± 0.005. The allowed β-decay branch to the level at 637 keV is for at least 90% of the Gamow- Teller type.     

The E0 component of the 689 keV 2β → 2g transition in Sm

The electric monopole contribution to the 689 keV 2_β → 2_g transition in ¹⁵²Sm is studied by measuring the 689K-122γ directional correlation. The result for the directional correlation coefficient is a₂ (Kγ) = 0.10±0.05. This value is used together with earlier electron and γ-ray intensity data to evaluate the E0/E2 electron amplitude and the M1 penetration parameter. The corresponding E0/E2 mixing ratio is compared with recent theoretical predictions.