High-precision evaluation of the magnetic moment of the helion

NMR spectra of samples containing a mixture of hydrogen deuteride HD with pressure of about 80 atm and helium-3 with partial pressure of about 1 atm are analyzed. The ratio of the resonance frequencies of the nuclei, F(³He)/F(H₂), is determined to be 0.761786594(2), which is equal to the magnetic moment of the helion (bound in a helium atom) in the units of the magnetic moment of a proton (bound in molecular hydrogen). The uncertainty of two digits in the last place corresponds to a relative error of ??[F(³He)/F(H₂)] = 2.6 × 10^?9. The use of the known calculated data on the shielding of nuclei in the helium-3 atom (??(³He) = 59924(2) × 10^?9) and on the shielding of protons in hydrogen (??(H₂) = 26288(2) × 10^?9) yields a value of ??(³He)/?? _p = ?0.761812217(3) for the free magnetic moment of the helion in the units of the proton magnetic moment.     

Study of the ρ, ω, ϕ→ηγ→7γ decays with an SND detector on a VEPP-2M collider

The e ⁺ e ^?→ηγ→7γ process was studied in the energy range 2E=600–1060 MeV with an SND detector on a VEPP-2M e ⁺ e ^? collider. The decay branching ratios B(φ→ηγ)=(1.353±0.011±0.052)×10^?2, B(ω→ηγ)=(4.62±0.71±0.18)×10^?4, and B(ρ→ηγ)=(2.73±0.31±0.15)×10^?4 were measured.     

Charge exchange and excitation cross sections at collisions of alpha particles with be-like impurity oxygen ions in a plasma

The charge exchange and excitation cross sections at collisions of alphas with O⁴⁺(1s ²2s ²) impurity atoms in a hot plasma for striking energies E _c varying from 20 keV to 2 MeV are determined for the first time. The cross sections are calculated using the method of close-coupling equations with 13 singlet four-electron quasi-molecular states taken as a basis. The partial cross sections of charge transfer to the 1s, 2s, and 2p states of a He⁺ ion and for O⁴⁺(1s ²2s ²) → O⁴⁺(1s ²2lnl’) (n = 2, 3) electronic excitation of an oxygen ion are found. The maximal value of the charge exchange total cross section roughly equals 2.2 × 10^?16 cm² at E _c ≈ 0.7 MeV. The excitation total cross section has a maximum of ≈ 7.7 × 10^?16 cm² at E _c ≈ 80 keV for single-electron excitation and ≈6.5 × 10^?16 cm² at E _c ≈ 0.7 MeV for two-electron excitation.     

Radiative neutron capture by 2H, 7Li, 14C, and 14N nuclei at astrophysical energies

The possibility of describing experimental data on the total cross sections for the n ²H, n ⁷Li, n ¹⁴C, and n ¹⁴N radiative-capture processes within the potential cluster model involving forbidden states and their classification according to Young’s tableaux is considered. It is shown that this model and the methods used here to construct potentials make it possible to describe correctly the behavior of the experimental cross sections at energies between 5 to 10 meV (5 × 10^?3–10 × 10^?3 eV) and 1 to 15MeV.     

Doubly radiative neutron capture by 2H, 3He, 16O and 208Pb

Cross-sections for doubly radiative thermal neutron capture on ²H, ³He, ¹⁶O and²⁰⁸Pb are calculated to be 21, 1200, 41 and 50 nb, corresponding to branching ratios of σ(n, γγ)/σ(n, γ) = 4.0 × 10^?5, ～ × 10^?2, 2.2 × 10^?4 and 1.0 × 10^?4, respectively.     

Classical stability of direct products of spheres in gravitational systems

Classical stability of Einstein spaces S^d₁ ×?×S^d_n(d_j ? 2) against all fluctuations is investigated in euclidean gravity with a cosmological constant. It is shown that S^d is classically stable, while S^d₁ ×?× S^d_n(n ? 2) is classically unstable. As a generalization of this analysis it is proved that a compact Einstein space B₁ ×?× B_n(n ? 2) which is a direct product of each Einstein space is classically unstable. Non-Einstein spaces M² × S⁴ (M² × S² × S²) are also considered in six- dimensional Einstein-Maxwell theory and are shown to be classically stable (unstable).     

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 search for the decay of Vanadium-50 with a low-level gamma-spectrometer

The spectrometer consists of a 4″×4″ NaJ-crystal with a double lead shield — the inner one being of selected lead — and a guard anticoincidence ring in between. The apparatus is situated in a cellar covered by 3 meters of soil. The total background above 0.03 MeV is 120 cpm, being extremely stable with an intrinsic r.m.s. variation below ±2 per mil. The crystal is surrounded by a sample container of volume 1.8 liters. An energy dependent gamma detection limit (2σ) ranging between 0.3 and 0.8 dpm has been obtained. This corresponds to a maximum detectable halflife of 1.0 to 2.7× 10¹⁸ years per mole of the radioactive nuclide in the sample container. In the case of vanadium-50 (isotopic abundance 0.25%) a lower limit of the half-life was found to be 9.0×10¹⁶ and 6.9×10¹⁶ years respectively for the two modes of decay V⁵⁰-EC-Ti^50*-γ(1.58 MeV) — Ti⁵⁰ and V⁵⁰-β^?-Cr^50*-γ(0.78 MeV)-Cr⁵⁰.     

Experimental investigation of highly excited states of the 5,6He and 5,6Li nuclei in the (6Li, 7Be) and (6Li, 7Li) one-nucleon pickup reactions

The (⁶Li, ⁷Be) and (⁶Li, ⁷Li) reactions on ⁶Li and ⁷Li nuclei were investigated in the angular interval 0°–20° in the laboratory system at a ⁶Li energy of 93 MeV. In addition to low-lying states of the ^5,6He and ^5,6Li nuclei, broad structures were observed near the t(³He)+d and t(³He)+t thresholds at the excitation energies of 16.75 (3/2⁺) and ～20 MeV (for ⁵He), 16.66 (3/2⁺) and ～20 MeV (⁵Li), 14.0 and 25 MeV (⁶He), and ～20 MeV (⁶Li). The angular distributions measured in the ⁷Li(⁶Li, ⁷Be)⁶He reaction for transitions to the ground state (0⁺) and excited states at E _x=1.8 MeV (2⁺) and 14.0 MeV of the ⁶He nucleus were analyzed by the finite-range distorted-wave method assuming the 1p-and 1s-proton pickup mechanism. The (⁶Li, ⁷Be) and (⁶Li, ⁷Li) reactions were shown to proceed predominantly through the one-step pickup mechanism, and the broad structures observed at high excitation energies are considered as quasimolecular states of the t(³He)+d and t(³He)+t types.     

Experimental observation of electron screening for the D(p, γ)3He nuclear reaction in titanium Deuteride TiD

Characteristics of the pd reaction (p + d → ³He + γ(5.5 MeV)) in titanium deuteride at astrophysical proton-deuteron collision energies ranging from 5.3 to 10.5 keV are investigated. Experiments are conducted on the pulsed plasma Hall accelerator at Tomsk Polytechnic University (Tomsk, Russia). The number of accelerated protons in a pulse 10 μs long is 5 × 10¹⁴ at a repetition rate of 7 × 10^?2 Hz. Gamma rays with an energy of 5.5 MeV are recorded by eight detectors based on NaI(Tl) crystals (100 × 100 × 400 mm) arranged around the TiD target. The dependence of the astrophysical S factor for the pd reaction on the proton-deuteron collision energy and the electron screening potential of protons interacting with deuterons in titanium deuteride are measured for the first time.     

First experimental evidence of D(p, γ)3He reaction in titanium deuteride in ultralow collision energy region

The article is devoted to the investigation of a pd-reaction (p + d → ³He + γ(5.5 MeV)) under-going in titanium deuteride in astrophysical collision energy region of protons and deuterons ranging from 5.3 to 10.5 keV. The experiments have been performed using the Hall NR TPU (Tomsk, Russia) pulsed plasma accelerator. The number of accelerated protons in 10 μs pulse was 5 × 10¹⁴ at a repetition rate of 7 × 10^?2 Hz. Detection of 5.5 MeV gamma rays was carried out using eight detectors based on crystals of NaI(Tl) (100 × 100 × 400 mm) placed around the TiD target. For the first time, the dependencies between the astrophysical S-factor and the effective cross section of the pd-reaction from proton-deuteron collision energy, and the potential electronic screening of the interacting protons and deuterons in titanium deuteride have been measured.     

First observation of the production and decay of the Σc+

An event with the decay chain Σ_c⁺ → Λ_c⁺ + π⁰, Λ_c⁺ → K^? + p + π⁺, has been observed in an exposure of BEBC, equipped with a track sensitive target, to the wide band neutrino beam from the SPS at CERN. The event has a unique three constraint kinematic fit to the ΔS = ?ΔQ reaction v + p → μ^? + p + K^? + π⁺ + π⁺ + π⁰ with both gammas from the π⁰ decay detected. The proton and other final state particles are identified. The masses are M(Λ_c⁺) = 2290 ± 3 MeV/c², M(Σ_c⁺) = 2457 ± 4 MeV/c² and M(Σ_c⁺) ? M(Λ_c⁺) = 168 ± 3 MeV/c². Including other data one obtains M (Σ_c⁺⁺) ? M(Σ_c⁺) = 0 ± 4 MeV/c².     

Absolute intensity measurements of the CO2 bands 401III←000 and 411III←010

The absolute intensities of the transitions 401_III←000 and 411_III←010 of CO₂ have been measured from spectra obtained under high resolution. Both the vibration-rotation line intensities and the integrated band intensities are reported. The rotationless transition moment of 401_III←000 is deduced and a vibration-rotation interaction factor F(m) = 1+(4.92×10^?4)m+(4.4×10^?7)m² is determined. The values obtained are: S_Band(401_III←000) = (25.54±0.22)×10^?5 cm^?2atm_{(293 K)}^?1, |R₀₀₀^401_III| = (1.87±0.02)×10^?4D, and S_Band(411_III←010) = (1.83±0.13)×10^?5 cm^?2atm_{(293 K)}^?1.     

The study of the ground state rotational bands in U 233 and U 235 by the inelastic scattering of deuterons

The ground state rotational bands in the odd isotopes of uranium U 233 and U 235, were studied by the inelastic scattering of 13.1 MeV deuterons. Seven members of these bands were seen in both nuclei. By fitting the experimental energies of the levels to the relation E(I)= =AI(I+1)+B[I(I+1)]², the parametersA andB were determined. Their values and the upper limits of the quadrupole reduced transition probabilities determined from the cross sections were: U 233:A=(5.93±0.10)keV,B=(?0.002±0.001)keV,B(E2,5/2→7/2)= =(6.51±0.66)×10^?48 e² cm⁴,B(E2,5/2→9/2)=(2.80±0.37) X 10^?48 e² cm⁴. U 235:A=(5.36±0.04)keV,B=(?0.0017±0.0004) keV,B(E2,7/2→9/2)=(8.05±0.71) × × 10^?48 e² cm⁴,B(E2,7/2→11/2)=(2.17±0.39) X 10^?48 e² cm⁴.     

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.     

Parity nonconservation in pα scattering

The elastic scattering of longitudinally polarized protons on ⁴He at energy E_p ? 15 MeV is considered. The difference of cross sections for protons of positive and negative helicities which is due to the weak interaction is calculated. The magnitude of the effect reaches 2–3 × 10^?7.     

Quasi-free scattering of pions on 3, 4He

Differential cross sections for ^{3, 4}He(π, π') are presented for angles of 60° and 120° at 200 MeV and 120° at 295 MeV. The momentum spectra for the scattered pions are dominated by a peak attributed to quasi-free scattering from individual nucleons. There are significant differences between the scattering on ³He and ⁴He as well as between the scattering of π⁺ and π^? on ³He. The data are compared to a simple model incorporating the free π+N scattering amplitudes. Modifications for the structure and dynamics of the target nucleus are discussed.     

Search for a new light gauge boson in π0, η and η′ decays

Upper limits for the production of new light gauge bosons in π⁰, η and η′ decays have been obtained with the Crystal Barrel detector. The kinematically well-constrained reactions p?p → π⁰π⁰ P have been studied, where P ? π ⁰, η, η′ decays through the emission of a single photon recoiling against a missing state X. X can be a long-lived weakly interacting particle or it decays into ???. The resulting branching ratio upper limits (90 % C.L.) are: 6 × 10^?5 for masses M _X of the missing particle X lying between 65 MeV/c² and 125 MeV/c² (π⁰ decay), 6 × 10^?5 for M _X between 200 MeV/c² and 525 MeV/c² (gh decay), and 4 × 10^?5 for M _X between 50 MeV/c² and 925 MeV/c² (η′ decay). The π⁰-decay limit represents an improvement by a factor of 4 to 8 (depending on M _X) when compared to the existing limit, whereas the η and η′ decay limits have been measured for the first time, thereby extending the M _X range from 125 MeV/c² up to 925 MeV/c².     

Measurement of radiative Σ±→nπ±γ decay

The radiativeΣ ⁺ → nπ⁺ γ decay mode was analysed in the 81 cm SACLAY hydrogen bubble chamber exposed to a stoppingK ^? beam at the CERN PS. The pion spectrum was measured up to momenta of 150 MeV/c in theΣ rest frame. We obtain the following branching ratios based on 180 Σ⁺→nπ⁺γ and 292Σ ^?→ nπ^?γ events:Γ(Σ⁺ → nπ⁺ γ)/Γ(Σ⁺→nπ⁺)=(0.93±0.10)×10^?3 Γ(Σ^?→nπ^? γ)/Γ(Σ^?→nπ^?)=(0.46±0.06)×10^?3. An unambiguous assignment ofS-wave to the Σ^?→nπ^? andP-wave toΣ ⁺→nπ⁺ was obtained. The absolute and differential decay rates as well as the parity assignments are in good agreement with theoretical predictions.     

A new experimental limit for the decay K+ → π+γγ

A search for K⁺ → π⁺γ, π⁺γγ, π⁺γγγ was made detecting pions from stopped kaons in the kinetic energy region between 117 MeV and 127 MeV. New Limits of 1.4 ×10^?6, 8.4 × 10^?6 and 1.0 × 10^?4 for the branching ratio were obtained assuming a phase-space spectrum on the pion energy. The first limit also aplies to another process K⁺ → π⁺ + a, where a is a light meson with mass smaller than 100 MeV/c² and decays into nγ's with lifetime less than 10^?9 s.