Evaluation of activation energy by means of different trap spectroscopy techniques

Correlations are deduced for the asymmetry and the halfwidth of a signal peak which correspond to a discrete level using different “isothermal” trap spectroscopy techniques. Using only the temperature $\text{T}$ of the scan peak maximum and the halfwidth δ = T₂ ? T₁ the activation energy can then be determined: $\text{E =}\text{T}{}^2\text{/(δT}{}_{\mathrm{K}}\text{)}$, where T_K(=4500?6000 KeV^-1) is given numerically for certain frequently applied trap spectroscopy techniques. T_K is the result of a complete mathematical treatment of the kinetic equation.     

Measurement of the analyzing power of the 3He(d, p)4He reaction below 1 MeV

The analyzing powers iT₁₁, T₂₀, T₂₁ and T₂₂ have been measured for the reaction ³He(d, p)⁴He at laboratory energies of 344, 465 and 727 keV. A polarized deuteron beam was used with quantization axis oriented perpendicular to and at 54.7° to the incident beam direction. With semi-conductor proton detectors in two perpendicular planes all four analyzing powers could be determined. The beam polarization was determined using the ³H(d, n)⁴He reaction at a mean energy of 130 keV. The uncertainty in this analyzing power and the effect on the results is discussed. The analyzing powers have been fitted to a Legendre polynomial expansion to four or five terms and the resulting coefficients tabulated. The results indicate that d-waves contribute to the reaction only through the ${}^4\text{D}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ entrance channel and their contribution falls off both above and below the $\text{3}\text{2}{}^{\mathrm{+}}$ resonance at 430 keV.     

Longitudinal polarization transfer in the D(d,n)3He reaction at 0°

We have measured the longitudinal neutron polarization in the $\text{D(}\text{d}\text{,}\text{n}\text{)}{}^3\text{He}$ reaction, at θ=0°, for an incident longitudinally polarized deuteron beam. A deuteron energy range of 3.3–14.9 MeV was covered. The polarization transfer from the deuteron to the neutron is found to be large, and the reaction is potentially useful as a source of polarized neutrons.     

Average polarization of 12B in 12C(μ, ν)12B(g.s.) reaction: Helicity of the π-decay muon and nature of the weak coupling

The helicity, h^?, of μ^? in π-decay has been determined as positive (h^??+0.90) from the average polarization, P_av≡〈J_B·s_μ〉, of ¹²B produced in the $\text{μ}{}^{\mathrm{?}}\text{+}{}^{12}\text{C}\text{→ν}{}_{\mathrm{\mu }}\text{+}{}^{12}\text{B}$ reaction. We obtain also dynamical information on μ-capture: (i) the weak magnetism form factor, μ=4.5±1.1, and (ii) the sum of the induced pseudoscalar (g_p) and the 2nd class induced tensor (g_T) couplings versus g_A, ($\text{g}{}_{\mathrm{<mtext>P</mtext>}}\text{+g}{}_{\mathrm{<mtext>T</mtext>}}\text{)}\text{g}{}_{\mathrm{<mtext>A</mtext>}}\text{=7.1±2.7}$. The latter result, adopting the “canonical” value of $\text{g}{}_{\mathrm{<mtext>P</mtext>}}\text{g}{}_{\mathrm{<mtext>A</mtext>}}$, leads to $\text{g}{}_{\mathrm{<mtext>T</mtext>}}\text{g}{}_{\mathrm{<mtext>A</mtext>}}\text{=+1±2.7}$ which is compatible with zero and in strong contradiction with the value ?—6 recently advocated by Kubodera, Delorme and Rho.     

Neutrino neutral current reactions in 12C

The differential and total cross sections for the nuclear reaction $\text{ν}{}_{\mathrm{\mu }}\text{+}{}^{12}\text{C (g.s) →}{}^{12}\text{C}{}^1$ (1⁺; T = 1, 15.1 MeV) + ν_μ are investigated for values of 50 ≤ E_νμ ≤ 300 MeV. An effective Hamiltonian for the above nuclear reaction is constructed from the neutrino-quark neutral current weak interaction, by first constructing the neutrino-nucleon neutral current interaction and then using the impulse approximation along with the non-relativistic reduction procedure. The Weinberg-Salam model is the basis of the calculations. Detailed expressions for the differential cross sections are derived including the nucleon momentum-dependent terms. The numerical results are obtained using the general 1p-shell wavefunctions of Cohen and Kurath. The sensitivity of the total cross sections to the nuclear models and to the Weinberg angle is studied. The corresponding anti-neutrino reaction is also investigated. The ratio is found to be independent of the nuclear wavefunctions but very sensitive to the Weinberg angle. Thus this observable can be used to determine the free parameter θ_w in a nuclear reaction, thereby complementing the studies involving free nucleons. The recoil polarization of the final nucleus ¹²C¹(1⁺; T = 1, 15.1 MeV) is also studied and its importance is pointed out.     

Measurement of the polarization parameter for antiproton-proton annihilation into charged pion and kaon pairs between 1.0 and 2.2 GeV/c

The polarization parameter P for the reactions $\text{p}\text{p}\text{→ π}{}^{\mathrm{?}}\text{π}{}^{\mathrm{+}}$ and $\text{p}\text{p}\text{→}\text{K}{}^{\mathrm{?}}\text{K}{}^{\mathrm{+}}$ has been measured over essentially the full angular range at ll laboratory momenta between 1.0 and 2.2. GeV/c, using a proton target polarized perpendicular to the scattering plane. The angles and momenta of both final state particles were determined from wire spark chambers, using the deflection caused by the polarized target magnet. Between 1000 and 5300 π^?π⁺ events, and 140 and 1300 K^?K⁺ events, were measured at each momentum. Differential cross sections for $\text{p}\text{p}\text{→ π}{}^{\mathrm{?}}\text{π}{}^{\mathrm{+}}$ were obtained. These are in excellent agreement with previous results. The polarization parameter for both channels is very close to +1 over much of the angular range. Legendre polynomial fits to the data are presented.     

Polarization in n-d scattering at 14.2 MeV

The angular distribution of the analyzing power in ${}^2\text{H(}\text{n}\text{,}\text{n}{}^2\text{H}$ elastic scattering has been measured at a neutron energy of 14.2 MeV in the angular range 50° to 152° c.m. Neutrons with a polarization of approximately 0.5 were obtained from the ${}^3\text{H(}\text{d}\text{n}\text{)}{}^4\text{He}$ reaction at a deuteron energy of 140 keV and lab emission angle of 82°. The ${}^3\text{H(}\text{d}\text{n}\text{)}{}^4\text{He}$ reaction was induced by vector polarized douterons obtained from a source of polarized ions. The latter was of a conventional “atomic beam” type. The results show good agreement with the data on the charge symmetric $\text{p}\text{+}\text{d}$ process at a proton energy of 14.5 MeV. Comparison is also made with the theoretical calculations of Doleschall and of Pieper and a good agreement is found.     

Parity non-conservation in the radiative capture of polarized neutrons by 35Cl

We report a measurement of the forward-backward asymmetry in the radiative capture of polarized cold neutrons in the reaction ³⁵Cl(n, γ)³⁶Cl where ³⁶Cl is in the ground state. The measured value of the asymmetry is a = (1.57 ± 0.531) × 10^?4. We deduce the mixing between the 2⁺ capture level and the neighboring 2^? levelto be $\text{〈2}{}^{\mathrm{?}}\text{¦H}{}_{\mathrm{<mtext>p.v.</mtext>}}\text{¦2}{}^{\mathrm{+}}\text{〉 = ?0.25 ± 0.08}\text{eV}$ before corrections. A measurement of the integral asymmetry of all γ-rays in the neutron capture by ³⁵Cl leads to agreement with measurements at Leningrad.     

Superfluidity of neutron matter: (II). Triplet pairing

The possibility of neutron triplet pairing and superfluidity in neutron star matter is investigated, and the energy gap and corresponding critical temperature is calculated or estimated as a function of Fermi momentum or density. The calculations are performed for a “one-pion-exchange gaussian” potential, and compared with the results for neutron and proton singlet pairing and superfluidity calculated earlier.The results indicate that neutron superfluidity, corresponding specifically to ³P₂ state pairing, may exist in a high-density shell in the nuclear-matter region of a neutron star, i.e. for 1.6 × 10¹⁴g/cm³ < ρ < 1.4 × 10¹⁵g/cm³, and the maximum self-consistent energy gap is Δ⁰₁k_F ≈ 0.6 MeV and Δ⁰₃(k_F) ≈ 0.1 MeV for an effective mass $\text{m}{}^1\text{≈ 0.75}\text{and}\text{k}{}_{\mathrm{<mtext>F</mtext>}}\text{≈ 2.1}\text{fm}{}^{\mathrm{?1}}$, i.e. for a mas ? ≈ 5.2 × 10¹⁴g/cm³. For $\text{m}{}^1\text{= 1.0}$ we get correspondingly Δ⁰₁(k_F) ≈ 3.3 MeV and Δ⁰₃(k_F) ≈ 0.6 MeV for k_F ≈ 2.2 fm^?1.     

Analysing power for neutron-proton scattering at 14.1 MeV

The analysing power A_γ(θ) for neutron-proton scattering has been measured at 14.1 MeV for c.m. angles between 50° and 157°. A polarized neutron beam was produced by the reaction ${}^3\text{H}\text{(}\text{d}\text{, n}\text{)}{}^4\text{He}$ at 110 keV, using polarized deuterons from an atomic beam polarized ion source. Liquid and plastic scintillators were used for proton targets and the scattered particles were detected in an array of plastic scintillators. Use of the associated alpha technique, multi-parameter recording of events and off-line computer treatment led to very low backgrounds. The results differ significantly from the predictions of the phase-shift analyses of Yale IV, Livermore X and Arndt et al. We find, however, excellent agreement with the predictions of the “Paris potential” of Lacombe et al. Existing n-p analysing power results up to 30 MeV are surveyed and found to be consistent. An attempt was made to look for an isospin splitting of the triplet P-wave phase shifts.     

Measurement of the magnetic moment of 39Ca by use of a polarized proton beam and NMR detection

Polarized β-emitting ${}^{39}\text{Ca}\text{(I}{}^{\mathrm{\pi }}\text{=}\text{3}\text{2}{}^{\mathrm{+}}$, $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext><mtext>=0.87</mtext>}}\text{s)}$ nuclei were produced in the reaction ${}^{39}\text{K(π|p, n)}{}^{39}\text{Ca}$ in thick polycrystalline targets of KBr, KCaBr₃, and KCaI₃ which served as hosts for the ${}^{39}\text{Ca}$ nuclei. The net polarization transferred to the ${}^{39}\text{Ca}$ nuclei was detected by measuring the asymmetry in the β-decay. The magnetic dipole moment of ${}^{39}\text{Ca}$ was measured by NMR detection. Including a diamagnetic correction we obtain ω=1.0216(2) nm.     

Estimate of fusion through deuteron-ionic halide interaction

The possibility of attaining the fusion reactions ¹⁹F(d,n)²⁰Ne, or ¹⁹F(d,p)²⁰F through coupling of a fluorine ion and a deuteron is discussed. Approximation of the ground state of this effective “bose atom” yields the following expression for the transmission coefficient for penetration of the deuteron through nuclear Coulomb barrier: $\text{T=}\text{exp}\text{[?2πZ(2s)}{}^{\mathrm{<mtext>3</mtext><mtext>4</mtext>}}\text{(}\text{m}{}_{\mathrm{<mtext>d</mtext>}}\text{20m}{}_{\mathrm{<mtext>e</mtext>}}\text{)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{]}$. The radius of the F^? ion is sa₀ and deuteron-to-electron mass is m_d/m_e. Thus, T is infinitesimal and the assumed model renders the said fusion reaction highly improbable.     

The analyzing power Aγ(θ) for the elastic scattering of 12 MeV neutrons from deuterons

The analyzing power A_γ(θ) was obtained at 10° intervals between 30° (lab) to 120° (lab) for ²H(n, n)²H at 12.0 MeV. The polarized neutron beam employed in the measurement was obtained by using neutrons emitted at 0° from the polarization transfer reaction ${}^2\text{H}\text{(}\text{d}\text{,}\text{n}\text{)}{}^3\text{He}$. The accuracy in the A_γ(θ) values that was achieved ranged from ± 0.006 to ± 0.013. Comparison of the data to A_γ(θ) results obtained at 12 MeV for the charge symmetric reaction ²H(p, p)²H shows that the two A_γ(θ) distributions are equal to within the above accuracy.     

On the challenge of measuring the colour charge of gluons

We propose two ways of measuring “directly” the chromodynamic gluon self-couplings. We argue that the measurements would serve to establish (or disprove) the gauge and non-Abelian nature of the candidate strong-interaction theory: QCD. Both experiments concern the production in e⁺e^? annihilation of a heavy vector meson resonance, followed by its hadronic decay into three “gluon jets”. The asymmetry of the decay plane relative to the electron axis is a measure of $\text{α}{}_{\mathrm{<mtext>S</mtext>}}\text{=}\text{g}{}^2\text{4π}$, with g the coupling for gluon self-interactions. If QCD is right, this value of g should coincide with the measured coupling of quarks to gluons. The two proposed experiments are difficult: they both demand very large statistics, one requires longitudinally polarized beams, the other the detection of weak-electromagnetic interferences. But the stakes are high.     

Neutron-proton radius differences and isovector deformations from π+ and π− inelastic scattering from 18O

π⁺ and π^? elastic and inelastic scattering from ¹⁸O have been measured at T(π)=164 MeV. Consistent with the results at 230 MeV, it is found that the ratio $\text{σ(π}{}^{\mathrm{?}}\text{)}\text{σ(π}{}^{\mathrm{+}}\text{)}$ for the 2₁⁺ state is 1.86(16), while for the 3₁^? state it is 0.89(6). These results are interpreted as indicating differences in neutron and proton deformations characterizing the 2₁⁺ transition and partial neutron blocking for the 3₁^? transition. Optical model analysis of elastic scattering leads to the conclusion that $\text{〈r}{}_{\mathrm{<mtext>n</mtext>}}{}^2\text{〉}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{?〈r}{}_{\mathrm{<mtext>p</mtext>}}{}^2\text{〉}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{=0.03(3)}\text{fm}$.     

On the proton-antiproton charge parity

The observed azimuthal asymmetry of the reaction $\text{p}\text{?}\text{p}\text{→π}{}^{\mathrm{+}}\text{π}{}^{\mathrm{?}}$ with the polarized target implies that the charge parity of the proton-antiproton pair is the same as predicted by the Dirac equation.     

Experimental detection and investigation of muon catalyzed fusion of deuterium and tritium

Measurement of the neutron yield of the reaction $\text{dt}\text{μ →}{}^4\text{He}\text{+ μ}{}^{\mathrm{?}}\text{+ 17.6}\text{MeV}$, induced by negative muons in a mixture of gaseous D₂ and T₂, has shown that the rate of muon transfer from deuterium to tritium is λ_dt = (2.7 ± 0.9) × 10⁸s^?1 and that the lower limit of the formation rate of dt_μ molecules is λ_dtμ > 10⁸s^?1.     

Prediction of the high-spin selectivity of compound reactions induced by heavy ions

Two procedures are described to predict the selectivity of heavy-ion (HI) compound reactions for excitation of high spins. The applicability of statistical-model calculations in respect to yrast line effects is discussed. Contour diagrams of the total cross sections $\text{σ(E}{}^1\text{, I), dσ(E}{}^1\text{, I)/}\text{d}\text{E}{}^1\text{and}\text{d}\text{σ(E}{}^1\text{)/}\text{d}\text{E}{}^1$ are derived, yielding the gradient $\text{d}\text{σ(E}{}^1\text{, I)/}\text{d}\text{I}$ and the p to “background” ratio of high-spin states as well as the “optimum Q-value” for any given HI compound reaction. The dependence of both the optimum Q-value and the shape of $\text{d}\text{σ(E}{}^1\text{)/}\text{d}\text{E}{}^1$ on the critical L-value at high bombarding energies can be used to determine L_crit. This is demonstrated for the reaction ${}^{12}\text{C}\text{+}{}^{14}\text{N}\text{→}{}^{26}\text{AI}$. A rougher estimate of the selectivity is given by the “grazing-collision picture” which is based on a consideration of the angular momentum balance. Using the reactions ¹⁰B(¹²C, d), ¹²C(¹²C, d), ¹²C(¹⁴N, d), ¹¹B(¹⁴N, p), ¹³C(¹⁴N, p), ${}^{10}\text{B}\text{(}{}^{14}\text{N}\text{, α)}$ and ¹²C(¹⁴N, ⁶Li) as examples, the theoretical predictions are shown to be in excellent agreement with experiment, for bombarding energies ranging between 40 and 120 MeV. The possibility to predict the high-spin selectivity is the precondition for an application of HI compound reactions for investigations of yrast lines and converts this class of reactions into an outstanding means for spectroscopy of high-spin states in light nuclei.     

The differential cross section and polarization quantities in the 4He(d,p)n4He and 2H(α, n)p4He reactions

The differential cross section and the polarization quantities (T₁₁, T₂₀, T₂₁, T₂₂, P_γ') in the deuteron breakup reaction by an α-particle are calculated in the framework of the recently developed three-body model. All values are discussed under the incomplete kinematical condition. All polarization quantities are caused by the difference of the potential between $\text{p}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ and $\text{p}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ waves of the N-α interaction. Results of the calculation are compared with the available measurement of (i) the differential cross section and the deuteron vector analysing power in the ⁴He($\text{d}$, p)n⁴He reaction and (ii) the differential cross section and neutron polarization in the ²H(α, $\text{n}$)p⁴He reaction. The agreement with experiment is very satisfactory in each case. Among the tensor analysing powers of the deuteron the absolute value of T₂₀ is very large. Observables at the FSI peak corresponding to ⁵He_g.s. are discussed systematically in the energy region of 5.4–20 MeV of the incident deuteron in the ⁴He(d, p)n⁴He reaction. Although the differential cross section is not sensitive to the energy of the three-body resonance, the polarization quantities T₁₁, T₂₀, P_γ' are quite sensitive to it.