Muon Capture on Deuteron and 3He

We present the results of a recent simultaneous study of the muon capture reactions ²H(?? ^?, ?? _?? )nn and ³He(?? ^?, ?? _?? )³H. The initial and final A = 2 and 3 nuclear wave functions are obtained from the Argonne v ₁₈ or chiral N3LO two-nucleon potential, in combination with, respectively, the Urbana IX or chiral N2LO three-nucleon potential in the case of A?=?3. The weak current consists of polar- and axial-vector components. The former are related to the isovector piece of the electromagnetic current via the conserved-vector-current hypothesis. These and the axial currents are derived either in a meson-exchange or in a chiral effective field theory (??EFT) framework. In the first case, there is one parameter which is fixed by reproducing the Gamow-Teller matrix element in tritium ??-decay (GT^EXP). In the second case, the low-energy constants, two in the polar and one in the axial-vector current, are fixed, respectively, by reproducing the A?=?3 magnetic moments and GT^EXP. The total rates are found to be 392.0 ± 2.3 s^?1 for A?=?2, and 1484 ± 13 s^?1 for A?=?3, where the spread accounts for the model dependence relative to the adopted interactions and currents (and cutoff sensitivity in the ??EFT currents).     

Some tips on the decomposition of tensor product representations of compact connected lie groups

Let ?₁, ?₂, ?₃, ?₄ be irreducible representations of a compact connected semisimple Lie group G with highest weights Λ₁, Λ₂, Λ₃, Λ₄, respectively. Let ?₁?₂ (resp. ?₃?₄) be irreducible representations of G with highest weights Λ₁·Λ₂ (resp. Λ₃·Λ₄). It is assumed that one knows the Clebsch-Gordan series of ?₁??₃ and ?₂??₄ (resp. of S²?₁, S²?₂, A²?₁ and A²?₂). Then we formulate a result (Theorem 2) which gives information on the decomposition of ?₁?₂??₃?₄ (resp. of S²(?₁?₂) and A²(?₁?₂)). Though this result is not complete, it is useful because it delivers the information very quickly and in a very simple manner.     

Glauber Dynamics for the Mean-Field Potts Model

We study Glauber dynamics for the mean-field (Curie-Weiss) Potts model with q??3 states and show that it undergoes a critical slowdown at an inverse-temperature ?? _s (q) strictly lower than the critical ?? _c (q) for uniqueness of the thermodynamic limit. The dynamical critical ?? _s (q) is the spinodal point marking the onset of metastability. We prove that when ??<?? _s (q) the mixing time is asymptotically C(??,q)nlogn and the dynamics exhibits the cutoff phenomena, a sharp transition in mixing, with a window of order n. At ??=?? _s (q) the dynamics no longer exhibits cutoff and its mixing obeys a power-law of order n ^4/3. For ??>?? _s (q) the mixing time is exponentially large in n. Furthermore, as ?????? _s with n, the mixing time interpolates smoothly from subcritical to critical behavior, with the latter reached at a scaling window of O(n ^?2/3) around ?? _s . These results form the first complete analysis of mixing around the critical dynamical temperature??including the critical power law??for a model with a first order phase transition.     

Discrepancy of Cross Sections in pd Breakup Reactions at E p = 250?MeV

In our previous inclusive experiment on ²H(p, p)pn at 247?MeV, the measured cross section at forward angles is about twice larger than 3N calculation with ?Ц? 3NF. Therefore, we have made an exclusive experiment on ²H(p, p ₁ p ₂)n at the same energy. The preliminary data suggest that the cross section was enhanced at forward angle of ?? ₁ and ?? ₂.     

Investigation of the kinetics of OH∗ and CH∗ chemiluminescence in hydrocarbon oxidation behind reflected shock waves

The temporal variation of chemiluminescence emission from OH^?(A² Σ ⁺) and CH^?(A² Δ) in reacting Ar-diluted H₂/O₂/CH₄, C₂H₂/O₂ and C₂H₂/N₂O mixtures was studied in a shock tube for a wide temperature range at atmospheric pressures and various equivalence ratios. Time-resolved emission measurements were used to evaluate the relative importance of different reaction pathways. The main formation channel for OH^? in hydrocarbon combustion was studied with CH₄ as benchmark fuel. Three reaction pathways leading to CH^? were studied with C₂H₂ as fuel. Based on well-validated ground-state chemistry models from literature, sub-mechanisms for OH^? and CH^? were developed. For the main OH^?-forming reaction CH+O₂=OH^?+CO, a rate coefficient of k ₂=(8.0±2.6)×10¹⁰ cm³?mol^?1?s^?1 was determined. For CH^? formation, best agreement was achieved when incorporating reactions C₂+OH=CH^?+CO (k ₅=2.0×10¹⁴ cm³?mol^?1?s^?1) and C₂H+O=CH^?+CO (k ₆=3.6×10¹²exp(?10.9 kJ?mol^?1/RT) cm³?mol^?1?s^?1) and neglecting the C₂H+O₂=CH^?+CO₂ reaction.     

π−A1 interference in πN → ϱN

An estimate of the A₁NN coupling is made using axial vector meson dominance of weak form factors, PCAC and current algebra. We use this to predict a vanishingly small polarisation due to unnatural parity exchanges in πN → ?N near the forward direction. In contrast, the contribution to πN → ωN of the Z (the J^PC = 2^?? exchange degenerate partner of the A₁) is found to be significant as indeed indicated by experiment.     

Molecular beam reactive scattering of Br2 from Pd(111) using an electrochemical effusive source

A computer-controlled modulated molecular beam source is used to investigate the kinetics of the surface reactions which occur when bromine is reactively scattered by Pd(111). The reaction products are atomic bromine and molecular bromine: the latter species arises from an adatom recombination process and gives rise to a product vector modulated at twice the frequency of the incident beam (2ω.) By making suitable measurements of the temperature dependence of the product vector phase shifts at ω and 2ω, the four kinetic parameters which characterise the first-order and second-order rate processes are obtained. These are: A₁ = 2.5×10⁹ s^?1, E₁ = 177 kJ mol^?1, A₂ = 3.6×10^?10 m² s^?1, E₂ = 131 kJ mol^?1. The significance of these values is discussed in terms of the properties of the transition state to desorption.     

Axial vector meson production

Recently available differential cross section and density matrix information on π^?p → B^?p at 4 GeV/c are successfully described in terms of t channel exchanges and s channel absorptive effects. The s channel helicity amplitude which is dominant at small |t| (zero net helicity flip ω exchange) is found to have a zero at ?t = 0.2 GeV². SU(3) and higher symmetries are used to predict cross sections for further axial vector meson production processes, in particular non-diffractive A₁ production. The importance of these processes with regard to Regge phenomenology and meson spectroscopy is emphasized.     

Q1(1290) and Q2 (1400) decay rates and their SU(3) implications

We summarize and combine the known information on the decay rates of the strangeness-one axial vector mesons, Q₁ and Q₂. From this information and the rate for B→ωπ, we determine the Q_A?Q_B mixing angle and the S-wave, symmetric and antisymmetric octet couplings for vector-pseudoscalar decays of axial vector mesons. If we assume the D(1285) and the E(1420) belong to the J^PC=1⁺⁺ nonet, we find the A₁ to have a mass of ～1.47 GeV and a large (>0.3 GeV) width.     

Stimulated Raman scattering in natural crystals of SrSO4, BaSO4 and PbSO4: High-order Stokes and anti-Stokes generation with?single-wavelength UV, visible, and near-IR excitation, as?well?as cascaded up-conversion nonlinear �� (3)?�� (3) lasing effects under dual-wavelength picosecond collinear coherent pumping

Orthorhombic crystals of SrSO₄, BaSO₄, and PbSO₄, known as natural crystals celestine, barite, and anglesite, were found to be attractive ?? ⁽³⁾-active nonlinear optical materials. High-order Stokes and anti-Stokes picosecond generation that spans almost two octaves has been recorded with single-wavelength laser excitation in the UV, visible, and near-IR ranges. All recorded Raman induced lasing components were identified and attributed to the SRS-promoting vibration modes of the studied crystals (?? _SRS??999?cm^?1 for SrSO₄,?? _SRS??985?cm^?1 for BaSO₄ and ?? _SRS??977?cm^?1 for PbSO₄). Under dual-wavelength (?? _f1=1.06415???m + ?? _f2=0.53207???m) collinear coherent picosecond pumping several new manifestations of cascaded ?? ⁽³⁾??? ⁽³⁾ nonlinear up-conversion lasing effects were observed in BaSO₄ and SrSO₄ crystals. We classify all three studied sulfate crystals as promising SRS-active materials for Raman laser frequency converters and as efficient ?? ⁽³⁾-crystals that efficiently generate Stokes and anti-Stokes frequency combs, which can enable experiments of ultra-short pulse syntheses.     

The probability of prompt and delayed fission of muonic237Np

Fission fragments from the reaction²³⁷Np(μ ^?,γ,f) have been measured in coincidence with muonic X-rays. The efficiency of the fission fragment detector is determined from (μ ^?,γ,f)-data of the same experiment. The total fission probability perμ-stopP _t has been measured as well as the fission probabilities P_f of the non-radiative muonic (3d→1s)- and (2p→1s)-transitions; the latter has been divided into two parts leading to different mean excitation energiesE:P _t =(54±17)%,P _f (3d→1s)=(41±21)%,P _f (2p→1s,E=6.218 MeV)=(61±19)%, andP _f (2p→1s,E=6.525 MeV)=(57±18)%. The influence of the muon on the fission barrier is discussed. The fission probability after muon capture is compared with a calculated value using a distribution of nuclear excitation energies following muon capture and the fission probability as measured in a²³⁸U(³He,αf)-reaction.     

Multiparticle azimuthal correlations of negative pions in nucleus-nucleus collisions

Multiparticle azimuthal correlations of ?? ^? mesons have been studied in dC, HeC, CC, CNe, MgMg, (d, He)Ta, CCu, CTa, and OPb collisions at momentum of 4.2, 4.5 GeV/c per nucleon within the standard transverse momentum analysis method of P. Danielewicz and G. Odyniec. The data were obtained by SKM-200-GIBS and Propane Bubble Chamber Collaborations of JINR. The axis has been selected in the phase space and with respect to this axis ?? ^? meson correlations were observed. The values of the coefficient of the correlations linearly depend on the mass numbers of projectile (A _P ) and target (A _T ) nuclei. The Quark-Gluon String Model satisfactorily describes the experimental results.     

Electro-optical features of antiferroelectric liquid crystal material (S)-(+)-4-(1-methylheptyloxycarbonyl) phenyl 4′-(6-octanoyloxyhex-1-oxy) biphenyl-4-carboxylate in its ferro and antiferroelectric phases

A detailed investigation of the electro-optical switching parameters of an antiferroelectric liquid crystal (S)-(+)-4-(1-methylheptyloxycarbonyl) phenyl 4′-(6-octanoyloxyhex-1-oxy) biphenyl-4-carboxylate (abbreviated as S-7H6Bi) has been carried out. S-7H6Bi has paraelectric (SmA^?) and ferroelectric (SmC^?) phases in addition to antiferroelectric (SmC^?_A) phase. Switching parameters viz. spontaneous polarization and switching time were determined by polarization reversal method. The spontaneous polarization (P_s) is found to be highly temperature dependent and decreases with temperature. The maximum value of P_s is found to be ∼90 nC/cm² whereas the switching time (t_s) is found to be of the order 1-2 ms. The temperature dependent torsional viscosity (γ_t) is of the order 10 Pa sec. It increases with decrease in temperature.     

The A1 and ρ mesons from the violation of local Lorentz invariance

A skew-symmetric field and its dual field are quantized by requiring Lorentz invariance and the positive definiteness of the Hamiltonian. When they are massless they describe scalar and pseudoscalar particles, respectively, i.e., h^PC = 0⁺⁺ and 0^?? (h denotes helicity). If they acquire their mass, then they become axial vector (J^PC = 1⁺⁺, like the A₁ meson) and vector (J^PC = 1^??, like the ρ meson), respectively. The lowest-order Lagrangian may be derived from a generally covariant Lagrangian for the gravitational field, previously proposed by Nakano and the author.     

Optical potential calculations for the 1s level in pionic atoms

The Ericson-Ericson optical potential for theπ-nucleuss-wave interaction was extended to be applicable also for light nuclei. In particular, terms of order A^?1 were evaluated and the (π2N) dispersion was considered. From comparison with experimental data we found that considerable improvement could be achieved by introducing terms of order A^?1. The (π2N) dispersion was found to be repulsive and of the same magnitude as the absorption. The (πN) scattering lengths were deduced to be α₃?α₁=0.258±0.008m _π ^?1 and α₁+2α₃=?0.018±0.008m _π ^?1 .     

Synthesis and characterisation of the Fe(II–III) hydroxy-formate green rust

A new methodology was envisioned in order to prepare green rust compounds build on organic anions that could intervene in microbiologically influenced corrosion processes of iron and steel. The formate ion was chosen as an example. The formation of rust was simulated by the oxidation of aqueous suspensions of Fe(OH)₂ precipitated from Fe(II) lactate and sodium hydroxide, in the presence of sodium formate to promote the formation of the corresponding green rust. The evolution of the precipitate with time was followed by transmission Mössbauer spectroscopy at 15 K. It was observed that the initial hydroxide was transformed into a new GR compound. Its spectrum is composed of three quadrupole doublets, D ₁ (δ?=?1.28 mm s^?1, Δ?=?2.75 mm s^?1) and D ₂ (δ?=?1.28 mm s^?1, Δ?=?2.48 mm s^?1) that correspond to Fe(II) and D ₃ (δ?=?0.49 mm s^?1, Δ?=?0.37 mm s^?1) that corresponds to Fe(III). The relative area of D ₃, close to the proportion of Fe(III) in the GR, was found at 28.5?±?1.5% (～2/7). Raman spectroscopy confirmed that the intermediate compound was a Fe(II–III) hydroxy-formate, GR(HCOO^?).     

Searching for the QCD critical point in AA collisions at CERN SPS

We investigate the transverse momentum correlations of pairs of opposite charged pions near their production threshold. Through intermittency analysis, we search for power-law dependence on observation scale, as dictated by critical QCD. We analyze the data on the most central collisions in four A systems (A = p, C, Si, Pb) at maximum SPS energy. We find a significant effect for the SiSi system approaching in size the critical QCD predictions as measured by the intermittency index ? ₂. Absence of this effect in the (?? ^?, ?? ^?) sector of the SiSi system gives further support that the observed behavior in the isoscalar mode is of critical origin.     

Hyperfine structure and nuclear magnetic moments of some neutron-deficient thallium isotopes

Using the atomic-beam magnetic resonance method, hyperfine structure (h.f.s.) measurements have been performed in the²P_1/2 electronic ground state of the neutron-deficient thallium isotopes^193–202Tl. In the doubly odd isotopes, the magnetic dipole hyperfine interaction constantsa were determined, while in the odd-A isotopes, direct measurements of the nuclearg-factors,g _I , were made. The electronicg-factor was measured in¹⁹⁸Tl. The magnetic dipole moments of the doubly odd isotopes have been evaluated by a direct comparison with known values in the stable isotope²⁰³Tl. The moments of the odd-A isotopes are in agreement with pervious measurements by optical spectroscopy. A discussion of the magnetic dipole moments in terms of different nuclear models is included. The moments of the 2^? nuclear ground states of the doubly odd isotopes may be interpreted as arising from a combination of the configurations 2^? (πs_1/2 vf_5/2) and 2^? (πs_1/2 vp_3/2).     

Measurement of Ar(I) and Ar(II) transition probabilities in LTE ARC plasmas

The transition probabilities of two Ar(I) lines and one Ar(II) line have been measured in emission on wall-stabilized argon arc plasmas (0·5×10⁵?p, Nm^-2?3×10⁵; 10,000?T, K?20,000; 10²²?N_e, m^-3?5×10²³) using the “method of best fit (MBF)”. The results (without line-wing correction) are for Ar(I) at 714·7 nm, A_nm=5·66×10⁵ s^-1±5%; for Ar(I) at 430·0 nm, A_nm=3·40×10⁵ s^-1±5%; for Ar(II) at 480·6 nm, A_nm=8·82×10⁷ s^-1±7%. These values were not influenced by deviations from LTE, which have been observed at electron number densities n_e?10²³ m^-3. The small uncertainties were achieved after careful corrections of different sources of error.     

Low temperature vibrational relaxation of OD in the A2Σ, state

The vibrational relaxation of the A ²Σ state of OD has been studied in the low translational temperature environment of an argon free-jet (T_trans near 5 K). Using laser induced fluorescence (LIF), the absolute vibrational relaxation rate coefficients were measured for OD A²Σ (ν′) to be 7.1 ± 2.6 × 10^?11, 5.9 ± 1.4 × 10^?11, and 2.7 ± 1.1 × 10^?11 cm³ s^?1 for the ν = 3, 2 and 1 states, respectively. State-to-state relaxation rate coefficients were also obtained for the ν= 1, ? = 1 level going to ν= 0, ? levels in the A²Σ manifold. The rotational relaxation rate coefficient for ν= 1, ?= 1 in the A state of OD was found to be 9.6 ± 1.0 × 10^?11cm³s^?1. These values are consistent with values measured for OH A²Σ, and the total loss rates are near the capture rate coefficient value. The vibrational relaxation rate coefficients k_ν appear to be governed by the vibrational energy of the molecule rather then by interaction with nearby dissociative states such as the a⁴Σ state. The relative Einstein A factors for the A²σ (ν = 3) state of OD were determined and compared with the available calculated value.