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1.
High-spin states have been populated in 54119Xe via the 96Mo( 27Al,p3n) reaction at 133 MeV, using the
γ-ray spectrometer to record triple γ-ray coincidences. The known level scheme has been significantly extended and several band crossings identified. In particular, the ν h11/2 yrast band has been extended to Iπ = (83/2 −) and shows features which are consistent with those of smooth band termination at high spin. Theoretical results for 119Xe at high spin are discussed within the framework of cranked Nilsson-Strutinsky calculations, together with results for 117Xe. 相似文献
2.
A rigorous calculation of the quantum-mechanical rotational partition function for tetrahedral XY4 molecules yields Q r = (
)(2 IY + 1) 4π
-
exp(/4), where IY is the spin of the Y nucleus, and ≡ Bhc/kT. This result is accurate to 1 per cent or better for all values of B and T such that <
. 相似文献
3.
The production rate for η′ in pp → ppη′ at rest is calculated in a covariant one boson exchange model, previously applied to study π 0 and η production in NN collisions. The transition amplitudes for the elementary BN → η′ N processes with B being the meson exchanged ( B = π, σ, η, , ω and a0) are taken to be the sum of s- and u-channels with a nucleon in the intermediate states, and an a0 meson pole in a t-channel. The couplings of the η′ to hadrons are a factor 0.4 weaker than the respective η-hadron couplings, as suggested by a quark model and a singlet-octet mixing angle θ = −23°. The model reproduces near threshold cross sections for the quasielastic processes π −p → nη(η′) and pp → ppη(η′) reactions. 相似文献
4.
The Doppler-Shift Attenuation Method has been used to extract transition quadrupole moments of high-spin bands in the N=74 isotones 133Pr, 132Ce and 131La, produced in the 37Cl + 100Mo reaction. The results appear to be configuration dependent and, for 133Pr and 132Ce, the involvement of Ω=1/2 ν h9/2 and ν f7/2 intruder orbitals appears to enhance the collectivity at high spin ( I>25 ). 相似文献
5.
Studies of ion dynamics in the highly conductive glassy fast ionic conductor (FIC) xLi2S + (1 − x) B2S3 ( x = 0.65 and 0.70) were made with NMR nuclear spin lattice relaxation (NSLR) R1(ω, T) of both mobile 7Li and immobile 11B ions, and 7Li NMR line narrowing δν( T). The possible dependence of ion dynamics on the short range order structures (SRO) and the distribution of activation energies (DAE) in this highly conductive FIC was investigated. Two Gaussian DAE were employed to fit 7Li NSLR data, where each Gaussian DAE was correlated to a separate 11B NSLR in a BS 3 and in a BS 4 group. The long range diffusion of Li ions among BS 3 groups and a seemingly localized ionic hopping motion around BS 4 group is suggested as a microscopic model for the ion dynamics in thioborate glasses, namely a ‘two channel relaxation’. 相似文献
6.
We study the nonresonant three-body decays of B+→ D(*)−sK+π + and Bd→ Ds(*)−K0π +. We find that these decays can provide the information on the time-like form factors of D(*)sK. We also explicitly investigate Bd→ Ds(*)−K*+ decays by discriminating the nonresonant contributions with the unknown D(*)s wave functions being fixed by the measured mode of Bd→ Ds−K+. 相似文献
7.
We study semileptonic decays B→η (′)lν, taking into account the flavor-singlet contribution ( Fsinglet+) to the B→η (′) form factors, which arises from the two-gluon emission in a decaying B meson. It has been recently pointed out that, in addition to large weak annihilation effects, the unknown value of Fsinglet+ prevents accurate theoretical estimates in the analysis of B→η′ K decays in QCD factorization. We present a certain method to determine Fsinglet+ with a reasonable accuracy, using B→η (′)lν and B→π lν decays. We also investigate the possible effect of Fsinglet+ on the estimated branching ratios (BRs) for B→η (′)lν and find that the BR for B→η′ lν is particularly sensitive to the effect of Fsinglet+. 相似文献
8.
We study the contribution of Bc mesons to the search for B → τν τ decays. We find that at LEP the contributions from Bu and Bc mesons can be comparable. This observation can have a relevant impact on the extraction of constraints on new physics (such as charged-Higgs contributions) from current LEP limits on B → τν final states. Inclusion of the Bc contribution can reduce the current L3 limit on tan β/ MH from 0.38 GeV −1 (90% CL) down to 0.27 GeV −1 (90% CL). 相似文献
9.
Fluorescence decay curves for 5,10,15,20-tetrakis(4-sulfonatophenyl)-21H,23H-porphine tetraanion (TPPS 4−) have been measured in the absence and presence of the methylviologen dication (MV 2+) with various ionic strengths in methanol. In the presence of MV 2+ the fluorescence decays can be expressed by a double exponential function, I( t = I1exp(− t/τ 1) + I2exp(− t/τ 2). The contribution by the faster decay component to the total fluorescence signal increases with increasing MV 2+ concentration. The faster decay process is attributed to fluorescence from the excited state of a solvent-separated ion pair (SSIP) formed between TPPS 4− and MV 2+, and the slower process is attributed to fluorescence from free TPPS 4− ions in the solution. Rate constants for the quenching of fluorescence from free TPPS 4− by MV 2+ ( kq) and formation constants for the SSIP ( KSSIP) were calculated and both are found to decrease with increasing ionic strength. The decrease in kq and KSSIP values can be interpreted in terms of the shielding of electrostatic attraction between the ions. 相似文献
10.
The π 0 spectrum in the KL0 → 3π decay was measured using a wire chambers magnetic spectrometer. In the usual approximation, the matrix element can be expressed as: M2 ≈ 1 + 2 a0( MK/ Mπ2)(2 Tπ0− Tπ0max) + a1( MK2/ Mπ4)(2 Tπ0− Tπ0max) 2. We obtained a0 = −0.282 ± 0.011 and a1 consistent with zero. 相似文献
11.
We study the ρ 0 and φ decays into π +π −γ, π 0π 0γ and φ into π 0ηγ using a chiral unitary approach to deal with the final state interaction of the MM system. The final state interaction modifies only moderately the large momenta tail of the photon spectrum of the ρ 0→π +π −γ decay. In the case of φ decay the contribution to π +π −γ and π 0π 0γ decay proceeds via kaonic loops and gives a distribution of ππ invariant masses in which the f0(980) resonance shows up with a very distinct peak. The spectrum found for φ→π 0π 0γ decay agrees with the recent experimental results obtained at Novosibirsk. The branching ratio for φ→π 0ηγ, dominated by the a0(980), is also in agreement with recent Novosibirsk results. 相似文献
12.
The time-dependence of the decay rate of initially pure K 0 into the final state (π +π −π 0) has been studied in search for the decay k S0→π +π −π 0. No evidence is found in a sample of 384 observed events. The ratio of the CP -violating K S0 amplitude and the K L0 amplitude is η +−0 = (0.13 −0.20+0.17) + i(0.17 −0.26+0.27); the ratio of the CP-conserving K S0 amplitude and the K L0 amplitude is < 0.4. The energy dependence of the K 0→π +π −π 0 matrix element is found to be a+−0 = −0.31 ± 0.03. 相似文献
13.
We present constraints on the relative photoproduction cross sections of positive parity pentaquark states, Σ 5, Λ 5, and N5, based on a minimum phenomenology gained in
and their baryon–meson couplings as in the work of Close and Dudek. The possibility of anomalous signals in γ p→ K0S(Θ +;Σ d+) is discussed. We emphasize the importance of comparing
with “conventional” states such as γ N→ KΣ(1660). 相似文献
14.
The reactions π −p → 2π −π +p, π −p → 2π −π +π op and π −p → 2π −2π +n are analysed at 11 and 16 GeV/ c using longitudinal phase space (LPS) plots. The weighted LPS distributions for π −p → 2π −π +p is dominated by two well separated structures corresponding to single diffraction dissociation of the pion, π −p → (2π −π +)p, and of the proton, π −p → π −(π −π +p). The former is more abundant than the latter, and both are approximately constant with energy. In contrast, processes of type π −p → (2π)(πp) decrease with increasing energy. In the five-body reactions the weighted LPS distribution reveals especially at 16 GeV/c a maximum for single dissociation of the proton into 3πp, namely π−p → π−(π−π+πop); this process is likely to be diffractive. The neutron channel has a corresponding maximum displaced toward a multiperipheral configuration π−p → π−(π−2π+)n. Another strong maximum corresponds to the pion dissociation π−p → (2π−π+πo)p. This is interpreted to be an ω-exchange process because no analogous structure occurs in π−p → (2π−2π+)n. Finally, a broad structure reveals double dissociation of both incident particles; it occurs in the two channels π−p → (2π−π+)(πop) and π−p → (2π−π+)(π+n), being stronger in the latter. Further analysis of this process in terms of isospin exchange suggests that it is partially diffractive. Factorization is also discussed. An appendix gives general aspects of the LPS analysis for the asymptotic study of n-body collisions at very high energy. 相似文献
15.
The static quadrupole moments of the first excited Jπ = 2 + states in 20Ne and 22Ne and the reduced electric quadrupole transition probabilities of these states to the ground states were measured via projectile Coulomb excitation. The quadrupole moments were deduced from the shapes of γ-ray angular distributions. The results are: Q( 20Ne, 2 +) = −0.20±0.05 b and Q( 22Ne, 2 +) = −0.11±0.05 b. The transition strengths were deduced from yield measurements and by comparison with the yields of target γ-rays. The results are: B(E2; 0 + → 2 +, 20Ne) = 0.037±0.003 e2 · b 2 and B(E2; 0 + → 2 +, 22Ne) = 0.025±0.002 e2· b 2. The results for the transition strengths are consistent with the results of accurate timing methods and resolve discrepancies between previous experiments. The results for the quadrupole moments are consistent with earlier measurements, although the mean values we obtain are slightly lower. The experimental measurements are compared with theoretical predictions and a detailed discussion is given of corrections to this type of reorientation experiment. 相似文献
16.
The average g factors of high-spin states in 180,182,184Pt were measured by the transient-field technique. In all three isotopes the quasicontinuum g factor at an angular momentum of 20 is g0.37. This contrasts with similar measurements on other nuclei that have 70 Z80, where typical values of g0.22 have been attributed to the influence of quasineutron alignments. Evidently proton and neutron configurations are about equally important at high spin in the Pt isotopes near mid-shell. This inference is consistent with the discrete spectroscopy, including the contention, supported by gK− gR values, that h9/2 proton pairs align along with the i13/2 neutrons at rotational frequencies of ω≈0.3 MeV in 184Pt. Links between the quasicontinuum g factors and features in the discrete spectroscopy are explored by comparing and contrasting the behavior of 184Pt and 166Hf. 相似文献
17.
The hyperspherical formalism is applied in the framework of the microscopic generator-coordinate method. Three-cluster systems are described with a single generator coordinate, the hyperradius. This model is a natural extension of previous microscopic theories, and can be applied to bound states and resonances in a range of nuclei exhibiting a cluster structure. As an illustrative example, the model is applied to 6He and 6Li. Density distributions and electric dipole transition strengths are calculated, including B( E2;0 +→2 +) in 6He. The results are consistent with a neutron halo structure for the ground state of 6He, and with a proton–neutron halo structure of its isobaric analog state in 6Li. No 1 − “soft dipole” resonance is found in 6He. 相似文献
18.
We calculate the corrections to various low-energy theorems concerning the behaviour of the pseudoscalar meson form factors near t=0. In particular we discuss (i) the Ademollo-Gatto theorem, (ii) Sirlin's relation between the Kl3 form factor ƒ +Kπ( t) and the electromagnetic form factors, (iii) the Callan-Treiman relation, and (iv) the Dashen-Weinstein relation, which connects the slope λ 0 of ƒ 0Kπ( t) with the ratio FK/ Fπ. Furthermore, we point out a remarkable isospin breaking effect which is clearly visible in the experimental rates of the decays K +→π 0e +ν, K 0→π −e +ν. 相似文献
19.
An 879.9(2) keV γ-ray transition has been identified following the β decay of 58V and assigned as the 2 +1→0 +1 transition in 58Cr 34. A peak in the energies of the first excited 2 + states for the even–even chromium isotopes is now evident at 56Cr 32, providing empirical evidence for a significant subshell gap at N=32. The appearance of this neutron subshell closure for neutron-rich nuclides may be attributed to the diminished π1 f7/2–ν1 f5/2 monopole proton–neutron interaction as protons are removed from the 1 f7/2 single-particle orbital. 相似文献
20.
We introduce a new parameterization of four-fermion operator matrix elements which does not involve quark masses and thus allows a reduction of systematic uncertainties. In order to simplify the matching between lattice and continuum renormalization schemes, we express our results in terms of renormalization group invariant B-parameters which are renormalization-scheme and scale independent. As an application of our proposal, matrix elements of Δ I=3/2 and SUSY Δ S=2 operators have been computed. The calculations have been performed using the tree-level improved Clover lattice action at two different values of the strong coupling constant (β=6/ g2=6.0 and 6.2), in the quenched approximation. Renormalization constants and mixing coefficients of lattice operators have been obtained non-perturbatively. Using lowest order χPT, we also obtain ππ| O7| KNDRI=2=(0.11±0.02) GeV 4 and ππ| O8| KNDRI=2=(0.51±0.05) GeV 4 at μ=2 GeV. 相似文献
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