Decay of an ultracold fermionic lithium gas near a Feshbach resonance

We studied the magnetic field dependence of the inelastic decay of an ultracold, optically trapped fermionic 6Li gas of different spin compositions. The spin mixture of the two lowest hyperfine states showed two decay resonances at 550 and 680 G, consistent with the predicted Feshbach resonances for elastic s-wave collisions. The observed lifetimes of several hundred ms are much longer than the expected time for Cooper pair formation and the phase transition to superfluidity in the vicinity of the Feshbach resonance.     

Angular correlations in the decays of two unstable identical particles with close momenta

For the decay of two identical particles with close momenta, the angular correlations between the directions of emission of decay products are considered on the basis of the model of independent single-particle sources emitting unstable unpolarized particles of nonzero spin. These correlations reflect spin correlations that are caused by quantum-statistics and final-state-interaction effects. A general theory of angular correlations in the decays of two arbitrarily polarized particles (resonances) is constructed.     

Chiral-symmetry realization for even- and odd-parity baryon resonances

Baryon resonances with even and odd parity are collectively investigated from the viewpoint of chiral symmetry (ChS). We propose a quartet scheme where Delta's and N(*)'s with even and odd parity form a chiral multiplet. This scheme gives parameter-free constraints on the baryon masses in the quartet, which are consistent with observed masses with spin 1 / 2,3 / 2,5 / 2. The scheme also gives selection rules in the one-pion decay: The absence of the parity nonchanging decay N(1720)-->piDelta(1232) is a typical example which should be confirmed experimentally to unravel the role of ChS in baryon resonances.     

Pion production via isobar giant resonance formation and decay

A spin, isotopic-spin formalism for the production of pions due to decays of isobar giant resonances formed in peripheral heavy-ion collisions is presented. The projectile nucleus isobar giant resonance state is assumed to coherently form and then incoherently decay to produce the pions. Total spin and isotopic spin for the system are conserved through the concomitant excitation of the target nucleus to an isobaric analog giant resonance state. Comparisons of the predicted total pion cross sections, over a range of energies, are made with heavy-ion pion data.     

Holographic hadro-quarkonium

We consider the recently suggested model for some resonances near the open charm threshold as bound states of charmonium inside excited light mesons. It is argued in the soft-wall holographic model of QCD that such states of heavy quarkonium necessarily exist at sufficiently large spin of the light meson. The bound state is provided by the dilaton exchange through the 5D bulk. We also argue that the decay of such bound systems into mesons with open heavy flavors due to splitting of the heavy quarkonium can be treated as semiclassical tunneling and is suppressed. This behavior is in agreement with the known relative suppression of the decay of the discussed charmonium-like resonances into channels with D mesons.     

Phase Coherence and Spin Squeezing in One-Axis Twisting Model with Decay

We investigate phase coherence and spin squeezing of a collective spin governed by one-axis twisting Hamiltonian with decay. Here we are interested in the dependence of phase coherence and spin squeezing parameter on the decay. The analytical expressions of phase coherence and spin squeezing parameter are obtained. The stronger decay can induce a stronger spin squeezing, and the squeezing can maintain a longer time interval. Moreover, more squeezing can be achieved by increasing the number of particles.     

Spontaneous dissociation of long-range Feshbach molecules

We study the spontaneous dissociation of diatomic molecules produced in cold atomic gases via magnetically tunable Feshbach resonances. We provide a universal formula for the lifetime of these molecules that relates their decay to the scattering length and the loss rate constant for inelastic spin relaxation. Our universal treatment as well as our exact coupled channels calculations for 85Rb dimers predict a suppression of the decay over several orders of magnitude when the scattering length is increased. Our predictions are in good agreement with recent measurements of the lifetime of 85Rb(2).     

Nonsecular contribution to the decay of spin-echo signals of quadrupolar nuclei in magnetically ordered materials

We analyze the influence of fluctuations of the nonsecular part of the spin Hamiltonian on the decay of ordinary and multiquantum signals of the two-pulse spin echo in a quadrupole spin system with an inhomogeneously broadened spectral line. Expressions are obtained for the rate of decay of an echo in the case of selective excitation of a signal from quadrupole nuclei with arbitrary spin. These expressions are then used to analyze the experimentally observed ordinary and multiquantum echo signals from quadrupole nuclei with spin I=3/2 (⁵³Cr, ⁶³Cu, and ⁶⁵Cu) in ferromagnetic chromium chalcogenide spinels. Zh. éksp. Teor. Fiz. 116, 204–216 (July 1999)     

Decay of rabi oscillations induced by magnetic dipole interactions in dilute paramagnetic solids

Decay of Rabi oscillations of equivalent spins diluted in diamagnetic solid matrix and coupled by magnetic dipole interactions is theoretically studied. It is shown that these interactions result in random shifts of spin transient nutation frequencies and thus lead to the decay of the transient signal. Averaging over random spatial distribution of spins within the solid and over their spectral positions within magnetic resonance line, we obtain analytical expressions for the decay of Rabi oscillations. The rate of the decay in the case when the half-width of magnetic resonance line exceeds Rabi frequency is found to depend on the intensity of resonant microwave field and on the spin concentration. The results are compared with the literature data for E′₁ centers in glassy silica and [AlO₄]⁰ centers in quartz.     

Complete angular analysis of the decay cascadeB→D ** (→D *(→Dπ)+π+W(→lv)

We develop a general algorithm for describing angular decay distributions in cascade decay chains of arbitrary length. The general algorithm is used to study joint angular decay distributions for the cascade decayB→D ^**(→D ^*(→Dπ)+W(→lv) where theD ^** is a genericP-wave charm meson state. Lepton mass effects are fully incorporated. The joint angular decay distribution depend on 43 independently measurable decay parameters if the spin parity of theD ^** is 1⁺ and on 48 decay parameters if the spin parity of theD ^** is 2⁺. We give expressions for these decay parameters in terms of the helicity amplitudes of the two-body decay processes. An absolute prediction for all the parameters is presented in the framework of the heavy quark effective theory. A method for obtaining the helicity amplitudes from measured joint angular distributions is suggested.     

Controlling Spin Squeezing in One-Axis Twisting with Decay

We investigate how an appropriate choice of the external field allows one to control spin squeezing of a collective spin governed by one-axis twisting with decay. By adopting frozen-spin approximation, we succussed in obtaining analytical expressions of the optimally squeezing angle and the spin squeezing parameter. The squeezing parameter is a periodical function, the period depends on the decay rate and the strength of the linear interaction, while the degree of squeezing is only determined by the external field, the smaller external field induces the stronger spin squeezing.     

Production of heavy resonances with electron and muon beams

The inelastic leptoproduction of heavy resonances J (J = J/ψ, Ψ,…) is investigated in a model where γ_vg → Jg is assumed to be the dominant mechanism. Analytic expressions for the differential cross section as well as for the helicity amplitudes are presented. A detailed numerical analysis of the angular distribution of the muon pair arising from the decay of the heavy resonance in its rest frame is presented.     

Top quark production at hadron colliders: Some useful formulae

We present compact expressions for the amplitudes describing production and decay of heavy top-anti-top quark pairs in hadron-hadron collisions. We include both the effects of a finite width of the W particles in the top quark decay and those of a non-zerob quark mass, as well as the complete spin correlations in the decays. Also a very compact analytical result for the width of the top quark including all these effects is given.     

Higher order spin resonances in a 2.1-GeV/c polarized proton beam

Spin resonances can depolarize or spin flip a polarized beam. We studied 1st and higher order spin resonances with stored 2.1 GeV/c vertically polarized protons. The 1st order vertical (ν(y)) resonance caused almost full spin flip, while some higher order ν(y) resonances caused partial depolarization. The 1st order horizontal (ν(x)) resonance caused almost full depolarization, while some higher order ν(x) resonances again caused partial depolarization. Moreover, a 2nd order ν(x) resonance is about as strong as some 3rd order ν(x) resonances, while some 3rd order ν(y) resonances are much stronger than a 2nd order ν(y) resonance. One thought that ν(y) spin resonances are far stronger than ν(x), and that lower order resonances are stronger than higher order; the data do not support this.     

High resolution proton inelastic scattering from 50Cr

Resonances in the ⁵⁰Cr(p, p′γ) reaction were investigated with the TUNL high resolution system. All previously observed p-wave resonances between Ep = 2.00 and 3.03 MeV were studied. Measurement of the p' and the γ-ray angular distributions provides sufficient information to determine unambiguously the J-value of the resonance and the magnitude and relative phase of the inelastic decay amplitudes. Expressions are given for the appropriate angular distributions and for the transformation between the channel spin and the total angular momentum representation. Experimental results are presented for 24 p-wave resonances in ⁵¹Mn including decay amplitudes and relative phases for $\text{16}\text{3}\text{2}{}^{\mathrm{?}}$ resonances. Six resonances formerly assigned $\text{1}\text{2}{}^{\mathrm{?}}$ are reassigned $\text{3}\text{2}{}^{\mathrm{?}}$. Inelastic spectroscopic factors were determined for two analogue states. Proton strength functions were evaluated from both the elastic and inelastic data.     

On the meaning of the nuclear reaction durations,measured by means of the blocking effect

The expressions for the duration of the nuclear reaction and the compound-nucleus lifetime at a range of strongly over- lapping resonances are generalized. It is shown how the interpretation of the measurements by means of the shadow (blocking) effect is changed when the non-exponential compound-nucleus decay is taken into account. A new method is proposed for obtaining information on the resonance density and width from the measured compound-nucleus lifetimes with the utilization of the optical-statistical analysis.     

Excited levels and isobaric analogue states in55Co investigated with the54Fe(p, γ)55Co reaction

The yield curve for the⁵⁴Fe(p, γ)⁵⁵Co reaction in the energy regionE _p=1.5–2.9 MeV has been recorded and the decay of ten resonances has been investigated. For six of the resonances the strengths have been determined. The angular distributions of the gamma rays have been recorded for four resonances to obtain spins or spin limitations for excited levels. In addition the lifetimes of 10 bound levels were determined with the Doppler Shift Attenuation Method. The isobaric analogues of the ground state and five excited states in⁵⁵Fe are discussed.     

Few-body Decay and Recombination in Nuclear Astrophysics

Three-body continuum problems are investigated for light nuclei of astrophysical relevance. We focus on three-body decays of resonances or recombination via resonances or the continuum background. The concepts of widths, decay mechanisms and dynamic evolution are discussed. We also discuss results for the triple ?? decay in connection with 2⁺ resonances and density and temperature dependence rates of recombination into light nuclei from ??-particles and neutrons.