On Fliessbach's approaches to direct reactions

The conventional models of direct cluster reactions treat the nuclear wave-function overlaps or reduced-width amplitudes as single-particle wave functions, which is contrary to the Pauli principle. The motivation of Fliessbach's two approaches reviewed in this paper is to improve on these models by a proper treatment of antisymmetrization. Fliessbach's approaches involve redefined reduced-width amplitudes, which can be regarded as single-particle wave functions. We show, however, that in the approach specialized to transfer reactions the antisymmetrization is in fact treated incorrectly, and the more general approach seems applicable only to processes that involve just two nuclear fragments, like a decay or radiative capture. We outline how single-particle wave functions can be used correctly in approximating reduced-width amplitudes. We show that our approach helps to bring the phenomenological spectroscopic factors into agreement with the nuclear structure models.     

Multiphonon decay of strong mode in quantum lattice

A nonperturbative theory of multiphonon anharmonic decay of strongly excited local mode is developed whereby the mode is considered classically and phonons, quantum mechanically. The decay rate of the mode is expressed via the negative frequency parts of the phonon pair correlation functions. In the case of two-phonon decay the later satisfy the linear integral equations while in the case of two- and more-phonon decay they satisfy the nonlinear integral equations. As a result, the processes mentioned differently depend on the mode amplitude A: two-phonon processes smoothly deminish if A → ∞ while three- and more-phonon processes are fully switched-off at large amplitudes and they abruptly switch-on if the amplitude approaches the critical value. At that the decay rate gets rather high value (of the order of the mode quantum per period). The final stage of the relaxation is well described by the perturbation theory.     

Where do we stand with calculations of the two-neutrino double beta decay rates?

Alternative approaches to the calculation of two-neutrino double beta decay amplitudes are suggested which include neither the evaluation of the intermediate nucleus spectrum nor the closure approximation.Dedicated by the co-author to the memory of M. Gmitro.We wish to thank V. Belyaev, S. Bilenky, R. Eramzhyan, A. Ovchinnikova and E. Truhlik for interest and discussions.     

Description of two-proton radioactivity on the basis of methods of the quantum theory of ternary nuclear fission

The two-proton decay of spherical nuclei is investigated on the basis of the formalism developed in constructing the quantum-mechanical theory of ternary fission. The proposed method for determining the amplitudes of partial widths with respect to two-proton decay and the asymptotic behavior of the wave function for a decaying nucleus makes it possible to solve the problem of describing two-proton radioactivity without recourse to the traditionally used (in R-matrix approaches) cumbersome procedure of matching the internal and the external wave function for the decaying nucleus within the three-body formulation. In the diagonal approximation and with allowance for the properties of the potential describing the interaction of the products of two-proton decay, the structure of the wave function for the Cooper pair of two protons bound in the parent nucleus is analyzed, along with the behavior of the wave function describing the potential scattering of the products of binary decay, the coupling of decay channels being taken into account in this analysis.     

Study of (∧) decay parameter in J/ψ→∧(∧)decay

The helicity amplitudes fot J/ψ→∧(∧)and the relevant background decays are presented for measuring the A decay parameter α+((∧)→(p)π)in J/ψ→∧(∧).The Monte Carlo(MC)simulations based on the helicity amplitudes information are carried out.The likelihood fit method to determine the A decay parameter is presented.Based on the MC generated sample,the sensitivity of the measurement for α+has been estimated,which shows that the J/ψ→∧(∧) channel can be used to measure the A decay parameter α+((∧)→(p)π+)well.     

Analysis of directCP violation in B^- \to D^0 D_s^-, D^0 D^- decays

We show that the semi-leptonic decay can be used as a source of information for two-pion distribution amplitudes. The connection between these amplitudes and the B-meson decay width is achieved by the light cone sum rule method. We show the relevant distribution amplitudes and give the formula for the decay width. Received: 11 April 2001 / Published online: 19 July 2001     

Quantification of fluorescent molecules in heterogeneous media by use of the fluorescence decay amplitude analysis

In heterogeneous media, including biological objects, fluorescent molecules of one kind often exist as a mixture of species with different fluorescence parameters. Fractional concentrations of these species can be measured by analyzing their fluorescence decay amplitudes. The amplitudes are linear functions of concentrations of actually fluorescent molecules, i.e., molecules whose fluorescence decay can be measured. Other (quenched) molecules do not influence these amplitudes. The other parameter that has to be measured to calculate these concentrations is the radiative rate constant. The parameter can be excluded by comparison of decay amplitudes of the sample studied and a standard. The comparison should be made taking into account the dependence of the radiation rates on emision wavelength. The method has been tested in experiments with the fluorescent probe 3-methoxybenzanthrone (MBA) bound with phosphatidylcholine bilayer membranes. The probe has a complex fluorescence decay in these membranes. The decay can be described as two exponentials, with decay times of 2 and 12 ns and a blue-shifted fluorescence spectrum of the short-life component as compared with long-life one. The shift was used to correct calculated radiative rate values. After this, about 100% of the MBA molecules were found to be fluorescent in these membranes. Thus, this approach can be used to measure absolute concentrations of subpopulations of fluorescent molecules in heterogeneous biological objects.     

Deviations from the ΔI = 12 rule and nonlocal effect on the weak current-current interaction

Sum rules for deviations from the $\text{ΔI =}\text{1}\text{2}$ rule are discussed both for S- and P-wave hyperon decay amplitudes. The observed deviations for the P-wave decay amplitudes suggest that a nonlocal effect on the weak current-current interaction is not negligible.     

Measurement of polarization and triple-product correlations in B-->phiK* decays

We present measurements of decay amplitudes and triple-product correlations in B-->phiK* decays based on 253 fb(-1) of data recorded at the Upsilon(4S) resonance with the Belle detector at the KEKB e(+)e(-) storage ring. The decay amplitudes for the three different helicity states are determined from the angular distributions of final-state particles. The longitudinal polarization amplitudes are found to be 0.45 +/- 0.05 +/- 0.02 for B0-->phiK(*0) and 0.52 +/- 0.08 +/- 0.03 for B+ -->phiK(*+) decays. CP- and T-odd CP-violating triple-product asymmetries are measured to be consistent with zero.     

Excited states in a bethe-salpeter model for baryons

Baryon Bethe-Salpeter amplitudes for excited states are constructed in a Bethe-Salpeter model with harmonic oscillator interaction using the spinstructure of the ground states. The amplitudes are applied to a calculation of pionic strong decay width of some excitations and the results are compared with experiment.     

High-reflectivity measurement with a broadband diode laser based cavity ring-down technique

A simple cavity ring-down technique employing a cw broadband diode laser is described for the reflectivity measurements of highly reflective mirrors. Due to the broad line width of the diode laser, the laser beam can be continuously injected into the ring-down cavity without tuning the cavity length or the laser frequency. Both Fourier- and time-domain data-processing approaches are developed to determine the reflectivity. In the Fourier domain, the amplitudes and phase shifts of the first and third harmonics of a periodic ring-down signal are measured as a function of the modulation frequency covering an appropriate range. The cavity decay time and the reflectivity of the cavity mirror are determined by minimizing a mean square variance containing both the amplitude and phase-shift error terms. On the other hand, in the time domain, the cavity decay time and the instrumental response time are determined simultaneously by fitting the measured waveforms of the cavity ring-down signals to a rigorous time-domain model via a multi-parameter fitting procedure. The reflectivity measurements are repeated at four cavity lengths and all the results obtained with both data-processing approaches are in excellent agreement. The reflectivity of cavity mirrors near 830 nm is statistically determined to be 0.99797 with an uncertainty less than 3×10^-5. PACS 07.60.Hv; 42.60.Da; 42.55.Px     

Weak radiative decay of baryons

The decay amplitudes and asymmetry parameters for weak radiative decay of baryons are calculated in both pole model and quark model. It is demonstrated that both models give the same results and the results satisfy the symmetry relations we have derived recently. The agreement of the theoretical prediction with the presently measured decay rates and asymmetry is quite good in view of uncertainty in the calculation.     

Covariant Helicity Amplitude Analysis for J／ψ→γPP

Covariant helicity amplitude analysis for the process of J/ψ→γPP is discussed starting from the Smatrix elements of decay process,we deduce the formulae of helicity coupling amplitudes for two-body decay process,These formulae are used to analyze intermediate resonance states in the process of J/ψ decay to γππ,γKK,γηη′     

Baryon-baryon and baryon-antibaryon interaction amplitudes in the spin-momentum operator expansion method

Partial-wave scattering amplitudes in baryon-baryon and baryon-antibaryon collisions and amplitudes for the production and decay of baryon resonances are constructed in the framework of the spin-momentum operator expansion method. The approach is relativistically invariant and it allows us to perform combined analyses of different reactions imposing analyticity and unitarity directly. The role of final-state interactions (triangle and box diagrams) is discussed.     

Proton decay in terms of an effective baryon-lepton transition

We calculate the two-body decay rates for the hadronic and electromagnetic decays of proton and neutron in terms of the effective baryon-lepton transition matrix element. Further ingredients like PCAC and vector meson dominance are used. We compute these transition amplitudes within the framework of a relativistic quark model involving Bethe-Salpeter amplitudes and present the nucleon lifetimes and branching ratios of various decay modes for three different grand unification models.     

The acoustic signature of bubbles fragmenting in sheared flow

Measurements of the sound of bubbles fragmenting in fluid shear are presented and analyzed. The frequency, amplitude, and decay rate of the acoustic emissions from 1.8-mm-radius bubbles fragmenting between opposed fluid jets have been determined. A broad band of frequencies (1.8 to 30 kHz) is observed with peak pressure amplitudes in the range of 0.03 to 2 Pa. While the peak pressure amplitudes show no significant scaling with frequency, the frequency dependence of the decay rates is consistent with the sum of thermal and acoustic radiation losses.     

Recoil corrected bag model calculations for semileptonic weak decays

We develop recoil corrections to various bag model results for strangeness changing weak decay amplitudes. It is shown that the spurious reference frame dependence of earlier calculations is reduced. The second class currents are generally less important than obtained by calculations in the static approximation. Finally, theoretical results are compared to observations. The agreement is quite good, although the values for the Cabibbo angle obtained by fits to the decay rates are somewhat too large.     

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.     

Baryon number violating nuclear decay

The expressions for baryon number violating nuclear partial decay widths are derived from the interactions as predicted by grand unified theories. Theory predicts that the baryon number violating proton decay inside the nucleus is hindered relative to the free proton decay rate. In the case of closed shell nuclei, the meson spin-isospin dependence of the partial width is the same as that for the nucleon decay. The branching ratios of decay amplitudes depend on the nuclear binding energies. Nuclear structure introduces lepton energy spread of ±49.5 MeV for light closed shell nuclei, while it does not affect the back to back emission of lepton-meson pair.     

Measurement of branching fractions and polarization in B-->phiK(*) decays

We present the first measurement of decay amplitudes in B-->phiK* and measurements of branching fractions in B-->phiK(*) decays based on 78.1 fb(-1) of data recorded at the Upsilon(4S) resonance with the Belle detector at the KEKB e+e- storage ring. The decay amplitudes for the different phiK*0 helicity states are measured from the angular distributions of final state particles in the transversity basis. The longitudinal and transverse complex amplitudes are |A0|2=0.43+/-0.09+/-0.04, |A(perpendicular)|2=0.41+/-0.10+/-0.04, arg((A(parallel))=-2.57+/-0.39+/-0.09, and arg((A(perpendicular))=0.48+/-0.32+/-0.06. The direct CP-violating asymmetries are found to be consistent with zero.