Gluons in quarkonium decay

We discuss what can be learned from the ³S₁ quarkonium decay $\text{Q}\text{Q}\text{→ 3}\text{gluons}$, $\text{Q}\text{Q}\text{→ γ + 2}\text{gluons}$. The former is a way to find gluon jets and test QCD. The latter also allows us to measure gluon + gluon → hadrons, and look for pure gluonic resonances (glueballs).     

Muon decay in orbit

The decay spectrum of a muon bound in the $\text{1s}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ state of an atom is calculated using V-A theory. Accurate muon and electron wave functions including finite nuclear size effects and vacuum polarization are used for the evaluation of the electron emission spectra of various elements. The formalism to perform the angular integration of the matrix elements is developed for the V-A weak interaction.     

Muon decay in sulphur

The electron spectrum from muon decay in orbit in sulphur was measured at SIN. In the energy range from 54 to 92 MeV, the measurement shows a spectrum compatible with the weak V-A theory within ±35% over the whole range.     

Proton decay

The lifetimes and branching ratios of the proton and bound neutron are calculated in the SO(10) grand unified theory by taking into account the form factor effect (by making use of SU(6) symmetric wave functions for the nucleons and mesons) and the generation mixing, based on the assumption that the ΔB = ? 1 decay interaction is generated by the exchange of superheavy leptoquark gauge bosons, D (X and Y) and E (X' and Y'). In our approach there is a free parameter M_D/M_E, which should be determined by experiment. The branching ratio of the inclusive decay of an I = 0 nucleus into neutrinos and anything is found to be most dependent on the ratio M_D/M_E. The nucleon lifetime is τ_N = [M_D (GeV)/5 × 10¹⁴]⁴ × (0.0015,2.5,4.6) × (1_?0.4⁺²) × 10³⁰ year, for M_D/M_E = (10,1,0.1). Only the cases in which M_DapM_E are found to be possible for Λ_ms[? 0.26 GeV and τ_N ? 5 × 10³⁰ year if there is not a fourth generation of light fermions, technicolored particles nor supersymmetric particles.     

Positronium-ion decay

We present a precise theoretical prediction for the decay width of the bound state of two electrons and a positron (a negative positronium ion), Gamma(Ps-)=2.087 963(12)/ns. We include O(alpha2) effects of hard virtual photons as well as soft corrections to the wave function and the decay amplitude. An outcome of a large-scale variational calculation, this is the first result for second-order corrections to a decay of a three-particle bound state. It will be tested experimentally in the new positronium-ion facility in Garching in Germany.     

Muon decay

Muon decay, after more than fifty years of experimental and theoretical investigations, has been established as a firm basis for the Standard Model of Electroweak Interactions. The decay products of the muon have been identified, and the Lorentz structure of the decay interaction has been determined completely from existing experiments in a model-independent way. Together with the completely anologous leptonic τ decays it continues to be an important and sensitive testing ground for deviations from the Standard Model.     

CP asymmetries in chargino production and decay: the three-body decay case

We study CP violation in chargino production and decay in the minimal supersymmetric standard model (MSSM) with complex parameters at an e⁺e^- linear collider with longitudinally polarised beams. We investigate CP-sensitive asymmetries by means of triple product correlations and study their dependence on the complex parameters M₁ and μ. We give numerical predictions for the asymmetries and their measurability at the future International Linear Collider. Our results show that the CP asymmetries can be measured in a large region of the MSSM parameter space.     

Evaluation of decay times in coupled spaces: Bayesian decay model selection

This paper applies Bayesian probability theory to determination of the decay times in coupled spaces. A previous paper [N. Xiang and P. M. Goggans, J. Acoust. Soc. Am. 110, 1415-1424 (2001)] discussed determination of the decay times in coupled spaces from Schroeder's decay functions using Bayesian parameter estimation. To this end, the previous paper described the extension of an existing decay model [N. Xiang, I. Acoust. Soc. Am. 98, 2112-2121 (1995)] to incorporate one or more decay modes for use with Bayesian inference. Bayesian decay time estimation will obtain reasonable results only when it employs an appropriate decay model with the correct number of decay modes. However, in architectural acoustics practice, the number of decay modes may not be known when evaluating Schroeder's decay functions. The present paper continues the endeavor of the previous paper to apply Bayesian probability inference for comparison and selection of an appropriate decay model based upon measured data. Following a summary of Bayesian model comparison and selection, it discusses selection of a decay model in terms of experimentally measured Schroeder's decay functions. The present paper, along with the Bayesian decay time estimation described previously, suggests that Bayesian probability inference presents a suitable approach to the evaluation of decay times in coupled spaces.     

Alpha decay in electron surrounding

The influence of atomic electron shells on the constant of alpha decay of heavy and mediummass nuclei was considered in detail. A method for simultaneously taking into account the change in the potential-barrier shape and the effect of reflection of a diverging Coulomb wave in the classically allowed region was developed. The ratios of decay probabilities per unit time for a bare nucleus and the respective neutral atom were found for some alpha-decaying isotopes.     

Asymmetries in semi-leptonic hyperon decay

Based on the thermodynamic model for particle production, inclusive two-particle correlations are studied. The model is used to study integrated correlations R⁽²⁾(s) and rapidity correlations at accelerator and ISR energies.Particle production is described via the formation of clusters called fireballs. The average mass of these clusters changes as $\text{s}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext><mtext>w</mtext>}}\text{exp}\text{(? |η|ν), (0 ? ν, w ? 1)}$ with the primary energy s and fireball rapidity η. The model produces in the limiting cases the same correlations as the multiperipheral model (with w = 0) and the diffractive excitation model (with w = 1) but contains also all intermediate cases (0 < w < 1) in which fireballs increasing in mass and number are formed. The average number of fireballs produced is also calculated. At ISR energies integrated correlations R⁽²⁾ and rapidity correlations are very different in the cases $\text{w = 0,}\text{1}\text{2}\text{and}\text{1}$. Therefore, experimental data at high energy on R⁽²⁾(s) or on rapidity correlations will allow one to determine the parameter w. Measurements of these different quantities should result in a consistent picture for the production of fireballs.     

Double-beta decay in gauge theories

Neutrinoless double-beta decay is a very important process both from the particle and nuclear physics point of view. From the elementary particle point of view, it pops up in almost every model, giving rise among others to the following mechanisms: (a) the traditional contributions like the light neutrino mass mechanism as well as the j _L –j _R leptonic interference (λ and η terms), (b) the exotic R-parity-violating supersymmetric (SUSY) contributions. Thus, its observation will severely constrain the existing models and will signal that the neutrinos are massive Majorana particles. From the nuclear physics point of view, it is challenging, because (1) the nuclei, which can undergo double-beta decay, have complicated nuclear structure; (2) the energetically allowed transitions are suppressed (exhaust a small part of all the strength); (3) since in some mechanisms the intermediate particles are very heavy one must cope with the short distance behavior of the transition operators (thus novel effects, like the double-beta decay of pions in flight between nucleons, have to be considered; in SUSY models, this mechanism is more important than the standard two-nucleon mechanism; and (4) the intermediate momenta involved are quite high (about 100 MeV/c). Thus one has to take into account possible momentum-dependent terms of the nucleon current, like modification of the axial current due to PCAC, weak magnetism terms, etc. We find that, for the mass mechanism, such modifications of the nucleon current for light neutrinos reduce the nuclear matrix elements by about 25%, almost regardless of the nuclear model. In the case of heavy neutrino, the effect is much larger and model-dependent. Taking the above effects into account, the needed nuclear matrix elements have been obtained for all the experimentally interesting nuclei A=76, 82, 96, 100, 116, 128, 130, 136, and 150. Then, using the best presently available experimental limits on the half-life of the 0νββ decay, we have extracted new limits on the various lepton-violating parameters. In particular, we find 〈m _ν〉 < 0.3 eV/c ², and, for reasonable choices of the parameters of SUSY models in the allowed SUSY parameter space, we get a stringent limit on the R-parity-violating parameter λ′₁₁₁<4.0×10^?4.     

Oscillations in radioactive exponential decay

Several older and recent reports provided evidence for the oscillatory character of the exponential decay law in radioactive decay and attempted to explain it with basic physics. We show here that the measured effects observed in some of the cases, namely in the decay of ²²⁶Ra, ³²Si in equilibrium, and ³⁶Cl, can be explained with the temperature variations.     

Luminescence decay in AgCl crystals

The kinetics of luminescence decay of single crystal plates of AgCl was measured at the temperature of liquid nitrogen. Luminescence decay first takes place (fort≦2·5× ×10^?3 sec) according to a hyperbole and then according to an exponential. The constantsa anda of the hyperbolic andt of the exponential dependence were measured for different intensity of the exciting radiation in normal and deformed samples and in samples irradiated withb-particles during measurement.     

Bremsstrahlung in alpha decay reexamined

A high-statistics measurement of bremsstrahlung emitted in the alpha decay of (210)Po has been performed, which allows us to follow the photon spectra up to energies of approximately 500 keV. The measured differential emission probability is in good agreement with our theoretical results obtained within the quasiclassical approximation as well as with the exact quantum mechanical calculation. It is shown that, due to the small effective electric dipole charge of the radiating system, a significant interference between the electric dipole and quadrupole contributions occurs, which is altering substantially the angular correlation between the alpha particle and the emitted photon.     

Exotic decay in cerium isotopes

Half life for the emission of exotic clusters like ⁸Be, ¹²C, ¹⁶O, ²⁰Ne, ²⁴Mg and ²⁸Si are computed taking Coulomb and proximity potentials as interacting barrier and many of these are found well within the present upper limit of measurement. These results lie very close to those values reported by Shanmugam et al using their cubic plus Yukawa plus exponential model (CYEM). It is found that ¹²C and ¹⁶O emissions from ¹¹⁶Ce and ¹⁶O from ¹¹⁸Ce are most favorable for measurement (T _1/2<10¹⁰ s). Lowest half life time for ¹⁶O emission from ¹¹⁶Ce stress the role of doubly magic ¹⁰⁰Sn daughter in exotic decay. Geiger-Nuttall plots were studied for different clusters and are found to be linear. Inclusion of proximity potential will not produce much deviation to linear nature of Geiger-Nuttall plots. It is observed that neutron excess in the parent nuclei slow down the exotic decay process. These findings support the earlier observations of Gupta and collaborators using their preformed cluster model (PCM).     

T violation in neutralino decay

We show that in the supersymmetric standard electroweak theory the neutralino decay causesCP violating phenomena. It will be possible to observeT odd asymmetry in the angular distribution if the trilepton decay of theW boson is found. We also discuss the constraint on the magnitude ofCP violation by the electric dipole moment of the neutron.     

Sequential decay in physical representation

Working in a physical representation, we discuss the problem of sequential decay of a discrete 3-level system interacting with boson fields. In such a representation, energy levels are sharp and collision processes conserve the energy. Nevertheless, 2-boson processes induce a broadening of the lines around $\text{(Ω}{}_2\text{? Ω}{}_1\text{), (Ω}{}_1\text{? Ω}{}_0\text{)}$; both lines have the same width and are truncated at (Ω₂ ? Ω₀). In contradistinction, Weisskopf-Wigner's idea of broad energy levels leads, in general, to lines with different widths and no upper limit.At t = 0, the distributions of bare and physical bosons are different; they become identical at t = ∞. The main difference between the two representations lies in the dynamics. Any bare boson can be emitted. In a 2-level model, only resonant physical bosons can be emitted; in a 3-level model, non resonant physical bosons can be emitted only with energy lower than (Ω₂ ? Ω₀); all other bosons must have been brought through the excitation mechanism.     

Proton decay in E6

It is shown that nucleon decay modes mediated by E₆ gauge bosons are identical to those occuring in O(10).