Decay Law of Moving Unstable Particle

Quantum relativistic decay law of moving unstable particle is analytically calculated in the model case of the Breit–Wigner mass distribution. It turns out that Einstein time dilation of the moving particle decay holds approximately at times when the decay is exponential. The related correction is calculated analytically. Being very small at these times it is practically unobservable. It is shown that Einstein dilation fails for large times t when decay is not exponential. An unstable system of the kind of K ₀-meson (which is the superposition of K _s and K _I) is also considered. In this case, the violation of Einstein dilation is shown to be appreciable at all times under some condition     

Interpretation of the recent Kolar events

We give plausible interpretations of the unusual events seen in the proton decay detector at Kolar Gold Fields indicating the existence of a massive (≳2GeV) long lived (10⁻⁸−10⁻⁹s) particle. We show that it is possible to accommodate the particle in the standard model as a fourth generation neutrino, or inE ₆ grand unified theory as a neutral fermion occurring in27 representation or in supersymmetric theory as a scalar neutrino. However, there is a difficulty in explaining the large production rate for the particle.     

ψ(3770) and B meson exclusive decay B → ψ(3770)K in QCD factorization

Belle has observed surprisingly copious production of ψ(3770) in the B meson decay B → ψ(3770)K, whose rate is comparable to that of B → ψ(3686)K. We study this puzzling process in the QCD factorization approach with the effect of the S-D mixing considered. We find that the soft scattering effects in the spectator interactions play an essential role. With a proper parametrization for the higher-twist soft end-point singularities associated with kaon, and with the S-D mixing angle θ = - 12^°, the calculated decay rates can be close to the data. Implications of these soft spectator effects to other charmonium production in B exclusive decays are also emphasized.     

On the Importance of the Bohmian Approach for Interpreting CP-Violation Experiments

We argue that the inference of CP violation in experiments involving the K⁰-K⁰ system in weak interactions of particle physics is facilitated by the assumption of particle trajectories for the decaying particles and the decay products. A consistent explanation in terms of such trajectories is naturally incorporated within the Bohmian interpretation of quantum mechanics.     

Ni27+ 离子Kα和Kβ 型衰变的双电子复合速率系数的计算

用HFR波函数对低密度类氢Ni²⁷⁺等离子体与电子相互作用的KLn和KMn共振激发的双电子复合过程进行了细致的理论计算研究.根据可能的重要辐射衰变通道，分析了Ni²⁷⁺等离子体Kα 型和Kβ 型辐射衰变的双电子复合速率系数随旁观电子主量子数n和轨道角动量量子数l与电子温度的变化行为，计算了Ni²⁷⁺等离子体双电子复合过程的总速率系数.研究结果表明，在低密度条件下，Kα 型和Kβ型辐射衰变的分支双电子复合速率系数与旁观电子主量子数n和轨道角动量量子数l有重要关系，前者的分支速率系数远大于后者. 关键词： 27+离子')" href="#">Ni²⁷⁺离子 Kα型和Kβ型辐射衰变')" href="#">Kα型和Kβ型辐射衰变 双电子复合 速率系数     

Kaon-induced $ \Lambda$(1405) production on a deuteron target at DAFNE

The K^--induced production of L \Lambda(1405) in the K ^- d ? \rightarrow p \pi S \Sigma n reaction is investigated having in mind the conditions of the DAFNE facility at Frascati where kaons are obtained from the decay of slow-moving f \phi mesons. We find that the K ^- d ? \rightarrow L \Lambda(1405)n process favors the production of L \Lambda(1405) initiated by the K^-p channel, which gives largest weight to the higher mass L \Lambda(1405) appearing at 1420MeV in chiral theories. We find that the fastest kaons from the decay of the f \phi are well suited to see this resonance, particularly if one selects forward going neutrons in the center of mass, which reduce the contribution of single scattering and make the double scattering dominate where the signal of the resonance appears clearer.     

Part II. Algebraic tails in three-dimensional quantum plasmas

We review various exact results concerning the presence of algebraic tails in three-dimensional quantum plasmas. First, we present a solvable model of two quantum charges immersed in a classical plasma. The effective potential between the quantum charges is shown to decay as 1/r ⁶ at large distances r. Then, we mention semiclassical expansions of the particle correlations for charged systems with Maxwell-Boltzmann statistics and short-ranged regularization of the Coulomb potential. The quantum corrections to the classical quantities, from orderh ⁴ on, also decay as 1/r ⁶. We also give the result of an analysis of the charge correlation for the one-component plasma in the framework of the usual many-body perturbation theory; some Feynman graphs beyond the random phase approximation display algebraic tails. Finally, we sketch a diagrammatic study of the correlations for the full many-body problem with quantum statistics and pure 1/r interactions. The particle correlations are found to decay as 1/r ⁶, while the charge correlation decays faster, as 1/r ¹⁰. The coefficients of these tails can be exactly computed in the low-density limit. The absence of exponential screening arises from the quantum fluctuations of partially screened dipolar interactions.     

Q value related mass determinations using a Penning trap

We report here about measurements of reaction and decay Q values by precise determination of pairs of atomic masses. These were performed with the Penning trap mass spectrometer SMILETRAP. Measurements with Penning traps give reliable and accurate masses, in particular Q values, due to the fact that certain systematic errors to a great deal cancel in the mass difference between the two atoms defining the Q value. Some Q values that are of fundamental interest will be discussed here, for example, a new Q value for the ⁶Li (n,γ) ⁷Li reaction, for the β-decay of tritium, related to properties of the electron neutrino mass, and for the neutrino-less double β-decay of ⁷⁶Ge, related to the question of whether the neutrino is a Majorana particle or not. In case of the latter two we report the most accurate Q values, namely 18,589.8(12) eV for the tritium decay and 2,038.997(46) keV for the neutrino-less double β-decay of ⁷⁶Ge.     

Observation of associated Kos-electron production in e+e− annihilation

We have observed K^o_s production in e⁺e^? annihilation between 3.6 and 4.4 GeV CMS energy. In the 4.0–4.1 GeV range K^o_s mesons occur correlated with prompt electrons, indicating the formation and weak decay of charmed particle. Within the sensitivity of the experiment, no K^o_s-electron correlation is seen at 3.6 and around 4.4 GeV.     

Part I. The 2D classical Coulomb gas near the zero-density Kosterlitz-Thouless critical point: Correlations and critical line

The 2D classical Coulomb gas undergoes the famous Kosterlitz-Thouless (KT) transition between a high-temperature conducting phase and a low-temperature insulating phase. We present various studies of the correlations in the insulating phase near the zero-density critical point. First, we briefly recall the phenomenological approach of Kosterlitz and Thouless. This theory predicts that the decay of the charge correlation is entirely controlled by the bare Coulomb potential between opposite charges only renormalized by the dielectric constante. Then, we present an analysis of the low-fugacity expansions of the correlations. The particle correlations are found to decay as 1/r⁴. The large-distance decay of the charge correlation is shown to be tightly related to the behavior of l/s in the regime of interest. Systematic resummations allow one to recover the algebraic decay predicted by the heuristic KT model. This settles on a rigorous basis various assumptions of this model. In particular, the nested pair mechanism naturally arises in the resummation scheme. Finally, we describe the phase diagram of the system according to the most recent calculations which include finite-density effects.     

Search for Lepton Flavor Non-universality with B→ (K,K*) τ+τ- Decays

The decay modes of B meson consisting tau leptons as final state particle are seemed to be the key feature for searching new physics. As the experimental measurements for b → sτ⁺τ⁻ processes are still not confirmed, the theoretical study of these decays is playing vital role in recent times. The lepton flavor universality violation gains much curiosity after the observation of R_K and \( {R}_{K^{\ast }} \) anomalies in semileptonic \( B\to \left(K,{K}^{\ast}\right)\mu \overline{\mu} \) channel which provides a hint towards μ − e non-universality in flavor sector. In this paper, we have devoted our concern to the decay mode B → (K, K^∗)τ⁺τ⁻ to predict the branching ratio. We have also searched for the τ − l (where l = e, μ) lepton flavor non-universality for neutral current transitions. We have estimated our results in the standard model as well as in Z′ model.

     

Strange axial-vector mesons mixing angle

The masses of K ₁(³ P ₁) and K ₁(¹ P ₁) are considered in a nonrelativistic constituent quark model, and the absolute value of the K ₁(³ P ₁)- K ₁(¹ P ₁) mixing angle is determined to be about 59.29^°. The comparison of the theoretical predictions on the strong decay widths of K ₁(1270) and K ₁(1400) in the ³ P ₀ decay model as well as the production ratio of these two states in the τ decay between the available experimental data strongly favors that the K ₁(³ P ₁)- K ₁(¹ P ₁) mixing angle is about +59.29^°.     

A relativistic quark model for mesons with an instanton-induced interaction

We present new results of a relativistic quark model based on the Bethe-Salpeter equation in its instantaneous approximation. Assuming a linearly rising confinement potential with an appropriate spinorial structure in Dirac space and adopting a residual interaction based on instanton effects, we can compute masses of the light mesons up to highest observed angular momenta with a natural solution of the U _A(1) problem. The calculated ground states masses and the radial excitations describe the experimental results well. In this paper, we will also discuss our results concerning numerous meson decay properties. For processes like π⁺/K ⁺↦e ⁺υ_eγ and 0^-↦γγ at various photon virtualities, we find a good agreement with experimental data. We will also comment on the form factors of the K _?3 decay and on the decay constants of the π, K and η mesons. For the sake of completeness, we will furthermore present the electromagnetic form factors of the charged π and K mesons as well as a comparison of the radiative meson decay widths with the most recent experimental data. Received: 28 August 2000 / Accepted: 12 September 2000     

The β function,scaling, and improved action forSU(3) lattice gauge theory

We present a detailed analysis of the nonperturbativeβ function along the Wilson axis for theSU(3) pure gauge theory using the Monte Carlo renormalization group method. The scaling behavior of the string tension, the deconfinement transition temperature, and the O⁺⁺ glueball mass obtained from published data is compared. The results show that there is no asymptotic scaling forK _F=(6/g ²)<6.1. We also estimate the renormalized action generated by the √3 block transformation for use in future calculations.     

Chiral phenomenological relations between rates of rare radiative decays of kaon to pion and leptons and the meson form factors

In the framework of the chiral perturbation theory we obtain the phenomenological relations between decay branches of rare radiative kaon to pion and leptons K ⁺ → π⁺ l ⁺ l ⁻ and K _S ⁰ → π⁰ l ⁺ l ⁻ and meson form factors. The comparison of these results with the present-day experimental data shows us that the ChPT relations for a charge kaon can determine meson form factors from already measured decay rates at high precision level. However, in the case of the neutral kaon decays K ⁰ → π⁰ e ⁺ e ⁻(μ⁺μ⁻) the form factor data are known to a higher precision than data on the differential rates of radiative kaon decay K ⁰ π⁰ e ⁺ e ⁻(μ⁺μ⁻).     

K +→π + vv andK L 0 →μ + μ − decays within the Minimal Supersymmetric Standard Model

We present a detailed calculation of the contributions of charginos, scalar quarks, and charged Higgs boson to theK ⁺→π ⁺ vv andK _L ⁰ →μ ⁺ μ ⁻ decays. We include mixings: that of charginos and that of the scalar partners of the left and right handed top quark. We find that the box contribution to the amplitudes is much smaller than the penguin contribution, which can be ∼10% of the Standard Model contribution, even for relatively large SUSY masses. The charged Higgs contribution can be as large as 25% of the SM contribution in the first decay and as much as 40% of the SM contribution in the second decay.     

New data on the p + N → [Σ0K+] + N reaction at E p= 70 GeV and the search for exotic baryons

New data for the diffractive reaction p+N→ [Σ⁰ K ⁺] +N at E _p= 70 GeV were obtained with partially upgraded SPHINX setup. The data are in a good agreement with the results of our previous study of this reaction. In the mass spectrum M(Σ⁰ K ⁺) a structure at the threshold region with a mass ∼1810 MeV and a distinct X(2000) peak with M= 1989 ± 6 MeV and γ= 91 ± 20 MeV are observed. Unusual features of the massive X(2000) state (narrow decay width, anomalously large branching ratio for the decay channel with strange particle emission) make it a serious candidate for cryptoexotic pentaquark baryon with hidden strangeness |qqqsˉs>. We also present new results on the narrow threshold structure X(1810) with M= 1807 ± 7 MeV and γ= 62 ± 19 MeV which is produced in the region of very small P ² _T < 0.01 GeV². The possibility of the Coulomb production mechanism for X(1810) is discussed. Received: 28 April 1999     

Irreversible quantum mechanics in the neutralK-system

The neutral kaon system is used to test the quantum theory of resonance scattering and decay phenomena. The two dimensional Lee-Oehme-Yang theory with complex Hamiltonian is obtained by truncating the complex basis vector expansion of the exact theory in rigged Hilbert space. This can be done forK ₁ andK ₂ as well as forK _S andK _L , depending upon whether one chooses the (self-adjoint, semibounded) Hamiltonian as commuting or noncommuting withCP. As an unexpected curiosity, one can show that the exact theory (without truncation) predicts long-time 2π decays of the neutral kaon system even if the Hamiltonian conservesCP.     

Characterization of ZnO and Zn0.95Co0.05O prepared by sol-gel method using PAC spectroscopy

We report on the first NMR study of ⁷³Ge nuclear spin decoherence in germanium single crystals with different abundance of the ⁷³Ge isotope. Hahn echo decays are well fit by a superposition of two exponentials. The deviation from the single exponential is more pronounced in the more spin-diluted sample, causing long-lived echoes. We show that the decay of these echoes becomes slower with the reduction of ⁷³Ge abundance and is therefore caused by dipole–dipole interaction, reflecting the fundamental decoherence process in the spin system. The fast decay at the beginning of the relaxation process is shown to be mainly caused by the quadrupole interaction. Our experimental findings are supported by the calculations of Hahn echo decays in the germanium crystals under study. Quite good agreement between the theory and experiment is demonstrated.     

CP non-violation in neutral K-meson decay: A non-standard explanation

A recently presented concept, where, in the framework of parametrized relativistic quantum field theory, antiparticles are described consistently with negative frequencies, but positive energy density, is used to analyse the decay of neutralK-mesons, where the experimental results usually are interpreted as an evidence forCP-violation. In the theory presented the charge conjugation is antilinear, as in original Dirac theory, and theCPT-transformation is unitary. The Hamiltonian is indefinite, and changes sign under theCPT-transformation, since positive and negative eigenvalues are interchanged. As a result the eigenstates of the Hamiltonian are notCPT-eigenstates. The interference of positive and negative frequencies leads to a mixing ofCPT-eigenstates, as is observed in experiment. The study of a simple model system shows that the proposed mechanism of dynamical mixing offers an explanation for the experiments on theK ⁰– ⁰-meson system, with respect to both the observed mixing of eigenstates and the observed difference in the number of CP-violating events in the decays of the longer and shorter living neutralK-mesonsK _L andK _S . No symmetry violation of the theory needs be assumed.