CPT-violating effects in muon decay

We consider low-energy CPT-violating modifications in charged current weak interactions and analyze possible ramifications in muon and antimuon decays. We calculate the lifetime of muon and antimuon with these modifications, and from the result, put bounds on the CPT-violating parameters. Moreover, we elaborate on the muon and antimuon decay rate differentials in electron energy and spatial angle, which entail interesting phenomenological consequences presenting new ways to constrain CPT violation in charged lepton decays.     

Oscillation of Dirac and Majorana neutrinos from muon decay in the case of a general interaction

We analyse the possibility of distinguishing Dirac and Majorana neutrinos in future neutrino factory experiments in which neutrinos are produced in muon decay when, in addition to a vector type as in the SM, there are also scalar interactions. We check this possibility in an experiment with a near detector, where the observed neutrinos do not oscillate, and in a far detector, after the neutrino oscillations. Neglecting higher-order corrections, even neutrino observation in the near detector does not give a chance to differentiate their character. However, this possibility appears in the leading-order after the neutrino oscillations observed in far detector.     

Enhanced electroweak radiative corrections in SUSY and precision data

Enhanced radiative corrections generated in SUSY extensions of the Standard Model spoil the fit of the precision data (Z-boson decay parameters and W-boson mass). This negative effect is washed out for heavy enough squarks, because of the decoupling property of SUSY models. We find that even for light squarks the enhanced radiative corrections can be small. In this case substantial mixing is necessary.     

Radiative corrections to muon and beta decay in the intermediate Vector Boson theory

The radiative corrections to muon and beta decay are examined in detail using the ξ-limiting formalism ofLee andYang. The electron spectra for both decays are calculated. It is found that the muon lifetime discrepancy is reduced considerably if one considers, quantitatively, the effect of strong interactions on the weak vector coupling constant as determined from the neutron's lifetime.     

Radiative corrections to muon decay in leading and next-to-leading approximation for electron spectrum

We have noted that the electron spectrum of muon decay in the leading logarithmic approximation calculated in two lowest orders of the perturbation theory in the paper of Berman (1958), can be reproduced by the parton language. This fact permits one to generalize the result to all orders of the perturbation theory using the structure function method.     

Hard meson corrections to the amplitude for radiative muon capture and the elementary particle method

Hard meson corrections to the amplitude of radiative muon capture on the proton are derived within the framework of vector meson dominance in the tree approximation. The weak form factors are mediated by π, ρ and A₁ mesons which may radiate. The model reproduces the terms in the amplitude of lower order in the momentum transfers as derived from low-energy theorems and determines higher-order terms which are otherwise ambiguous or undetermined. Arguments are given why a similar approach to radiative muon capture in nuclei in an elementary particle method is expected to fail.     

Hard meson corrections to the amplitude for radiative muon capture and the elementary particle method

Hard meson corrections to the amplitude of radiative muon capture on the proton are derived within the framework of vector meson dominance in the tree approximation. The weak form factors are mediated by π, ρ and A₁ mesons which may radiate. The model reproduces the terms in the amplitude of lower order in the momentum transfers as derived from low-energy theorems and determines higher-order terms which are otherwise ambiguous or undetermined. Arguments are given why a similar approach to radiative muon capture in nuclei in an elementary particle method is expected to fail.     

New non-abelian couplings and radiative corrections to the main decay of the top quark

We calculate first order radiative corrections to the main decay of the top quark,tb+W, beyond the Standard Model, by grafting onto the standard lagrangian (using the terminology of de Rújula, Gavela, Hernandez and Massó), a new operator, which respects the gauge symmetry of the Standard Model and modifies theZ ⁰ W ⁺ W ^–,W ⁺ W ^– vertices In our renormalization scheme we use ,G _F,M _Z as input parameters. Them _t dependence is given where we use =1 TeV as a possible scale of the new physics. Form _t =150(200) GeV and =1 TeV, the maximal effect due to the new non-abelian couplings, is to change the relative size of the electroweak radiative corrections of the Standard Model by adding a value of –2.98(–6.96)%, i.e. from a value of 5.55(3.26)% to 2.57(–3.7)%.     

Asphericity in the Fermi Surface and Fermi Energy of Na-K, Na-Rb and Na-Cs Binary Alloys

Detailed theoretical investigations into asphericity in the Fermi surface (FS) and Fermi energy (FE) ofNa1_xKx, Na1_xRbx, and Na1_xCsx binary solid solutions are carried out for the first time. The alloying behavior ofthe K, Rb, and Cs with the Na generates the Fermi surface distortion (FSD) of bce simple metals. The FS of Na-K,Na-Rb, and Na-Cs solid solution is a distorted sphere with the largest deviation along [110]. We have found that theimpact of local-field correction function on FSD is maximun at [100] point and minimum at [111] point. The exchangeand correlation effect is found to suppress the value of FE.     

Measurement of and the dipion contribution to the muon anomaly with the KLOE detector

We have measured the cross section σ(e⁺e⁻→π⁺π⁻γ(γ)) at DAΦNE, the Frascati -factory, using events with initial state radiation photons emitted at small angle and inclusive of final state radiation. We present the analysis of a new data set corresponding to an integrated luminosity of 240 pb⁻¹. We have achieved a reduced systematic uncertainty with respect to previously published KLOE results. From the cross section we obtain the pion form factor and the contribution to the muon magnetic anomaly from two-pion states in the mass range 0.592<M_ππ<0.975 GeV. For the latter we find Δ^ππa_μ=(387.2±0.5_stat±2.4_exp±2.3_th)×10⁻¹⁰.     

Hemoglobin magnetism in aqueous solution probed by muon spin relaxation and future applications to brain research

A marked difference in spin relaxation behavior due to hemoglobin magnetism was found for positive muons (μ⁺) in deoxyhemoglobin in comparison with that observed in oxyhemoglobin in aqueous solution at room temperature under zero and external longitudinal magnetic fields upto 0.4 Tesla. At the same time, small but significant unique relaxation pattern was observed in nonmagnetic oxyhemoglobin. Combined with our previous measurements on hemoglobin in human blood, application of this type of measurement to the studies of the level of oxygenation in various regions of the human brain is suggested.     

Weak radiative decay Λ b →Λγ in the heavy quark effective theory

The weak radiative decay Λ _b →Λγ is studied in the heavy quark effective theory treatings-quark as heavy. This rare decay is induced by the short distance electromagnetic penguins. Including corrections of the order of (1/m _Q), we obtain the transition matrix element and the corresponding decay width. The Isgur-Wise function is evaluated in the largeN _c limit and the branching ratio obtained is 1.48×10⁻⁵.     

Phonon contribution to the shear viscosity of a superfluid Fermi gas in the unitarity limit

We present a detailed analysis of the contribution of small-angle Nambu–Goldstone boson (phonon) collisions to the shear viscosity, η$\eta$, in a superfluid atomic Fermi gas close to the unitarity limit. We show that the experimental values of the shear viscosity coefficient to entropy ratio, η/s$\eta /s$, obtained at the lowest reached temperature can be reproduced assuming that phonons give the leading contribution to η$\eta$. The phonon contribution is evaluated considering 1↔2$1\leftrightarrow 2$ processes and taking into account the finite size of the experimental system. In particular, for very low temperatures, T?0.1T_F$T?0.1T_F$, we find that phonons are ballistic and the contribution of phonons to the shear viscosity is determined by the processes that take place at the interface between the superfluid and the normal phase. This result is independent of the detailed form of the phonon dispersion law and leads to two testable predictions: the shear viscosity should correlate with the size of the optical trap and it should decrease with decreasing temperature. For higher temperatures the detailed form of the phonon dispersion law becomes relevant and, within our model, we find that the experimental data for η/s$\eta /s$ can be reproduced assuming that phonons have an anomalous dispersion law.     

Quark mass corrections to the perturbative thrust and its effect on the determination of αs

We consider the effects of quark masses to the perturbative thrust in e ⁺ e ⁻ annihilation. In particular we show that perturbative power corrections resulting from non-zero quark masses considerably alters the size of the non-perturbative power corrections and consequently, significantly changes the fitted value of α_s.     

Quantum corrections to the semiclassical level density of the circular disk in homogeneous magnetic fields

In the semiclassical trace formula for the level density of a circular disk in homogeneous magnetic fields, quantum corrections to the Maslov phase have been shown to be important in strong fields. In this article further quantum corrections are considered, namely, grazing corrections which are relevant for whispering-gallery orbits, and a uniform approximation to the bifurcation points in strong fields is applied. Both corrections are shown to have a surprisingly small effect on the semiclassical level density. Implementing those corrections requires a technique different from the common Gaussian smoothing in the numerical evaluation of the trace formula. The appropriate generalization is presented. 1997 Elsevier Science B.V. All rights reserved.     

On the corrections to scaling in three-dimensional Ising models

The leading correction-to-scaling amplitudes for the spin-1/2, nearest-neighbor sc, bcc, and fee Ising models are considered with the particular aim of determining their signs. On the basis of previous two-variable series analyses by Chen, Fisher, and Nickel and renormalization group=4–d expansions, it is concluded that the correction amplitudes for the susceptibility, correlation length, specific heat, and spontaneous magnetization arenegative for all three lattices. Thus, for example, the effective exponent _eff(T) asymptotically approaches the true susceptibility exponent fromabove. Other earlier and more recent high-temperature series and field-theoretic analyses are seen to be consistent with this result. However, the usual nonasymptotic, perturbative field-theoretic approaches are essentially committed to positive correction amplitudes. The question of the signs therefore relates directly to the applicability of these non-asymptotic field-theoretic calculations to three-dimensional Ising models as well as to different experimental systems.     

Fermi超流气体在unitarity区域和Bose-Einstein凝聚区域的自俘获现象研究米

在平均场理论和两模近似下,通过观察布居数差随时间的演化,以及布居数差的平均随非线性相互作用参数的变化,研究了对称双势阱以及势阱问高频调制时Fermi超流气体在unitarity区域和Bose-Einstein凝聚区域的自俘获现象．给出了出现自俘获现象的边界条件;发现高频调制在一定调制范围内使自俘获现象更容易实现．最后研究了初值对自俘获的影响,发现初值的绝对值︳s（O）︳的增加更有利于自俘获的实现．