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1.
We report on time-modulated two-body weak decays observed in the orbital electron capture of hydrogen-like 140Pr59+ and 142Pm60+ ions coasting in an ion storage ring. Using non-destructive single ion, time-resolved Schottky mass spectrometry we found that the expected exponential decay is modulated in time with a modulation period of about 7 seconds for both systems. Tentatively this observation is attributed to the coherent superposition of finite mass eigenstates of the electron neutrinos from the weak decay into a two-body final state.  相似文献   

2.
We examine the possible role of electron-capture on the thermally populated first 2+ excited state of 44Ti in hot astrophysical environments pertaining to post explosive nucleosynthesis supernova debris. We find in a simple schematic model that the astrophysical weak interaction rate for electron-capture decay of 44Ti can depend considerably on temperature and hence on time. We propose a time varying decay rate for the evolving supernova debris and demonstrate its consequence for the 44Ti mass yield of the supernova Cas A, observed through the measured 1.157 MeV γ-ray flux from the electron-capture decay of 44Ti.  相似文献   

3.
The properties of the K1 and charged lepton from the charmed particle decay D→K1?ν are used to give some model-independent tests for the presence of a purely vector (c, s) weak current. Present data on the electron energy spectrum may suggest that the (c, s) current is not purely vector. Models for the decay and general analysis techniques are also discussed.  相似文献   

4.
We calculate analytically the weak radiative corrections to the weak neutral current gauge boson-bottom fermion vertex, keeping the mass mt of the internal fermion line for the relevant diagrams. We find, to order α, a hard mass-term dependence mt2/MW2 of the amplitude, for large mt values. Its origin comes from the unphysical charged Higgs coupling to fermions in the renormalizable gauge or, equivalently, from the longitudinal charged gauge boson couplings. The diagonal Z0 decay width to b-quarks decreases, due to these weak radiative corrections, by 0.6%–2.5% when the top mass mt varies from 45 to 200 GeV.  相似文献   

5.
New weak interactions of the b-quark and the τ?-lepton are discussed in a gauge model with exact Cabibbo universality for the light quarks. The model is consistent with all observed neutral current data and leads to new signals in the decay of bb? states to electrons.  相似文献   

6.
戴元本 《物理学报》1961,17(2):89-98
利用色散关系研究了弱电流不守恒情况下的π-→π0+e+ν衰变过程。在对π—π散射相移作了一些假定后,证明了π、π中间态的贡献很小。在N、N中间态项中出现的N、N湮灭矩阵元用Chew-Ball理论及湮灭实验估计,同时出现的核子弱作用形状因子又用色散关系计算,证明了N、N中间态对它的贡献很小,计算了π、π中间态对它的贡献。根据现有N、N湮灭实验估计,π-→π0+e+ν过程的衰变几率<6×10-4-1。  相似文献   

7.
We consider the production and weak decay of a pair of heavy quarks (mesons) ine + e ? experiments and study their effect on the various jet distributions. The relative magnitudes of the two-quark-jet and three-quark-jet final states, in the decay of a heavy quark are estimated in the framework of an SU(2) L ×U(1) model. We find that the three quark configuration dominates over the two quark configuration. For the quark jets resulting from the weak decay of the heavy quarks, we calculate the jet distributions in Sphericity, Spherocity and Thrust for the process \(e^ + e^ - \to Q\bar Q \to 6\) quarks. These distributions are compared with the corresponding quantities from the non-perturbative process \(e^ + e^ - \to q\bar q\) and the QCD process \(e^ + e^ - \to q\bar qg\) . We find that the weak decay of heavy quarks is the dominant mechanism for jet broadening ine + e ? experiments, in the intermediate energy region relevant for PETRA and PEP.  相似文献   

8.
《Nuclear Physics A》1998,628(3):417-426
We re-examine the puzzling π+ emission from the weak decay of Λ4He and propose an explanation in terms of a three-body decay of the virtual Σ+. Such a resolution of the π+ decay puzzle is consistent with the calculated Σ+ probability in light Λ hypernuclei as well as the experimentally observed π+ energy spectrum and s-wave angular distribution.  相似文献   

9.
Since one photon exchange is completely forbidden in processes of the type ?0? → ?0+ (? is a charged lepton) or any crossed version of such a process, weak neutral current effects are considerably enhanced. It is shown that 0&#x0304;?0+ nuclear isomers, if they exist, will accordingly exhibit strikingly large neutral current effects. In particular, the monoenergetic conversion electrons will have helicities h of the order of 25% which should be easily measurable. In certain favourable cases, the nuclear weak current matrix elements may be measured experimentally via the analogue β decay or electron capture so that measuring h will constitute a measurement of the electron's neutral vector current coupling constant. In any event, detection of h would prove the existence of an as yet unseen class of neutral currents.  相似文献   

10.
11.
We point out that, given the current experimental status of radiative kaon decays, a subclass of the \(\mathcal{O} (p^4)\) counterterms of the weak chiral lagrangian can be determined in closed form. This involves in a decisive way the decay \(K^\pm \rightarrow \pi ^\pm \pi ^0 l^+ l^-\), currently being measured at CERN by the NA48/2 and NA62 collaborations. We show that consistency with other radiative kaon decay measurements leads to a rather clean prediction for the \(\mathcal{{O}}(p^4)\) weak couplings entering this decay mode. This results in a characteristic pattern for the interference Dalitz plot, susceptible to be tested already with the limited statistics available at NA48/2. We also provide the first analysis of \(K_S\rightarrow \pi ^+\pi ^-\gamma ^*\), which will be measured by LHCb and will help reduce (together with the related \(K_L\) decay) the experimental uncertainty on the radiative weak chiral couplings. A precise experimental determination of the \(\mathcal{{O}}(p^4)\) weak couplings is important in order to assess the validity of the existing theoretical models in a conclusive way. We briefly comment on the current theoretical situation and discuss the merits of the different theoretical approaches.  相似文献   

12.
Isospin violating signals in the τ? → (3π)?ντ decay mode are discussed. For the τ? → π?π?π+ντ decay mode, isospin violation arises from the vector current contribution in the τ? → ωπ?ντ decay with the subsequent isospin violating ω decay into π+π?. We demonstrate that such effects may be observed in presently available data through the measurement of the interference effects of these vector current contributions with the dominating axial vector current,i. e. through a measurement of the structure functionsW F, WG, WH andW I. In the case of the τ? → π0π0π?ντ decay mode, a vector current contribution is generated by ηπ0 mixing in the decay chain τ? → η??ντ → π0π0π?ντ. We find that this effect is rather small, the magnitude of the associated interference terms being too low for present statistics.  相似文献   

13.
Laser-induced nuclear orientation has been used to make sub-Doppler-resolution measurements of a nuclear isomer85mRb that has a lifetime of only a microsecond. The technique succeeds because the sampled atoms remove themselves before equilibrating. This paper describes two cases in which pre-equilibrium removal of atoms can prevent thermal equilibrium from obscuring information about the weak interaction that is present in the velocity profile of atoms as they recoil following beta decay. It should be possible to measure electron-antineutrino angular correlations in the beta decay of85Kr, and to look for beta decay of tritium into an atomic bound state of3He-a fundamental effect predicted by weak interaction theory but never observed.  相似文献   

14.
We analyze the possibility of experimental investigation of new low-energy relations between the values of resonance masses in the meson form factors and the differential rate of radiative kaon decay K + → π+ e + e +μ) at the current level of the experimental precision. A set of arguments is listed in favor that these relations can be a consequence of weak static interactions in the Standard Model. The results were presented at the 5th NA48 Mini-Workshop on Kaon Physics, CERN, Dec. 12, 2006. The text was submitted by the authors in English.  相似文献   

15.
The possibility of observing Higgs particles through virtual effects is considered in detail for a general gauge theory. The effect of charged Higgs particles on low-energy weak interaction processes, like muon decay, tau decay, nuclear beta decay, pion decay, and some higher-order processes is analyzed. The effect of flavor-changing neutral Higgs particles on rare decay modes of the muon and kaon, μe conversion, Ko-Ko and Do-Do mixing is also studied. We discuss constraints on possible extensions of the Weinberg-Salam model and experiments sensitive to their Higgs particles. In particular, we analyze the neutral Higgs which couple to fermions in the minimal SU(2)L×SU(2)R×U(1) model and find that they probably have mass greater than 100 GeV.  相似文献   

16.
We proveL 2-decay rates of suitable weak solutions to the Navier-Stokes equations in exterior domains. The results for the order of decay are the same as for the solutions to the Cauchy problem of the Navier-Stokes equations. Finally in the case of=R 3 the decay rate order is sharp in the class of solutions considered by us.  相似文献   

17.
18.
We compute the parity conserving and parity violating amplitudes of the weak radiative hyperon decays in a pole model which includes negative parity intermediate states. The matrix elements are determined from experimentally known quantities and also evaluated in a nonrelativistic quark model. We find good numerical agreement with the data for the decay Σ+P+γ and obtain predictions for the other decays where experimental information has been scarce up to now.  相似文献   

19.
We use the method of QCD sum rules to treat the semileptonic weak decay of the D or B meson into a light meson and leptons. To obtain the transition form factors, we adopt the two-point Green’s function in the presence of an external vector or axial-vector field. We find that this method can be related approximately to the traditional three-point Green’s function in the heavy quark limit (m Q → ∞). Unlike some existing QCD sum rule calculations, our results indicate that the form factors have simple dipole or monopole behavior. We obtain results on the various form factors of the semileptonic decay of D and B mesons into a light meson and investigate various decay processes such as B?0 → π + τ _?ν?τ and B?0 → ρ + τν?τ. The method allows us to take into account nonperturbative strong interaction effects, thereby providing a more reliable determination of the Cabibbo-Kobayashi-Maskawa matrix elements from the experimental data.  相似文献   

20.
We have measured the transport critical current densityJ cof sintered YBa2Cu3O7, in various applied fields up to 185 Oe at 77 K. We find a sharp decay ofJ cwith magnetic field. We show that this sharp decay is consistent with the low field hysteresis results of Groveret al. We argue that the observed field dependence is not caused by intragranular weak links.  相似文献   

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