نتایج جستجو برای: ππ electron
تعداد نتایج: 309859 فیلتر نتایج به سال:
Recent data from Belle show unusually large partial widths Υ(5S) → Υ(1S)ππ and Υ(5S) → Υ(2S)ππ. The Z(4430) narrow resonance also reported by Belle in ψπ spectrum has the properties expected of a c̄cud̄ charged isovector tetraquark T c̄c . The analogous state T b̄b in the bottom sector might mediate anomalously large cascade decays in the Upsilon system, Υ(mS) → T b̄b π → Υ(nS)ππ, with a tetraquark-...
Using 58 million J/ψ events taken with the BESII detector, a search for ηc CP violating decays into ππ and KK̄ has been performed. No clear ηc signal is observed, and upper limits for B(ηc → ππ) and B(ηc → KK̄) are given at the 90% confidence level, B(J/ψ → γηc) · B(ηc → π π) < 1.1 × 10, B(J/ψ → γηc) · B(ηc → π π) < 0.71 × 10, B(J/ψ → γηc) · B(ηc → K K) < 0.96 × 10 and B(J/ψ → γηc) ·B(ηc → K 0 SK...
The influence of strong and electroweak penguin amplitudes in B/B̄ → ππ is investigated in connection with the determination of the unitarity triangle angle α of the CKM matrix. A relation between the observable asymmetry, the angle α, and the penguin amplitude is established. A model calculation of the penguin amplitude shows that the CP asymmetry in B → ππ decays is only mildly influenced by t...
We have measured ππ and KK production in two-photon collisions using 87.7 fb of data collected with the Belle detector at the asymmetric energy ee collider KEKB. The cross sections are measured to high precision in the two-photon center-of-mass energy (W ) range between 2.4GeV < W < 4.1GeV and angular region |cos θ∗| < 0.6. The cross section ratio σ(γγ → KK)/σ(γγ → ππ) is measured to be 0.89 ± ...
We present fixed-t subtracted dispersion relations for Compton scattering off the nucleon at energies E γ ≤ 500 MeV, as a formalism to extract the nucleon polarizabilities with a minimum of model dependence. The subtracted dispersion integrals are mainly saturated by πN intermediate states in the s-channel γN → πN → γN and ππ intermediate states in the t-channel γγ → ππ → N ¯ N. For the subproc...
The relationship between the pionium lifetime and the ππ scattering lengths is established, including the sizable electromagnetic corrections. The bound state formalism that is used is that of constraint theory which provides a covariant three-dimensional reduction of the Bethe–Salpeter equation. The framework of generalized chiral perturbation theory allows then an analysis of the lifetime val...
We report on recent progress in studying two aspects of B physics, in which penguin amplitudes play an important role: 1. Bounds on penguin pollution in B(t) → ππ constraining CKM parameters, and a lower bound on B → ππ improving precision in sin 2α. 2. A suggestion for measuring the photon polarization in electroweak penguin decay, B → K1(1400)γ, providing a precision test of the Standard Model.
We present a calculation of the low energy constants describing the real and imaginary parts of the K → ππ decay amplitudes A0 and A2. Leading and next leading order chiral perturbation theory is used and its applicability assessed. A combination of statistical and systematic errors limits the precision of the results. The apparent limitations of chiral perturbation theory raise doubts about th...
The results of analyses obtained in Part I are examined from the viewpoint of chiral symmetry. The mass spectra of ππ system are widely believed to be suppressed generally near the threshold, because of the derivative coupling property of Nambu-Goldstone π meson. However, this suppression does not hold in the processes with large energy release, and the steep increase from the ππ threshold obse...
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