نتایج جستجو برای: ππ interactions
تعداد نتایج: 389020 فیلتر نتایج به سال:
We explore the decay of a vector meson to two pseudoscalar mesons on the lattice with N f = 2 flavours of sea quark. Although we are working with quark masses that do not allow a physical decay, we show how the transition rate can be evaluated from the amplitude for ρ → ππ and from the annihilation component of ππ → ππ. We explore the decay amplitude for two different pion momenta and find cons...
I calculate the leading logarithmic contributions up to two-loop order of the octet part of the K0 → ππ amplitude. This sector of the weak chiral Lagrangian is believed to be the main source of the enhancement of the I = 0 relative to the I = 2 K0 → ππ amplitude, the so-called ∆I = 1/2 rule. I discuss the procedure of chiral extrapolations of lattice data specific to K → ππ decays and study the...
The phases of terms of amplitude that arise from the ππ interaction are obtained by using a simple realistic model of ππ interaction via virtual ρ-meson, instead of the ChPT. It is shown that the standard ChPT approach cannot reproduce the contribution of the ρ-meson to the ππ interaction. It is shown that the interference between the terms of amplitude with different CP-parity appears only whe...
Using data collected by the high energy photoproduction experiment FOCUS at Fermilab we study the doubly and singly Cabibbo suppressed decays D and D s → K ππ. Our measurements of Γ(D → Kππ)/Γ(D → Kππ) = 0.0065 ± 0.0008 ± 0.0004 and Γ(D s → K ππ)/ Γ(D s → K Kπ) = 0.127 ± 0.007± 0.014 are based on samples of 189± 24 D and 567± 31 D s reconstructed events, respectively. We also present Dalitz plo...
The reversal of aromaticity and antiaromaticity upon excitation to the lowest ππ* state impacts on photophysics photoreactivity various annulenes. This unifying principle can guide rationalization a plethora excited-state reactions has strong predictive power in design new photochemical transformations. For more details, see Review by H. Ottosson et al. (DOI: 10.1002/chem.202203748)
Four of the six parameters defining the two-loop ππ scattering amplitude have been determined using Roy dispersion relations. Combining this information with the Standard χPT expressions, we obtain the threshold parameters, low-energy phases and the O(p) constants l 1, l r 2. The result l r 2(Mρ) = (1.6 ± 0.4 ± 0.9) × 10 −3 (l̄2 = 4.17 ± 0.19 ± 0.43) reproduces the correct D-waves but it is inco...
A joint analysis of the ππ and ππ S-wave amplitudes including results of three experiments has been performed. Using our theoretical model of the ππ production in which not only the pion exchange but also the a1 meson exchange were taken into account we have obtained a unique solution (called ”down-flat”) for the scalar-isoscalar phase shifts. Thus a long-standing problem of ambiguities in the ...
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