Final State Interactions Of Pions Research Articles

Chiral nonet mixing inη′→ηππdecay

Underlying mixing of scalar mesons is studied in $\eta'\rightarrow \eta\pi\pi$ decay within a generalized linear sigma model of low-energy QCD which contains two nonets of scalar mesons and two nonets of pseudoscalar mesons (a quark-antiquark nonet and a four quark nonet). The model has been previously employed in various investigations of the underlying mixings among scalar mesons below and above 1 GeV (as well as those of their pseudoscalar chiral partners) and has provided a coherent global picture for the physical properties and quark substructure of these states. It is found that the linear sigma model with only a single lowest-lying nonet is not accurate in predicting the decay width, but inclusion of the mixing of this nonet with the next-to-lowest lying nonet, together with the effect of final state interaction of pions, significantly improves this prediction and agrees with experiment up to about 1\%. It is also shown that while the prediction of the leading order of the generalized model for the Dalitz parameters is not close to the experiment, the model is able to give a reasonable prediction of the energy dependencies of the normalized decay amplitude squared and that this is expected to improve with further refinement of the complicated underlying mixings. Overall this investigation provides further support for the global picture of scalar mesons: those below 1 GeV are predominantly four-quark states and significantly mix with those above 1 GeV which are closer to the conventional p-wave quark-antiquark states.

Isospin symmetry violating effects and scattering length extraction from kaon decays

The isospin symmetry breaking effects in the charged kaons decays to two or three pions are considered. In semileptonic decay K ± → π + π −e± ν (called K e4) these effects turn out to be crucial for correct extraction of ππ scattering lengths. Taking in account electromagnetic interaction between the pions in the final state and isospin symmetry breaking due to different masses of charged and neutral pions allows to adjust the values of scattering lengths obtained from experimental data on K e4 decay and predictions of Chiral Perturbation Theory (ChPT). Final state interactions of pions in the decay K ± → π ± π 0 π 0 leading to the anomaly (cusp) in the π 0 π 0 invariant mass distribution in the vicinity of charged pions’ threshold are discussed and recent results of accounting of the electromagnetic interaction among charged pions leading to π + π − bound states (pioniumatom) just under the charged pions’ threshold are presented.

The electromagnetic effects in K e4 decay

The final-state interaction of pions in K e4 decay allows to obtain the value of the isospin and angular-momentum-zero ππ scattering length a 00 .We take into account the electromagnetic interaction of pions and isospin-symmetry-breaking effects caused by different masses of neutral and charged pions and estimate the impact of these effects on the procedure of scattering-length extraction from K e4 decays.

Radiative corrections in K e4 decay

The final state interaction of pions in the decay K±→π+π−e±ν allows one to obtain the value of the isospin and angular momentum zero pion–pion scattering length a00. To extract this quantity from experimental data the radiative corrections (RC) have to be taken into account. Based on the lowest order results and the factorization hypothesis, we get the expressions for RC in the leading and next-to leading logarithmical approximation. It is shown that the decay width dependence on the lepton mass me through the parameter \(\sigma=\frac{\alpha}{2\pi}(\ln\frac{M^{2}}{m_{e}^{2}}-1)\) has the standard form of the Drell–Yan process and is proportional to the Sommerfeld–Sakharov factor. The numerical estimations are presented.

Charged current antineutrino reactions fromC12at MiniBooNE energies

A study of charged current induced antineutrino interactions from nuclei has been done for the intermediate energy antineutrinos and applied to {sup 12}C, relevant for ongoing experiment by MiniBooNE collaboration. The calculations have been done for the quasielastic and inelastic lepton production as well as for the incoherent and the coherent pion production processes. The calculations are done in local density approximation. In the case of the quasielastic reaction the effects of Pauli blocking, Fermi motion effects, renormalization of weak transition strengths in nuclear medium and the Coulomb distortion of the outgoing lepton have been taken into account. For the inelastic processes the calculations have been done in the {delta} dominance model and take into account the effect of Pauli blocking, Fermi motion of the nucleon, and renormalization of {delta} properties in a nuclear medium. The effect of final state interactions of pions is also taken into account. The numerical results for the total cross sections for the charged current quasielastic scattering and incoherent pion production processes are compared with earlier experimental results available in freon and freon-propane. It is found that nuclear medium effects give strong reduction in the cross sections leading to satisfactory agreement with the available data.

Electromagnetic corrections to final state interactions in [formula omitted] decays

The final state interactions of pions in decays K ± → π ± π 0 π 0 are considered using the methods of quantum mechanics. We show how to incorporate the electromagnetic effects in the amplitudes of these decays and to work out the relevant expressions valid above and below the two charged pions production threshold M c = 2 m . The electromagnetic corrections are given as evaluated in a potential model.

Neutrino induced charged current1π+production at intermediate energies

The charged current one pion production induced by ${\ensuremath{\nu}}_{\ensuremath{\mu}}$ from nucleons and nuclei like $^{12}\mathrm{C}$ and $^{16}\mathrm{O}$ nuclei has been studied. The calculations have been done for the incoherent and the coherent processes from nuclear targets assuming the $\ensuremath{\Delta}$ dominance model and taking into account the effect of Pauli blocking, Fermi motion of the nucleon, and renormalization of $\ensuremath{\Delta}$ properties in a nuclear medium. The effect of final state interactions of pions has been taken into account. The theoretical uncertainty in the total cross sections due to various parametrizations of the weak transition form factors used in literature has been studied. The numerical results for the total cross sections are compared with the recent preliminary results from the MiniBooNE collaboration on $^{12}\mathrm{C}$ and could be useful in analyzing future data from the K2K collaboration.

Nuclear cross sections in 16O for β beam neutrinos at intermediate energies

Abstract The nuclear cross sections for charged lepton production induced by β beam neutrinos (antineutrinos) in 16O have been presented at intermediate energies corresponding to the Lorentz boost factor γ 250 ( 150 ) . The calculations for quasielastic lepton production includes the effect of Pauli blocking, Fermi motion and renormalization of weak transition strengths in the nuclear medium. The calculations for the inelastic lepton production is done in the Δ dominance model. The renormalization of Δ properties in a nuclear medium and final state interactions of pions with the final nucleus are taken into account. The results may be useful in performing feasibility studies for the future CERN-FREJUS base line neutrino oscillation experiments.

ϱ-meson production and decay in proton-nucleus collision

We analyze the production of ϱ-mesons in p + A reactions including both the production by proton-nucleon as well as pion-nucleon collisions within a coupled channel transport approach. The final state interactions of the ϱ-meson with nucleons are evaluated from a resonance model which allows to extract elastic and inelastic cross sections. We include the latter final state interactions, the ϱ-meson decay into two pions as well as the final pion-nucleon interactions within the transport approach. We find the invariant mass distribution of pion pairs to be sensitive to the ϱ-meson properties in the nuclear medium. However, due to the strong final state interactions of pions only light targets like 12C might be suited to extract a ϱ-signal from the uncorrelated two pion background which carries information about the in-medium properties of the ϱ-meson.