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Register a new userLight Meson Physics from Charm Decays at Fermilab E791
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Carla Gobel
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We present recent results on light mesons based on Dalitz plot analyses of charm decays from Fermilab experiment E791. Scalar mesons are found to have large contributions to the decays studied, $D^+to K^-pi^+pi^+$ and $D^+, D_s^+topi^-pi^+pi^+$. From the $Kpipi$ final state, we find good evidence for the existence of the light and broad $kappa$ meson and we measure its mass and width. We also discuss recently published results on the 3$pi$ final states, especially the measurement of the $f_0$ parameters and the evidence for the $sigma$ meson from $D^+tosigmapi^+$. These results demonstrate the importance of charm decays as a new environment for the study of light meson physics.
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We will discuss how the decays of charm mesons can be used to study light mesons spectroscopy, by presenting recent results of Dalitz plot analyses using data from Fermilab experiment E791. Emphasis will be on scalar mesons, which are found to have large contribution to the $D$ decays studied. In addition to the usual extraction of decay fractions and relative phases of the intermediate amplitudes, the Dalitz plot technique is used to measure masses and widths of scalar resonances. From the $D_s$ decay, we obtain masses and widths of $f_0(980)$ and $f_0(1370)$. We find evidence for a light and broad scalar resonance, the $sigma$ meson, in $D^+topi^-pi^+pi^+$ decay. Preliminary studies also show evidence for a light and broad resonance, the $kappa$ meson, in $D^+to K^-pi^+pi^+$ decay. These results illustrate the potential of charm decays as a laboratory for the study of light mesons.
A new approach to the analysis of three body decays is presented. Model-independent results are obtained for the swave $Kpi$ amplitude as a function of $Kpi$ invariant mass. These are compared with results from $Kmpip$ elastic scattering, and the prediction of the Watson theorem, that the phase behavour be the same below $Keta^{prime}$ threshold, is tested. Contributions from $I=half$ and $I={3over 2}$ are not resolved in this study. If $I=half$ dominates, however, the Watson theorem does not describe these data well.}
Results are presented for the 500 GeV/c pion production asymmetry and polarization of the Lambda_c (anti-Lanbda_c) charmed baryon from Fermilab experiment E791. An analysis of the decay to the p anti-K pi final state is described. Resonant sub-channel fractions and phases are given and possible resonant effects in the low mass p anti-K system discussed. Significant decay to Lambda_c --> Delta++ K- establishes for the first time the importance of a W exchange mechanism in charmed baryon decay.
The $bar PANDA$ experiment at FAIR (Facility for Antiproton and Ion Research) in Darmstadt (Germany) is designed for $bar p p$ annihilation studies and it will investigate fundamental questions of hadron and nuclear physics in interactions of antiprotons with nucleons and nuclei. Gluonic excitations and the physics of hadrons with strange and charm quarks will be accessible with unprecedented accuracy, thereby allowing high precision tests of the strong interactions. In particular, the $D_{s0}^*(2317)^+$ and $D_{s1}(2460)^+$ are still of high interest 11 years after their discovery, because they can not be simply understood in term of potential models. The available statistics and resolution of the past experiments did not allow to clarify their nature. Recently LHCb at CERN has made progresses in this respect, but still not at the level of precision required in order to clarify the puzzle of the $cs$-spectrum. $bar PANDA$ will be able to achieve a factor 20 higher mass resolution than attained at the B-factories, which is expected to be decisive on these and second-order open questions. The technique to evaluate the width from the excitation function of the cross section of the $D_s$ mesons will be presented, and ongoing simulations performed with $PandaRoot$ will be shown.
An overview of the most important progresses in charm physics since the last CKM Workshop (2014) is presented. Due emphasis is given to the experimental measurements directly related to the CKM matrix.
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