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Register a new userCharm Hadronic Decays From FOCUS: Lessons Learnt
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The FOCUS photoproduction experiment took data in the ninenties and produced a wealth of results in charm physics. Some of the studies were seminal for contemporary experiments, and even paved the way for the technology of many charm and beauty analysis tools.
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The INTEGRAL mission provides a large data set for studying the hard X-ray properties of AGN and allows to test the unified scheme for AGN. We present results based on the analysis of 199 AGN. A difference between the Seyfert types is detected in slightly flatter spectra with higher cut-off energies and lower luminosities for the more absorbed/type 2 AGN. When applying a Compton reflection model, the underlying continua (photon index 1.95) appear the same in Seyfert 1 and 2, and the reflection strength is R=1 in both cases, with differences in the inclination angle only. A difference is seen in the sense that Seyfert 1 are on average twice as luminous in hard X-rays than the Seyfert 2 galaxies. The unified model for Seyfert galaxies seems to hold, showing in hard X-rays that the central engine is the same in Seyfert 1 and 2 galaxies, seen under different inclination angle and absorption. Based on our knowledge of AGN from INTEGRAL data, we briefly outline open questions and investigations to answer them. In this context an ultra-deep (>= 12 Ms) extragalactic field can be a true legacy of the INTEGRAL mission in the area of AGN studies.
We give arguments in favor of the compatibility with standard physics of some large nonleptonic branching fractions in Cabibbo--forbidden $D^+$ decays, contrary to a recent claim in the literature.
We discuss a search for CPT violation in neutral charm meson oscillations. The data come from the Fermilab fixed-target experiment FOCUS. While flavor mixing in the charm sector is predicted to be small by the standard model, it is still possible to investigate CPT violation through study of the proper time dependence of the asymmetry in right-sign decay rates for D0 and D0-bar. Using present limits for D0-D0-bar mixing we infer bounds on charm CPT violation using data from FOCUS.
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.
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.
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