Complex amplitude phase motion in Dalitz plot heavy meson three body decay

We propose a method to determine the phase motion of a complex amplitude in three body heavy meson decays. We show that the phase variation of a complex amplitude can be directly revealed through the interference observed in the Dalitz Plot region where it crosses with a well established resonant state. This method could be applied to the decays \d3pi and $D^+\to K^-\pi^+\pi^+$, to determine whether the low mass states $\sigma$ and $\kappa$, suggested by E791, have phase motions compatible with resonances.Comment: To appear in Physics Letters

Lessons from CLEO and FOCUS Measurements of D0-anti-D0 Mixing Parameters

If the true values of the D0-anti-D0 mixing parameters lie within the one sigma ranges of recent measurements, then there is strong evidence for a large width difference, y > 0.01, and large SU(3) breaking effects in strong phases, \delta > pi/4. These constraints are model independent, and would become stronger if M_{12}/Gamma_{12} << 1 in the D0-anti-D0 system. The interesting fact that the FOCUS result cannot be explained by a large mass difference is not trivial and depends on the small D0-anti-D0 production asymmetry in FOCUS and the bounds on CP violating effects from CLEO. The large value of \delta might help explain why y ~ sin^2(theta_c).Comment: 15 pages, harvma

Light quark and charm interplay in the Dalitz-plot analysis of hadronic decays in FOCUS

The potentiality of interpreting the D-meson decay-dynamics has revealed itself to be strongly dependent on our understanding of the light-meson sector. The statistics collected by FOCUS is already at a level that manifests parametrization problems for scalar particles. In this paper the first application of the K-matrix approach in the charm sector is illustrated and preliminary results on the D+ and Ds decays to three pions are shown.Comment: 9 pages, 7 figures, Invited talk at the Scalar Meson Worksho

On the scalar nonet lowest in mass

The hypothesis that there exists a nonet of scalars mainly composed of a valence quark-antiquark pair and mixed according to near singlet-octet separation : f_0 (980) singlet, a_0^{+,0,-} (980), K^{* +,0}_0 (1430), \bar K^{* -,0}_0 (1430), f_0 (1500) octet, is put to further tests from the three body decays D^{\pm}, D_{s}^{\pm} -> PS^{\pm} pi^+ pi^- with PS^{\pm} = pi^{\pm}, K^{\pm}. The analysis of decay phases supports the singlet nature of f_0 (980).Comment: Talk (by P.M.) given at the QCD 02 9th International High-Energy Physics Conference in QuantumChromoDynamics (Montpellier 2-9th July 2002), 4 page

Dalitz plot analysis and branching fraction measurement of D+ and Ds+ -> pi+pi-pi+

Fermilab fixed target experiment E791 obtained a sample of $1172 \pm 61$ events of $D^+ \to \pi^- \pi^+ \pi^+$ and 848 $\pm 44$ events of $D_s^+ \to \pi^- \pi^+ \pi^+$ decays. We find respectively $B (D^+ \to \pi^- \pi^+ \pi^+) / B (D^+ \to K^- \pi^+ \pi^+) = 0.0311 \pm 0.0018 ^ {+0.0016}_{-0.0026}$ and $B(D_s^+ \to \pi^+ \pi^- \pi^+) / B(D_s^+ \to \phi \pi^+) = 0.245 \pm 0.028^{+0.019}_{-0.012}$. Using a coherent amplitude analysis to fit the Dalitz plot of the $D^+ \to \pi^- \pi^+ \pi^+$ decay, we find strong evidence for a scalar resonance of mass $478^{+24}_{-23} \pm 17$MeV/$c^2$ and width $324^{+42}_{-40} \pm 21$ MeV/$c^2$, compatible with what is expected for the isoscalar meson $\sigma$ >. The $D^+ \to \sigma(500) \pi^+$ fraction accounts for approximately half of all three-charged-pion decays of the $D^+$ . From the Dalitz plot analysis of the $D_s^+ \to \pi^- \pi^+ \pi^+$ decay events, we find significant contributions from the channels $\rho^0(770)\pi^+$, $\rho^0(1450)\pi^+$, $f_0(980)\pi^+$, $f_2(1270)\pi^+$, and $f_0(1370)\pi^+$. We also present new measurement of the masses and widths of the isoscalar resonances $f_0(980)$ and $f_0(1370)$.Comment: 4 pages, 4 figures, talk presented in BEACH2000, Valencia, Spai

A chiral qbarqbarqq nonet?

We point out that meson spectrum indicates the existence of a degenerate chiral nonet in the energy region around 1.4 GeV with a slightly inverted spectrum with respect to a qq nonet. Based on this observation, the approximately linear rising of the mass of a hadron with the number of constituent quarks, and the existence of a cuasidegenerate pseudoscalar nonet, we conjecture the existence of a tetraquark chiral nonet in this energy region with chiral symmetry implemented directly. We realize this idea in a chiral model and take into account the mixing of the tetraquark chiral nonet with a conventional qq nonet. We find that the mass spectrum of mesons below 1.5 GeV is consistent with this picture. In general, pseudoscalar states arise as mainly qq states but scalar states turn out to be strong admixtures of qq and tetraquark states.Comment: 8 pages, 3 figure

Theoretical Summary of the HADRON99 conference

The Constituent Quark Model has provided a remarkable description of the experimentally observed hadron spectrum but still has no firm theoretical basis. Attempts to provide a QCD justification discussed at Hadron99 include QCD Sum Rules, instantons, relativistic potential models and the lattice. Phenomenological analyses to clarify outstanding problems like the nature of the scalar and pseudoscalar mesons and the low branching ratio for $\psi' \to \rho-\pi$ were presented. New experimental puzzles include the observation of $\bar p p \to \phi \pi$.Comment: 10 pages, espcrc1.st

Structure of Light Scalar Mesons from D_s and D^0 Non-Leptonic Decays

Non-leptonic D meson decays may provide a reliable testbed for the multiquark interpretation of light scalar mesons. In this letter we consider D_s decay and show that a 4-quark f_0(980) meson could induce a decay pattern, which is forbidden for a q-qbar constituent structure. Experimental tests to probe such possibilities are within reach in the near future.Comment: 11 pages, 3 figures, minor changes. To appear in Phys. Lett.