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

Measurements of Lifetimes and a Limit on the Lifetime Difference in the Neutral D-Meson System

Using the large hadroproduced charm sample collected in experiment E791 at Fermilab, we report the first directly measured constraint on the decay-width difference Delta Gamma for the mass eigenstates of the D0-D0bar system. We obtain our result from lifetime measurements of the decays D0 --> K-pi+ and D0 --> K-K+, under the assumption of CP invariance, which implies that the CP eigenstates and the mass eigenstates are the same. The lifetime of D0 --> K-K+ (the CP-even final state is \tau_KK = 0.410 +/- 0.011 +/- 0.006 ps, and the lifetime of D0 --> K-pi+ (an equal mixture of CP-odd and CP-even final states is tau_Kpi = 0.413 +/- 0.003 +/- 0.004 ps. The decay-width difference is Delta Gamma = 2(Gamma_KK - Gamma_Kpi) = 0.04 +/- 0.14 +/- 0.05 ps^-1. We relate these measurements to measurements of mixing in the neutral D-meson system.Comment: 8 pages + 3 figures + 2 table

Color Transparency via Coherent Exclusive rho Production

We examine the potential of the COMPASS experiment at CERN to study color transparency via exclusive coherent vector meson production in hard muon-nucleus scattering. It is demonstrated that COMPASS has high sensitivity to test this important prediction of perturbative QCD.Comment: Feasibility study for COMPASS collaboration, 3 pages, no figures, 1 table. This contribution is based on talk presented at the Workshop on Spin Physics, Trento, Italy, July 2001. The conference www site is http://ECTstar.ect.it/contents.html The proceedings of the workshop will be published as a special issue of Nuclear Physics B (proc suppl), eds. S Bass, A De Roeck and A Deshpande. A more complete 26 page feasibility study with 7 figures and 3 tables is available as A. Sandacz et al., hep-ex/0106076 Revision of 26 Sept. for Ref. 11 modificatio

The Leading Particle Effect from Heavy-Quark Recombination

The leading particle effect in charm hadroproduction is an enhancement of the cross section for a charmed hadron D in the forward direction of the beam when the beam hadron has a valence parton in common with the D. The large D+/D- asymmetry observed by the E791 experiment is an example of this phenomenon. We show that the heavy-quark recombination mechanism provides an economical explanation for this effect. In particular, the D+/D- asymmetry can be fit reasonably well using a single parameter whose value is consistent with a recent determination from charm photoproduction.Comment: Revtex file, 4 pages, 3 figure

Phase Motion in the Scalar Low-Mass pi+pi- Amplitude in D+ -> pi-pi+pi+ Decay

Applying the Amplitude Difference method to Fermilab experiment E791 D+ -> pi-pi+pi+ data, we measure the low mass pi+pi- phase motion. Our results suggest a significant phase variation, compatible with the existence of an isoscalar sigma(500) meson, as previously reported using an isobar model fit to the full Dalitz-plot density.Comment: 12 pages, 8 figures Accepted for publication at PL

Coulomb induced diffraction of energetic hadrons into jets

The electromagnetic (e.m.) current conservation and renormalizability of QCD are used to calculate the amplitude of energetic hadron(photon) diffraction into several jets with large relative transverse momenta off the nucleon(nucleus) Coulomb field. Numerical estimates of the ratio of e.m. and strong amplitudes show that within the kinematic range where the leading twist approximation for the strong amplitude is applicable, the e.m. contribution can be neglected. In pA scattering at LHC and in the fragmentation of a photon into two jets in ultraperipheral AA collisions in the black limit (which maybe realistic at LHC) e.m. contribution may win.Comment: 10 page