Hybrid Meson Production via Pion Scattering from Nuclear Coulomb Field

The CERN COMPASS experiment may use 100-280 GeV pion and Kaon beams and magnetic spectrometers and calorimeters to measure Hybrid (mixed quark-gluon) meson production cross sections in the ultra-peripheral Primakoff scattering of high energy pions and Kaons from virtual photons in the Coulomb field of High-Z targets. There are strong advantages to study Hybrid mesons by the Primakoff reactions pi- gamma --> Hybrid --> rho pi, eta pi, eta' pi, pi b1, pi f1; and similar reactions with a K- beam. Such data should provide significant new input for a more complete understanding of the strong interactions of QCD. A brief description and update of this program is presented

Doubly Charmed Baryons in COMPASS

The search for doubly charmed baryons has been a topic for COMPASS from the beginning. Requiring however a complete spectrometer and highest possible trigger rates this measurement has been postponed. The scenario for such a measurement in the second phase of COMPASS is outlined here. First studies of triggering and simulation of the setup have been performed. New rate estimates based on recent measurements from SELEX at FNAL are presented.Comment: 13 pages, 15 figures, contribution to the Workshop on Future Physics at COMPASS, CERN, Geneva, September 26-27 2002, to appear as CERN Yellow Repor

Doubly heavy hadrons and the domain of validity of doubly heavy diquark--anti-quark symmetry

In the limit of heavy quark masses going to infinity, a symmetry is known to emerge in QCD relating properties of hadrons with two heavy quarks to analogous states with one heavy anti-quark. A key question is whether the charm mass is heavy enough so that this symmetry is manifest in at least an approximate manner. The issue is crucial in attempting to understand the recent reports by the SELEX Collaboration of doubly charmed baryons. We argue on very general grounds that the charm quark mass is substantially too light for the symmetry to emerge automatically via colour coulombic interactions. However, the symmetry could emerge approximately depending on the dynamical details.Comment: 9 page

Doubly Heavy Baryons and Quark-Diquark Symmetry in Quenched and Partially Quenched Chiral Perturbation Theory

We extend the chiral Lagrangian with heavy quark-diquark symmetry to quenched and partially quenched theories. These theories are used to derive formulae for the chiral extrapolation of masses and hyperfine splittings of doubly heavy baryons in lattice QCD simulations. A quark-diquark symmetry prediction for the hyperfine splittings of heavy mesons and doubly heavy baryons is rather insensitive to chiral corrections in both quenched and partially quenched QCD. Extrapolation formulae for the doubly heavy baryon electromagnetic transition moments are also determined for the partially quenched theory.Comment: 19pp, Ref. adde

Radiative Corrections to High Energy Lepton Bremsstrahlung on Heavy Nuclei

One-loop radiative corrections to the leptonic tensor in high energy bremsstrahlung on heavy nuclei are calculated. Virtual and real photon radiation is taken into account. Double bremsstrahlung is simulated by means of Monte Carlo. Numerical results are presented for the case of muon bremsstrahlung in conditions of the COMPASS experiment at CERN.Comment: 7 pages, 1 figur

Heavy Baryons in a Quark Model

A quark model is applied to the spectrum of baryons containing heavy quarks. The model gives masses for the known heavy baryons that are in agreement with experiment, but for the doubly-charmed baryon Cascade_{cc}, the model prediction is too heavy. Mixing between the Cascade_Q and Cascade_Q^\prime states is examined and is found to be small for the lowest lying states. In contrast with this, mixing between the Cascade_{bc} and Cascade_{bc}^\prime states is found to be large, and the implication of this mixing for properties of these states is briefly discussed. We also examine heavy-quark spin-symmetry multiplets, and find that many states in the model can be placed in such multiplets. We compare our predictions with those of a number of other authors.Comment: Version published in International Journal of Modern Physics

Chiral Lagrangian with Heavy Quark-Diquark Symmetry

We construct a chiral Lagrangian for doubly heavy baryons and heavy mesons that is invariant under heavy quark-diquark symmetry at leading order and includes the leading O(1/m_Q) symmetry violating operators. The theory is used to predict the electromagnetic decay width of the J=3/2 member of the ground state doubly heavy baryon doublet. Numerical estimates are provided for doubly charm baryons. We also calculate chiral corrections to doubly heavy baryon masses and strong decay widths of low lying excited doubly heavy baryons.Comment: 20 pages, no figure

Relativistic quark model and pentaquark spectroscopy

The relativistic five-quark equations are found in the framework of the dispersion relation technique. The solutions of these equations using the method based on the extraction of leading singularities of the amplitudes are obtained. The five-quark amplitudes for the low-lying pentaquarks are calculated under the condition that flavor SU(3) symmetry holds. The poles of five-quark amplitudes determine the masses of the lowest pentaquarks. The mass spectra of pentaquarks which contain only light quarks are calculated. The calculation of pentaquark amplitudes estimates the contributions of three subamplitudes. The main contributions to the pentaquark amplitude are determined by the subamplitudes, which include the meson states.Comment: 22 pages, pd