Structure for the breathing mode of the nucleon from high energy p-p scattering

Spectra of p-p and pi-p scattering at beam momenta between 6 and 30 GeV/c have been reanalysed. These show strong excitation of N* resonances, the strongest one corresponding to the "scalar" P11 excitation (breathing mode) at m_o= 1400+-10 MeV with Gamma= 200+-25 MeV. The result of a strong scalar excitation is supported by a large longitudinal amplitude S_1/2 extracted from e-p scattering. From exclusive data on p+p=>p p pi+ pi- a large 2pi-N decay branch for the P_11 resonance of B_2pi= 75+-20 % has been extracted. The differential cross sections were described in a double folding approach, assuming multi-gluon exchange as the dominant part of the effective interaction between the constituents of projectile and target. First, the parameters of the interaction were fitted to elastic scattering; then with this interaction the inelastic cross sections were described in the distorted wave Born approximation. A good description of the data requires a surface peaked transition density, quite different from that of a pure radial mode. In contrast, the electron scattering amplitude S_1/2 is quite well described by a breathing mode transition density with radial node. This large difference between charge and matter transition density suggests, that in p-p scattering the coupling to the multi-gluon field is much more important than the coupling to the valence quarks. A multi-gluon (or sea-quark) transition density is derived, which shows also breathing, indicating a rather complex multi-quark structure of N and N* including multi-glue (or q^2n qbar ^-2n) creation out of the g.s. vacuum.Comment: 18 pages with 7 figure

Observation of photon-assisted tunneling in optical lattices

We have observed tunneling suppression and photon-assisted tunneling of Bose-Einstein condensates in an optical lattice subjected to a constant force plus a sinusoidal shaking. For a sufficiently large constant force, the ground energy levels of the lattice are shifted out of resonance and tunneling is suppressed; when the shaking is switched on, the levels are coupled by low-frequency photons and tunneling resumes. Our results agree well with theoretical predictions and demonstrate the usefulness of optical lattices for studying solid-state phenomena.Comment: 5 pages, 3 figure

Excitation and damping of collective modes of a Bose-Einstein condensate in a one-dimensional lattice

The mode structure of a Bose-Einstein condensate non-adiabatically loaded into a one-dimensional optical lattice is studied by analyzing the visibility of the interference pattern as well as the radial profile of the condensate after a time-of-flight. A simple model is proposed that predicts the short-time decrease of the visibility as a function of the condensate parameters. In the radial direction, heavily damped oscillations are observed, as well as an increase in the condensate temperature. These findings are interpreted as a re-thermalization due to dissipation of the initial condensate excitations into high-lying modes.Comment: 5 pages; submitted to PR