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

Full counting statistics and phase diagram of a dissipative Rydberg gas

Ultra-cold gases excited to strongly interacting Rydberg states are a promising system for quantum simulations of many-body systems. For off-resonant excitation of such systems in the dissipative regime, highly correlated many-body states exhibiting, among other characteristics, intermittency and multi-modal counting distributions are expected to be created. So far, experiments with Rydberg atoms have been carried out in the resonant, non-dissipative regime. Here we realize a dissipative gas of rubidium Rydberg atoms and measure its full counting statistics for both resonant and off-resonant excitation. We find strongly bimodal counting distributions in the off-resonant regime that are compatible with intermittency due to the coexistence of dynamical phases. Moreover, we measure the phase diagram of the system and find good agreement with recent theoretical predictions. Our results pave the way towards detailed studies of many-body effects in Rydberg gases.Comment: 12 pages, 5 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

Phase-matched four wave mixing and quantum beam splitting of matter waves in a periodic potential

We show that the dispersion properties imposed by an external periodic potential ensure both energy and quasi-momentum conservation such that correlated pairs of atoms can be generated by four wave mixing from a Bose-Einstein condensate moving in an optical lattice potential. In our numerical solution of the Gross-Pitaevskii equation, a condensate with initial quasi-momentum k_0 is transferred almost completely (>95%) into a pair of correlated atomic components with quasi-momenta k_1 and k_2, if the system is seeded with a smaller number of atoms with the appropriate quasi-momentum k_1.Comment: 4 pages, 4 figures, version accepted for publication in Phys. Rev. A, Rapid Communication