2,423 research outputs found
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
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