561 research outputs found
The helium trimer with soft-core potentials
The helium trimer is studied using two- and three-body soft-core potentials.
Realistic helium-helium potentials present an extremely strong short-range
repulsion and support a single, very shallow, bound state. The description of
systems with more than two helium atoms is difficult due to the very large
cancellation between kinetic and potential energy. We analyze the possibility
of describing the three helium system in the ultracold regime using a gaussian
representation of a widely used realistic potential, the LM2M2 interaction.
However, in order to describe correctly the trimer ground state a three-body
force has to be added to the gaussian interaction. With this potential model
the two bound states of the trimer and the low energy scattering helium-dimer
phase shifts obtained with the LM2M2 potential are well reproduced.Comment: 15 pages, 3 figures, submitted to Few-Body System
Temporal patterns in the occurrence of selected tropical fishes in mangrove creeks: implications for the fisheries management in north Brazil
Planning the Future of U.S. Particle Physics (Snowmass 2013): Chapter 6: Accelerator Capabilities
These reports present the results of the 2013 Community Summer Study of the
APS Division of Particles and Fields ("Snowmass 2013") on the future program of
particle physics in the U.S. Chapter 6, on Accelerator Capabilities, discusses
the future progress of accelerator technology, including issues for high-energy
hadron and lepton colliders, high-intensity beams, electron-ion colliders, and
necessary R&D for future accelerator technologies.Comment: 26 page
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Vacuum System of the High Energy Ring of an Asymmetric B-Factory Based on Pep
The multi-ampere currents required for high luminosity operation of an asymmetric B factory leads to extremely stressing requirements on a vacuum system suitable for maintaining long beam-gas lifetimes and acceptable background levels in the detector. We present the design for a Cu alloy vacuum chamber and its associated pumping system for the 9 GeV electron storage ring of the proposed B factory based on PEP. The excellent thermal and photo-desorption properties of Cu allows handling the high proton flux in a conventional, single chamber design with distributed ion pumps. The x-ray opacity of the Cu is sufficiently high that no additional lead shielding is necessary to protect the dipoles from the intense synchrotron radiation generated by the beam. The design allows chamber commissioning in <500 hr of operation. 5 refs., 3 figs., 2 tabs
The Three-Boson System at Next-To-Next-To-Leading Order
We discuss effective field theory treatments of the problem of three
particles interacting via short-range forces (range R >> a_2, with a_2 the
two-body scattering length). We show that forming a once-subtracted scattering
equation yields a scattering amplitude whose low-momentum part is
renormalization-group invariant up to corrections of O(R^3/a_2^3). Since
corrections of O(R/a_2) and O(R^2/a_2^2) can be straightforwardly included in
the integral equation's kernel, a unique solution for 1+2 scattering phase
shifts and three-body bound-state energies can be obtained up to this accuracy.
We use our equation to calculate the correlation between the binding energies
of Helium-4 trimers and the atom-dimer scattering length. Our results are in
excellent agreement with the recent three-dimensional Faddeev calculations of
Roudnev and collaborators that used phenomenological inter-atomic potentials.Comment: 20 pages, 3 eps figure
Scaling predictions for radii of weakly bound triatomic molecules
The mean-square radii of the molecules He, HeLi,
HeLi and HeNa are calculated using a three-body model
with contact interactions. They are obtained from a universal scaling function
calculated within a renormalized scheme for three particles interacting through
pairwise Dirac-delta interaction. The root-mean-square distance between two
atoms of mass in a triatomic molecule are estimated to be of de order of
, where is the dimer and the
trimer binding energies, and is a constant (varying from
to ) that depends on the ratio between and . Considering
previous estimates for the trimer energies, we also predict the sizes of
Rubidium and Sodium trimers in atomic traps.Comment: 7 pages, 2 figure
Proton pump inhibitors increase the risk for hospital-acquired Clostridium difficile infection in critically ill patients
The ^4He trimer as an Efimov system
We review the results obtained in the last four decades which demonstrate the
Efimov nature of the He three-atomic system.Comment: Review article for a special issue of the Few-Body Systems journal
devoted to Efimov physic
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