517 research outputs found
Experimental demonstration of painting arbitrary and dynamic potentials for Bose-Einstein condensates
There is a pressing need for robust and straightforward methods to create
potentials for trapping Bose-Einstein condensates which are simultaneously
dynamic, fully arbitrary, and sufficiently stable to not heat the ultracold
gas. We show here how to accomplish these goals, using a rapidly-moving laser
beam that "paints" a time-averaged optical dipole potential in which we create
BECs in a variety of geometries, including toroids, ring lattices, and square
lattices. Matter wave interference patterns confirm that the trapped gas is a
condensate. As a simple illustration of dynamics, we show that the technique
can transform a toroidal condensate into a ring lattice and back into a toroid.
The technique is general and should work with any sufficiently polarizable
low-energy particles.Comment: Minor text changes and three references added. This is the final
version published in New Journal of Physic
Scotland, Catalonia and the “right” to self-determination: a comment suggested by Kathryn Crameri’s “Do Catalans Have the Right to Decide?
No abstract available
Possible Indication of Narrow Baryonic Resonances Produced in the 1720-1790 MeV Mass Region
Signals of two narrow structures at M=1747 MeV and 1772 MeV were observed in
the invariant masses M_{pX} and M_{\pi^{+}X} of the pp->ppX and pp->p\pi^{+}X
reactions respectively. Many tests were made to see if these structures could
have been produced by experimental artefacts. Their small widths and the
stability of the extracted masses lead us to conclude that these structures are
genuine and may correspond to new exotic baryons. Several attempts to identify
them, including the possible "missing baryons" approach, are discussed.Comment: 17 pages including 8 figures and 3 tables. ReVte
Responsivity mapping techniques for the non-positional CCD: the swept charge device CCD236
The e2v CCD236 is a swept charge device (SCD) designed as a soft X-ray detector for spectroscopy in the range 0.8 keV to 10 keV [1]. It benefits from improvements in design over the previous generation of SCD (the e2v CCD54) [2] to allow for increased detector area, a reduction in split X-ray events and improvements to radiation hardness [3]. To enable the suppression of surface dark current the device is clocked continuously, therefore there is no positional information making responsivity variations difficult to measure. This paper describes investigated techniques to achieve a responsivity map across the device using masking and XRF, and spot illumination from an organic light-emitting diode (OLED). The results of this technique should allow a deeper understanding of the device sensitivity and allow better data interpretation in SCD applications
Law, Liberty and the Rule of Law (in a Constitutional Democracy)
In the hunt for a better--and more substantial--awareness of the “law,” The author intends to analyze the different notions related to the “rule of law” and to criticize the conceptions that equate it either to the sum of “law” and “rule” or to the formal assertion that “law rules,” regardless of its relationship to certain principles, including both “negative” and “positive” liberties. Instead, he pretends to scrutinize the principles of the “rule of law,” in general, and in a “constitutional democracy,” in particular, to conclude that the tendency to reduce the “democratic principle” to the “majority rule” (or “majority principle”), i.e. to whatever pleases the majority, as part of the “positive liberty,” is contrary both to the “negative liberty” and to the “rule of law” itself
Cooperative damping mechanism of the resonance in the nuclear photoabsorption
We propose a resonance damping mechanism to explain the disappearance of the
peaks around the position of the resonances higher than the resonance
in the nuclear photoabsorption. This phenomenon is understood by taking into
account the cooperative effect of the collision broadening of and
, the pion distortion and the interference in the two-pion
photoproduction processes in the nuclear medium.Comment: 11 pages, uses revtex.sty. To appear in Phys. Rev. Let
Nuclear Photoabsorption at Photon Energies between 300 and 850 Mev
We construct the formula for the photonuclear total absorption cross section
using the projection method and the unitarity relation. Our treatment is very
effective when interference effects in the absorption processes on a nucleon
are strong. The disappearance of the peak around the position of the
resonance in the nuclear photoabsorption can be explained with the cooperative
effect of the interference in two-pion production processes,the Fermi motion,
the collision broadenings of and , and the pion distortion in the
nuclear medium. The change of the interference effect by the medium plays an
important role.Comment: 22pages,7figures,revtex
Photofission of heavy nuclei at energies up to 4 GeV
Total photofission cross sections for 238U, 235U, 233U, 237Np, 232Th, and
natPb have been measured simultaneously, using tagged photons in the energy
range Egamma=0.17-3.84 GeV. This was the first experiment performed using the
Photon Tagging Facility in Hall B at Jefferson Lab. Our results show that the
photofission cross section for 238U relative to that for 237Np is about 80%,
implying the presence of important processes that compete with fission. We also
observe that the relative photofission cross sections do not depend strongly on
the incident photon energy over this entire energy range. If we assume that for
237Np the photofission probability is equal to unity, we observe a significant
shadowing effect starting below 1.5 GeV.Comment: 4 pages of RevTex, 6 postscript figures, Submitted to Phys. Rev. Let
- …