149 research outputs found
Signature inversion in axially deformed Tm
The microscopic analysis of experimental data in Tm is presented
within the two-quasiparticle-phonon model. The model includes the interaction
between odd quasiparticles and their coupling with core vibrations. The
coupling explains naturally the attenuation of the Coriolis interaction in
rotating odd-odd nuclei. It is shown that the competition between the Coriolis
and neutron-proton interactions is responsible for the signature inversion
phenomenon.Comment: 10 pages, 1 figure, corrected some typo
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Proposed Few-optical Cycle Laser-driven ParticleAccelerator Structure
We describe a transparent dielectric grating accelerator structure that is designed for ultra-short laser pulse operation. The structure is based on the principle of periodic field reversal to achieve phase synchronicity for relativistic particles, however to preserve ultra-short pulse operation it does not resonate the laser field in the vacuum channel. The geometry of the structure appears well suited for application with high average power lasers and high thermal loading. Finally, it shows potential for an unloaded gradient of 10 GeV/m with 10 fsec laser pulses and the possibility to accelerate 10{sup 6} electrons per bunch at an efficiency of 8%. The fabrication procedure and a proposed near term experiment with this accelerator structure are presented
Justifying the Special Theory of Relativity with Unconceived Methods
Many realists argue that present scientific theories will not follow the fate of past scientific theories because the former are more successful than the latter. Critics object that realists need to show that present theories have reached the level of success that warrants their truth. I reply that the special theory of relativity has been repeatedly reinforced by unconceived scientific methods, so it will be reinforced by infinitely many unconceived scientific methods. This argument for the special theory of relativity overcomes the critics’ objection, and has advantages over the no-miracle argument and the selective induction for it
Lifetime determination of excited states in Cd-106
Two separate experiments using the Differential Decay Curve Method have been performed to extract mean lifetimes of excited states in 106 Cd. The inedium-spin states of interest were populated by the Mo-98(C-12, 4n) Cd-106 reaction performed at the Wright Nuclear Structure Lab., Yale University. From this experiment, two isomeric state mean lifetimes have been deduced. The low-lying states were populated by the Mo-96(C-13, 3n)Cd-106 reaction performed at the Institut fur Kernphysik, Universitat zu Koln. The mean lifetime of the I-pi = 2(1)(+) state was deduced, tentatively, as 16.4(9) ps. This value differs from the previously accepted literature value from Coulomb excitation of 10.43(9) ps
Comparison of Isoscalar Vector Meson Production Cross Sections in Proton-Proton Collisions
The reaction was investigated with the TOF
spectrometer, which is an external experiment at the accelerator COSY
(Forschungszentrum J\"ulich, Germany). Total as well as differential cross
sections were determined at an excess energy of (). Using the total cross section of for the
reaction determined here and existing data for the reaction
, the ratio
turns out to be
significantly larger than expected by the Okubo-Zweig-Iizuka (OZI) rule. The
uncertainty of this ratio is considerably smaller than in previous
determinations. The differential distributions show that the
production is still dominated by S-wave production at this excess energy,
however higher partial waves clearly contribute. A comparison of the measured
angular distributions for production to published distributions for
production at shows that the data are consistent with an
identical production mechanism for both vector mesons
Very high rotational frequencies and band termination in 73Br
Rotational bands in 73Br have been investigated up to spins of 65/2 using the
EUROBALL III spectrometer. One of the negative-parity bands displays the
highest rotational frequency 1.85 MeV reported to date in nuclei with mass
number greater than 25. At high frequencies, the experimental dynamic moment of
inertia for all bands decrease to very low values, indicating a loss of
collectivity. The bands are described in the configuration-dependent cranked
Nilsson-Strutinsky model. The calculations indicate that one of the
negative-parity bands is observed up to its terminating single-particle state
at spin 63/2. This result establishes the first band termination case in the A
= 70 mass region.Comment: 6 pages, 6 figures, submitted to Phys. Rev. C as a Rapid
Communicatio
Direct comparison of phase-space distributions of K- and K+ mesons in heavy-ion collisions at SIS energies - evidence for in-medium modifications of kaons ?
The ratio of K- to K+ meson yields has been measured in the systems RuRu at
1.69 A GeV, Ru+Zr at 1.69 A GeV, and Ni+Ni at 1.93 A GeV incident beam kinetic
energy. The yield ratio is observed to vary across the measured phase space.
Relativistic transport-model calculations indicate that the data are best
understood if in-medium modifications of the kaons are taken into account.Comment: 14 pages including 3 figure
Identification of baryon resonances in central heavy-ion collisions at energies between 1 and 2 AGeV
The mass distributions of baryon resonances populated in near-central
collisions of Au on Au and Ni on Ni are deduced by defolding the spectra
of charged pions by a method which does not depend on a specific resonance
shape. In addition the mass distributions of resonances are obtained from the
invariant masses of pairs. With both methods the deduced mass
distributions are shifted by an average value of -60 MeV/c relative to the
mass distribution of the free resonance, the distributions
descent almost exponentially towards mass values of 2000 MeV/c^2. The observed
differences between and pairs indicate a contribution
of isospin resonances. The attempt to consistently describe the
deduced mass distributions and the reconstructed kinetic energy spectra of the
resonances leads to new insights about the freeze out conditions, i.e. to
rather low temperatures and large expansion velocities.Comment: 30 pages, 13 figures, Latex using documentstyle[12pt,a4,epsfig], to
appear in Eur. Phys. J.
Production of mesons in proton-proton collisions
The cross section for the production of mesons in proton-proton
collisions has been measured in a previously unexplored region of incident
energies. Cross sections were extracted at 92 MeV and 173 MeV excess energy,
respectively. The angular distribution of the at =173 MeV is
strongly anisotropic, demonstrating the importance of partial waves beyond pure
s-wave production at this energy.Comment: 12 pages, 4 figures submitted to Physics Letters B v2: figure 1
added, discussion detailing the data analysis, figure 3 (fig. 2 in v1)
modified in line styles and systematic errors displayed on dat
Sideward flow of K+ mesons in Ru+Ru and Ni+Ni reactions near threshold
Experimental data on K+ meson and proton sideward flow measured with the FOPI
detector at SIS/GSI in the reactions Ru+Ru at 1.69 AGeV and Ni+Ni at 1.93 AGeV
are presented. The K+ sideward flow is found to be anti-correlated (correlated)
with the one of protons at low (high) transverse momenta. When compared to the
predictions of a transport model, the data favour the existence of an in-medium
repulsive K+ nucleon potential.Comment: 16 pages Revtex, 3 ps-figures, submitted to Phys. Lett.
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