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141.
W. Deconinck 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):653-655
An experimental search for the Θ(1540)- and Λ(1520)-resonance was performed in quasi-real photoproduction on deuterium at the HERMES experiment. While evidence for Θ(1540) was found in the decay channel pK
0
S→pπ
+
π
-, no evidence for the corresponding anti-particle was found. In some models it is expected that the Θ(1540) and the Λ(1520) have similar production mechanisms. The photoproduction cross-sections for the Λ(1520) in the decay channel Λ(1520)→pK
- and the corresponding anti-particle are determined. The partial photoproduction cross-sections for Λ(1520) and ˉ(1520) are obtained as σ
Λ(1520) = 65.3±8.8(stat)±6.9(syst)nb and σ
ˉ(1520) = 9.8±2.6(stat)±0.9(syst)nb, corresponding to a ratio R
Λ(1520) = σ
ˉ(1520)/σ
Λ(1520) = 0.15±0.05(stat)±0.02(syst). 相似文献
142.
R. R. Mhaskar S. E. Olson G. Raithel 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(2):221-227
A method of imaging distributions of cold atoms under the presence of large
trapping-field-induced level shifts is investigated. By utilizing a probe
laser tuned to an open transition, the fluorescence yield per atom is
largely fixed throughout the trap volume, independent of the trapping
field. This enables a reliable conversion of fluorescence images into
atomic-density profiles. The method is applied to measure distributions of
87Rb atoms in a high-gradient (2.7 kG/cm) magnetic atom guide. We
characterize the parameters for which the open-channel imaging method
performs best. Results of quantum Monte Carlo simulations verify the
underlying assumptions of the method. 相似文献
143.
144.
145.
146.
We characterize a method of heat-assisted magnetic probe recording on perpendicular media. Heating source is field emission current from a scanning tunneling microscope (STM) tip. Recording media are three kinds of magnetic films, Co/Pt, CoNi/Pt, and Co/Pd multilayers with different nucleation fields. Pulses with amplitude of 5 V were applied between the STM tip and the recording medium. Experiments show that magnetic marks with an average size of 180 nm were formed on both Co/Pt and CoNi/Pt films whose nucleation fields are greater than their saturation magnetization. No marks were observed on the Co/Pd film whose nucleation field is smaller than its saturation magnetization. A model is built to simulate the dynamic process of domain formation in probe-based magnetic recording system. Simulation results agree with experiments and it explains the effect of the nucleation field of medium in perpendicular recording. 相似文献
147.
V. I. Telnov 《Pramana》2007,69(6):957-961
At linear colliders, the e
+
e
− luminosity is limited by beam-collision effects, which determine the required emittances of beams in damping rings (DRs).
In γγ collisions at the photon collider, these effects are absent, and so smaller emittances are desirable. In the present damping
ring designs, nominal DR parameters correspond to those required for e
+
e
− collisions. In this note, I would like to stress once again that as soon as we plan the photon collider mode of ILC operation,
the damping ring emittances are dictated by the photon collider requirements — namely, they should be as small as possible.
This can be achieved by adding more wigglers to the DRs; the incremental cost is easily justified by a considerable potential
improvement of the γγ luminosity. No expert analysis exists as of now, but it seems realistic to obtain a factor five increase of the γγ luminosity compared to the ‘nominal’ DR design.
相似文献
148.
H. Jensen J. Kröger N. Néel R. Berndt 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,45(3):465-469
Clusters on surfaces have been investigated with low-temperature scanning tunnelling microscopy and spectroscopy. Constant
current spectra acquired on Ag oligomers and one-dimensional chains on a Ag(111) reveal a
single resonance peak whose energy shifts towards the Fermi level with increasing cluster size. Next, controlled and reproducible
contact between a STM tip and a C60 molecule adsorbed on Cu(100) is reported. The
transition from tunnelling to contact is discussed in terms of local heating of the tip-molecule junction. 相似文献
149.
D. Khalil A. Makhoute A. Maquet G. Rahali M. Zitane 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(2):287-295
The dynamics of laser-assisted elastic collisions in
helium is studied using the second-order Born approximation.
Detailed calculations of the scattering amplitudes are performed
by using the Sturmian basis expansion. Differential cross sections
for elastic scattering with the net absorption/emission of up to
two photons are calculated for collision energies of 5 eV, 10 eV,
and 20 eV. We discuss the influence of the low-energy electrons on
the differential cross section (DCS) as a function of the
scattering angle for selected choices of the laser frequency and
the number of photons exchanged between the external field and
electron-helium system. 相似文献
150.
Shuzheng Yang Qingquan Jiang Huiling Li 《International Journal of Theoretical Physics》2007,46(3):625-636
The strictly thermal spectrum in dragging coordinate system and the tunneling radiation characteristics of stationary axisymmetry
Kerr-Newman de Sitter black hole is studied. The result shows that the tunneling rates at the event and cosmological horizon
are related to the change of Bekenstein-Hawking entropy and that the factual radiation spectrum is not strictly pure thermal.
Thus an exact correction to the Hawking thermal spectrum is present. 相似文献