13,281 research outputs found
Lepton Mass Effects in Single Pion Production by Neutrinos
We reconsider the Feynman-Kislinger-Ravndal model applied to
neutrino-excitation of baryon resonances. The effects of lepton mass are
included, using the formalism of Kuzmin, Lyubushkin and Naumov. In addition we
take account of the pion-pole contribution to the hadronic axial vector
current. Application of this new formalism to the reaction nu(mu) + p --> mu +
Delta at E(nu) approx 1 GeV gives a suppressed cross section at small angles,
in agreement with the screening correction in Adler's forward scattering
theorem. Application to the process nu(tau) + p --> tau + Delta at E(nu) approx
7 GeV leads to the prediction of right-handed tau polarization for
forward-going leptons, in line with a calculation based on an isobar model. Our
formalism represents an improved version of the Rein-Sehgal model,
incorporating lepton mass effects in a manner consistent with PCAC.Comment: 14 pages, 5 figures. Typos in eq. 9 and 27 corrected. Numbers in
table I for coherent cross sections (RSA and RSC) corrected (normalization
error). Figs 3 and 4 changed accordingly. These corrections also apply to the
published version PRD 76, 113004 (2007
Second Order Correlation Function of a Phase Fluctuating Bose-Einstein Condensate
The coherence properties of phase fluctuating Bose-Einstein condensates are
studied both theoretically and experimentally. We derive a general expression
for the N-particle correlation function of a condensed Bose gas in a highly
elongated trapping potential. The second order correlation function is analyzed
in detail and an interferometric method to directly measure it is discussed and
experimentally implemented. Using a Bragg diffraction interferometer, we
measure intensity correlations in the interference pattern generated by two
spatially displaced copies of a parent condensate. Our experiment demonstrates
how to characterize the second order correlation function of a highly elongated
condensate and to measure its phase coherence length.Comment: 22 pages, 5 figure
Regular Incidence Complexes, Polytopes, and C-Groups
Regular incidence complexes are combinatorial incidence structures
generalizing regular convex polytopes, regular complex polytopes, various types
of incidence geometries, and many other highly symmetric objects. The special
case of abstract regular polytopes has been well-studied. The paper describes
the combinatorial structure of a regular incidence complex in terms of a system
of distinguished generating subgroups of its automorphism group or a
flag-transitive subgroup. Then the groups admitting a flag-transitive action on
an incidence complex are characterized as generalized string C-groups. Further,
extensions of regular incidence complexes are studied, and certain incidence
complexes particularly close to abstract polytopes, called abstract polytope
complexes, are investigated.Comment: 24 pages; to appear in "Discrete Geometry and Symmetry", M. Conder,
A. Deza, and A. Ivic Weiss (eds), Springe
Characterization and control of phase fluctuations in elongated Bose-Einstein condensates
Quasi one dimensional Bose-Einstein condensates (BECs) in elongated traps
exhibit significant phase fluctuations even at very low temperatures. We
present recent experimental results on the dynamic transformation of phase
fluctuations into density modulations during time-of-flight and show the
excellent quantitative agreement with the theoretical prediction. In addition
we confirm that under our experimental conditions, in the magnetic trap density
modulations are strongly suppressed even when the phase fluctuates. The paper
also discusses our theoretical results on control of the condensate phase by
employing a time-dependent perturbation. Our results set important limitations
on future applications of BEC in precision atom interferometry and atom optics,
but at the same time suggest pathways to overcome these limitations.Comment: 9 pages, 7 figure
Tables of Overlap Integrals. II. Bonds between Some First Row and Second Row Atoms
Tables of overlap integrals for some bonds between the first
row atoms and the second row atoms are given. They are based on
atomic orbitals o,f Clementi and include the basic overlap integrals
of the valence shell orbitals only, i. e. overlaps between 2s anu 2p
orbitals of the first row atoms with 3s and 3p orbitals of tne second
row atoms. The intervals of interatomic distances are lim~ted so as
to cover known _variations in bond lengths reported in the, literature
Tables of Overlap Integrals
Tables of overlap integrals for bonds between the first row
atoms and their hydrides are given. They are based on atomic
orbitals suggested by Clementi, which provide a more reliable
guide to the description of bonds than do Slater orbitals. The
region of interatomic distances is limited so as to cover known
bond lengths found in the literature
Tables of Overlap Integrals. II. Bonds between Some First Row and Second Row Atoms
Tables of overlap integrals for some bonds between the first
row atoms and the second row atoms are given. They are based on
atomic orbitals o,f Clementi and include the basic overlap integrals
of the valence shell orbitals only, i. e. overlaps between 2s anu 2p
orbitals of the first row atoms with 3s and 3p orbitals of tne second
row atoms. The intervals of interatomic distances are lim~ted so as
to cover known _variations in bond lengths reported in the, literature
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