512 research outputs found
Common Space of Spin and Spacetime
Given Lorentz invariance in Minkowski spacetime, we investigate a common
space of spin and spacetime. To obtain a finite spinor representation of the
non-compact homogeneous Lorentz group including Lorentz boosts, we introduce an
indefinite inner product space (IIPS) with a normalized positive probability.
In this IIPS, the common momentum and common variable of a massive fermion turn
out to be ``doubly strict plus-operators''. Due to this nice property, it is
straightforward to show an uncertainty relation between fermion mass and proper
time. Also in IIPS, the newly-defined Lagrangian operators are self-adjoint,
and the fermion field equations are derivable from the Lagrangians. Finally,
the nonlinear QED equations and Lagrangians are presented as an example.Comment: 17 pages, a reference corrected, final version published on
Foundations of Physics Letters in June of 2005, as a personal tribute to
Einstein and Dira
Interference between the halves of a double-well trap containing a Bose-Einstein condensate
Interference between the halves of a double-well trap containing a
Bose-Einstein condensate is studied. It is found that when the atoms in the two
wells are initially in the coherent state, the intensity exhibits collapses and
revivals, but it does not for the initial Fock states. Whether the initial
states are in the coherent states or in a Fock states, the fidelity time has
nothing to do with collision. We point out that interference and its fidelity
can be adjusted experimentally by properly preparing the number and initial
states of the system.Comment: 10 pages, 3 figures, accepted by Phy. rev.
Attenuation of leukocyte sequestration by selective blockade of PECAM-1 or VCAM-1 in murine endotoxemia
Background: Molecular mechanisms regulating leukocyte sequestration into the tissue during endotoxemia and/or sepsis are still poorly understood. This in vivo study investigates the biological role of murine PECAM-1 and VCAM-1 for leukocyte sequestration into the lung, liver and striated skin muscle. Methods: Male BALB/c mice were injected intravenously with murine PECAM-1 IgG chimera or monoclonal antibody (mAb) to VCAM-1 ( 3 mg/kg body weight); controls received equivalent doses of IgG2a ( n = 6 per group). Fifteen minutes thereafter, 2 mg/kg body weight of Salmonella abortus equi endotoxin was injected intravenously. At 24 h after the endotoxin challenge, lungs, livers and striated muscle of skin were analyzed for their myeloperoxidase activity. To monitor intravital leukocyte-endothelial cell interactions, fluorescence videomicroscopy was performed in the skin fold chamber model of the BALB/c mouse at 3, 8 and 24 h after injection of endotoxin. Results: Myeloperoxidase activity at 24 h after the endotoxin challenge in lungs (12,171 +/- 2,357 mU/g tissue), livers ( 2,204 +/- 238 mU/g) and striated muscle of the skin ( 1,161 +/- 110 mU/g) was significantly reduced in both treatment groups as compared to controls, with strongest attenuation in the PECAM-1 IgG treatment group. Arteriolar leukocyte sticking at 3 h after endotoxin (230 +/- 46 cells x mm(-2)) was significantly reduced in both treatment groups. Leukocyte sticking in postcapillary venules at 8 h after endotoxin ( 343 +/- 69 cells/mm(2)) was found reduced only in the VCAM-1-mAb-treated animals ( 215 +/- 53 cells/mm(2)), while it was enhanced in animals treated with PECAM-1 IgG ( 572 +/- 126 cells/mm(2)). Conclusion: These data show that both PECAM-1 and VCAM-1 are involved in endotoxin-induced leukocyte sequestration in the lung, liver and muscle, presumably through interference with arteriolar and/or venular leukocyte sticking. Copyright (C) 2004 S. Karger AG, Basel
Tensor meson exchange at low energies
We complete the analysis of meson resonance contributions to chiral
low-energy constants of O(p^4) by including all quark-antiquark bound states
with orbital angular momentum less or equal to one. Different tensor meson
Lagrangians used in previous work are shown to produce the same final results
for the low-energy constants once QCD short-distance constraints are properly
implemented. We also discuss the possible relevance of axial-vector mesons with
odd C-parity.Comment: 20 pages, comparison with previous work updated, typos removed,
results unchanged, version to appear in EPJ
Virtual Effects of Split SUSY in Higgs Productions at Linear Colliders
In split supersymmetry the gauginos and higgsinos are the only supersymmetric
particles possibly accessible at foreseeable colliders like the CERN Large
Hadron Collider (LHC) and the International Linear Collider (ILC). In order to
account for the cosmic dark matter measured by WMAP, these gauginos and
higgsinos are stringently constrained and could be explored at the colliders
through their direct productions and/or virtual effects in some processes. The
clean environment and high luminosity of the ILC render the virtual effects of
percent level meaningful in unraveling the new physics effects. In this work we
assume split supersymmetry and calculate the virtual effects of the
WMAP-allowed gauginos and higgsinos in Higgs productions e+e- -> Z h and e+e-
-> \nu_e \bar_\nu_e h through WW fusion at the ILC. We find that the production
cross section of e+e- -> Zh can be altered by a few percent in some part of the
WMAP-allowed parameter space, while the correction to the WW-fusion process
e+e- -> \nu_e \bar_\nu_e h is below 1%. Such virtual effects are correlated
with the cross sections of chargino pair productions and can offer
complementary information in probing split supersymmetry at the colliders.Comment: more discussions added (7 pages, 10 figs
\psi(2S) Decays into \J plus Two Photons
Using \gamma \gamma J/\psi, J/\psi \ra e^+ e^- and events
from a sample of \psip decays collected with the BESII
detector, the branching fractions for \psip\ra \pi^0\J, \eta\J, and
\psi(2S)\ar\gamma\chi_{c1},\gamma\chi_{c2}\ar\gamma\gamma\jpsi are measured
to be B(\psip\ra \pi^0\J) = (1.43\pm0.14\pm0.13)\times 10^{-3}, B(\psip\ra
\eta\J) = (2.98\pm0.09\pm0.23)%,
B(\psi(2S)\ar\gamma\chi_{c1}\ar\gamma\gamma\jpsi) = (2.81\pm0.05\pm 0.23)%,
and B(\psi(2S)\ar\gamma\chi_{c2}\ar\gamma\gamma\jpsi) = (1.62\pm0.04\pm
0.12)%.Comment: 7 pages, 6 figures. submitted to Phys. Rev.
Inelastic neutrino and antineutrino scattering on nuclei and ``strangeness'' of the nucleon
Possibilities to extract information on the strange form factors of the
nucleon from neutrino (antineutrino) inelastic scattering on nuclei, in an
energy range from 200 MeV to 1 GeV and more, are investigated in detail. All
calculations are performed within two relativistic independent particle models
(Fermi gas and shell model); the final state interactions of the ejected
nucleon are taken into account through relativistic optical model potentials.
We have shown that the values of the cross sections significantly depend on the
nuclear model (especially in the lower energy range). However the NC/CC
neutrino-antineutrino asymmetry in a medium--high energy range shows a rather
small dependence on the model and allows to disentangle different values of the
parameters that characterize the strange form factors. We have calculated also
the ratio of the cross sections for inelastic NC scattering of neutrinos on
nuclei, with the emission of a proton and of a neutron. Our calculations show
that this ratio depends rather weakly on the nuclear model and confirm previous
conclusions on the rather strong dependence of this ratio upon the axial
strange form factors.Comment: RevTeX file, 35 pages including 12 figure
Longitudinal double-spin asymmetry and cross section for inclusive neutral pion production at midrapidity in polarized proton collisions at sqrt(s) = 200 GeV
We report a measurement of the longitudinal double-spin asymmetry A_LL and
the differential cross section for inclusive Pi0 production at midrapidity in
polarized proton collisions at sqrt(s) = 200 GeV. The cross section was
measured over a transverse momentum range of 1 < p_T < 17 GeV/c and found to be
in good agreement with a next-to-leading order perturbative QCD calculation.
The longitudinal double-spin asymmetry was measured in the range of 3.7 < p_T <
11 GeV/c and excludes a maximal positive gluon polarization in the proton. The
mean transverse momentum fraction of Pi0's in their parent jets was found to be
around 0.7 for electromagnetically triggered events.Comment: 6 pages, 3 figures, submitted to Phys. Rev. D (RC
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