7,975 research outputs found
Antiproton-Proton Channels in J/psi Decays
The recent measurements by the BES Collaboration of J/psi decays into a
photon and a proton-antiproton pair indicate a strong enhancement at the
proton-antiproton threshold not observed in the decays into a neutral pion and
a proton-antiproton pair. Is this enhancement due to a proton-antiproton
quasi-bound state or a baryonium? A natural explanation follows from a
traditional model of proton-antiproton interactions based on G-parity
transformation. The observed proton-antiproton structure is due to a strong
attraction in the 1S0 state, and possibly to a near-threshold quasi-bound state
in the 11S0 wave.Comment: 6 pages, 5 figures. The antiproton-proton pair being in isospin one
in the J/Psi decay into neutral pion-antiproton-proton, the antiproton-proton
1P1 and 3S1 waves have been replaced by the 31P1 and 33S1 ones and Figs. 1
and 2 have been replaced accordingly. Conclusions are unchanged. Most of the
content of the paper is published in Phys. Rev. C72, 011001 (2005
Pulse generation without gain-bandwidth limitation in a laser with self-similar evolution
With existing techniques for mode-locking, the bandwidth of ultrashort pulses from a laser is determined primarily by the spectrum of the gain medium. Lasers with self-similar evolution of the pulse in the gain medium can tolerate strong spectral breathing, which is stabilized by nonlinear attraction to the parabolic self-similar pulse. Here we show that this property can be exploited in a fiber laser to eliminate the gain-bandwidth limitation to the pulse duration. Broad (̃200 nm) spectra are generated through passive nonlinear propagation in a normal-dispersion laser, and these can be dechirped to ̃20-fs duration
Engineering multiple levels of specificity in an RNA viral vector
Synthetic molecular circuits could provide powerful therapeutic capabilities, but delivering them to specific cell types and controlling them remains challenging. An ideal "smart" viral delivery system would enable controlled release of viral vectors from "sender" cells, conditional entry into target cells based on cell-surface proteins, conditional replication specifically in target cells based on their intracellular protein content, and an evolutionarily robust system that allows viral elimination with drugs. Here, combining diverse technologies and components, including pseudotyping, engineered bridge proteins, degrons, and proteases, we demonstrate each of these control modes in a model system based on the rabies virus. This work shows how viral and protein engineering can enable delivery systems with multiple levels of control to maximize therapeutic specificity
Multiscale Technicolor and the Zbb-bar Vertex
We estimate the correction to the Zbb-bar vertex arising from the exchanges
of the sideways extended technicolor (ETC) boson and the flavor-diagonal ETC
boson in the multiscale walking technicolor model. The obtained result is too
large to explain the present data. However, if we introduce a new self-
interaction for the top quark to induce the top quark condensate serving as the
origin of the large top quark mass, the corrected R_b=Gamma_b/Gamma_h can be
consistent with the recent LEP data. The corresponding correction to
R_c=Gamma_c/Gamma_h is shown to be negligibly small.Comment: 9-page LaTex fil
transition form factor within Light Front Quark Model
We study the transition form factor of as a
function of the momentum transfer within the light-front quark model
(LFQM). We compare our result with the experimental data by BaBar as well as
other calculations based on the LFQM in the literature. We show that our
predicted form factor fits well with the experimental data, particularly those
at the large region.Comment: 11 pages, 4 figures, accepted for publication in PR
Characterizing anomalies in distributed strain measurements of cast-in-situ bored piles
This paper describes the method of identifying typical defects of bored cast-in-situ piles when instrumenting using Distributed Optical Fiber Strain Sensing (DOFSS). The DOFSS technology is based on Brillouin Optical Time Domain Analyses (BOTDA), which has the advantage of recording continuous strain profile as opposed to the conventional discrete based sensors such as Vibrating Wire strain gauges. In pile instrumentation particularly, obtaining distributed strain profile is important when analysing the load-transfer and shaft friction of a pile, as well as detecting any anomalies in the strain regime. Features such as defective pile shaft necking, discontinuity of concrete, intrusion of foreign matter and improper toe formation due to contamination of concrete at base with soil particles, among others, may cause the pile to fail. In this study, a new technique of detecting such defects is proposed using DOFSS technology which can potentially supplement the existing non-destructive test (NDT) methods. Discussion on the performance of instrumented piles by means of maintained load test are also presented
Spectroscopy and Dynamics of the Predissociated, Quasi-linear S2 State of Chlorocarbene
In this work, we report on the spectroscopy and dynamics of the quasi-linear S2 state of chlorocarbene, CHCl, and its deuterated isotopologue using optical-optical double resonance (OODR) spectroscopy through selected rovibronic levels of the S1 state. This study, which represents the first observation of the S2 state in CHCl, builds upon our recent examination of the corresponding state in CHF, where pronounced mode specificity was observed in the dynamics, with predissociation rates larger for levels containing bending excitation. In the present work, a total of 14 S2 state vibrational levels with angular momentum ℓ = 1 were observed for CHCl, and 34 levels for CDCl. The range of ℓ in this case was restricted by the pronounced Renner-Teller effect in the low-lying S1 levels, which severely reduces the fluorescence lifetime for levels with Ka \u3e 0. Nonetheless, by exploiting different intermediate S1 levels, we observed progressions involving all three fundamental vibrations. For levels with long predissociation lifetimes, rotational constants were determined by measuring spectra through different intermediate J levels of the S1 state. Plots of the predissociation linewidth (lifetime) vs. energy for various S2 levels show an abrupt onset, which lies near the calculated threshold for elimination to form C(3P) + HCl on the triplet surface. Our experimental results are compared with a series of high level ab initio calculations, which included the use of a dynamically weighted full-valence CASSCF procedure, focusing maximum weight on the state of interest (the singlet and triplet states were computed separately). This was used as the reference for subsequent Davidson-corrected MRCI(+Q) calculations. These calculations reveal the presence of multiple conical intersections in the singlet manifold
Extending the first-order post-Newtonian scheme in multiple systems to the second-order contributions to light propagation
In this paper, we extend the first-order post-Newtonian scheme in multiple
systems presented by Damour-Soffel-Xu to the second-order contribution to light
propagation without changing the virtueof the scheme on the linear partial
differential equations of the potential and vector potential. The spatial
components of the metric are extended to second order level both in a global
coordinates () and a local coordinates (). The
equations of (or ) are obtained from the field equations.The
relationship between and are presented in this paper also. In
special case of the solar system (isotropic condition is applied ()), we obtain the solution of . Finally, a further extension
of the second-order contributions in the parametrized post-Newtonian formalism
is discussed.Comment: Latex2e; 6 pages PS fil
Detection of Gravitational Wave - An Application of Relativistic Quantum Information Theory
We show that a passing gravitational wave may influence the spin entropy and
spin negativity of a system of massive spin-1/2 particles, in a way that is
characteristic of the radiation. We establish the specific conditions under
which this effect may be nonzero. The change in spin entropy and negativity,
however, is extremely small. Here, we propose and show that this effect may be
amplified through entanglement swapping. Relativistic quantum information
theory may have a contribution towards the detection of gravitational wave.Comment: 9 page
Thermodynamical Metrics and Black Hole Phase Transitions
An important phase transition in black hole thermodynamics is associated with
the divergence of the specific heat with fixed charge and angular momenta, yet
one can demonstrate that neither Ruppeiner's entropy metric nor Weinhold's
energy metric reveals this phase transition. In this paper, we introduce a new
thermodynamical metric based on the Hessian matrix of several free energy. We
demonstrate, by studying various charged and rotating black holes, that the
divergence of the specific heat corresponds to the curvature singularity of
this new metric. We further investigate metrics on all thermodynamical
potentials generated by Legendre transformations and study correspondences
between curvature singularities and phase transition signals. We show in
general that for a system with n-pairs of intensive/extensive variables, all
thermodynamical potential metrics can be embedded into a flat (n,n)-dimensional
space. We also generalize the Ruppeiner metrics and they are all conformal to
the metrics constructed from the relevant thermodynamical potentials.Comment: Latex, 25 pages, reference added, typos corrected, English polished
and the Hawking-Page phase transition clarified; to appear in JHE
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