1,144 research outputs found
Scaling and Duality in Semi-exclusive Processes
We discuss extending scaling and duality studies to semi-exclusive processes.
We show that semi-exclusive hard pion photoproduction should exhibit scaling
behavior in kinematic regions where the photon and pion both interact directly
with the same quark. We show that such kinematic regions exist. We also show
that the constancy with changing momentum transfer of the resonance
peak/scaling curve ratio, familiar for many resonances in deep inelastic
scattering, is also expected in the semi-exclusive case.Comment: 8 pages, 4 figures, submitted to Phys.Rev.
Single-shot measurement of quantum optical phase
Although the canonical phase of light, which is defined as the complement of
photon number, has been described theoretically by a variety of distinct
approaches, there have been no methods proposed for its measurement. Indeed
doubts have been expressed about whether or not it is measurable. Here we show
how it is possible, at least in principle, to perform a single-shot measurement
of canonical phase using beam splitters, mirrors, phase shifters and
photodetectors.Comment: This paper was published in PRL in 2002 but, at the time, was not
placed on the archive. It is included now to make accessing this paper easie
Approach to Perturbative Results in the N-Delta Transition
We show that constraints from perturbative QCD calculations play a role in
the nucleon to Delta(1232) electromagnetic transition even at moderate momentum
transfer scales. The pQCD constraints, tied to real photoproduction data and
unseparated resonance response functions, lead to explicit forms for the
helicity amplitudes wherein the E2/M1 ratio remains small at moderately large
momentum transfer.Comment: 4 pages, 2 figures, ReVTe
Comparison of Efficacy and Safety of Transcatheter Aortic Valve Implantation in Patients With Bicuspid Versus Tricuspid Aortic Valves
Bicuspid aortic valve (BAV) stenosis has been considered a contraindication to transcatheter aortic valve implantation (TAVI). The aim of this study is to compare the efficacy and safety of TAVI in patients with BAV with those with tricuspid aortic valve (TAV) using balloon-expandable and self-expanding transcatheter heart valves. This retrospective study included 823 consecutive patients with severe, symptomatic aortic valve stenosis undergoing TAVI in 2 institutions, Baylor Heart and Vascular Hospital (Dallas, TX) and The Heart Hospital Baylor Plano (Plano, TX), from January 2012 to February 2016. Efficacy was evaluated by postprocedural valve function as mean gradient, peak velocity, effective orifice area, and ≥moderate paravalvular leak. Safety end points included all-cause 30-day and 1-year mortality, immediate postprocedural mortality and 30-day cardiovascular mortality, procedural success, pacemaker implantation, and procedural complications. Of the 823 included patients, 735 had TAV and 77 had BAV. Baseline characteristics were similar between the 2 groups. Procedural success was high in both BAV and TAV (98.7% vs 99.1%, p = ns). There were no significant differences between groups in valve hemodynamics after TAVI, pacemaker implantation rate, or procedural complications. There were no differences regarding immediate postprocedural mortality (BAV vs TAV, 1.1% vs 0.8%, p = ns), nor 30-day cardiovascular mortality (3.4% vs 2.3%, p = ns). All-cause mortality at 30 days (3.4% vs 3.1%, p = ns) and 1-year (8.5% vs 10.5%) were similar. Patients with BAV showed similar procedural and clinical outcomes to patients with TAV. Therefore, TAVI appears to be a safe and effective procedure for patients with BAVs as well as those with TAVs
The Role of the D13 (1520) Resonance in eta Electroproduction
We investigate the electroproduction of eta mesons below a center of momentum
energy of 1.6 GeV, with particular emphasis on the roles of the N*(1535) and
N*(1520) resonances. Using the effective Lagrangian approach, we show that the
transverse helicity amplitude of the N*(1535) can be extracted with good
accuracy from the new eta electroproduction data, under reasonable assumptions
for the strength of the longitudinal helicity amplitude. In addition, although
the differential cross section is found to to have a small sensitivity to the
N*(1520) resonance, it is shown that a recently completed double polarization
experiment is very sensitive to this resonance.Comment: 7 pages, Revtex, 3 figure
Frequency of and Prognostic Significance of Atrial Fibrillation in Patients Undergoing Transcatheter Aortic Valve Implantation
The prognostic implications of preexisting atrial fibrillation (AF) and new-onset AF (NOAF) in transcatheter aortic valve implantation (TAVI) remain uncertain. This study assesses the epidemiology of AF in patients treated with TAVI and evaluates their outcomes according to the presence of preexisting AF or NOAF. A retrospective analysis of 708 patients undergoing TAVI from 2 heart hospitals was performed. Patients were divided into 3 study groups: sinus rhythm (n = 423), preexisting AF (n = 219), and NOAF (n = 66). Primary outcomes of interest were all-cause death and stroke both at 30-day and at 1-year follow-up. Preexisting AF was present in 30.9% of our study population, whereas NOAF was observed in 9.3% of patients after TAVI. AF and NOAF patients showed a higher rate of 1-year all-cause mortality compared with patients in sinus rhythm (14.6% vs 6.5% for preexisting AF and 16.3% vs 6.5% for NOAF, p = 0.007). No differences in 30-day mortality were observed between groups. In patients with AF (either preexisting and new-onset), those discharged with single antiplatelet therapy displayed higher mortality rates at 1 year (42.9% vs 11.7%, p = 0.006). Preexisting AF remained an independent predictor of mortality at 1-year follow-up (hazard ratio [HR] 2.34, 95% CI 1.22 to 4.48, p = 0.010). Independent predictors of NOAF were transapical and transaortic approach as well as balloon postdilatation (HR 3.48, 95% CI 1.66 to 7.29, p = 0.001; HR 5.08, 95% CI 2.08 to 12.39, p <0.001; HR 2.76, 95% CI 1.25 to 6.08, p = 0.012, respectively). In conclusion, preexisting AF is common in patients undergoing TAVI and is associated with a twofold increased risk of 1-year mortality. This negative effect is most pronounced in patients discharged with single antiplatelet therapy compared with other antithrombotic regimens
Theory Support for the Excited Baryon Program at the Jlab 12 GeV Upgrade
This document outlines major directions in theoretical support for the
measurement of nucleon resonance transition form factors at the JLab 12 GeV
upgrade with the CLAS12 detector. Using single and double meson production,
prominent resonances in the mass range up to 2 GeV will be studied in the range
of photon virtuality up to 12 GeV where quark degrees of freedom are
expected to dominate. High level theoretical analysis of these data will open
up opportunities to understand how the interactions of dressed quarks create
the ground and excited nucleon states and how these interactions emerge from
QCD. The paper reviews the current status and the prospects of QCD based model
approaches that relate phenomenological information on transition form factors
to the non-perturbative strong interaction mechanisms, that are responsible for
resonance formation.Comment: 52 pages, 19 figures, White Paper of the Electromagnetic N-N*
Transition Form Factor Workshop at Jefferson Lab, October 13-15, 2008,
Newport News, VA, US
SU(2) and SU(1,1) algebra eigenstates: A unified analytic approach to coherent and intelligent states
We introduce the concept of algebra eigenstates which are defined for an
arbitrary Lie group as eigenstates of elements of the corresponding complex Lie
algebra. We show that this concept unifies different definitions of coherent
states associated with a dynamical symmetry group. On the one hand, algebra
eigenstates include different sets of Perelomov's generalized coherent states.
On the other hand, intelligent states (which are squeezed states for a system
of general symmetry) also form a subset of algebra eigenstates. We develop the
general formalism and apply it to the SU(2) and SU(1,1) simple Lie groups.
Complete solutions to the general eigenvalue problem are found in the both
cases, by a method that employs analytic representations of the algebra
eigenstates. This analytic method also enables us to obtain exact closed
expressions for quantum statistical properties of an arbitrary algebra
eigenstate. Important special cases such as standard coherent states and
intelligent states are examined and relations between them are studied by using
their analytic representations.Comment: LaTeX, 24 pages, 1 figure (compressed PostScript, available at
http://www.technion.ac.il/~brif/abstracts/AES.html ). More information on
http://www.technion.ac.il/~brif/science.htm
Interpolating Coherent States for Heisenberg-Weyl and Single-Photon SU(1,1) Algebras
New quantal states which interpolate between the coherent states of the
Heisenberg_Weyl and SU(1,1) algebras are introduced. The interpolating states
are obtained as the coherent states of a closed and symmetric algebra which
interpolates between the two algebras. The overcompleteness of the
interpolating coherent states is established. Differential operator
representations in suitable spaces of entire functions are given for the
generators of the algebra. A nonsymmetric set of operators to realize the
Heisenberg-Weyl algebra is provided and the relevant coherent states are
studied.Comment: 13 pages nd 5 ps figure
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