Pion and Kaon Masses and Pion Form Factors from Dynamical Chiral-Symmetry Breaking with Light Constituent Quarks

Light constituent quark masses and the corresponding dynamical quark masses are determined by data, the quark-level linear sigma model, and infrared QCD. This allows to define effective nonstrange and strange current quark masses, which reproduce the experimental pion and kaon masses very accurately, by simple additivity. In contrast, the usual nonstrange and strange current quarks employed by the Particle Data Group and Chiral Perturbation Theory do not allow a straightforward quantitative explanation of the pion and kaon masses.Comment: 4 pages, AIP style, contribution to conference ``Quark Confinement and the Hadron Spectrum VII'', Azores, Portugal, 2-7 September 200

Analysis of total urinary catecholamines by liquid chromatography: methodology, routine experience and clinical interpretations of results

A simple routine method is described for simultaneous assay of total urinary adrenaline, noradrenaline and dopamine. The catecholamines are pre-purified on a small ion-exchange column, separated by reversed phase ion-pair liquid chromatography, and are quantitated by electrochemical detection. The method was routinely applied to 422 urines. Elevated values were found in four urine specimens obtained from patients with histologically proven phaeochromocytomas. Virtually no interference by endogenous or exogenous compounds was found. Values for urinary catecholamines determined by fluorimetric analysis agreed with those obtained by high pressure liquid chromatography with electrochemical detection. Within-day CVs for the compounds ranged from 5.2-11.9%, between-day CVs from 3.3-6.6%. The normal range (95% confidence level) was 20-230 micrograms/24 h for noradrenaline and 1-35 micrograms/24 h for adrenaline

Comment on "Two-photon decay of the sigma meson"

We comment on a recent paper by Giacosa, Gutsche, and Lyobovitskij, in which it is argued that a quarkonium interpretation of the $\sigma$ meson should give rise to a much smaller two-photon decay width than commonly assumed. The reason for this claimed discrepancy is a term in the transition amplitude, necessary for gauge invariance, which allegedly is often omitted in the literature, including the work of the present authors. Here we show their claims to be incorrect by demonstrating, in the context of the Quark-Level Linear $\sigma$ Model, that the recently extracted experimental value $\Gamma_{\sigma\to2\gamma}=(4.1\pm0.3)$ keV is compatible with a $q\bar{q}$ assignment for the $\sigma$, provided that meson loops are taken into account as well.Comment: RevTeX, 4 pages, Comment on Phys. Rev. D 77 (2008) 034007 [0710.3403 [hep-ph]

Nanometer-Resolved Collective Micromeniscus Oscillations through Optical Diffraction

We study the dynamics of periodic arrays of micrometer-sized liquid-gas menisci formed at superhydrophobic surfaces immersed into water. By measuring the intensity of optical diffraction peaks in real time we are able to resolve nanometer scale oscillations of the menisci with sub-microsecond time resolution. Upon driving the system with an ultrasound field at variable frequency we observe a pronounced resonance at a few hundred kHz, depending on the exact geometry. Modeling the system using the unsteady Stokes equation, we find that this low resonance frequency is caused by a collective mode of the acoustically coupled oscillating menisci.Comment: 4 pages, 5 figure

Mezonski faktori oblika u linearnom σ modelu na kvarkovskoj razini

The quark-level linear σ model (LσM) is employed to compute a variety of electromagnetic and weak observables of light mesons, including pion and kaon form factors and charge radii, charged-pion polarizabilities, semileptonic weak Kℓ3 decay, semileptonic weak radiative pion and kaon form factors, radiative decays of vector mesons, and nonleptonic weak K2π decay. The agreement of all these predicted observables with experiment is striking. In passing, the tight link between the LσM and vector-meson dominance is shown. Some conclusions are drawn on the LσM in connection with lattice and renormalization-group approaches to QCD.Primjenjujemo linearni σ model (LσM) na kvarkovskoj razini za računanje niza elektromagnetskih i slabih veličina za lake mezone, kao što su pionski i kaonski faktori oblika i nabojski polumjeri, polarizivost nabijenih piona, poluleptonski slab Kℓ3 raspad, poluleptonski slabi radijativni pionski i kaonski faktori oblika, radijativni raspadi vektorskih mezona i neleptonski slabi raspadi K2π. Slaganje svih predviđanja s ishodima mjerenja je izvanredno. Usput, pokazujemo blisku vezu LσM sa prevladavanjem vektorskih mezona. Izvodima neke zaključke o LσM u odnosu na pristupe QCDu s rešetkama i renormalizacijskom grupom