Application of Current Algebra in Three Pseudoscalar Meson Decays of τ\tau Lepton

The decays of $\tau \to 3\pi \nu$ and $\tau \to \pi K^{*} \nu, K\rho \nu$ are calculated using the hard pion and kaon current algebra and assuming the Axial-Vector meson dominance of the hadronic axial currents. Using the experimental data on their masses and widths, the $\tau$ decay branching ratios into these channels are calculated and found to be in a reasonable agreement with the experimental data. In particular, using the available Aleph data on the $3\pi$ spectrum, we determine the $A_1$ parameters, $m_A=1.24\pm 0.02 GeV$, $\Gamma _A=0.43\pm 0.02$ GeV; the hard current algebra calculation yields a $3\pi$ branching ratio of $19 \pm 3 \%$.Comment: 14 pages, Tex, 6 included figure

τ→πKν\tau \to \pi K \nu Decay and πK\pi K Scattering

Using chiral low energy theorems and elastic unitarity assumption, the $\tau\to\pi K \nu$ decay is investigated. The vector and scalar $\pi K$ form factors are calculated. It is found that the $\pi K$ spectrum is dominated by the $K^*$ resonance. By measuring the forward-backward asymmetry, it is shown that the S wave $\pi K$ phase shift can be determined near the $K^{*}$ resonance region. The calculated branching ratio and resonance parameters are in good agreement with experiments.Comment: 15 pages, Tex, 6 included figure

Tau Decays and Chiral Perturbation Theory

In a small window of phase space, chiral perturbation theory can be used to make standard model predictions for tau decays into two and three pions. For $\tau \to 2\pi \nu_\tau$, we give the analytical result for the relevant form factor $F_V$ up to two loops, then calculate the differential spectrum and compare with available data. For $\tau \to 3 \pi \nu_\tau$, we have calculated the hadronic matrix element to one loop. We discuss the decomposition of the three pion states into partition states and we give detailed predictions for the decay in terms of structure functions. We also compare with low energy predictions of meson dominance models. Overall, we find good agreement, but also some interesting discrepancies, which might have consequences beyond the limit of validity of chiral perturbation theory.Comment: 39 pages, Latex, including 8 Postscript figures. The complete paper is also available via anonymous ftp at ftp://www-ttp.physik.uni-karlsruhe.de/ , or via www at http://www-ttp.physik.uni-karlsruhe.de/cgi-bin/preprint

Unitarity, Chiral Perturbation Theory, and Meson Form Factors

The inverse-amplitude method is applied to the one-loop chiral expansion of the pion, kaon, and $K_{l3}$ form factors. Since these form factors are determined by the same chiral low-energy constants, it is possible to obtain finite predictions for the inverse-amplitude method. It is shown that this method clearly improves one-loop chiral perturbation theory, and a very good agreement between the inverse-amplitude method and the experimental information is obtained. This suggests that the inverse-amplitude method is a rather systematic way of improving chiral perturbation theory.Comment: 15 pages, 5 figs, uses REVTeX and epsfig.st

Structural, magnetic, and optical studies of the polymorphic 9′-anthracenyl dithiadiazolyl radical

The fluorescent 9′-anthracenyl-functionalized dithiadiazolyl radical (3) exhibits four structurally determined crystalline phases, all of which are monomeric in the solid state. Polymorph 3α (monoclinic P21/c, Z′ = 2) is isolated when the radical is condensed onto a cold substrate (enthalpically favored polymorph), whereas 3β (orthorhombic P212121, Z′ = 3) is collected on a warm substrate (entropically favored polymorph). The α and β polymorphs exhibit chemically distinct structures with 3α exhibiting face-to-face π–π interactions between anthracenyl groups, while 3β exhibits edge-to-face π–π interactions. 3α undergoes an irreversible conversion to 3β on warming to 120 °C (393 K). The β-phase undergoes a series of reversible solid-state transformations on cooling; below 300 K a phase transition occurs to form 3γ (monoclinic P21/c, Z′ = 1), and on further cooling below 165 K, a further transition is observed to 3δ (monoclinic P21/n, Z′ = 2). Both 3β → 3γ and 3γ → 3δ transitions are reversible (single-crystal X-ray diffraction), and the 3γ → 3δ process exhibits thermal hysteresis with a clear feature observed by heat capacity measurements. Heating 3β above 160 °C generates a fifth polymorph (3ε) which is distinct from 3α–3δ based on powder X-ray diffraction data. The magnetic behavior of both 3α and the 3β/3γ/3δ system reflect an S = 1/2 paramagnet with weak antiferromagnetic coupling. The reversible 3δ ↔ 3γ phase transition exhibits thermal hysteresis of 20 K. Below 50 K, the value of χmT for 3δ approaches 0 emu·K·mol–1 consistent with formation of a gapped state with an S = 0 ground-state configuration. In solution, both paramagnetic 3 and diamagnetic [3][GaCl4] exhibit similar absorption and emission profiles reflecting similar absorption and emission mechanisms for paramagnetic and diamagnetic forms. Both emit in the deep-blue region of the visible spectrum (λem ∼ 440 nm) upon excitation at 255 nm with quantum yields of 4% (3) and 30% ([3][GaCl4]) affording a switching ratio [ΦF(3+)/ΦF(3)] of 7.5 in quantum efficiency with oxidation state. Solid-state films of both 3 and [3][GaCl4] exhibit emission bands at a longer wavelength (490 nm) attributed to excimer emission.We would like to thank the Canada Research Chairs Program for financial support (J.M.R.) and the University of Windsor for a scholarship (Y.B.). E.G. and M.P. would like to thank NSERC. A.A. and J.C. acknowledge support from grant MAT2015-68200-C2−2-P from the Ministerio de Economía y Competividad of Spain and the European Regional Development Fund. Additional support from Diputacion General de Aragon (DGA-M4) is also acknowledged.Peer reviewe

Influence of the Hypersensitivity to Low Dose Phenomenon on the Tumor Response to Hypofractionated Stereotactic Body Radiation Therapy.

Stereotactic body radiation therapy (SBRT) has made the hypofractionation of high doses delivered in a few sessions more acceptable. While the benefits of hypofractionated SBRT have been attributed to additional vascular, immune effects, or specific cell deaths, a radiobiological and mechanistic model is still needed. By considering each session of SBRT, the dose is divided into hundreds of minibeams delivering some fractions of Gy. In such a dose range, the hypersensitivity to low dose (HRS) phenomenon can occur. HRS produces a biological effect equivalent to that produced by a dose 5-to-10 times higher. To examine whether HRS could contribute to enhancing radiation effects under SBRT conditions, we exposed tumor cells of different HRS statuses to SBRT. Four human HRS-positive and two HRS-negative tumor cell lines were exposed to different dose delivery modes: a single dose of 0.2 Gy, 2 Gy, 10 × 0.2 Gy, and a single dose of 2 Gy using a non-coplanar isocentric minibeams irradiation mode were delivered. Anti-γH2AX immunofluorescence, assessing DNA double-strand breaks (DSB), was applied. In the HRS-positive cells, the DSB produced by 10 × 0.2 Gy and 2 Gy, delivered by tens of minibeams, appeared to be more severe, and they provided more highly damaged cells than in the HRS-negative cells, suggesting that more severe DSB are induced in the "SBRT modes" conditions when HRS occurs in tumor. Each SBRT session can be viewed as hyperfractionated dose delivery by means of hundreds of low dose minibeams. Under current SBRT conditions (i.e., low dose per minibeam and not using ultra-high dose-rate), the response of HRS-positive tumors to SBRT may be enhanced significantly. Interestingly, similar conclusions were reached with HRS-positive and HRS-negative untransformed fibroblast cell lines, suggesting that the HRS phenomenon may also impact the risk of post-RT tissue overreactions