Weak radiative hyperon decays, Hara's theorem and the diquark

Weak radiative hyperon decays are discussed in the diquark-level approach. It is pointed out that in the general diquark formalism one may reproduce the experimentally suggested pattern of asymmetries, while maintaining Hara's theorem in the SU(3) limit. At present, however, no detailed quark-based model of parity-violating diquark-photon coupling exists that would have the necessary properties.Comment: 10 pages, LaTe

Comment on "Hara's theorem in the constituent quark model"

It is pointed out that current conservation alone does not suffice to prove Hara's theorem as it was claimed recently. By explicit calculation we show that the additional implicit assumption made in such "proofs" is that of a sufficiently localized current.Comment: 8 pages, Late

No self-similar aggregates with sedimentation

Two-dimensional cluster-cluster aggregation is studied when clusters move both diffusively and sediment with a size dependent velocity. Sedimentation breaks the rotational symmetry and the ensuing clusters are not self-similar fractals: the mean cluster width perpendicular to the field direction grows faster than the height. The mean width exhibits power-law scaling with respect to the cluster size, ~ s^{l_x}, l_x = 0.61 +- 0.01, but the mean height does not. The clusters tend to become elongated in the sedimentation direction and the ratio of the single particle sedimentation velocity to single particle diffusivity controls the degree of orientation. These results are obtained using a simulation method, which becomes the more efficient the larger the moving clusters are.Comment: 10 pages, 10 figure

GDR Feeding of the Highly-Deformed Band in 42Ca

The gamma-ray spectra from the decay of the GDR in the compound nucleus reaction 18O+28Si at bombarding energy of 105 MeV have been measured in an experiment using the EUROBALL IV and HECTOR arrays. The obtained experimental GDR strength function is highly fragmented, with a low energy (10 MeV) component, indicating a presence of a large deformation and Coriolis effects. In addition, the preferential feeding of the highly-deformed band in 42Ca by this GDR low energy component is observed.Comment: 6 pages, 2 figures, Proceedings of the Zakopane2004 Symposium, to be published in Acta Phys. Pol. B36 (2005

Block-Diagonalization and f-electron Effects in Tight-Binding Theory

We extend a tight-binding total energy method to include f-electrons, and apply it to the study of the structural and elastic properties of a range of elements from Be to U. We find that the tight-binding parameters are as accurate and transferable for f-electron systems as they are for d-electron systems. In both cases we have found it essential to take great care in constraining the fitting procedure by using a block-diagonalization procedure, which we describe in detail.Comment: 9 pages, 6 figure

Somatic mosaicism of an intragenic FANCB duplication in both fibroblast and peripheral blood cells observed in a Fanconi anemia patient leads to milder phenotype

© 2017 The Authors. Molecular Genetics & Genomic Medicine published by Wiley Periodicals, Inc. Background: Fanconi anemia (FA) is a rare disorder characterized by congenital malformations, progressive bone marrow failure, and predisposition to cancer. Patients harboring X-linked FANCB pathogenic variants usually present with severe congenital malformations resembling VACTERL syndrome with hydrocephalus. Methods: We employed the diepoxybutane (DEB) test for FA diagnosis, arrayCGH for detection of duplication, targeted capture and next-gen sequencing for defining the duplication breakpoint, PacBio sequencing of full-length FANCB aberrant transcript, FANCD2 ubiquitination and foci formation assays for the evaluation of FANCB protein function by viral transduction of FANCB- cells with lentiviral FANCB WT and mutant expression constructs, and droplet digital PCR for quantitation of the duplication in the genomic DNA and cDNA. Results: We describe here an FA-B patient with a mild phenotype. The DEB diagnostic test for FA revealed somatic mosaicism. We identified a 9154 bp intragenic duplication in FANCB, covering the first coding exon 3 and the flanking regions. A four bp homology (GTAG) present at both ends of the breakpoint is consistent with microhomology-mediated duplication mechanism. The duplicated allele gives rise to an aberrant transcript containing exon 3 duplication, predicted to introduce a stop codon in FANCB protein (p.A319*). Duplication levels in the peripheral blood DNA declined from 93% to 7.9% in the span of eleven years. Moreover, the patient fibroblasts have shown 8% of wild-type (WT) allele and his carrier mother showed higher than expected levels of WT allele (79% vs. 50%) in peripheral blood, suggesting that the duplication was highly unstable. Conclusion: Unlike sequence point variants, intragenic duplications are difficult to precisely define, accurately quantify, and may be very unstable, challenging the proper diagnosis. The reversion of genomic duplication to the WT allele results in somatic mosaicism and may explain the relatively milder phenotype displayed by the FA-B patient described here

Long Distance Contribution to s→dγs \to d\gamma and Implications for Ω−→Ξ−γ,Bs→Bd∗γ\Omega^-\to \Xi ^-\gamma, B_s \to B_d^*\gamma and b→sγb \to s\gamma

We estimate the long distance (LD) contribution to the magnetic part of the $s \to d\gamma$ transition using the Vector Meson Dominance approximation $(V=\rho,\omega,\psi_i)$. We find that this contribution may be significantly larger than the short distance (SD) contribution to $s \to d\gamma$ and could possibly saturate the present experimental upper bound on the $\Omega^-\to \Xi^-\gamma$ decay rate, $\Gamma^{\rm MAX}_{\Omega^-\to \Xi^-\gamma} \simeq 3.7\times10^{-9}$eV. For the decay $B_s \to B^*_d\gamma$, which is driven by $s \to d\gamma$ as well, we obtain an upper bound on the branching ratio $BR(B_s \to B_d^*\gamma)<3\times10^{-8}$ from $\Gamma^{\rm MAX}_{\Omega^-\to \Xi^-\gamma}$. Barring the possibility that the Quantum Chromodynamics coefficient $a_2(m_s)$ be much smaller than 1, $\Gamma^{\rm MAX}_{\Omega^-\to \Xi^-\gamma}$ also implies the approximate relation $\frac{2}{3} \sum_i \frac{g^2_{\psi_i}(0)}{m^2_{\psi_i}} \simeq \frac{1}{2} \frac{g^2_\rho(0)}{m^2_\rho} + \frac{1}{6}\frac{g^2_\omega(0)}{m^2_\omega}$. This relation agrees quantitatively with a recent independent estimate of the l.h.s. by Deshpande et al., confirming that the LD contributions to $b \to s\gamma$ are small. We find that these amount to an increase of $(4\pm2)\%$ in the magnitude of the $b \to s \gamma$ transition amplitude, relative to the SD contribution alone.Comment: 16 pages, LaTeX fil

Hara's Theorem and W-exchange in Hyperon Weak Radiative Decays

We reconsider Hara's theorem in its relation to the well-known properties of beta-decay. All assumptions necessary for the theorem to be true are explicitly formulated. Further, we study the W-exchange contribution to weak radiative decays and show that it does not violate Hara's theorem. However, this contribution reveals the essential role of particle mixing in symmetry considerations and some peculiar features of gauge-invariant amplitudes under perturbative expansion. Together they explain an effect, which was treated as contradicting Hara's theorem, without any violation. The properties of W-exchange we describe here may have more general importance and should be taken into account in further detailed calculations of weak processes.Comment: 14 pages, LATEX, no figure

A QCD Sum Rule Approach to the s→dγs\to d\gamma Contribution to the Ω−→Ξ−γ\Omega^-\to \Xi^-\gamma Radiative Decay

QCD sum rules are used to calculate the contribution of short-distance single-quark transition $s\rightarrow d \gamma$, to the amplitudes of the hyperon radiative decay, $\Omega^-\rightarrow \Xi^-\gamma$. We re-evaluate the Wilson coefficient of the effective operator responsible for this transition. We obtain a branching ratio which is comparable to the unitarity limit.Comment: 15 pages, Revtex, 13 figures available as a uuencoded, gz-compressed ps fil