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Garcilazo, H., Valcarce, A., & Vijande, J. (2016). Maximal isospin few-body systems of nucleons and Xi hyperons. Phys. Rev. C, 94(2), 024002–3pp.
Abstract: By using local central Yukawa-type interactions that reproduce the low-energy parameters of the latest updates of the Nijmegen ESC08c potentials, we show that the N Xi, NN Xi, N Xi Xi, and NN Xi Xi systems with maximal isospin are bound. Since in these states the strong decay N Xi -> Lambda Lambda is forbidden by isospin conservation, these strange few-body systems will be stable under the strong interaction. These results may suggest that other states with different number of Ns and Xi s in the maximal isospin channel could also be bound.
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Garcilazo, H., Valcarce, A., & Vijande, J. (2016). Doubly heavy baryon spectra guided by lattice QCD. Phys. Rev. D, 94(7), 074003–8pp.
Abstract: This paper provides results for the ground state and excited spectra of three-flavored doubly heavy baryons, bcn and bcs. We take advantage of the spin-independent interaction recently obtained to reconcile the lattice SU(3) QCD static potential and the results of nonperturbative lattice QCD for the triply heavy baryon spectra. We show that the spin-dependent potential might be constrained on the basis of nonperturbative lattice QCD results for the spin splittings of three-flavored doubly heavy baryons. Our results may also represent a challenge for future lattice QCD work, because a smaller lattice error could help in distinguishing between different prescriptions for the spin-dependent part of the interaction. Thus, by comparing with the reported baryon spectra obtained with parameters estimated from lattice QCD, one can challenge the precision of lattice calculations. The present work supports a coherent description of singly, doubly and triply heavy baryons with the same Cornell-like interacting potential. The possible experimental measurement of these states at LHCb is an incentive for this study.
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Gimenez-Alventosa, V., Vijande, J., Ballester, F., & Perez-Calatayud, J. (2016). Transit dose comparisons for Co-60 and Ir-192 HDR sources. J. Radiol. Prot., 36(4), 858–864.
Abstract: The goal of this study is to evaluate the ambient dose due to the transit of high dose rate (HDR) Co-60 sources along a transfer tube as compared to Ir-192 ones in a realistic clinical scenario. This goal is accomplished by evaluating air-kerma differences with Monte Carlo calculations using PENELOPE2011. Scatter from both the afterloader and the patient was not taken into account. Two sources, mHDR-v2 and Flexisource Co-60, (Elekta Brachytherapy, Veenendaal, the Netherlands) have been considered. These sources were simulated within a standard transfer tube located in an infinite air phantom. The movement of the source was included by displacing their positions along the connecting tube from z = – 75 cm to z = + 75 cm and combining them. Since modern afterloaders like Flexitron (Elekta) or Saginova (BEBIG GmbH) are able to use equally 192Ir and 60Co sources, it was assumed that both sources are displaced with equal speed. Typical HDR source activity content values were provided by the manufacturer. 2D distributions were obtained with type-A uncertainties (k = 2) less than 0.01%. From those, the air-kerma ratio Co-60/Ir-192 was evaluated weighted by their corresponding typical activities. It was found that it varies slowly with distance (less than 10% variation at 75 cm) but strongly in time due to the shorter half-life of the 192Ir (73.83 d). The maximum ratio is located close to the tube. It reaches a value of 0.57 when the typical activity of the sources at the time when they were installed by the vendor was used. Such ratio increases up to 1.28 at the end of the recommended working life (90 d) of the Ir-192 source. Co-60/Ir-192 air-kerma ratios are almost constant (0.51-0.57) in the vicinity of the source-tube with recent installed sources. Nevertheless, air-kerma ratios increase rapidly (1.15-1.29) whenever the Ir-192 is approaching the end of its life. In case of a medical event requiring the medical staff to access the treatment room, these ratios indicate that the dosimetric impact on the medical team will be lower, with a few exceptions, in the case of Co-60-based HDR brachytherapy as compared to Ir-192-based one when typical air-kerma strength values are considered.
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Vijande, J., Valcarce, A., & Garcilazo, H. (2015). Constituent-quark model description of triply heavy baryon nonperturbative lattice QCD data. Phys. Rev. D, 91(5), 054011–7pp.
Abstract: This paper provides results for the spectra of triply charmed and bottom baryons based on a constituent-quark model approach. We take advantage of the assumption that potential models are expected to describe triply heavy baryons to a similar degree of accuracy as the successful results obtained in the charmonium and bottomonium sectors. The high precision calculation of the ground state and positive and negative parity excited states recently reported by nonperturbative lattice QCD provides us with a unique opportunity to confront model predictions with the data. This comparison may also help to build a bridge between two difficult to reconcile lattice QCD results, namely, the lattice SU(3) QCD static three-quark potential and the recent results of nonperturbative lattice QCD for the triply heavy baryon spectra.
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Hueso-Gonzalez, F., Vijande, J., Ballester, F., Perez-Calatayud, J., & Siebert, F. A. (2015). A simple analytical method for heterogeneity corrections in low dose rate prostate brachytherapy. Phys. Med. Biol., 60(14), 5455–5469.
Abstract: In low energy brachytherapy, the presence of tissue heterogeneities contributes significantly to the discrepancies observed between treatment plan and delivered dose. In this work, we present a simplified analytical dose calculation algorithm for heterogeneous tissue. We compare it with Monte Carlo computations and assess its suitability for integration in clinical treatment planning systems. The algorithm, named as RayStretch, is based on the classic equivalent path length method and TG-43 reference data. Analytical and Monte Carlo dose calculations using Penelope2008 are compared for a benchmark case: a prostate patient with calcifications. The results show a remarkable agreement between simulation and algorithm, the latter having, in addition, a high calculation speed. The proposed analytical model is compatible with clinical real-time treatment planning systems based on TG-43 consensus datasets for improving dose calculation and treatment quality in heterogeneous tissue. Moreover, the algorithm is applicable for any type of heterogeneities.
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