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n_TOF Collaboration(Zugec, P. et al), Domingo-Pardo, C., Giubrone, G., & Tain, J. L. (2016). Integral measurement of the C-12(n, p)B-12 reaction up to 10 GeV. Eur. Phys. J. A, 52(4), 101–13pp.
Abstract: The integral measurement of the C-12(n, p)B-12 reaction was performed at the neutron time-of-flight facility nTOF at CERN. The total number of B-12 nuclei produced per neutron pulse of the nTOF beam was determined using the activation technique in combination with a time-of-flight technique. The cross section is integrated over the n_TOF neutron energy spectrum from reaction threshold at 13.6 MeV to 10 GeV. Having been measured up to 1 GeV on basis of the U-235(n, f) reaction, the neutron energy spectrum above 200 MeV has been re-evaluated due to the recent extension of the cross section reference for this particular reaction, which is otherwise considered a standard up to 200 MeV. The results from the dedicated GEANT4 simulations have been used to evaluate the neutron flux from 1 GeV up to 10 GeV. The experimental results related to the C-12(n, p)B-12 reaction are compared with the evaluated cross sections from major libraries and with the predictions of different GEANT4 models, which mostly underestimate the B-12 production. On the contrary, a good reproduction of the integral cross section derived from measurements is obtained with TALYS-1.6 calculations, with optimized parameters.
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Aguilar, A. C., Binosi, D., Figueiredo, C. T., & Papavassiliou, J. (2016). Unified description of seagull cancellations and infrared finiteness of gluon propagators. Phys. Rev. D, 94(4), 045002–22pp.
Abstract: We present a generalized theoretical framework for dealing with the important issue of dynamical mass generation in Yang-Mills theories, and, in particular, with the infrared finiteness of the gluon propagators, observed in a multitude of recent lattice simulations. Our analysis is manifestly gauge invariant, in the sense that it preserves the transversality of the gluon self-energy, and gauge independent, given that the conclusions do not depend on the choice of the gauge-fixing parameter within the linear covariant gauges. The central construction relies crucially on the subtle interplay between the Abelian Ward identities satisfied by the nonperturbative vertices and a special integral identity that enforces a vast number of “seagull cancellations” among the one-and two-loop dressed diagrams of the gluon Schwinger-Dyson equation. The key result of these considerations is that the gluon propagator remains rigorously massless, provided that the vertices do not contain (dynamical) massless poles. When such poles are incorporated into the vertices, under the pivotal requirement of respecting the gauge symmetry of the theory, the terms comprising the Ward identities conspire in such a way as to still enforce the total annihilation of all quadratic divergences, inducing, at the same time, residual contributions that account for the saturation of gluon propagators in the deep infrared.
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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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Orrigo, S. E. A. et al, Rubio, B., Gelletly, W., Agramunt, J., Algora, A., & Molina, F. (2016). Observation of the 2(+) isomer in Co-52. Phys. Rev. C, 94(4), 044315–8pp.
Abstract: We report the first observation of the 2(+) isomer in Co-52, produced in the beta decay of the 0(+), Ni-52 ground state. We have observed three. rays at 849, 1910, and 5185 keV characterizing the beta de-excitation of the isomer. We have measured a half-life of 102(6) ms for the isomeric state. The Fermi and Gamow-Teller transition strengths for the beta decay of Co-52m to Fe-52 have been determined. We also add new information on the beta decay of the 6(+), Co-52 ground state, for which we have measured a half-life of 112(3) ms.
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XENON Collaboration(Aprile, E. et al), & Orrigo, S. E. A. (2016). Physics reach of the XENON1T dark matter experiment. J. Cosmol. Astropart. Phys., 04(4), 027–37pp.
Abstract: The XENON1T experiment is currently in the commissioning phase at the Laboratori Nazionali del Gran Sasso, Italy. In this article we study the experiment's expected sensitivity to the spin-independent WIMP-nucleon interaction cross section, based on Monte Carlo predictions of the electronic and nuclear recoil backgrounds. The total electronic recoil background in 1 tonne fiducial volume and (1, 12) keV electronic recoil equivalent energy region, before applying any selection to discriminate between electronic and nuclear recoils, is (1.80+/-0.15) . 10(-4) (kg.day.keV)(-1), mainly due to the decay of Rn-222 daughters inside the xenon target. The nuclear recoil background in the corresponding nuclear recoil equivalent energy region (4, 50) keV, is composed of (0.6 +/- 0.1) (t.y)(-1) from radiogenic neutrons, (1.8+/-0.3) . 10(-2) (t.y)(-1) from coherent scattering of neutrinos, and less than 0.01 (t.y)(-1) from muon-induced neutrons. The sensitivity of XENON1T is calculated with the Pro file Likelihood Ratio method, after converting the deposited energy of electronic and nuclear recoils into the scintillation and ionization signals seen in the detector. We take into account the systematic uncertainties on the photon and electron emission model, and on the estimation of the backgrounds, treated as nuisance parameters. The main contribution comes from the relative scintillation efficiency L-eff, which affects both the signal from WIMPs and the nuclear recoil backgrounds. After a 2 y measurement in 1 tonne fiducial volume, the sensitivity reaches a minimum cross section of 1.6 . 10(-47) cm(2) at m(chi) = 50 GeV/c(2).
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