n_TOF Collaboration(Barbagallo, M. et al), Domingo-Pardo, C., & Tain, J. L. (2018). Experimental setup and procedure for the measurement of the Be-7(n,p)Li-7 reaction at n_TOF. Nucl. Instrum. Methods Phys. Res. A, 887, 27–33.
Abstract: Following the completion of the second neutron beam line and the related experimental area (EAR2) at the n_TOF spallation neutron source at CERN, several experiments were planned and performed. The high instantaneous neutron flux available in EAR2 allows to investigate neutron induced reactions with charged particles in the exit channel even employing targets made out of small amounts of short-lived radioactive isotopes. After the successful measurement of the Be-7(n,alpha)alpha cross section, the Be-7(n,p)Li-7 reaction was studied in order to provide still missing cross section data of relevance for Big Bang Nucleosynthesis (BBN), in an attempt to find a solution to the cosmological Lithium abundance problem. This paper describes the experimental setup employed in such a measurement and its characterization.
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n_TOF Collaboration(Praena, J. et al), Domingo-Pardo, C., Giubrone, G., Tain, J. L., & Tarifeño-Saldivia, A. (2018). Preparation and characterization of S-33 samples for S-33(n,alpha)Si-30 cross-section measurements at the n_TOF facility at CERN. Nucl. Instrum. Methods Phys. Res. A, 890, 142–147.
Abstract: Thin S-33 samples for the study of the S-33(n,alpha)Si-30 cross-section at the n_TOF facility at CERN were made by thermal evaporation of S-33 powder onto a dedicated substrate made of kapton covered with thin layers of copper, chromium and titanium. This method has provided for the first time bare sulfur samples a few centimeters in diameter. The samples have shown an excellent adherence with no mass loss after few years and no sublimation in vacuum at room temperature. The determination of the mass thickness of S-33 has been performed by means of Rutherford backscattering spectrometry. The samples have been successfully tested under neutron irradiation.
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BRIKEN Collaboration(Tolosa-Delgado, A. et al), Agramunt, J., Tain, J. L., Algora, A., Domingo-Pardo, C., Morales, A. I., et al. (2019). Commissioning of the BRIKEN detector for the measurement of very exotic beta-delayed neutron emitters. Nucl. Instrum. Methods Phys. Res. A, 925, 133–147.
Abstract: A new detection system has been installed at the RIKEN Nishina Center (Japan) to investigate decay properties of very neutron-rich nuclei. The setup consists of three main parts: a moderated neutron counter, a detection system sensitive to the implantation and decay of radioactive ions, and gamma-ray detectors. We describe here the setup, the commissioning experiment and some selected results demonstrating its performance for the measurement of half-lives and beta-delayed neutron emission probabilities. The methodology followed in the analysis of the data is described in detail. Particular emphasis is placed on the correction of the accidental neutron background.
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Babiano, V., Caballero, L., Calvo, D., Ladarescu, I., Olleros, P., & Domingo-Pardo, C. (2019). gamma-Ray position reconstruction in large monolithic LaCl3(Ce) crystals with SiPM readout. Nucl. Instrum. Methods Phys. Res. A, 931, 1–22.
Abstract: We report on the spatial response characterization of large LaCl3(Ce) monolithic crystals optically coupled to 8 x 8 pixel silicon photomultiplier (SiPM) sensors. A systematic study has been carried out for 511 keV gamma-rays using three different crystal thicknesses of 10 mm, 20 mm and 30 mm, all of them with planar geometry and a base size of 50 x 50 mm(2). In this work we investigate and compare two different approaches for the determination of the main gamma-ray hit location. On one hand, methods based on the fit of an analytical model for the scintillation light distribution provide the best results in terms of linearity and field of view, with spatial resolutions close to similar to 1 mm FWHM. On the other hand, position reconstruction techniques based on neural networks provide similar linearity and field-of-view, becoming the attainable spatial resolution similar to 3 mm FWHM. For the third space coordinate z or depth-of-interaction we have implemented an inverse linear calibration approach based on the cross-section of the measured scintillation-light distribution at a certain height. The detectors characterized in this work are intended for the development of so-called Total Energy Detectors with Compton imaging capability (i-TED), aimed at enhanced sensitivity and selectivity measurements of neutron capture cross sections via the time-of-flight (TOF) technique.
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Babiano, V., Balibrea, J., Caballero, L., Calvo, D., Ladarescu, I., Mira Prats, S., et al. (2020). First i-TED demonstrator: A Compton imager with Dynamic Electronic Collimation. Nucl. Instrum. Methods Phys. Res. A, 953, 163228–9pp.
Abstract: i-TED consists of both a total energy detector and a Compton camera primarily intended for the measurement of neutron capture cross sections by means of the simultaneous combination of neutron time-of-flight (TOF) and gamma-ray imaging techniques. TOF allows one to obtain a neutron-energy differential capture yield, whereas the imaging capability is intended for the discrimination of radiative background sources, that have a spatial origin different from that of the capture sample under investigation. A distinctive feature of i-TED is the embedded Dynamic Electronic Collimation (DEC) concept, which allows for a trade-off between efficiency and image resolution. Here we report on some general design considerations and first performance characterization measurements made with an i-TED demonstrator in order to explore its gamma-ray detection and imaging capabilities.
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Alidra, M. et al, & Torro Pastor, E. (2021). The MATHUSLA test stand. Nucl. Instrum. Methods Phys. Res. A, 985, 164661–9pp.
Abstract: The rate of muons from LHC pp collisions reaching the surface above the ATLAS interaction point is measured as a function of the ATLAS luminosity and compared with expected rates from decays of W and Z bosons and b- and c-quark jets. In addition, data collected during periods without beams circulating in the LHC provide a measurement of the background from cosmic ray inelastic backscattering that is compared to simulation predictions. Data were recorded during 2018 in a 2.5 x 2.5 x 6.5 m(3) active volume MATHUSLA test stand detector unit consisting of two scintillator planes, one at the top and one at the bottom, which defined the trigger, and six layers of RPCs between them, grouped into three (x, y)-measuring layers separated by 1.74 m from each other. Triggers selecting both upward-going tracks and downward-going tracks were used.
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Balibrea-Correa, J., Lerendegui-Marco, J., Babiano-Suarez, V., Caballero, L., Calvo, D., Ladarescu, I., et al. (2021). Machine Learning aided 3D-position reconstruction in large LaCl3 crystals. Nucl. Instrum. Methods Phys. Res. A, 1001, 165249–17pp.
Abstract: We investigate five different models to reconstruct the 3D gamma-ray hit coordinates in five large LaCl3(Ce) monolithic crystals optically coupled to pixelated silicon photomultipliers. These scintillators have a base surface of 50 x 50 mm(2) and five different thicknesses, from 10 mm to 30 mm. Four of these models are analytical prescriptions and one is based on a Convolutional Neural Network. Average resolutions close to 1-2 mm fwhm are obtained in the transverse crystal plane for crystal thicknesses between 10 mm and 20 mm using analytical models. For thicker crystals average resolutions of about 3-5 mm fwhm are obtained. Depth of interaction resolutions between 1 mm and 4 mm are achieved depending on the distance of the interaction point to the photosensor surface. We propose a Machine Learning algorithm to correct for linearity distortions and pin-cushion effects. The latter allows one to keep a large field of view of about 70%-80% of the crystal surface, regardless of crystal thickness. This work is aimed at optimizing the performance of the so-called Total Energy Detector with Compton imaging capability (i-TED) for time-of-flight neutron capture cross-section measurements.
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Barrientos, L., Borja-Lloret, M., Etxebeste, A., Muñoz, E., Oliver, J. F., Ros, A., et al. (2021). Performance evaluation of MACACO II Compton camera. Nucl. Instrum. Methods Phys. Res. A, 1014, 165702–7pp.
Abstract: The IRIS group at IFIC-Valencia has developed a second version of a Compton camera prototype for hadron therapy treatment monitoring, with the aim of improving the performance with respect to its predecessor. The system is composed of three Lanthanum (III) bromide (LaBr3) crystals coupled to silicon photomultipliers (SiPMs). The detector energy resolution has been improved to 5.6% FWHM at 511 keV and an angular resolution of 8.0 degrees has been obtained. Images of a Na-22 point-like source have been reconstructed selecting two and three interaction events. Moreover, the experimental data have been reproduced with Monte Carlo simulations using a Compton camera module (CCMod) in GATE v8.2 obtaining a good correlation.
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Abbas, G. (2016). Right-right-left extension of the Standard Model. Mod. Phys. Lett. A, 31(19), 1650117–10pp.
Abstract: A right-right-left extension of the Standard Model is proposed. In this model, SM gauge group SU(2)(L) circle times U(1)(Y) is extended to SU(2)(L) circle times SU(2)(R) circle times SU(2)'(R) circle times SU(2)'(L) circle times U(1)(Y). The gauge symmetries SU(2)'(R), SU(2)'(L) are the mirror counterparts of the SU(2)(L) and SU(2)(R), respectively. Parity is spontaneously broken when the scalar Higgs fields acquire vacuum expectation values (VEVs) in a certain pattern. Parity is restored at the scale of SU(2)'(L). The gauge sector has a unique pattern. The scalar sector of the model is optimum, elegant and unique.
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Baker, M. J., Bordes, J., Hong-Mo, C., & Tsun, T. S. (2012). Developing the Framed Standard Model. Int. J. Mod. Phys. A, 27(17), 1250087–45pp.
Abstract: The framed standard model (FSM) suggested earlier, which incorporates the Higgs field and three fermion generations as part of the framed gauge theory (FGT) structure, is here developed further to show that it gives both quarks and leptons hierarchical masses and mixing matrices akin to what is experimentally observed. Among its many distinguishing features which lead to the above results are (i) the vacuum is degenerate under a global su(3) symmetry which plays the role of fermion generations, (ii) the fermion mass matrix is “universal,” rank-one and rotates (changes its orientation in generation space) with changing scale mu, (iii) the metric in generation space is scale-dependent too, and in general nonflat, (iv) the theta-angle term in the quantum chromodynamics (QCD) action of topological origin gets transformed into the CP-violating phase of the Cabibbo-Kobayashi-Maskawa (CKM) matrix for quarks, thus offering at the same time a solution to the strong CP problem.
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