Vijande, J., Carmona, V., Lliso, F., Ballester, F., & Perez-Calatayud, J. (2024). An efficient component of the redundancy calibration program to ensure equipment stability by assaying HDR Ir-192 sources at the time of replacement. J. Appl. Clin. Med. Phys, , 5pp.
Abstract: BackgroundBrachytherapy (BT) treatments involving temporary high-dose rate (HDR) sources are extensively employed in clinical practice. Ensuring the consistency of all measurement equipment at the hospital level is crucial, requiring a robust redundancy and consistency program. This enables the institution to verify the stability of the dosimetry system over time.PurposeTo describe, justify, and analyze a component of the redundancy program of the calibration protocols followed by the Radiotherapy Department of the Hospital Universitari i Polit & egrave;cnic La Fe (Val & egrave;ncia, Spain) during the last 10 years for the case of HDR BT as an additional component to ensure long term stability of the measurement equipment.MethodsAt the time the HDR BT source is replaced, its Air Kerma Strength (SK) is measured. By comparing this value with the one obtained at the time of installation (corrected by decay), a clear determination of the stability of the measurement equipment can be performed.ResultsDifference between SK,vendor and SK,hosp as a function of the measurement date is reported for a 10 years' period. All measurements are well within the +/- 3% tolerance level recommended in current international guidelines. Percentage differences of SK,hosp values at the time of replacement compared to SK,hosp ones at the time when the source was installed are within the +/- 0.5% range, reflecting oscillations around a null deviation.ConclusionsThe method proposed allows any hospital to ensure a redundancy component of the long-term stability of all equipment involved in BT measurements in a very simple and time efficient manner. Additionally, it enables the hospital to maintain a detailed log of historical differences, facilitating the identification and correction of potential systematic deviations over time.
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ATLAS Collaboration(Aad, G. et al), Aikot, A., Amos, K. R., Aparisi Pozo, J. A., Bailey, A. J., Bouchhar, N., et al. (2024). Search for new phenomena with top-quark pairs and large missing transverse momentum using 140 fb-1 of pp collision data at √s=13 TeV with the ATLAS detector. J. High Energy Phys., 03(3), 139–58pp.
Abstract: A search is conducted for new phenomena in events with a top quark pair and large missing transverse momentum, where the top quark pair is reconstructed in final states with one isolated electron or muon and multiple jets. The search is performed using the Large Hadron Collider proton-proton collision data sample at a centre-of-mass energy of root s = 13TeV recorded by the ATLAS detector that corresponds to an integrated luminosity of 140 fb(-1). An analysis based on neural network classifiers is optimised to search for directly produced pairs of supersymmetric partners of the top quark (stop), and to search for spin-0 mediators, produced in association with a pair of top quarks, that decay into dark-matter particles. In the stop search, the analysis is designed to target models in which the mass difference between the stop and the neutralino from the stop decay is close to the top quark mass. This new search is combined with previously published searches in final states with different lepton multiplicities. No significant excess above the Standard Model background is observed, and limits at 95% confidence level are set. Models with neutralinos with masses up to 570 GeV are excluded, while for small neutralino masses models are excluded for stop masses up to 1230 GeV. Scalar (pseudoscalar) dark matter mediator masses as large as 350 (370) GeV are excluded when the coupling strengths of the mediator to Standard Model and dark-matter particles are both set to one. At lower mediator masses, models with production cross-sections as small as 0.15 (0.16) times the nominal predictions are excluded. Results of this search are also used to set constraints on effective four-fermion contact interactions between top quarks and neutrinos.
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Babeluk, M. et al, Lacasta, C., Marinas, C., Mazorra de Cos, J., & Vobbilisetti, V. (2024). The OBELIX chip for the Belle II VTX upgrade. Nucl. Instrum. Methods Phys. Res. A, 1067, 169659–3pp.
Abstract: The OBELIX depleted monolithic active CMOS pixel sensor (DMAPS) is currently developed for the upgrade of the vertex detector of the Belle II experiment located at Tsukuba/Japan. The pixel matrix of OBELIX is inherited from the TJ-Monopix2 chip, but the periphery includes additional features to improve performance and allow the integration into a larger detector system. The new features include a trigger unit to process trigger signals, a precision timing module and a possibility to transmit low granularity hit information with low latency to contribute to the Belle II trigger. Additionally, low dropout voltage regulators and an ADC to monitor power consumption and substrate temperature is developed. This paper will focus on the trigger contribution capabilities of the OBELIX chip.
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Silva, J. E. G., Yesiltas, O., Furtado, J., & Araujo Filho, A. A. (2024). Strain effects on the electronic properties of a graphene wormhole. Eur. Phys. J. Plus, 139(8), 762–16pp.
Abstract: In this work, we explore the strain and curvature effects on the electronic properties of a curved graphene structure, called the graphene wormhole. The electron dynamics is described by a massless Dirac fermion containing position-dependent Fermi velocity. In addition, the strain produces a pseudo-magnetic vector potential to the geometric coupling. For an isotropic strain tensor, the decoupled components of the spinor field exhibit a supersymmetric (SUSY) potential, depending on the centrifugal term and the external magnetic field only. In the absence of an external magnetic field, the strain yields an exponentially damped amplitude, whereas the curvature leads to a power-law damping of the wave function. The spin-curvature coupling breaks the chiral symmetry between the upper and the lower spinor component, which leads to the increasing of the wave function on either upper or lower region of the wormhole, i.e., depending on the spin number. By adding a uniform magnetic field, the effective potential exhibits an asymptotic quadratic profile and a spin-curvature barrier near the throat. As a result, the bound states (Landau levels) are confined around the wormhole throat showing an asymmetric and spin-dependent profile.
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Belle II VTX Collaboration(Babeluk, M. et al)., Marinas, C., & Mazorra de Cos, J. (2024). The DMAPS upgrade of the Belle II vertex detector. Nucl. Instrum. Methods Phys. Res. A, 1064, 169428–5pp.
Abstract: The Belle II experiment at KEK in Japan considers an upgrade for the vertex detector system in line with the accelerator upgrade for higher luminosity at long shutdown 2 planned for 2028. One proposal for the upgrade of the vertex detector called VTX aims to improve background robustness and reduce occupancy using small and fast pixels. VTX accommodates the OBELIX depleted monolithic active CMOS pixel sensor (DMAPS) on all five proposed layers. OBELIX is specifically developed for the VTX application and based on the TJ-Monopix2 chip initially developed to meet the requirements of the outer layers of the ATLAS inner tracker (ITk). This paper will review recent tests of the TJ-Monopix2 chip as well as various design aspects of the OBELIX-1 chip currently under development.
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