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Martin Lozano, V., Sanda Seoane, R. M., & Zurita, J. (2023). Z'-explorer 2.0: Reconnoitering the dark matter landscape. Comput. Phys. Commun., 288, 108729–14pp.
Abstract: We introduce version 2.0 of Z'-explorer, a software tool that provides a simple, fast, and user-friendly test of models with an extra U (1) gauge boson (Z') against experimental LHC results. The main novelty of the second version is the inclusion of missing energy searches, as the first version only included final states into SM particles. Hence Z'-explorer 2.0 is able to test dark matter models where the Z' acts as an s-channel mediator between the Standard Model and the dark sector, a widespread benchmark employed by the ATLAS and CMS experimental collaborations. To this end, we perform here the first public reinterpretation of the most recent ATLAS mono-jet search with 139 fb-1. In addition, the corresponding searches in the visible final states have also been updated. We illustrate the power of our code by re -obtaining public plots and also showing novel results. In particular, we study the cases where the Z' couples strongly to top quarks (top-philic), where dark matter couples with a mixture of vector and axial-vector couplings, and also perform a scan in the parameter space of a string inspired Stuckelberg model. Z'-explorer 2.0 is publicly available on GitHub. Program summary Program Title: Z'-explorer 2.0 CPC Library link to program files: https://doi .org /10 .17632 /k7tdp8kwgf .2 Developer's repository link: https://github .com /ro -sanda /Z--explorer-2 .0 Licensing provisions: GPLv3 Programming language: C++ and bash Nature of problem: New SM neutral gauge bosons, Z', are ubiquitously present in models of New Physics. In order to confront these models versus a large and ever-growing library of LHC searches, Z'-explorer 1.0 had already included all final states including Standard Model particles. Notably, the previous version of this tool lacked the so-called invisible final states manifested as a momentum imbalance in the transverse plane (“missing energy”). These searches help to probe mediators into a dark sector, where a dark matter candidate resides. Solution method: Z'-explorer encodes the production cross sections for Z' bosons at the LHC as a function of their mass, allowing for a fast evaluation of the exclusion limits. This version of Z'-explorer includes a careful validation of the latest search with one energetic jet (mono-jet) performed by the ATLAS collaboration. Hence one can now test if a given point in parameter space is excluded by both visible and invisible searches. The modular structure of the code has been kept, which allows for potential additions (low-energy constraints, flavor, extrapolation to future colliders).
Keywords: LHC; New physics; Exclusion limits; Dark matter
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Gonzalez-Iglesias, D., Esperante, D., Gimeno, B., Blanch, C., Fuster-Martinez, N., Martinez-Reviriego, P., et al. (2023). Analysis of the Multipactor Effect in an RF Electron Gun Photoinjector. IEEE Trans. Electron Devices, 70(1), 288–295.
Abstract: The objective of this work is the evaluation of the risk of suffering a multipactor discharge within an RF electron gun photoinjector. Photoinjectors are a type of source for intense electron beams, which are the main electron source for synchrotron light sources, such as free-electron lasers. The analyzed device consists of 1.6 cells and it has been designed to operate at the S-band. Besides, around the RF gun there is an emittance compensation solenoid, whose magnetic field prevents the growth of the electron beam emittance, and thus the degradation of the properties of the beam. The multipactor analysis is based on a set of numerical simulations by tracking the trajectories of the electron cloud in the cells of the device. To reach this aim, an in-house multipactor code was developed. Specifically, two different cases were explored: with the emittance compensation solenoid assumed to be off and with the emittance compensation solenoid in operation. For both the cases, multipactor simulations were carried out exploring different RF electric field amplitudes. Moreover, for a better understanding of the multipactor phenomenon, the resonant trajectories of the electrons and the growth rate of the electrons population are investigated.
Keywords: Magnetic tunneling; Multipactor effect; photoinjector; RF breakdown; RF gun
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Martin-Luna, P., Gimeno, B., Gonzalez-Iglesias, D., Esperante, D., Blanch, C., Fuster-Martinez, N., et al. (2023). On the Magnetic Field of a Finite Solenoid. IEEE Trans. Magn., 59(4), 7000106–6pp.
Abstract: The magnetostatic field of a finite solenoid with infinitely thin walls carrying a dc current oriented in the azimuthal direction is calculated everywhere in space in terms of complete elliptic integrals by direct integration of the Biot-Savart law. The solution is particularized near the solenoid axis and in the midplane perpendicular to the axis obtaining expressions that agree with some typical approximations that are made in introductory courses of electromagnetism or in the technical literature. The range of validity of these approximations has been studied comparing them with the obtained general expression.
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Millar, W. L. et al, & Bañon Caballero, D. (2023). High-Power Test of Two Prototype X-Band Accelerating Structures Based on SwissFEL Fabrication Technology. IEEE Trans. Nucl. Sci., 70(1), 1–19.
Abstract: This article presents the design, construction, and high-power test of two $X$ -band radio frequency (RF) accelerating structures built as part of a collaboration between CERN and the Paul Scherrer Institute (PSI) for the compact linear collider (CLIC) study. The structures are a modified “tuning-free ” variant of an existing CERN design and were assembled using Swiss free electron laser (SwissFEL) production methods. The purpose of the study is two-fold. The first objective is to validate the RF properties and high-power performance of the tuning-free, vacuum brazed PSI technology. The second objective is to study the structures' high-gradient behavior to provide insight into the breakdown and conditioning phenomena as they apply to high-field devices in general. Low-power RF measurements showed that the structure field profiles were close to the design values, and both structures were conditioned to accelerating gradients in excess of 100 MV/m in CERN's high-gradient test facility. Measurements performed during the second structure test suggest that the breakdown rate (BDR) scales strongly with the accelerating gradient, with the best fit being a power law relation with an exponent of 31.14. In both cases, the test results indicate that stable, high-gradient operation is possible with tuning-free, vacuum brazed structures of this kind.
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Real, D., Calvo, D., Diaz, A., Alves Garre, S., Carretero, V., Sanchez Losa, A., et al. (2023). An Ultra-Narrow Time Optical Pulse Emitter Based on a Laser: UNTOPEL. IEEE Trans. Nucl. Sci., 70(10), 2364–2372.
Abstract: Light sources that emit repetitive subnanosecond pulses are used in neutrino telescopes for time calibration. Optical pulses with an ultra-narrow (subnanosecond) width can replicate the light produced by neutrino interactions, and are an important calibration and test element. By measuring the time-of-flight of the light, it is possible to provide a relative time calibration for all the detector photomultipliers. This work presents the ultra-narrow time optical pulse emitter based on a laser (UNTOPEL), an instrument emitting ultra-short laser optical pulses with a duration of 500 ps, energies per pulse of four microjoules at a wavelength of 532 nm, and a timing precision of 400 ps. The UNTOPEL pulse intensity can be fine-tuned, which is a novelty and a significant advantage in those applications that need to illuminate light detectors located at different distances with the same light intensity. The UNTOPEL pulse intensity can be controlled remotely, allowing for its use in operating conditions where physical access is impossible or difficult. Moreover, it is easy to operate and can be easily controlled through an inter-integrated circuit bus. The UNTOPEL is a sound instrument used when subnanosecond pulses and variable energy emissions are needed.
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