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1. The FASER detector

   https://doi.org/10.1088/1748-0221/19/05/P05066  

   Abreu, Henso; Mansour, Elham Amin; Antel, Claire; Ariga, Akitaka; Ariga, Tomoko; Bernlochner, Florian; Boeckh, Tobias; Boyd, Jamie; Brenner, Lydia; Cadoux, Franck; et al (May 2024, Journal of Instrumentation)

   Abstract FASER, the ForwArd Search ExpeRiment, is an experiment dedicated to searching for light, extremely weakly-interacting particles at CERN's Large Hadron Collider (LHC). Such particles may be produced in the very forward direction of the LHC's high-energy collisions and then decay to visible particles inside the FASER detector, which is placed 480 m downstream of the ATLAS interaction point, aligned with the beam collisions axis. FASER also includes a sub-detector, FASERν, designed to detect neutrinos produced in the LHC collisions and to study their properties. In this paper, each component of the FASER detector is described in detail, as well as the installation of the experiment system and its commissioning using cosmic-rays collected in September 2021 and during the LHC pilot beam test carried out in October 2021. FASER has successfully started taking LHC collision data in 2022, and will run throughout LHC Run 3. 

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2. The new monolithic ASIC of the preshower detector for di-photon measurements in the FASER experiment at CERN

   https://doi.org/10.1088/1748-0221/18/02/C02002  

   Gonzalez-Sevilla, S. (February 2023, Journal of Instrumentation)

   Abstract The ForwArd Search ExpeRiment (FASER) is an experiment searching for new light and weakly-interacting particles at CERN’s Large Hadron Collider. FASER is composed of different sub-detectors, including silicon microstrip detectors, scintillator counters and an electromagnetic calorimeter. In this paper, a new preshower detector for the FASER experiment is presented. The new detector, based on monolithic pixel ASICs, will provide excellent spatial and time resolutions and a large charge dynamic range. First results from a prototype chip produced by IHP in 130 nm SiGe BiCMOS technology are shown. 

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3. Highlight: Forward Physics (LHCf + FASER)

   https://doi.org/10.22323/1.397.0025  

   FASER and LHCf Collaborations, Berti (October 2021, The Ninth Annual Conference on Large Hadron Collider Physics (LHCP2021))

   The LHC Run III will be a crucial run for the two LHC forward experiments: LHCf and FASER. In particular, Run III will be the last run where the LHCf detector can operate, and the first run of the new FASER project. The LHCf experiment is dedicated to precise measurements of forward production, necessary to tune hadronic interaction models employed in cosmic-ray physics. In Run III, the experiment will accomplish two fundamental goals: operating in p-p collisions at s√= s = 14 TeV, it will acquire a statistics that is ten times larger respect to Run II, in order to have precise measurements of π0 π 0 production; operating in high energy p-O and O-O collisions, it will measure forward production in a configuration that is very similar to the first interaction of an Ultra High Energy Cosmic Ray with an atmospheric nucleus. The FASER experiment is dedicated to the search of new weakly-interacting light particles thanks to a forward detector with proper shielding from Standard Model background. In Run III, it will be able to search for new particles with a good sensitivity, which can be strongly improved after an upgrade before Run IV. In addition, thanks to the dedicated FASERν detector, it will measure neutrino production at a collider for the first time. In this contribution, we discuss the main results expected from the LHCf and FASER experiments in Run III, highlighting their fundamental contribution in research fields that are not accessible to the four large LHC experiments. 

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4. Search for photons above ${10}^{18}\mathrm{eV}$ by simultaneously measuring the atmospheric depth and the muon content of air showers at the Pierre Auger Observatory

   https://doi.org/10.1103/PhysRevD.110.062005  

   Abdul_Halim, A; Abreu, P; Aglietta, M; Allekotte, I; Almeida_Cheminant, K; Almela, A; Aloisio, R; Alvarez-Muñiz, J; Ammerman_Yebra, J; Anastasi, G A; et al (September 2024, Physical Review D)

   The Pierre Auger Observatory is the most sensitive instrument to detect photons with energies above $10^{17}\mathrm{eV}$. It measures extensive air showers generated by ultrahigh energy cosmic rays using a hybrid technique that exploits the combination of a fluorescence detector with a ground array of particle detectors. The signatures of a photon-induced air shower are a larger atmospheric depth of the shower maximum ( $X_{\max }$) and a steeper lateral distribution function, along with a lower number of muons with respect to the bulk of hadron-induced cascades. In this work, a new analysis technique in the energy interval between 1 and 30 EeV ( $1\mathrm{EeV}=10^{18}\mathrm{eV}$) has been developed by combining the fluorescence detector-based measurement of $X_{\max }$with the specific features of the surface detector signal through a parameter related to the air shower muon content, derived from the universality of the air shower development. No evidence of a statistically significant signal due to photon primaries was found using data collected in about 12 years of operation. Thus, upper bounds to the integral photon flux have been set using a detailed calculation of the detector exposure, in combination with a data-driven background estimation. The derived 95% confidence level upper limits are 0.0403, 0.01113, 0.0035, 0.0023, and $0.0021{\mathrm{km}}^{-2}{\mathrm{sr}}^{-1}{\mathrm{yr}}^{-1}$above 1, 2, 3, 5, and 10 EeV, respectively, leading to the most stringent upper limits on the photon flux in the EeV range. Compared with past results, the upper limits were improved by about 40% for the lowest energy threshold and by a factor 3 above 3 EeV, where no candidates were found and the expected background is negligible. The presented limits can be used to probe the assumptions on chemical composition of ultrahigh energy cosmic rays and allow for the constraint of the mass and lifetime phase space of super-heavy dark matter particles. Published by the American Physical Society2024 

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5. The DUNE Far Detector Vertical Drift Technology. Technical Design Report

   https://doi.org/10.1088/1748-0221/19/08/T08004  

   Abed_Abud, A; Abi, B; Acciarri, R; Acero, MA; Adames, MR; Adamov, G; Adamowski, M; Adams, D; Adinolfi, M; Adriano, C; et al (August 2024, Journal of Instrumentation)

   Abstract DUNE is an international experiment dedicated to addressing some of the questions at the forefront of particle physics and astrophysics, including themystifying preponderance of matter over antimatter in the early universe. The dual-site experiment will employ an intense neutrino beam focused on a near and a far detector as it aims to determine the neutrino mass hierarchy and to make high-precision measurements of the PMNS matrix parameters, including the CP-violating phase. It will also stand ready to observe supernova neutrino bursts, and seeks to observe nucleon decay as a signature of a grand unified theory underlying the standard model.The DUNE far detector implements liquid argon time-projection chamber (LArTPC) technology, and combines the many tens-of-kiloton fiducial mass necessary for rare event searches with the sub-centimeter spatial resolutionrequired to image those events with high precision. The addition of a photon detection system enhances physics capabilities for all DUNE physics drivers and opens prospects for further physics explorations. Given its size, the far detector will be implemented as a set of modules, with LArTPC designs that differ from one another as newer technologies arise.In the vertical drift LArTPC design, a horizontal cathode bisects the detector, creating two stacked drift volumes in which ionization charges drift towards anodes at either the top or bottom. The anodes are composed of perforated PCB layers with conductive strips, enabling reconstruction in 3D.Light-trap-style photon detection modules are placed both on the cryostat's side walls and on the central cathode where they are optically powered.This Technical Design Report describes in detail the technical implementations of each subsystem of this LArTPC that, together with the other far detector modules and the near detector, will enable DUNE to achieve its physics goals. 

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