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Search for compressed electroweakinos with low-momentum isolated tracks
No full textA search is presented for higgsino dark matter (DM) in final states with a low momentum (soft), isolated track and large missing transverse momentum.
In the minimal supersymmetric standard model (MSSM), charginos are most often produced in association with a nearly mass-degenerate neutralino or another chargino, and predominantly decay into the lightest neutralino (DM candidate) and a soft pion. For a mass difference less than , a discernible displacement of the pion's track with respect to the primary vertex can arise, reaching up to about for the smallest allowed . A parameterized multivariate classifier is employed to distinguish the signal track from background tracks, optimally targeting a range of by exploiting the track transverse momentum, impact parameter, and event topology to varying degrees depending on the assumed . The analyzed data correspond to an integrated luminosity of collected by the CMS experiment in proton-proton collisions at . No evidence of new physics is observed, and limits are set at the confidence level in the mass plane of the model. Assuming MSSM cross sections, values of between and are excluded for a mass chargino, and chargino masses up to are excluded for of
Upgrade of the CMS Electromagnetic Calorimeter for the High-Luminosity LHC
No full textThe High Luminosity upgrade of the LHC (HL-LHC) at CERN will provide unprecedented instantaneous and integrated luminosities of around 5 x 10 cm s and 3000/fb, respectively. The expected average of 140 to 200 collisions per bunch-crossing represents a severe challenge for the detectors. In the barrel region of the CMS electromagnetic calorimeter (ECAL), the lead tungstate crystals and avalanche photodiodes will operate at a lower temperature with respect to the present and the entire readout and trigger electronics will be replaced.
Each of the 61,200 ECAL barrel crystals will be read out by two custom ASICs providing signal amplification with two gains, ADC with 160 MHz sampling rate, and lossless data compression for the transmission of all channel data to the off-detector electronics. Trigger primitive generation by updated reconstruction algorithms as well as data acquisition will be implemented on powerful FPGA processors boards. The upgrade of the ECAL electronics will allow to maintain the excellent energy resolution of the current detector and, in addition, to greatly improve the time resolution of electrons and photons.
This document will present the design and status of the individual components of the upgraded ECAL barrel detector, and the results of energy and time resolution measurements obtained with the latest ECAL readout electronics prototypes using electron beams with energies of up to 250 GeV at the CERN SPS
Molecular Antimatter Confinement Experiment (MACE): Proposal to investigate synthesis of pbar@C60 antimatter endohedral fullerenes by ion implantation at ELENA-TELMAX
No full textThis proposal describes an experiment at the ELENA-TELMAX area at the CERN AD to test whether antiprotons (pbar) can be successfully implanted into nanoporous materials such as C60 fullerenes for high-density energy storage. Bulk production of antimatter remains a technical challenge, which is not addressed in this work. More pressing is the need for a reliable high-density containment strategy that avoids prompt annihilation with regular matter. Confidence that generated antimatter will not promptly annihilate would encourage more practical consideration of production methods and applications. Proposed high-density containment strategies in the literature (such as diamagnetically-levitated antihydrogen ice balls) are not fail safe. Containment of antimatter within fullerenes or similar materials may serve as a safer storage method, and offers a new direction for inquiry on this problem. Results from ion implantation experiments into fullerenes in the literature suggest not only that existing technology is sufficient, but that yields may be favorable. In this work, we describe the scientific basis for containment, the technical feasibility of an experiment, and the programmatic support requirements for realizing the scientific objectives of the experiment
Search for heavy neutral leptons in decays to positrons
No full textA search for heavy neutral lepton () production in in-flight decays using data collected by the NA62 experiment at CERN in 2017-2024 is reported. Upper limits for the extended neutrino mixing matrix element are established at the level of for heavy neutral leptons with mass in the range 95-126 MeV/ and lifetime exceeding 50 ns.A search for heavy neutral lepton () production in in-flight decays using data collected by the NA62 experiment at CERN in 2017-2024 is reported. Upper limits for the extended neutrino mixing matrix element are established at the level of for heavy neutral leptons with mass in the range 95-126 and lifetime exceeding 50 ns
Upgrade of the ATLAS Hadronic Tile Calorimeter for the High Luminosity LHC
No full textThe Tile Calorimeter (TileCal) is a sampling hadronic calorimeter covering the central region of the ATLAS experiment, with steel as absorber and plastic scintillators as active medium. The High Luminosity phase of LHC, delivering five times the LHC nominal instantaneous luminosity, is expected to begin in 2030. TileCal will require new electronics to meet the requirements of a 1 MHz trigger, higher ambient radiation, and to ensure better performance under high pile-up conditions. Both the on- and off-detector TileCal electronics will be replaced during the shutdown of 2026-2030. PMT signals from every TileCal cell will be digitized and sent directly to the back-end electronics, where the signals are reconstructed, stored, and sent to the first level of trigger at a rate of 40 MHz. This will provide better precision of the calorimeter signals used by the trigger system and will allow the development of more complex trigger algorithms. The modular front-end electronics feature radiation-tolerant commercial off-the-shelf components and redundant design to minimise single points of failure. The timing, control and communication interface with the off-detector electronics is implemented with modern Field Programmable Gate Arrays (FPGAs) and high speed fibre optic links running up to 9.6 Gb/s. The TileCal upgrade program has included extensive R&D and test beam studies. A Demonstrator module with reverse compatibility with the existing system was inserted in ATLAS in August 2019 for testing in actual detector conditions. The ongoing developments for on- and off-detector systems, together with expected performance characteristics and results of test-beam campaigns with the electronics prototypes will be discussed
Searching for direct slepton production in moderately compressed mass spectra with the ATLAS detector
No full textThese proceedings summarise results presented for the direct pair production of charged light-flavour sleptons (), each decaying into a stable neutralino () and an associated Standard Model lepton. The analyses focus on the challenging 'corridor' region, where the mass difference, , is less or similar to the mass of the boson, , with the aim to close a persistent gap in sensitivity to models in this region. The searches utilise LHC collision data at TeV recorded by the ATLAS detector, corresponding to an integrated luminosity of 140 fb. The results are generally consistent with the Standard Model, with the most significant deviations observed with a local significance of in the selectron search, and in the smuon search. Constraints at the 95% confidence level are set on simplified models of selectron and smuon pair production, where selectrons (smuons) with masses up to 300 (350) GeV can be excluded for between 2 GeV and 100 GeV
