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Polarized simulations of or boson production with hadronic decays
No full textUnderstanding the polarization of massive vector bosons provides a powerful method to probe the electroweak symmetry breaking mechanism and to test the Standard Model and its potential extensions. This thesis investigates hadronically decaying, polarized W ± and Z bosons at the LHC energy scale. By analyzing simulated events, the effects of different polarization states on jet substructure observables are explored. The results show that jets stemming from transversely polarized bosons often exhibit distinct two-pronged substructures, while longitudinally polarized bosons yield more isotropic jets. These polarization-dependent patterns manifest in variables such as N-subjettiness, transverse momentum correlation functions, and Fox-Wolfram moments. When attempting to distinguish vector boson jets from QCD jets in the context of highly boosted boson production, a simple mass-window selection on jet candidates offers only limited improvement in identifying vector boson jets. Moreover, relying solely on Fox-Wolfram moments is insufficient. Instead, more advanced jet substructure variables are required to achieve robust discrimination. Overall, this study highlights the sensitivity of jet substructure observables to vector boson polarization and provides insights for the development of future jet tagging algorithms
AD-7/GBAR status report for the 2025 CERN SPSC
No full textWe report on the activities performed during 2024 and the plans for 2025 for the GBAR experiment. Highlights include record positron accumulation and an order-of-magnitude increase in antihydrogen production, with several publications in preparation
iRPC FEB cooling system
No full textIn view of the High-Luminosity upgrade of LHC, the CMS Muon spectrometer is undergoing a series of upgrade projects,in particular the addition of four new stations featuring improved Resistive Plate Chambers (iRPC), which will cover the pseudo-rapidity range from 1.8 to 2.4. A new Front-End Board (FEB) is designed to read iRPC signals with a very low threshold and a Time Digital Converter (TDC) embedded into a Cyclone V INTEL FPGA with a resolution of 30\,ps and a sampling of 100 MHz. In contrast to the previous RPC boards, this one produces 21--22 W of heat in a confined space that needs to be carefully evacuated. A cheap and robust cooling system was designed on the basis of a copper plate and water cooling. This system was first simulated with a Computational Fluid Dynamics package, Ansys Fluent, and then optimized with thermal measurements. In this paper, the system and its prominent features are described. A quantitative comparison between the experimental measurements in the laboratory and the simulation is provided to demonstrate the robustness of this simple cooling system
DUNE-PRISM: Reducing neutrino interaction model dependence with a movable neutrino detector
No full textThe Deep Underground Neutrino Experiment (DUNE) is a next-generation long-baseline neutrino oscillation experiment designed to make precision measurements in the world's most powerful neutrino beam. Neutrinos are measured at two detector facilities: a near detector (ND) located at Fermilab close to where the beam is produced and a far detector (FD) at SURF. The Precision Reaction Independent Spectrum Measurement (PRISM) system allows for the measurement of different neutrino energy spectra by moving the near detector away from the central axis of the neutrino beam. These off-axis neutrino energy spectra provide a new degree of freedom that can be used to develop a deeper understanding of the relationship between the observable energy deposits in the detector and the energy of the interacting neutrino. This can benefit DUNE by significantly reducing the impact of systematic uncertainties in the neutrino interaction model. One possible use of the PRISM system is to perform a novel neutrino oscillation analysis that linearly combines off-axis neutrino energy spectra at the near detector to produce data-driven predictions of the far detector energy spectrum
The hadronic contribution to the running of and the electroweak mixing angle
No full textWe report on our update to \cite{Ce:2022eix} on the hadronic running of electroweak couplings from -improved Wilson fermions with flavours. The inclusion of additional ensembles at very fine lattice spacings together with a number of techniques to split the different contributions for a better control of cutoff effects allows us to substantially improve the precision. We employ two different discretizations of the vector current to compute the subtracted Hadronic Vacuum Polarization (HVP) functions and for Euclidean time momenta up to . To reduce cutoff effects in the short distance region we apply a suitable subtraction to the TMR kernel function, which cancels the leading behaviour. The subtracted term is then computed in perturbative QCD using the Adler function and added back to compensate for the subtraction. Chiral-continuum extrapolations are performed with five values of the lattice spacing and several pion masses, including its physical value, and several fit ansätze are explored to estimate the systematics arising from model selection. Our results show excellent prospects for high-precision estimates of at the Z-pole.We report on our update to [1] on the hadronic running of electroweak couplings from -improved Wilson fermions with flavours. The inclusion of additional ensembles at very fine lattice spacings together with a number of techniques to split the different contributions for a better control of cutoff effects allows us to substantially improve the precision. We employ two different discretizations of the vector current to compute the subtracted Hadronic Vacuum Polarization (HVP) functions and for Euclidean time momenta up to . To reduce cutoff effects in the short distance region we apply a suitable subtraction to the TMR kernel function, which cancels the leading behaviour. The subtracted term is then computed in perturbative QCD using the Adler function and added back to compensate for the subtraction. Chiral-continuum extrapolations are performed with five values of the lattice spacing and several pion masses, including its physical value, and several fit ansätze are explored to estimate the systematics arising from model selection. Our results show excellent prospects for high-precision estimates of at the Z-pole
The LHC as a TeV Muon Beam Dump: Muonphilic Scalars at FASER
No full textThe FASER experiment was designed to study long-lived dark sector particles and neutrinos traveling in the forward direction at the LHC. Neutrinos are predominantly produced from meson decays, which also result in an intense energetic flux of muons in the forward direction regularly observed by FASER. So far, these muons are treated only as backgrounds to neutrino and new physics studies, and extensive effort is required to suppress them. In this study, we consider the opposite scenario and use muons produced in the forward direction to produce new muonphilic scalars, which can then be searched for at the FASER detector. To minimize the backgrounds for this search, we make use of an upgraded preshower component, which is expected to be installed at FASER before the end of Run 3, and is capable of spatially resolving two energetic photons. We find that FASER, and its upgrade, FASER2 can probe currently unconstrained regions of parameter space, including regions that can potentially explain the anomaly. This highlights the physics opportunities that the intense TeV muon beam at the LHC can bring
Detection efficiency and spatial resolution of Monolithic Active Pixel Sensors bent to different radii
No full textBent monolithic active pixel sensors are the basis for the planned fully cylindrical ultra low material budget tracking detector ITS3 of the ALICE experiment. This paper presents results from testbeam campaigns using high-energy particles to verify the performance of 50 um thick bent ALPIDE chips in terms of efficiency and spatial resolution. The sensors were bent to radii of 18, 24 and 30 mm, slightly smaller than the foreseen bending radii of the future ALICE ITS3 layers. An efficiency larger than and a spatial resolution of approximately 5 um, in line with the nominal operation of flat ALPIDE sensors, is obtained at nominal operating conditions. These values are found to be independent of the bending radius and thus constitute an additional milestone in the demonstration of the feasibility of the planned ITS3 detector. In addition, a special geometry in which the beam particles graze the chip and traverse it laterally over distances of up to 3 mm is investigated