arXiv subjects
Publications and source records attributed to Marta Felcini.
Understanding the fundamental nature and properties of dark matter is a main goal of fundamental physics experiments. The LHC experiments seek to detect processes that could explain how dark matter is produced and how it interacts with ordinary matter. After a reminder of the main dark matter production models, we give an overview of LHC searches for dark matter production processes and outline future opportunities.
The searches for new particles that could be constituents of the dark matter in the universe are an essential part of the physics program of the experiments at the Large Hadron Collider. An overview of recent dark matter candidate searches is presented with a focus on new results obtained by the ATLAS and CMS experiments from the analysis of the proton-proton collision data at 13 TeV center-of-mass energy collected in the first part of Run 2.
The CMS experiment will collect data from the proton-proton collisions delivered by the Large Hadron Collider (LHC) at a centre-of-mass energy up to 14 TeV. The CMS trigger system is designed to cope with unprecedented luminosities and LHC bunch-crossing rates up to 40 MHz. The unique CMS trigger architecture only employs two trigger levels. The Level-1 trigger is implemented using custom electronics. The High Level Trigger is implemented on a large cluster of commercial processors, the Filter Farm. Trigger menus have been developed for detector calibration and for fulfilment of the CMS physics program, at start-up of LHC operations, as well as for operations with higher luminosities. A complete multipurpose trigger menu developed for an early instantaneous luminosity of 10^{32}cm{-2}s{-1} has been tested in the HLT system under realistic online running conditions. The required computing power needed to process with no dead time a maximum HLT input rate of 50 kHz, as expected at startup, has been measured, using the most recent commercially available processors. The Filter Farm has been equipped with 720 such processors, providing a computing power at least a factor two larger than expected to be needed at startup. Results for the commissioning of the full-scale trigger and data acquisition system with cosmic muon runs are reported. The trigger performance during operations with LHC circulating proton beams, delivered in September 2008, is outlined and first results are shown.
We give an overview of the main features of the CMS trigger and data acquisition (DAQ) system. Then, we illustrate the strategies and trigger configurations (trigger tables) developed for the detector calibration and physics program of the CMS experiment, at start-up of LHC operations, as well as their possible evolution with increasing luminosity. Finally, we discuss the expected CPU time performance of the trigger algorithms and the CPU requirements for the event filter farm at start-up.
The aim of this CP symmetry test in positronium is to measure the CP violation amplitude parameter \ccp. This is derived from the measurement of the asymmetry in an angular distribution of the photons from the decay of the ortho-positronium in a magnetic field. The Standard Model prediction for \ccp\ is a value of the order of $10^{-9}$. Thus the observation of a larger \ccp\ value would be signal of physics beyond the Standard Model. A previous measurement has found \ccp consistent with zero, with an uncertainty of $\sim 10^{-2}$. We have investigated the possibility of using the existing ETHZ-INRM-IN2P3 BGO crystal detector, set-up for positronium physics studies, to improve the sensitivity on the \ccp measurement. Preliminary calculations indicate that, using such an apparatus, with some modification, in a magnetic field of 4 kGauss, \ccp could be measured with an uncertainty in the range between $\sim 10^{-4}$ and $\sim 10^{-3}$, depending mainly on the uncertainty in the asymmetry measurement and the angular resolution of the photon detectors. If \ccp is less than $\sim 10^{-4}$, the experimental technique outlined here appears to be inadequate to observe a CP violating effect and new techniques or different observables must be exploited for better sensitivity.
The results of the experimental searches for Higgs particles at LEP, using the data collected at centre-of-mass energies up to 189 GeV, are reviewed and the prospects for the near future outlined.