1,721,153 research outputs found
CMS Phase-2 Inner Tracker system tests
No full textThe LHC will undergo an upgrade known as the High Luminosity LHC (HL-LHC), with the aim of delivering 3000
fb. The Compact Muon Solenoid (CMS) detector will be upgraded during the Phase-2 upgrade to profit from the increased luminosity delivered by HL-LHC.As a part of the Phase-2 upgrade, the CMS tracking detector will be replaced. In the regions closest to the beam, the Phase-2 Inner Tracker (IT) will face harsh conditions with high integrated radiation levels of 1.9 Grad and n, a high pileup of up to 200 collisions per bunch crossing, and hit rate up to 3.2 GHz/cm. The Phase-2 IT is designed to operate in these conditions while maintaining excellent performance. The IT hybrid pixel modules consist of planar or 3D silicon sensors with a pixel size of cm that are bump-bonded to a readout ASIC developed by the RD53 collaboration and a high-density interconnect to connect power lines and readout signals. The modules are mounted on lightweight structures that provide serial power, cooling, and communication. The electrical signals from the modules are transformed into optical signals by the portcards. The central (barrel) part of IT consists of four cylindrical structures, while the forward part is divided into two subsystems composed of eight small and four large disc-like structures per end. We present the results of the IT system tests from structures to portcards with prototype and final IT modules for the three subsystems and discuss their performance
LHCb RICH Upgrade 2019: CLARO calibration and MaPMT characterization
No full textIn the next year LHCb RICH will be upgraded for high luminosity regime. To measure system properties before installation and assure its quality the final set-up for the RICH Upgrade was studied at SysLab, CERN
Measurement of CP-violation in decays of strange beauty mesons
Full text linkThe Standard Model (SM) describes fundamental particles and interactions between them, except gravity. However, it lacks explanations for several phenomena, including the origin of particle masses, dark matter, and the predominance of matter over antimatter in the Universe. Sakharov's conditions, which summarize the prerequisites for generating a matter-dominated Universe, require the presence of a violation of CP-symmetry. In principle, CP-violation is present in the SM within the weak interaction. However, the observed matter-antimatter asymmetry significantly exceeds the asymmetry generated within the SM. Understanding the dominance of matter over antimatter in the Universe requires further searches for extra contributions to the CP-violating phenomena. The Bs → J/ψφ is a crucial decay mode for such investigations, strongly sensitive to new CP-violating processes via the CP-violating phase present in the decay. The discrepancy between the measured and predicted CP-violating phase in this decay would indicate the existence of new CP-violating processes in the Universe. This thesis presents the world's most precise measurement of the amount of CP-violation in Bs → J/ψφ decays up to date. The measurement relies on the simultaneous observation of the decay time and the angles of decay products. Therefore, an accurate description of the decay time and angular-dependent detector inefficiencies and biases is necessary. The precision was achieved by collecting a high-purity dataset of 5.7 inverse fb in the LHCb experiment and improving the measurement methodology. The CP-violating phase is measured to be -0.038 +/- 0.021 (stat.) +/- 0.006 (syst.) mrad. The uncertainties are large, and the value is compatible with the SM prediction within these uncertainties. The main limitation of the precision is the size of the collected dataset. Therefore, more data is necessary to probe the extra CP-violating resources within Bs → J/ψφ decays
Inverted CERN School of Computing 2023
No full textTrack fitting is an everyday repetitive task in the high energy physics detector reconstruction chains. The precision and stability of the fitter depend on the available computing resources. A fit might cost up to half of the CPU time, that is spent on reconstruction. Kalman filters are a widespread solution for the track fitting. A classical Kalman filter is a powerful tool, that is applicable to the linear problems with Gaussian-like errors. However, in reality one has to deal with non-linear problems and sometimes with non-Gaussian errors. The numerical overheat results in instabilities and slows down the convergence. Physics and reparametrisation can help to improve the fit performance. Starting from the simple Kalman filter, we build up a more realistic Kalman filter, discussing practical tricks and possible issues of implementation. We then talk about implementation differences if using CPU or GPU
Inverted CERN School of Computing 2023
No full textTrack fitting is an everyday repetitive task in the high energy physics detector reconstruction chains. The precision and stability of the fitter depend on the available computing resources. A fit might cost up to half of the CPU time, that is spent on reconstruction. Kalman filters are a widespread solution for the track fitting. A classical Kalman filter is a powerful tool, that is applicable to the linear problems with Gaussian-like errors. However, in reality one has to deal with non-linear problems and sometimes with non-Gaussian errors. The numerical overheat results in instabilities and slows down the convergence. Physics and reparametrisation can help to improve the fit performance. Starting from the simple Kalman filter, we build up a more realistic Kalman filter, discussing practical tricks and possible issues of implementation. We then talk about implementation differences if using CPU or GPU.
In these two lectures, we start from the points on planes and follow the entire track-fitting chain up to the high-level particle parameters. We discuss the connection between the geometry of the detector and the track model, as well as, the track-fitting chain. We also discuss physics-driven optimization of the algorithms based on the effect of the changes on the high-level parameters.
In the end, we discuss possible implementations of track fitting on CPU and GPU, highlighting the importance of a trade-off between speed and precision
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