The CMS tracking code is organized in several levels, known as ‘iterative steps’, each optimized to reconstruct a class of particle trajectories, as the ones of particles originating from the primary ...vertex or displaced tracks from particles resulting from secondary vertices. Each iterative step consists of seeding, pattern recognition and fitting by a Kalman filter, and a final filtering and cleaning. Each subsequent step works on hits not yet associated to a reconstructed particle trajectory. The CMS tracking code underwent a major upgrade deployed in two phases. It was needed to make the reconstruction computing load compatible with the increasing instantaneous luminosity of LHC, resulting in a large number of primary vertices and tracks per bunch crossing. The improvements are described. Among the others, the iterative steps have been reorganized and optimized and an iterative step specialized for the reconstruction of photon conversion has been added. The overall impact on reconstruction performances is discussed and the prospects for future applications are given.
The conversion of photons into electron-positron pairs in the detector material is a nuisance in the event reconstruction of high energy physics experiments, since the measurement of the ...electromagnetic component of interaction products results degraded. Nonetheless this unavoidable detector effect can also be extremely useful. The reconstruction of photon conversions can be used to probe the detector material and to accurately measure soft photons that come from radiative decays in heavy flavor physics. In fact a converted photon can be measured with very high momentum resolution by exploiting the excellent reconstruction of charged tracks of a tracking detector as the one of CMS at LHC. The main issue is that photon conversion tracks are difficult to reconstruct for standard reconstruction algorithms. They are typically soft and very displaced from the primary interaction vertex. An innovative seeding technique that exploits the peculiar photon conversion topology, successfully applied in the CMS track reconstruction sequence, is presented. The performances of this technique and the substantial enhancement of photon conversion reconstruction efficiency are discussed. Application examples are given.
In many physics experiments where calorimeters are employed, the requirement of an accurate energy measurement is accompanied by the requirement of very high hadron–electron discrimination power. ...Normally the latter requirement is achieved by designing a high-granularity detector with sufficient depth so that the showers can fully develop. This method has many drawbacks ranging from the high number of electronic channels to the high mass of the detector itself. Some of these drawbacks may in fact severely limit the deployment of such a detector in many experiments, most notably in space-based ones. Another method, proposed by our group and currently under investigation, relies on the use of scintillation detectors which are sensitive to the neutron component of the hadron showers. Here a review of the current status will be presented starting with the simulations performed both with GEANT4 and FLUKA. A small prototype detector has been built and has been tested in a high-energy pion/electron beam behind a “shallow” calorimeter. Results are encouraging and indicate that it is possible to enhance the discrimination power of an existing calorimeter by the addition of a small-mass neutron detector, thus paving the way for better performing astroparticle experiments.
An innovative approach to compact calorimetry in space, NEUCAL Bottai, S.; Castellini, G.; Papini, P. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
05/2010, Letnik:
617, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Neutron emission during the development of hadronic showers can be used to discriminate between electromagnetic and hadronic interacting particles impinging a calorimeter. A neutron detector based on ...a high efficiency ‘active moderator’ is presented and its performance is evaluated with the aid of Monte Carlo simulation.
The CMS Tracker upgrade for HL-LHC Sguazzoni, G.
2023 IEEE Nuclear Science Symposium, Medical Imaging Conference and International Symposium on Room-Temperature Semiconductor Detectors (NSS MIC RTSD),
2023-Nov.-4
Conference Proceeding
The Large Hadron Collider will undergo an enhancement which will smoothly bring the luminosity to about 5-7.5×10 34 cm -2 s -1 in 2029, to possibly deliver an integrated luminosity of 3000-4000fb -1 ...per experiment over a decade.This High Luminosity LHC scenario, HL-LHC, will require an upgrade program of the LHC detectors known as Phase-2 upgrade. The current CMS Strip Tracker, already running beyond design specifications, and CMS Phase-1 Pixel Detector will not be able to survive HL-LHC radiation conditions and to withstand the increased rates. To fully exploit the luminosity and to comply with the highly demanding conditions, CMS is preparing to build completely new improved tracking devices to be installed during the long shutdown in 2026-2028: the Inner Tracker, based on pixel silicon sensors, and the Outer Tracker, based on strip and macropixel silicon sensors.The Inner Tracker ensures high-granularity coverage up to |η|<4 and features the innovative serial powering scheme to minimise the material budget. The Outer Tracker is designed to have trigger capabilities and provide primitives for tracking at L1. To achieve such goals, R&D activities have explored options for both the Inner Tracker and the Outer Tracker.The design choices for the Tracker upgrades are discussed along with some highlights on key factors and technological approaches. The system design is now essentially completed, parts procurement is ongoing and production is imminent.
An excellent hadron to electron discrimination is a crucial aspect of calorimeter-based experiments in astroparticle physics. Standard discrimination techniques require full shower development and ...fine granularity but in space detectors severe limitations exist due to constraints on dimensions, weight and power consumption. A possible approach is to exploit the different neutron yield of electromagnetic and hadronic showers. NEUCAL is a light and compact innovative neutron detector, to be used as an auxiliary complement of electromagnetic calorimeters. This new approach to neutron counting relies on scintillation detectors which are sensitive to the moderation phase of the neutron component. The NEUCAL prototype has been placed after a conventional calorimeter and tested with high energy beams of pions and positrons. The comparison of experimental data with a detailed Geant4 simulation and the encouraging results obtained are presented.
CMS inner tracker detector modules Sguazzoni, Giacomo
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2005, Letnik:
552, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The production of silicon detector modules that will instrument the CMS Inner Tracker has nowadays reached 1300 units out of the approximately 3700 needed in total, with an overall yield close to ...96%. A description of the module design, the assembly procedures and the qualification tests is given. The results of the quality assurance are presented and the experience gained is discussed.
Mesostructural analysis carried out in several localities of western, southern-central and southeastern Iceland shows an unexpectedly frequent occurrence of strike-slip faults parallel to, or lying ...at relatively small angles with, the axis of rifting. Some faults can be interpreted in terms of shear parallel to the rifts, whereas others form conjugate systems referable to rift-parallel compression.
Axial shear can be explained by the accommodation of differences in the directions of tectonic extension between different segments of the axial rift system and subordinately by lateral (rift-parallel) displacements between the major lithospheric plates. Axial compression may be attributable to rift-oblique transform shear or to mantle transport parallel to the spreading axis compensating local deficiencies in mantle upwelling.
The data regard 1974 fault surfaces, mainly small-scale.
Searches for R-parity conserving supersymmetric particles have been performed in e
+e
− data collected by LEP detectors, at centre-of-mass energies up to 209 GeV, corresponding to an integrated ...luminosity of ∼3.1 fb
−1. The results and their interpretation in the context of MSSM frameworks are briefly reviewed.
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