scholarly journals Event Reconstruction

2020 ◽  
pp. 23-31
Author(s):  
Rudolf Frühwirth ◽  
Are Strandlie
Keyword(s):  
Particle Identification ◽  
Object Reconstruction ◽  
Track Reconstruction ◽  
Missing Energy ◽  
Local Reconstruction ◽  
Event Reconstruction ◽  
Global Reconstruction ◽  
Vertex Reconstruction

AbstractThe chapter gives an outline of the event reconstruction chain of a typical large experiment, from the trigger to the physics object reconstruction. The concept of the trigger is illustrated by two examples, CMS and LHCb, followed by a discussion of track reconstruction and its stages: hit generation, local reconstruction, and global reconstruction. The section on vertex reconstruction introduces a classification of vertices and sets the scene for the dedicated chapters on vertex finding and vertex fitting. The chapter concludes with some remarks on particle identification and reconstruction of physics objects such as electrons, muons, photons, jets,τleptons, and missing energy.

scholarly journals First Demonstration of a Pixelated Charge Readout for Single-Phase Liquid Argon Time Projection Chambers

Instruments ◽  
2020 ◽  
Vol 4 (1) ◽  
pp. 9 ◽  
Author(s):  
Jonathan Asaadi ◽  
Martin Auger ◽  
Antonio Ereditato ◽  
Damian Goeldi ◽  
Umut Kose ◽  
...  
Keyword(s):  
Single Phase ◽  
Signal To Noise Ratio ◽  
Liquid Argon ◽  
Track Reconstruction ◽  
3D Tracking ◽  
3D Space ◽  
Time Projection Chambers ◽  
Event Reconstruction ◽  
Phase Liquid ◽  
Time Projection

Traditional charge readout technologies of single-phase Liquid Argon Time projection Chambers (LArTPCs) based on projective wire readout introduce intrinsic ambiguities in event reconstruction. Combined with the slow response inherent in LArTPC detectors, reconstruction ambiguities have limited their performance, until now. Here, we present a proof of principle of a pixelated charge readout that enables the full 3D tracking capabilities of LArTPCs. We characterize the signal-to-noise ratio of charge readout chain to be about 14, and demonstrate track reconstruction on 3D space points produced by the pixel readout. This pixelated charge readout makes LArTPCs a viable option for high-multiplicity environments.

scholarly journals On the Possible Detection of Massive Stable Exotic Particles at the LHC

1997 ◽  
Vol 12 (29) ◽  
pp. 2213-2222 ◽  
Author(s):  
Aleandro Nisati ◽  
Silvano Petrarca ◽  
Giorgio Salvini
Keyword(s):  
Hadronic Colliders ◽  
Atlas Detector ◽  
Particle Identification ◽  
High Luminosity ◽  
Track Reconstruction ◽  
Ionization Loss ◽  
Exotic Particles ◽  
Present Design ◽  
Good Measurement ◽  
Interesting Class

The possible detection of massive quasi-stable exotic particles at the high luminosity hadronic colliders is discussed. In this decade, the LHC, now under preparation, has the best opportunity to observe them at the TeV scale. The present design of the ATLAS detector, that has been almost irreversibly decided, may turn out to be flexible enough to allow the detection of this interesting class of exotic particles. The trigger acceptance, the track reconstruction and the particle identification are studied. The necessity of a good measurement of the ionization loss in the muon sector of the detectors is recommended.

scholarly journals Local reconstruction algorithms in the cathode strip chambers of CMS

2019 ◽  
Vol 214 ◽  
pp. 02014
Author(s):  
Mirena Paneva
Keyword(s):  
High Rate ◽  
Reconstruction Algorithms ◽  
Ionization Detector ◽  
Forward Region ◽  
Local Reconstruction ◽  
Straight Line ◽  
Gas Ionization ◽  
Cathode Strip ◽  
Global Reconstruction ◽  
New Algorithms

The design of the CMS detector is optimized for muon measurements. The muon system consists of gas ionization detector technologies. Cathode Strip Chambers (CSC) with both tracking and triggering capabilities are installed in the forward region. The first stage of muon reconstruction uses information from individual muon chambers and is thus called local reconstruction, in contrast to a subsequent global reconstruction where the information from all detectors is combined. First, 2-dimensional spatial points (rechits) describing where a muon crosses the CSC layers are built from the electrical signals induced by the charged particle traversing the chamber. Next, from the reconstructed hits, straight-line track segments are built within each chamber. Local reconstruction becomes particularly challenging at high instantaneous luminosities, which are expected at the HL-LHC. The high rate of particles traversing the detectors leads to increased rate of spurious rechits and segments thus increasing the combinatorial backgrounds. In this respect, work on improving the current and developing new algorithms is essential and is in progress. This document presents the existing local reconstruction algorithms used in the CMS cathode strip chambers. Their performance as well as ongoing efforts towards HL-LHC improvements are discussed.

scholarly journals Time-based Reconstruction of Free-streaming Data in CBM

2018 ◽  
Vol 173 ◽  
pp. 04002
Author(s):  
Valentina Akishina ◽  
Ivan Kisel ◽  
Iouri Vassiliev ◽  
Maksym Zyzak
Keyword(s):  
Kalman Filter ◽  
Cellular Automaton ◽  
Target Position ◽  
Streaming Data ◽  
Filter Method ◽  
Track Reconstruction ◽  
Large Computer ◽  
Event Reconstruction ◽  
Kalman Filter Method ◽  
Particle Reconstruction

Traditional latency-limited trigger architectures typical for conventional experiments are inapplicable for the CBM experiment. Instead, CBM will ship and collect time-stamped data into a readout buffer in a form of a time-slice of a certain length and deliver it to a large computer farm, where online event reconstruction and selection will be performed. Grouping measurements into physical collisions must be performed in software and requires reconstruction not only in space, but also in time, the so-called 4-dimensional track reconstruction and event building. The tracks, reconstructed with 4D Cellular Automaton track finder, are combined into event-corresponding clusters according to the estimated time in the target position and the errors, obtained with the Kalman Filter method. The reconstructed events are given as inputs to the KF Particle Finder package for short-lived particle reconstruction. The results of time-based reconstruction of simulated collisions in CBM are presented and discussed in details.

scholarly journals The CMS High Granularity Calorimeter for HL-LHC

2018 ◽  
Vol 46 ◽  
pp. 1860075
Author(s):  
L. Mastrolorenzo
Keyword(s):  
Fine Structure ◽  
Large Fraction ◽  
Particle Identification ◽  
Particle Flow ◽  
Radiation Tolerance ◽  
High Luminosity ◽  
Good Energy Resolution ◽  
Silicon Sensors ◽  
Event Reconstruction ◽  
Good Energy

The High Luminosity LHC (HL-LHC) will integrate 10 times more luminosity than the LHC, posing significant challenges for radiation tolerance and event pileup on detectors, especially for forward calorimetry, and hallmarks the issue for future colliders. As part of its HL-LHC upgrade program, the CMS Collaboration is designing a High Granularity Calorimeter (HGCAL) to replace the existing endcap calorimeters. It features unprecedented transverse and longitudinal segmentation for both electromagnetic (CE-E) and hadronic (CE-H) compartments. This will facilitate particle-flow (PF) calorimetry, where the fine structure of showers can be measured and used to enhance pileup rejection and particle identification, whilst still achieving good energy resolution. The CE-E and a large fraction of CE-H will be based on hexagonal silicon sensors of [Formula: see text] cell size, with the remainder of the CE-H based on highly-segmented scintillators with SiPM readout. The intrinsic high-precision timing capabilities of the silicon sensors will add an extra dimension to event reconstruction, especially in terms of pileup rejection. An overview of the HGCAL project is presented in this paper.

scholarly journals Catch and Prolong: recurrent neural network for seeking track-candidates

2019 ◽  
Vol 201 ◽  
pp. 05001 ◽  
Author(s):  
Dmitriy Baranov ◽  
Gennady Ososkov ◽  
Pavel Goncharov ◽  
Andrei Tsytrinov
Keyword(s):  
Neural Network ◽  
Recurrent Neural Network ◽  
Nuclear Physics ◽  
High Energy ◽  
Track Reconstruction ◽  
Reconstruction Procedure ◽  
Event Reconstruction ◽  
Pass Through ◽  
Two Stages ◽  
Set Of Points

One of the most important problems of data processing in high energy and nuclear physics is the event reconstruction. Its main part is the track reconstruction procedure which consists in looking for all tracks that elementary particles leave when they pass through a detector among a huge number of points, so-called hits, produced when flying particles fire detector coordinate planes. Unfortunately, the tracking is seriously impeded by the famous shortcoming of multiwired, strip and GEM detectors due to appearance in them a lot of fake hits caused by extra spurious crossings of fired strips. Since the number of those fakes is several orders of magnitude greater than for true hits, one faces with the quite serious difficulty to unravel possible track-candidates via true hits ignoring fakes. We introduce a renewed method that is a significant improvement of our previous two-stage approach based on hit preprocessing using directed K-d tree search followed a deep neural classifier. We combine these two stages in one by applying recurrent neural network that simultaneously determines whether a set of points belongs to a true track or not and predicts where to look for the next point of track on the next coordinate plane of the detector. We show that proposed deep network is more accurate, faster and does not require any special preprocessing stage. Preliminary results of our approach for simulated events of the BM@N GEM detector are presented.

scholarly journals Anti- and Hyper-Nuclei Production at the LHC with ALICE

Proceedings ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 47
Author(s):  
Luca Barioglio
Keyword(s):  
High Energy Physics ◽  
Hadron Collider ◽  
Theoretical Models ◽  
High Energy ◽  
Particle Identification ◽  
Track Reconstruction ◽  
Alice Experiment ◽  
Proton Proton ◽  
Open Question ◽  
Production Mechanisms

At the Large Hadron Collider (LHC) a significant production of (anti-)(hyper-)nuclei is observed in proton-proton (pp), proton-lead (p-Pb) and lead-lead (Pb-Pb) collisions. The measurement of the production yields of light (anti-)nuclei is extremely important to provide insight into the production mechanisms of nuclear matter, which is still an open question in high energy physics. The outstanding particle identification (PID) capabilities of the ALICE detectors allow the identification of rarely produced particles such as deuterons, 3 He and their antiparticles. From the production spectra measured for light (anti-)nuclei with ALICE, the key observables of the production mechanisms (antimatter/matter ratio, coalescence parameter, nuclei/protons ratio) are computed and compared with the available theoretical models. Another open question is the determination of the hypertriton lifetime: published experimental values show a lifetime shorter than the expected one, which should be close to that of the free Λ hyperon. Thanks to the high-resolution track reconstruction capabilities of the ALICE experiment, it has been possible to determine the hypertriton lifetime at the highest Pb-Pb collisions energy with the highest precision ever reached.

scholarly journals A track finding algorithm for the inner tracking system of MPD/NICA

2019 ◽  
Vol 204 ◽  
pp. 07006 ◽  
Author(s):  
Dmitry Zinchenko ◽  
Eduard Nikonov ◽  
Alexander Zinchenko
Keyword(s):  
Tracking System ◽  
Simulated Data ◽  
Secondary Vertex ◽  
Track Reconstruction ◽  
Interaction Point ◽  
Inner Tracking System ◽  
Pixel Sensors ◽  
First Results ◽  
Vertex Reconstruction

An inner tracking system (ITS) based on silicon pixel sensors is currently considered as one of the possible MPD upgrade steps. The main purpose of the new detector is to provide a better precision of the primary and secondary vertex reconstruction and improve track reconstruction in MPD in the region close to the interaction point. To study the ITS performance a new track finding algorithm was developed, which better takes into account the new system’s advantages. In this paper the new algorithm is described and first results obtained on simulated data are presented.

scholarly journals On the challenges of searching for GeV-scale long-lived particles at the LHC

2021 ◽  
Vol 2021 (4) ◽  
Author(s):  
Elias Bernreuther ◽  
Juliana Carrasco Mejia ◽  
Felix Kahlhoefer ◽  
Michael Krämer ◽  
Patrick Tunney
Keyword(s):  
Dark Matter ◽  
Higgs Boson ◽  
Dark Sector ◽  
Missing Energy ◽  
Exotic Mesons ◽  
Strongly Interacting ◽  
Low Mass ◽  
Vertex Reconstruction ◽  
Low Efficiency

Abstract Many models of dark matter predict long-lived particles (LLPs) that can give rise to striking signatures at the LHC. Existing searches for displaced vertices are however tailored towards heavy LLPs. In this work we show that this bias severely affects their sensitivity to LLPs with masses at the GeV scale. To illustrate this point we consider two dark sector models with light LLPs that decay hadronically: a strongly-interacting dark sector with long-lived exotic mesons, and a Higgsed dark sector with a long-lived dark Higgs boson. We study the sensitivity of an existing ATLAS search for displaced vertices and missing energy in these two models and find that current track and vertex cuts result in very low efficiency for light LLPs. To close this gap in the current search programme we suggest two possible modifications of the vertex reconstruction and the analysis cuts. We calculate projected exclusion limits for these modifications and show that they greatly enhance the sensitivity to LLPs with low mass or short decay lengths.

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