5,384 research outputs found
Upgrade of the CMS muon system with triple-GEM detectors
No full textThe CMS collaboration considers upgrading the muon forward region which is particularly affected by the high-luminosity conditions at the LHC. The proposal involves Gas Electron Multiplier (GEM) chambers, which are able to handle the extreme particle rates expected in this region along with a high spatial resolution. This allows to combine tracking and triggering capabilities, which will improve the CMS muon High Level Trigger, the muon identification and the track reconstruction. Intense R&D has been going on since 2009 and it has lead to the development of several GEM prototypes and associated detector electronics. These GEM prototypes have been subjected to extensive tests in the laboratory and in test beams at the CERN Super Proton Synchrotron (SPS). This contribution will review the status of the CMS upgrade project with GEMs and its impact on the CMS performance
The CMS statistical analysis and combination tool: COMBINE
No full textThis paper describes the Combine software package used for statistical analyses by the CMS Collaboration. The package, originally designed to perform searches for a Higgs boson and the combined analysis of those searches, has evolved to become the statistical analysis tool presently used in the majority of measurements and searches performed by the CMS Collaboration. It is not specific to the CMS experiment, and this paper is intended to serve as a reference for users outside of the CMS Collaboration, providing an outline of the most salient features and capabilities. Readers are provided with the possibility to run Combine and reproduce examples provided in this paper using a publicly available container image. Since the package is constantly evolving to meet the demands of ever-increasing data sets and analysis sophistication, this paper cannot cover all details of Combine. However, the online documentation referenced within this paper provides an up-to-date and complete user
guide
Data Quality Monitoring and Performance Studies of the Resistive Plate Chamber Detector at the CMS Experiment at LHC.
No full textThe CMS detector is a sophisticated and massive system: 7 different detector technologies, a high number of front-end electronic channels (10^7) , an input rate of 10^9 interactions per second, a trigger able to reduce the frequency by a factor 10^5, and online computer farms with a storage capability rates of about 10^2 MB/s. CMS is foreseen to take data, with high efficiency, for
over 15 years. Clearly, assuring pristine and stable behavior of each of its components is critical and delicate task.
The CMS collaboration designed and built, in tandem with detector commissioning, a high-level Data Quality Monitoring (DQM) system for the reliable certification of recorded data for physics analyses. DQM debugs hardware, monitors detector and trigger performance behavior, and highlight problems or malfunctioning by processing calibration and physics data.
Definition of the requirements, design, and development of the RPC DQM system, as well as its use to study detector and trigger performance, have been the focus of this doctoral thesis work
Stand-alone cosmic muon reconstruction before installation of the CMS silicon strip tracker
No full textThis is the Pre-print version of the Article. The official published version can be accessed from the link below - Copyright @ 2009 IOPThe subsystems of the CMS silicon strip tracker were integrated and commissioned at the Tracker Integration Facility (TIF) in the period from November 2006 to July 2007. As part of the commissioning, large samples of cosmic ray data were recorded under various running conditions in the absence of a magnetic field. Cosmic rays detected by scintillation counters were used to trigger the readout of up to 15 % of the final silicon strip detector, and over 4.7 million events were recorded. This document describes the cosmic track reconstruction and presents results on the performance of track and hit reconstruction as from dedicated analyses.This work was supported by: the Austrian
Federal Ministry of Science and Research; the Belgium Fonds de la Recherche Scientifique and Fonds voorWetenschappelijk
Onderzoek; the Academy of Finland and Helsinki Institute of Physics; the Institut National de Physique Nucleaire et de Physique des Particules / CNRS, France; the Bundesministerium fur Bildung und Forschung, Germany; the Istituto Nazionale di Fisica Nucleare, Italy; the Swiss Funding Agencies; the Science and Technology Facilities Council, UK; the US Department of Energy, and National Science Foundation. Individuals have received support from the Marie-Curie IEF program (European Union) and the A.P. Sloan Foundation
CMS tracking performance results from early LHC operation
No full textThis is the Pre-print version of the Article. The official published version of the Paper can be accessed from the link below - Copyright @ 2010 Sringer VerlagThe first LHC pp collisions at centre-of-mass energies of 0.9 and 2.36 TeV were recorded by the CMS detector in December 2009. The trajectories of charged particles produced in the collisions were reconstructed using the all-silicon Tracker and their momenta were measured in the 3.8 T axial magnetic field. Results from the Tracker commissioning are presented including studies of timing, efficiency, signal-to-noise, resolution, and ionization energy. Reconstructed tracks are used to benchmark the performance in terms of track and vertex resolutions, reconstruction of decays, estimation of ionization energy loss, as well as identification of photon conversions, nuclear interactions, and heavy-flavour decays
Performance studies of the CMS strip tracker before installation
No full textThis is the Pre-print version of the Article. The official published version can be accessed from the link below - Copyright @ 2009 IOPIn March 2007 the assembly of the Silicon Strip Tracker was completed at the Tracker Integration Facility at CERN. Nearly 15% of the detector was instrumented using cables, fiber optics, power supplies, and electronics intended for the operation at the LHC. A local chiller was used to circulate the coolant for low temperature operation. In order to understand the efficiency and alignment of the strip tracker modules, a cosmic ray trigger was implemented. From March through July 4.5 million triggers were recorded. This period, referred to as the Sector Test, provided practical experience with the operation of the Tracker, especially safety, data acquisition, power, and cooling systems. This paper describes the performance of the strip system during the Sector Test, which consisted of five distinct periods defined by the coolant temperature. Significant emphasis is placed on comparisons between the data and results from Monte Carlo studies.This work was supported by: the Austrian
Federal Ministry of Science and Research; the Belgium Fonds de la Recherche Scientifique and Fonds voorWetenschappelijk
Onderzoek; the Academy of Finland and Helsinki Institute of Physics; the Institut National de Physique Nucleaire et de Physique des Particules / CNRS, France; the Bundesministerium f¨ur Bildungund Forschung, Germany; the Istituto Nazionale di Fisica Nucleare, Italy; the Swiss Funding Agencies; the Science and Technology Facilities Council, UK; the US Department of Energy, and National Science Foundation. Individuals have received support from the Marie-Curie IEF program (European Union) and the A.P. Sloan Foundation
A deep neural network to search for new long-lived particles decaying to jets
No full textA tagging algorithm to identify jets that are significantly displaced from the proton-proton (pp) collision region in the CMS detector at the LHC is presented. Displaced jets can arise from the decays of long-lived particles (LLPs), which are predicted by several theoretical extensions of the standard model. The tagger is a multiclass classifier based on a deep neural network, which is parameterised according to the proper decay length ct 0 of the LLP. A novel scheme is defined to reliably label jets from LLP decays for supervised learning. Samples of pp collision data, recorded by the CMS detector at a centre-of-mass energy of 13 TeV, and simulated events are used to train the neural network. Domain adaptation by backward propagation is performed to improve the simulation modelling of the jet class probability distributions observed in pp collision data. The potential performance of the tagger is demonstrated with a search for long-lived gluinos, a manifestation of split supersymmetric models. The tagger provides a rejection factor of 10 000 for jets from standard model processes, while maintaining an LLP jet tagging efficiency of 30%-80% for gluinos with 1 mm≤ct 0≤ 10 m. The expected coverage of the parameter space for split supersymmetry is presented
Author Correction: A portrait of the Higgs boson by the CMS experiment ten years after the discovery (Nature, (2022), 607, 7917, (60-68), 10.1038/s41586-022-04892-x)
No full textCorrection to: Nature Published online 4 July 2022 In the version of this article initially published, CMS Collaboration author names, affiliations and acknowledgements were omitted and have now been included in the HTML and PDF versions of the article.SCOAP
Enriching the physics program of the CMS experiment via data scouting and data parking
No full textSpecialized data-taking and data-processing techniques were introduced by the CMS experiment in Run 1 of the CERN LHC to enhance the sensitivity of searches for new physics and the precision of standard model measurements. These techniques, termed data scouting and data parking, extend the data-taking capabilities of CMS beyond the original design specifications. The novel data-scouting strategy trades complete event information for higher event rates, while keeping the data bandwidth within limits. Data parking involves storing a large amount of raw detector data collected by algorithms with low trigger thresholds to be processed when sufficient computational power is available to handle such data. The research program of the CMS Collaboration is greatly expanded with these techniques. The implementation, performance, and physics results obtained with data scouting and data parking in CMS over the last decade are discussed in this Report, along with new developments aimed at further improving low-mass physics sensitivity over the next years of data taking
CMS technical design report, volume II: Physics performance
No full textCMS is a general purpose experiment, designed to study the physics of pp collisions at 14 TeV at the Large Hadron Collider (LHC). It currently involves more than 2000 physicists from more than 150 institutes and 37 countries. The LHC will provide extraordinary opportunities for particle physics based on its unprecedented collision energy and luminosity when it begins operation in 2007.
The principal aim of this report is to present the strategy of CMS to explore the rich physics programme offered by the LHC. This volume demonstrates the physics capability of the CMS experiment. The prime goals of CMS are to explore physics at the TeV scale and to study the mechanism of electroweak symmetry breaking—through the discovery of the Higgs particle or otherwise. To carry out this task, CMS must be prepared to search for new particles, such as the Higgs boson or supersymmetric partners of the Standard Model particles, from the start-up of the LHC since new physics at the TeV scale may manifest itself with modest data samples of the order of a few fb-1 or less.
The analysis tools that have been developed are applied to study in great detail and with all the methodology of performing an analysis on CMS data specific benchmark processes upon which to gauge the performance of CMS. These processes cover several Higgs boson decay channels, the production and decay of new particles such as Z' and supersymmetric particles, Bs production and processes in heavy ion collisions. The simulation of these benchmark processes includes subtle effects such as possible detector miscalibration and misalignment. Besides these benchmark processes, the physics reach of CMS is studied for a large number of signatures arising in the Standard Model and also in theories beyond the Standard Model for integrated luminosities ranging from 1 fb-1 to 30 fb-1. The Standard Model processes include QCD, B-physics, diffraction, detailed studies of the top quark properties, and electroweak physics topics such as the W and Z0 boson properties. The production and decay of the Higgs particle is studied for many observable decays, and the precision with which the Higgs boson properties can be derived is determined. About ten different supersymmetry benchmark points are analysed using full simulation. The CMS discovery reach is evaluated in the SUSY parameter space covering a large variety of decay signatures. Furthermore, the discovery reach for a plethora of alternative models for new physics is explored, notably extra dimensions, new vector boson high mass states, little Higgs models, technicolour and others. Methods to discriminate between models have been investigated.
This report is organized as follows. Chapter 1, the Introduction, describes the context of this document. Chapters 2–6 describe examples of full analyses, with photons, electrons, muons, jets, missing ET, B-mesons and tau’s, and for quarkonia in heavy ion collisions. Chapters 7–15 describe the physics reach for Standard Model processes, Higgs discovery and searches for new physics beyond the Standard Model
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