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At least 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Combination of Measurements of the Top Quark Mass from Data Collected by the ATLAS and CMS Experiments at s = 7 and 8 TeV

A combination of fifteen top quark mass measurements performed by the ATLAS and CMS experiments at the LHC is presented. The datasets used correspond to an integrated luminosity of up to 5 and 20 fb − 1 of proton-proton collisions at center-of-mass energies of 7 and 8 TeV, respectively. The combination includes measurements in top quark pair events that exploit both the semileptonic and hadronic decays of the top quark, and a measurement using events enriched in single top quark production via the electroweak t channel. The combination accounts for the correlations between measurements and achieves an improvement in the total uncertainty of 31% relative to the most precise input measurement. The result is m t = 172.52 ± 0.14 ( stat ) ± 0.30 ( syst ) GeV , with a total uncertainty of 0.33 GeV. © 2024 CERN, for the CMS and ATLASs Collaboration 2024 CERN

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Isolating Unisolated Upsilons with Anomaly Detection in CMS Open Data

We present the first study of anti-isolated Upsilon decays to two muons (ϒ→𝜇⁺⁢𝜇⁻) in proton-proton collisions at the Large Hadron Collider. Using a machine learning (ML)-based anomaly detection strategy, we “rediscover” the ϒ in 13 TeV CMS Open Data from 2016, despite overwhelming anti-isolated backgrounds. We elevate the signal significance to 6.4⁢𝜎 using these methods, starting from 1.6⁢𝜎 using the dimuon mass spectrum alone. Moreover, we demonstrate improved sensitivity from using an ML-based estimate of the multifeature likelihood compared to traditional “cut-and-count” methods. This is the first ever detection of anti-isolated Upsilons, which can be useful in the study of heavy-flavor fragmentation in quantum chromodynamics. Our Letter demonstrates that it is possible and practical to find real signals in experimental collider data using ML-based anomaly detection, and we distill a readily accessible benchmark dataset from the CMS Open Data to facilitate future anomaly detection developments.

machine learning↗
DOE OSTI2025

ETROC2 as the Final Version for CMS MTD Endcap Timing Layer (ETL) Upgrade

The ETROC2 is the first full-size full-functionality prototype design fully compatible with the final chip specifications for CMS ETL. The ETROC2 chips have been extensively tested and the results have been presented at IEEE NSS MIC RTSD 2024. We will present here new results including the bump bonding yield improvement study, the time walk correction (TWC) generality study with single pixel TWC applied to all pixels, the final SEU testing results using both heavy ion and proton beam, more beam test studies including different sensors and irradiated sensors, and readiness for the ETROC2 production for CMS ETL upgrade.

Liu, Tie Hui [Fermilab] (ORCID:0009000765225605)↗
DOE OSTI2016

Development of flexible, scalable, low cost readout for beam tests of the high granularity calorimeter for the CMS endcap

As part of the development of the High Granularity Calorimeter for the CMS Endcap at HL-LHC, The CMS collaboration is conducting a comprehensive series of beam tests. The first beam test, with a single HGC module was carried out in March of 2016 at the Fermilab Test Beam Facility, continuing to a 16 module test in July of 2016. We describe here the development of a low cost readout system that is simple to implement and is able to grow with the system under test. The system is based on the low cost Zynq SoC that allows simple DAQ development in a Linux environment. For this application we used the Digilent ZedBoard, which allows high speed LVDS links and Linux software development on a single commercial board. A small custom FPGA board designed to comply with the VITA 57 Field Programmable Mezzanine Card standard implements the interface to the readout ASIC mounted on the HGC sensor modules and provides the LVDS links to the ZedBoard, either directly over the FMC connector or via a custom carrier card. This architecture provides scalability, ease of development and low cost.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

Investigation of fast timing capabilities of silicon sensors for the CMS high granularity calorimeter at HL-LHC

The High Granularity Calorimeter (HGCAL) is the technology choice of the CMS collaboration for the endcap calorimetry upgrade planned to cope with the harsh radiation and unprecedented in-time event pileup projected at the High Luminosity-LHC era. In this context, profiting from fast-timing information with a resolution of a few tens of picoseconds embedded in the calorimeter would represent a unique capability for resolving information from individual collisions at the HL-LHC. This will enhance the reconstruction and physics capabilities of the CMS detector in terms of pileup mitigation and particle identification. The HGCAL is realized as a sampling calorimeter that uses silicon sensors as its active elements. Prototype sensors were tested with high-energy electron beams at the CERN SPS, and at the FNAL FTBF test beam facilities. We present the motivation for this studies including the concept and use of fast-timing in the HGCAL, and the measured intrinsic timing capabilities of silicon sensors for electromagnetic showers and minimum-ionizing particles.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2021

Precision luminosity measurement in proton–proton collisions at $\sqrt{s}$ = 13 TeV in 2015 and 2016 at CMS

The measurement of the luminosity recorded by the CMS detector installed at LHC interaction point 5, using proton–proton collisions at √s = 13 TeV in 2015 and 2016, is reported. The absolute luminosity scale is measured for individual bunch crossings using beam-separation scans (the van der Meer method), with a relative precision of 1.3 and 1.0% in 2015 and 2016, respectively. The dominant sources of uncertainty are related to residual differences between the measured beam positions and the ones provided by the operational settings of the LHC magnets, the factorizability of the proton bunch spatial density functions in the coordinates transverse to the beam direction, and the modeling of the effect of electromagnetic interactions among protons in the colliding bunches. When applying the van der Meer calibration to the entire run periods, the integrated luminosities when CMS was fully operational are 2.27 and 36.3 fb -1 in 2015 and 2016, with a relative precision of 1.6 and 1.2%, respectively. These are among the most precise luminosity measurements at bunched-beam hadron colliders.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

CMS PYTHIA 8 colour reconnection tunes based on underlying-event data

New sets of parameter tunes for two of the colour reconnection models, quantum chromodynamics-inspired and gluon-move, implemented in the PYTHIA 8 event generator, are obtained based on the default CMS PYTHIA 8 underlying-event tune, CP5. Measurements sensitive to the underlying event performed by the CMS experiment at centre-of-mass energies $\sqrt{s}=$7 and 13 TeV, and by the CDF experiment at 1.96 TeV are used to constrain the parameters of colour reconnection models and multiple-parton interactions simultaneously. The new colour reconnection tunes are compared with various measurements at 1.96, 7, 8, and 13 TeV including measurements of the underlying-event, strange-particle multiplicities, jet substructure observables, jet shapes, and colour flow in top quark pair ($t\bar{t}$) events. The new tunes are also used to estimate the uncertainty related to colour reconnection modelling in the top quark mass measurement using the decay products of $t\bar{t}$ events in the semileptonic channel at 13 TeV .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Luminosity determination using Z boson production at the CMS experiment

The measurement of Z boson production is presented as a method to determine the integrated luminosity of CMS data sets. The analysis uses proton–proton collision data, recorded by the CMS experiment at the CERN LHC in 2017 at a center-of-mass energy of 13 TeV. Events with Z bosons decaying into a pair of muons are selected. The total number of Z bosons produced in a fiducial volume is determined, together with the identification efficiencies and correlations from the same data set, in small intervals of 20 pb –1 of integrated luminosity, thus facilitating the efficiency and rate measurement as a function of time and instantaneous luminosity. Using the ratio of the efficiency-corrected numbers of Z bosons, the precisely measured integrated luminosity of one data set is used to determine the luminosity of another. For the first time, a full quantitative uncertainty analysis of the use of Z bosons for the integrated luminosity measurement is performed. The uncertainty in the extrapolation between two data sets, recorded in 2017 at low and high instantaneous luminosity, is less than 0.5%. We show that the Z boson rate measurement constitutes a precise method, complementary to traditional methods, with the potential to improve the measurement of the integrated luminosity.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2024

Measurement of the background in the CMS muon detector in ${p}{p}$-collisions at $\sqrt{s} = 13$ TeV

The CMS detector, including its muon system, has been operating at the CERN LHC in increasingly challenging conditions for about 15 years. The muon detector was designed to provide excellent triggering and track reconstruction for muons produced in proton–proton collisons at an instantaneous luminosity ($\mathcal{L}$) of 1 x 10 34 cm –2 s –1 . During the Run 2 data-taking period (2015–2018), the LHC achieved an instantaneous luminosity of twice its design value, resulting in larger background rates and making the efficient detection of muons more difficult. While some backgrounds result from natural radioactivity, cosmic rays, and interactions of the circulating protons with residual gas in the beam pipe, the dominant source of background hits in the muon system arises from proton–proton interactions themselves. Charged hadrons leaving the calorimeters produce energy deposits in the muon chambers. In addition, high-energy particles interacting in the hadron calorimeter and forward shielding elements generate thermal neutrons, which leak out of the calorimeter and shielding structures, filling the CMS cavern. We describe the method used to measure the background rates in the various muon subsystems. These rates, in conjunction with simulations, can be used to estimate the expected backgrounds in the High-Luminosity LHC. This machine will run for at least 10 years starting in 2029 reaching an instantaneous luminosity of $\mathcal{L}$ = 5 x 10 34 cm –2 s –1 and increasing ultimately to $\mathcal{L}$ = 7.5 x 10 34 cm –2 s –1 . These background estimates have been a key ingredient for the planning and design of the muon detector upgrade.

Tytgat, M. (ORCID:0000000239902074)↗
DOE OSTI2019

R&D for new silicon pixel sensors for the High Luminosity phase of the CMS experiment at LHC

The High Luminosity upgrade of the CERN LHC collider (HL-LHC) demands a new high-radiation–tolerant solid-state pixel sensor capable of surviving fluencies up to a few 10$^{16} n_{eq}/\mathrm{cm}^2$ at ~ 3 cm from the interaction point. To this extent the INFN ATLAS-CMS joint research activity, in collaboration with Fondazione Bruno Kessler (FBK), is aiming at the development of thin n -in- p –type pixel sensors for the HL-LHC. The R&D covers both planar and single-sided 3D columnar pixel devices made with the Si-Si Direct Wafer Bonding technique, which allows for the production of sensors with 100 μm and 130 μm active thickness for planar sensors, and 130 μm for 3D sensors, the thinnest ones ever produced so far. The first prototypes of hybrid modules, bump-bonded to the present CMS readout chip, have been tested on beam. The first results on their performance before and after irradiation are presented

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2025

AmeriFlux FLUXNET-1F US-Cms Central Marsh

This is the AmeriFlux Management Project (AMP) created FLUXNET-1F version of the carbon flux data for the site US-Cms Central Marsh. This is the FLUXNET version of the carbon flux data for the site US-Cms Central Marsh produced by applying the standard ONEFlux (1F) software. Site Description - This tower is located near Central Marsh, Barrow. The wet sedge is dominated on permafrost.

Miyata, Akira [National Agriculture and Food Resea↗
DOE OSTI2016

A search for long-lived particles that stop in the CMS detector and decay to muons

A search for long-lived particles that are produced in proton-proton collisions at the CERN LHC, come to rest in the CMS detector, and decay to muons is presented. The decays of the stopped particles could be observed during the intervals between LHC beam crossings, at times that are well separated from any proton-proton collisions. The analysis uses 19.7 1/fb of 8 TeV data collected by CMS in 2012, during a search interval of 293 hours of trigger livetime. Massive, long-lived particles do not exist in the Standard Model, and so any sign of them would be an indication of new physics. The results are interpreted with a model that predicts a long-lived particle that has a charge of twice the electron charge and that behaves like a lepton. Cross section limits are set for each long-lived particle mass as a function of lifetime, for lifetimes between 100 ns and 10 days. These are the first limits for long-lived stopped particles that decay to muons.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

High Energy Physics Research with the CMS Experiment at CERN - Energy Frontier Experiment

The Large Hadron Collider (LHC) at the European Organization for Nuclear Research (CERN) near Geneva, Switzerland, is now the highest energy accelerator in the world, colliding protons with protons. On July 4, 2012, the two general-purpose experiments, ATLAS and the Compact Muon Solenoid (CMS) experiment, announced the observation of a particle consistent with the world’s most sought-after particle, the Higgs boson, at a mass of about 125 GeV (approximately 125 times the mass of the proton). The Higgs boson is the final missing ingredient of the standard model, in which it is needed to allow most other particles to acquire mass through the mechanism of electroweak symmetry breaking. We are members of the team in the CMS experiment that found evidence for the Higgs boson through its decay to two photons, the most sensitive channel at the LHC. We are proposing to carry out studies to determine whether the new particle has the properties expected for the standard model Higgs boson or whether it is something else. The new particle can still carry out its role in electroweak symmetry breaking but have other properties as well. Most theorists think that a single standard model Higgs boson cannot be the complete solution – there are other particles needed to answer some of the remaining questions, such as the hierarchy problem. The particle that has been observed could be one of several Higgs bosons, for example, or it could be composite. One model of physics beyond the standard model is supersymmetry, in which every ordinary particle has a superpartner with opposite spin properties. In supersymmetric models, there must be at least five Higgs bosons. In the most popular versions of supersymmetry, the lightest supersymmetric particle does not decay and is a candidate for dark matter. This proposal covers the period from June 1, 2013, to March 31, 2016. During this period the LHC will finally reach its design energy, almost twice the energy at which it now runs. We will be able to study the Higgs boson at the current LHC energy using about three times as much data as were used to make the observation. In 2013 the LHC will shut down to make preparations to run at its design energy in 2015. During the shutdown period, we will be preparing upgrades of the detector to be able to run at the higher rates of proton-proton collisions that will also be possible once the LHC is running at design energy. The upgrade on which we are working, the inner silicon pixel tracker, will be installed in late 2016. Definitive tests of whether the new particle satisfies the properties of the standard model Higgs boson will almost certainly require both the higher energy and the larger amounts of data that can be accumulated using the higher rates. Meanwhile we will use the data taken during 2012 and the higher energy data starting in 2015 to continue to search for beyond-the-standard-model physics such as supersymmetry and heavy neutrinos. We have already made such searches using data since the LHC started running. We are discussing with theorists how a 125-GeV Higgs modifies such models. Finding such particles will probably also require the higher energy and larger amounts of data beginning in 2015. The period of this proposal promises to be very exciting, leading to new knowledge of the matter in the Universe.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Simulation of CMS Phase 2 Pixel Tracker for HL-LHC [Slides]

The High-Luminosity Large Hadron Collider (HL-LHC) aims to increase luminosity by a factor of 10 beyond the LHC's design value. To cope with the increased rate of particle production without compromising physics performance, the LHC detectors will undergo an extensive upgrade. CMS will replace the current inner tracker system with a new silicon tracker which will feature increased forward acceptance, improved radiation hardness, higher granularity, and compatibility with higher data rates. We present a simulation study of the CMS Phase 2 pixel tracker that investigates the expected occupancy and tracking performance for various geometric and sensor granularity options.

43 PARTICLE ACCELERATORS↗
DOE OSTI2018

A Letter of Intent for MATHUSLA: a dedicated displaced vertex detector above ATLAS or CMS.

In this Letter of Intent we propose the construction of MATHUSLA (MAssive Timing Hodoscope for Ultra-Stable neutraL pArticles), a dedicated large-volume displaced vertex detector (DV) for the HL-LHC on the surface above ATLAS or CMS. Such a detector, which can be built using existing technologies with a reasonable budget in time for the HL-LHC upgrade, could search for neutral long-lived particles (LLPs) without trigger limitations and with very low or zero backgrounds, allowing it to probe LLP cross sections and lifetimes up to several orders of magnitude beyond the reach of ATLAS or CMS. MATHUSLA would also act as a cutting-edge cosmic ray telescope at CERN, exploring many open questions in cosmic ray and astro-particle physics.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2019

CMS Patatrack Project [PowerPoint]

This talk presents the technical performance and lessons learned of the Patatrack demonstator, where the CMS pixel local reconstruction and pixel-only track reconstruction have been ported to NVIDIA GPUs. The demonstrator is run within the CMS software framework (CMSSW), and the model of integrating CUDA algorithms to CMSSW is discussed as well.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Ultrarelativistic Heavy-Ion Reactions at the LHC with the CMS Detector

This grant funded the travel to CERN to allow participation in the 2018 PbPb run as part of the Compact Muon Solenoid (CMS) detector collaboration. Among the activities performed were the testing and installation of the spectator reaction plane detector (SRPD). This detector was designed and constructed by the heavy ion group at the University of Maryland. Its purpose is to map the spacial distribution of the spectator neutrons that make it at zero degrees to the Zero Degree Calorimeter (ZDC), located 140 meters from the interaction point of CMS. This will be used to determine the spectator reaction plane for the PbPb collisions. During this heavy ion run at the LHC, there was also the opportunity to participate in a test beam at the CERN SPS. A duplicate copy of the SRPD was used in this test. This report focuses on the results from the test beam.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2019

Transitioning CMS to Rucio Data Management [Slides]

Rucio is a good match for CMS data management needs. Transitioning an operating experiment at this scale is a non-trivial process. CMS has tested Rucio near the LHC Run 3 scale needed. We expect significant benefits from shared code base and operational experience with ATLAS and others. The final transition will occur in 2020. We expect to collaborate on future development which enable Rucio to function in the HL-LHC era.

97 MATHEMATICS AND COMPUTING↗