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At least 1,531 records · Page 85
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DOE OSTI2019

Search for a right-handed gauge boson decaying into a high-momentum heavy neutrino and a charged lepton in p p collisions with the ATLAS detector at s = 13 TeV

CERN-LHC, ATLAS. A search for a right-handed gauge boson WR, decaying into a boosted right-handed heavy neutrino NR, in the framework of Left-Right Symmetric Models is presented. It is based on data from proton-proton collisions with a centre-of-mass energy of 13 TeV collected by the ATLAS detector at the Large Hadron Collider during the years 2015, 2016 and 2017, corresponding to an integrated luminosity of 80 fb−1. The search is performed separately for electrons and muons in the final state. A distinguishing feature of the search is the use of large-radius jets containing electrons. Selections based on the signal topology result in smaller background compared with to expected signal. No significant deviation from the Standard Model prediction is observed and lower limits are set in the WR and NR mass plane. Mass values of the WR smaller than 3.8-5 TeV are excluded for NR in the mass range 0.1-1.8 TeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Search for light long-lived neutral particles produced in p p collisions at s = 13 TeV and decaying into collimated leptons or light hadrons with the ATLAS detector

CERN-LHC. Search for long-lived dark photons produced from the decay of a Higgs boson or a heavy scalar boson and decaying into displaced collimated Standard Model fermions. The search uses data corresponding to an integrated luminosity of 36.1/fb collected in proton-proton collisions at 13 TeV center-of-mass energy and recorded in 2015-2016 with the ATLAS detector at the Large Hadron Collider. The observed number of events is consistent with the expected background, and limits on the production cross section times branching fraction as a function of the proper decay length of the dark photon are reported. Detection efficiency as a function of the proper decay lenght are also reported.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Measurement of angular and momentum distributions of charged particles within and around jets in Pb+Pb and p p collisions at s NN = 5.02 TeV with the ATLAS detector

CERN-LHC. Studies of the fragmentation of jets into charged particles in heavy-ion collisions can provide information about the mechanism of jet-quenching by the hot and dense QCD matter created in such collisions, the quark-gluon plasma. This paper presents a measurement of the angular distribution of charged particles around the jet axis in sNN=5.02 TeV Pb+Pb and pp collisions, using the ATLAS detector at the LHC. The Pb+Pb and pp data sets have integrated luminosities of 0.49 nb−1 and 25 pb−1, respectively. The measurement is performed for jets reconstructed with the anti-kt algorithm with radius parameter R=0.4 and is extended to an angular distance of r=0.8 from the jet axis. Results are presented as a function of Pb+Pb collision centrality and distance from the jet axis for charged particles with transverse momenta in the 1−63 GeV range, matched to jets with transverse momenta in the 126−316 GeV range and an absolute value of jet rapidity of less than 1.7. Modifications to the measured distributions are quantified by taking a ratio to the measurements in pp collisions. Yields of charged particles with transverse momenta below 4 GeV are observed to be increasingly enhanced as a function of angular distance from the jet axis, reaching a maximum at r=0.6. Charged particles with transverse momenta above 4 GeV have an enhanced yield in Pb+Pb collisions in the jet core for angular distances up to r=0.05 from the jet axis, with a suppression at larger distances.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Measurement of jet fragmentation in Pb+Pb and p p collisions at s N N = 5.02 TeV with the ATLAS detector

CERN-LHC. This paper presents a measurement of jet fragmentation functions in 0.49 nb−1 of Pb+Pb collisions and 25 pb−1 of pp collisions at sNN=5.02 TeV collected in 2015 with the ATLAS detector at the LHC. These measurements provide insight into the jet quenching process in the quark-gluon plasma created in the aftermath of ultrarelativistic collisions between two nuclei. The modifications to the jet fragmentation functions are quantified by dividing the measurements in Pb+Pb collisions by baseline measurements in pp collisions. This ratio is studied as a function of the transverse momentum of the jet, the jet rapidity, and the centrality of the collision. In both collision systems, the jet fragmentation functions are measured for jets with transverse momentum between 126 and 398 GeV and with an absolute value of jet rapidity less than 2.1. An enhancement of particles carrying a small fraction of the jet momentum is observed, which increases with centrality and with increasing jet transverse momentum. Yields of particles carrying a very large fraction of the jet momentum are also observed to be enhanced. Between these two enhancements of the fragmentation functions a suppression of particles carrying an intermediate fraction of the jet momentum is observed in Pb+Pb collisions. A small dependence of the modifications on jet rapidity is observed.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Measurement of azimuthal anisotropy of muons from charm and bottom hadrons in p p collisions at s = 13 TeV with the ATLAS detector

CERN-LHC. The elliptic flow of muons from the decay of charm and bottom hadrons is measured in pp collisions at 13 TeV using a data sample with an integrated luminosity of 150 pb^{-1} recorded by the ATLAS detector at the LHC. The muons from heavy-flavor decay are separated from light-hadron decay muons using momentum imbalance between the tracking and muon spectrometers. The heavy-flavor decay muons are further separated into those from charm decay and those from bottom decay using the distance-of-closest-approach to the collision vertex. The measurement is performed for muons in the transverse momentum range 4 < pT < 7 GeV and pseudorapidity range |η|<2.4. A significant non-zero elliptic anisotropy coefficient v2 is observed for muons from charm decays, while the v2 value for muons from bottom decays is consistent with zero within uncertainties.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Search for supersymmetry in events with photons, bottom quarks, and missing transverse momentum in proton–proton collisions at a centre-of-mass energy of 7 TeV with the ATLAS detector

CERN-LHC. Study of events produced in proton-proton collisions at a centre-of-mass energy of 7 Tev which have a final state consisting of an isolated photon with high PT, at least on jet identified as originating from a bottom quark, and high missing PT. The data sample used, collected in 2011, has a total integrated luminsoity of 4.7 fb-1. The results of the search are interpreted in the context of general gauge mediation (GGM).

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Easing the Control System Application Development for CMS Detector Control System with Automatic Production Environment Reproduction

The Detector Control System (DCS) is one of the main pieces involved in the operation of the Compact Muon Solenoid (CMS) experiment at the LHC. The system is built using WinCC Open Architecture (WinCC OA) and the Joint Controls Project (JCOP) framework which was developed on top of WinCC at CERN. Following the JCOP paradigm, CMS has developed its own framework which is structured as a collection of more than 200 individual installable components each providing a different feature. Everyone of the systems that the CMS DCS consists of is created by installing a different set of these components. By automating this process, we are able to quickly and efficiently create new systems in production or recreate problematic ones, but also, to create development environments that are identical to the production ones. This latter one results in smoother development and integration processes, as the new/reworked components are developed and tested in production-like environments. Moreover, it allows the central DCS support team to easily reproduce systems that the users/developers report as being problematic, reducing the response time for bug fixing and improving the support quality.

43 PARTICLE ACCELERATORS↗
DOE OSTI2025

Accelerating Control Systems with GitOps: A Path to Automation and Reliability

GitOps is a foundational approach for modernizing infrastructure by leveraging Git as the single source of truth for declarative configurations. The poster explores how GitOps transforms traditional control system infrastructure, services and applications by enabling fully automated, auditable, and version-controlled infrastructure management. Cloud-native and containerized environments are shifting the ecosystem not only in the IT industry but also within the computational science field, as is the case of CERN and Diamond Light Source among other Accelerator/Science facilities which are slowly shifting towards modern software and infrastructure paradigms. The ACORN project, which aims to modernize Fermilab’s control system infrastructure and software is implementing proven best-practices and cutting-edge technology standards including GitOps, containerization, infrastructure as code and modern data pipelines for control system data acquisition and the inclusion of AI/ML in our accelerator complex.

Gonzalez, M. [Fermilab]↗
DOE OSTI2018

Optimization of Diffuser (Pre-Scatterer) Configurations for Slow Extraction Loss Reduction at Electrostatic Septa

Uncontrolled beam loss at the electrostatic septum is a performance limit for several existing or planned high power hadron accelerators delivering slow-extracted spills to fixed targets. A passive diffuser, or pre-scatterer, in a suitable configuration has been shown to reduce such beamloss significantly, with the actual gain factor depending on the parameters and details of the extraction process and hardware. In this paper, the optimization of diffuser configurations is investigated for a range of beam energies and extraction conditions, and the sensitivity to the available parameters explored via simulation results. The advantages and limitations of the diffuser are discussed and conclusions drawn concerning the specific case studies of the 8 GeV Fermilab debuncher ring and 400 GeV CERN SPS.

43 PARTICLE ACCELERATORS↗
DOE OSTI2019

Measurements of Decay and Snapback in Nb₃Sn Accelerator Magnets at Fermilab

In recent years, Fermilab has been executing an inten-sive R&D program on Nb₃Sn accelerator magnets. This program has included dipole and quadrupole models and demonstrators for various programs and projects, including the HL-LHC accelerator upgrade project. A systematic study of the field decay and snapback during the injection portion of a simulated accelerator cycle was executed at the Fermilab Magnet Test Facility. This paper summarizes the recent measurements of the MQXFS1 short quadrupole model and discusses the results of some previously measured Nb₃Sn magnets at CERN

43 PARTICLE ACCELERATORS↗