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ATLAS Coordinate System - ATLAS Cheat Sheet
No full textPhysics Cheat Sheets are an outreach resource for the general public or students to better understand some of the fundamental concepts of particle physics. They could be used online or as posters. This sheet explains the ATLAS coordinate system
Dark sector searches at ATLAS and CMS
No full textIn the quest for expanding our understanding of Nature, one of the main open issues is the existence of dark matter i.e., the observation that most of the gravitational mass acting in the universe appears insensitive to any of the other known interactions. Collider experiments provides a powerful complement to direct and indirect searches for dark matter, both thorough searches based on simplified models aimed at exploring wide ranges of phase space, as well as more targeted searches for signatures that would elude the first strategy. We present recent results in this field from the ATLAS and CMS experiment at the CERN LHC collider
Measurement of Threshold Voltages in PTP Structures and Estimation of P-stop Densities Across an ATLAS18 Silicon Strip Sensor Wafer Using TCAD Simulations
No full textA total of 24,010 AC-coupled silicon strip sensors, consisting of n-type strips in p-type silicon and referred to as ATLAS18, are currently in production for installation in the upgraded ATLAS Inner Tracker (ITk). In n-in-p strip sensors, a dense p-type region (e.g., p-stop implant) is essential for electrically isolating the n-type strips from a conductive inversion layer between the strips, caused by positive interface charges. The punch-through protection (PTP) structure is implemented at one end of each strip to protect the AC-coupling capacitor in the event of large currents flowing into the strips. During quality assurance (QA) testing, we occasionally observed a deviation in the threshold voltage () of the PTP structure in the test chips located at a corner of the wafer perimeter, with a shift of four standard deviations or more below the mean. To evaluate the variation of across a wafer, we selected two main sensors, each processed in a different furnace, where measurements in the QA test chips were still near the mean value. One sensor exhibited a flat distribution of measurements, while the other showed a non-uniform, parabolic distribution, with a shift of four standard deviations toward the wafer edge. TCAD simulations were used to analyze as a function of p-stop density, confirming that the correlates well with the p-stop density. By setting the nominal p-stop density ( cm) to correspond to the mean value, the p-stop density at the wafer edge, which is four standard deviations away from the mean, is estimated to be approximately half ( cm). A p-stop density of cm should still be sufficient to ensure isolation, even after irradiation, and in the presence of interface charges as high as cm
Mechanical Design and Integration of the CMS Phase-2 Tracker
No full textThe mechanical design of the CMS Phase-2 Tracker addresses the stringent requirements imposed by the High Luminosity LHC environment, including stability under high radiation and thermal loads, a minimal material budget, and precise alignment across large detector volumes. This article describes the engineering challenges and the mechanical solutions implemented in both the Inner Tracker and the Outer Tracker. Key topics include the design of support structures, thermal management systems, carbon-fibre composite components, and the modularity that enables efficient assembly and maintenance. The integration strategy, from substructures to the fully assembled Tracker, is presented together with results from mechanical qualification tests, thermal cycling, and alignment validation, demonstrating the readiness of the Phase-2 Tracker for High Luminosity LHC operation
Chiral Composite Linear Dilaton as String Dual to Two-Dimensional Yang-Mills
No full textTwo-dimensional Yang-Mills theory (2d YM) is arguably the simplest confining gauge theory and its large expansion has a structure of the genus expansion in string theory. Nevertheless various aspects of its worldsheet description have not been fully understood. In this paper, we elaborate on a bosonic string dual to large chiral 2d YM at finite 't Hooft coupling, proposed in our earlier work. The worldsheet theory consists of - system deformed by linear dilaton action built from a composite of . It can be seen as a noncritical version of nonrelativistic string theory introduced by Gomis and Ooguri. We provide a detailed analysis of the worldsheet operator product expansion and the computation of three- and four-point scattering amplitudes