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On the Weyl anomaly for chiral fermions
No full textWe compute the parity-odd part of the Weyl anomaly for chiral fermions in a background gravitational field. We start from a manifestly real form of the Lagrangian (that is, not only real up to a total derivative), and we regularize it by means of Pauli-Villars fermions. All parity-odd terms in the anomaly cancel in the integrand, so that the result of the anomaly is necessarily parity-even
ATLAS Tile Calorimeter Performance in LHC Run~3
No full textThe Tile Calorimeter is a sampling hadronic calorimeter covering the central region of the ATLAS experiment, with steel as absorber and plastic scintillators as active medium. The scintillators are read-out by the wavelength shifting fibres coupled to the photomultiplier tubes (PMTs). The analogue signals from the PMTs are amplified, shaped, digitized by sampling the signal every 25~ns and stored on detector until a trigger decision is received. The Tile Calorimeter front-end electronics reads out the signals produced by about 10000 channels measuring energies ranging from about 30~MeV to about 2~TeV. Each stage of the signal production from scintillation light to the signal reconstruction is monitored and calibrated. During LHC runs, high-momentum isolated muons have been used to study and validate the electromagnetic scale, while hadronic response has been probed with isolated hadrons. The calorimeter time resolution has been studied with multi-jet events. A summary of the performance results with the LHC Run~3 data, including the calibration, stability, absolute energy scale, uniformity and time resolution, will be shown
Generalized Symmetries and Deformations of Symmetric Product Orbifolds
No full textWe construct generalized symmetries in two-dimensional symmetric product orbifold CFTs for a generic seed CFT . These symmetries are more general than the universal and maximally symmetric ones previously constructed. We show that, up to one fine-tuned example when the number of copies equals four, the only symmetries that can be preserved under twisted sector marginal deformations are invertible and maximally symmetric. The results are obtained in two ways. First, using the mathematical machinery of -equivariantization of fusion categories, and second, via the projector construction of topological defect lines. As an application, we classify all preserved symmetries in symmetric product orbifold CFTs with the seed CFT given by any -series minimal model. We comment on the implications of our results for holography
What JWST Reveals about the Hubble Tension (online talk)
No full textThe Hubble tension—the persistent discrepancy between local and early-Universe measurements of the Hubble constant—remains one of the most intriguing puzzles in cosmology. The James Webb Space Telescope (JWST) now offers a fresh perspective on this issue by allowing an independent look at the same type of stars, Cepheids, used in the Hubble Space Telescope (HST) measurements that help define our best local estimate of cosmic expansion. I’ll show how early JWST data, although still limited in size, serves as a powerful crosscheck of the HST-based distance ladder. When comparing results across multiple techniques and research groups, we find strong consistency with the HST measurements, lending confidence to their accuracy. These comparisons suggest that the observed tension is unlikely to stem from systematic errors in HST's Cepheid distances. Though JWST’s smaller sample size limits its precision for now, it already provides valuable validation of the HST approach. As more data accumulates, JWST will play an increasingly important role in testing and refining our understanding of the expanding Universe—and perhaps help us get to the bottom of the Hubble tension.
Bio: Adam Riess is a Bloomberg Distinguished Professor at Johns Hopkins University, a distinguished astronomer at the Space Telescope Science Institute and a member of the National Academy of Sciences.He was awarded the 2011 Nobel Prize in Physics for his leadership in the High-z Supernova Search Team’s discovery that the expansion rate of the universe is accelerating. Currently, he leads the SH0ES Team in efforts to improve the measurement of the Hubble Constant and the HIgher-z Team to find and measure the most distant type Ia supernovae known to probe the origin of cosmic acceleration.This Colloquium is part of the Invisibles25 Workshop (webpage)
Coffee and tea will be served at 16h
Organised by : Valerie Domcke, Miguel Escudero and Alexander Zhiboedov</p
Assembly and quality control tests of the 3D sensor modules for the innermost layer of the ATLAS ITk pixel detector
No full textThe High Luminosity upgrade of the Large Hadron Collider (HL-LHC) will push the ATLAS detector to handle an increased luminosity of and up to 200 proton-proton collisions per bunch crossing. To meet this challenge, the current ATLAS Inner Detector will be replaced with the new silicon-based Inner Tracker (ITk), consisting of a Pixel detector at a small radius and a surrounding Strip detector. The ITk Pixel detector uses hybrid pixel sensors bump-bonded to ITkPix readout chips CMOS). Planar sensors will be used for the outer layers, while radiation-hard 3D sensors are chosen for the innermost layer (L0), which faces fluences up to about . L0’s basic unit, the "triplet" module, consists of three 3D sensors individually hybridized to readout chips and mounted on a flexible PCB for biasing and communication. These modules are serially powered to minimize material budget. Three designs exist: linear triplets for the barrel and two ring geometries (R0, R0.5) for the end-cap sections. Seven European institutes handle triplet module assembly and quality control, with SLAC (US) integrating them into the inner system supports. This paper presents the current status of ITk triplet production, detailing assembly, testing procedures, bump connectivity checks, readout chip integrity, and sensor stability
Top quark, top precision: Tests of the Standard Model at the percent level with top-quark cross-section measurements with the ATLAS experiment
No full text
Using the full Run-2 dataset at √s = 13 TeV, the ATLAS Collaboration has measured the ˉ production cross-section with a precision of 1.3%, using opposite-sign electron-muon pairs and b-tagged jets. Several differential cross-section measurements are provided to test the QCD predictions at next-to-next-to-leading order precision as well as extract the top-quark pole mass. The Collaboration has also performed its first extraction of the top-quark Yukawa coupling from the ˉ invariant-mass spectrum near threshold using the lepton+jets final state, including ˉquasi bound-state effects.
Refreshments will be served at 10h30
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