Measurement of ttˉt\bar{t} production in association with a ZZ boson in pp collisions at S\sqrt{S} = 13.6TeV

We present a measurement of the inclusive cross section of $t\bar{t}$ production in association with a $Z$ boson in proton-proton collisions at a center-of-mass energy of 13.6TeV. The data samples used were collected by the CMS experiment in 2022 during run-3 of the Large Hadron Collider (LHC) at CERN, and they correspond to an integrated luminosity of 34.7fb$^{−1}$ . The measurement is performed using final states that contain 3 charged leptons, where 2 of them are an oppositely charged, same flavour pair with invariant mass compatible to that of the $Z$ boson. The production cross section is measured to be $\sigma (t\bar{t} Z ) = 0.10 \pm 0.01(\text{stat}) \pm 0.01(\text{syst})$pb

An experimental and numerical framework to assess the temperature distribution in complex He II-cooled magnet geometries

In the context of the High Luminosity upgrade of the Large Hadron Collider at CERN, a framework implementing experimental techniques and numerical analysis has been developed to systematically assess the temperature distribution in complex He II-cooled composite magnet geometries. The experiments are designed to measure the heat transfer coefficients in the magnet coil layers using coil samples in a stagnant superfluid helium bath. A numerical tool-kit has been developed to facilitate intensive parametric studies, in addition to estimation of helium content via a phenomenological model. The workflow of the tool-kit is built to handle complex geometries composed of different materials each with their temperature-dependent properties, at low computational cost. This framework has been validated with experimental data obtained from laboratory-scale experiments on impregnated coil samples, reported and discussed here. Three use cases for the developed numerical tool, with increasing levels of complexity, are presented and its results discussed. •In this article, a framework implementing experimental techniques and numerical analysis has been developed to systematically assess the temperature distribution in complex He II-cooled composite magnet geometries, which have been designed for the High-Luminosity upgrade of the LHC.•The experiments are designed keeping in mind the operational conditions of the magnets. The main aim is to measure the heat transfer coefficients in the layers by heating up actual coil samples in a pressurised stagnant superfluid helium bath. This is done by analysing the steady state behaviour of the samples. However, during the development of the experiment test stand which was done using prototype coil samples, a presence of helium content within the samples was observed from the transient behaviour. This was an unexpected since the impregnated Nb3Sn coils should be theoretically impervious to the helium. The measurements of production coil samples, which are only reported in this article, showed a reduction in the helium signature from the measurements, attributed to improved vacuum impregnation techniques.•In parallel, a numerical tool-kit has been developed to facilitate intensive parametric studies, in addition to estimation of helium content via a phenomenological model. Heat transfer simulations of the He II-cooled magnets are computationally intensive and a subject of considerable effort in the design and development of high field magnets. The workflow of the tool-kit is built to handle these complex geometries composed of different materials each with their temperature-dependent properties, while attacking the problem of computational cost. Compared to older techniques, the computational cost was reduced by a factor of almost 10. The tool-kit has been applied to three different use-cases with increasing levels of complexity. We aim to establish the robust nature of the tool-kit with this article, by providing a brief description of the approach and its applications

Student Sessions 2024

Introduction: Logan is a rising 4th-year Bachelors student at a Liberal Arts College called Pacific University in Forest Grove, Oregon, USA. He is double majoring in Physics and Mathematics and believes his career path is guiding him toward theoretical particle cosmology. Abstract: The Compact Muon Solenoid (CMS) detector records, at its peak, around 1 billion interactions per second (CMS Collaboration), which, over time, is way too much data to hang on to long-term. This is why CMS utilizes detector components called triggers, which sift through and decide whether or not to keep data. This project focuses on a more detail-oriented trigger, the High-Level Trigger (HLT) looking for an unobserved interaction: W-Boson decay into three charged pions. More specifically, we are analyzing the efficiency of triggers looking for this interaction to see if we can find a replacement for the DeepTau HLT trigger algorithm

Determination of the strong-coupling constant from the Z-boson transverse-momentum distribution

The coupling constant of the strong force is determined from the transverse-momentum distribution of Z bosons produced in 8 TeV proton-proton collisions. The Z-boson cross sections are measured in the full phase space of the decay leptons. The analysis is based on predictions evaluated at third order in perturbative QCD, supplemented by the resummation of logarithmically enhanced contributions in the low transverse-momentum region of the lepton pairs

Measurements of vector-boson scattering with the ATLAS experiment

[Proceeding draft for DIS 2024 talk] Measurements of diboson final states with two energetic jets allow to explore the electroweak production mechanism of the Standard Model using the data collected at the LHC. The ATLAS collaboration recentely released new measurements exploiting Wγ, opposite sign WW and WZ final states, with the the W and Z decaying leptonically. Observation of the electroweak production has been claimed in the first two channels. Inclusive and differential cross section measurements in phase spaces enhanced in the vector-boson scattering component have been performed. The growing interest in the constraint of the Effective Field Theory operators motivated to perform intepretation in these final states

CMS: Modernizing a CMS Production Code Base

Unified is a tool employed by the CMS offline and computing team to preform checks during the scheduling process of physics workflows on the computing grid available to the CMS group. The whole framework comprising of the WMCore and Unified operates as a finite state machine, starting from requesting a workflow to be scheduled on one of the available nodes. The process includes verifying the credentials of the requester, performing various validity checks on the workflow, scheduling and executing it, and assessing whether the produced results meet a minimum threshold. If the results meet the threshold, the workflow is announced; if not, it is resubmitted as an ACDC workflow. Despite its critical role, Unified was originally written without adhering to coding best practices. It featured several scripts/services comprising of a single, large function handling all tasks, resulting in redundant code and the absence of dedicated classes where necessary. This led to a complex and difficult-to-understand codebase. The task of this project was to refactor these scripts to improve their structure and maintainability

GEM performance results with 2024 data

The GE1/1 station is made of triple GEM detectors and it was installed in CMS between 2019 and 2020. This document presents a study on the performance in terms of stability of the electronics and efficiency. The study includes 2023 and 2024 data taking periods. Content: \begin{itemize} \item Fraction of the front-end chips that is configured and doesn't register errors \item Optimization study result for one chamber \item Efficiency map for a chamber \item Summary of the performance improvement between the beginning of 2024 and the HV settings adjustment. \end{itemize

Electroweak Physics at the LHC - Experimental Overview

Plenary talk at 42nd International Conference on High Energy Physic