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Finance Committee - Three-Hundred-and-Ninety-Ninth Meeting
No full textFinance Committee - Three-Hundred-and-Ninety-Ninth Meetin
Parameter Estimation with Neural Simulation-Based Inference in ATLAS
No full textNeural Simulation-Based Inference (NSBI) is a powerful class of machine learning (ML)-based methods for statistical inference that naturally handle high dimensional parameter estimation without the need to bin data into low-dimensional summary histograms. Such methods are promising for a range of measurements at the Large Hadron Collider, where no single observable may be optimal to scan over the entire theoretical phase space under consideration, or where binning data into histograms could result in a loss of sensitivity. This work develops an NSBI framework that, for the first time, allows NSBI to be applied to a full-scale LHC analysis, by successfully incorporating a large number of systematic uncertainties, quantifying the uncertainty coming from finite training statistics, developing a method to construct confidence intervals, and demonstrating a series of intermediate diagnostic checks that can be performed to validate the robustness of the method. As an example, the power and feasibility of the method are demonstrated for an off-shell Higgs boson couplings measurement in the four lepton decay channel, using ATLAS experiment simulated samples. The proposed method is a generalisation of the standard statistical framework at the LHC, and can benefit a large number of physics analyses. This work serves as a blueprint for measurements at the LHC using NSBI
ATLAS results on ultra-peripheral collisions
No full textThe future electron-hadron collider (EIC) at Brookhaven National Laboratory and the High-Luminosity Large Hadron Collider (HL-LHC) at CERN represent the next frontiers for high precision quantum chromodynamics (QCD) measurements in nuclear physics. The staggered timelines, together with the synergy between the physics programs of the two accelerators, offer unique opportunities to advance the understanding of QCD in both the hot and cold temperature regimes. Thanks to its outstanding detection capabilities, the ATLAS experiment at the LHC can reconstruct proton-proton (p+p), proton-nucleus (p+A), and nucleus-nucleus (A+A) collisions with high precision. In this talk, I will review recent heavy-ion results from ATLAS that are directly related to the physics landscape of the LHC. I will present ultra-peripheral A+A collisions, demonstrating their direct connection to the EIC program
Search for charged lepton flavor violating Z and Z' boson decays in proton-proton collisions at 13 TeV
No full textA search for flavor violating decays of the Z boson to charged leptons is performed using data from proton-proton collisions at 13 TeV collected with the CMS detector at the LHC, corresponding to an integrated luminosity of 138 fb. Each of the decays , , and is considered. The data are consistent with the backgrounds expected from standard model processes. For the channel the observed (expected) 95% confidence level upper limit on the branching fraction is 1.9 (2.0)10, which is the most stringent direct limit to date on this process; the corresponding limits for the and channels are 13.8 (11.4)10 and 12.0 (5.3)10, respectively. Additionally, the final state is used to search for lepton flavor violating decays of Z' resonances in the mass range from 110 to 500 GeV. No significant excess is observed above the predicted background levels.A search for flavor violating decays of the Z boson to charged leptons is performed using data from proton-proton collisions at s=13 TeV collected with the CMS detector at the LHC, corresponding to an integrated luminosity of 138 fb-1. Each of the decays Z→eμ, Z→eτ, and Z→μτ is considered. The data are consistent with the backgrounds expected from standard model processes. For the Z→eμ channel the observed (expected) 95% confidence level upper limit on the branching fraction is 1.9(2.0)×10-7, which is the most stringent direct limit to date on this process; the corresponding limits for the Z→eτ and Z→μτ channels are 13.8(11.4)×10-6 and 12.0(5.3)×10-6, respectively. Additionally, the eμ final state is used to search for lepton flavor violating decays of Z′ resonances in the mass range from 110 to 500 GeV. No significant excess is observed above the predicted background levels.A search for flavor violating decays of the Z boson to charged leptons is performed using data from proton-proton collisions at = 13 TeV collected with the CMS detector at the LHC, corresponding to an integrated luminosity of 138 fb. Each of the decays Z e, Z e, and Z is considered. The data are consistent with the backgrounds expected from standard model processes. For the Z e channel the observed (expected) 95% confidence level upper limit on the branching fraction is 1.9 (2.0) 10, which is the most stringent direct limit to date on this process; the corresponding limits for the Z e and Z channels are 13.8 (11.4) 10 and 12.0 (5.3) 10, respectively. Additionally, the e final state is used to search for lepton flavor violating decays of Z' resonances in the mass range from 110 to 500 GeV. No significant excess is observed above the predicted background levels
Visit by Her Excellency Ms Sylvie Bollini, Permanent Observer of the Council of Europe to the United Nations Office and other international organisations in Geneva
No full textVisit by Her Excellency Ms Sylvie Bollini, Permanent Observer of the Council of Europe to the United Nations Office and other international organisations in Genev
Margin on the FMCM Threshold for the MBS in TT66
No full textOn 1st April 2025, voltage ripples at the output of the MBS dipoles’ power converter in TT66 inhibited beam extraction to HiRadMat. Despite several mitigation measures, including component replacements, the issue persisted. As a temporary solution, the FMCM threshold was relaxed from approximately 300 ppm to approximately 500 ppm. This note evaluates whether the increased threshold can be safely maintained by assessing its impact on machine protection, performing simulations, and comparing the results to previous studies to propose an acceptable limit