arXiv subjects

Angela Giraldi

Publications and source records attributed to Angela Giraldi.

3 recordsLinked to original sources

arXiv2026

Design and performance of the Fast Beam Condition Monitor for luminosity and background measurement at the CMS Experiment in LHC Run 3

The Fast Beam Condition Monitor (BCM1F) has been used at the CMS Experiment since the first LHC circulating beams in 2008. Originally meant as a beam-induced background monitor for fast beam losses detection, it showed a potential also for luminosity measurements in 2012 running, and has been used for luminosity measurements since the beginning of Run 2 data taking in 2015 as a part of the Beam Radiation, Instrumentation and Luminosity (BRIL) system. Over the years, the system has undergone various upgrades to the sensors, the front-end and back-end electronics, providing improvements in the precision of the measurements, that remain valid in the higher pileup conditions of LHC Run 3 (2022-2026). Based on the experience of all BCM1F Run 2 upgrades, the detector was completely rebuilt prior to LHC Run 3 using AC-coupled silicon-pad diodes and active cooling. This latest detector version exhibits excellent linearity with instantaneous luminosity and achieves nanosecond-level timing precision, enabling improved systematic corrections for luminosity and background measurements. This paper presents a detailed overview of the detector system for LHC Run 3, including the selection and qualification of sensors as well as a summary of the readout system. It also outlines the processing and calibration strategy for luminosity data, discussing operational hurdles and comparing BCM1F measurements to other CMS luminosity measurements to assess the system's performance as a luminometer. Lastly, the implications for the design of a future luminosity detector to be used in the envisioned HL-LHC upgrade are discussed.

physics.ins-det↗

arXiv2022

$\mathrm{t\bar{t}H/tH}$ production at CMS

After the Higgs boson discovery, a main focus at the CERN LHC has been the measurement of its properties. Observing the Higgs boson associated production with a top quark-antiquark pair ($\mathrm{t\bar{t}H}$) is particularly interesting because it provides tree-level access to measuring the Higgs boson-top quark Yukawa coupling. However, the production of a single top quark in association with the Higgs boson ($\mathrm{tH}$) is also sensitive to the sign of this coupling. This coupling is essential for the stability of the Higgs potential at high energy scales and can also be a probe for physics beyond the standard model (SM). The latest measurements of the $\mathrm{t\bar{t}H}$ and $\mathrm{tH}$ associated production rates performed by the CMS Collaboration with proton-proton collision events at $\sqrt{s} =13$ TeV in the diphoton and multilepton channels are presented here. Events are categorized according to the lepton and jet multiplicities, and multivariate classifiers are used to distinguish signal from background processes. The results are consistent with the SM predictions and feature the first observation of $\mathrm{t\bar{t}H}$ production in a single Higgs boson decay channel along with the first tests of its CP structure.

hep-ex↗

arXiv2022

Precision luminosity measurement with proton-proton collisions at the CMS experiment in Run 2

A precision luminosity measurement is essential for LHC cross-section measurements to determine fundamental parameters of the standard model and constrain or discover beyond-the-standard-model phenomena. The luminosity of the CMS detector has been measured at the LHC Interaction Point 5 using proton-proton collisions at $\sqrt{s}=13$ TeV during the Run 2 data-taking period (2015-2018). The absolute luminosity scale is obtained using beam-separation scans and the Van der Meer (VdM) method, and several systematic uncertainty sources are investigated, from the knowledge of the scale of beam separation provided by LHC magnets to the nonfactorizability of the spatial components of proton bunch density distributions in the transverse direction. When the VdM calibration is applied to the entire data-taking period, the detector linearity and stability measurements contribute significantly to the total uncertainty in the integrated luminosity. In 2016-2018, the reported integrated luminosity was among the most precise measurements at bunched-beam hadron colliders.

hep-ex↗