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Measurement of WWZ and ZH cross sections at sqrt(s)=13 and 13.6 TeV in the four-lepton channel with the CMS detector
No full textA measurement is presented of the cross section in proton-proton collisions for the production of two W bosons and one Z boson. It is based on a data recorded by the CMS experiment at the CERN LHC at center-of-mass energies =13 and 13.6 TeV, and corresponding to an integrated luminosity of 200 fb. Events with four leptons (electrons or muons) in the final state are selected. Both non-resonant WWZ production and ZH production, with the Higgs boson decaying to two W bosons, are considered. For the first time, the two processes are measured simultaneously. Signal strengths relative to the standard model (SM) predictions of and are measured for =13 and 13.6 TeV respectively. The observed (expected) significance for the tri-boson signal is found to be 3.83 (2.49) standard deviations for =13.6 TeV, thus providing the first evidence at this center-of-mass energy. Taking all data together, the signal strength relative to the SM prediction is measured to be , with an observed (expected) significance of 4.53 (5.04) standard deviations
A New Stress-Relieving Layer in ATLAS ITk Strip Modules
No full textThe Inner Detector system of the ATLAS experiment is being entirely replaced with a new all-silicon detector known as the Inner Tracker (ITk) to prepare for high particle-rate conditions at the High Luminosity LHC. The innermost layers of the ITk will be composed of silicon pixels, while the outer layers will consist of silicon strips. The basic building block of the ITk Strip detector is the module, composed of front-end electronics glued to a silicon microstrip sensor. A critical problem was encountered during module pre-production wherein some silicon sensors cracked due to thermal stresses when mounted to local support structures and brought to cold operating temperatures. A potential solution has been trialed in which the modules are redesigned to include a new layer of soft glue between the front-end electronics and the silicon sensor to absorb thermal stresses. This redesign necessitated a new R&D phase of the project, during which new modules were assembled and proven to satisfy quality assurance and quality control criteria. These proceedings explore the technical challenges of incorporating the stress-relieving layer into the module assembly chain and evaluate the impact of the redesign on prototype module performance
Branching fraction measurement of the decay
No full textThe branching fraction of the decay , relative to the topologically similar decay , is measured using proton-proton collision data collected by the LHCb experiment at center-of-mass energies of 7, 8, and 13 TeV, corresponding to an integrated luminosity of . The ratio is found to be , where the first uncertainty is statistical and the second systematic. Using the world-average branching fraction for , the branching fraction for the decay is found to be , where the first uncertainty is statistical, the second systematic, and the third is due to the branching fraction of the normalization channel.The branching fraction of the decay , relative to the topologically similar decay , is measured using proton-proton collision data collected by the LHCb experiment at center-of-mass energies of 7, 8, and 13 TeV, corresponding to an integrated luminosity of . The ratio is found to be , where the first uncertainty is statistical and the second systematic. Using the world-average branching fraction for , the branching fraction for the decay is found to be , where the first uncertainty is statistical, the second systematic, and the third is due to the branching fraction of the normalization channel
Operational experience from the Spanish CMS Analysis Facility at CIEMAT
No full textThe anticipated surge in data volumes generated by the LHC in the coming years, especially during the High-Luminosity LHC phase, will reshape how physicists conduct their analysis. This necessitates a shift in programming paradigms and techniques for the final stages of analysis. As a result, there is a growing recognition within the community of the need for new computing infrastructures tailored to these evolving demands. To meet this need, the recently established Analysis Facility at the CIEMAT institute is already providing crucial support to the local analysis community. This contribution will describe the diverse resources and functionalities provided by the new facility, its expansion to complementary resources also available at CIEMAT, as well as the important feedback gained from the operational experience by the users
Search for the associated production of a Higgs boson with a charm quark in the diphoton decay channel in pp collisions at 13 TeV
No full textThis paper presents the first search for the associated production of a Higgs boson with a charm quark (), with the Higgs boson decaying to two photons. Associated production provides an opportunity to probe the coupling of the Higgs boson to charm quarks. The results are based on a data set of proton-proton collisions at a center-of-mass energy of 13 TeV collected with the CMS experiment at the LHC, corresponding to an integrated luminosity of 138 fb. Assuming the standard model (SM) rates for all other Higgs boson production processes, the observed (expected) upper limit at 95% confidence level on the signal strength is 243 (355) times the SM prediction. Under the same assumption, the observed (expected) allowed interval on the Higgs boson to charm quark coupling modifier, , is 38.1 ( 72.5) at 95% confidence level.This paper presents the first search for the associated production of a Higgs boson with a charm quark (cH), with the Higgs boson decaying to two photons. Associated cH production provides an opportunity to probe the coupling of the Higgs boson to charm quarks. The results are based on a data set of proton-proton collisions at a center-of-mass energy of 13 TeV collected with the CMS experiment at the LHC, corresponding to an integrated luminosity of 138 fb. Assuming the standard model (SM) rates for all other Higgs boson production processes, the observed (expected) upper limit at 95% confidence level on the cH signal strength is 243 (355) times the SM prediction. Under the same assumption, the observed (expected) allowed interval on the Higgs boson to charm quark coupling modifier, , is 38.1 ( 72.5) at 95% confidence level
Signal selection and model-independent extraction of the neutrino neutral-current single cross section with the T2K experiment
No full textThis article presents a study of single production in neutrino neutral-current interactions (NC1) using the ND280 detector of the T2K experiment. We report the largest sample of such events selected by any experiment, providing the first new data for this channel in over four decades and the first using a sub-GeV neutrino flux. The signal selection strategy and its performance are detailed together with validations of a robust cross section extraction methodology. The measured flux-averaged integrated cross-section is , 1.3~ above the NEUT v5.4.0 expectation
LumiDays 25
No full text- How are LHC experiments and LHC Operations using Emittance scans today
- Is there a preference for early or late scans
- How frequently should they be run
- List improvements that either have been implemented in the analysis since Run II , or are definitely needed (e.g.: BB corrections, all expts), or are being dreamt about (e.g. characterization of long-range BB effects in the scans with trains
Multiple (multi-)strange hadron production in proton-proton collisions at = 5.02 TeV with ALICE at the LHC
No full textThe increased production of strange hadrons in heavy-ion collisions compared to minimum-bias pp collisions has historically been interpreted as one of the earliest signatures of the formation of a deconfined quark-gluon plasma. One of the most significant findings from Run 1 and Run 2 of the LHC is the observation by the ALICE Collaboration of an enhanced production of (multi-)strange to non-strange hadron yields, gradually rising from low-multiplicity to high-multiplicity pp and p–Pb collisions, reaching values close to those measured in peripheral Pb–Pb collisions. Despite these observations, the origin of this phenomenon in small collision systems remains unclear. Furthermore, none of the current QCD-inspired Monte Carlo generators can quantitatively describe the observed behavior. This emphasizes the need for additional experimental data, new observables and theoretical advancements to uncover the microscopic mechanisms driving strangeness enhancement. A deeper understanding of the mechanisms behind strangeness production, and hadronization more in general, could be achieved by measuring the (multi-)strange particle multiplicity distribution (P()). A novel method involving event-by-event count-ing of strange particles offers a promising approach. In this thesis, the first ALICE results of the multiplicity distributions for K, , , , , , and in pp collisions at = 5.02 TeV are presented as a function of charged particle multiplicity. These results provide a unique perspective on the correlation between charged and strange particles’ production. Furthermore, the measurement of P() enables the determination of the average yields of multiplets for each type of strange particle, widening the scope of strangeness production studies beyond average values and enabling the investigation of extreme cases where up to six strange quarks coalesce into hadrons in a single event. Additionally, by comparing hadron combinations with varying and quark compositions but identical total strange () quark content, it becomes possible to isolate the contributions to the enhancement pattern that arise from mechanisms unrelated to strangeness. These findings are compared with state-of-the-art phenomenological models implemented in commonly used Monte Carlo event generators, drastically enhancing the sensitivity to the different processes implemented in each approach. This thesis also provides an overview of the data quality of the MUon IDentifier (MID) during pp and Pb–Pb collisions in Run 3 (2022–2024), with a focus on monitoring the asynchronous quality control