Azimuthal correlations of high transverse momentum jets at next-to-leading order in the parton branching method

AbstractThe azimuthal correlation, $$\Delta \phi _{12}$$ Δ ϕ 12 , of high transverse momentum jets in pp collisions at $$\sqrt{s}=13$$ s = 13  TeV is studied by applying PB-TMD distributions to NLO calculations via MCatNLO together with the PB-TMD parton shower. A very good description of the cross section as a function of $$\Delta \phi _{12}$$ Δ ϕ 12 is observed. In the back-to-back region of $${\Delta \phi _{12}}\rightarrow \pi$$ Δ ϕ 12 → π , a very good agreement is observed with the PB-TMD Set 2 distributions while significant deviations are obtained with the PB-TMD Set 1 distributions. Set 1 uses the evolution scale while Set 2 uses transverse momentum as an argument in $$\alpha _\mathrm {s}$$ α s , and the above observation therefore confirms the importance of an appropriate soft-gluon coupling in angular ordered parton evolution. The total uncertainties of the predictions are dominated by the scale uncertainties of the matrix element, while the uncertainties coming from the PB-TMDs and the corresponding PB-TMD shower are very small. The $$\Delta \phi _{12}$$ Δ ϕ 12 measurements are also compared with predictions using MCatNLO together Pythia8, illustrating the importance of details of the parton shower evolution.</jats:p

Search for dark matter particles in W+W− events with transverse momentum imbalance in proton-proton collisions at √s = 13 TeV

A preprint version of the article is available at arXiv:2310.12229v2 [hep-ex], https://arxiv.org/abs/2310.12229v2 . Comments: Replaced with the published version. Added the journal reference and the DOI. All the figures and tables can be found at https://cms-results.web.cern.ch/cms-results/public-results/publications/EXO-21-012 (CMS Public Pages).A search for dark matter particles is performed using events with a pair of W bosons and large missing transverse momentum. Candidate events are selected by requiring one or two leptons (ℓ = electrons or muons). The analysis is based on proton-proton collision data collected at a center-of-mass energy of 13 TeV by the CMS experiment at the LHC and corresponding to an integrated luminosity of 138 fb−1. No significant excess over the expected standard model background is observed in the ℓνqq and 2ℓ2ν final states of the W+W− boson pair. Limits are set on dark matter production in the context of a simplified dark Higgs model, with a dark Higgs boson mass above the W+W− mass threshold. The dark matter phase space is probed in the mass range 100–300 GeV, extending the scope of previous searches. Current exclusion limits are improved in the range of dark Higgs masses from 160 to 250 GeV, for a dark matter mass of 200 GeV.SCOAP3

Search for long-lived heavy neutral leptons with lepton flavour conserving or violating decays to a jet and a charged lepton

A preprint version of the article is available at arXiv:2312.07484v3 [hep-ex], https://arxiv.org/abs/2312.07484 . Comments: Replaced with the published version. Added the journal reference and the DOI. All the figures and tables can be found at https://cms-results.web.cern.ch/cms-results/public-results/publications/EXO-21-013 (CMS Public Pages)A search for long-lived heavy neutral leptons (HNLs) is presented, which considers the hadronic final state and coupling scenarios involving all three lepton generations in the 2-20 GeV HNL mass range for the first time. Events comprising two leptons (electrons or muons) and jets are analyzed in a data sample of proton-proton collisions, recorded with the CMS experiment at the CERN LHC at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 138 fb−1. A novel jet tagger, based on a deep neural network, has been developed to identify jets from an HNL decay using various features of the jet and its constituent particles. The network output can be used as a powerful discriminating tool to probe a broad range of HNL lifetimes and masses. Contributions from background processes are determined from data. No excess of events in data over the expected background is observed. Upper limits on the HNL production cross section are derived as functions of the HNL mass and the three coupling strengths VℓN to each lepton generation ℓ and presented as exclusion limits in the coupling-mass plane, as lower limits on the HNL lifetime, and on the HNL mass. In this search, the most stringent limit on the coupling strength is obtained for pure muon coupling scenarios; values of |VμN|2 > 5 (4) × 10−7 are excluded for Dirac (Majorana) HNLs with a mass of 10 GeV at a confidence level of 95% that correspond to proper decay lengths of 17 (10) mm.SCOAP3

Implementation of the Cluster Counting and Timing technique on FPGA for the reduction of transferred data and stored information

Ultra-low mass and high granularity Drift Chambers fulfill the requirements of tracking systems for modern High Energy Physics experiments at future high luminosity accelerators (FCC or CEPC). The application of the Cluster Counting/Timing (CCT) technique adds a valuable particle identification capabilities with resolutions outperforming the traditional dE/dx technique. By measuring the arrival times of each individual ionization electron to the sense wire and by using suitable statistical tools it is possible to perform a bias free estimate of the impact parameter and a precise particle identification in drift chamber operating in a Helium based gas mixtures. The CCT technique consisting in identifying pulses due to different ionization electrons and in associating them in clusters according to their relative time delays, therefore it is necessary to have read-out interfaces capable of processing such high speed signals. This requires a data acquisition chain, able to manage the low amplitude signals from the sense wires (a ~few mV) with a high bandwidth (~1 GHz). Requirements on the drift chamber performance impose analog-to-digital conversions by a fast ADC at sample rates of at least 2 GS/s with 14-bit resolution. These constraints, together with maximum drift times and many readout channels, impose some sizeable data reduction strategy, while preserving all relevant information. Measuring both the amplitude and the arrival time of each peak in the signal associated to each ionization electron is the minimum requirement on the data transfer for storage to prevent any data loss. An electronic board including a Fast ADC and an FPGA for real-time processing of drift chamber signals is presented. The implementation of different algorithms for peaks finding are compared

Measurement of the primary Lund jet plane density in proton-proton collisions at s\sqrt{s} = 13 TeV

A preprint version of the article is available at arXiv:2312.16343v1 [hep-ex], https://arxiv.org/abs/2312.16343v1 [it will be replaced with v2 in due course). Comments: Submitted to the Journal of High Energy Physics. All figures and tables can be found at https://cms-results.web.cern.ch/cms-results/public-results/publications/SMP-22-007 (CMS Public Pages). Report number: CMS-SMP-22-007, CERN-EP-2023-282.A measurement is presented of the primary Lund jet plane (LJP) density in inclusive jet production in proton-proton collisions. The analysis uses 138 fb−1 of data collected by the CMS experiment at √s = 13 TeV. The LJP, a representation of the phase space of emissions inside jets, is constructed using iterative jet declustering. The transverse momentum kT and the splitting angle ΔR of an emission relative to its emitter are measured at each step of the jet declustering process. The average density of emissions as function of ln(kT/GeV) and ln(R/ΔR) is measured for jets with distance parameters R = 0.4 or 0.8, transverse momentum pT> 700 GeV, and rapidity |y|< 1.7. The jet substructure is measured using the charged-particle tracks of the jet. The measured distributions, unfolded to the level of stable particles, are compared with theoretical predictions from simulations and with perturbative quantum chromodynamics calculations. Due to the ability of the LJP to factorize physical effects, these measurements can be used to improve different aspects of the physics modeling in event generators.SCOAP3

Search for flavor changing neutral current interactions of the top quark in final states with a photon and additional jets in proton-proton collisions at s\sqrt{s} = 13 TeV

A preprint of this article is available at: arXiv:2312.08229v2 [hep-ex], https://arxiv.org/abs/2312.08229 . Comments: Replaced with the published version. Added the journal reference and the DOI. All the figures and tables can be found at https://cms-results.web.cern.ch/cms-results/public-results/publications/TOP-21-013 (CMS Public Pages)A search for the production of a top quark in association with a photon and additional jets via flavor changing neutral current interactions is presented. The analysis uses proton-proton collision data recorded by the CMS detector at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 138 fb−1. The search is performed by looking for processes where a single top quark is produced in association with a photon, or a pair of top quarks where one of the top quarks decays into a photon and an up or charm quark. Events with an electron or a muon, a photon, one or more jets, and missing transverse momentum are selected. Multivariate analysis techniques are used to discriminate signal and standard model background processes. No significant deviation is observed over the predicted background. Observed (expected) upper limits are set on the branching fractions of top quark decays: B (t → uγ) < 0.95 × 10−5 (1.20 × 10−5) and B (t → cγ) < 1.51 × 10−5 (1.54 × 10−5) at 95% confidence level, assuming a single nonzero coupling at a time. The obtained limit for B(t → uγ) is similar to the current best limit, while the limit for B (t → cγ) is significantly tighter than previous results.SCOAP3