Search for new particles in events with energetic jets and large missing transverse momentum in proton-proton collisions at root s=13 TeV

A search is presented for new particles produced at the LHC in proton-proton collisions at root s = 13 TeV, using events with energetic jets and large missing transverse momentum. The analysis is based on a data sample corresponding to an integrated luminosity of 101 fb(-1), collected in 2017-2018 with the CMS detector. Machine learning techniques are used to define separate categories for events with narrow jets from initial-state radiation and events with large-radius jets consistent with a hadronic decay of a W or Z boson. A statistical combination is made with an earlier search based on a data sample of 36 fb(-1), collected in 2016. No significant excess of events is observed with respect to the standard model background expectation determined from control samples in data. The results are interpreted in terms of limits on the branching fraction of an invisible decay of the Higgs boson, as well as constraints on simplified models of dark matter, on first-generation scalar leptoquarks decaying to quarks and neutrinos, and on models with large extra dimensions. Several of the new limits, specifically for spin-1 dark matter mediators, pseudoscalar mediators, colored mediators, and leptoquarks, are the most restrictive to date.Peer reviewe

Probing effective field theory operators in the associated production of top quarks with a Z boson in multilepton final states at root s=13 TeV

Peer reviewe

Flavor tagging algorithms for CP violation measurements in CMS

This thesis presents the development of four flavor tagging algorithms to be used in CP violation measurements in CMS. Flavor tagging is an essential tool for CP violation measurement, which often rely on the knowledge of both the initial and final flavor of a meson. Three of the algorithm presented use the production of quarks as pairs and analyze the -hadron unrelated to the signal, while the last one examines the hadronization of the signal meson to infer its flavor. The last algorithms is specifically novel in its kind, as it does not make use of particle identification for the inference or the selection of the input features. All taggers examined are based on Deep Neural Networks and are developed and calibrated using reconstructed $_{s}^{0}$ → / (1020) and $^{+}$ → / $^{+}$ decays. The performance of the taggers is evaluated in a dataset corresponding to 96.48 fb$^{-1}$ collected in proton-proton collisions at $\sqrt{s}$ = 13 TeV during the years 2017 and 2018 by the CMS experiment. After combination of the various algorithms, the total tagging power $_{tag}$ is estimated to be $_{tag}$ = 5.59 ± 0.02%. With this combination, a ∼ 30% subset of the data sample is used in a time-dependent angular analysis for a measurement of the CP violating phase $_{s}$, obtaining a result of $_{s}$ = −21 ± 42 (stat.) mrad. A suite of tagging related systematic uncertainties is evaluated on the measurements, showing them to be negligible compared to the statistical uncertainty and to the intrinsic model bias of the fitting procedure.

Misura della produzione di coppie b-anti b in collisioni protone-protone a 13 TeV nell'esperimento CMS / Measurement of bb_bar production in s = 13 TeV pp collisions with the CMS experiment

The measurent of the bb_bar production cross-section is a very important test of our understanding of QCD at high energies. In this thesis we will present a novel method for this measurement using comparison between pileup and signal vertices, which avoids sistematic errors due to luminosity or branching ratios of intermediate processes and might provide a better accuracy compared to previous measures

Misura della produzione di coppie b-anti b in collisioni protone-protone a 13 TeV nell'esperimento CMS / Measurement of bb_bar production in s = 13 TeV pp collisions with the CMS experiment

The measurent of the bb_bar production cross-section is a very important test of our understanding of QCD at high energies. In this thesis we will present a novel method for this measurement using comparison between pileup and signal vertices, which avoids sistematic errors due to luminosity or branching ratios of intermediate processes and might provide a better accuracy compared to previous measures.ope

Relation between drug therapy-based comorbidity indices, Charlson's comorbidity index, polypharmacy and mortality in three samples of older adults.

Background: Comorbidity indexes were designed in order to measure how the disease burden of a patient is related to different clinical outcomes such as mortality, especially in older and intensively treated people. Charlson's Comorbidity Index (CCI) is the most widely used rating system, based on diagnoses, but when this information is not available therapy-based comorbidity indices (TBCI) are an alternative: among them, Drug Derived Complexity Index (DDCI), Medicines Comorbidity Index (MCI), and Chronic Disease Score (CDS) are available. Aims: This study assessed the predictive power for 1-year mortality of these comorbidity indices and polypharmacy. Methods: Survival analysis and Receiver Operating Characteristic (ROC) analysis were conducted on three Italian cohorts: 2,389 nursing home residents (Korian), 4,765 and 633 older adults admitted acutely to geriatric or internal medicine wards (REPOSI and ELICADHE). Results: Cox's regression indicated that the highest levels of the CCI are associated with an increment of 1-year mortality risk as compared to null score for all the three samples. DDCI and excessive polypharmacy gave similar results but MCI and CDS were not always statistically significant. The predictive power with the ROC curve of each comorbidity index was poor and similar in all settings. Conclusion: On the whole, comorbidity indices did not perform well in our three settings, although the highest level of each index was associated with higher mortality

Search for the rare decays B→πl+l− and B0→ηl+l−

We present the results of a search for the rare flavor-changing neutral-current decays B→πl+l− (π=π±, π0 and l=e, μ) and B0→ηl+l− using a sample of e+e−→Υ(4S)→BB⎯⎯⎯ decays corresponding to 428 fb−1 of integrated luminosity collected by the BABAR detector. No significant signal is observed, and we set an upper limit on the isospin and lepton-flavor averaged branching fraction of B(B→πl+l−)<5.9×10−8 and a lepton-flavor averaged upper limit of B(B0→ηl+l−)<6.4×10−8, both at the 90% confidence level. We also report 90% confidence level branching fraction upper limits for the individual modes B+→π+e+e−, B0→π0e+e−, B+→π+μ+μ−, B0→π0μ+μ−, B0→ηe+e−, and B0→ημ+μ−

Strategies and performance of the CMS silicon tracker alignment during LHC Run 2

The strategies for and the performance of the CMS silicon tracking system alignment during the 2015–2018 data-taking period of the LHC are described. The alignment procedures during and after data taking are explained. Alignment scenarios are also derived for use in the simulation of the detector response. Systematic effects, related to intrinsic symmetries of the alignment task or to external constraints, are discussed and illustrated for different scenarios

Measurement of the double-differential inclusive jet cross section in proton-proton collisions at s\sqrt{s} = 5.02 TeV

International audienceThe inclusive jet cross section is measured as a function of jet transverse momentum $p_\mathrm{T}$ and rapidity $y$. The measurement is performed using proton-proton collision data at $\sqrt{s}$ = 5.02 TeV, recorded by the CMS experiment at the LHC, corresponding to an integrated luminosity of 27.4 pb$^{-1}$. The jets are reconstructed with the anti-$k_\mathrm{T}$ algorithm using a distance parameter of $R$ = 0.4, within the rapidity interval $\lvert y\rvert$$\lt$ 2, and across the kinematic range 0.06 $\lt$$p_\mathrm{T}$$\lt$ 1 TeV. The jet cross section is unfolded from detector to particle level using the determined jet response and resolution. The results are compared to predictions of perturbative quantum chromodynamics, calculated at both next-to-leading order and next-to-next-to-leading order. The predictions are corrected for nonperturbative effects, and presented for a variety of parton distribution functions and choices of the renormalization/factorization scales and the strong coupling $\alpha_\mathrm{S}$