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The double differential cross sections of the Drell-Yan lepton pair ( , dielectron or dimuon) production are measured as functions of the invariant mass , transverse momentum , and . The observable, derived from angular measurements of the leptons and highly correlated with , is used to probe the low- region in a complementary way. Dilepton masses up to 1 are investigated. Additionally, a measurement is performed requiring at least one jet in the final state. To benefit from partial cancellation of the systematic uncertainty, the ratios of the differential cross sections for various ranges to those in the Z mass peak interval are presented. The collected data correspond to an integrated luminosity of 36.3 of proton-proton collisions recorded with the CMS detector at the LHC at a centre-of-mass energy of 13 . Measurements are compared with predictions based on perturbative quantum chromodynamics, including soft-gluon resummation.

The Czech Republic, Poland, and Slovakia share similar experiences in the past, and a swift post-communist integration into the originally West European communities of democratic countries, as their “return to Europe.” Michal Vít explores how these three countries have been influenced by the new all-European environment for their independent national development. He introduces a research framework for the analysis of national identity focusing on parliamentary political parties represented at both the national and European levels. How did these parties cope with possible misfits of their understanding of national identity? How did these tensions interplay with their new transnational European political environment? Vít’s study finds that, after the accession of the Czech Republic, Poland, and Slovakia to the EU, there started a gradual decrease of identification of political parties with the European space. The extent of this estrangement was determined by these parties’ belonging or non-belonging to European political party families. The book provides a better understanding of current political developments in East-Central Europe and their consequences for these countries’ national and European politics.

Abstract A data sample of events from proton-proton collisions with at least two jets, and two isolated same-sign or three or more charged leptons, is studied in a search for signatures of new physics phenomena. The data correspond to an integrated luminosity of $$137{\\,{\\text {fb}}^{-1}} $$ 137fb-1 at a center-of-mass energy of $$13\\,{\\text {TeV}} $$ 13TeV , collected in 2016–2018 by the CMS experiment at the LHC. The search is performed using a total of 168 signal regions defined using several kinematic variables. The properties of the events are found to be consistent with the expectations from standard model processes. Exclusion limits at 95% confidence level are set on cross sections for the pair production of gluinos or squarks for various decay scenarios in the context of supersymmetric models conserving or violating R parity. The observed lower mass limits are as large as $$2.1\\,{\\text {TeV}} $$ 2.1TeV for gluinos and $$0.9\\,{\\text {TeV}} $$ 0.9TeV for top and bottom squarks. To facilitate reinterpretations, model-independent limits are provided in a set of simplified signal regions.

Abstract The standard model (SM) production of four top quarks ($$\\text {t} {}{\\overline{\\text {t}}} \\text {t} {}{\\overline{\\text {t}}} $$ tt¯tt¯ ) in proton–proton collisions is studied by the CMS Collaboration. The data sample, collected during the 2016–2018 data taking of the LHC, corresponds to an integrated luminosity of 137$$\\,\\text {fb}^{-1}$$ fb-1 at a center-of-mass energy of 13$$\\,\\text {TeV}$$ TeV . The events are required to contain two same-sign charged leptons (electrons or muons) or at least three leptons, and jets. The observed and expected significances for the $$\\text {t} {}{\\overline{\\text {t}}} \\text {t} {}{\\overline{\\text {t}}} $$ tt¯tt¯ signal are respectively 2.6 and 2.7 standard deviations, and the $$\\text {t} {}{\\overline{\\text {t}}} \\text {t} {}{\\overline{\\text {t}}} $$ tt¯tt¯ cross section is measured to be $$12.6^{+5.8}_{-5.2}\\,\\text {fb} $$ 12.6-5.2+5.8fb . The results are used to constrain the Yukawa coupling of the top quark to the Higgs boson, $$y_{\\text {t}}$$ yt , yielding a limit of $$|y_{\\text {t}}/y_{\\text {t}}^{\\mathrm {SM}} | < 1.7$$ |yt/ytSM|<1.7 at $$95\\%$$ 95% confidence level, where $$y_{\\text {t}}^{\\mathrm {SM}}$$ ytSM is the SM value of $$y_{\\text {t}}$$ yt . They are also used to constrain the oblique parameter of the Higgs boson in an effective field theory framework, $$\\hat{H}<0.12$$ H^<0.12 . Limits are set on the production of a heavy scalar or pseudoscalar boson in Type-II two-Higgs-doublet and simplified dark matter models, with exclusion limits reaching 350–470$$\\,\\text {GeV}$$ GeV and 350–550$$\\,\\text {GeV}$$ GeV for scalar and pseudoscalar bosons, respectively. Upper bounds are also set on couplings of the top quark to new light particles.

Abstract Two related searches for phenomena beyond the standard model (BSM) are performed using events with hadronic jets and significant transverse momentum imbalance. The results are based on a sample of proton–proton collisions at a center-of-mass energy of $$13\\,\\text {Te}\\text {V} $$ 13Te , collected by the CMS experiment at the LHC in 2016–2018 and corresponding to an integrated luminosity of 137$$\\,\\text {fb}^{-1}$$ fb-1 . The first search is inclusive, based on signal regions defined by the hadronic energy in the event, the jet multiplicity, the number of jets identified as originating from bottom quarks, and the value of the kinematic variable $$M_{\\mathrm {T2}}$$ MT2 for events with at least two jets. For events with exactly one jet, the transverse momentum of the jet is used instead. The second search looks in addition for disappearing tracks produced by BSM long-lived charged particles that decay within the volume of the tracking detector. No excess event yield is observed above the predicted standard model background. This is used to constrain a range of BSM models that predict the following: the pair production of gluinos and squarks in the context of supersymmetry models conserving R-parity, with or without intermediate long-lived charginos produced in the decay chain; the resonant production of a colored scalar state decaying to a massive Dirac fermion and a quark; or the pair production of scalar and vector leptoquarks each decaying to a neutrino and a top, bottom, or light-flavor quark. In most of the cases, the results obtained are the most stringent constraints to date.

Abstract The double differential cross sections of the Drell–Yan lepton pair ( $$\\ell ^+\\ell ^-$$ ℓ + ℓ - , dielectron or dimuon) production are measured as functions of the invariant mass $$m_{\\ell \\ell }$$ m ℓ ℓ , transverse momentum $$p_{\\textrm{T}} (\\ell \\ell )$$ p T ( ℓ ℓ ) , and $$\\varphi ^{*}_{\\eta }$$ φ η ∗ . The $$\\varphi ^{*}_{\\eta }$$ φ η ∗ observable, derived from angular measurements of the leptons and highly correlated with $$p_{\\textrm{T}} (\\ell \\ell )$$ p T ( ℓ ℓ ) , is used to probe the low- $$p_{\\textrm{T}} (\\ell \\ell )$$ p T ( ℓ ℓ ) region in a complementary way. Dilepton masses up to 1 $$\\,\\text {Te\\hspace{-.08em}V}$$ Te V are investigated. Additionally, a measurement is performed requiring at least one jet in the final state. To benefit from partial cancellation of the systematic uncertainty, the ratios of the differential cross sections for various $$m_{\\ell \\ell }$$ m ℓ ℓ ranges to those in the Z mass peak interval are presented. The collected data correspond to an integrated luminosity of 36.3 $$\\,\\text {fb}^{-1}$$ fb - 1 of proton–proton collisions recorded with the CMS detector at the LHC at a centre-of-mass energy of 13 $$\\,\\text {Te\\hspace{-.08em}V}$$ Te V . Measurements are compared with predictions based on perturbative quantum chromodynamics, including soft-gluon resummation.

Abstract Results are presented from a search for CP violation in top quark pair production, using proton-proton collisions at a center-of-mass energy of 13 TeV. The data used for this analysis consist of final states with two charged leptons collected by the CMS experiment, and correspond to an integrated luminosity of 35.9 fb −1. The search uses two observables, O $$ \\mathcal{O} $$ 1 and O $$ \\mathcal{O} $$ 3, which are Lorentz scalars. The observable O $$ \\mathcal{O} $$ 1 is constructed from the four-momenta of the charged leptons and the reconstructed top quarks, while O $$ \\mathcal{O} $$ 3 consists of the four-momenta of the charged leptons and the b quarks originating from the top quarks. Asymmetries in these observables are sensitive to CP violation, and their measurement is used to determine the chromoelectric dipole moment of the top quark. The results are consistent with the expectation from the standard model.

Abstract A search for physics beyond the standard model (SM) in final states with an electron or muon and missing transverse momentum is presented. The analysis uses data from proton-proton collisions at a centre-of-mass energy of 13 TeV, collected with the CMS detector at the LHC in 2016–2018 and corresponding to an integrated luminosity of 138 fb −1. No significant deviation from the SM prediction is observed. Model-independent limits are set on the production cross section of W’ bosons decaying into lepton-plus-neutrino final states. Within the framework of the sequential standard model, with the combined results from the electron and muon decay channels a W’ boson with mass less than 5.7 TeV is excluded at 95% confidence level. Results on a SM precision test, the determination of the oblique electroweak W parameter, are presented using LHC data for the first time. These results together with those from the direct W’ resonance search are used to extend existing constraints on composite Higgs scenarios. This is the first experimental exclusion on compositeness parameters using results from LHC data other than Higgs boson measurements.

Abstract A search for supersymmetry in events with two or three low-momentum leptons and missing transverse momentum is performed. The search uses proton-proton collisions at s $$ \\sqrt{s} $$ = 13 TeV collected in the three-year period 2016–2018 by the CMS experiment at the LHC and corresponding to an integrated luminosity of up to 137 fb −1. The data are found to be in agreement with expectations from standard model processes. The results are interpreted in terms of electroweakino and top squark pair production with a small mass difference between the produced supersymmetric particles and the lightest neutralino. For the electroweakino interpretation, two simplified models are used, a wino-bino model and a higgsino model. Exclusion limits at 95% confidence level are set on χ ~ 2 0 / χ ~ 1 ± $$ {\\overset{\\sim }{\\upchi}}_2^0/{\\overset{\\sim }{\\upchi}}_1^{\\pm } $$ masses up to 275 GeV for a mass difference of 10 GeV in the wino-bino case, and up to 205(150) GeV for a mass difference of 7.5 (3) GeV in the higgsino case. The results for the higgsino are further interpreted using a phenomenological minimal supersymmetric standard model, excluding the higgsino mass parameter μ up to 180 GeV with the bino mass parameter M 1 at 800 GeV. In the top squark interpretation, exclusion limits are set at top squark masses up to 540 GeV for four-body top squark decays and up to 480 GeV for chargino-mediated decays with a mass difference of 30 GeV.

Abstract The top quark pair production cross section is measured in proton-proton collisions at a center-of-mass energy of 5.02 TeV. The data were collected in a special LHC low-energy and low-intensity run in 2017, and correspond to an integrated luminosity of 302 pb −1. The measurement is performed using events with one electron and one muon of opposite charge, and at least two jets. The measured cross section is 60.7 ± 5.0 (stat) ± 2.8 (syst) ± 1.1 (lumi) pb. A combination with the result in the single lepton + jets channel, based on data collected in 2015 at the same center-of-mass energy and corresponding to an integrated luminosity of 27.4 pb −1, is then performed. The resulting measured value is 63.0 ± 4.1 (stat) ± 3.0 (syst+lumi) pb, in agreement with the standard model prediction of 66.8 − 3.1 + 2.9 $$ {66.8}_{-3.1}^{+2.9} $$ pb.