The yields and average transverse momenta of pions, kaons, and antiprotons produced at the Fermilab p¯p collider at s=300, 540, 1000, and 1800 GeV are presented and compared with data from the energies reached at the CERN collider. We also present data on the dependence of average transverse momentum 〈pt〉 and particle ratios as a function of charged particle density dNcdη; data for particle densities as high as six times the average value, corresponding to a Bjorken energy density 6 GeV/fm3, are reported. These data are relevant to the search for quark-gluon phase of QCD.

The observation of the production of four top quarks in proton-proton collisions is reported, based on a data sample collected by the CMS experiment at a center-of-mass energy of 13 TeV in 2016-2018 at the CERN LHC and corresponding to an integrated luminosity of 138 fb$^{-1}$. Events with two same-sign, three, or four charged leptons (electrons and muons) and additional jets are analyzed. Compared to previous results in these channels, updated identification techniques for charged leptons and jets originating from the hadronization of b quarks, as well as a revised multivariate analysis strategy to distinguish the signal process from the main backgrounds, lead to an improved expected signal significance of 4.9 standard deviations above the background-only hypothesis. Four top quark production is observed with a significance of 5.6 standard deviations, and its cross section is measured to be 17.7 $^{+3.7}_{-3.5}$ (stat) $^{+2.3}_{-1.9}$ (syst) fb, in agreement with the available standard model predictions.

A measurement of the differential cross sections for a W boson produced in association with jets in the muon decay channel is presented. The measurement is based on 13 TeV proton-proton collision data corresponding to an integrated luminosity of 2.2 inverse femtobarns, recorded by the CMS detector at the LHC. The cross sections are reported as functions of jet multiplicity, jet transverse momentum pT, jet rapidity, the scalar pT sum of the jets, and angular correlations between the muon and the jet for different jet multiplicities. The measured cross sections are in agreement with predictions that include multileg leading-order (LO) and next-to-LO matrix element calculations interfaced with parton showers, as well as a next-to-next-to-LO calculation for the W boson and one jet production.

Four-lepton production in proton-proton collisions, $\mathrm{pp}\to (\mathrm{Z}/ \gamma^*)(\mathrm{Z}/\gamma^*) \to 4\ell$, where $\ell = \mathrm{e}$ or $\mu$, is studied at a center-of-mass energy of 13 TeV with the CMS detector at the LHC. The data sample corresponds to an integrated luminosity of 35.9 fb$^{-1}$. The ZZ production cross section, $\sigma(\mathrm{pp} \to \mathrm{Z}\mathrm{Z}) = 17.2 \pm 0.5\text{ (stat) }\pm 0.7\text{ (syst) }\pm 0.4(\mathrm{theo}) \pm 0.4\text{ (lumi)}$ pb, measured using events with two opposite-sign, same-flavor lepton pairs produced in the mass region $60 < m_{\ell^+\ell^-} < $120 GeV, is consistent with standard model predictions. Differential cross sections are measured and are well described by the theoretical predictions. The Z boson branching fraction to four leptons is measured to be $\mathcal{B}(\mathrm{Z}\to 4\ell) = 4.8 \pm 0.2\text{ (stat) }\pm 0.2\text{ (syst) } \pm 0.1\text{ (theo) }\pm 0.1\text{ (lumi) }\times 10^{-6}$ for events with a four-lepton invariant mass in the range 80 $ < m_{4\ell} < $ 100 GeV and a dilepton mass $m_{\ell\ell} > $4 GeV for all opposite-sign, same-flavor lepton pairs. The results agree with standard model predictions. The invariant mass distribution of the four-lepton system is used to set limits on anomalous ZZZ and ZZ$\gamma$ couplings at 95% confidence level: $-0.0012 < f_4^\mathrm{Z} < 0.0010$, $-0.0010 < f_5^\mathrm{Z} < 0.0013$, $-0.0012 < f_4^{\gamma} < 0.0013$, $-0.0012 < f_5^{\gamma} < 0.0013$.

Differential production cross sections of J/$\psi$ and $\psi$(2S) charmonium and $\Upsilon$(nS) (n = 1, 2, 3) bottomonium states are measured in proton-proton collisions at $\sqrt{s} =$ 13 TeV, with data collected by the CMS detector at the LHC, corresponding to an integrated luminosity of 2.3 fb$^{-1}$ for the J/$\psi$ and 2.7 fb$^{-1}$ for the other mesons. The five quarkonium states are reconstructed in the dimuon decay channel, for dimuon rapidity $|y| <$ 1.2. The double-differential cross sections for each state are measured as a function of $y$ and transverse momentum, and compared to theoretical expectations. In addition, ratios are presented of cross sections for prompt $\psi$(2S) to J/$\psi$, $\Upsilon$(2S) to $\Upsilon$(1S), and $\Upsilon$(3S) to $\Upsilon$(1S) production.

A measurement of vector boson scattering and constraints on anomalous quartic gauge couplings from events with two Z bosons and two jets are presented. The analysis is based on a data sample of proton-proton collisions at sqrt(s) = 13 TeV collected with the CMS detector and corresponding to an integrated luminosity of 35.9 inverse femtobarns. The search is performed in the fully leptonic final state ZZ to lll'l', where l, l' = e, mu. The electroweak production of two Z bosons in association with two jets is measured with an observed (expected) significance of 2.7 (1.6) standard deviations. A fiducial cross section for the electroweak production is measured to be sigma[EW](pp -> ZZjj -> lll'l'jj) = 0.40 -0.16 +0.21 (stat) -0.09 +0.13 (syst) fb, which is consistent with the standard model prediction. Limits on anomalous quartic gauge couplings are determined in terms of the effective field theory operators T0, T1, T2, T8, and T9. This is the first measurement of vector boson scattering in the ZZ channel at the LHC.

The results of a search for Higgs boson pair (HH) production in the WW*WW*, WW*$\tau\tau$, and $\tau\tau\tau\tau$ decay modes are presented. The search uses 138 fb$^{-1}$ of proton-proton collision data recorded by the CMS experiment at the LHC at a center-of-mass energy of 13 TeV from 2016 to 2018. Analyzed events contain two, three, or four reconstructed leptons, including electrons, muons, and hadronically decaying tau leptons. No evidence for a signal is found in the data. Upper limits are set on the cross section for nonresonant HH production, as well as resonant production in which a new heavy particle decays to a pair of Higgs bosons. For nonresonant production, the observed (expected) upper limit on the cross section at 95% confidence level (CL) is 21.3 (19.4) times the standard model (SM) prediction. The observed (expected) ratio of the trilinear Higgs boson self-coupling to its value in the SM is constrained to be within the interval $-$6.9 to 11.1 ($-$6.9 to 11.7) at 95% CL, and limits are set on a variety of new-physics models using an effective field theory approach. The observed (expected) limits on the cross section for resonant HH production range from 0.18 to 0.90 (0.08 to 1.06) pb at 95% CL for new heavy-particle masses in the range 250-1000 GeV.

A measurement is presented of the associated production of a single top quark and a Z boson. The study uses data from proton-proton collisions at $\sqrt{s} =$ 13 TeV recorded by the CMS experiment, corresponding to an integrated luminosity of 35.9 fb$^{-1}$. Using final states with three leptons (electrons or muons), the tZq production cross section is measured to be $\sigma$(pp$\to$tZq$\to$Wb$\ell^+\ell^-$q) = $123 ^{+33}_{-31}$ (stat) $^{+29}_{-23}$ (syst) fb, where $\ell$ stands for electrons, muons, or $\tau$ leptons, with observed and expected significances of 3.7 and 3.1 standard deviations, respectively.

A measurement of the jet mass distribution in hadronic decays of Lorentz-boosted top quarks is presented. The measurement is performed in the lepton+jets channel of top quark pair production ($\mathrm{t\bar{t}}$) events, where the lepton is an electron or muon. The products of the hadronic top quark decay are reconstructed using a single large-radius jet with transverse momentum greater than 400 GeV. The data were collected with the CMS detector at the LHC in proton-proton collisions and correspond to an integrated luminosity of 138 fb$^{-1}$. The differential $\mathrm{t\bar{t}}$ production cross section as a function of the jet mass is unfolded to the particle level and is used to extract the top quark mass. The jet mass scale is calibrated using the hadronic W boson decay within the large-radius jet. The uncertainties in the modelling of the final state radiation are reduced by studying angular correlations in the jet substructure. These developments lead to a significant increase in precision, and a top quark mass of 173.06 $\pm$ 0.84 GeV.

A search for Higgs bosons that decay into a bottom quark-antiquark pair and are accompanied by at least one additional bottom quark is performed with the CMS detector. The data analyzed were recorded in proton-proton collisions at a centre-of-mass energy of $\sqrt{s} =$ 13 TeV at the LHC, corresponding to an integrated luminosity of 35.7 fb$^{-1}$. The final state considered in this analysis is particularly sensitive to signatures of a Higgs sector beyond the standard model, as predicted in the generic class of two Higgs doublet models (2HDMs). No signal above the standard model background expectation is observed. Stringent upper limits on the cross section times branching fraction are set for Higgs bosons with masses up to 1300 GeV. The results are interpreted within several MSSM and 2HDM scenarios.