The first search for scalar leptoquarks produced in $\tau$-lepton-quark collisions is presented. It is based on a set of proton-proton collision data recorded with the CMS detector at the LHC at a center-of-mass energy of 13 TeV corresponding to an integrated luminosity of 138 fb$^{-1}$. The reconstructed final state consists of a jet, significant missing transverse momentum, and a $\tau$ lepton reconstructed through its hadronic or leptonic decays. Limits are set on the product of the leptoquark production cross section and branching fraction and interpreted as exclusions in the plane of the leptoquark mass and the leptoquark-$\tau$-quark coupling strength.

A search for long-lived particles (LLPs) decaying in the CMS muon detectors is presented. A data sample of proton-proton collisions at $\sqrt{s}$ = 13 TeV corresponding to an integrated luminosity of 138 fb$^{-1}$ recorded at the LHC in 2016-2018, is used. The decays of LLPs are reconstructed as high multiplicity clusters of hits in the muon detectors. In the context of twin Higgs models, the search is sensitive to LLP masses from 0.4 to 55 GeV and a broad range of LLP decay modes, including decays to hadrons, $\tau$ leptons, electrons, or photons. No excess of events above the standard model background is observed. The most stringent limits to date from LHC data are set on the branching fraction of the Higgs boson decay to a pair of LLPs with masses below 10 GeV. This search also provides the best limits for various intervals of LLP proper decay length and mass. Finally, this search sets the first limits at the LHC on a dark quantum chromodynamic sector whose particles couple to the Higgs boson through gluon, Higgs boson, photon, vector, and dark-photon portals, and is sensitive to branching fractions of the Higgs boson to dark quarks as low as 2 $\times$ 10$^{-3}$.

A search for a heavy pseudoscalar Higgs boson, A, decaying to a 125 GeV Higgs boson h and a Z boson is presented. The h boson is identified via its decay to a pair of tau leptons, while the Z boson is identified via its decay to a pair of electrons or muons. The search targets the production of the A boson via the gluon-gluon fusion process, gg $\to$ A, and in association with bottom quarks, $\mathrm{b\bar{b}}$A. The analysis uses a data sample corresponding to an integrated luminosity of 138 fb$^{-1}$ collected with the CMS detector at the CERN LHC in proton-proton collisions at a centre-of-mass energy of $\sqrt{s}$ = 13 TeV. Constraints are set on the product of the cross sections of the A production mechanisms and the A $\to$ Zh decay branching fraction. The observed (expected) upper limit at 95% confidence level ranges from 0.049 (0.060) pb to 1.02 (0.79) pb for the gg $\to$ A process and from 0.053 (0.059) pb to 0.79 (0.61) pb for the $\text{b}\bar{\text{b}}$A process in the probed range of the A boson mass, $m_\text{A}$, from 225 GeV to 1 TeV. The results of the search are used to constrain parameters within the ${\text{M}_{\text{h,EFT}}^{\text{125}}}$ benchmark scenario of the minimal supersymmetric extension of the standard model. Values of $\tanβ$ below 2.2 are excluded in this scenario at 95% confidence level for all $m_\text{A}$ values in the range from 225 to 350 GeV.

Incoherent J/$ψ$ photoproduction in heavy ion ultraperipheral collisions (UPCs) provides a sensitive probe of localized, fluctuating gluonic structures within heavy nuclei. This study reports the first measurement of the photon-nucleon center-of-mass energy ($W_{γ\mathrm{N}}$) dependence of this process in PbPb UPCs at a nucleon-nucleon center-of-mass energy of 5.02 TeV, using 1.52 nb$^{-1}$ of data recorded by the CMS experiment. The measurement covers a wide $W_{γ\mathrm{N}}$ range of $\approx$ 40-400 GeV, probing gluons carrying a fraction $x$ of nucleon momentum down to an unexplored region of 6.5 $\times$ 10$^{-5}$. Compared to baseline predictions neglecting nuclear effects, the measured cross sections exhibit significantly greater suppression at lower $x$. Additionally, the ratio of incoherent to coherent photoproduction is found to be constant across the probed $W_{γ\mathrm{N}}$ and $x$ range, disfavoring the establishment of the black disk limit. This study provides critical insights into the $x$-dependent evolution of fluctuating gluonic structures within nuclei and calls for further advancements in theoretical models incorporating nuclear shadowing and gluon saturation.

A search for $γ$H production is performed with data from the CMS experiment at the LHC corresponding to an integrated luminosity of 138 fb$^{-1}$ at a proton-proton center-of-mass collision energy of 13 TeV. The analysis focuses on the topology of a boosted Higgs boson recoiling against a high-energy photon. The final states of H $\to$$\mathrm{b\bar{b}}$ and H $\to$ 4$\ell$ are analyzed. This study examines effective HZ$γ$ and H$γγ$ anomalous couplings within the context of an effective field theory. In this approach, the production cross section is constrained to be $σ_{γ\text{H}}$$\lt$ 16.4 fb at 95% confidence level (CL). Simultaneous constraints on four anomalous couplings involving HZ$γ$ and H$γγ$ are provided. Additionally, the production rate for H $\to$ 4$\ell$ is examined to assess potential enhancements in the Yukawa couplings between light quarks and the Higgs boson. Assuming the standard model values for the Yukawa couplings of the bottom and top quarks, the following simultaneous constraints are obtained: $κ_\text{u}$ = (0.0 $\pm$ 1.5) $\times$ 10$^{3}$, $κ_\text{d}$ = (0.0 $^{+6.7}_{-6.8}$) $\times$ 10$^{2}$, $κ_\text{s}$ = 0 $^{+30}_{-32}$, and $κ_\text{c}$ = 0.0 $^{+2.3}_{-2.8}$. This rules out the hypothesis that up- or down-type quarks in the first or second generation have the same Yukawa couplings as those in the third generation, with a CL greater than 95%.

A search is presented for an extended Higgs sector with two new particles, X and $\phi$, in the process $X \to\phi\phi\to(\gamma\gamma)(\gamma\gamma)$. Novel neural networks classify events with diphotons that are merged and determine the diphoton masses. The search uses LHC proton-proton collision data at $\sqrt{s}$ = 13 TeV collected with the CMS detector, corresponding to an integrated luminosity of 138 fb$^{-1}$. No evidence of such resonances is seen. Upper limits are set on the production cross section for $m_X$ between 300 and 3000 GeV and $m_\phi / m_X$ between 0.5 and 2.5%, representing the most sensitive search in this channel.

A measurement of the Higgs boson mass and width via its decay to two Z bosons is presented. Proton-proton collision data collected by the CMS experiment, corresponding to an integrated luminosity of 138 fb$^{-1}$ at a center-of-mass energy of 13 TeV is used. The invariant mass distribution of four leptons in the on-shell Higgs boson decay is used to measure its mass and constrain its width. This yields the most precise single measurement of the Higgs boson mass to date, 125.04 $\pm$ 0.12 GeV, and an upper limit on the width $\Gamma_\mathrm{H}$$\lt$ 330 MeV at 95% confidence level. A combination of the on- and off-shell Higgs boson production decaying to four leptons is used to determine the Higgs boson width, assuming that no new virtual particles affect the production, a premise that is tested by adding new heavy particles in the gluon fusion loop model. This result is combined with a previous CMS analysis of the off-shell Higgs boson production with decay to two leptons and two neutrinos, giving a measured Higgs boson width of 3.0 $^{+2.0}_{-1.5}$ MeV, in agreement with the standard model prediction of 4.1 MeV. The strength of the off-shell Higgs boson production is also reported. The scenario of no off-shell Higgs boson production is excluded at a confidence level corresponding to 3.8 standard deviations.

Measurements of fiducial and total inclusive cross sections for W and Z boson production are presented in proton-proton collisions at $\sqrt{s}$ = 5.02 and 13 TeV. Electron and muon decay modes ($\ell$ = e or $\mu$) are studied in the data collected with the CMS detector in 2017, in dedicated runs with reduced instantaneous luminosity. The data sets correspond to integrated luminosities of 298 $\pm$ 6 pb$^{-1}$ at 5.02 TeV and 206 $\pm$ 5 pb$^{-1}$ at 13 TeV. Measured values of the products of the total inclusive cross sections and the branching fractions at 5.02 TeV are $\sigma$(pp $\to$ W+X) $\mathcal{B}$(W $\to$$\ell\nu$) = 7300 $\pm$ 10 (stat) $\pm$ 60 (syst) $\pm$ 140 (lumi) pb, and $\sigma$(pp $\to$ Z+X) $\mathcal{B}$(Z $\to$$\ell^+\ell^-$) = 669 $\pm$ 2 (stat) $\pm$ 6 (syst) $\pm$ 13 (lumi) pb for the dilepton invariant mass in the range of 60-120 GeV. The corresponding results at 13 TeV are 20480 $\pm$ 10 (stat) $\pm$ 170 (syst) $\pm$ 470 (lumi) pb and 1952 $\pm$ 4 (stat) $\pm$ 18 (syst) $\pm$ 45 (lumi) pb. The measured values agree with cross section calculations at next-to-next-to-leading-order in perturbative quantum chromodynamics. Fiducial and total inclusive cross sections, ratios of cross sections of W$^+$ and W$^-$ production as well as inclusive W and Z boson production, and ratios of these measurements at 5.02 and 13 TeV are reported.

Searches for pair-produced multijet signatures using data corresponding to an integrated luminosity of 128 fb$^{-1}$ of proton-proton collisions at $\sqrt{s}$ = 13 TeV are presented. A data scouting technique is employed to record events with low jet scalar transverse momentum sum values. The electroweak production of particles predicted in $R$-parity violating supersymmetric models is probed for the first time with fully hadronic final states. This is the first search for prompt hadronically decaying mass-degenerate higgsinos, and extends current exclusions on $R$-parity violating top squarks and gluinos.

The production cross sections of B$^0_\mathrm{s}$ and B$^+$ mesons are reported in proton-proton (pp) collisions recorded by the CMS experiment at the CERN LHC with a center-of-mass energy of 5.02 TeV. The data sample corresponds to an integrated luminosity of 302 pb$^{-1}$. The cross sections are based on measurements of the B$^0_\mathrm{s}$$\to$ J/$ψ(μ^+μ^-)ϕ$(1020) (K$^+$K$^-$) and B$^+$$\to$ J/$ψ(μ^+μ^-)$K$^+$ decay channels. Results are presented in the transverse momentum ($p_\mathrm{T}$) range 7-50 GeV/$c$ and the rapidity interval $\lvert y \rvert$$\lt$ 2.4 for the B mesons. The measured $p_\mathrm{T}$-differential cross sections of B$^+$ and B$^0_\mathrm{s}$ in pp collisions are well described by fixed-order plus next-to-leading logarithm perturbative quantum chromodynamics calculations. Using previous PbPb collision measurements at the same nucleon-nucleon center-of-mass energy, the nuclear modification factors, $R_\mathrm{AA}$, of the B mesons are determined. For $p_\mathrm{T}$$\lt$ 10 GeV/$c$, both mesons are found to be suppressed in PbPb collisions (with $R_\mathrm{AA}$ values significantly below unity), with less suppression observed for the B$^0_\mathrm{s}$ mesons. In this $p_\mathrm{T}$ range, the $R_\mathrm{AA}$ values for the B$^+$ mesons are consistent with those for inclusive charged hadrons and D$^0$ mesons. Below 10 GeV/$c$, both B$^+$ and B$^0_\mathrm{s}$ are found to be less suppressed than either inclusive charged hadrons or D$^0$ mesons, with the B$^0_\mathrm{s}$$R_\mathrm{AA}$ value consistent with unity. The $R_\mathrm{AA}$ values found for the B$^+$ and B$^0_\mathrm{s}$ are compared to theoretical calculations, providing constraints on the mechanism of bottom quark energy loss and hadronization in the quark-gluon plasma, the hot and dense matter created in ultrarelativistic heavy ion collisions.