CMS Publications#CMSPAS: Observation of a peaking structure in the Y(1S)phi(1020) channel in proton-proton collisions at sqrt(s) = 13 TeV (CMS-PAS-BPH-25-009) https://cds.cern.ch/record/2961554 #BPhysics
#CMSpaper: Observation of the rare decay η → μ⁺μ⁻e⁺e⁻ (arXiv:2605.00615) https://arxiv.org/abs/2605.00615 #BPhysics
Observation of the rare decay $η$ $\to$ $μ^+μ^-$e$^+$e$^-$
A first observation of the rare decay $η$ $\to$ $μ^+μ^-$e$^+$e$^-$ is reported by the CMS Collaboration at the CERN LHC. The result is based on a proton-proton collision data sample at $\sqrt{s}$ = 13.6 TeV corresponding to an integrated luminosity of 38.0 fb$^{-1}$, acquired in 2022 using a high-rate dimuon trigger. Using the $η$ $\to$ $μ^+μ^-γ$ decay channel for normalization, the branching fraction is measured to be $\mathcal{B}$($η$ $\to$ $μ^+μ^-$e$^+$e$^-$) = (2.4 $\pm$ 0.8)$\times$ 10$^{-6}$, with the uncertainty including statistical and systematic sources as well as the $\mathcal{B}$($η$ $\to$ $μ^+μ^-γ$) uncertainty. This result is close to two orders of magnitude smaller than the existing limit, and is consistent with recent theoretical predictions.
#CMSpaper soon on arXiv: Observation of the rare decay η → μ⁺μ⁻e⁺e⁻ (CERN-EP-2026-023) https://cds.cern.ch/record/2960487 #BPhysics
#CMSPAS: Measurement of angular observables and differential branching fraction for BsToPhiMuMu at 13 TeV (CMS-PAS-BPH-23-003) https://cds.cern.ch/record/2957485 #Moriond #BPhysics
#CMSPAS: Search for the rare B⁰_s (B⁰) → μ⁺ μ⁻ μ⁺ μ⁻ decays in proton-proton collisions (CMS-PAS-BPH-24-007) https://cds.cern.ch/record/2957483 #Moriond #BPhysics
#CMSPAS: Search for the lepton flavor violating τ → 3μ decay in proton-proton collisions at √s = 13.6 TeV (CMS-PAS-BPH-24-010) https://cds.cern.ch/record/2957462 #Moriond #BPhysics
#CMSpaper: Measurement of B meson production fraction ratios in proton-proton collisions at √s = 13 TeV using open-charm and charmonium decays (arXiv:2602.10270) https://arxiv.org/abs/2602.10270 #BPhysics
Measurement of B meson production fraction ratios in proton-proton collisions at $\sqrt{s}$ = 13 TeV using open-charm and charmonium decays
Production fraction ratios of B$^+$, B$^0$, and B$^0_\mathrm{s}$ mesons are measured in proton-proton collisions at $\sqrt{s}$ = 13 TeV using a special data set recorded in 2018 with high-rate triggers designed to collect an unbiased sample of $10^{10}$ b hadrons with the CMS experiment at the LHC. These data allow the use of the open-charm decays of B mesons (B$_\mathrm{(s)}$ $\to$ $π$D$_\mathrm{(s)}$) where the D meson decays into fully hadronic final states. Production fraction ratios as functions of B meson transverse momentum ($p_\mathrm{T}$) and rapidity ($y$) are measured using the open-charm decays in the kinematic range of 8 $\lt$ $p_\mathrm{T}$ $\lt$ 60 GeV and $\lvert y \rvert$ $\lt$ 2.25. In addition, the same data are used to measure the relative production fraction ratios with the charmonium decay channels (B$_\mathrm{(s)}$ $\to$ X$\,$J/$ψ$ with X indicating a K$^+$, K$^*$(892)$^0$, or $ϕ$(1020) meson) with the J/$ψ$ meson decaying into a pair of muons. By utilizing known branching fractions, precision theoretical calculations, and the open-charm results, the production fraction ratios in the charmonium samples are determined with an absolute normalization for the first time. These results also improve several world-average values of the ratios of branching fractions of B meson decays to charmonium and open-charm states. Finally, we test isospin invariance in B meson production in proton-proton collisions and observe that it holds within the experimental precision.
#CMSpaper soon on arXiv: Measurement of B meson production fraction ratios in proton-proton collisions at √s = 13 TeV using open-charm and charmonium decays (CERN-EP-2025-176) https://cds.cern.ch/record/2954592 #BPhysics
Measurement of $ {\mathrm{B}} $ meson production fraction ratios in proton-proton collisions at $ \sqrt{s} = $ 13 TeV using open-charm and charmonium decays
Production fraction ratios of $ {\mathrm{B}^{+}} $, $ {\mathrm{B}^0} $, and $ \mathrm{B}_{s}^{0} $ mesons are measured in proton-proton collisions at $ \sqrt{s} = $ 13 TeV using a special data set recorded in 2018 with high-rate triggers designed to collect an unbiased sample of $ 10^{10} \mathrm{b} $ hadrons with the CMS experiment at the LHC\@. These data allow the use of the open-charm decays of $ {\mathrm{B}} $ mesons ($ {\mathrm{B}}_{(\mathrm{s})} \!\to\! \pi\mathrm{D}_{(\mathrm{s})} $) where the $ \mathrm{D} $ meson decays into fully hadronic final states. Production fraction ratios as functions of $ {\mathrm{B}} $ meson transverse momentum ($ p_{\mathrm{T}} $) and rapidity ($ y $) are measured using the open-charm decays in the kinematic range of 8 $ < p_{\mathrm{T}} < $ 60 GeV and $ |y| < $ 2.25. In addition, the same data are used to measure the relative production fraction ratios with the charmonium decay channels ($ {\mathrm{B}}_{(\mathrm{s})} \!\to\! \mathrm{X}{\mathrm{J}/\psi} $ with $ \mathrm{X} $ indicating a $ \mathrm{K^+} $, $ \mathrm{K^*}(892)^0 $, or $ \phi(1020) $ meson) with the $ {\mathrm{J}/\psi} $ meson decaying into a pair of muons. By utilizing known branching fractions, precision theoretical calculations, and the open-charm results, the production fraction ratios in the charmonium samples are determined with an absolute normalization for the first time. These results also improve several world-average values of the ratios of branching fractions of $ {\mathrm{B}} $ meson decays to charmonium and open-charm states. Finally, we test isospin invariance in $ {\mathrm{B}} $ meson production in proton-proton collisions and observe that it holds within the experimental precision.
#CMSpaper: Observation of Υ(1S) + Z associated production and measurement of the effective double-parton scattering cross section in proton-proton collisions at √s = 13 TeV (arXiv:2602.02770) https://arxiv.org/abs/2602.02770 #BPhysics
Observation of $Υ$(1S) + Z associated production and measurement of the effective double-parton scattering cross section in proton-proton collisions at $\sqrt{s}$ = 13 TeV
The observation of associated production of an $Υ$(1S) meson with a Z boson and a measurement of the ratio of its fiducial cross section to the fiducial cross section of the Z boson are presented. Both the $Υ$(1S) meson and the Z boson are identified via decays into a pair of opposite-sign muons. The analysis is based on proton-proton (pp) collision data at $\sqrt{s}$ = 13 TeV, collected with the CMS detector in 2016$-$2018 and corresponding to an integrated luminosity of 138 fb$^{-1}$. Using the production of the Z boson decaying into four muons as a normalization channel, the ratio of the fiducial cross sections $σ$(pp $\to$ Z $+$ $Υ$(1S))$\mathcal{B}$(Z $\to$ $μ^+μ^-$)$\mathcal{B}$($Υ$(1S) $\to$ $μ^+μ^-$ ) to $σ$(pp $\to$ Z)$\mathcal{B}$(Z $\to$ 4$μ$) is measured to be $\mathcal{R}_{\mathrm{Z+Υ}\mathrm{(1S)}}$ = (21.1 $\pm$ 55 (stat) $\pm$ 0.6 (syst) $\times$ 10$^{-3}$), where stat and syst denote the statistical and systematic uncertainties, respectively. The result is used to extract the effective double-parton scattering cross section $σ_\text{eff}$ = 13.0$^{+7.7}_{-3.4}$. In addition, for the first time, $σ_\text{eff}$ is measured in bins of the transverse momentum of the $Υ$(1S) meson or of the Z boson.
#CMSpaper soon on arXiv: Observation of Υ(1S) + Z associated production and measurement of the effective double-parton scattering cross section in proton-proton collisions at √s = 13 TeV (CERN-EP-2025-163) https://cds.cern.ch/record/2954080 #BPhysics
Observation of $ \Upsilon\mathrm{(1S)} $ + Z associated production and measurement of the effective double-parton scattering cross section in proton-proton collisions at $ \sqrt{s}= $ 13 TeV
The observation of associated production of an $ \Upsilon\mathrm{(1S)} $ meson with a Z boson and a measurement of the ratio of its fiducial cross section to the fiducial cross section of the Z boson are presented. Both the $ \Upsilon\mathrm{(1S)} $ meson and the Z boson are identified via decays into a pair of opposite-sign muons. The analysis is based on proton-proton (pp) collision data at $ \sqrt{s}= $ 13 TeV, collected with the CMS detector in 2016--2018 and corresponding to an integrated luminosity of 138 fb$ ^{-1} $. Using the production of the Z boson decaying into four muons as a normalization channel, the ratio of the fiducial cross sections $ \sigma(\mathrm{p}\mathrm{p}\to\mathrm{Z}+\Upsilon\mathrm{(1S)}) \mathcal{B}(\mathrm{Z}\to\mu^{+}\mu^{-}) \mathcal{B}(\Upsilon\mathrm{(1S)}\to\mu^{+}\mu^{-}) $ to $ \sigma(\mathrm{p}\mathrm{p}\to\mathrm{Z})\mathcal{B}(\mathrm{Z}\to4\mu) $ is measured to be $ \mathcal{R}_{\mathrm{Z}+ \Upsilon\mathrm{(1S)}}=( $ 21.1 $ \pm $ 5.5 (stat) $ \pm $ 0.6 (syst) $) \times 10^{-3} $, where stat and syst denote the statistical and systematic uncertainties, respectively. The result is used to extract the effective double-parton scattering cross section $ \sigma_\text{eff} = $ 13.0 $ ^{+7.7}_{-3.4} $ $ $ mb. In addition, for the first time, $ \sigma_\text{eff} $ is measured in bins of the transverse momentum of the $ \Upsilon\mathrm{(1S)} $ meson or of the Z boson.