Search for resonance-enhanced CP and angular asymmetries in the Λc+→pμ+μ− decay at LHCb

The first measurement of the CP asymmetry of the decay rate (ACP) and the CP average (ΣAFB) and CP asymmetry (ΔAFB) of the forward-backward asymmetry in the muon system of Λþ c → pμþμ− decays is reported. The measurement is performed using a data sample of proton-proton collisions, recorded by the LHCb experiment from 2016 to 2018 at a center-of-mass energy of 13 TeV, which corresponds to an integrated luminosity of 5.4 fb−1. The asymmetries are measured in two regions of dimuon mass near the φ-meson mass peak. The dimuon-mass integrated results are ACP 1⁄4 ð−1.1 4.0 0.5Þ%, ΣAFB 1⁄4 ð3.9 4.0 0.6Þ%, ΔAFB 1⁄4 ð3.1 4.0 0.4Þ%, where the first uncertainty is statistical and the second systematic. The results are consistent with the conservation of CP symmetry and the Standard Model expectations

Search for D0 meson decays to π+π−e+e− and K+K−e+e− final states

A search for D0 meson decays to the πþπ−eþe− and KþK−eþe− final states is reported using a sample of proton-proton collisions collected by the LHCb experiment at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 6 fb−1. The decay D0 → πþπ−eþe− is observed for the first time when requiring that the two electrons are consistent with coming from the decay of a φ or ρ0=ω meson. The corresponding branching fractions are measured relative to the D0 → K−π−1⁄2eþe−ρ0=ω decay, where the two electrons are consistent with coming from the decay of a ρ0 or ω meson. No evidence is found for the D0 → KþK−eþe− decay and world-best limits are set on its branching fraction. The results are compared to, and found to be consistent with, the branching fractions of the D0 → πþπ−μþμ− and D0 → KþK−μþμ− decays recently measured by LHCb and confirm lepton universality at the current precision

Test of Lepton Flavor Universality with B+→K+π+π−l+l− Decays

The first test of lepton flavor universality between muons and electrons using Bþ → Kþπþπ−lþl− (l 1⁄4 e, μ) decays is presented. The measurement is performed with data from proton-proton collisions collected by the LHCb experiment at center-of-mass energies of 7, 8, and 13 TeV, corresponding to an integrated luminosity of 9 fb−1. The ratio of branching fractions between Bþ → Kþπþπ−eþe− and Bþ → Kþπþπ−μþμ− decays is measured in the dilepton invariant-mass-squared range 1.1 < q2 < 7.0 GeV2=c4 and is found to be R−1 Kππ 1⁄4 1.31þ0.18 −0.17 ðstatÞ þ0.12 −0.09 ðsystÞ, in agreement with the standard model prediction. The first observation of the Bþ → Kþπþπ−eþe− decay is also reporte

Probing the nature of the χc1(3872)\chi_{c1}(3872) state using radiative decays

The radiative decays $\chi_{c1}(3872)\rightarrow\psi(2S)\gamma$ and $\chi_{c1}(3872)\rightarrow J/\psi\gamma$ are used to probe the~nature of the~$\chi_{c1}(3872)$ state using proton-proton collision data collected with the LHCb detector, corresponding to an~integrated luminosity of~9fb$^{-1}$. Using the~$B^+\rightarrow \chi_{c1}(3872)K^+$decay, the $\chi_{c1}(3872)\rightarrow \psi(2S)\gamma$ process is observed for the first time and the ratio of its partial width to that of the $\chi_{c1}(3872)\rightarrow J/\psi\gamma$ decay is measured to be $$\frac{\Gamma_{\chi_{c1}(3872)\rightarrow \psi(2S)\gamma}} {\Gamma_{\chi_{c1}(3872)\rightarrow J/\psi\gamma}} = 1.67 \pm 0.21 \pm 0.12 \pm0.04 ,$$ where the first uncertainty is statistical, the second systematic and the third is due to the uncertainties on the branching fractions of the $\psi(2S)$ and $J/\psi$ mesons. The measured ratio makes the interpretation of the $\chi_{c1}(3872)$ state as a~pure $D^0\bar{D}^{*0}+\bar{D}^0D^{*0}$ molecule questionable and strongly indicates a sizeable compact charmonium or tetraquark component within the $\chi_{c1}(3872)$ state.Comment: 31 pages, 2 figures. All figures and tables, along with any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2024-015.html (LHCb public pages

Test of Lepton Flavor Universality with B+ →k+π+π-l+l- Decays

The first test of lepton flavor universality between muons and electrons using B+→K+π+π-l+l- (l=e, μ) decays is presented. The measurement is performed with data from proton-proton collisions collected by the LHCb experiment at center-of-mass energies of 7, 8, and 13 TeV, corresponding to an integrated luminosity of 9 fb-1. The ratio of branching fractions between B+→K+π+π-e+e- and B+→K+π+π-μ+μ- decays is measured in the dilepton invariant-mass-squared range 1.1<7.0 GeV2/c4 and is found to be RKππ-1=1.31-0.17+0.18(stat) -0.09+0.12(syst), in agreement with the standard model prediction. The first observation of the B+→K+π+π-e+e- decay is also reported

Measurement of CP asymmetries in Λb0→ph− decays

A search for CP violation in Λ0 b → pK− and Λ0 b → pπ− decays is presented using the full Run 1 and Run 2 data samples of pp collisions collected with the LHCb detector, corresponding to an integrated luminosity of 9 fb−1 at center-of-mass energies of 7, 8, and 13 TeV. For the Run 2 data sample, the CPviolating asymmetries are measured to be ApK− CP 1⁄4 ð−1.4 0.7 0.4Þ% and Apπ− CP 1⁄4 ð0.4 0.9 0.4Þ%, where the first uncertainty is statistical and the second is systematic. Following significant improvements in the evaluation of systematic uncertainties compared to the previous LHCb measurement, the Run 1 dataset is reanalyzed to update the corresponding results. When combining the Run 2 and updated Run 1 measurements, the final results are found to be ApK− CP 1⁄4 ð−1.1 0.7 0.4Þ% and Apπ− CP 1⁄4 ð0.2 0.8 0.4Þ%, constituting the most precise measurements of these asymmetries to date

Measurement of the CKM angle γ in B± → DK*(892)± decays

Measurements of CP observables and the CKM angle γ are performed in B± → DK∗ (892)± decays, where D represents a superposition of D0 and D 0 states, using the LHCb dataset collected during Run 1 (2011–2012) and Run 2 (2015–2018). A study of this channel is presented with the D meson reconstructed in two-body fnal states K±π ∓, K+K− and π +π −; four-body fnal states K±π ∓π ±π ∓ and π +π −π +π −; and threebody fnal states K0 S π +π − and K0 SK+K−. This analysis includes the frst observation of the suppressed B± → [π ±K∓]DK∗± and B± → [π ±K∓π ±π ∓]DK∗± decays. The combined result gives γ = (63 ± 13)◦

Measurement of CP Violation Observables in D+→K−K+π+ Decays

A search for violation of the charge-parity (CP) symmetry in the D+→K-K+π+ decay is presented, with proton-proton collision data corresponding to an integrated luminosity of 5.4 fb-1, collected at a center-of-mass energy of 13 TeV with the LHCb detector. A novel model-independent technique is used to compare the D+ and D- phase-space distributions, with instrumental asymmetries subtracted using the Ds+→K-K+π+ decay as a control channel. The p value for the hypothesis of CP conservation is 8.1%. The CP asymmetry observables ACP|Sφπ+=(0.95±0.43stat±0.26syst)×10-3 and ACP|SK̄∗0K+=(-0.26±0.56stat±0.18syst)×10-3 are also measured. These results show no evidence of CP violation and represent the most sensitive search performed through the phase space of a multibody decay

Measurements of ψ(2S) and χc1(3872) production within fully reconstructed jets

This paper presents the first measurement of ψ(2S) and χc1(3872) meson production within fully reconstructed jets. Each quarkonium state (tag) is reconstructed via its decay to the J/ψ(→μ+μ−)π+π− final state in the forward region using proton-proton collision data collected by the LHCb experiment at the center-of-mass-energy of 13TeV in 2016, corresponding to an integrated luminosity of 1.64 fb−1. The fragmentation function, presented as the ratio of the quarkonium-tag transverse momentum to the full jet transverse momentum (pT(tag)/pT(jet)), is measured differentially in pT(jet) and pT(tag) bins. The distributions are separated into promptly produced quarkonia from protonproton collisions and quarkonia produced from displaced b-hadron decays. While the displaced quarkonia fragmentation functions are in general well described by parton-shower predictions, the prompt quarkonium distributions differ significantly from fixed-order non-relativistic QCD (NRQCD) predictions followed by a QCD parton showe

Observation of muonic Dalitz decays of chib mesons and precise spectroscopy of hidden-beauty states

The decays of the χb1(1P), χb2(1P), χb1(2P) and χb2(2P) mesons into the Υ(1S)μ+μ− final state are observed with a high significance using proton-proton collision data collected with the LHCb detector and corresponding to an integrated luminosity of 9 fb−1. The newly observed decays together with the Υ(2S) → Υ(1S)π+π− and Υ(3S) → Υ(2S)π+π− decay modes are used for precision measurements of the mass and mass splittings for the hidden-beauty states