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A<sc>bstract</sc> A search for the decay$$ {B}_c^{+} $$ $B_c^{+}$→ χ_c1(3872)π⁺is reported using proton-proton collision data collected with the LHCb detector between 2011 and 2018 at centre-of-mass energies of 7, 8, and 13 TeV, corresponding to an integrated luminosity of 9 fb⁻¹. No significant signal is observed. Using the decay$$ {B}_c^{+} $$ $B_c^{+}$→ψ(2S)π⁺as a normalisation channel, an upper limit for the ratio of branching fractions$$ {\mathcal{R}}_{\psi (2S)}^{\chi_{c1}(3872)}=\frac{{\mathcal{B}}_{B_c^{+}\to {\chi}_{c1}(3872){\pi}^{+}}}{{\mathcal{B}}_{B_c^{+}\to \psi (2S){\pi}^{+}}}\times \frac{{\mathcal{B}}_{\chi_{c1}(3872)\to J/\psi {\pi}^{+}{\pi}^{-}}}{{\mathcal{B}}_{\psi (2S)\to J/\psi {\pi}^{+}{\pi}^{-}}}<0.05(0.06), $$ $R_{\psi \left(2S\right)}^{{\chi }_{c1}\left(3872\right)}=\frac{B_{B_c^{+}\to {\chi }_{c1}\left(3872\right){\pi }^{+}}}{B_{B_c^{+}\to \psi \left(2S\right){\pi }^{+}}}\times \frac{B_{{\chi }_{c1}\left(3872\right)\to J/\psi {\pi }^{+}{\pi }^{-}}}{B_{\psi \left(2S\right)\to J/\psi {\pi }^{+}{\pi }^{-}}}<0.05\left(0.06\right),$ is set at the 90 (95)% confidence level. 

Abstract This paper presents the first measurement of$$\psi {(2S)}$$ $\psi \left(2S\right)$and$$\chi _{c1}(3872)$$ ${\chi }_{c1}\left(3872\right)$meson production within fully reconstructed jets. Each quarkonium state (tag) is reconstructed via its decay to the$${{J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }} $$ $J/\psi$($$\rightarrow $$ $\to$$$\mu ^+\mu ^-$$ ${\mu }^{+}{\mu }^{-}$)$$\pi ^+\pi ^-$$ ${\pi }^{+}{\pi }^{-}$final state in the forward region using proton-proton collision data collected by the LHCb experiment at the center-of-mass-energy of$$13\text {TeV} $$ $13\text{TeV}$in 2016, corresponding to an integrated luminosity of$$1.64\,\text {\,fb} ^{-1} $$ $1.64{\text{,fb}}^{-1}$. The fragmentation function, presented as the ratio of the quarkonium-tag transverse momentum to the full jet transverse momentum ($$p_{\textrm{T}} (\text {tag})/p_{\textrm{T}} (\text {jet})$$ $p_{\text{T}}\left(\text{tag}\right)/p_{\text{T}}\left(\text{jet}\right)$), is measured differentially in$$p_{\textrm{T}} (\text {jet})$$ $p_{\text{T}}\left(\text{jet}\right)$and$$p_{\textrm{T}} (\text {tag})$$ $p_{\text{T}}\left(\text{tag}\right)$bins. The distributions are separated into promptly produced quarkonia from proton-proton collisions and quarkonia produced from displacedb-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 shower. 

Lepton flavor universality in rare $b\to s$transitions is tested for the first time using $B_s^0$meson decays. The measurements are performed using $pp$collision data collected by the LHCb experiment between 2011 and 2018, corresponding to a total integrated luminosity of $9{\mathrm{fb}}^{-1}$. Branching fraction ratios between the $B_s^0\to \varphi e^{+}{e}^{-}$and $B_s^0\to \varphi {\mu }^{+}{\mu }^{-}$decays are measured in three regions of dilepton mass squared, $q^2$, with $0.1<q^2<1.1$, $1.1<q^2<6.0$, and $15<q^2<19{\mathrm{GeV}}^2/c^4$. The results agree with the standard model expectation of lepton flavor universality. © 2025 CERN, for the LHCb Collaboration2025CERN 

A<sc>bstract</sc> Measurements ofCPobservables and the CKM angleγare performed inB^±→DK^*(892)^±decays, whereDrepresents a superposition ofD⁰and$$ {\overline{D}}^0 $$ ${\overline{D}}^0$states, using the LHCb dataset collected during Run 1 (2011–2012) and Run 2 (2015–2018). A study of this channel is presented with theDmeson reconstructed in two-body final statesK^±π^∓,K⁺K⁻andπ⁺π⁻; four-body final statesK^±π^∓π^±π^∓andπ⁺π⁻π⁺π⁻; and three-body final states$$ {K}_{\textrm{S}}^0{\pi}^{+}{\pi}^{-} $$ $K_S^0{\pi }^{+}{\pi }^{-}$and$$ {K}_{\textrm{S}}^0{K}^{+}{K}^{-} $$ $K_S^0{K}^{+}{K}^{-}$. This analysis includes the first observation of the suppressedB^±→[π^±K^∓]_DK^*±andB^±→[π^±K^∓π^±π^∓]_DK^*±decays. The combined result givesγ= (63±13)°. 

Abstract Charged-particle trajectories are usually reconstructed with the LHCb detector using combined information from the tracking devices placed upstream and downstream of the 4 T m dipole magnet. Trajectories reconstructed using only information from the tracker downstream of the dipole magnet, which are referred to as T tracks, have not been used for physics analysis to date. The challenges of the reconstruction of long-lived particles with T tracks for physics use are discussed and solutions are proposed. The feasibility and the tracking performance are studied using samples of long-lived$${\Lambda }$$ $\Lambda$and$$K_S^0$$ $K_S^0$hadrons decaying between 6.0 and 7.6 m downstream of the proton–proton collision point, thereby traversing most of the magnetic field region and providing maximal sensitivity to magnetic and electric dipole moments. The reconstruction can be expanded upstream to about 2.5 m for use in direct searches of exotic long-lived particles. The data used in this analysis have been recorded between 2015 and 2018 and correspond to an integrated luminosity of 6 $$\hbox {fb}^{-1}$$ ${\text{fb}}^{-1}$. The results obtained demonstrate the possibility to further extend the decay volume and the physics reach of the LHCb experiment. 

Abstract A search for the very rare$$B^{*0}\rightarrow \mu ^+\mu ^-$$ $B_{}^{\ast 0}\to {\mu }^{+}{\mu }^{-}$and$$B_{s}^{*0}\rightarrow \mu ^+\mu ^-$$ $B_s^{\ast 0}\to {\mu }^{+}{\mu }^{-}$decays is conducted by analysing the$$B_c^+\rightarrow \pi ^+\mu ^+\mu ^-$$ $B_c^{+}\to {\pi }^{+}{\mu }^{+}{\mu }^{-}$process. The analysis uses proton-proton collision data collected with the LHCb detector between 2011 and 2018, corresponding to an integrated luminosity of 9$$\text {\,fb}^{-1}$$ ${\text{,fb}}^{-1}$. The signal signatures correspond to simultaneous peaks in the$$\mu ^+\mu ^-$$ ${\mu }^{+}{\mu }^{-}$and$$\pi ^+\mu ^+\mu ^-$$ ${\pi }^{+}{\mu }^{+}{\mu }^{-}$invariant masses. No evidence for an excess of events over background is observed for either signal decay mode. Upper limits at the$$90\%$$ $90\%$confidence level are set on the branching fractions relative to that for$$B_c^+\rightarrow J\hspace{-1.66656pt}/\hspace{-1.111pt}\psi \pi ^+$$ $B_c^{+}\to J/\psi {\pi }^{+}$decays,$$\begin{aligned} \mathcal{R}_{B^{*0}(\mu ^+\mu ^-)\pi ^+/J\hspace{-1.66656pt}/\hspace{-1.111pt}\psi \pi ^+}&< 3.8\times 10^{-5}\ \text { and }\\ \mathcal{R}_{B_{s}^{*0}(\mu ^+\mu ^-)\pi ^+/J\hspace{-1.66656pt}/\hspace{-1.111pt}\psi \pi ^+}&< 5.0\times 10^{-5}. \end{aligned}$$ $\begin{array}{cc}R_{B_{}^{\ast 0}\left({\mu }^{+}{\mu }^{-}\right){\pi }^{+}/J/\psi {\pi }^{+}}^{}& <3.8\times {10}^{-5}\text{and}\\ R_{B_s^{\ast 0}\left({\mu }^{+}{\mu }^{-}\right){\pi }^{+}/J/\psi {\pi }^{+}}^{}& <5.0\times {10}^{-5}.\end{array}$ 

A<sc>bstract</sc> Usingppcollision data at$$ \sqrt{s} $$ $\sqrt{s}$= 13 TeV, recorded by the LHCb experiment between 2016 and 2018 and corresponding to an integrated luminosity of 5.4 fb⁻¹, the forward-backward asymmetry in thepp→Z/γ^*→μ⁺μ⁻process is measured. The measurement is carried out in ten intervals of the difference between the muon pseudorapidities, within a fiducial region covering dimuon masses between 66 and 116 GeV, muon pseudorapidities between 2.0 and 4.5 and muon transverse momenta above 20 GeV. These forward-backward asymmetries are compared with predictions, at next-to-leading order in the strong and electroweak couplings. The measured effective leptonic weak mixing angle is$$ {\sin}^2{\theta}_{\textrm{eff}}^{\ell }=0.23147\pm 0.00044\pm 0.00005\pm 0.00023, $$ ${sin}^2{\theta }_{\mathrm{eff}}^{\ell }=0.23147\pm 0.00044\pm 0.00005\pm 0.00023,$ where the first uncertainty is statistical, the second arises from systematic uncertainties associated with the asymmetry measurement, and the third arises from uncertainties in the fit model used to extract$$ {\sin}^2{\theta}_{\textrm{eff}}^{\ell } $$ ${sin}^2{\theta }_{\mathrm{eff}}^{\ell }$from the asymmetry measurement. This result is based on an arithmetic average of results using the CT18, MSHT20, and NNPDF31 parameterisations of the proton internal structure, and is consistent with previous measurements and with predictions from the global electroweak fit. 

A search for violation of the charge-parity ( $CP$) symmetry in the $D^{+}\to K^{-}{K}^{+}{\pi }^{+}$decay is presented, with proton-proton collision data corresponding to an integrated luminosity of $5.4{\mathrm{fb}}^{-1}$, 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 $D_s^{+}\to K^{-}{K}^{+}{\pi }^{+}$decay as a control channel. The $p$value for the hypothesis of $CP$conservation is 8.1%. The $CP$asymmetry observables $A_{CP|S}^{\varphi {\pi }^{+}}=(0.95\pm 0.43_{\mathrm{stat}}\pm 0.26_{\mathrm{syst}})\times {10}^{-3}$and $A_{CP|S}^{{\overline{K}}^{*0}{K}^{+}}=(-0.26\pm 0.56_{\mathrm{stat}}\pm 0.18_{\mathrm{syst}})\times {10}^{-3}$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. © 2024 CERN, for the LHCb Collaboration2024CERN 

A comprehensive study of the angular distributions in the bottom-baryon decays ${\mathrm{\Lambda }}_b^0\to {\mathrm{\Lambda }}_c^{+}{h}^{-}(h=\pi ,K)$, followed by ${\mathrm{\Lambda }}_c^{+}\to \mathrm{\Lambda }{h}^{+}$with $\mathrm{\Lambda }\to p{\pi }^{-}$or ${\mathrm{\Lambda }}_c^{+}\to p{K}_{\mathrm{S}}^0$decays, is performed using a data sample of proton-proton collisions corresponding to an integrated luminosity of $9{\mathrm{fb}}^{-1}$collected by the LHCb experiment at center-of-mass energies of 7, 8, and 13 TeV. The decay parameters and the associated charge-parity ( $CP$) asymmetries are measured, with no significant $CP$violation observed. For the first time, the ${\mathrm{\Lambda }}_b^0\to {\mathrm{\Lambda }}_c^{+}{h}^{-}$decay parameters are measured. The most precise measurements of the decay parameters $\alpha$, $\beta$, and $\gamma$are obtained for ${\mathrm{\Lambda }}_c^{+}$decays and an independent measurement of the decay parameters for the strange-baryon $\mathrm{\Lambda }$decay is provided. The results deepen our understanding of weak decay dynamics in baryon decays. © 2024 CERN, for the LHCb Collaboration2024CERN 

A<sc>bstract</sc> The decays of the χ_b1(1P), χ_b2(1P), χ_b1(2P) and χ_b2(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.