The first measurement of phi(1020) meson production in fixed-target pNe collisions at root s(NN) = 68.5 GeV is presented. The phi(1020) mesons are reconstructed in their K+K- decay in a data sample consisting of proton collisions on neon nuclei at rest, corresponding to an integrated luminosity of 21.7 +/- 1.4 nb(-1), collected by the LHCb detector at CERN. The phi;(1020) production cross-section in the centre-of-mass rapidity range of -1.8 < y* < 0 and transverse momentum range of 800 < p(T) < 6500MeV/ c is found to be sigma = 182.7 +/- 2.7 (stat.) +/- 14.1 (syst) mu b/nucleon. A double-differential measurement of the cross-section is also provided in four regions of rapidity and six regions of transverse momentum of the phi(1020) meson and compared with the predictions from Pythia and EPOS4, which are found to underestimate the experimental values.

A bstract Measurements of CP observables and the CKM angle γ are performed in B ± → DK * (892) ± decays, where D represents a superposition of D 0 and $$ {\overline{D}}^0 $$ 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 final states K ± π ∓ , K + K − and π + π − ; four-body final states K ± π ∓ π ± π ∓ and π + π − π + π − ; and three-body final states $$ {K}_{\textrm{S}}^0{\pi}^{+}{\pi}^{-} $$ K S 0 π + π − and $$ {K}_{\textrm{S}}^0{K}^{+}{K}^{-} $$ K S 0 K + K − . This analysis includes the first observation of the suppressed B ± → [ π ± K ∓ ] D K * ± and B ± → [ π ± K ∓ π ± π ∓ ] D K * ± decays. The combined result gives γ = (63 ± 13) ° .

The branching fraction ratios of B[over ¯]^{0}→D^{+}τ^{-}ν[over ¯]_{τ} and B[over ¯]^{0}→D^{*+}τ^{-}ν[over ¯]_{τ} decays are measured with respect to their muonic counterparts, using a data sample corresponding to an integrated luminosity of 2.0  fb^{-1} collected by the LHCb experiment in proton-proton collisions at sqrt[s]=13  TeV. The reconstructed final states are formed by combining D^{+} mesons with τ^{-}→μ^{-}ν[over ¯]_{μ}ν_{τ} candidates, where the D^{+} is reconstructed via the D^{+}→K^{-}π^{+}π^{+} decay. The results are R(D^{+})=0.249±0.043±0.047, R(D^{*+})=0.402±0.081±0.085, where the first uncertainties are statistical and the second systematic. The two measurements have a correlation coefficient of -0.39 and are compatible with the standard model.

Abstract The first full amplitude analysis of B + → ψ(2S)K + π + π − decays is performed using proton-proton collision data corresponding to an integrated luminosity of 9 fb−1 recorded with the LHCb detector. The rich K + π + π − spectrum is studied and the branching fractions of the resonant substructure associated with the prominent K 1(1270)+ contribution are measured. The data cannot be described by conventional strange and charmonium resonances only. An amplitude model with 53 components is developed comprising 11 hidden-charm exotic hadrons. New production mechanisms for charged charmonium-like states are observed. Significant resonant activity with spin-parity J P = 1+ in the ψ(2S)π + system is confirmed and a multi-pole structure is demonstrated. The spectral decomposition of the ψ(2S)π + π − invariant-mass structure, dominated by X 0 → ψ(2S)ρ(770)0 decays, broadly resembles the J/ψϕ spectrum observed in B + → J/ψϕK + decays. Exotic ψ(2S)K + π − resonances are observed for the first time.

Abstract A time-dependent, flavour-tagged measurement of CP violation is performed with B 0 → D + D − and B s 0 $$ {B}_s^0 $$ → D s + D s − $$ {D}_s^{+}{D}_s^{-} $$ decays, using data collected by the LHCb detector in proton-proton collisions at a centre-of-mass energy of 13 TeV corresponding to an integrated luminosity of 6 fb −1. In B 0 → D + D − decays the CP-violation parameters are measured to be S D + D − = − 0.552 ± 0.100 stat ± 0.010 syst , C D + D − = 0.128 ± 0.103 stat ± 0.010 syst . $$ {\displaystyle \begin{array}{c}{S}_{D^{+}{D}^{-}}=-0.552\pm 0.100\left(\textrm{stat}\right)\pm 0.010\left(\textrm{syst}\right),\\ {}{C}_{D^{+}{D}^{-}}=0.128\pm 0.103\left(\textrm{stat}\right)\pm 0.010\left(\textrm{syst}\right).\end{array}} $$ In B s 0 $$ {B}_s^0 $$ → D s + D s − $$ {D}_s^{+}{D}_s^{-} $$ decays the CP-violating parameter formulation in terms of ϕ s and |λ| results in ϕ s = − 0.086 ± 0.106 stat ± 0.028 syst rad , ∣ λ D s + D s − ∣ = 1.145 ± 0.126 stat ± 0.031 syst . $$ {\displaystyle \begin{array}{c}{\phi}_s=-0.086\pm 0.106\left(\textrm{stat}\right)\pm 0.028\left(\textrm{syst}\right)\textrm{rad},\\ {}\mid {\lambda}_{D_s^{+}{D}_s^{-}}\mid =1.145\pm 0.126\left(\textrm{stat}\right)\pm 0.031\left(\textrm{syst}\right).\end{array}} $$ These results represent the most precise single measurement of the CP-violation parameters in their respective channels. For the first time in a single measurement, CP symmetry is observed to be violated in B 0 → D + D − decays with a significance exceeding six standard deviations.

Measurements are presented of the cross-section for the central exclusive production of J/psi -> mu(+) mu(-) and psi(2S) -> mu(+)mu(-) processes in proton-proton collisions at root s = 13 TeV with 2016-2018 data. They are performed by requiring both muons to be in the LHCb acceptance (with pseudorapidity 2 < eta(mu +/-) < 4.5) and mesons in the rapidity range 2.0 < y < 4.5. The integrated cross-section results are sigma(J/psi ->mu+ mu-) (2.0 < y(J/psi) < 4.5, 2.0 < eta(mu +/-) < 4.5) = 400 +/- 2 +/- 5 +/- 12 pb, sigma(psi(2S)->mu+mu-)(2.0 < y(psi(2S)) < 4.5, 2.0 < eta(mu +/-) < 4.5) = 9.40 +/- 0.15 +/- 0.13 +/- 0.27 pb, where the uncertainties are statistical, systematic and due to the luminosity determination. In addition, a measurement of the ratio of psi(2S) and J/psi cross-sections, at an average photon-proton centre-of-mass energy of 1 TeV, is performed, giving sigma(psi(2S))/sigma(J/psi) = 0.1763 +/- 0.0029 +/- 0.0008 +/- 0.0039, where the first uncertainty is statistical, the second systematic and the third due to the knowledge of the involved branching fractions. For the first time, the dependence of the J/psi and psi(2S) cross-sections on the total transverse momentum transfer is determined in pp collisions and is found consistent with the behaviour observed in electron-proton collisions.

An amplitude analysis of B^{-}→D^{-}D^{0}K_{S}^{0} decays is performed using proton-proton collision data, corresponding to an integrated luminosity of 9  fb^{-1}, collected with the LHCb detector at center-of-mass energies of 7, 8, and 13 TeV. A resonant structure of spin-parity 0^{+} is observed in the D^{0}K_{S}^{0} invariant-mass spectrum with a significance of 5.3σ. The mass and width of the state, modeled with a Breit-Wigner line shape, are determined to be 2883±11±8  MeV/c^{2} and 87_{-47}^{+22}±17  MeV, respectively, where the first uncertainties are statistical and the second systematic. These properties and the quark content are consistent with those of the open-charm tetraquark candidate T_{cs0}^{*}(2870)^{0} observed previously in the D^{+}K^{-} final state of the B^{-}→D^{-}D^{+}K^{-} decay. This result confirms the existence of the T_{cs0}^{*}(2870)^{0} state in a new decay mode. The T_{cs1}^{*}(2900)^{0} state, reported in the B^{-}→D^{-}D^{+}K^{-} decay, is also searched for in the D^{0}K_{S}^{0} invariant-mass spectrum of the B^{-}→D^{-}D^{0}K_{S}^{0} decay, without finding evidence for it.

An angular analysis of the B_s^0 → ϕe+e− decay is performed using the proton-proton collision dataset collected between 2011 and 2018 by the LHCb experiment, corresponding to an integrated luminosity of 9 fb−1 at centre-of-mass energies of 7, 8 and 13 TeV. The analysis is performed in the very low dielectron invariant mass-squared region between 0.0009 and 0.2615 GeV2/c4. The longitudinal polarisation fraction of the ϕ meson is measured to be less than 11.5 A_T^ℛ eCP observable, which is related to the lepton forward-backward asymmetry, is measured to be 0.116 ± 0.155 ± 0.006, where the first uncertainty is statistical and the second systematic. The transverse asymmetries, A_T^(2) and A_T^ℐ mCP , which are sensitive to the virtual photon polarisation, are found to be −0.045 ± 0.235 ± 0.014 and 0.002 ± 0.247 ± 0.016, respectively. The results are consistent with Standard Model predictions.

This paper presents the first measurement of $$\psi {(2S)}$$ ψ ( 2 S ) and $$\chi _{c1}(3872)$$ χ c 1 ( 3872 ) 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 / ψ ( $$\rightarrow $$ → $$\mu ^+\mu ^-$$ μ + μ - ) $$\pi ^+\pi ^-$$ 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 $$13\text {TeV} $$ 13 TeV in 2016, corresponding to an integrated luminosity of $$1.64\,\text {\,fb} ^{-1} $$ 1.64 \,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 T ( tag ) / p T ( jet ) ), is measured differentially in $$p_{\textrm{T}} (\text {jet})$$ p T ( jet ) and $$p_{\textrm{T}} (\text {tag})$$ p T ( tag ) bins. The distributions are separated into promptly produced quarkonia from proton-proton 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 shower.

A time-dependent, flavour-tagged measurement of CP violation is performed with B0 → D+D− and B_s^0 → D_s^+D_s^- decays, using data collected by the LHCb detector in proton-proton collisions at a centre-of-mass energy of 13 TeV corresponding to an integrated luminosity of 6 fb−1. In B0 → D+D− decays the CP-violation parameters are measured to be [ S_D^+D^-=-0.552± 0.100(stat)± 0.010(syst),; C_D^+D^-=0.128± 0.103(stat)± 0.010(syst). ] In B_s^0 → D_s^+D_s^- decays the CP-violating parameter formulation in terms of ϕs and |λ| results in [ ϕ_s=-0.086± 0.106(stat)± 0.028(syst)rad,; |λ_D_s^+D_s^-| =1.145± 0.126(stat)± 0.031(syst). ] These results represent the most precise single measurement of the CP-violation parameters in their respective channels. For the first time in a single measurement, CP symmetry is observed to be violated in B0 → D+D− decays with a significance exceeding six standard deviations.

A search for hidden-charm pentaquark states decaying to a range of ΣcD¯ and Λc+D¯ final states, as well as doubly charmed pentaquark states to ΣcD and Λc+D, is made using samples of proton-proton collision data corresponding to an integrated luminosity of 5.7 fb−1 recorded by the LHCb detector at s=13 TeV. Since no significant signals are found, upper limits are set on the pentaquark yields relative to that of the Λc+ baryon in the Λc+→pK−π+ decay mode. The known pentaquark states are also investigated, and their signal yields are found to be consistent with zero in all cases. © 2024 CERN, for the LHCb Collaboration 2024 CERN

For accurate determination of particle masses accurate knowledge of the momentum scale of the detectors is crucial. The procedure used to calibrate the momentum scale of the LHCb spectrometer is described and illustrated using the performance obtained with an integrated luminosity of $1.6~ fb^{-1}$ collected during 2016 in $pp$ running. The procedure uses large samples of $J/\psi \rightarrow \mu^+ \mu^-$ and $B^+ \rightarrow J/\psi K^+$ decays and leads to a relative accuracy of $3 \times 10^{-4}$ on the momentum scale.

A comprehensive study of the angular distributions in the bottom-baryon decays Λ^0_b→Λ_c^+ h^-(h=π, K), followed by Λ_c^+→Λ h^+ with Λ→pπ^- or Λ_c^+→pK^0_S decays, is performed using a data sample of proton-proton collisions corresponding to an integrated luminosity of 9 fb^-1 collected by the LHCb experiment at center-of-mass energies of 7, 8 and 13 Te -0.1em V. The decay parameters and the associated charge-parity (CP) asymmetries are measured, with no significant CP violation observed. For the first time, the Λ^0_b →Λ_c^+ h^- decay parameters are measured. The most precise measurements of the decay parameters α, β and γ are obtained for Λ_c^+ decays and an independent measurement of the decay parameters for the strange-baryon Λ decay is provided. The results deepen our understanding of weak decay dynamics in baryon decays.

Abstract The Λ b 0 $$ {\Lambda}_b^0 $$ → D + D − Λ decay is observed for the first time using proton-proton collision data collected by the LHCb experiment at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.3 fb −1. Using the B 0 → D + D − K S 0 $$ {D}^{+}{D}^{-}{K}_S^0 $$ decay as a reference channel, the product of the relative production cross-section and decay branching fractions is measured to be R = σ Λ b 0 σ B 0 = B Λ b 0 → D + D − Λ B B 0 → D + D − K S 0 = 0.179 ± 0.022 ± 0.014 , $$ \mathcal{R}=\frac{\sigma_{\Lambda_b^0}}{\sigma_{B^0}}=\frac{\mathcal{B}\left({\Lambda}_b^0\to {D}^{+}{D}^{-}\Lambda \right)}{\mathcal{B}\left({B}^0\to {D}^{+}{D}^{-}{K}_{\textrm{S}}^0\right)}=0.179\pm 0.022\pm 0.014, $$ where the first uncertainty is statistical and the second is systematic. The known branching fraction of the reference channel, B B 0 → D + D − K S 0 $$ \mathcal{B}\left({B}^0\to {D}^{+}{D}^{-}{K}_{\textrm{S}}^0\right) $$ , and the cross-section ratio, σ Λ b 0 / σ B 0 $$ {\sigma}_{\Lambda_b^0}/{\sigma}_{B^0} $$ , previously measured by LHCb are used to derive the branching fraction of the Λ b 0 $$ {\Lambda}_b^0 $$ → D + D − Λ decay B Λ b 0 → D + D − Λ = 1.24 ± 0.15 ± 0.10 ± 0.28 ± 0.11 × 10 − 4 , $$ \mathcal{B}\left({\Lambda}_b^0\to {D}^{+}{D}^{-}\Lambda \right)=\left(1.24\pm 0.15\pm 0.10\pm 0.28\pm 0.11\right)\times {10}^{-4}, $$ where the third and fourth contributions are due to uncertainties of B B 0 → D + D − K S 0 $$ \mathcal{B}\left({B}^0\to {D}^{+}{D}^{-}{K}_{\textrm{S}}^0\right) $$ and σ Λ b 0 / σ B 0 $$ {\sigma}_{\Lambda_b^0}/{\sigma}_{B^0} $$ , respectively. Inspection of the D +Λ and D + D − invariant-mass distributions suggests a rich presence of intermediate resonances in the decay. The Λ b 0 $$ {\Lambda}_b^0 $$ → D *+ D − Λ decay is also observed for the first time as a partially reconstructed component in the D + D − Λ invariant mass spectrum.

The first measurement of the Z boson production cross-section at centre-of-mass energy v s = 5.02TeV in the forward region is reported, using pp collision data collected by the LHCb experiment in year 2017, corresponding to an integrated luminosity of 100 +/- 2 pb-1. The production cross-section is measured for final-state muons in the pseudorapidity range 2.0 <. < 4.5 with transverse momentum pT > 20 GeV/c. The integrated cross-section is determined to be sZ.mu+mu- = 39.6 +/- 0.7(stat) +/- 0.6(syst) +/- 0.8(lumi) pb for the di-muon invariant mass in the range 60 < M mu mu < 120 GeV/c2. This result and the differential cross-section results are in good agreement with theoretical predictions at next-to-next-to-leading order in the strong coupling constant. Based on a previous LHCb measurement of the Z boson production cross-section in pPb collisions at v sNN = 5.02TeV, the nuclear modification factor RpPb is measured for the first time at this energy. The measured values are 1.2+0.5 -0.3(stat) +/- 0.1(syst) in the forward region (1.53 < y* mu < 4.03) and 3.6+1.6 -0.9(stat)+/- 0.2(syst) in the backward region (-4.97 < y* mu < -2.47), where y* mu represents the muon rapidity in the centre-of-mass frame.

Abstract A measurement of CP-violating observables associated with the interference of B0→ D0K⋆(892)0 and $$ {B}^0\to {\overline{D}}^0{K}^{\star }{(892)}^0 $$ B 0 → D ¯ 0 K ⋆ 892 0 decay amplitudes is performed in the D0→ K∓π±(π+π−), D0→ π+π−(π+π−), and D0→ K+K− final states using data collected by the LHCb experiment corresponding to an integrated luminosity of 9 fb−1. CP-violating observables related to the interference of $$ {B}_s^0\to {D}^0{\overline{K}}^{\star }{(892)}^0 $$ B s 0 → D 0 K ¯ ⋆ 892 0 and $$ {B}_s^0\to {\overline{D}}^0{\overline{K}}^{\star }{(892)}^0 $$ B s 0 → D ¯ 0 K ¯ ⋆ 892 0 are also measured, but no evidence for interference is found. The B0 observables are used to constrain the parameter space of the CKM angle γ and the hadronic parameters $$ {r}_{B^0}^{DK\star } $$ r B 0 DK ⋆ and $$ {\delta}_{B^0}^{DK\star } $$ δ B 0 DK ⋆ with inputs from other measurements. In a combined analysis, these measurements allow for four solutions in the parameter space, only one of which is consistent with the world average.

A study of resonant structures in B^{+}→D^{*+}D^{-}K^{+} and B^{+}→D^{*-}D^{+}K^{+} decays is performed, using proton-proton collision data at center-of-mass energies of sqrt[s]=7, 8, and 13 TeV recorded by the LHCb experiment, corresponding to an integrated luminosity of 9  fb^{-1}. A simultaneous amplitude fit is performed to the two channels with contributions from resonances decaying to D^{*-}D^{+} and D^{*+}D^{-} states linked by C parity. This procedure allows the C parities of resonances in the D^{*±}D^{∓} mass spectra to be determined. Four charmonium or charmoniumlike states are observed decaying into D^{*±}D^{∓}: η_{c}(3945), h_{c}(4000), χ_{c1}(4010), and h_{c}(4300), with quantum numbers J^{PC} equal to 0^{-+}, 1^{+-}, 1^{++}, and 1^{+-}, respectively. At least three of these states have not been observed previously. In addition, the existence of the T_{c[over ¯]s[over ¯]0}^{*}(2870)^{0} and T_{c[over ¯]s[over ¯]1}^{*}(2900)^{0} resonances in the D^{-}K^{+} mass spectrum, already observed in the B^{+}→D^{+}D^{-}K^{+} decay, is confirmed in a different production channel.

A study of prompt Xi(+)(c) production in proton-lead collisions is performed with the LHCb experiment at a centerof-mass energy per nucleon pair of 8.16 TeV in 2016 in pPb and Pbp collisions with an estimated integrated luminosity of approximately 12.5 and 17.4 nb(-1), respectively. The Xi(+)(c) roduction cross section, as well as the Xi(+)(c) to Lambda(+)(c) production cross-section ratio, are measured as a function of the transverse momentum and rapidity and compared to the latest theory predictions. The forward-backward asymmetry is also measured as a function of the Xi(+)(c) ransverse momentum. The results provide strong constraints on theoretical calculation and are a unique input for hadronization studies in different collision systems.

A comprehensive study of the angular distributions in the bottom-baryon decays Λ_{b}^{0}→Λ_{c}^{+}h^{-}(h=π,K), followed by Λ_{c}^{+}→Λh^{+} with Λ→pπ^{-} or Λ_{c}^{+}→pK_{S}^{0} decays, is performed using a data sample of proton-proton collisions corresponding to an integrated luminosity of 9  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 Λ_{b}^{0}→Λ_{c}^{+}h^{-} decay parameters are measured. The most precise measurements of the decay parameters α, β, and γ are obtained for Λ_{c}^{+} decays and an independent measurement of the decay parameters for the strange-baryon Λ decay is provided. The results deepen our understanding of weak decay dynamics in baryon decays.

A bstract A search for the fully reconstructed $$ {B}_s^0 $$ B s 0 → μ + μ − γ decay is performed at the LHCb experiment using proton-proton collisions at $$ \sqrt{s} $$ s = 13 TeV corresponding to an integrated luminosity of 5 . 4 fb − 1 . No significant signal is found and upper limits on the branching fraction in intervals of the dimuon mass are set $$ {\displaystyle \begin{array}{cc}\mathcal{B}\left({B}_s^0\to {\mu}^{+}{\mu}^{-}\gamma \right)<4.2\times {10}^{-8},& m\left({\mu}^{+}{\mu}^{-}\right)\in \left[2{m}_{\mu },1.70\right]\textrm{GeV}/{c}^2,\\ {}\mathcal{B}\left({B}_s^0\to {\mu}^{+}{\mu}^{-}\gamma \right)<7.7\times {10}^{-8},&\ m\left({\mu}^{+}{\mu}^{-}\right)\in \left[\textrm{1.70,2.88}\right]\textrm{GeV}/{c}^2,\\ {}\mathcal{B}\left({B}_s^0\to {\mu}^{+}{\mu}^{-}\gamma \right)<4.2\times {10}^{-8},& m\left({\mu}^{+}{\mu}^{-}\right)\in \left[3.92,{m}_{B_s^0}\right]\textrm{GeV}/{c}^2,\end{array}} $$ B B s 0 → μ + μ − γ < 4.2 × 10 − 8 , m μ + μ − ∈ 2 m μ 1.70 GeV / c 2 , B B s 0 → μ + μ − γ < 7.7 × 10 − 8 , m μ + μ − ∈ 1.70, 2.88 GeV / c 2 , B B s 0 → μ + μ − γ < 4.2 × 10 − 8 , m μ + μ − ∈ 3.92 m B s 0 GeV / c 2 , at 95% confidence level. Additionally, upper limits are set on the branching fraction in the [2 m μ , 1 . 70] GeV /c 2 dimuon mass region excluding the contribution from the intermediate ϕ (1020) meson, and in the region combining all dimuon-mass intervals.