401 research outputs found

    Studies of η\eta and ηâ€Č\eta' production in pppp and ppPb collisions

    Full text link
    The production of η\eta and ηâ€Č\eta' mesons is studied in proton-proton and proton-lead collisions collected with the LHCb detector. Proton-proton collisions are studied at center-of-mass energies of 5.025.02 and 13 TeV13~{\rm TeV}, and proton-lead collisions are studied at a center-of-mass energy per nucleon of 8.16 TeV8.16~{\rm TeV}. The studies are performed in center-of-mass rapidity regions 2.5<yc.m.<3.52.5<y_{\rm c.m.}<3.5 (forward rapidity) and −4.0<yc.m.<−3.0-4.0<y_{\rm c.m.}<-3.0 (backward rapidity) defined relative to the proton beam direction. The η\eta and ηâ€Č\eta' production cross sections are measured differentially as a function of transverse momentum for 1.5<pT<10 GeV1.5<p_{\rm T}<10~{\rm GeV} and 3<pT<10 GeV3<p_{\rm T}<10~{\rm GeV}, respectively. The differential cross sections are used to calculate nuclear modification factors. The nuclear modification factors for η\eta and ηâ€Č\eta' mesons agree at both forward and backward rapidity, showing no significant evidence of mass dependence. The differential cross sections of η\eta mesons are also used to calculate η/π0\eta/\pi^0 cross section ratios, which show evidence of a deviation from the world average. These studies offer new constraints on mass-dependent nuclear effects in heavy-ion collisions, as well as η\eta and ηâ€Č\eta' meson fragmentation.Comment: All figures and tables, along with machine-readable versions and any supplementary material and additional information, are available at https://lhcbproject.web.cern.ch/Publications/p/LHCb-PAPER-2023-030.html (LHCb public pages

    Fraction of χc\chi_c decays in prompt J/ψJ/\psi production measured in pPb collisions at sNN=8.16\sqrt{s_{NN}}=8.16 TeV

    Get PDF
    The fraction of χc1\chi_{c1} and χc2\chi_{c2} decays in the prompt J/ψJ/\psi yield, Fχc=σχc→J/ψ/σJ/ψF_{\chi c}=\sigma_{\chi_c \to J/\psi}/\sigma_{J/\psi}, is measured by the LHCb detector in pPb collisions at sNN=8.16\sqrt{s_{NN}}=8.16 TeV. The study covers the forward (1.5<y∗<4.01.5<y^*<4.0) and backward (−5.0<y∗<−2.5-5.0<y^*<-2.5) rapidity regions, where y∗y^* is the J/ψJ/\psi rapidity in the nucleon-nucleon center-of-mass system. Forward and backward rapidity samples correspond to integrated luminosities of 13.6 ±\pm 0.3 nb−1^{-1} and 20.8 ±\pm 0.5 nb−1^{-1}, respectively. The result is presented as a function of the J/ψJ/\psi transverse momentum pT,J/ψp_{T,J/\psi} in the range 1<pT,J/ψ<20<p_{T, J/\psi}<20 GeV/cc. The FχcF_{\chi c} fraction at forward rapidity is compatible with the LHCb measurement performed in pppp collisions at s=7\sqrt{s}=7 TeV, whereas the result at backward rapidity is 2.4 σ\sigma larger than in the forward region for 1<pT,J/ψ<31<p_{T, J/\psi}<3 GeV/cc. The increase of FχcF_{\chi c} at low pT,J/ψp_{T, J/\psi} at backward rapidity is compatible with the suppression of the ψ\psi(2S) contribution to the prompt J/ψJ/\psi yield. The lack of in-medium dissociation of χc\chi_c states observed in this study sets an upper limit of 180 MeV on the free energy available in these pPb collisions to dissociate or inhibit charmonium state formation.Comment: All figures and tables, along with machine-readable versions and any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2023-028.html (LHCb public pages

    A measurement of ΔΓs\Delta \Gamma_{s}

    Full text link
    Using a dataset corresponding to 9 fb−19~\mathrm{fb}^{-1} of integrated luminosity collected with the LHCb detector between 2011 and 2018 in proton-proton collisions, the decay-time distributions of the decay modes Bs0→J/ψηâ€ČB_s^0 \rightarrow J/\psi \eta' and Bs0→J/ψπ+π−B_s^0 \rightarrow J/\psi \pi^{+} \pi^{-} are studied. The decay-width difference between the light and heavy mass eigenstates of the Bs0B_s^0 meson is measured to be ΔΓs=0.087±0.012±0.009 ps−1\Delta \Gamma_s = 0.087 \pm 0.012 \pm 0.009 \, \mathrm{ps}^{-1}, where the first uncertainty is statistical and the second systematic.Comment: All figures and tables, along with machine-readable versions and any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2023-025.htm

    Enhanced production of Λb0\Lambda_{b}^{0} baryons in high-multiplicity pppp collisions at s=13\sqrt{s} = 13 TeV

    Get PDF
    The production rate of Λb0\Lambda_{b}^{0} baryons relative to B0B^{0} mesons in pppp collisions at a center-of-mass energy s=13\sqrt{s} = 13 TeV is measured by the LHCb experiment. The ratio of Λb0\Lambda_{b}^{0} to B0B^{0} production cross-sections shows a significant dependence on both the transverse momentum and the measured charged-particle multiplicity. At low multiplicity, the ratio measured at LHCb is consistent with the value measured in e+e−e^{+}e^{-} collisions, and increases by a factor of ∌2\sim2 with increasing multiplicity. At relatively low transverse momentum, the ratio of Λb0\Lambda_{b}^{0} to B0B^{0} cross-sections is higher than what is measured in e+e−e^{+}e^{-} collisions, but converges with the e+e−e^{+}e^{-} ratio as the momentum increases. These results imply that the evolution of heavy bb quarks into final-state hadrons is influenced by the density of the hadronic environment produced in the collision. Comparisons with a statistical hadronization model and implications for the mechanisms enforcing quark confinement are discussed.Comment: All figures and tables, along with machine-readable versions and any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2023-027.html (LHCb public pages

    Amplitude analysis of the Λb0→pK−γ decay

    Get PDF
    The resonant structure of the radiative decay Λb0→pK−γ in the region of proton-kaon invariant-mass up to 2.5 GeV/c2 is studied using proton-proton collision data recorded at centre-of-mass energies of 7, 8, and 13 TeV collected with the LHCb detector, corresponding to a total integrated luminosity of 9 fb−1. Results are given in terms of fit and interference fractions between the different components contributing to this final state. Only Λ resonances decaying to pK− are found to be relevant, where the largest contributions stem from the Λ(1520), Λ(1600), Λ(1800), and Λ(1890) states

    Observation of strangeness enhancement with charmed mesons in high-multiplicity pPbp\mathrm{Pb} collisions at sNN=8.16 \sqrt {s_{\mathrm{NN}}}=8.16\,TeV

    Full text link
    The production of prompt Ds+D^+_{s} and D+D^+ mesons is measured by the LHCb experiment in proton-lead (pPbp\mathrm{Pb}) collisions in both the forward (1.5<y∗<4.01.5<y^*<4.0) and backward (−5.0<y∗<−2.5-5.0<y^*<-2.5) rapidity regions at a nucleon-nucleon center-of-mass energy of sNN=8.16 \sqrt {s_{\mathrm{NN}}}=8.16\,TeV. The nuclear modification factors of both Ds+D^+_{s} and D+D^+ mesons are determined as a function of transverse momentum, pTp_{\mathrm{T}}, and rapidity. In addition, the Ds+D^+_{s} to D+D^+ cross-section ratio is measured as a function of the charged particle multiplicity in the event. An enhanced Ds+D^+_{s} to D+D^+ production in high-multiplicity events is observed for the whole measured pTp_{\mathrm{T}} range, in particular at low pTp_{\mathrm{T}} and backward rapidity, where the significance exceeds six standard deviations. This constitutes the first observation of strangeness enhancement in charm quark hadronization in high-multiplicity pPbp\mathrm{Pb} collisions. The results are also qualitatively consistent with the presence of quark coalescence as an additional charm quark hadronization mechanism in high-multiplicity proton-lead collisions.Comment: All figures and tables, along with machine-readable versions and any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2023-021.html (LHCb public pages

    Search for CP\textit{CP} violation in the phase space of D0→KS0K±π∓D^{0} \rightarrow K_{S}^{0} K^{\pm} \pi^{\mp} decays with the energy test

    Get PDF
    A search for CP\textit{CP} violation in D0→KS0K+π−D^{0} \rightarrow K_{S}^{0} K^{+} \pi^{-} and D0→KS0K−π+D^{0} \rightarrow K_{S}^{0} K^{-} \pi^{+} decays is reported. The search is performed using an unbinned model-independent method known as the energy test that probes local CP\textit{CP} violation in the phase space of the decays. The data analysed correspond to an integrated luminosity of 5.4 5.4~fb−1^{-1} collected in proton-proton collisions by the LHCb experiment at a centre-of-mass energy of s=13\sqrt{s}=13~TeV, amounting to approximately 950000 and 620000 signal candidates for the D0→KS0K−π+D^{0} \rightarrow K_{S}^{0} K^{-} \pi^{+} and D0→KS0K+π−D^{0} \rightarrow K_{S}^{0} K^{+} \pi^{-} modes, respectively. The method is validated using D0→K−π+π−π+D^{0} \rightarrow K^{-} \pi^{+} \pi^{-} \pi^{+} and D0→KS0π+π−D^{0} \rightarrow K_{S}^{0} \pi^{+} \pi^{-} decays, where CP\textit{CP}-violating effects are expected to be negligible, and using background-enhanced regions of the signal decays. The results are consistent with CP\textit{CP} symmetry in both the D0→KS0K−π+D^{0} \rightarrow K_{S}^{0} K^{-} \pi^{+} and the D0→KS0K+π−D^{0} \rightarrow K_{S}^{0} K^{+} \pi^{-} decays, with pp-values for the hypothesis of no CP\textit{CP} violation of 70% and 66%, respectively.Comment: All figures and tables, along with any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2023-019.html (LHCb public pages

    Measurement of associated J/ψJ/\psi-ψ(2S)\psi(2S) production cross-section in pppp collisions at s=13\sqrt{s}=13 TeV

    Full text link
    The cross-section of associated J/ψJ/\psi-ψ(2S)\psi(2S) production in proton-proton collisions at a centre-of-mass energy of s=13\sqrt{s}=13 TeV is measured using a data sample corresponding to an integrated luminosity of 4.2 fb−1^{-1}, collected by the LHCb experiment. The measurement is performed for both J/ψJ/\psi and ψ(2S)\psi(2S) mesons having transverse momentum pT<14p_{\text{T}}<14 GeV/cc and rapidity 2.0<y<4.52.0<y<4.5, assuming negligible polarisation of the J/ψJ/\psi and ψ(2S)\psi(2S) mesons. The production cross-section is measured to be 4.5±0.7±0.34.5\pm0.7\pm0.3 nb, where the first uncertainty is statistical and the second systematic. The differential cross-sections are measured as functions of several kinematic variables of the J/ψJ/\psi-ψ(2S)\psi(2S) candidates. The results are combined with a measurement of J/ψJ/\psi-J/ψJ/\psi production, giving a cross-section ratio between J/ψJ/\psi-ψ(2S)\psi(2S) and J/ψJ/\psi-J/ψJ/\psi production of 0.274±0.044±0.0080.274\pm0.044\pm0.008, where the first uncertainty is statistical and the second systematic.Comment: All figures and tables, along with machine-readable versions and any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2023-023.html (LHCb public pages

    Observation of Cabibbo-suppressed two-body hadronic decays and precision mass measurement of the Ωc0\Omega_{c}^{0} baryon

    Get PDF
    The first observation of the singly Cabibbo-suppressed Ωc0→Ω−K+\Omega_{c}^{0}\to\Omega^{-}K^{+} and Ωc0→Ξ−π+\Omega_{c}^{0}\to\Xi^{-}\pi^{+} decays is reported, using proton-proton collision data at a centre-of-mass energy of 13 TeV13\,{\rm TeV}, corresponding to an integrated luminosity of 5.4 fb−15.4\,{\rm fb}^{-1}, collected with the LHCb detector between 2016 and 2018. The branching fraction ratios are measured to be B(Ωc0→Ω−K+)B(Ωc0→Ω−π+)=0.0608±0.0051(stat)±0.0040(syst)\frac{\mathcal{B}(\Omega_{c}^{0}\to\Omega^{-}K^{+})}{\mathcal{B}(\Omega_{c}^{0}\to\Omega^{-}\pi^{+})}=0.0608\pm0.0051({\rm stat})\pm 0.0040({\rm syst}), B(Ωc0→Ξ−π+)B(Ωc0→Ω−π+)=0.1581±0.0087(stat)±0.0043(syst)±0.0016(ext)\frac{\mathcal{B}(\Omega_{c}^{0}\to\Xi^{-}\pi^{+})}{\mathcal{B}(\Omega_{c}^{0}\to\Omega^{-}\pi^{+})}=0.1581\pm0.0087({\rm stat})\pm0.0043({\rm syst})\pm0.0016({\rm ext}). In addition, using the Ωc0→Ω−π+\Omega_{c}^{0}\to\Omega^{-}\pi^{+} decay channel, the Ωc0\Omega_{c}^{0} baryon mass is measured to be M(Ωc0)=2695.28±0.07(stat)±0.27(syst)±0.30(ext) MeV/c2M(\Omega_{c}^{0})=2695.28\pm0.07({\rm stat})\pm0.27({\rm syst})\pm0.30({\rm ext})\,{\rm MeV}/c^{2}, improving the precision of the previous world average by a factor of four.Comment: All figures and tables, along with any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2023-011.html (LHCb public pages
    • 

    corecore