760 research outputs found

    Ion Dynamics in Single and Multi-Cation Perovskite

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    In organic-inorganic perovskites currently widely used to fabricate high-efficiency solar cells the electrical properties are to a large extent determined by the presence of mobile ions. These mobile ions are commonly held responsible for many undesirable features of perovskite solar cells, such as hysteretic behavior of electrical properties and degradation of parameters during operation. Hence, developing methods to study the properties of mobile ions and distinguish their contribution to electrical properties from the usual effects due to electronic states are essential for gaining control over the type and density of mobile ions. In this paper we show that comparison of deep levels transient spectroscopy (DLTS) measurements performed in the normal and reverse biasing/pulsing sequences provides a useful means of discriminating between the contributions of electronic traps usual for all semiconductors and the mobile ions very important in perovskites. To simplify things these experiments were performed on Schottky diodes rather than heterojunctions with organic-inorganic electron transport and hole transport layers. The results of experiments are presented and compared for single cation MAPbI(3)and multication perovskites. In both cases the main features observed in DLTS could be attributed to mobile ions

    Observation of the doubly charmed baryon decay Ξcc++→Ξc′+π+

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    The Ξcc++→Ξc′+π+ decay is observed using proton-proton collisions collected by the LHCb experiment at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.4 fb−1. The Ξcc++→Ξc′+π+ decay is reconstructed partially, where the photon from the Ξc′+→Ξc+γ decay is not reconstructed and the pK−π+ final state of the Ξc+ baryon is employed. The Ξcc++→Ξc′+π+branching fraction relative to that of the Ξcc++→Ξc+π+ decay is measured to be 1.41 ± 0.17 ± 0.10, where the first uncertainty is statistical and the second systematic. [Figure not available: see fulltext.

    Amplitude analysis of the Λb0→pK−γ decay

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    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

    Measurement of ZZ boson production cross-section in pppp collisions at s=5.02\sqrt{s} = 5.02 TeV

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    The first measurement of the ZZ boson production cross-section at centre-of-mass energy s=5.02\sqrt{s} = 5.02\,TeV in the forward region is reported, using pppp collision data collected by the LHCb experiment in year 2017, corresponding to an integrated luminosity of 100±2pb1100 \pm 2\,\rm{pb^{-1}}. The production cross-section is measured for final-state muons in the pseudorapidity range 2.020GeV/c2.0 20\,\rm{GeV/}\it{c}. The integrated cross-section is determined to be σZμ+μ=39.6±0.7(stat)±0.6(syst)±0.8(lumi) pb \sigma_{Z \rightarrow \mu^{+}\mu^{-}} = 39.6 \pm 0.7\,(\rm{stat}) \pm 0.6\,(\rm{syst}) \pm 0.8\,(\rm{lumi}) \ \rm{pb} for the di-muon invariant mass in the range 60<Mμμ<120GeV/c260<M_{\mu\mu}<120\,\rm{GeV/}\it{c^{2}}. 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. Based on a previous LHCb measurement of the ZZ boson production cross-section in ppPb collisions at sNN=5.02\sqrt{s_{NN}}=5.02 TeV, the nuclear modification factor RpPbR_{p\rm{Pb}} is measured for the first time at this energy. The measured values are 1.20.3+0.5(stat)±0.1(syst)1.2^{+0.5}_{-0.3}\,(\rm{stat}) \pm 0.1\,(\rm{syst}) in the forward region (1.53<yμ<4.031.53<y^*_{\mu}<4.03) and 3.60.9+1.6(stat)±0.2(syst)3.6^{+1.6}_{-0.9}\,(\rm{stat}) \pm 0.2\,(\rm{syst}) in the backward region (4.97<yμ<2.47-4.97<y^*_{\mu}<-2.47), where yμy^*_{\mu} represents the muon rapidity in the centre-of-mass frame.Comment: All figures and tables, along with any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2023-010.html (LHCb public pages

    Observation of the decays B(s)0Ds1(2536)K±B_{(s)}^{0}\to D_{s1}(2536)^{\mp}K^{\pm}

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    This paper reports the observation of the decays B(s)0Ds1(2536)K±B_{(s)}^{0}\to D_{s1}(2536)^{\mp}K^{\pm} using proton-proton collision data collected by the LHCb experiment, corresponding to an integrated luminosity of 9fb19\,\mathrm{fb}^{-1}. The branching fractions of these decays are measured relative to the normalisation channel B0D0K+KB^{0}\to \overline{D}^{0}K^{+}K^{-}. The Ds1(2536)D_{s1}(2536)^{-} meson is reconstructed in the D(2007)0K\overline{D}^{*}(2007)^{0}K^{-} decay channel and the products of branching fractions are measured to be B(Bs0Ds1(2536)K±)×B(Ds1(2536)D(2007)0K)=(2.49±0.11±0.12±0.25±0.06)×105,\mathcal{B}(B_{s}^{0}\to D_{s1}(2536)^{\mp}K^{\pm})\times\mathcal{B}(D_{s1}(2536)^{-}\to\overline{D}^{*}(2007)^{0}K^{-})=(2.49\pm0.11\pm0.12\pm0.25\pm0.06)\times 10^{-5}, B(B0Ds1(2536)K±)×B(Ds1(2536)D(2007)0K)=(0.510±0.021±0.036±0.050)×105.\mathcal{B}(B^{0}\to D_{s1}(2536)^{\mp}K^{\pm})\times\mathcal{B}(D_{s1}(2536)^{-}\to\overline{D}^{*}(2007)^{0}K^{-}) = (0.510\pm0.021\pm0.036\pm0.050)\times 10^{-5}. The first uncertainty is statistical, the second systematic, and the third arises from the uncertainty of the branching fraction of the B0D0K+KB^{0}\to \overline{D}^{0}K^{+}K^{-} normalisation channel. The last uncertainty in the Bs0B_{s}^{0} result is due to the limited knowledge of the fragmentation fraction ratio, fs/fdf_{s}/f_{d}. The significance for the Bs0B_{s}^{0} and B0B^{0} signals is larger than 10σ10\,\sigma. The ratio of the helicity amplitudes which governs the angular distribution of the Ds1(2536)D(2007)0KD_{s1}(2536)^{-}\to\overline{D}^{*}(2007)^{0}K^{-} decay is determined from the data. The ratio of the SS- and DD-wave amplitudes is found to be 1.11±0.15±0.061.11\pm0.15\pm 0.06 and its phase 0.70±0.09±0.040.70\pm0.09\pm 0.04 rad, 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-2023-014.html (LHCb public pages

    Observation of Two New Excited Ξb0 States Decaying to Λb0 K-π+

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    Two narrow resonant states are observed in the Λb0K-π+ mass spectrum using a data sample of proton-proton collisions at a center-of-mass energy of 13 TeV, collected by the LHCb experiment and corresponding to an integrated luminosity of 6 fb-1. The minimal quark content of the Λb0K-π+ system indicates that these are excited Ξb0 baryons. The masses of the Ξb(6327)0 and Ξb(6333)0 states are m[Ξb(6327)0]=6327.28-0.21+0.23±0.12±0.24 and m[Ξb(6333)0]=6332.69-0.18+0.17±0.03±0.22 MeV, respectively, with a mass splitting of Δm=5.41-0.27+0.26±0.12 MeV, where the uncertainties are statistical, systematic, and due to the Λb0 mass measurement. The measured natural widths of these states are consistent with zero, with upper limits of Γ[Ξb(6327)0]&lt;2.20(2.56) and Γ[Ξb(6333)0]&lt;1.60(1.92) MeV at a 90% (95%) credibility level. The significance of the two-peak hypothesis is larger than nine (five) Gaussian standard deviations compared to the no-peak (one-peak) hypothesis. The masses, widths, and resonant structure of the new states are in good agreement with the expectations for a doublet of 1D Ξb0 resonances

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

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    The production of η\eta and η\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 η\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 η\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 η\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

    Study of charmonium and charmonium-like contributions in B+ → J/ψηK+ decays

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    A study of B+→ J/ψηK+ decays, followed by J/ψ → μ+μ− and η → γγ, is performed using a dataset collected with the LHCb detector in proton-proton collisions at centre-of-mass energies of 7, 8 and 13 TeV, corresponding to an integrated luminosity of 9 fb−1. The J/ψη mass spectrum is investigated for contributions from charmonia and charmonium-like states. Evidence is found for the B+→ (ψ2(3823) → J/ψη)K+ and B+→ (ψ(4040) → J/ψη)K+ decays with significance of 3.4 and 4.7 standard deviations, respectively. This constitutes the first evidence for the ψ2(3823) → J/ψη decay

    Observation and branching fraction measurement of the decay Ξb- → Λ0 bπ -

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    Measurement of antiproton production from antihyperon decays in pHe collisions at √sNN=110GeV

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    The interpretation of cosmic antiproton flux measurements from space-borne experiments is currently limited by the knowledge of the antiproton production cross-section in collisions between primary cosmic rays and the interstellar medium. Using collisions of protons with an energy of 6.5 TeV incident on helium nuclei at rest in the proximity of the interaction region of the LHCb experiment, the ratio of antiprotons originating from antihyperon decays to prompt production is measured for antiproton momenta between 12 and 110GeV\!/c . The dominant antihyperon contribution, namely Λ¯ → p¯ π+ decays from promptly produced Λ¯ particles, is also exclusively measured. The results complement the measurement of prompt antiproton production obtained from the same data sample. At the energy scale of this measurement, the antihyperon contributions to antiproton production are observed to be significantly larger than predictions of commonly used hadronic production models
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