Publications
1178 results found
Aaij R, Abdelmotteleb ASW, Abellan Beteta C, et al., 2024, Measurement of Ξc+ production in pPb collisions at sNN =8.16 TeV at LHCb, Physical Review C, Vol: 109, ISSN: 2469-9985
A study of prompt Ξc+ production in proton-lead collisions is performed with the LHCb experiment at a center-of-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 Ξc+ production cross section, as well as the Ξc+ to Λc+ 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 Ξc+ transverse momentum. The results provide strong constraints on theoretical calculation and are a unique input for hadronization studies in different collision systems.
Aaij R, Abdelmotteleb ASW, Abellan Beteta C, et al., 2024, Amplitude Analysis of the B^{0}→K^{*0}μ^{+}μ^{-} Decay., Phys Rev Lett, Vol: 132
An amplitude analysis of the B^{0}→K^{*0}μ^{+}μ^{-} decay is presented using a dataset corresponding to an integrated luminosity of 4.7 fb^{-1} of pp collision data collected with the LHCb experiment. For the first time, the coefficients associated to short-distance physics effects, sensitive to processes beyond the standard model, are extracted directly from the data through a q^{2}-unbinned amplitude analysis, where q^{2} is the μ^{+}μ^{-} invariant mass squared. Long-distance contributions, which originate from nonfactorizable QCD processes, are systematically investigated, and the most accurate assessment to date of their impact on the physical observables is obtained. The pattern of measured corrections to the short-distance couplings is found to be consistent with previous analyses of b- to s-quark transitions, with the largest discrepancy from the standard model predictions found to be at the level of 1.8 standard deviations. The global significance of the observed differences in the decay is 1.4 standard deviations.
Aaij R, Abdelmotteleb ASW, Abellan Beteta C, et al., 2024, Search for CP violation in the phase space of $$ {D}^0\to {K}_S^0{K}^{\pm }{\pi}^{\mp } $$ decays with the energy test, Journal of High Energy Physics, Vol: 2024
<jats:title>A<jats:sc>bstract</jats:sc> </jats:title><jats:p>A search for <jats:italic>CP</jats:italic> violation in <jats:inline-formula><jats:alternatives><jats:tex-math>$$ {D}^0\to {K}_S^0{K}^{+}{\pi}^{-} $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mi>D</mml:mi> <mml:mn>0</mml:mn> </mml:msup> <mml:mo>→</mml:mo> <mml:msubsup> <mml:mi>K</mml:mi> <mml:mi>S</mml:mi> <mml:mn>0</mml:mn> </mml:msubsup> <mml:msup> <mml:mi>K</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:msup> <mml:mi>π</mml:mi> <mml:mo>−</mml:mo> </mml:msup> </mml:math></jats:alternatives></jats:inline-formula> and <jats:inline-formula><jats:alternatives><jats:tex-math>$$ {D}^0\to {K}_S^0{K}^{-}{\pi}^{+} $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mi>D</mml:mi> <mml:mn>0</mml:mn> </mml:msup> <mml:mo>→</mml:mo> <mml:msubsup> <mml:mi>K</mml:mi> <mml:mi>S</mml:mi> <mml:mn>0</mml:mn> </mml:msubsup> <mml:msup> <mml:mi>K</mm
Aaij R, Abdelmotteleb ASW, Abellan Beteta C, et al., 2024, Measurement of J/ψ-pair production in pp collisions at $$ \sqrt{s} $$ = 13 TeV and study of gluon transverse-momentum dependent PDFs, Journal of High Energy Physics, Vol: 2024
<jats:title>A<jats:sc>bstract</jats:sc> </jats:title><jats:p>The production cross-section of <jats:italic>J/ψ</jats:italic> pairs in proton-proton collisions at a centre-of-mass energy of <jats:inline-formula><jats:alternatives><jats:tex-math>$$ \sqrt{s} $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msqrt> <mml:mi>s</mml:mi> </mml:msqrt> </mml:math></jats:alternatives></jats:inline-formula> = 13 TeV is measured using a data sample corresponding to an integrated luminosity of 4<jats:italic>.</jats:italic>2 fb<jats:sup><jats:italic>−</jats:italic>1</jats:sup> collected by the LHCb experiment. The measurement is performed with both <jats:italic>J/ψ</jats:italic> mesons in the transverse momentum range 0 <jats:italic>< p</jats:italic><jats:sub>T</jats:sub><jats:italic><</jats:italic> 14 GeV/<jats:italic>c</jats:italic> and rapidity range 2<jats:italic>.</jats:italic>0 <jats:italic>< y <</jats:italic> 4<jats:italic>.</jats:italic>5. The cross-section of this process is measured to be 16<jats:italic>.</jats:italic>36 ± 0<jats:italic>.</jats:italic>28 (stat) ± 0<jats:italic>.</jats:italic>88 (syst) nb. The contributions from single-parton scattering and double-parton scattering are separated based on the dependence of the cross-section on the absolute rapidity difference ∆<jats:italic>y</jats:italic> between the two <jats:italic>J/ψ</jats:italic> mesons. The effective cross-section of double-parton scattering is measured to be <jats:italic>σ</jats:italic><jats:su
Aaij R, Abdelmotteleb ASW, Abellan Beteta C, et al., 2024, Fraction of χ_{c} Decays in Prompt J/ψ Production Measured in pPb Collisions at sqrt[s_{NN}]=8.16 TeV., Phys Rev Lett, Vol: 132
The fraction of χ_{c1} and χ_{c2} decays in the prompt J/ψ yield, F_{χ_{c}→J/ψ}=σ_{χ_{c}→J/ψ}/σ_{J/ψ}, is measured by the LHCb detector in pPb collisions at sqrt[s_{NN}]=8.16 TeV. The study covers the forward (1.5<y^{*}<4.0) and backward (-5.0<y^{*}<-2.5) rapidity regions, where y^{*} is the J/ψ rapidity in the nucleon-nucleon center-of-mass system. Forward and backward rapidity samples correspond to integrated luminosities of 13.6±0.3 and 20.8±0.5 nb^{-1}, respectively. The result is presented as a function of the J/ψ transverse momentum p_{T,J/ψ} in the range 1<p_{T,J/ψ}<20 GeV/c. The F_{χ_{c}→J/ψ} fraction at forward rapidity is compatible with the LHCb measurement performed in pp collisions at sqrt[s]=7 TeV, whereas the result at backward rapidity is 2.4σ larger than in the forward region for 1<p_{T,J/ψ}<3 GeV/c. The increase of F_{χ_{c}→J/ψ} at low p_{T,J/ψ} at backward rapidity is compatible with the suppression of the ψ(2S) contribution to the prompt J/ψ yield. The lack of in-medium dissociation of χ_{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.
Aaij R, Abdelmotteleb ASW, Beteta CA, et al., 2024, Observation of $${{\varXi } ^0_{b}} \rightarrow {{\varXi } ^+_{c}} {{D} ^-_{s}} $$ and $${{\varXi } ^-_{b}} \rightarrow {{\varXi } ^0_{c}} {{D} ^-_{s}} $$ decays, The European Physical Journal C, Vol: 84
<jats:title>Abstract</jats:title><jats:p>The <jats:inline-formula><jats:alternatives><jats:tex-math>$$\Xi _b^0 \rightarrow \Xi _c^+ D_s^-$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msubsup> <mml:mi>Ξ</mml:mi> <mml:mi>b</mml:mi> <mml:mn>0</mml:mn> </mml:msubsup> <mml:mo>→</mml:mo> <mml:msubsup> <mml:mi>Ξ</mml:mi> <mml:mi>c</mml:mi> <mml:mo>+</mml:mo> </mml:msubsup> <mml:msubsup> <mml:mi>D</mml:mi> <mml:mi>s</mml:mi> <mml:mo>-</mml:mo> </mml:msubsup> </mml:mrow> </mml:math></jats:alternatives></jats:inline-formula> and <jats:inline-formula><jats:alternatives><jats:tex-math>$$\Xi _b^- \rightarrow \Xi _c^0 D_s^-$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msubsup> <mml:mi>Ξ</mml:mi> <mml:mi>b</mml:mi> <mml:mo>-</mml:mo> </mml:msubsup> <mml:mo>→</mml:mo> <mml:msubsup> <mml:mi>Ξ</mml:mi> <mml:mi>c</mml:mi> <mml:mn>0</mml:mn> </mml:msubsup> <mml:msu
Aaij R, Abdelmotteleb ASW, Abellan Beteta C, et al., 2024, Determination of short- and long-distance contributions in B0 →k∗0μ+μ- decays, Physical Review D, Vol: 109, ISSN: 2470-0010
An amplitude analysis of the B0→K∗0μ+μ- decay is presented. The analysis is based on data collected by the LHCb experiment from proton-proton collisions at s=7, 8 and 13 TeV, corresponding to an integrated luminosity of 4.7 fb-1. For the first time, Wilson coefficients and nonlocal hadronic contributions are accessed directly from the unbinned data, where the latter are parametrized as a function of q2 with a polynomial expansion. Wilson coefficients and nonlocal hadronic parameters are determined under two alternative hypotheses: the first relies on experimental information alone, while the second one includes information from theoretical predictions for the nonlocal contributions. Both models obtain similar results for the parameters of interest. The overall level of compatibility with the Standard Model is evaluated to be between 1.8 and 1.9 standard deviations when looking at the C9 Wilson coefficient alone, and between 1.3 and 1.4 standard deviations when considering the full set of C9,C10,C9′ and C10′ Wilson coefficients. The ranges reflect the theoretical assumptions made in the analysis.
Aaij R, Abdelmotteleb ASW, Abellan Beteta C, et al., 2024, Curvature-bias corrections using a pseudomass method, Journal of Instrumentation, Vol: 19
Momentum measurements for very high momentum charged particles, such as muons from electroweak vector boson decays, are particularly susceptible to charge-dependent curvature biases that arise from misalignments of tracking detectors. Low momentum charged particles used in alignment procedures have limited sensitivity to coherent displacements of such detectors, and therefore are unable to fully constrain these misalignments to the precision necessary for studies of electroweak physics. Additional approaches are therefore required to understand and correct for these effects. In this paper the curvature biases present at the LHCb detector are studied using the pseudomass method in proton-proton collision data recorded at centre of mass energy √s = 13 TeV during 2016, 2017 and 2018. The biases are determined using Z → μ+μ- decays in intervals defined by the data-taking period, magnet polarity and muon direction. Correcting for these biases, which are typically at the 10-4 GeV-1 level, improves the Z → μ+μ- mass resolution by roughly 18% and eliminates several pathological trends in the kinematic-dependence of the mean dimuon invariant mass.
Aaij R, Abdelmotteleb ASW, Beteta CA, et al., 2024, Measurement of the CKM angle $$\gamma $$ in the $${{{B} ^0} \rightarrow {D} {{K} ^{*0}}}$$ channel using self-conjugate $${D} \rightarrow {{K} ^0_{\textrm{S}}} h^+ h^-$$ decays, The European Physical Journal C, Vol: 84
<jats:title>Abstract</jats:title><jats:p>A model-independent study of <jats:inline-formula><jats:alternatives><jats:tex-math>$$C\!P$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>C</mml:mi> <mml:mspace /> <mml:mi>P</mml:mi> </mml:mrow> </mml:math></jats:alternatives></jats:inline-formula> violation in <jats:inline-formula><jats:alternatives><jats:tex-math>$${{B} ^0} \rightarrow {D} {{K} ^{*0}} $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mrow> <mml:mi>B</mml:mi> </mml:mrow> <mml:mn>0</mml:mn> </mml:msup> <mml:mo>→</mml:mo> <mml:mi>D</mml:mi> <mml:msup> <mml:mrow> <mml:mi>K</mml:mi> </mml:mrow> <mml:mrow> <mml:mrow /> <mml:mo>∗</mml:mo> <mml:mn>0</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:math></jats:alternatives></jats:inline-formula> decays is presented using data corresponding to an integrated luminosity of 9<jats:inline-formula><jats:alternatives><jats:tex-math>$$\text {\,fb} ^{-1}$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML&quo
Aaij R, Abdelmotteleb ASW, Abellan Beteta C, et al., 2024, Enhanced Production of Λ_{b}^{0} Baryons in High-Multiplicity pp Collisions at sqrt[s]=13 TeV., Phys Rev Lett, Vol: 132
The production rate of Λ_{b}^{0} baryons relative to B^{0} mesons in pp collisions at a center-of-mass energy sqrt[s]=13 TeV is measured by the LHCb experiment. The ratio of Λ_{b}^{0} to B^{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^{-} collisions, and increases by a factor of ∼2 with increasing multiplicity. At relatively low transverse momentum, the ratio of Λ_{b}^{0} to B^{0} cross sections is higher than what is measured in e^{+}e^{-} collisions, but converges with the e^{+}e^{-} ratio as the momentum increases. These results imply that the evolution of heavy b quarks into final-state hadrons is influenced by the density of the hadronic environment produced in the collision. Comparisons with several models and implications for the mechanisms enforcing quark confinement are discussed.
Aaij R, Abdelmotteleb ASW, Abellan Beteta C, et al., 2024, Observation of Cabibbo-Suppressed Two-Body Hadronic Decays and Precision Mass Measurement of the Ω_{c}^{0} Baryon., Phys Rev Lett, Vol: 132
The first observation of the singly Cabibbo-suppressed Ω_{c}^{0}→Ω^{-}K^{+} and Ω_{c}^{0}→Ξ^{-}π^{+} decays is reported, using proton-proton collision data at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.4 fb^{-1}, collected with the LHCb detector between 2016 and 2018. The branching fraction ratios are measured to be B(Ω_{c}^{0}→Ω^{-}K^{+})/B(Ω_{c}^{0}→Ω^{-}π^{+})=[6.08±0.51(stat)±0.40(syst)]%,B(Ω_{c}^{0}→Ξ^{-}π^{+})/B(Ω_{c}^{0}→Ω^{-}π^{+})=[15.81±0.87(stat)±0.44(syst)±0.16(ext)]%. In addition, using the Ω_{c}^{0}→Ω^{-}π^{+} decay channel, the Ω_{c}^{0} baryon mass is measured to be M(Ω_{c}^{0})=2695.28±0.07(stat)±0.27(syst)±0.30(ext) MeV, improving the precision of the previous world average by a factor of 4.
Aaij R, Abdelmotteleb ASW, Abellan Beteta C, et al., 2024, Study of $$ {B}_c^{+}\to {\chi}_c{\pi}^{+} $$ decays, Journal of High Energy Physics, Vol: 2024
<jats:title>A<jats:sc>bstract</jats:sc> </jats:title><jats:p>A study of <jats:inline-formula><jats:alternatives><jats:tex-math>$$ {B}_c^{+}\to {\chi}_c{\pi}^{+} $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mi>B</mml:mi> <mml:mi>c</mml:mi> <mml:mo>+</mml:mo> </mml:msubsup> <mml:mo>→</mml:mo> <mml:msub> <mml:mi>χ</mml:mi> <mml:mi>c</mml:mi> </mml:msub> <mml:msup> <mml:mi>π</mml:mi> <mml:mo>+</mml:mo> </mml:msup> </mml:math></jats:alternatives></jats:inline-formula> decays is reported using proton-proton collision data, collected with the LHCb detector at centre-of-mass energies of 7, 8, and 13 TeV, corresponding to an integrated luminosity of 9 fb<jats:sup><jats:italic>−</jats:italic>1</jats:sup>. The decay <jats:inline-formula><jats:alternatives><jats:tex-math>$$ {B}_c^{+}\to {\chi}_{c2}{\pi}^{+} $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mi>B</mml:mi> <mml:mi>c</mml:mi> <mml:mo>+</mml:mo> </mml:msubsup> <mml:mo>→</mml:mo> <mml:msub> <mml:mi>χ</mml:mi> <mml:mrow> <mml:mi>c</mml:mi> <
Aaij R, Abdelmotteleb ASW, Abellan Beteta C, et al., 2024, A model-independent measurement of the CKM angle γ in partially reconstructed B± → D*h± decays with D → $$ {K}_S^0 $$h+h− (h = π, K), Journal of High Energy Physics, Vol: 2024
<jats:title>A<jats:sc>bstract</jats:sc> </jats:title><jats:p>A measurement of <jats:italic>CP</jats:italic>-violating observables in <jats:italic>B</jats:italic><jats:sup>±</jats:sup> → <jats:italic>D</jats:italic><jats:sup>*</jats:sup><jats:italic>K</jats:italic><jats:sup>±</jats:sup> and <jats:italic>B</jats:italic><jats:sup>±</jats:sup> → <jats:italic>D</jats:italic><jats:sup>*</jats:sup>π<jats:sup>±</jats:sup> decays is made where the photon or neutral pion from the <jats:italic>D</jats:italic><jats:sup>*</jats:sup><jats:italic>→ D</jats:italic>γ or <jats:italic>D</jats:italic><jats:sup>*</jats:sup><jats:italic>→ D</jats:italic>π<jats:sup>0</jats:sup> decay is not reconstructed. The <jats:italic>D</jats:italic> meson is reconstructed in the self-conjugate decay modes, <jats:italic>D</jats:italic> → <jats:inline-formula><jats:alternatives><jats:tex-math>$$ {K}_S^0 $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mi>K</mml:mi> <mml:mi>S</mml:mi> <mml:mn>0</mml:mn> </mml:msubsup> </mml:math></jats:alternatives></jats:inline-formula>π<jats:sup>+</jats:sup>π<jats:sup>−</jats:sup> or <jats:italic>D</jats:italic> → <jats:inline-formula><jats:alternatives><jats:tex-math>$$ {K}_S^0 $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML">
Aaij R, Abdelmotteleb ASW, Abellan Beteta C, et al., 2024, Measurement of the Z boson production cross-section in pp collisions at $$ \sqrt{s} $$ = 5.02 TeV, Journal of High Energy Physics, Vol: 2024
<jats:title>A<jats:sc>bstract</jats:sc> </jats:title><jats:p>The first measurement of the <jats:italic>Z</jats:italic> boson production cross-section at centre-of-mass energy <jats:inline-formula><jats:alternatives><jats:tex-math>$$ \sqrt{s} $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msqrt> <mml:mi>s</mml:mi> </mml:msqrt> </mml:math></jats:alternatives></jats:inline-formula> = 5<jats:italic>.</jats:italic>02 TeV in the forward region is reported, using <jats:italic>pp</jats:italic> collision data collected by the LHCb experiment in year 2017, corresponding to an integrated luminosity of 100 ± 2 pb<jats:sup><jats:italic>−</jats:italic>1</jats:sup>. The production cross-section is measured for final-state muons in the pseudorapidity range 2<jats:italic>.</jats:italic>0 <jats:italic>< η <</jats:italic> 4<jats:italic>.</jats:italic>5 with transverse momentum <jats:italic>p</jats:italic><jats:sub>T</jats:sub><jats:italic>></jats:italic> 20 GeV/<jats:italic>c</jats:italic>. The integrated cross-section is determined to be<jats:disp-formula><jats:alternatives><jats:tex-math>$$ {\sigma}_{Z\to \mu +\mu -}=39.6\pm 0.7\left(\textrm{stat}\right)\pm 0.6\left(\textrm{syst}\right)\pm 0.8\left(\textrm{lumi}\right)\textrm{pb} $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>σ</mml:mi> <mml:mrow> <mml:mi>Z</mml:mi> <mml:mo>→</mml:mo>
Aaij R, Abdelmotteleb ASW, Abellan Beteta C, et al., 2024, A search for rare B → Dμ+μ− decays, Journal of High Energy Physics, Vol: 2024
<jats:title>A<jats:sc>bstract</jats:sc> </jats:title><jats:p>A search for rare <jats:italic>B → Dμ</jats:italic><jats:sup>+</jats:sup><jats:italic>μ</jats:italic><jats:sup><jats:italic>−</jats:italic></jats:sup> decays is performed using proton-proton collision data collected by the LHCb experiment, corresponding to an integrated luminosity of 9 fb<jats:sup><jats:italic>−</jats:italic>1</jats:sup>. No significant signals are observed in the non-resonant <jats:italic>μ</jats:italic><jats:sup>+</jats:sup><jats:italic>μ</jats:italic><jats:sup><jats:italic>−</jats:italic></jats:sup> modes, and upper limits of <jats:inline-formula><jats:alternatives><jats:tex-math>$$ \mathcal{B}\left({B}^0\to {\overline{D}}^0{\mu}^{+}{\mu}^{-}\right)<5.1\times {10}^{-8} $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>B</mml:mi> <mml:mfenced> <mml:mrow> <mml:msup> <mml:mi>B</mml:mi> <mml:mn>0</mml:mn> </mml:msup> <mml:mo>→</mml:mo> <mml:msup> <mml:mover> <mml:mi>D</mml:mi> <mml:mo>¯</mml:mo> </mml:mover> <mml:mn>0</mml:mn> </mml:msup> <mml:msup> <mml:mi>μ</mml:mi> <mml:mo>+</mml:mo> </mml:msup>
Aaij R, Abdelmotteleb ASW, Abellan Beteta C, et al., 2024, Improved Measurement of CP Violation Parameters in B_{s}^{0}→J/ψK^{+}K^{-} Decays in the Vicinity of the ϕ(1020) Resonance., Phys Rev Lett, Vol: 132
The decay-time-dependent CP asymmetry in B_{s}^{0}→J/ψ(→μ^{+}μ^{-})K^{+}K^{-} decays is measured using proton-proton collision data, corresponding to an integrated luminosity of 6 fb^{-1}, collected with the LHCb detector at a center-of-mass energy of 13 TeV. Using a sample of approximately 349 000 B_{s}^{0} signal decays with an invariant K^{+}K^{-} mass in the vicinity of the ϕ(1020) resonance, the CP-violating phase ϕ_{s} is measured, along with the difference in decay widths of the light and heavy mass eigenstates of the B_{s}^{0}-B[over ¯]_{s}^{0} system, ΔΓ_{s}, and the difference of the average B_{s}^{0} and B^{0} meson decay widths, Γ_{s}-Γ_{d}. The values obtained are ϕ_{s}=-0.039±0.022±0.006 rad, ΔΓ_{s}=0.0845±0.0044±0.0024 ps^{-1}, and Γ_{s}-Γ_{d}=-0.0056_{-0.0015}^{+0.0013}±0.0014 ps^{-1}, where the first uncertainty is statistical and the second systematic. These are the most precise single measurements to date and are consistent with expectations based on the Standard Model and with the previous LHCb analyses of this decay. These results are combined with previous independent LHCb measurements. The phase ϕ_{s} is also measured independently for each polarization state of the K^{+}K^{-} system and shows no evidence for polarization dependence.
Aaij R, Abdelmotteleb ASW, Abellan Beteta C, et al., 2024, Production of η and η′ mesons in pp and pPb collisions, Physical Review C, Vol: 109, ISSN: 2469-9985
The production of η and η′ 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 5.02 and 13TeV and proton-lead collisions are studied at a center-of-mass energy per nucleon of 8.16TeV. The studies are performed in center-of-mass (c.m.) rapidity regions 2.5<yc.m.<3.5 (forward rapidity) and -4.0<yc.m.<-3.0 (backward rapidity) defined relative to the proton beam direction. The η and η′ production cross sections are measured differentially as a function of transverse momentum for 1.5<pT<10GeV and 3<pT<10GeV, respectively. The differential cross sections are used to calculate nuclear modification factors. The nuclear modification factors for η and η′ mesons agree at both forward and backward rapidity, showing no significant evidence of mass dependence. The differential cross sections of η mesons are also used to calculate η/π0 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 and η′ meson fragmentation.
Aaij R, Abdelmotteleb ASW, Beteta CA, et al., 2024, Helium identification with LHCb, Journal of Instrumentation, Vol: 19
The identification of helium nuclei at LHCb is achieved using a method based on measurements of ionisation losses in the silicon sensors and timing measurements in the Outer Tracker drift tubes. The background from photon conversions is reduced using the RICH detectors and an isolation requirement. The method is developed using pp collision data at √s = 13 TeV recorded by the LHCb experiment in the years 2016 to 2018, corresponding to an integrated luminosity of 5.5 fb−1. A total of around 105 helium and antihelium candidates are identified with negligible background contamination. The helium identification efficiency is estimated to be approximately 50% with a corresponding background rejection rate of up to O(1012). These results demonstrate the feasibility of a rich programme of measurements of QCD and astrophysics interest involving light nuclei.
Aaij R, Abdelmotteleb ASW, Beteta CA, et al., 2024, Momentum scale calibration of the LHCb spectrometer, Journal of Instrumentation, Vol: 19
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/ → +− and B+ → J/K+ decays and leads to a relative accuracy of 3 × 10−4 on the momentum scale.
Aaij R, Abdelmotteleb ASW, Abellan Beteta C, et al., 2024, Measurement of CP Violation in B^{0}→ψ(→ℓ^{+}ℓ^{-})K_{S}^{0}(→π^{+}π^{-}) Decays., Phys Rev Lett, Vol: 132
A measurement of time-dependent CP violation in the decays of B^{0} and B[over ¯]^{0} mesons to the final states J/ψ(→μ^{+}μ^{-})K_{S}^{0}, ψ(2S)(→μ^{+}μ^{-})K_{S}^{0} and J/ψ(→e^{+}e^{-})K_{S}^{0} with K_{S}^{0}→π^{+}π^{-} is presented. The data correspond to an integrated luminosity of 6 fb^{-1} collected at a center-of-mass energy of sqrt[s]=13 TeV with the LHCb detector. The CP-violation parameters are measured to be S_{ψK_{S}^{0}}=0.717±0.013(stat)±0.008(syst) and C_{ψK_{S}^{0}}=0.008±0.012(stat)±0.003(syst). This measurement of S_{ψK_{S}^{0}} represents the most precise single measurement of the CKM angle β to date and is more precise than the current world average. In addition, measurements of the CP-violation parameters of the individual channels are reported and a combination with the LHCb Run 1 measurements is performed.
Aaij R, Abdelmotteleb ASW, Abellan Beteta C, et al., 2024, Measurement of prompt D <sup>+</sup> and Ds+ production in pPb collisions at √sNN = 5.02 TeV, Journal of High Energy Physics, Vol: 2024
The production of prompt D + and Ds+ mesons is studied in proton-lead collisions at a centre-of-mass energy of sNN = 5.02 TeV. The data sample corresponding to an integrated luminosity of (1.58 ± 0.02)nb −1 is collected by the LHCb experiment at the LHC. The differential production cross-sections are measured using D + and Ds+ candidates with transverse momentum in the range of 0 < p T < 14 GeV/c and rapidities in the ranges of 1.5 < y ∗ < 4.0 and –5.0 < y ∗ < –2.5 in the nucleon-nucleon centre-of-mass system. For both particles, the nuclear modification factor and the forward-backward production ratio are determined. These results are compared with theoretical models that include initial-state nuclear effects. In addition, measurements of the cross-section ratios between D +, Ds+ and D 0 mesons are presented, providing a baseline for studying the charm hadronization in lead-lead collisions at LHC energies. [Figure not available: see fulltext.].
Aaij R, Abdelmotteleb ASW, Abellan Beteta C, et al., 2023, Measurement of the CKM angle γ using the B <sup>±</sup> → D <sup>*</sup> h <sup>±</sup> channels, Journal of High Energy Physics, Vol: 2023
A measurement of the CP-violating observables from B ± → D * K ± and B ± → D * π ± decays is presented, where D *(D) is an admixture of D *0 and D¯ ∗ 0 (D 0 and D¯) states and is reconstructed through the decay chains D * → Dπ 0 /γ and D→KS0π+π−/KS0K+K− . The measurement is performed by analysing the signal yield variation across the D decay phase space and is independent of any amplitude model. The data sample used was collected by the LHCb experiment in proton-proton collisions and corresponds to a total integrated luminosity of 9 fb−1 at centre-of-mass energies of 7, 8 and 13 TeV. The CKM angle γ is determined to be (69−14+13)∘ using the measured CP-violating observables. The hadronic parameters rBD∗K±,rBD∗π±,δBD∗K±,δBD∗π± , which are the ratios and strong phase differences between favoured and suppressed B ± decays, are also reported. [Figure not available: see fulltext.]
Aaij R, Abdelmotteleb ASW, Abellan Beteta C, et al., 2023, Observation of New Baryons in the Ξ_{b}^{-}π^{+}π^{-} and Ξ_{b}^{0}π^{+}π^{-} Systems., Phys Rev Lett, Vol: 131
The first observation and study of two new baryonic structures in the final state Ξ_{b}^{0}π^{+}π^{-} and the confirmation of the Ξ_{b}(6100)^{-} state in the Ξ_{b}^{-}π^{+}π^{-} decay mode are reported using proton-proton collision data collected by the LHCb experiment, corresponding to an integrated luminosity of 9 fb^{-1}. In addition, the properties of the known Ξ_{b}^{*0}, Ξ_{b}^{'-} and Ξ_{b}^{*-} resonances are measured with improved precision. The new decay mode of the Ξ_{b}^{0} baryon to the Ξ_{c}^{+} π^{-} π^{+} π^{-} final state is observed and exploited for the first time in these measurements.
Aaij R, Abdelmotteleb ASW, Abellan Beteta C, et al., 2023, Precision Measurement of CP Violation in the Penguin-Mediated Decay B_{s}^{0}→ϕϕ., Phys Rev Lett, Vol: 131
A flavor-tagged time-dependent angular analysis of the decay B_{s}^{0}→ϕϕ is performed using pp collision data collected by the LHCb experiment at the center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 6 fb^{-1}. The CP-violating phase and direct CP-violation parameter are measured to be ϕ_{s}^{ss[over ¯]s}=-0.042±0.075±0.009 rad and |λ|=1.004±0.030±0.009, respectively, assuming the same values for all polarization states of the ϕϕ system. In these results, the first uncertainties are statistical and the second systematic. These parameters are also determined separately for each polarization state, showing no evidence for polarization dependence. The results are combined with previous LHCb measurements using pp collisions at center-of-mass energies of 7 and 8 TeV, yielding ϕ_{s}^{ss[over ¯]s}=-0.074±0.069 rad and |λ|=1.009±0.030. This is the most precise study of time-dependent CP violation in a penguin-dominated B meson decay. The results are consistent with CP symmetry and with the standard model predictions.
Aaij R, Abdelmotteleb ASW, Abellan Beteta C, et al., 2023, Evidence for the decays B0 → $$ \overline{D} $$(*)0ϕ and updated measurements of the branching fractions of the $$ {B}_s^0 $$ → $$ \overline{D} $$(*)0ϕ decays, Journal of High Energy Physics, Vol: 2023
<jats:title>A<jats:sc>bstract</jats:sc> </jats:title><jats:p>Evidence for the decays <jats:italic>B</jats:italic><jats:sup>0</jats:sup><jats:italic>→</jats:italic><jats:inline-formula><jats:alternatives><jats:tex-math>$$ \overline{D} $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mover> <mml:mi>D</mml:mi> <mml:mo>¯</mml:mo> </mml:mover> </mml:math></jats:alternatives></jats:inline-formula><jats:sup>0</jats:sup><jats:italic>ϕ</jats:italic> and <jats:italic>B</jats:italic><jats:sup>0</jats:sup><jats:italic>→</jats:italic><jats:inline-formula><jats:alternatives><jats:tex-math>$$ \overline{D} $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mover> <mml:mi>D</mml:mi> <mml:mo>¯</mml:mo> </mml:mover> </mml:math></jats:alternatives></jats:inline-formula><jats:sup>*0</jats:sup><jats:italic>ϕ</jats:italic> is reported with a significance of 3.6 <jats:italic>σ</jats:italic> and 4.3 <jats:italic>σ</jats:italic>, respectively. The analysis employs <jats:italic>pp</jats:italic> collision data at centre-of-mass energies <jats:inline-formula><jats:alternatives><jats:tex-math>$$ \sqrt{s} $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msqrt> <mml:mi>s</mml:mi> </mml:msqrt>
Aaij R, Abdelmotteleb ASW, Abellan Beteta C, et al., 2023, Measurement of the Λ_{b}^{0}→Λ(1520)μ^{+}μ^{-} Differential Branching Fraction., Phys Rev Lett, Vol: 131
The branching fraction of the rare decay Λ_{b}^{0}→Λ(1520)μ^{+}μ^{-} is measured for the first time, in the squared dimuon mass intervals q^{2}, excluding the J/ψ and ψ(2S) regions. The data sample analyzed was collected by the LHCb experiment at center-of-mass energies of 7, 8, and 13 TeV, corresponding to a total integrated luminosity of 9 fb^{-1}. The result in the highest q^{2} interval, q^{2}>15.0 GeV^{2}/c^{4}, where theoretical predictions have the smallest model dependence, agrees with the predictions.
Aaij R, Abdelmotteleb ASW, Abellan Beteta C, et al., 2023, Observation of the decays B(s)0 → D<inf>s1</inf>(2536)<sup>∓</sup> K <sup> ±</sup>, Journal of High Energy Physics, Vol: 2023
This paper reports the observation of the decays B(s)0 → Ds1(2536)∓ K ± using proton-proton collision data collected by the LHCb experiment, corresponding to an integrated luminosity of 9 fb −1. The branching fractions of these decays are measured relative to the normalisation channel B 0 → D¯ 0 K + K −. The Ds1(2536) − meson is reconstructed in the D¯ *(2007)0 K − decay channel and the products of branching fractions are measured to be B(Bs0→Ds1(2536)∓K±)×B(Ds1(2536)−→D¯∗(2007)0K−)=(2.49±0.11±0.12±0.25±0.06)×10−5,B(B0→Ds1(2536)∓K±)×B(Ds1(2536)−→D¯∗(2007)0K−)=(0.510±0.021±0.036±0.050)×10−5. The first uncertainty is statistical, the second systematic, and the third arises from the uncertainty of the branching fraction of the B 0 → D¯ 0 K + K − normalisation channel. The last uncertainty in the Bs0 result is due to the limited knowledge of the fragmentation fraction ratio, fs/fd. The significance for the Bs0 and B 0 signals is larger than 10 σ. The ratio of the helicity amplitudes which governs the angular distribution of the Ds1(2536) − → D¯ *(2007)0 K − decay is determined from the data. The ratio of the S- and D-wave amplitudes is found to be 1.11 ± 0.15 ± 0.06 and the phase difference between them 0.70 ± 0.09 ± 0.04 rad, where the first uncertainty is statistical and the second systematic. [Figure not available: see fulltext.].
Aaij R, Beteta CA, Ackernley T, et al., 2023, Addendum: Test of lepton universality in beauty-quark decays, Nature Physics, Vol: 19, Pages: 1517-1517, ISSN: 1745-2473
Aaij R, Abdelmotteleb ASW, Abellan Beteta C, et al., 2023, Evidence of a J/ψK_{S}^{0} Structure in B^{0}→J/ψϕK_{S}^{0} Decays., Phys Rev Lett, Vol: 131
An amplitude analysis of B^{0}→J/ψϕK_{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. Evidence with a significance of 4.0 standard deviations of a structure in the J/ψK_{S}^{0} system, named T_{ψs1}^{θ}(4000)^{0}, is seen, with its mass and width measured to be 3991_{-10}^{+12} _{-17}^{+9} MeV/c^{2} and 105_{-25}^{+29} _{-23}^{+17} MeV, respectively, where the first uncertainty is statistical and the second systematic. The T_{ψs1}^{θ}(4000)^{0} state is likely to be the isospin partner of the T_{ψs1}^{θ}(4000)^{+} state, previously observed in the J/ψK^{+} system of the B^{+}→J/ψϕK^{+} decay. When isospin symmetry for the charged and neutral T_{ψs1}^{θ}(4000) states is assumed, the signal significance increases to 5.4 standard deviations.
Aaij R, Abdelmotteleb ASW, Abellan Beteta C, et al., 2023, Observation of New Ω_{c}^{0} States Decaying to the Ξ_{c}^{+}K^{-} Final State., Phys Rev Lett, Vol: 131
Two new excited states, Ω_{c}(3185)^{0} and Ω_{c}(3327)^{0}, are observed in the Ξ_{c}^{+}K^{-} invariant-mass spectrum using proton-proton collision data collected by the LHCb experiment, corresponding to an integrated luminosity of 9 fb^{-1}. Five previously observed excited Ω_{c}^{0} states are confirmed, namely Ω_{c}(3000)^{0}, Ω_{c}(3050)^{0}, Ω_{c}(3065)^{0}, Ω_{c}(3090)^{0}, and Ω_{c}(3119)^{0}. The masses and widths of these seven states are measured with the highest precision to date.
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