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  • Springer Science and Business Media LLC  (342)
  • Manca, G.  (342)
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  • Springer Science and Business Media LLC  (342)
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  • 1
    In: Journal of High Energy Physics, Springer Science and Business Media LLC, Vol. 2024, No. 3 ( 2024-03-19)
    Abstract: A search for CP violation in $$ {D}^0\to {K}_S^0{K}^{+}{\pi}^{-} $$ D 0 → K S 0 K + π − and $$ {D}^0\to {K}_S^0{K}^{-}{\pi}^{+} $$ D 0 → K S 0 K − π + decays is reported. The search is performed using an unbinned model-independent method known as the energy test that probes local CP violation in the phase space of the decays. The data analysed correspond to an integrated luminosity of 5 . 4 fb − 1 collected in proton-proton collisions by the LHCb experiment at a centre-of-mass energy of $$ \sqrt{s} $$ s = 13 TeV, amounting to approximately 950 thousand and 620 thousand signal candidates for the $$ {D}^0\to {K}_S^0{K}^{-}{\pi}^{+} $$ D 0 → K S 0 K − π + and $$ {D}^0\to {K}_S^0{K}^{+}{\pi}^{-} $$ D 0 → K S 0 K + π − modes, respectively. The method is validated using D 0 → K − π + π − π + and $$ {D}^0\to {K}_S^0{\pi}^{+}{\pi}^{-} $$ D 0 → K S 0 π + π − decays, where CP -violating effects are expected to be negligible, and using background-enhanced regions of the signal decays. The results are consistent with CP symmetry in both the $$ {D}^0\to {K}_S^0{K}^{-}{\pi}^{+} $$ D 0 → K S 0 K − π + and the $$ {D}^0\to {K}_S^0{K}^{+}{\pi}^{-} $$ D 0 → K S 0 K + π − decays, with p -values for the hypothesis of no CP violation of 70% and 66%, respectively.
    Type of Medium: Online Resource
    ISSN: 1029-8479
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2024
    detail.hit.zdb_id: 2027350-2
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  • 2
    In: Journal of High Energy Physics, Springer Science and Business Media LLC, Vol. 2024, No. 4 ( 2024-04-19)
    Abstract: The production of ψ (2 S ) mesons in proton-lead collisions at a centre-of-mass energy per nucleon pair of $$ \sqrt{s_{\textrm{NN}}} $$ s NN = 8 . 16 TeV is studied with the LHCb detector using data corresponding to an integrated luminosity of 34 nb − 1 . The prompt and nonprompt ψ (2 S ) production cross-sections and the ratio of the ψ (2 S ) to J/ψ cross-section are measured as a function of the meson transverse momentum and rapidity in the nucleon-nucleon centre-of-mass frame, together with forward-to-backward ratios and nuclear modification factors. The production of prompt ψ (2 S ) is observed to be more suppressed compared to pp collisions than the prompt J/ψ production, while the nonprompt productions have similar suppression factors.
    Type of Medium: Online Resource
    ISSN: 1029-8479
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2024
    detail.hit.zdb_id: 2027350-2
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  • 3
    In: Journal of High Energy Physics, Springer Science and Business Media LLC, Vol. 2024, No. 2 ( 2024-02-13)
    Abstract: The first measurement of the Z boson production cross-section at centre-of-mass energy $$ \sqrt{s} $$ s = 5 . 02 TeV 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 〈 η 〈 4 . 5 with transverse momentum p T 〉 20 GeV/ c . The integrated cross-section is determined to be $$ {\sigma}_{Z\to \mu +\mu -}=39.6\pm 0.7\left(\textrm{stat}\right)\pm 0.6\left(\textrm{syst}\right)\pm 0.8\left(\textrm{lumi}\right)\textrm{pb} $$ σ Z → μ + μ − = 39.6 ± 0.7 stat ± 0.6 syst ± 0.8 lumi pb for the di-muon invariant mass in the range 60 〈 M μμ 〈 120 GeV/ 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 constant. Based on a previous LHCb measurement of the Z boson production cross-section in p Pb collisions at $$ \sqrt{s_{NN}} $$ s NN = 5 . 02 TeV, the nuclear modification factor R p Pb is measured for the first time at this energy. The measured values are $$ {1.2}_{-0.3}^{+0.5} $$ 1.2 − 0.3 + 0.5 (stat) ± 0 . 1(syst) in the forward region (1.53 〈 $$ {y}_{\mu}^{\ast } $$ y μ ∗ 〈 4 . 03) and $$ {3.6}_{-0.9}^{+1.6} $$ 3.6 − 0.9 + 1.6 (stat) ± 0 . 2(syst) in the backward region ( − 4 . 97 〈 $$ {y}_{\mu}^{\ast } $$ y μ ∗ 〈 − 2 . 47), where $$ {y}_{\mu}^{\ast } $$ y μ ∗ represents the muon rapidity in the centre-of-mass frame.
    Type of Medium: Online Resource
    ISSN: 1029-8479
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2024
    detail.hit.zdb_id: 2027350-2
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  • 4
    In: Journal of High Energy Physics, Springer Science and Business Media LLC, Vol. 2024, No. 3 ( 2024-03-14)
    Abstract: The production cross-section of J/ψ pairs in proton-proton collisions at a centre-of-mass energy of $$ \sqrt{s} $$ s = 13 TeV is measured using a data sample corresponding to an integrated luminosity of 4 . 2 fb − 1 collected by the LHCb experiment. The measurement is performed with both J/ψ mesons in the transverse momentum range 0 〈 p T 〈 14 GeV/ c and rapidity range 2 . 0 〈 y 〈 4 . 5. The cross-section of this process is measured to be 16 . 36 ± 0 . 28 (stat) ± 0 . 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 ∆ y between the two J/ψ mesons. The effective cross-section of double-parton scattering is measured to be σ eff = 13 . 1 ± 1 . 8 (stat) ± 2 . 3 (syst) mb. The distribution of the azimuthal angle ϕ CS of one of the J/ψ mesons in the Collins-Soper frame and the p T -spectrum of the J/ψ pairs are also measured for the study of the gluon transverse-momentum dependent distributions inside protons. The extracted values of ⟨cos 2 ϕ CS ⟩ and ⟨cos 4 ϕ CS ⟩ are consistent with zero, but the presence of azimuthal asymmetry at a few percent level is allowed.
    Type of Medium: Online Resource
    ISSN: 1029-8479
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2024
    detail.hit.zdb_id: 2027350-2
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  • 5
    In: Journal of High Energy Physics, Springer Science and Business Media LLC, Vol. 2024, No. 2 ( 2024-02-16)
    Abstract: A measurement of CP -violating observables in B ± → D * K ± and B ± → D * π ± decays is made where the photon or neutral pion from the D * → D γ or D * → D π 0 decay is not reconstructed. The D meson is reconstructed in the self-conjugate decay modes, D → $$ {K}_S^0 $$ K S 0 π + π − or D → $$ {K}_S^0 $$ K S 0 K + K − . The distribution of signal yields in the D decay phase space is analysed in a model-independent way. The measurement uses a data sample collected in proton-proton collisions at centre-of-mass energies of 7, 8, and 13 TeV, corresponding to a total integrated luminosity of approximately 9 fb − 1 . The B ± → D * K ± and B ± → D * π ± CP -violating observables are interpreted in terms of hadronic parameters and the CKM angle γ, resulting in a measurement of γ = ( $$ {92}_{-17}^{+21} $$ 92 − 17 + 21 ) ° . The total uncertainty includes the statistical and systematic uncertainties, and the uncertainty due to external strong-phase inputs.
    Type of Medium: Online Resource
    ISSN: 1029-8479
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2024
    detail.hit.zdb_id: 2027350-2
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  • 6
    In: The European Physical Journal C, Springer Science and Business Media LLC, Vol. 84, No. 7 ( 2024-07-30)
    Abstract: A method is presented to reconstruct charged particles with lifetimes between $$10\,\text {ps} $$ 10 ps and $$10\,\text {ns},$$ 10 ns , which considers a combination of their decay products and the partial tracks created by the initial charged particle. Using the $${\varXi } ^- $$ Ξ - baryon as a benchmark, the method is demonstrated with simulated events and proton-proton collision data at $$\sqrt{s} =13\,\text {TeV},$$ s = 13 TeV , corresponding to an integrated luminosity of 2.0 $$\,\text {fb} ^{-1}$$ fb - 1 collected with the LHCb detector in 2018. Significant improvements in the angular resolution and the signal purity are obtained. The method is implemented as part of the LHCb Run 3 event trigger in a set of requirements to select detached hyperons. This is the first demonstration of the applicability of this approach at the LHC, and the first to show its scaling with instantaneous luminosity.
    Type of Medium: Online Resource
    ISSN: 1434-6052
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2024
    detail.hit.zdb_id: 1459069-4
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  • 7
    In: The European Physical Journal C, Springer Science and Business Media LLC, Vol. 84, No. 5 ( 2024-05-07)
    Abstract: The first search for nonresonant $${{B} _{c} ^+} \!\rightarrow {{\pi } ^+} {\mu ^+\mu ^-} $$ B c + → π + μ + μ - decays is reported. The analysis uses proton–proton collision data collected with the LHCb detector between 2011 and 2018, corresponding to an integrated luminosity of 9 $$\,\text {fb} ^{-1}$$ fb - 1 . No evidence for an excess of signal events over background is observed and an upper limit is set on the branching fraction ratio $${\mathcal {B}} ({{B} _{c} ^+} \!\rightarrow {{\pi } ^+} {\mu ^+\mu ^-} )/{\mathcal {B}} ({{B} _{c} ^+} \!\rightarrow {{J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }} {{\pi } ^+} ) 〈 2.1\times 10^{-4}$$ B ( B c + → π + μ + μ - ) / B ( B c + → J / ψ π + ) 〈 2.1 × 10 - 4 at $$90\%$$ 90 % confidence level. Additionally, an updated measurement of the ratio of the $${{B} _{c} ^+} \!\rightarrow {\psi {(2S)}} {{\pi } ^+} $$ B c + → ψ ( 2 S ) π + and $${{B} _{c} ^+} \!\rightarrow {{J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }} {{\pi } ^+} $$ B c + → J / ψ π + branching fractions is reported. The ratio $${\mathcal {B}} ({{B} _{c} ^+} \!\rightarrow {\psi {(2S)}} {{\pi } ^+} )/{\mathcal {B}} ({{B} _{c} ^+} \!\rightarrow {{J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }} {{\pi } ^+} )$$ B ( B c + → ψ ( 2 S ) π + ) / B ( B c + → J / ψ π + ) is measured to be $$0.254\pm 0.018 \pm 0.003 \pm 0.005$$ 0.254 ± 0.018 ± 0.003 ± 0.005 , where the first uncertainty is statistical, the second systematic, and the third is due to the uncertainties on the branching fractions of the leptonic $${J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }$$ J / ψ  and $$\psi {(2S)}$$ ψ ( 2 S )  decays. This measurement is the most precise to date and is consistent with previous LHCb results.
    Type of Medium: Online Resource
    ISSN: 1434-6052
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2024
    detail.hit.zdb_id: 1459069-4
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  • 8
    In: Journal of High Energy Physics, Springer Science and Business Media LLC, Vol. 2024, No. 7 ( 2024-07-11)
    Abstract: 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.
    Type of Medium: Online Resource
    ISSN: 1029-8479
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2024
    detail.hit.zdb_id: 2027350-2
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  • 9
    In: The European Physical Journal C, Springer Science and Business Media LLC, Vol. 84, No. 3 ( 2024-03-07)
    Abstract: The $$\Xi _b^0 \rightarrow \Xi _c^+ D_s^-$$ Ξ b 0 → Ξ c + D s - and $$\Xi _b^- \rightarrow \Xi _c^0 D_s^-$$ Ξ b - → Ξ c 0 D s - decays are observed for the first time using proton-proton collision data collected by the LHCb experiment at a centre-of-mass energy of $$\sqrt{s}=13\,\,\textrm{TeV}$$ s = 13 TeV , corresponding to an integrated luminosity of $$5.1\,\,\textrm{fb}^{-1}$$ 5.1 fb - 1 . The branching fractions times the production cross-sections of $$\Xi _b$$ Ξ b baryons relative to that of $$\Lambda _b^0$$ Λ b 0 baryon are measured to be $$\begin{aligned} \mathcal {R}\left( \frac{\Xi _b^0}{\Lambda _b^0}\right) & \equiv \frac{\sigma \left( \Xi _b^0\right) }{\sigma \left( \Lambda _b^0\right) } \times \frac{\mathcal {B}\left( \Xi _b^0 \rightarrow \Xi _c^+ D_s^-\right) }{\mathcal {B}\left( \Lambda _b^0 \rightarrow \Lambda _c^0 D_s^-\right) }\\ & =(15.8\pm 1.1\pm 0.6\pm 7.7)\%,\\ \mathcal {R}\left( \frac{\Xi _b^-}{\Lambda _b^0}\right) & \equiv \frac{\sigma \left( \Xi _b^-\right) }{\sigma \left( \Lambda _b^0\right) } \times \frac{\mathcal {B}\left( \Xi _b^- \rightarrow \Xi _c^0 D_s^-\right) }{\mathcal {B}\left( \Lambda _b^0 \rightarrow \Lambda _c^0 D_s^-\right) } \\ & =(16.9\pm 1.3\pm 0.9\pm 4.3)\%, \end{aligned}$$ R Ξ b 0 Λ b 0 ≡ σ Ξ b 0 σ Λ b 0 × B Ξ b 0 → Ξ c + D s - B Λ b 0 → Λ c 0 D s - = ( 15.8 ± 1.1 ± 0.6 ± 7.7 ) % , R Ξ b - Λ b 0 ≡ σ Ξ b - σ Λ b 0 × B Ξ b - → Ξ c 0 D s - B Λ b 0 → Λ c 0 D s - = ( 16.9 ± 1.3 ± 0.9 ± 4.3 ) % , where the first uncertainties are statistical, the second systematic, and the third due to the uncertainties on the decay branching fractions of relevant charmed baryons. The masses of $$\Xi _b^0$$ Ξ b 0 and $$\Xi _b^-$$ Ξ b - baryons are measured to be $$m_{\Xi _b^0}=5791.12\pm 0.60\pm 0.45\pm 0.24\,\,\textrm{MeV}/c^2$$ m Ξ b 0 = 5791.12 ± 0.60 ± 0.45 ± 0.24 MeV / c 2 and $$m_{\Xi _b^-}=5797.02\pm 0.63\pm 0.49\pm 0.29\,\,\textrm{MeV}/c^2$$ m Ξ b - = 5797.02 ± 0.63 ± 0.49 ± 0.29 MeV / c 2 , where the uncertainties are statistical, systematic, and those due to charmed-hadron masses, respectively.
    Type of Medium: Online Resource
    ISSN: 1434-6052
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2024
    detail.hit.zdb_id: 1459069-4
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  • 10
    In: Journal of High Energy Physics, Springer Science and Business Media LLC, Vol. 2023, No. 10 ( 2023-10-17)
    Abstract: This paper reports the observation of the decays $$ {B}_{(s)}^0 $$ B s 0 → D s 1 (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 → $$ \overline{D} $$ D ¯ 0 K + K − . The D s 1 (2536) − meson is reconstructed in the $$ \overline{D} $$ D ¯ * (2007) 0 K − decay channel and the products of branching fractions are measured to be $$ {\displaystyle \begin{array}{c}\mathcal{B}\left({B}_s^0\to {D}_{s1}{(2536)}^{\mp }{K}^{\pm}\right)\times \mathcal{B}\left({D}_{s1}{(2536)}^{-}\to {\overline{D}}^{\ast }{(2007)}^0{K}^{-}\right)\\ {}=\left(2.49\pm 0.11\pm 0.12\pm 0.25\pm 0.06\right)\times {10}^{-5},\\ {}\mathcal{B}\left({B}^0\to {D}_{s1}{(2536)}^{\mp }{K}^{\pm}\right)\times \mathcal{B}\left({D}_{s1}{(2536)}^{-}\to {\overline{D}}^{\ast }{(2007)}^0{K}^{-}\right)\\ {}=\left(0.510\pm 0.021\pm 0.036\pm 0.050\right)\times {10}^{-5}.\end{array}} $$ B B s 0 → D s 1 2536 ∓ K ± × B D s 1 2536 − → D ¯ ∗ 2007 0 K − = 2.49 ± 0.11 ± 0.12 ± 0.25 ± 0.06 × 10 − 5 , B B 0 → D s 1 2536 ∓ K ± × B D s 1 2536 − → D ¯ ∗ 2007 0 K − = 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 → $$ \overline{D} $$ D ¯ 0 K + K − normalisation channel. The last uncertainty in the $$ {B}_s^0 $$ B s 0 result is due to the limited knowledge of the fragmentation fraction ratio, f s / f d . The significance for the $$ {B}_s^0 $$ B s 0 and B 0 signals is larger than 10 σ . The ratio of the helicity amplitudes which governs the angular distribution of the D s 1 (2536) − → $$ \overline{D} $$ 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.
    Type of Medium: Online Resource
    ISSN: 1029-8479
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2023
    detail.hit.zdb_id: 2027350-2
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