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Andreotti, M.

Publications and source records attributed to Andreotti, M..

At least 37 records · Page 2
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DOE OSTI2023

Observation of the B + → Jψη'K + decay

The B + → Jψη'K + decay is observed for the first time using proton-proton collision data collected by the LHCb experiment at centre-of-mass energies of 7, 8, and 13 TeV, corresponding to a total integrated luminosity of 9 fb -1 . The branching fraction of this decay is measured relative to the known branching fraction of the B + → ψ (2S)K + decay and found to be $\frac{\mathcal{B}(B^+ → Jψη'K^+)}{\mathcal{B}(B^+ → ψ(2S)K^+)}$ = (4.91 ± 0.47 ± 0.29 ± 0.07) X 10 -2 , where the first uncertainty is statistical, the second is systematic and the third is related to external branching fractions. A first look at the J/ψη' mass distribution is performed and no signal of intermediate resonances is observed.

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DOE OSTI2023

Associated production of prompt $J/ψ$ and Υ mesons in $pp$ collisions at $\sqrt{s}$ = 13 TeV

The associated production of prompt J/ψ and Υ mesons in pp collisions at a centre-of-mass energy of $\sqrt{s}$ = 13 TeV is studied using LHCb data, corresponding to an integrated luminosity of 4 fb -1 . The measurement is performed for J/ψ (Υ) mesons with a transverse momentum p T < 10 (30) GeV/c in the rapidity range 2.0 < y < 4.5. In this kinematic range, the cross-section of the associated production of prompt J/ψ and Υ(1S) mesons is measured to be 133 ± 22 ± 7 ± 3 pb, with a signifcance of 7.9 σ, and that of prompt J/ψ and Υ(2S) mesons to be 76 ± 21 ± 4 ± 7 pb, with a signifcance of 4.9 σ. The frst uncertainty is statistical, the second systematic, and the third due to uncertainties on the used branching fractions. This is the frst observation of the associated production of J/ψ and Υ(1S) in proton-proton collisions. Diferential cross-sections are measured as functions of variables that are sensitive to kinematic correlations between the J/ψ and Υ(1S) mesons. The efective cross-sections of the associated production of prompt J/ψ and Υ mesons are obtained and found to be compatible with measurements using other particle productions.

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DOE OSTI2023

${\Lambda}_c^{+}$ polarimetry using the dominant hadronic mode

The polarimeter vector field for multibody decays of a spin-half baryon is intro duced as a generalisation of the baryon asymmetry parameters. Using a recent amplitude analysis of the ${\Lambda}_c^{+}$ → $pK^-π^+$ decay performed at the LHCb experiment, we compute the distribution of the kinematic-dependent polarimeter vector for this process in the space of Mandelstam variables to express the polarised decay rate in a model-agnostic form. The obtained representation can facilitate polarisation measurements of the ${\Lambda}_c^{+}$ baryon and eases inclusion of the ${\Lambda}_c^{+}$ → $pK^-π^+$ decay mode in hadronic amplitude analyses.

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DOE OSTI2023

Study of ${B}_c^{+}$ meson decays to charmonia plus multihadron final states

Four decay modes of the ${B}_c^{+}$ meson into a J/ψ meson and multiple charged kaons or pions are studied using proton-proton collision data, collected with the LHCb detector at centre-of-mass energies of 7, 8, and 13 TeV and corresponding to an integrated luminosity of 9 fb -1 . The decay ${B}_c^{+}$ → J/ψK + K - π + π + π - is observed for the first time, and evidence for the ${B}_c^{+}$ → J/ψ4π + 3π - decay is found. The decay ${B}_c^{+}$ → J/ψ3π + 2π - is observed and the previous observation of the ${B}_c^{+}$ → ψ(2S)π + π + π - decay is confirmed using the ψ(2S) → J/ψπ + π - decay mode. Ratios of the branching fractions of these four ${B}_c^{+}$ decay channels are measured.

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DOE OSTI2023

Amplitude analysis of the ${D}_s^{+}$ → π - π + π + decay

A Dalitz plot analysis of the ${D}_s^{+}$ → π - π + π + decay is presented. The analysis is based on proton-proton collision data recorded by the LHCb experiment at a centre of-mass energy of 8 TeV and corresponding to an integrated luminosity of 1.5 fb -1 . The resonant structure of the decay is obtained using a quasi-model-independent partial-wave analysis, in which the π + π - S-wave amplitude is parameterised as a generic complex function determined by a fit to the data. The S-wave component is found to be dominant, followed by the contribution from spin-2 resonances and a small contribution from spin-1 resonances. The latter includes the first observation of the ${D}_s^{+}$ → ω(782)π + channel in the ${D}_s^{+}$ → π - π + π + decay. The resonant structures of the ${D}_s^{+}$ → π - π + π + and ${D}^{+}$ → π - π + π + decays are compared, providing information about the mechanisms for the hadron formation in these decays.

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DOE OSTI2023

Measurement of the CKM angle γ with B ± → D[K ∓ π ± π ± π ∓ ]h ± decays using a binned phase-space approach

The CKM angle γ is determined from CP-violating observables measured in B ± → D[K ∓ π ± π ± π ∓ ]h ± , (h = K, π) decays, where the measurements are performed in bins of the decay phase-space of the D meson. Using proton-proton collision data collected by the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV, corresponding to a total integrated luminosity of 9 fb –1 , γ is determined to be $\gamma ={\left(54.8\begin{array}{c}+6.0\\ {}-5.8\end{array}\begin{array}{c}+0.6\\ {}-0.6\end{array}\begin{array}{c}+6.7\\ {}-4.3\end{array}\right)}^{\circ },$ where the first uncertainty is statistical, the second systematic and the third from the external inputs on the coherence factors and strong phases of the D-meson decays.

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DOE OSTI2023

Observation of the ${B}_s^0$ → D* + D* - decay

The first observation of the $B^{0}_{s}$ → D* + D* - decay and the measurement of its branching ratio relative to the B 0 → D* + D* - decay are presented. The data sample used corresponds to an integrated luminosit y of 9 fb -1 of proton-proton collisions recorded by the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV between 2011 and 2018. The decay is observed with more than 10 standard deviations and the time-integrated ratio of branching fractions is determined to be $\frac{\mathcal{B}(B^{0}_{s} → D*^+D*^-)}{\mathcal{B}(B^0 → D*^+D*^-)}$ = 0.269 ± 0.032 ± 0.011 ± 0.008, where the first uncertainty is statistical, the second systematic and the third due to the uncertainty of the fragmentation fraction ratio f s /f d . The $B^{0}_{s}$ → D* + D* - branching fraction is calculated to be $\mathcal{B}$ ($B^{0}_{s} → D*^+D*^-)$ = (2.15 ± 0.26 ± 0.09 ± 0.06 ± 0.16) X 10 -4 , where the fourth uncertainty is due to the B 0 → D* + D* - branching fraction. These results are calculated using the average $B^{0}_{s}$ meson lifetime in simulation. Correction factors are reported for scenarios where either a purely heavy or a purely light $B^{0}_{s}$ eigenstate is considered.

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DOE OSTI2023

Observation of the ${\textrm{B}}_{\textrm{s}}^0$ → χ c1 (3872) π + π - decay

The first observation of the ${B}_s^0$ → ( Xc1 (3872) → J/ψπ + π - )π + π - decay is reported using proton-proton collision data, corresponding to integrated luminosities of 1, 2 and 6 fb -1 , collected by the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV, respectively. The ratio of branching fractions relative to the ${B}_s^0$ → (ψ(2S) → J/ψπ + π - )π + π - decay is measured to be $\frac{\mathcal{B}(B^{0}_{s} → X_{c1}(3872)π^+π^-) x \mathcal{B} (X_{c1}(3872) → J/ψπ^+π^-)}{\mathcal{B}(B^0_{s} → ψ(2S)π^+π^-) X \mathcal{B} (ψ(2S) → Jψπ^+π^-)}$ = (6.8 ± 1.1 ± 0.2) x 10 -2 where the first uncertainty is statistical and the second systematic. The mass spectrum of the π + π - system recoiling against the Xc1 (3872) meson exhibits a large contribution from ${B}_s^0$ → Xc1 (3872) (f 0 (980) → π + π - ) decays.

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DOE OSTI2023

Measurement of the ratio of branching fractions $\mathcal{B}\left({B}_c^{+}\to {B}_s^0{\pi}^{+}\right)/\mathcal{B}\left({B}_c^{+}\to J/\psi {\pi}^{+}\right)$

The ratio of branching fractions of ${B}_c^{+}\to {B}_s^0{\pi}^{+}$ and ${B}_c^{+}\to J/\psi {\pi}^{+}$ decays is measured with proton-proton collision data of a centre-of-mass energy of 13 TeV. The data were collected with the LHCb experiment during 2016–2018, corresponding to an integrated luminosity of 5.4 fb –1 . The ${B}_s^0$ mesons are reconstructed via the decays ${B}_s^0\to J/\psi \phi$ and ${B}_s^0\to {D}_s^{-}{\pi}^{+}$. The ratio of branching fractions is measured to be $\mathcal{B}\left({B}_c^{+}\to {B}_s^0{\pi}^{+}\right)/\mathcal{B}\left({B}_c^{+}\to J/\psi {\pi}^{+}\right)=91\pm 10\pm 8\pm 3$ where the first uncertainty is statistical, the second is systematic and the third is due to the knowledge of the branching fractions of the intermediate state decays.

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DOE OSTI2023

Search for CP violation in ${D}_{(s)}^{+}$ → K - K + K + decays

A search for direct CP violation in the Cabibbo-suppressed decay \( {D}_s^{+} \) → K - K + K + and in the doubly Cabibbo-suppressed decay D + → K - K + K + is reported. The analysis is performed with data collected by the LHCb experiment in proton-proton collisions at a centre-of-mass energy of 13 TeV corresponding to an integrated luminosity of 5.6 fb - 1 . The search is conducted by comparing the \( {D}_{(s)}^{+} \) and \( {D}_{(s)}^{-} \) Dalitz-plot distributions through a model-independent binned technique, based on fits to the K - K + K + invariant-mass distributions, with a total of 0.97 (1.27) million \( {D}_s^{+} \) ( D + ) signal candidates. The results are given as p -values for the hypothesis of CP conservation and are found to be 13.3% for the \( {D}_s^{+} \) → K - K + K + decay and 31.6% for the D + → K - K + K + decay. No evidence for CP violation is observed in these decays.

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DOE OSTI2023

Measurement of Υ production in pp collisions at $\sqrt{s}$ = 5 TeV

The production cross-sections of Υ mesons, namely Υ(1S), Υ(2S) and Υ(3S), in pp collisions at $\sqrt{s}$ = 5 TeV are measured with a data sample corresponding to an integrated luminosity of 9.13 ± 0.18 pb –1 collected by the LHCb detector. The Υ mesons are reconstructed in the decay mode Υ → μ + μ – . Double differential cross-sections times branching fractions, as functions of the transverse momentum p T and the rapidity y of the Υ mesons, are measured in the range p T < 20 GeV/c and 2.0 < y < 4.5. The results integrated over these p T and y ranges are $\sigma \left(\textrm{Y}(1S)\right)\times \mathcal{B}\left(\textrm{Y}(1S)\to {\mu}^{+}{\mu}^{-}\right)=2101\pm 33\pm 83\ \textrm{pb},$ $\sigma \left(\textrm{Y}(2S)\right)\times \mathcal{B}\left(\textrm{Y}(2S)\to {\mu}^{+}{\mu}^{-}\right)=526\pm 20\pm 21\ \textrm{pb},$ $\sigma \left(\textrm{Y}(3S)\right)\times \mathcal{B}\left(\textrm{Y}(3S)\to {\mu}^{+}{\mu}^{-}\right)=242\pm 16\pm 10\ \textrm{pb},$ where the first uncertainties are statistical and the second are systematic. The ratios of cross-sections between measurements of two different Υ states and between measurements at different centre-of-mass energies are determined. The nuclear modification factor of Υ(1S) at $\sqrt{s}$ = 5 TeV is updated as well using the directly measured cross-section results from this analysis.

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DOE OSTI2023

Search for the lepton-flavour violating decays B 0 → K *0 τ ± μ ∓

A first search for the lepton-flavour violating decays B 0 → K*0 τ ± μ ∓ is presented. The analysis is performed using a sample of proton-proton collision data, collected with the LHCb detector at centre-of-mass energies of 7, 8 and 13 TeV between 2011 and 2018, corresponding to an integrated luminosity of 9 fb –1 . No significant signal is observed, and upper limits on the branching fractions are determined to be B (B 0 → K* 0 τ + μ – ) < 1.0(1.2) x 10 –5 and B(B 0 → K* 0 τ – μ + ) < 8.2(9.8) x 10 –6 at the 90% (95%) confidence level.

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DOE OSTI2023

Study of exclusive photoproduction of charmonium in ultra-peripheral lead-lead collisions

The cross-sections of exclusive (coherent) photoproduction J/ψ and ψ(2S) mesons in ultra-peripheral PbPb collisions at a nucleon-nucleon centre-of-mass energy of 5.02 TeV are measured using a data sample corresponding to an integrated luminosity of 228 ± 10 µb -1 , collected by the LHCb experiment in 2018. The differential cross-sections are measured separately as a function of transverse momentum and rapidity in the nucleus-nucleus centre-of-mass frame for J/ψ and ψ(2S) mesons. The integrated cross-sections are measured to be $σ^{coh}_{J/ψ}$ = 5.965 ± 0.059 ± 0.232 ± 0.262 mb and $σ^{coh}_{ψ(2S)}$ = 0.923 ± 0.086 ± 0.028 ± 0.040 mb, where the first listed uncertainty is statistical, the second systematic and the third due to the luminosity determination. The cross-section ratio is measured to be $σ^{coh}_{ψ(2S)}$/$σ^{coh}_{J/ψ}$ = 0.155 ± 0.014 ± 0.003, where the first uncertainty is statistical and the second is systematic. These results are compatible with theoretical predictions.

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DOE OSTI2023

Measurement of the ${\Lambda}_c^{+}$ to D 0 production ratio in peripheral PbPb collisions at $\sqrt{s_{\textrm{NN}}}$ = 5.02 TeV

We report on a measurement of the ${\Lambda}_c^{+}$ to D 0 production ratio in peripheral PbPb collisions at $\sqrt{s_{\textrm{NN}}}$ = 5.02 TeV with the LHCb detector in the forward rapidity region 2 < y < 4.5. The ${\Lambda}_c^{+}$ (D 0 ) hadrons are reconstructed via the decay channel ${\Lambda}_c^{+}$ → pK – π + (D 0 → K – π + ) for 2 < p T < 8 GeV/c and in the centrality range of about 65–90%. The results show no significant dependence on p T , y or the mean number of participating nucleons. They are also consistent with similar measurements obtained by the LHCb collaboration in pPb and Pbp collisions at $\sqrt{s_{\textrm{NN}}}$ = 5.02 TeV. The data agree well with predictions from PYTHIA in pp collisions at $\sqrt{s}$ = 5 TeV but are in tension with predictions of the Statistical Hadronization model.

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DOE OSTI2023

Search for the lepton-flavour violating decays B0 → K *0 μ ± e ∓ and ${B}_s^0$ → Φμ ± e ∓

A search for the lepton-flavour violating decays B 0 → K *0 μ ± e ∓ and \( {B}_s^0 \) → Φμ ± e ∓ is presented, using proton-proton collision data collected by the LHCb detector at the LHC, corresponding to an integrated luminosity of 9 fb - 1 . No significant signals are observed and upper limits of $$ {\displaystyle \begin{array}{c}\mathcal{B}\left({B}^0\to {K}^{\ast 0}{\mu}^{+}{e}^{-}\right)<5.7\times {10}^{-9}\left(6.9\times {10}^{-9}\right),\\ {}\mathcal{B}\left({B}^0\to {K}^{\ast 0}{\mu}^{-}{e}^{+}\right)<6.8\times {10}^{-9}\left(7.9\times {10}^{-9}\right),\\ {}\mathcal{B}\left({B}^0\to {K}^{\ast 0}{\mu}^{\pm }{e}^{\mp}\right)<10.1\times {10}^{-9}\left(11.7\times {10}^{-9}\right),\\ {}\mathcal{B}\left({B}_s^0\to \phi {\mu}^{\pm }{e}^{\mp}\right)<16.0\times {10}^{-9}\left(19.8\times {10}^{-9}\right)\end{array}} $$ are set at 90% (95%) confidence level. These results constitute the world’s most stringent limits to date, with the limit on the decay \( {B}_s^0 \) → Φμ ± e ∓ the first being set. In addition, limits are reported for scalar and left-handed lepton-flavour violating New Physics scenarios.

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DOE OSTI2023

Amplitude analysis of the $D^+$ → $π^-π^+π^+$ decay and measurement of the $π^-π^+$ S-wave amplitude

An amplitude analysis of the $D^+$ → $π^-π^+π^+$ decay is performed with a sample corresponding to 1.5 fb -1 of integrated luminosity of $pp$ collisions at a centre-of-mass energy $\sqrt{s}$ = 8 TeV collected by the LHCb detector in 2012. The sample contains approximately six hundred thousand candidates with a signal purity of 95%. The resonant structure is studied through a fit to the Dalitz plot where the $π^-π^+$ S-wave amplitude is extracted as a function of $π^-π^+$ mass, and spin-1 and spin-2 resonances are included coherently through an isobar model. The S-wave component is found to be dominant, followed by the $ρ(770)^0π^+$ and $f_2(1270)π^+$ components. A small contribution from the $ω$(782) → $π^-π^+$ decay is seen for the first time in the $D^+$ → $π^-π^+π^+$ decay.

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DOE OSTI2023

Measurement of the Z boson production cross-section in proton-lead collisions at $\sqrt{s_{\textrm{NN}}}$ = 8.16 TeV

This article presents the first measurement of the differential Z-boson production cross-section in the forward region using proton-lead collisions with the LHCb detector. The dataset was collected at a nucleon-nucleon centre-of-mass energy of $\sqrt{s_{NN}}$ = 8.16 TeV in 2016, corresponding to an integrated luminosity of 30.8 nb –1 . The forward-backward ratio and the nuclear modification factors are measured together with the differential cross-section as functions of the Z boson rapidity in the centre-of-mass frame, the transverse momentum of the Z boson and a geometric variable $\phi$*. The results are in good agreement with the predictions from nuclear parton distribution functions, providing strong constraining power at small Bjorken-x.

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DOE OSTI2023

Impact of cross-section uncertainties on supernova neutrino spectral parameter fitting in the Deep Underground Neutrino Experiment

A primary goal of the upcoming Deep Underground Neutrino Experiment (DUNE) is to measure the 𝒪⁡(10) MeV neutrinos produced by a Galactic core-collapse supernova if one should occur during the lifetime of the experiment. The liquid-argon-based detectors planned for DUNE are expected to be uniquely sensitive to the 𝜈 𝑒 component of the supernova flux, enabling a wide variety of physics and astrophysics measurements. A key requirement for a correct interpretation of these measurements is a good understanding of the energy-dependent total cross section 𝜎⁡(𝐸 𝜈 ) for charged-current 𝜈 𝑒 absorption on argon. In the context of a simulated extraction of supernova 𝜈 𝑒 spectral parameters from a toy analysis, we investigate the impact of 𝜎⁡(𝐸 𝜈 ) modeling uncertainties on DUNE’s supernova neutrino physics sensitivity for the first time. We find that the currently large theoretical uncertainties on 𝜎⁡(𝐸 𝜈 ) must be substantially reduced before the 𝜈𝑒 flux parameters can be extracted reliably; in the absence of external constraints, a measurement of the integrated neutrino luminosity with less than 10% bias with DUNE requires 𝜎⁡(𝐸 𝜈 ) to be known to about 5%. The neutrino spectral shape parameters can be known to better than 10% for a 20% uncertainty on the cross-section scale, although they will be sensitive to uncertainties on the shape of 𝜎⁡(𝐸 𝜈 ). A direct measurement of low-energy 𝜈𝑒-argon scattering would be invaluable for improving the theoretical precision to the needed level.

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