Engineering topics

Aaij, R.

Publications and source records attributed to Aaij, R..

At least 37 records · Page 2

DOE OSTI2023

Amplitude analysis of the Λ c + → p K - π + decay and Λ c + baryon polarization measurement in semileptonic beauty hadron decays

An amplitude analysis of Λ c + → p K - π + decays together with a measurement of the Λ c + polarization vector in semiōleptonic beauty hadron decays is presented. A sample of 400 000 candidates is selected from proton-proton collisions recorded by the LHCb detector at a center-of-mass energy of 13 TeV. An amplitude model is developed and the resonance fractions as well as two- and three-body decay parameters are reported. The mass and width of the $Λ$(2000) state are also determined. A significant Λ c + polarization is found. A large sensitivity of the Λ c + → p K - π + decay to the polarization is seen, making the amplitude model suitable for Λ c + polarization measurements in other systems.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2023

Amplitude analysis of B 0 → D ¯ 0 D s + π - and B + → D - D s + π + decays

Resonant contributions in B 0 → D ¯ 0 D s + π - and B + → D - D s + π + decays are determined with an amplitude analysis, which is performed both separately and simultaneously, where in the latter case isospin symmetry between the decays is assumed. The analysis is based on data collected by the LHCb detector in proton-proton collisions at center-of-mass energies of 7, 8, and 13 TeV. The full data sample corresponds to an integrated luminosity of 9 fb -1 . A doubly charged spin-0 open-charm tetraquark candidate together with a neutral partner, both with masses near 2.9 GeV, are observed in the $D_sπ$ decay channel.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2023

Study of the B - → Λ c + Λ ¯ c - K - decay

The decay B - → $Λ^+_c \overline{Λ}^-_c K^-$ is studied in proton-proton collisions at a center-of-mass energy of $\sqrt{s}$ = 13 TeV using data corresponding to an integrated luminosity of 5 fb -1 collected by the LHCb experiment. In the $Λ^+_c K^-$ system, the Ξ c (2930) 0 state observed at the BABAR and Belle experiments is resolved into two narrower states, Ξ c (2923) 0 and Ξ c (2939) 0 , whose masses and widths are measured to be m(Ξ c (2923) 0 ) = 2924.5 ± 0.4 ± 1.1 MeV, m(Ξ c (2939) 0 ) = 2938.5 ± 0.9 ± 2.3 MeV, Γ(Ξ c (2923) 0 ) = 4.8 ± 0.9 ± 1.5 MeV, Γ(Ξ c (2939) 0 ) = 11.0 ± 1.9 ± 7.5 MeV, where the first uncertainties are statistical and the second systematic. The results are consistent with a previous LHCb measurement using a prompt $Λ^+_c K^-$ sample. Evidence of a new Ξ c (2880) 0 state is found with a local significance of 3.8σ, whose mass and width are measured to be 2881.8 ± 3.1 ± 8.5 MeV and 12.4 ± 5.3 ± 5.8 MeV, respectively. In addition, evidence of a new decay mode Ξ c (2790) 0 → $Λ^+_c K^-$ is found with a significance of 3.7σ. The relative branching fraction of B - → $Λ^+_c \overline{Λ}^-_c K^-$ with respect to the B - → D + D - K - decay is measured to be 2.36 ± 0.11 0.22 ± 0.25, where the first uncertainty is statistical, the second systematic and the third originates from the branching fractions of charm hadron decays.

79 ASTRONOMY AND ASTROPHYSICS↗

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.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

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.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

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.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2023

Charmonium production in $p$Ne collisions at $\sqrt{s_{\scriptscriptstyle \text {NN}}} =68.5$ GeV

The measurement of charmonium states produced in proton-neon (pNe) collisions by the LHCb experiment in its fixed-target configuration is presented. The pro duction of J/ψ and ψ(2S) mesons is studied with a beam of 2.5 TeV protons colliding on gaseous neon targets at rest, corresponding to a nucleon-nucleon centre-of-mass energy $\sqrt{s_{NN}}$ = 68.5 GeV. The data sample corresponds to an integrated luminosity of 21.7 ± 1.4 nb -1 . The J/ψ and ψ(2S) hadrons are reconstructed in μ + μ - final states. The J/ψ production cross-section per target nucleon in the centre-of mass rapidity range y* ϵ [-2.29, 0] is found to be 506 ± 8 ± 46 nb/nucleon. The ratio of J/ψ and D 0 cross-sections is evaluated to (1.06 ± 0.02 ± 0.09)%. The ψ(2S) to J/ψ relative production rate is found to be (1.67 ± 0.27 ± 0.10)% in good agreement with other measurements involving beam and target nuclei of similar sizes.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

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.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

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.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

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.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

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.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

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.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2023

A study of $CP$ violation in the decays $B^±$ → [$K^+ K^-π^+π^-$]$_Dh^±$ ($h$ = $K, π$) and $B^±$ → [$π^+π^-π^+π^-$]$_Dh^±$

The first study of CP violation in the decay mode $B^±$ → [$K^+ K^-π^+π^-$]$_Dh^±$, with $h$ = $K, π$, is presented, exploiting a data sample of proton–proton collisions collected by the LHCb experiment that corresponds to an integrated luminosity of 9 fb -1 . The analysis is performed in bins of phase space, which are optimised for sensitivity to local CP asymmetries. CP-violating observables that are sensitive to the angle γ of the Unitarity Triangle are determined. The analysis requires external information on charm-decay parameters, which are currently taken from an amplitude analysis of LHCb data, but can be updated in the future when direct measurements become available. Measurements are also performed of phase-space integrated observables for $B^±$ → [$K^+ K^-π^+π^-$]$_Dh^±$ and $B^±$ → [$π^+π^-π^+π^-$]$_Dh^±$ decays.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

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.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

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.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

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.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

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.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

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.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗