Engineering topics

Bartolini, M. (ORCID:0000000284795802)

Publications and source records attributed to Bartolini, M. (ORCID:0000000284795802).

At least 19 records

DOE OSTI2025

Branching fraction measurement of the decay B + → ψ ( 2 S ) ϕ ( 1020 ) K +

The branching fraction of the decay B + → ψ ( 2 S ) ϕ ( 1020 ) K + , relative to the topologically similar decay B + → J / ψ ϕ ( 1020 ) K + , is measured using proton-proton collision data collected by the LHCb experiment at center-of-mass energies of 7, 8, and 13 TeV, corresponding to an integrated luminosity of 9 fb − 1 . The ratio is found to be 0.061 ± 0.004 ± 0.009 , where the first uncertainty is statistical and the second systematic. Using the world-average branching fraction for B + → J / ψ ϕ ( 1020 ) K + , the branching fraction for the decay B + → ψ ( 2 S ) ϕ ( 1020 ) K + is found to be ( 3.0 ± 0.2 ± 0.5 ± 0.2 ) × 10 − 6 , where the first uncertainty is statistical, the second systematic, and the third is due to the branching fraction of the normalization channel. © 2025 CERN, for the LHCb Collaboration 2025 CERN

Aaij, R. (ORCID:0000000305331952)↗

DOE OSTI2025

Test of Lepton Flavor Universality with B s 0 → ϕ ℓ + ℓ − Decays

Lepton flavor universality in rare b → s transitions is tested for the first time using B s 0 meson decays. The measurements are performed using p p collision data collected by the LHCb experiment between 2011 and 2018, corresponding to a total integrated luminosity of 9 fb − 1 . Branching fraction ratios between the B s 0 → ϕ e + e − and B s 0 → ϕ μ + μ − decays are measured in three regions of dilepton mass squared, q 2 , with 0.1 < q 2 < 1.1 , 1.1 < q 2 < 6.0 , and 15 < q 2 < 19 GeV 2 / c 4 . The results agree with the standard model expectation of lepton flavor universality. © 2025 CERN, for the LHCb Collaboration 2025 CERN

Aaij, R. (ORCID:0000000305331952)↗

DOE OSTI2025

Study of Λ b 0 and Ξ b 0 Decays to Λ h + h ′ − and Evidence for C P Violation in Λ b 0 → Λ K + K − Decays

A study of Λ b 0 and Ξ b 0 decays to Λ h + h ′ − ( h ( ′ ) = π , K ) is performed using p p collision data collected by the LHCb experiment during LHC Runs 1–2, corresponding to an integrated luminosity of 9 fb − 1 . The branching fractions for these decays are measured using the Λ b 0 → Λ c + ( → Λ π + ) π − decay as a control channel. The decays Λ b 0 → Λ π + π − and Ξ b 0 → Λ K − π + are observed for the first time. For decay modes with sufficient signal yields, C P asymmetries are measured in the full and localized regions of the final-state phase space. Evidence is found for C P violation in the Λ b 0 → Λ K + K − decay, interpreted as originating primarily from an asymmetric Λ b 0 → N * + K − decay amplitude. The measured C P asymmetries for other decays are compatible with zero. © 2025 CERN, for the LHCb Collaboration 2025 CERN

Aaij, R. (ORCID:0000000305331952)↗

DOE OSTI2025

Observation of the Open-Charm Tetraquark Candidate T c s 0 * ( 2870 ) 0 in the B − → D − D 0 K S 0 Decay

An amplitude analysis of B − → D − D 0 K 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. A resonant structure of spin-parity 0 + is observed in the D 0 K S 0 invariant-mass spectrum with a significance of 5.3 σ . The mass and width of the state, modeled with a Breit-Wigner line shape, are determined to be 2883 ± 11 ± 8 MeV / c 2 and 87 − 47 + 22 ± 17 MeV , respectively, where the first uncertainties are statistical and the second systematic. These properties and the quark content are consistent with those of the open-charm tetraquark candidate T c s 0 * ( 2870 ) 0 observed previously in the D + K − final state of the B − → D − D + K − decay. This result confirms the existence of the T c s 0 * ( 2870 ) 0 state in a new decay mode. The T c s 1 * ( 2900 ) 0 state, reported in the B − → D − D + K − decay, is also searched for in the D 0 K S 0 invariant-mass spectrum of the B − → D − D 0 K S 0 decay, without finding evidence for it. © 2025 CERN, for the LHCb Collaboration 2025 CERN

Aaij, R. (ORCID:0000000305331952)↗

DOE OSTI2025

Measurement of the Branching Fraction Ratios R ( D + ) and R ( D * + ) Using Muonic τ Decays

The branching fraction ratios of B ¯ 0 → D + τ − ν ¯ τ and B ¯ 0 → D * + τ − ν ¯ τ decays are measured with respect to their muonic counterparts, using a data sample corresponding to an integrated luminosity of 2.0 fb − 1 collected by the LHCb experiment in proton-proton collisions at s = 13 TeV . The reconstructed final states are formed by combining D + mesons with τ − → μ − ν ¯ μ ν τ candidates, where the D + is reconstructed via the D + → K − π + π + decay. The results are R ( D + ) = 0.249 ± 0.043 ± 0.047 , R ( D * + ) = 0.402 ± 0.081 ± 0.085 , where the first uncertainties are statistical and the second systematic. The two measurements have a correlation coefficient of − 0.39 and are compatible with the standard model. © 2025 CERN, for the LHCb Collaboration 2025 CERN

Aaij, R. (ORCID:0000000305331952)↗

DOE OSTI2024

Measurement of Λ b 0 , Λ c + , and Λ Decay Parameters Using Λ b 0 → Λ c + h − Decays

A comprehensive study of the angular distributions in the bottom-baryon decays Λ b 0 → Λ c + h − ( h = π , K ) , followed by Λ c + → Λ h + with Λ → p π − or Λ c + → p K S 0 decays, is performed using a data sample of proton-proton collisions corresponding to an integrated luminosity of 9 fb − 1 collected by the LHCb experiment at center-of-mass energies of 7, 8, and 13 TeV. The decay parameters and the associated charge-parity ( C P ) asymmetries are measured, with no significant C P violation observed. For the first time, the Λ b 0 → Λ c + h − decay parameters are measured. The most precise measurements of the decay parameters α , β , and γ are obtained for Λ c + decays and an independent measurement of the decay parameters for the strange-baryon Λ decay is provided. The results deepen our understanding of weak decay dynamics in baryon decays. © 2024 CERN, for the LHCb Collaboration 2024 CERN

Aaij, R. (ORCID:0000000305331952)↗

DOE OSTI2024

Measurement of C P Violation Observables in D + → K − K + π + Decays

A search for violation of the charge-parity ( C P ) symmetry in the D + → K − K + π + decay is presented, with proton-proton collision data corresponding to an integrated luminosity of 5.4 fb − 1 , collected at a center-of-mass energy of 13 TeV with the LHCb detector. A novel model-independent technique is used to compare the D + and D − phase-space distributions, with instrumental asymmetries subtracted using the D s + → K − K + π + decay as a control channel. The p value for the hypothesis of C P conservation is 8.1%. The C P asymmetry observables A C P | S ϕ π + = ( 0.95 ± 0.4 3 stat ± 0.2 6 syst ) × 10 − 3 and A C P | S K ¯ * 0 K + = ( − 0.26 ± 0.5 6 stat ± 0.1 8 syst ) × 10 − 3 are also measured. These results show no evidence of C P violation and represent the most sensitive search performed through the phase space of a multibody decay. © 2024 CERN, for the LHCb Collaboration 2024 CERN

Aaij, R. (ORCID:0000000305331952)↗

DOE OSTI2024

Measurement of the D * longitudinal polarization in B 0 → D * − τ + ν τ decays

The longitudinal polarization fraction of the D * meson is measured in B 0 → D * − τ + ν τ decays, where the τ lepton decays to three charged pions and a neutrino, using proton-proton collision data collected by the LHCb experiment at center-of-mass energies of 7, 8 and 13 TeV and corresponding to an integrated luminosity of 5 fb − 1 . The D * polarization fraction F L D * is measured in two q 2 regions, below and above 7 GeV 2 / c 4 , where q 2 is defined as the squared invariant mass of the τ ν τ system. The F L D * values are measured to be 0.52 ± 0.07 ± 0.04 and 0.34 ± 0.08 ± 0.02 for the lower and higher q 2 regions, respectively. The first uncertainties are statistical and the second systematic. The average value over the whole q 2 range is F L D * = 0.41 ± 0.06 ± 0.03 . These results are compatible with the Standard Model predictions. © 2024 CERN, for the LHCb Collaboration 2024 CERN

Aaij, R. (ORCID:0000000305331952)↗

DOE OSTI2024

Search for the lepton-flavor violating decay B s 0 → ϕ μ ± τ ∓

A search for the lepton-flavor violating decays B s 0 → ϕ μ ± τ ∓ is presented, using a sample of proton-proton collisions at center-of-mass energies of 7, 8, and 13 TeV, collected with the LHCb detector and corresponding to a total integrated luminosity of 9 fb − 1 . The τ leptons are selected using decays with three charged pions. No significant excess is observed, and an upper limit on the branching fraction is determined to be B ( B s 0 → ϕ μ ± τ ∓ ) < 1.0 × 10 − 5 at 90% confidence level. © 2024 CERN, for the LHCb Collaboration 2024 CERN

Aaij, R. (ORCID:0000000305331952)↗

DOE OSTI2024

Precision measurement of the Ξ b − baryon lifetime

A sample of p p collision data, corresponding to an integrated luminosity of 5.5 fb − 1 and collected by the LHCb experiment during LHC Run 2, is used to measure the ratio of the lifetime of the Ξ b − baryon to that of the Λ b 0 baryon, r τ ≡ τ Ξ b − / τ Λ b 0 . The value r τ = 1.076 ± 0.013 ± 0.006 is obtained, where the first uncertainty is statistical and the second systematic. This value is averaged with the corresponding value from Run 1 to obtain r τ Run 1 , 2 = 1.078 ± 0.012 ± 0.007 . Multiplying by the world-average value of the Λ b 0 lifetime yields τ Ξ b − Run 1 , 2 = 1.578 ± 0.018 ± 0.010 ± 0.011 ps , where the uncertainties are statistical, systematic, and due to the limited knowledge of the Λ b 0 lifetime. This measurement improves the precision of the current world average of the Ξ b − lifetime by about a factor of 2, and is in good agreement with the most recent theoretical predictions. © 2024 CERN, for the LHCb Collaboration 2024 CERN

Aaij, R. (ORCID:0000000305331952)↗

DOE OSTI2024

Observation of New Charmonium or Charmoniumlike States in B + → D * ± D ∓ K + Decays

A study of resonant structures in B + → D * + D − K + and B + → D * − D + K + decays is performed, using proton-proton collision data at center-of-mass energies of s = 7 , 8, and 13 TeV recorded by the LHCb experiment, corresponding to an integrated luminosity of 9 fb − 1 . A simultaneous amplitude fit is performed to the two channels with contributions from resonances decaying to D * − D + and D * + D − states linked by C parity. This procedure allows the C parities of resonances in the D * ± D ∓ mass spectra to be determined. Four charmonium or charmoniumlike states are observed decaying into D * ± D ∓ : η c ( 3945 ) , h c ( 4000 ) , χ c 1 ( 4010 ) , and h c ( 4300 ) , with quantum numbers J P C equal to 0 − + , 1 + − , 1 + + , and 1 + − , respectively. At least three of these states have not been observed previously. In addition, the existence of the T c ¯ s ¯ 0 * ( 2870 ) 0 and T c ¯ s ¯ 1 * ( 2900 ) 0 resonances in the D − K + mass spectrum, already observed in the B + → D + D − K + decay, is confirmed in a different production channel. © 2024 CERN, for the LHCb Collaboration 2024 CERN

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2024

Search for the rare decay of charmed baryon Λ c + into the p μ + μ − final state

A search for the nonresonant Λ c + → p μ + μ − decay is performed using proton-proton collision data recorded at a center-of-mass energy of 13 TeV by the LHCb experiment, corresponding to an integrated luminosity of 5.4 fb − 1 . No evidence for the decay is found in the dimuon invariant-mass regions where the expected contributions of resonances is subdominant. The upper limit on the branching fraction of the Λ c + → p μ + μ − decay is determined to be 2.9 ( 3.2 ) × 10 − 8 at 90 % ( 95 % ) confidence level. The branching fractions in the dimuon invariant-mass regions dominated by the η , ρ and ω resonances are also determined. © 2024 CERN, for the LHCb Collaboration 2024 CERN

Aaij, R. (ORCID:0000000305331952)↗

DOE OSTI2024

Search for Time-Dependent C P Violation in D 0 → π + π − π 0 Decays

A measurement of time-dependent C P violation in D 0 → π + π − π 0 decays using a p p collision data sample collected by the LHCb experiment in 2012 and from 2015 to 2018, corresponding to an integrated luminosity of 7.7 fb − 1 , is presented. The initial flavor of each D 0 candidate is determined from the charge of the pion produced in the D * ( 2010 ) + → D 0 π + decay. The decay D 0 → K − π + π 0 is used as a control channel to validate the measurement procedure. The gradient of the time-dependent C P asymmetry Δ Y in D 0 → π + π − π 0 decays is measured to be Δ Y = ( − 1.3 ± 6.3 ± 2.4 ) × 10 − 4 , where the first uncertainty is statistical and the second is systematic, which is compatible with C P conservation. © 2024 CERN, for the LHCb Collaboration 2024 CERN

Aaij, R. (ORCID:0000000305331952)↗

DOE OSTI2024

First observation of Λ b 0 → Σ c ( * ) + + D ( * ) − K − decays

The four decays, Λ b 0 → Σ c ( * ) + + D ( * ) − K − , are observed for the first time using proton-proton collision data collected with the LHCb detector at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 6 fb − 1 . By considering the Λ b 0 → Λ c + D ¯ 0 K − decay as reference channel, the following branching fraction ratios are measured to be B ( Λ b 0 → Σ c + + D − K − ) B ( Λ b 0 → Λ c + D ¯ 0 K − ) = 0.282 ± 0.016 ± 0.016 ± 0.005 , B ( Λ b 0 → Σ c * + + D − K − ) B ( Λ b 0 → Σ c + + D − K − ) = 0.460 ± 0.052 ± 0.028 , B ( Λ b 0 → Σ c + + D * − K − ) B ( Λ b 0 → Σ c + + D − K − ) = 2.261 ± 0.202 ± 0.129 ± 0.046 , B ( Λ b 0 → Σ c * + + D * − K − ) B ( Λ b 0 → Σ c + + D − K − ) = 0.896 ± 0.137 ± 0.066 ± 0.018 , where the first uncertainties are statistical, the second are systematic, and the third are due to uncertainties in the branching fractions of intermediate particle decays. These initial observations mark the beginning of pentaquark searches in these modes, with more datasets to become available following the LHCb upgrade. © 2024 CERN, for the LHCb Collaboration 2024 CERN

Aaij, R. (ORCID:0000000305331952)↗

DOE OSTI2024

Observation of strangeness enhancement with charmed mesons in high-multiplicity p Pb collisions at s NN = 8.16 TeV

The production of prompt D s + and D + mesons is measured by the LHCb experiment in proton-lead ( p Pb ) collisions in both the forward ( 1.5 < y * < 4.0 ) and backward ( − 5.0 < y * < − 2.5 ) rapidity regions at a nucleon-nucleon center-of-mass energy of s NN = 8.16 TeV . The nuclear modification factors of both D s + and D + mesons are determined as a function of transverse momentum, p T , and rapidity. In addition, the D s + to D + cross section ratio is measured as a function of the primary charged particle multiplicity in the event. An enhanced D s + to D + production in high-multiplicity events is observed for the whole measured p T range, in particular at low p T and backward rapidity, where the significance exceeds six standard deviations. This constitutes the first observation of strangeness enhancement in charm quark hadronization in high-multiplicity p Pb collisions. The results are also qualitatively consistent with the presence of quark coalescence as an additional charm quark hadronization mechanism in high-multiplicity proton-lead collisions. © 2024 CERN, for the LHCb Collaboration 2024 CERN

Aaij, R. (ORCID:0000000305331952)↗

DOE OSTI2024

Search for prompt production of pentaquarks in charm hadron final states

A search for hidden-charm pentaquark states decaying to a range of Σ c D ¯ and Λ c + D ¯ final states, as well as doubly charmed pentaquark states to Σ c D and Λ c + D , is made using samples of proton-proton collision data corresponding to an integrated luminosity of 5.7 fb − 1 recorded by the LHCb detector at s = 13 TeV . Since no significant signals are found, upper limits are set on the pentaquark yields relative to that of the Λ c + baryon in the Λ c + → p K − π + decay mode. The known pentaquark states are also investigated, and their signal yields are found to be consistent with zero in all cases. © 2024 CERN, for the LHCb Collaboration 2024 CERN

Aaij, R. (ORCID:0000000305331952)↗

DOE OSTI2024

Modification of χ c 1 ( 3872 ) and ψ ( 2 S ) Production in p Pb Collisions at s NN = 8.16 TeV

The LHCb Collaboration measures production of the exotic hadron χ c 1 ( 3872 ) in proton-nucleus collisions for the first time. Comparison with the charmonium state ψ ( 2 S ) suggests that the exotic χ c 1 ( 3872 ) experiences different dynamics in the nuclear medium than conventional hadrons, and comparison with data from proton-proton collisions indicates that the presence of the nucleus may modify χ c 1 ( 3872 ) production rates. This is the first measurement of the nuclear modification factor of an exotic hadron. © 2024 CERN, for the LHCb Collaboration 2024 CERN

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2024

Measurement of forward charged hadron flow harmonics in peripheral PbPb collisions at s N N = 5.02 TeV with the LHCb detector

Flow harmonic coefficients, v n , which are the key to studying the hydrodynamics of the quark-gluon plasma (QGP) created in heavy-ion collisions, have been measured in various collision systems and kinematic regions and using various particle species. The study of flow harmonics in a wide pseudorapidity range is particularly valuable to understand the temperature dependence of the shear viscosity to entropy density ratio of the QGP. This paper presents the first LHCb results of the second- and the third-order flow harmonic coefficients of charged hadrons as a function of transverse momentum in the forward region, corresponding to pseudorapidities between 2.0 and 4.9, using the data collected from PbPb collisions in 2018 at a center-of-mass energy of 5.02 TeV . The coefficients measured using the two-particle angular correlation analysis method are smaller than the central-pseudorapidity measurements at ALICE and ATLAS from the same collision system but share similar features. ©2024 CERN, for the LHCb Collaboration 2024 CERN

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗