| 1. |
- Aaij, R., et al.
(författare)
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A study of CP violation in the decays B± → [K + K −π+π− ]D h± (h = K, π) and B± → [π+π−π+π− ]D h±
- 2023
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Ingår i: European Physical Journal C. - : Springer Nature. - 1434-6044 .- 1434-6052.
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Tidskriftsartikel (refereegranskat)abstract
- The first study of CP violation in the decay mode B-+/- -> [K+K-pi(+)pi(-)](D)h(+/-), with h = K, pi, is presented, exploiting a data sample of proton-proton collisions collected by the LHCb experiment that corresponds to an integrated luminosity of 9fb(-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 gamma 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-pi(+)pi(-)](D)h(+/-) and B-+/- -> [pi(+)pi(-)pi(+)pi(-)](D)h(+/-) decays.
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| 2. |
- Aaij, R., et al.
(författare)
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Amplitude analysis of B0? : D0Ds+p - and B plus ? D -Ds plus p plus decays
- 2023
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Ingår i: Physical Review D. - : American Physical Society. - 2470-0010 .- 2470-0029. ; 108:1
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Tidskriftsartikel (refereegranskat)abstract
- Resonant contributions in B0 & RARR; over bar D0D+s & pi;- and B+ & RARR; D-D+s & pi;+ 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 Ds & pi; decay channel.
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| 3. |
- Aaij, R., et al.
(författare)
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Amplitude analysis of the ?c+- pK-p+ decay and ?c+ baryon polarization measurement in semileptonic beauty hadron decays
- 2023
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Ingår i: Physical Review D. - : American Physical Society. - 2470-0010 .- 2470-0029. ; 108:1
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Tidskriftsartikel (refereegranskat)abstract
- An amplitude analysis of A+c - pK- & pi;+ decays together with a measurement of the A+c polarization vector in semiOleptonic 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 Ao2000 thorn state are also determined. A significant A+c polarization is found. A large sensitivity of the A+c - pK-& pi;+ decay to the polarization is seen, making the amplitude model suitable for A+c polarization measurements in other systems.
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| 4. |
- Aaij, R., et al.
(författare)
-
Amplitude analysis of the D+-> pi(-)pi(+)pi(+) decay and measurement of the pi(-)pi(+) S-wave amplitude
- 2023
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Ingår i: Journal of High Energy Physics (JHEP). - : Springer. - 1126-6708 .- 1029-8479.
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Tidskriftsartikel (refereegranskat)abstract
- An amplitude analysis of the D+-> (-)pi(+)pi(+) decay is performed with a sample corresponding to 1.5 fb(-1) of integrated luminosity of pp collisions at a centre-of-mass energy root 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 pi(-)pi(+) S-wave amplitude is extracted as a function of pi(-)pi(+) 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 rho(770)(0)pi(+) and f(2)(1270)pi(+) components. A small contribution from the omega(782) -> pi(-)pi(+) decay is seen for the first time in the D+-> pi(-)pi(+)pi(+) decay.
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| 5. |
- Aaij, R., et al.
(författare)
-
Amplitude analysis of the D+s → π-π+π+ decay
- 2023
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Ingår i: Journal of High Energy Physics (JHEP). - : Springer Nature. - 1126-6708 .- 1029-8479. ; :7
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Tidskriftsartikel (refereegranskat)abstract
- A Dalitz plot analysis of the D-s(+) -> pi(-)pi(+)pi(+) decay is presented. The analysis is based on proton-proton collision data recorded by the LHCb experiment at a centre-of-mass energy of 8TeV 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 pi(+)pi(-) 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(+) -> omega(782)pi(+) channel in the D-s(+) -> pi(-)pi(+)pi(+) decay. The resonant structures of the D-s(+) -> pi(-)pi(+)pi(+) and D+ -> pi(-)pi(+)pi(+) decays are compared, providing information about the mechanisms for the hadron formation in these decays.
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| 6. |
- Aaij, R., et al.
(författare)
-
Associated production of prompt J/Ψ and Υ mesons in pp collisions at √ˆšs=13 TeV
- 2023
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Ingår i: Journal of High Energy Physics (JHEP). - : Springer. - 1126-6708 .- 1029-8479.
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Tidskriftsartikel (refereegranskat)abstract
- The associated production of prompt J/psi and (sic) mesons in pp collisions at a centre-of-mass energy of root s = 13TeV is studied using LHCb data, corresponding to an integrated luminosity of 4 fb(-1). The measurement is performed for J/psi (sic) mesons with a transverse momentum pT < 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/psi and (sic)(1S) mesons is measured to be 133 +/- 22 +/- 7 +/- 3 pb, with a significance of 7.9 s, and that of prompt J/psi and (sic)(2S) mesons to be 76 +/- 21 +/- 4 +/- 7 pb, with a significance of 4.9 sigma. The first uncertainty is statistical, the second systematic, and the third due to uncertainties on the used branching fractions. This is the first observation of the associated production of J/psi and (sic)(1S) in proton-proton collisions. Differential cross-sections are measured as functions of variables that are sensitive to kinematic correlations between the J/psi and (sic)(1S) mesons. The effective cross-sections of the associated production of prompt J/psi and (sic) mesons are obtained and found to be compatible with measurements using other particle productions.
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| 7. |
- Aaij, R., et al.
(författare)
-
Charmonium production in pNe collisions at √sNN = 68.5 GeV
- 2023
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Ingår i: European Physical Journal C. - : Springer Nature. - 1434-6044 .- 1434-6052. ; 83:7
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Tidskriftsartikel (refereegranskat)abstract
- The measurement of charmonium states produced in proton-neon ( pNe) collisions by the LHCb experiment in its fixed-target configuration is presented. The production 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 √sNN = 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 ∈ [−2.29, 0] is found to be 506 ± 8 ± 46 nb/nucleon. The ratio of J/ψ and D0 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.
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| 8. |
- Aaij, R., et al.
(författare)
-
Direct CP violation in charmless three-body decays of B± mesons
- 2023
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Ingår i: Physical Review D. - : American Physical Society. - 2470-0010 .- 2470-0029. ; 108
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Tidskriftsartikel (refereegranskat)abstract
- Measurements of CP asymmetries in charmless three-body decays of B-+/- mesons are reported using proton-proton collision data collected by the LHCb detector, corresponding to an integrated luminosity of 5.9 fb(-1). The previously observed CP asymmetry in B-+/- -> pi(K+K-)-K-+/- decays is confirmed, and CP asymmetries are observed with a significance of more than five standard deviations in the B-+/- -> pi(+/-)pi(+)pi and B-+/- -> (KK+K-)-K-+/- decays, while the CP asymmetry of B-+/- -> K-+/-pi(+)pi(-) decays is confirmed to be compatible with zero. The distributions of these asymmetries are also studied as a function of the three-body phase space and suggest contributions from rescattering and resonance interference processes. An indication of the presence of the decays B+ -> pi(+) chi(c0) (1P) in both B+ ->pi(+)pi(+)pi and B+ ->pi+K+K- decays is observed, as is CP violation involving these amplitudes.
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| 9. |
- Aaij, R., et al.
(författare)
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Evidence for Modification of ? Quark Hadronization in High-Multiplicity ?? Collisions at √?=13 TeV
- 2023
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Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 131:6
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Tidskriftsartikel (refereegranskat)abstract
- The production rate of ?0? mesons relative to ?0 mesons is measured by the LHCb experiment in ?? collisions at a center-of-mass energy √?=13 TeV over the forward rapidity interval 2<?<4.5 as a function of the charged particle multiplicity measured in the event. Evidence at the 3.4? level is found for an increase of the ratio of ?0? to ?0 cross sections with multiplicity at transverse momenta below 6 GeV/?, with no significant multiplicity dependence at higher transverse momentum. Comparison with data from ?+?− collisions implies that the density of the hadronic medium may affect the production rates of ? mesons. This is qualitatively consistent with the emergence of quark coalescence as an additional hadronization mechanism in high-multiplicity collisions.
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| 10. |
- Aaij, R., et al.
(författare)
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Evidence for the decays B0 → (*)0ϕ and updated measurements of the branching fractions of the Bs0 → D‾(*)0ϕ decays
- 2023
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Ingår i: Journal of High Energy Physics (JHEP). - : Springer. - 1126-6708 .- 1029-8479. ; :10
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Tidskriftsartikel (refereegranskat)abstract
- Evidence for the decays B-0 -> (D) over bar (0)phi and B-0 -> (D) over bar (*0) phi is reported with a significance of 3.6 sigma and 4.3 sigma, respectively. The analysis employs pp collision data at centre-of-mass energies root s = 7, 8 and 13TeV collected by the LHCb detector and corresponding to an integrated luminosity of 9 fb(-1). The branching fractions are measured to be B(B-0 -> (D) over bar (0)phi) = (7.7 +/- 2.1 +/- 0.7 +/- 0.7) x 10(-7), B(B-0 -> (D) over bar (*0)phi) = (2.2 +/- 05 +/- 0.2 +/- 0.2) x 10(-6). In these results, the first uncertainty is statistical, the second systematic, and the third is related to the branching fraction of the B-0 -> (D) over bar K-0(+) K- decay, used for normalisation. By combining the branching fractions of the decays B-0 -> (D) over bar ((*)0)phi and B-0 -> (D) over bar ((*)0)omega, the omega-phi mixing angle delta is constrained to be tan(2)delta = (3.6 +/- 0.7 +/- 0.4) x 10(-3), where the first uncertainty is statistical and the second systematic. An updated measurement of the branching fractions of the B-s(0) -> (D) over bar ((*)0).phi decays, which can be used to determine the CKM angle gamma, leads to B(B-s(0) -> (D) over bar (0)phi) = (2.30 +/- 0.10 +/- 0.11 +/- 0.20) x 10(-5), B(B-s(0) -> (D) over bar (*0)phi) = (3.17 +/- 0.16 +/- 0.17 +/- 0.27) x 10(-5).
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