The first measurement of the lifetime of the doubly charmed baryon Ξ + + c c is presented, with the signal reconstructed in the final state Λ + c K − π + π + . The data sample used corresponds to an ...integrated luminosity of 1.7 fb − 1 , collected by the LHCb experiment in proton-proton collisions at a center-of-mass energy of 13 TeV. The Ξ + + c c lifetime is measured to be 0.25 6 + 0.024 − 0.022 ( stat ) ± 0.014 ( syst ) ps .
The first measurement of the lifetime of the doubly charmed baryon Ξ + + c c is presented, with the signal reconstructed in the final state Λ + c K − π + π + . The data sample used corresponds to an ...integrated luminosity of 1.7 fb − 1 , collected by the LHCb experiment in proton-proton collisions at a center-of-mass energy of 13 TeV. The Ξ + + c c lifetime is measured to be 0.25 6 + 0.024 − 0.022 ( stat ) ± 0.014 ( syst ) ps .
Searches are performed for both promptlike and long-lived dark photons, A ′ , produced in proton-proton collisions at a center-of-mass energy of 13 TeV, using A ′ → μ + μ − decays and a data sample ...corresponding to an integrated luminosity of 1.6 fb − 1 collected with the LHCb detector. The promptlike A ′ search covers the mass range from near the dimuon threshold up to 70 GeV, while the long-lived A ′ search is restricted to the low-mass region 214 < m ( A ′ ) < 350 MeV . No evidence for a signal is found, and 90% confidence level exclusion limits are placed on the γ - A ′ kinetic-mixing strength. The constraints placed on promptlike dark photons are the most stringent to date for the mass range 10.6 < m ( A ′ ) < 70 GeV , and are comparable to the best existing limits for m ( A ′ ) < 0.5 GeV . The search for long-lived dark photons is the first to achieve sensitivity using a displaced-vertex signature.
Searches are performed for both promptlike and long-lived dark photons, A ′ , produced in proton-proton collisions at a center-of-mass energy of 13 TeV, using A ′ → μ + μ − decays and a data sample ...corresponding to an integrated luminosity of 1.6 fb − 1 collected with the LHCb detector. The promptlike A ′ search covers the mass range from near the dimuon threshold up to 70 GeV, while the long-lived A ′ search is restricted to the low-mass region 214 < m ( A ′ ) < 350 MeV . No evidence for a signal is found, and 90% confidence level exclusion limits are placed on the γ - A ′ kinetic-mixing strength. The constraints placed on promptlike dark photons are the most stringent to date for the mass range 10.6 < m ( A ′ ) < 70 GeV , and are comparable to the best existing limits for m ( A ′ ) < 0.5 GeV . The search for long-lived dark photons is the first to achieve sensitivity using a displaced-vertex signature.
Observation of a New Ξb- Resonance Alfonso Albero, Alejandro; Calvo Gómez, Míriam; Camboni, Alessandro ...
Physical review letters,
08/2018
Journal Article
Recenzirano
Odprti dostop
From samples of p p collision data collected by the LHCb experiment at √ s = 7 , 8 and 13 TeV, corresponding to integrated luminosities of 1.0, 2.0 and 1.5 fb − 1 , respectively, a peak in both ...the Λ 0 b K − and Ξ 0 b π − invariant mass spectra is observed. In the quark model, radially and orbitally excited Ξ − b resonances with quark content b d s are expected. Referring to this peak as Ξ b ( 6227 ) − , the mass and natural width are measured to be m Ξ b ( 6227 ) − = 6226.9 ± 2.0 ± 0.3 ± 0.2 MeV / c 2 and Γ Ξ b ( 6227 ) − = 18.1 ± 5.4 ± 1.8 MeV / c 2 , where the first uncertainty is statistical, the second is systematic, and the third, on m Ξ b ( 6227 ) − , is due to the knowledge of the Λ 0 b baryon mass. Relative production rates of the Ξ b ( 6227 ) − → Λ 0 b K − and Ξ b ( 6227 ) − → Ξ 0 b π − decays are also reported.
Observation of a New Ξb- Resonance Alfonso Albero, Alejandro; Calvo Gómez, Míriam; Camboni, Alessandro ...
Physical review letters,
08/2018
Journal Article
Recenzirano
Odprti dostop
From samples of p p collision data collected by the LHCb experiment at √ s = 7 , 8 and 13 TeV, corresponding to integrated luminosities of 1.0, 2.0 and 1.5 fb − 1 , respectively, a peak in both ...the Λ 0 b K − and Ξ 0 b π − invariant mass spectra is observed. In the quark model, radially and orbitally excited Ξ − b resonances with quark content b d s are expected. Referring to this peak as Ξ b ( 6227 ) − , the mass and natural width are measured to be m Ξ b ( 6227 ) − = 6226.9 ± 2.0 ± 0.3 ± 0.2 MeV / c 2 and Γ Ξ b ( 6227 ) − = 18.1 ± 5.4 ± 1.8 MeV / c 2 , where the first uncertainty is statistical, the second is systematic, and the third, on m Ξ b ( 6227 ) − , is due to the knowledge of the Λ 0 b baryon mass. Relative production rates of the Ξ b ( 6227 ) − → Λ 0 b K − and Ξ b ( 6227 ) − → Ξ 0 b π − decays are also reported.
The time-integrated untagged Dalitz plot of the three-body hadronic charmless decay ¯ B 0 → K 0 S π + π − is studied using a p p collision data sample recorded with the LHCb detector, corresponding ...to an integrated luminosity of 3.0 fb − 1 . The decay amplitude is described with an isobar model. Relative contributions of the isobar amplitudes to the ¯ B 0 → K 0 S π + π − decay branching fraction and C P asymmetries of the flavor-specific amplitudes are measured. The C P asymmetry between the conjugate ¯ B 0 → K ∗ ( 892 ) − π + and B 0 → K ∗ ( 892 ) + π − decay rates is determined to be − 0.308 ± 0.062.
The time-integrated untagged Dalitz plot of the three-body hadronic charmless decay ¯ B 0 → K 0 S π + π − is studied using a p p collision data sample recorded with the LHCb detector, corresponding ...to an integrated luminosity of 3.0 fb − 1 . The decay amplitude is described with an isobar model. Relative contributions of the isobar amplitudes to the ¯ B 0 → K 0 S π + π − decay branching fraction and C P asymmetries of the flavor-specific amplitudes are measured. The C P asymmetry between the conjugate ¯ B 0 → K ∗ ( 892 ) − π + and B 0 → K ∗ ( 892 ) + π − decay rates is determined to be − 0.308 ± 0.062.
Evidence for the Rare Decay Σ+ →pμ+μ Alfonso Albero, Alejandro; Badalov, Alexey; Calvo Gómez, Míriam ...
Physical review letters,
05/2018
Journal Article
Recenzirano
Odprti dostop
A search for the rare decay Σ + → p μ + μ − is performed using p p collision data recorded by the LHCb experiment at center-of-mass energies √ s = 7 and 8 TeV, corresponding to an integrated ...luminosity of 3 fb − 1 . An excess of events is observed with respect to the background expectation, with a signal significance of 4.1 standard deviations. No significant structure is observed in the dimuon invariant mass distribution, in contrast with a previous result from the HyperCP experiment. The measured Σ + → p μ + μ − branching fraction is ( 2.2 + 1.8 − 1.3 ) × 10 − 8 , where statistical and systematic uncertainties are included, which is consistent with the standard model prediction.
Evidence for the Rare Decay Σ+ →pμ+μ Alfonso Albero, Alejandro; Badalov, Alexey; Calvo Gómez, Míriam ...
Physical review letters,
05/2018
Journal Article
Recenzirano
Odprti dostop
A search for the rare decay Σ + → p μ + μ − is performed using p p collision data recorded by the LHCb experiment at center-of-mass energies √ s = 7 and 8 TeV, corresponding to an integrated ...luminosity of 3 fb − 1 . An excess of events is observed with respect to the background expectation, with a signal significance of 4.1 standard deviations. No significant structure is observed in the dimuon invariant mass distribution, in contrast with a previous result from the HyperCP experiment. The measured Σ + → p μ + μ − branching fraction is ( 2.2 + 1.8 − 1.3 ) × 10 − 8 , where statistical and systematic uncertainties are included, which is consistent with the standard model prediction.
