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Echocardiographic changes in anorexia nervosa: a pathophysiological adaptation or a disease? Intern Emerg Med 2022; 17:777-787. [PMID: 34677790 DOI: 10.1007/s11739-021-02871-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Accepted: 10/12/2021] [Indexed: 11/25/2022]
Abstract
Anorexia Nervosa is one of the most common form of eating disorders. Cardiac involvement occurs in approximately 80% of patients. Few reports focused on the association between body weight fluctuations and echocardiographic abnormalities, considering linear measurements. We describe echocardiographic and clinical features among male and female patients with anorexia nervosa and the effect of weight gain on these parameters. We performed a single center, retrospective study of patients followed at a dedicated multidisciplinary Unit. The study population consisted of 81 patients, mean age 25 ± 11 years, 94% female. Median body mass index was 14.4 kg/m2 (25th-75th percentile 12.7-15.6 kg/m2). Patients with body mass index below the median value had more often pericardial effusion, smaller left ventricular mass and left ventricular end-diastolic volume and thinner interventricular septum. However, when indexed to body surface area, left ventricular mass and volumes were within the normal range in 90% of population. Patients with pericardial effusion showed mitral valve abnormalities and lower values of white blood cells and platelets, although within normal limits. Presence of pericardial effusion was not related to inflammatory parameters or low plasma protein levels. In 39 patients who displayed weight gain during a median follow-up of 189 days (25th-75th percentile 47-471), increased left ventricular mass, interventricular septum thickness, white blood cells and platelet count and decreased pericardial effusion were observed. Patients with anorexia nervosa have a specific echocardiographic pattern which seems to be proportional to the body size, suggesting a pathophysiological adaptation to the lack of substrates.
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Different COVID19 pandemic phases & STEMI: experience from an Italian hub centre. Eur Heart J 2021. [PMCID: PMC8767583 DOI: 10.1093/eurheartj/ehab724.1356] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Abstract
Introduction and methods
During Coronavirus disease 2019 (COVID-19) pandemic a reduction in ST-elevation acute myocardial infarction with an increase in in-hospital mortality has been observed. In our region the pandemic temporal trend was sinusoidal with peaks and valleys. A first outbreak (phase-peak 1 “P-P1”) was in March 2020 (248.12 cases for 100,000 inhabitants), a reduction (phase-valley 1 “P-V1”) in May 2020 (16.68 cases for 100,000 inhabitants) and a second outbreak (phase-peak 2 “P-P2”) in November 2020 (540.17 cases for 100,000 inhabitants; data from Italian Health Ministry). Our hospital was reorganized as one of the 13 Macro-Hubs identified in Lombardy for the treatment of STEMI. Here we describe our experience in the treatment of STEMI patients in the three different phases of COVID-19 pandemic.
Results
In the three different phases the groups were superimposable for mean characteristics, but they differ for COVID-19 infection incidence (table). At multivariate analysis for the entire population COVID-19 infection (OR 45.8 [95% CI] 1.39–1511.79; p=0.03) was the only independent predictor of in-hospital mortality. Focusing on COVID-19 patients (figure) they experienced a 5-time increased incidence of in-hospital mortality (COVID-19pos vs COVID-19neg, 50% vs 11.1%; p=0.02). Moreover, the compresence of COVID-19 infection induced an 8 times increased risk of death (OR 8; [95% CI] 1.85–34.60; p=0.005) determined by a higher incidence respiratory complications (COVID-19pos vs COVID-19neg, 33.3% vs 8.9%; p=0.03) with a similar incidence of cardiac death (COVID-19pos vs COVID-19neg, 16.7% vs 11.17%; p=0.60).
Conclusions
In conclusion our data suggest the crucial necessity of an early and precise diagnosis of COVID-19 infection in STEMI to establish a correct management of this very high risk patients.
Funding Acknowledgement
Type of funding sources: None. STEMI mortality in COVID+ vs COVID−
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Sacubitril/Valsartan in heart failure with reduced ejection fraction: clinical and echocardiographic insights from a real world population. Eur Heart J 2021. [DOI: 10.1093/eurheartj/ehab724.0785] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Abstract
Background
Following the PARADIGM trial, some studies have identified cardiac remodeling as major background for hard end point benefits of Sacubitril/Valsartan (S/V), but few adopted a well described definition in the literature.
Purpose
We aimed at a comprehensive evaluation of the effects of S/V on echo-derived measures of cardiac remodeling along with clinical and laboratory data over a medium-term follow-up pointing to a real-world HFrEF population.
Methods
This is a prospective observational study of HFrEF patients on optimal medical therapy (OMT) initiated with S/V at Heart Failure Clinic of our institute (January 2017-January 2020). In 62 HFrEF, echocardiographic, laboratory and clinical data were collected at baseline and over 10 (Q1-Q3 8–13) months after S/V initiation. Mean age was 68±12 years, 79% men. Left ventricular reverse remodeling (LVRR) was defined as: 1) an absolute increase in LVEF ≥10 points or a LVEF ≥50% at follow-up and 2) a relative decrease in indexed left ventricular end-diastolic diameter of at least 10% or an indexed left ventricular end-diastolic diameter ≤33 mm/m2.
Results
Compared to baseline, S/V promoted a significant improvement of LV ejection fraction (LVEF, from 30% to 37%; p<0,0001) with an absolute median increase in LVEF of 8 points. Parallel significant reductions in left ventricular and atrial volumes, lower mitral regurgitation degree and a better diastolic dysfunction along with clinical improvement (NYHA class and NT-proBNP values) were observed at follow up. sPAP (systolic Pulmonary Arterial Pressure) was significantly decreased at follow-up evaluation (37 mmHg vs 31 mmHg p=0,005) (Table 1). Overall, LVRR as defined above was observed in 30% of patients. Younger age (64 vs 74 years, p=0,007), a shorter duration of the disease (7 vs 23 months, p=0,009), and non ischaemic etiology (79% vs 33% p=0,003), along with a smaller baseline LAESVi (Left Atrial End Systolic Volume, 41 vs 48 ml/m2 p=0,012) were more common in patients with LVRR. sPAP and Right Ventricular (RV) function estimated by tricuspid annular plane systolic excursion (TAPSE) were significantly better in LVRR patients along with TAPSE/sPAP ratio (Table 2).
Conclusions
Our data point to a remarkable medium-term reverse remodeling effect by S/V in HFrEF. Findings reinforce the concept that the main benefits of S/V on hard end-points are mediated by its cardiac-related effects. Both a left and right reverse remodeling occur in HFrEF patients who start S/V in the most adaptable phase of the disease supporting an early administration.
Funding Acknowledgement
Type of funding sources: None.
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Consequences on the right ventricular to pulmonary circulation coupling of COVID-19 infection. Eur Heart J 2021. [DOI: 10.1093/eurheartj/ehab724.0149] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Abstract
Background
Right Ventricular (RV) dysfunction and pulmonary hypertension (PH) are two very likely acute and long term targets of COVID-19 pneumonia, with a potential prognostic implications.
Purpose
To determine the COVID-19 pneumonia effects on the right ventricular to pulmonary circulation coupling through bedside echocardiography and extend its implications to prognostic assessment.
Methods
Single-centre study including consecutive subjects hospitalized for COVID-19 pneumonia who underwent a clinical indicated echocardiogram between March 2020 and December 2020. Extensive analysis of cardiac function was performed offline by an operator blinded to clinical data, laboratory findings and CT scans.
Results
133 patients were enrolled (mean age 69±12 years, 57% men), 38% of whom already had cardiac disease in their medical history. In-hospital mortality was 26% (35 pts), during a mean hospital stay of 26±16 days. Non survivors had higher pulmonary artery systolic pressure (PASP) and worse RV function, assessed with both standard parameters (i.e. TAPSE) and with the novel speckle tracking analysis by RV-Global Longitudinal Strain (RV-GLS) and RV-Free Wall Longitudinal Strain (RV-FWLS). The combination of these two variables in TAPSE/PASP ratio allows assessment of RV to pulmonary circulation (Pc) coupling and was strongly associated with in-hospital death (HR 0.73, 95% CI 0.59–0.89, p=0.003) and patients with TAPSE/PASP<0.57 mm/mmHg had a more than 4-fold increased risk of in-hospital death (HR 4.8, 95% CI 1.7–13.1, p=0.003). In patients where speckle tracking analysis was feasible, we examined RV-GLS/PASP and RV-FWLS/PASP and found that it was associated with in-hospital mortality. The best cut-offs for predicting in-hospital mortality was 0.51 for RV-GLS/PASP (94% sensitivity and 59% specificity) and 0.49 for RV-free wall LS (87% sensitivity and 70% specificity). At the multivariable analysis RV to Pc remained associated with in-hospital death after adjustments for age, PaO2/FiO2, LVEF, and severity of lung involvement at the CT.
Conclusions
Either PH and RV dysfunction predict in-hospital mortality in patients with COVID-19 pneumonia. The assessment of RV to Pc coupling, however, better describes the adaptive RV response to increased PASP and gives additional prognostic information in a population with a relevant prevalence of comorbidities.
Funding Acknowledgement
Type of funding sources: None.
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Echocardographic changes in anorexia nervosa: a pathophysiological adaptation or a disease? Eur Heart J Cardiovasc Imaging 2021. [DOI: 10.1093/ehjci/jeaa356.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Abstract
Funding Acknowledgements
Type of funding sources: None.
Background
Anorexia nervosa (AN) is one of the most common form of eating disorders and it is a severe and potentially fatal disease with high rates of morbidity and mortality especially in the population aged 15-25 years. Cardiac involvement occurs in approximately 80% of patients with AN. Cardiovascular complications include changes in the autonomic regulation (increased vagal tone, bradycardia, orthostatic hypotension, syncope), arrhythmias, congestive heart failure and sudden death. Few reports have described, in small series, a variety of echocardiographic abnormalities including decreased cardiac mass, mitral valve prolapse, pericardial effusion and reduced left ventricular (LV) dimensions. No previous studies, however, examined if there is a change in these abnormalities with weight fluctuations.
Purpose
To describe echocardiographic findings among male and female patients with AN and to examine the effect of weight gain on clinical and echocardiographic parameters.
Methods
We performed a single center, retrospective, study of patients diagnosed with AN using the diagnostic and statistical manual of mental disorders, fifth edition (DSM-5). Clinical, laboratory and ECG-graphic data were obtained by reviewing each patient’s medical records. Echocardiographic parameters were measured off-line.
Results
The study population consisted of 81 patients, mean age 24.5 ± 11.6 years, 92.6% females. 75% showed an extreme AN degree. Mean body mass index (BMI) was 15.2 ± 2.1 kg/m2. Mean heart rate was 57.2 ± 12.7 beats per minute. Some patients showed right bundle branch block (7.4%) or prolonged QT interval (14.8%). Patients with BMI below the mean value had more often pericardial effusion, smaller LV mass and LV end-diastolic volume and thinner interventricular septum (all p < 0.05). However, when index to BSA, LV mass and volumes were within normal range in the 90% of the population. They also showed mitral valve abnormalities and low values of white blood cells and platelets. The presence of pericardial effusion was not related to inflammatory parameters or protein deficiency. For 39 patients echocardiographic exams at the highest and the lowest weight were available. With weight gain, there was an improvement in LV mass, interventricular septum thickness, pericardial effusion and an increase in white blood cells and platelet count.
Conclusions
Our study showed that patients with AN have a specific echocardiographic pattern which seems to be proportional to the body size, suggesting a pathophysiological adaptation to the lack of substrates, hypothesis confirmed by the regression with weight gain. It is possible that pericardic effusion fills the gap left by mass loss.
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Amplitude Analysis of the Decay B[over ¯]^{0}→K_{S}^{0}π^{+}π^{-} and First Observation of the CP Asymmetry in B[over ¯]^{0}→K^{*}(892)^{-}π^{+}. PHYSICAL REVIEW LETTERS 2018; 120:261801. [PMID: 30004725 DOI: 10.1103/physrevlett.120.261801] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2018] [Revised: 03/15/2018] [Indexed: 06/08/2023]
Abstract
The time-integrated untagged Dalitz plot of the three-body hadronic charmless decay B[over ¯]^{0}→K_{S}^{0}π^{+}π^{-} is studied using a pp 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[over ¯]^{0}→K_{S}^{0}π^{+}π^{-} decay branching fraction and CP asymmetries of the flavor-specific amplitudes are measured. The CP asymmetry between the conjugate B[over ¯]^{0}→K^{*}(892)^{-}π^{+} and B^{0}→K^{*}(892)^{+}π^{-} decay rates is determined to be -0.308±0.062.
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Measurement of the Ratio of the B^{0}→D^{*-}τ^{+}ν_{τ} and B^{0}→D^{*-}μ^{+}ν_{μ} Branching Fractions Using Three-Prong τ-Lepton Decays. PHYSICAL REVIEW LETTERS 2018; 120:171802. [PMID: 29756810 DOI: 10.1103/physrevlett.120.171802] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Revised: 03/05/2018] [Indexed: 06/08/2023]
Abstract
The ratio of branching fractions R(D^{*-})≡B(B^{0}→D^{*-}τ^{+}ν_{τ})/B(B^{0}→D^{*-}μ^{+}ν_{μ}) is measured using a data sample of proton-proton collisions collected with the LHCb detector at center-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3 fb^{-1}. For the first time, R(D^{*-}) is determined using the τ-lepton decays with three charged pions in the final state. The B^{0}→D^{*-}τ^{+}ν_{τ} yield is normalized to that of the B^{0}→D^{*-}π^{+}π^{-}π^{+} mode, providing a measurement of B(B^{0}→D^{*-}τ^{+}ν_{τ})/B(B^{0}→D^{*-}π^{+}π^{-}π^{+})=1.97±0.13±0.18, where the first uncertainty is statistical and the second systematic. The value of B(B^{0}→D^{*-}τ^{+}ν_{τ})=(1.42±0.094±0.129±0.054)% is obtained, where the third uncertainty is due to the limited knowledge of the branching fraction of the normalization mode. Using the well-measured branching fraction of the B^{0}→D^{*-}μ^{+}ν_{μ} decay, a value of R(D^{*-})=0.291±0.019±0.026±0.013 is established, where the third uncertainty is due to the limited knowledge of the branching fractions of the normalization and B^{0}→D^{*-}μ^{+}ν_{μ} modes. This measurement is in agreement with the standard model prediction and with previous results.
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Measurement of the Ratio of Branching Fractions B(B_{c}^{+}→J/ψτ^{+}ν_{τ})/B(B_{c}^{+}→J/ψμ^{+}ν_{μ}). PHYSICAL REVIEW LETTERS 2018; 120:121801. [PMID: 29694106 DOI: 10.1103/physrevlett.120.121801] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2017] [Revised: 01/19/2018] [Indexed: 06/08/2023]
Abstract
A measurement is reported of the ratio of branching fractions R(J/ψ)=B(B_{c}^{+}→J/ψτ^{+}ν_{τ})/B(B_{c}^{+}→J/ψμ^{+}ν_{μ}), where the τ^{+} lepton is identified in the decay mode τ^{+}→μ^{+}ν_{μ}ν[over ¯]_{τ}. This analysis uses a sample of proton-proton collision data corresponding to 3.0 fb^{-1} of integrated luminosity recorded with the LHCb experiment at center-of-mass energies of 7 and 8 TeV. A signal is found for the decay B_{c}^{+}→J/ψτ^{+}ν_{τ} at a significance of 3 standard deviations corrected for systematic uncertainty, and the ratio of the branching fractions is measured to be R(J/ψ)=0.71±0.17(stat)±0.18(syst). This result lies within 2 standard deviations above the range of central values currently predicted by the standard model.
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Search for Dark Photons Produced in 13 TeV pp Collisions. PHYSICAL REVIEW LETTERS 2018; 120:061801. [PMID: 29481252 DOI: 10.1103/physrevlett.120.061801] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2017] [Indexed: 06/08/2023]
Abstract
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.
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First Observation of the Rare Purely Baryonic Decay B^{0}→pp[over ¯]. PHYSICAL REVIEW LETTERS 2017; 119:232001. [PMID: 29286678 DOI: 10.1103/physrevlett.119.232001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2017] [Indexed: 06/07/2023]
Abstract
The first observation of the decay of a B^{0} meson to a purely baryonic final state, B^{0}→pp[over ¯], is reported. The proton-proton collision data sample used was collected with the LHCb experiment at center-of-mass energies of 7 and 8 TeV and corresponds to an integrated luminosity of 3.0 fb^{-1}. The branching fraction is determined to be B(B^{0}→pp[over ¯])=(1.25±0.27±0.18)×10^{-8}, where the first uncertainty is statistical and the second systematic. The decay mode B^{0}→pp[over ¯] is the rarest decay of the B^{0} meson observed to date. The decay B_{s}^{0}→pp[over ¯] is also investigated. No signal is seen and the upper limit B(B_{s}^{0}→pp[over ¯])<1.5×10^{-8} at 90% confidence level is set on the branching fraction.
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χ_{c1} and χ_{c2} Resonance Parameters with the Decays χ_{c1,c2}→J/ψμ^{+}μ^{-}. PHYSICAL REVIEW LETTERS 2017; 119:221801. [PMID: 29286773 DOI: 10.1103/physrevlett.119.221801] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2017] [Indexed: 06/07/2023]
Abstract
The decays χ_{c1}→J/ψμ^{+}μ^{-} and χ_{c2}→J/ψμ^{+}μ^{-} are observed and used to study the resonance parameters of the χ_{c1} and χ_{c2} mesons. The masses of these states are measured to be m(χ_{c1})=3510.71±0.04(stat)±0.09(syst) MeV and m(χ_{c2})=3556.10±0.06(stat)±0.11(syst) MeV, where the knowledge of the momentum scale for charged particles dominates the systematic uncertainty. The momentum-scale uncertainties largely cancel in the mass difference m(χ_{c2})-m(χ_{c1})=45.39±0.07(stat)±0.03(syst) MeV. The natural width of the χ_{c2} meson is measured to be Γ(χ_{c2})=2.10±0.20(stat)±0.02(syst) MeV. These results are in good agreement with and have comparable precision to the current world averages.
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Updated search for long-lived particles decaying to jet pairs. THE EUROPEAN PHYSICAL JOURNAL. C, PARTICLES AND FIELDS 2017; 77:812. [PMID: 31997934 PMCID: PMC6956870 DOI: 10.1140/epjc/s10052-017-5178-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/23/2017] [Accepted: 08/31/2017] [Indexed: 06/10/2023]
Abstract
A search is presented for long-lived particles with a mass between 25 and 50 GeV / c 2 and a lifetime between 2 and 500 ps, using proton-proton collision data corresponding to an integrated luminosity of 2.0 fb - 1 , collected by the LHCb detector at centre-of-mass energies of 7 and 8 TeV. The particles are assumed to be pair-produced in the decay of a 125 GeV / c 2 Standard-Model-like Higgs boson. The experimental signature is a single long-lived particle, identified by a displaced vertex with two associated jets. No excess above background is observed and limits are set on the production cross-section as a function of the mass and lifetime of the long-lived particle.
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Observation of D^{0} Meson Decays to π^{+}π^{-}μ^{+}μ^{-} and K^{+}K^{-}μ^{+}μ^{-} Final States. PHYSICAL REVIEW LETTERS 2017; 119:181805. [PMID: 29219589 DOI: 10.1103/physrevlett.119.181805] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2017] [Indexed: 06/07/2023]
Abstract
The first observation of the D^{0}→π^{+}π^{-}μ^{+}μ^{-} and D^{0}→K^{+}K^{-}μ^{+}μ^{-} decays is reported using a sample of proton-proton collisions collected by LHCb at a center-of-mass energy of 8 TeV, and corresponding to 2 fb^{-1} of integrated luminosity. The corresponding branching fractions are measured using as normalization the decay D^{0}→K^{-}π^{+}[μ^{+}μ^{-}]_{ρ^{0}/ω}, where the two muons are consistent with coming from the decay of a ρ^{0} or ω meson. The results are B(D^{0}→π^{+}π^{-}μ^{+}μ^{-})=(9.64±0.48±0.51±0.97)×10^{-7} and B(D^{0}→K^{+}K^{-}μ^{+}μ^{-})=(1.54±0.27±0.09±0.16)×10^{-7}, where the uncertainties are statistical, systematic, and due to the limited knowledge of the normalization branching fraction. The dependence of the branching fraction on the dimuon mass is also investigated.
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Search for Baryon-Number Violating Ξ_{b}^{0} Oscillations. PHYSICAL REVIEW LETTERS 2017; 119:181807. [PMID: 29219549 DOI: 10.1103/physrevlett.119.181807] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2017] [Indexed: 06/07/2023]
Abstract
A search for baryon-number violating Ξ_{b}^{0} oscillations is performed with a sample of pp collision data recorded by the LHCb experiment, corresponding to an integrated luminosity of 3 fb^{-1}. The baryon number at the moment of production is identified by requiring that the Ξ_{b}^{0} come from the decay of a resonance Ξ_{b}^{*-}→Ξ_{b}^{0}π^{-} or Ξ_{b}^{'-}→Ξ_{b}^{0}π^{-}, and the baryon number at the moment of decay is identified from the final state using the decays Ξ_{b}^{0}→Ξ_{c}^{+}π^{-},Ξ_{c}^{+}→pK^{-}π^{+}. No evidence of baryon-number violation is found, and an upper limit at the 95% confidence level is set on the oscillation rate of ω<0.08 ps^{-1}, where ω is the associated angular frequency.
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Improved limit on the branching fraction of the rare decay K S 0 → μ + μ - . THE EUROPEAN PHYSICAL JOURNAL. C, PARTICLES AND FIELDS 2017; 77:678. [PMID: 31997922 PMCID: PMC6956924 DOI: 10.1140/epjc/s10052-017-5230-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/12/2017] [Accepted: 09/18/2017] [Indexed: 06/10/2023]
Abstract
A search for the decay K S 0 → μ + μ - is performed, based on a data sample of proton-proton collisions corresponding to an integrated luminosity of 3 fb - 1 , collected by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV . The observed yield is consistent with the background-only hypothesis, yielding a limit on the branching fraction of B ( K S 0 → μ + μ - ) < 0.8 ( 1.0 ) × 10 - 9 at 90 % ( 95 % ) confidence level. This result improves the previous upper limit on the branching fraction by an order of magnitude.
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Observation of the Doubly Charmed Baryon Ξ_{cc}^{++}. PHYSICAL REVIEW LETTERS 2017; 119:112001. [PMID: 28949228 DOI: 10.1103/physrevlett.119.112001] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2017] [Indexed: 06/07/2023]
Abstract
A highly significant structure is observed in the Λ_{c}^{+}K^{-}π^{+}π^{+} mass spectrum, where the Λ_{c}^{+} baryon is reconstructed in the decay mode pK^{-}π^{+}. The structure is consistent with originating from a weakly decaying particle, identified as the doubly charmed baryon Ξ_{cc}^{++}. The difference between the masses of the Ξ_{cc}^{++} and Λ_{c}^{+} states is measured to be 1334.94±0.72(stat.)±0.27(syst.) MeV/c^{2}, and the Ξ_{cc}^{++} mass is then determined to be 3621.40±0.72(stat.)±0.27(syst.)±0.14(Λ_{c}^{+}) MeV/c^{2}, where the last uncertainty is due to the limited knowledge of the Λ_{c}^{+} mass. The state is observed in a sample of proton-proton collision data collected by the LHCb experiment at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 1.7 fb^{-1}, and confirmed in an additional sample of data collected at 8 TeV.
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Study of charmonium production in b -hadron decays and first evidence for the decay B s 0 → ϕ ϕ ϕ. THE EUROPEAN PHYSICAL JOURNAL. C, PARTICLES AND FIELDS 2017; 77:609. [PMID: 31997939 PMCID: PMC6956955 DOI: 10.1140/epjc/s10052-017-5151-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/01/2017] [Accepted: 08/20/2017] [Indexed: 06/10/2023]
Abstract
Using decays to ϕ -meson pairs, the inclusive production of charmonium states in b -hadron decays is studied with pp collision data corresponding to an integrated luminosity of 3.0 fb - 1 , collected by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. Denoting by B C ≡ B ( b → C X ) × B ( C → ϕ ϕ ) the inclusive branching fraction of a b hadron to a charmonium state C that decays into a pair of ϕ mesons, ratios R C 2 C 1 ≡ B C 1 / B C 2 are determined as R η c ( 1 S ) χ c 0 = 0.147 ± 0.023 ± 0.011 , R η c ( 1 S ) χ c 1 = 0.073 ± 0.016 ± 0.006 , R η c ( 1 S ) χ c 2 = 0.081 ± 0.013 ± 0.005 , R χ c 0 χ c 1 = 0.50 ± 0.11 ± 0.01 , R χ c 0 χ c 2 = 0.56 ± 0.10 ± 0.01 and R η c ( 1 S ) η c ( 2 S ) = 0.040 ± 0.011 ± 0.004 . Here and below the first uncertainties are statistical and the second systematic. Upper limits at 90% confidence level for the inclusive production of X(3872), X(3915) and χ c 2 ( 2 P ) states are obtained as R χ c 1 X ( 3872 ) < 0.34 , R χ c 0 X ( 3915 ) < 0.12 and R χ c 2 χ c 2 ( 2 P ) < 0.16 . Differential cross-sections as a function of transverse momentum are measured for the η c ( 1 S ) and χ c states. The branching fraction of the decay B s 0 → ϕ ϕ ϕ is measured for the first time, B ( B s 0 → ϕ ϕ ϕ ) = ( 2.15 ± 0.54 ± 0.28 ± 0 . 21 B ) × 10 - 6 . Here the third uncertainty is due to the branching fraction of the decay B s 0 → ϕ ϕ , which is used for normalization. No evidence for intermediate resonances is seen. A preferentially transverse ϕ polarization is observed. The measurements allow the determination of the ratio of the branching fractions for the η c ( 1 S ) decays to ϕ ϕ and p p ¯ as B ( η c ( 1 S ) → ϕ ϕ ) / B ( η c ( 1 S ) → p p ¯ ) = 1.79 ± 0.14 ± 0.32 .
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Measurement of B_{s}^{0} and D_{s}^{-} Meson Lifetimes. PHYSICAL REVIEW LETTERS 2017; 119:101801. [PMID: 28949189 DOI: 10.1103/physrevlett.119.101801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2017] [Indexed: 06/07/2023]
Abstract
We report on a measurement of the flavor-specific B_{s}^{0} lifetime and of the D_{s}^{-} lifetime using proton-proton collisions at center-of-mass energies of 7 and 8 TeV, collected by the LHCb experiment and corresponding to 3.0 fb^{-1} of integrated luminosity. Approximately 407 000 B_{s}^{0}→D_{s}^{(*)-}μ^{+}ν_{μ} decays are partially reconstructed in the K^{+}K^{-}π^{-}μ^{+} final state. The B_{s}^{0} and D_{s}^{-} natural widths are determined using, as a reference, kinematically similar B^{0}→D^{(*)-}μ^{+}ν_{μ} decays reconstructed in the same final state. The resulting differences between widths of B_{s}^{0} and B^{0} mesons and of D_{s}^{-} and D^{-} mesons are Δ_{Γ}(B)=-0.0115±0.0053(stat)±0.0041(syst) ps^{-1} and Δ_{Γ}(D)=1.0131±0.0117(stat)±0.0065(syst) ps^{-1}, respectively. Combined with the known B^{0} and D^{-} lifetimes, these yield the flavor-specific B_{s}^{0} lifetime, τ_{B_{s}^{0}}^{fs}=1.547±0.013(stat)±0.010(syst)±0.004(τ_{B}) ps and the D_{s}^{-} lifetime, τ_{D_{s}^{-}}=0.5064±0.0030(stat)±0.0017(syst)±0.0017(τ_{D}) ps. The last uncertainties originate from the limited knowledge of the B^{0} and D^{-} lifetimes. The results improve upon current determinations.
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Observation of the Decays Λ_{b}^{0}→χ_{c1}pK^{-} and Λ_{b}^{0}→χ_{c2}pK^{-}. PHYSICAL REVIEW LETTERS 2017; 119:062001. [PMID: 28949591 DOI: 10.1103/physrevlett.119.062001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2017] [Indexed: 06/07/2023]
Abstract
The first observation of the decays Λ_{b}^{0}→χ_{c1}pK^{-} and Λ_{b}^{0}→χ_{c2}pK^{-} is reported using a data sample corresponding to an integrated luminosity of 3.0 fb^{-1}, collected by the LHCb experiment in pp collisions at center-of-mass energies of 7 and 8 TeV. The following ratios of branching fractions are measured: B(Λ_{b}^{0}→χ_{c1}pK^{-})/B(Λ_{b}^{0}→J/ψpK^{-})=0.242±0.014±0.013±0.009,B(Λ_{b}^{0}→χ_{c2}pK^{-})/B(Λ_{b}^{0}→J/ψpK^{-})=0.248±0.020±0.014±0.009,B(Λ_{b}^{0}→χ_{c2}pK^{-})/B(Λ_{b}^{0}→χ_{c1}pK^{-})=1.02±0.10±0.02±0.05,where the first uncertainty is statistical, the second systematic, and the third due to the uncertainty on the branching fractions of the χ_{c1}→J/ψγ and χ_{c2}→J/ψγ decays. Using both decay modes, the mass of the Λ_{b}^{0} baryon is also measured to be m_{Λ_{b}^{0}}=5619.44±0.28±0.26 MeV/c^{2}, where the first and second uncertainties are statistical and systematic, respectively.
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First Observation of a Baryonic B_{s}^{0} Decay. PHYSICAL REVIEW LETTERS 2017; 119:041802. [PMID: 29341762 DOI: 10.1103/physrevlett.119.041802] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Indexed: 06/07/2023]
Abstract
We report the first observation of a baryonic B_{s}^{0} decay, B_{s}^{0}→pΛ[over ¯]K^{-}, using proton-proton collision data recorded by the LHCb experiment at center-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3.0 fb^{-1}. The branching fraction is measured to be B(B_{s}^{0}→pΛ[over ¯]K^{-})+B(B_{s}^{0}→p[over ¯]ΛK^{+})=[5.46±0.61±0.57±0.50(B)±0.32(f_{s}/f_{d})]×10^{-6}, where the first uncertainty is statistical and the second systematic, the third uncertainty accounts for the experimental uncertainty on the branching fraction of the B^{0}→pΛ[over ¯]π^{-} decay used for normalization, and the fourth uncertainty relates to the knowledge of the ratio of b-quark hadronization probabilities f_{s}/f_{d}.
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Measurement of the CP Violation Parameter A_{Γ} in D^{0}→K^{+}K^{-} and D^{0}→π^{+}π^{-} Decays. PHYSICAL REVIEW LETTERS 2017; 118:261803. [PMID: 28707946 DOI: 10.1103/physrevlett.118.261803] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2017] [Indexed: 06/07/2023]
Abstract
Asymmetries in the time-dependent rates of D^{0}→K^{+}K^{-} and D^{0}→π^{+}π^{-} decays are measured in a pp collision data sample collected with the LHCb detector during LHC Run 1, corresponding to an integrated luminosity of 3 fb^{-1}. The asymmetries in effective decay widths between D^{0} and D[over ¯]^{0} decays, sensitive to indirect CP violation, are measured to be A_{Γ}(K^{+}K^{-})=(-0.30±0.32±0.10)×10^{-3} and A_{Γ}(π^{+}π^{-})=(0.46±0.58±0.12)×10^{-3}, where the first uncertainty is statistical and the second systematic. These measurements show no evidence for CP violation and improve on the precision of the previous best measurements by nearly a factor of two.
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Search for the Decays B_{s}^{0}→τ^{+}τ^{-} and B^{0}→τ^{+}τ^{-}. PHYSICAL REVIEW LETTERS 2017; 118:251802. [PMID: 28696756 DOI: 10.1103/physrevlett.118.251802] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2017] [Indexed: 06/07/2023]
Abstract
A search for the rare decays B_{s}^{0}→τ^{+}τ^{-} and B^{0}→τ^{+}τ^{-} is performed using proton-proton collision data collected with the LHCb detector. The data sample corresponds to an integrated luminosity of 3 fb^{-1} collected in 2011 and 2012. The τ leptons are reconstructed through the decay τ^{-}→π^{-}π^{+}π^{-}ν_{τ}. Assuming no contribution from B^{0}→τ^{+}τ^{-} decays, an upper limit is set on the branching fraction B(B_{s}^{0}→τ^{+}τ^{-})<6.8×10^{-3} at the 95% confidence level. If instead no contribution from B_{s}^{0}→τ^{+}τ^{-} decays is assumed, the limit is B(B^{0}→τ^{+}τ^{-})<2.1×10^{-3} at the 95% confidence level. These results correspond to the first direct limit on B(B_{s}^{0}→τ^{+}τ^{-}) and the world's best limit on B(B^{0}→τ^{+}τ^{-}).
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Abstract
The production of J/ψ mesons in jets is studied in the forward region of proton-proton collisions using data collected with the LHCb detector at a center-of-mass energy of 13 TeV. The fraction of the jet transverse momentum carried by the J/ψ meson, z(J/ψ)≡p_{T}(J/ψ)/p_{T}(jet), is measured using jets with p_{T}(jet)>20 GeV in the pseudorapidity range 2.5<η(jet)<4.0. The observed z(J/ψ) distribution for J/ψ mesons produced in b-hadron decays is consistent with expectations. However, the results for prompt J/ψ production do not agree with predictions based on fixed-order nonrelativistic QCD. This is the first measurement of the p_{T} fraction carried by prompt J/ψ mesons in jets at any experiment.
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Measurement of the B_{s}^{0}→μ^{+}μ^{-} Branching Fraction and Effective Lifetime and Search for B^{0}→μ^{+}μ^{-} Decays. PHYSICAL REVIEW LETTERS 2017; 118:191801. [PMID: 28548525 DOI: 10.1103/physrevlett.118.191801] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2017] [Indexed: 06/07/2023]
Abstract
A search for the rare decays B_{s}^{0}→μ^{+}μ^{-} and B^{0}→μ^{+}μ^{-} is performed at the LHCb experiment using data collected in pp collisions corresponding to a total integrated luminosity of 4.4 fb^{-1}. An excess of B_{s}^{0}→μ^{+}μ^{-} decays is observed with a significance of 7.8 standard deviations, representing the first observation of this decay in a single experiment. The branching fraction is measured to be B(B_{s}^{0}→μ^{+}μ^{-})=(3.0±0.6_{-0.2}^{+0.3})×10^{-9}, where the first uncertainty is statistical and the second systematic. The first measurement of the B_{s}^{0}→μ^{+}μ^{-} effective lifetime, τ(B_{s}^{0}→μ^{+}μ^{-})=2.04±0.44±0.05 ps, is reported. No significant excess of B^{0}→μ^{+}μ^{-} decays is found, and a 95% confidence level upper limit, B(B^{0}→μ^{+}μ^{-})<3.4×10^{-10}, is determined. All results are in agreement with the standard model expectations.
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Observation of Five New Narrow Ω_{c}^{0} States Decaying to Ξ_{c}^{+}K^{-}. PHYSICAL REVIEW LETTERS 2017; 118:182001. [PMID: 28524669 DOI: 10.1103/physrevlett.118.182001] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2017] [Indexed: 06/07/2023]
Abstract
The Ξ_{c}^{+}K^{-} mass spectrum is studied with a sample of pp collision data corresponding to an integrated luminosity of 3.3 fb^{-1}, collected by the LHCb experiment. The Ξ_{c}^{+} is reconstructed in the decay mode pK^{-}π^{+}. Five new, narrow excited Ω_{c}^{0} states are observed: the Ω_{c}(3000)^{0}, Ω_{c}(3050)^{0}, Ω_{c}(3066)^{0}, Ω_{c}(3090)^{0}, and Ω_{c}(3119)^{0}. Measurements of their masses and widths are reported.
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Search for massive long-lived particles decaying semileptonically in the LHCb detector. THE EUROPEAN PHYSICAL JOURNAL. C, PARTICLES AND FIELDS 2017; 77:224. [PMID: 28515664 PMCID: PMC5408995 DOI: 10.1140/epjc/s10052-017-4744-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/06/2016] [Accepted: 03/07/2017] [Indexed: 06/07/2023]
Abstract
A search is presented for massive long-lived particles decaying into a muon and two quarks. The dataset consists of proton-proton interactions at centre-of-mass energies of 7 and 8 TeV, corresponding to integrated luminosities of 1 and 2[Formula: see text], respectively. The analysis is performed assuming a set of production mechanisms with simple topologies, including the production of a Higgs-like particle decaying into two long-lived particles. The mass range from 20 to 80 [Formula: see text] and lifetimes from 5 to 100[Formula: see text] are explored. Results are also interpreted in terms of neutralino production in different R-Parity violating supersymmetric models, with masses in the 23-198 GeV/[Formula: see text] range. No excess above the background expectation is observed and upper limits are set on the production cross-section for various points in the parameter space of theoretical models.
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Observation of B_{c}^{+}→D^{0}K^{+} Decays. PHYSICAL REVIEW LETTERS 2017; 118:111803. [PMID: 28368647 DOI: 10.1103/physrevlett.118.111803] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/07/2017] [Indexed: 06/07/2023]
Abstract
Using proton-proton collision data corresponding to an integrated luminosity of 3.0 fb^{-1}, recorded by the LHCb detector at center-of-mass energies of 7 and 8 TeV, the B_{c}^{+}→D^{0}K^{+} decay is observed with a statistical significance of 5.1 standard deviations. By normalizing to B^{+}→D[over ¯]^{0}π^{+} decays, a measurement of the branching fraction multiplied by the production rates for B_{c}^{+} relative to B^{+} mesons in the LHCb acceptance is obtained, R_{D^{0}K}=(f_{c}/f_{u})×B(B_{c}^{+}→D^{0}K^{+})=(9.3_{-2.5}^{+2.8}±0.6)×10^{-7}, where the first uncertainty is statistical and the second is systematic. This decay is expected to proceed predominantly through weak annihilation and penguin amplitudes, and is the first B_{c}^{+} decay of this nature to be observed.
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Measurement of the phase difference between short- and long-distance amplitudes in the [Formula: see text] decay. THE EUROPEAN PHYSICAL JOURNAL. C, PARTICLES AND FIELDS 2017; 77:161. [PMID: 28408857 PMCID: PMC5368951 DOI: 10.1140/epjc/s10052-017-4703-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Accepted: 02/16/2017] [Indexed: 06/07/2023]
Abstract
A measurement of the phase difference between the short- and long-distance contributions to the [Formula: see text] decay is performed by analysing the dimuon mass distribution. The analysis is based on pp collision data corresponding to an integrated luminosity of 3[Formula: see text] collected by the LHCb experiment in 2011 and 2012. The long-distance contribution to the [Formula: see text] decay is modelled as a sum of relativistic Breit-Wigner amplitudes representing different vector meson resonances decaying to muon pairs, each with their own magnitude and phase. The measured phases of the [Formula: see text] and [Formula: see text] resonances are such that the interference with the short-distance component in dimuon mass regions far from their pole masses is small. In addition, constraints are placed on the Wilson coefficients, [Formula: see text] and [Formula: see text], and the branching fraction of the short-distance component is measured.
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Observation of the Annihilation Decay Mode B^{0}→K^{+}K^{-}. PHYSICAL REVIEW LETTERS 2017; 118:081801. [PMID: 28282211 DOI: 10.1103/physrevlett.118.081801] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2016] [Indexed: 06/06/2023]
Abstract
A search for the B^{0}→K^{+}K^{-} decay is performed using pp-collision data collected by LHCb. The data set corresponds to integrated luminosities of 1.0 and 2.0 fb^{-1} at center-of-mass energies of 7 and 8 TeV, respectively. This decay is observed for the first time, with a significance of more than 5 standard deviations. The analysis also results in an improved measurement of the branching fraction for the B_{s}^{0}→π^{+}π^{-} decay. The measured branching fractions are B(B^{0}→K^{+}K^{-})=(7.80±1.27±0.81±0.21)×10^{-8} and B(B_{s}^{0}→π^{+}π^{-})=(6.91±0.54±0.63±0.19±0.40)×10^{-7}. The first uncertainty is statistical, the second is systematic, the third is due to the uncertainty on the B^{0}→K^{+}π^{-} branching fraction used as a normalization. For the B_{s}^{0} mode, the fourth accounts for the uncertainty on the ratio of the probabilities for b quarks to hadronize into B_{s}^{0} and B^{0} mesons.
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Observation of the Decay Ξ_{b}^{-}→pK^{-}K^{-}. PHYSICAL REVIEW LETTERS 2017; 118:071801. [PMID: 28256886 DOI: 10.1103/physrevlett.118.071801] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2016] [Indexed: 06/06/2023]
Abstract
Decays of the Ξ_{b}^{-} and Ω_{b}^{-} baryons to the charmless final states ph^{-}h^{'-}, where h^{(')} denotes a kaon or pion, are searched for with the LHCb detector. The analysis is based on a sample of proton-proton collision data collected at center-of-mass energies sqrt[s]=7 and 8 TeV, corresponding to an integrated luminosity of 3 fb^{-1}. The decay Ξ_{b}^{-}→pK^{-}K^{-} is observed with a significance of 8.7 standard deviations, and evidence at the level of 3.4 standard deviations is found for the Ξ_{b}^{-}→pK^{-}π^{-} decay. Results are reported, relative to the B^{-}→K^{+}K^{-}K^{-} normalization channel, for the products of branching fractions and b-hadron production fractions. The branching fractions of Ξ_{b}^{-}→pK^{-}π^{-} and Ξ_{b}^{-}→pπ^{-}π^{-} relative to Ξ_{b}^{-}→pK^{-}K^{-} decays are also measured.
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Observation of [Formula: see text] and [Formula: see text] decays. THE EUROPEAN PHYSICAL JOURNAL. C, PARTICLES AND FIELDS 2017; 77:72. [PMID: 28331428 PMCID: PMC5341203 DOI: 10.1140/epjc/s10052-017-4610-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/06/2016] [Accepted: 01/07/2017] [Indexed: 06/06/2023]
Abstract
The decays [Formula: see text] and [Formula: see text] are observed for the first time using a data sample corresponding to an integrated luminosity of 3.0 fb[Formula: see text], collected by the LHCb experiment in proton-proton collisions at the centre-of-mass energies of 7 and 8[Formula: see text]. The branching fractions relative to that of [Formula: see text] are measured to be [Formula: see text]where the first uncertainties are statistical and the second are systematic.
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Measurement of the b-Quark Production Cross Section in 7 and 13 TeV pp Collisions. PHYSICAL REVIEW LETTERS 2017; 118:052002. [PMID: 28211722 DOI: 10.1103/physrevlett.118.052002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2016] [Indexed: 06/06/2023]
Abstract
Measurements of the cross section for producing b quarks in the reaction pp→bb[over ¯]X are reported in 7 and 13 TeV collisions at the LHC as a function of the pseudorapidity η in the range 2<η<5 covered by the acceptance of the LHCb experiment. The measurements are done using semileptonic decays of b-flavored hadrons decaying into a ground-state charmed hadron in association with a muon. The cross sections in the covered η range are 72.0±0.3±6.8 and 154.3±1.5±14.3 μb for 7 and 13 TeV. The ratio is 2.14±0.02±0.13, where the quoted uncertainties are statistical and systematic, respectively. The agreement with theoretical expectation is good at 7 TeV, but differs somewhat at 13 TeV. The measured ratio of cross sections is larger at lower η than the model prediction.
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Observation of J/ψϕ Structures Consistent with Exotic States from Amplitude Analysis of B^{+}→J/ψϕK^{+} Decays. PHYSICAL REVIEW LETTERS 2017; 118:022003. [PMID: 28128595 DOI: 10.1103/physrevlett.118.022003] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2016] [Indexed: 06/06/2023]
Abstract
The first full amplitude analysis of B^{+}→J/ψϕK^{+} with J/ψ→μ^{+}μ^{-}, ϕ→K^{+}K^{-} decays is performed with a data sample of 3 fb^{-1} of pp collision data collected at sqrt[s]=7 and 8 TeV with the LHCb detector. The data cannot be described by a model that contains only excited kaon states decaying into ϕK^{+}, and four J/ψϕ structures are observed, each with significance over 5 standard deviations. The quantum numbers of these structures are determined with significance of at least 4 standard deviations. The lightest has mass consistent with, but width much larger than, previous measurements of the claimed X(4140) state.
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First Experimental Study of Photon Polarization in Radiative B_{s}^{0} Decays. PHYSICAL REVIEW LETTERS 2017; 118:021801. [PMID: 28128619 DOI: 10.1103/physrevlett.118.021801] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2016] [Indexed: 06/06/2023]
Abstract
The polarization of photons produced in radiative B_{s}^{0} decays is studied for the first time. The data are recorded by the LHCb experiment in pp collisions corresponding to an integrated luminosity of 3 fb^{-1} at center-of-mass energies of 7 and 8 TeV. A time-dependent analysis of the B_{s}^{0}→ϕγ decay rate is conducted to determine the parameter A^{Δ}, which is related to the ratio of right- over left-handed photon polarization amplitudes in b→sγ transitions. A value of A^{Δ}=-0.98_{-0.52}^{+0.46}_{-0.20}^{+0.23} is measured. This result is consistent with the standard model prediction within 2 standard deviations.
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Measurement of CP Violation in B^{0}→D^{+}D^{-} Decays. PHYSICAL REVIEW LETTERS 2016; 117:261801. [PMID: 28059544 DOI: 10.1103/physrevlett.117.261801] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2016] [Indexed: 06/06/2023]
Abstract
The CP violation observables S and C in the decay channel B^{0}→D^{+}D^{-} are determined from a sample of proton-proton collisions at center-of-mass energies of 7 and 8 TeV, collected by the LHCb experiment and corresponding to an integrated luminosity of 3 fb^{-1}. The observable S describes CP violation in the interference between mixing and the decay amplitude, and C parametrizes direct CP violation in the decay. The following values are obtained from a flavor-tagged, decay-time-dependent analysis: S=-0.54_{-0.16}^{+0.17}(stat)±0.05(syst), C=0.26_{-0.17}^{+0.18}(stat)±0.02(syst). These values provide evidence for CP violation at a significance level of 4.0 standard deviations. The phase shift due to higher-order standard model corrections is constrained to a small value of Δϕ=-0.16_{-0.21}^{+0.19} rad.
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Search for Structure in the B_{s}^{0}π^{±} Invariant Mass Spectrum. PHYSICAL REVIEW LETTERS 2016; 117:152003. [PMID: 27768360 DOI: 10.1103/physrevlett.117.152003] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Indexed: 06/06/2023]
Abstract
The B_{s}^{0}π^{±} invariant mass distribution is investigated in order to search for possible exotic meson states. The analysis is based on a data sample recorded with the LHCb detector corresponding to 3 fb^{-1} of pp collision data at sqrt[s]=7 and 8 TeV. No significant excess is found, and upper limits are set on the production rate of the claimed X(5568) state within the LHCb acceptance. Upper limits are also set as a function of the mass and width of a possible exotic meson decaying to the B_{s}^{0}π^{±} final state. The same limits also apply to a possible exotic meson decaying through the chain B_{s}^{*0}π^{±}, B_{s}^{*0}→B_{s}^{0}γ where the photon is excluded from the reconstructed decays.
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Evidence for Exotic Hadron Contributions to Λ_{b}^{0}→J/ψpπ^{-} Decays. PHYSICAL REVIEW LETTERS 2016; 117:082003. [PMID: 27588849 DOI: 10.1103/physrevlett.117.082003] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2016] [Indexed: 06/06/2023]
Abstract
A full amplitude analysis of Λ_{b}^{0}→J/ψpπ^{-} decays is performed with a data sample acquired with the LHCb detector from 7 and 8 TeV pp collisions, corresponding to an integrated luminosity of 3 fb^{-1}. A significantly better description of the data is achieved when, in addition to the previously observed nucleon excitations N→pπ^{-}, either the P_{c}(4380)^{+} and P_{c}(4450)^{+}→J/ψp states, previously observed in Λ_{b}^{0}→J/ψpK^{-} decays, or the Z_{c}(4200)^{-}→J/ψπ^{-} state, previously reported in B^{0}→J/ψK^{+}π^{-} decays, or all three, are included in the amplitude models. The data support a model containing all three exotic states, with a significance of more than three standard deviations. Within uncertainties, the data are consistent with the P_{c}(4380)^{+} and P_{c}(4450)^{+} production rates expected from their previous observation taking account of Cabibbo suppression.
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