Constraints on the K_{S}^{0}→μ^{+}μ^{-} Branching Fraction

A search for the decay K_{S}^{0}→μ^{+}μ^{-} is performed using proton-proton collision data, corresponding to an integrated luminosity of 5.6  fb^{-1} and collected with the LHCb experiment during 2016, 2017, and 2018 at a center-of-mass energy of 13 TeV. The observed signal yield is consistent with zero, yielding an upper limit of B(K_{S}^{0}→μ^{+}μ^{-})<2.2×10^{-10} at 90% C.L.. The limit reduces to B(K_{S}^{0}→μ^{+}μ^{-})<2.1×10^{-10} at 90% C.L. once combined with the result from data taken in 2011 and 2012.

Observation of Enhanced Double Parton Scattering in Proton-Lead Collisions at sqrt[s_{NN}]=8.16 TeV

A study of prompt charm-hadron pair production in proton-lead collisions at sqrt[s_{NN}]=8.16  TeV is performed using data corresponding to an integrated luminosity of about 30  nb^{-1}, collected with the LHCb experiment. Production cross sections for different pairs of charm hadrons are measured and kinematic correlations between the two charm hadrons are investigated. This is the first measurement of associated production of two charm hadrons in proton-lead collisions. The results confirm the predicted enhancement of double parton scattering production in proton-lead collisions compared to the single parton scattering production.

Clinical summary guide: reproduction in women with previous abdominopelvic radiotherapy or total body irradiation

STUDY QUESTION

What is the evidence to guide the management of women who wish to conceive following abdominopelvic radiotherapy (AP RT) or total body irradiation (TBI)?

SUMMARY ANSWER

Pregnancy is possible, even following higher doses of post-pubertal uterine radiation exposure; however, it is associated with adverse reproductive sequelae and pregnancies must be managed in a high-risk obstetric unit.

WHAT IS KNOWN ALREADY

In addition to primary ovarian insufficiency, female survivors who are treated with AP RT and TBI are at risk of damage to the uterus. This may impact on its function and manifest as adverse reproductive sequelae.

STUDY DESIGN SIZE DURATION

A review of the literature was carried out and a multidisciplinary working group provided expert opinion regarding assessment of the uterus and obstetric management.

PARTICIPANTS/MATERIALS SETTING METHODS

Reproductive outcomes for postpubertal women with uterine radiation exposure in the form of AP RT or TBI were reviewed. This included Pubmed listed peer-reviewed publications from 1990 to 2019, and limited to English language..

MAIN RESULTS AND THE ROLE OF CHANCE

The prepubertal uterus is much more vulnerable to the effects of radiation than after puberty. Almost all available information about the impact of radiation on the uterus comes from studies of radiation exposure during childhood or adolescence.An uncomplicated pregnancy is possible, even with doses as high as 54 Gy. Therefore, tumour treatment doses alone cannot at present be used to accurately predict uterine damage.

LIMITATIONS REASONS FOR CAUTION

Much of the data cannot be readily extrapolated to adult women who have had uterine radiation and the publications concerning adult women treated with AP RT are largely limited to case reports.

WIDER IMPLICATIONS OF THE FINDINGS

This analysis offers clinical guidance and assists with patient counselling. It is important to include patients who have undergone AP RT or TBI in prospective studies to provide further evidence regarding uterine function, pregnancy outcomes and correlation of imaging with clinical outcomes.

STUDY FUNDING/COMPETING INTERESTS

This study received no funding and there are no conflicts of interest.

TRIAL REGISTRATION NUMBER

N/A.

ApoB48-Lipoproteins Are Associated with Cardiometabolic Risk in Adolescents with and without Polycystic Ovary Syndrome

CONTEXT

Adolescents with polycystic ovary syndrome (PCOS) have increased incidence of cardiometabolic risk factors including dyslipidemia. Atherogenic apolipoprotein (apo) B-lipoprotein remnants are associated with increased cardiovascular disease (CVD) risk.

OBJECTIVE

The aim of this study was to determine the concentrations of fasting plasma apoB-lipoprotein remnants, apoB48 and apoB100, and their association with cardiometabolic risk factors and androgen indices in adolescent girls with and without PCOS.

DESIGN SETTING AND PARTICIPANTS

Participants (n = 184) aged 17 years were recruited in the Menstruation in Teenagers Study from the Western Australian Pregnancy Cohort (Raine) Study.

THE MAIN OUTCOME MEASURES

Fasting plasma apo-B48 and -B100 lipoprotein remnant concentrations in adolescent girls with and without PCOS.

RESULTS

Fasting plasma apoB48-lipoprotein remnants but not apoB100-lipoprotein remnants were elevated in adolescent girls with increased cardiometabolic risk compared with those with lower cardiometabolic risk (13.91 ± 5.06 vs 12.09 ± 4.47 µg/mL, P < .01). ApoB48-lipoprotein remnants were positively correlated with fasting plasma triglycerides (b = .43, P < .0001). The prevalence of increased cardiometabolic risk factors was 2-fold higher in those diagnosed with PCOS (35.3%) than in those without PCOS (16.3%).Conclusion: Adolescents with PCOS have a 2-fold higher incidence of cardiometabolic risk factors than those without PCOS. Fasting apoB48-lipoprotein remnants are elevated in adolescent girls with a high prevalence of cardiometabolic risk factors.

The association between in-utero exposure to stressful life events during pregnancy and male reproductive function in a cohort of 20-year-old offspring: The Raine Study

STUDY QUESTION

Is exposure to gestational stress in the critical time window for the normal differentiation and growth of male reproductive tissue associated with male reproductive function in offspring in later life?

SUMMARY ANSWER

Exposure to stressful life events (SLEs) in early, but not late gestation, are associated with reduced adult male reproductive function, consistent with the hypothesis that events during early prenatal life programme adult male reproductive function.

WHAT IS ALREADY KNOWN

Animal studies suggest that gestational stress may impact on the reproductive function of male offspring, but human evidence is sparse.

STUDY DESIGN, SIZE, DURATION

Using a prospective longitudinal cohort, we examined the association between number and type of maternal stressors during pregnancy in both early and late gestation and reproductive function in 643 male Generation 2 (offspring) at age 20 years. Mothers and their male Generation 2 (offspring) from The Raine Study participated. Mothers prospectively reported SLEs during pregnancy recorded at gestational weeks 18 and 34 using a standardized 10-point questionnaire.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The 643 male Generation 2 (offspring) underwent testicular ultrasound examination and semen analysis and provided serum for reproductive hormone analysis. Multivariate linear regression analysis was used to examine associations.

MAIN RESULTS AND ROLE OF CHANCE

Of 643 recruited males, 407 (63%) were exposed to at least one SLE in early gestation. Fewer SLEs were reported in late gestation (n = 343, 53%). Maternal SLE exposure in early gestation was negatively associated with total sperm count (β = -0.31, 95% CI -0.58; -0.03), number of progressive motile sperm (β = -0.15, 95% CI -0.31; 0.00) and morning serum testosterone concentration (β = -0.04, 95% CI -0.09; -0.00). No similar effects of maternal SLE exposure in late pregnancy were detected. The large sample size and an objective detailed direct assessment of adult male reproductive function with strict external quality control for sperm quality, as well as detailed prospectively collected information on prenatal SLEs in two distinct time windows of pregnancy reported by the women in early and late gestation along with other risk factors, imply minimal possibility of recall, information bias and selection bias. When assessing our results, we adjusted for a priori chosen confounders, but residual confounding or confounding by factors unbeknown to us cannot be ruled out.

LIMITATIONS, REASONS FOR CAUTION

It is not possible to measure how SLEs impacted differently on the mother's experience or perception of stress. Resilience (coping) gradients may alter cortisol levels and thus modify the associations we observed and the mothers' own perception of stress severity may have provided a more precise estimate of her exposure.

WIDER IMPLICATIONS OF THE FINDINGS

Our findings suggest that exposure to SLEs in early, but not late gestation, are associated with reduced adult male reproductive function. Improved support for women with exposure to SLEs during pregnancy, particularly during the first trimester, may improve the reproductive health of their male offspring in later life. Intervention studies of improved pregnancy support could provide more insight into this association and more information is needed about the potential specific epigenetic mechanisms underlying this association.

STUDY FUNDING/COMPETING INTEREST(S)

The male fertility sub-study was funded by NHMRC Grant 634 457. The core management of the Raine Study is funded by University of Western Australia, Curtin University, Telethon Kids Institute, Women and Infants Research Foundation, Edith Cowan University, Murdoch University, The University of Notre Dame Australia and Raine Medical Research foundation. Dr Bräuner's salary was supported by Læge Sofus Carl Emil Friis og Hustru Olga Doris Friis foundation in Denmark. All authors declare no competing interests.

TRIAL REGISTRATION NUMBER

N/A.

Measurement of CP-Averaged Observables in the B^{0}→K^{*0}μ^{+}μ^{-} Decay

An angular analysis of the B^{0}→K^{*0}(→K^{+}π^{-})μ^{+}μ^{-} decay is presented using a dataset corresponding to an integrated luminosity of 4.7  fb^{-1} of pp collision data collected with the LHCb experiment. The full set of CP-averaged observables are determined in bins of the invariant mass squared of the dimuon system. Contamination from decays with the K^{+}π^{-} system in an S-wave configuration is taken into account. The tension seen between the previous LHCb results and the standard model predictions persists with the new data. The precise value of the significance of this tension depends on the choice of theory nuisance parameters.

Observation of New Ξ_{c}^{0} Baryons Decaying to Λ_{c}^{+}K^{-}

The Λ_{c}^{+}K^{-} mass spectrum is studied with a data sample of pp collisions at a center-of-mass energy of 13 TeV corresponding to an integrated luminosity of 5.6  fb^{-1} collected by the LHCb experiment. Three Ξ_{c}^{0} states are observed with a large significance and their masses and natural widths are measured to be m[Ξ_{c}(2923)^{0}]=2923.04±0.25±0.20±0.14  MeV, Γ[Ξ_{c}(2923)^{0}]=7.1±0.8±1.8  MeV, m[Ξ_{c}(2939)^{0}]=2938.55±0.21±0.17±0.14  MeV, Γ[Ξ_{c}(2939)^{0}]=10.2±0.8±1.1  MeV, m[Ξ_{c}(2965)^{0}]=2964.88±0.26±0.14±0.14  MeV, Γ[Ξ_{c}(2965)^{0}]=14.1±0.9±1.3  MeV, where the uncertainties are statistical, systematic, and due to the limited knowledge of the Λ_{c}^{+} mass. The Ξ_{c}(2923)^{0} and Ξ_{c}(2939)^{0} baryons are new states. The Ξ_{c}(2965)^{0} state is in the vicinity of the known Ξ_{c}(2970)^{0} baryon; however, their masses and natural widths differ significantly.

Search for the Rare Decays B_{s}^{0}→e^{+}e^{-} and B^{0}→e^{+}e^{-}

A search for the decays B_{s}^{0}→e^{+}e^{-} and B^{0}→e^{+}e^{-} is performed using data collected with the LHCb experiment in proton-proton collisions at center-of-mass energies of 7, 8, and 13 TeV, corresponding to integrated luminosities of 1, 2, and 2  fb^{-1}, respectively. No signal is observed. Assuming no contribution from B^{0}→e^{+}e^{-} decays, an upper limit on the branching fraction B(B_{s}^{0}→e^{+}e^{-})<9.4(11.2)×10^{-9} is obtained at 90(95)% confidence level. If no B_{s}^{0}→e^{+}e^{-} contribution is assumed, a limit of B(B^{0}→e^{+}e^{-})<2.5(3.0)×10^{-9} is determined at 90(95)% confidence level. These upper limits are more than one order of magnitude lower than the previous values.

OR31-02 Diagnostic Criteria for Polycystic Ovary Syndrome in Adolescents: Impact on Prevalence and Longitudinal Body Mass Index Trajectories

Background: Polycystic ovary syndrome (PCOS) is characterised by oligo-anovulation (OA), hyperandrogenism (HA) and polycystic ovary morphology (PCO). While the Rotterdam criteria (defined as 2 out of 3 features) are the most widely used criteria in adults, controversy remains for the diagnostic criteria in adolescents as many PCOS features overlap with normal pubertal physiological changes. The 2018 international evidence-based PCOS guideline recommends modified Rotterdam criteria (OA and HA) in adolescents based on expert consensus. We aimed to 1) compare the prevalence of PCOS using original and modified Rotterdam criteria in an unselected adolescent cohort and 2) explore the association between diagnostic phenotypes and long-term body mass index (BMI) trajectories. Methods: 227 adolescent females of the Western Australian Pregnancy Cohort (Raine) Study undertook detailed PCOS assessment at the mean age of 15.3 years (mean age of menarche 12.4 years). Detailed anthropometric measurements were collected from birth until age 22 years. T-test was used for group BMI comparisons and longitudinal BMI was analysed using Generalised Estimating Equations with PCOS by time and PCOS phenotypes by time as interaction terms. Results: PCOS was diagnosed in 66 (29.1%) participants using original Rotterdam criteria versus 37 (16.3%) participants using modified Rotterdam criteria. Using modified Rotterdam criteria, participants with PCOS had higher mean group BMI than participants without PCOS from age 5 years onwards. Significant interaction was detected between PCOS and time (p<0.001) on longitudinal BMI gain where higher BMI gain was observed in participants with PCOS from age 14 years onwards. Only the modified criteria phenotype was significantly associated wth long-term BMI gain whereas other PCOS phenotypes had similar BMI trajectories as participants without PCOS (p<0.001). Conclusions: Our findings validate the PCOS guideline recommendation as modified Rotterdam criteria reduce over-diagnosis of PCOS in adolescents and accurately identify the phenotype at risk of long-term weight gain. The BMI trajectories of females with and without PCOS diverge from early childhood suggesting that metabolic dysfunction in PCOS commences early in the pre-pubertal period. Disclosures: Nothing to disclose. Funding: PCOS CRE scholarship and Research Training Program Scholarship awarded to CT; NHMRC Medical Research Future fund awarded to HT; National Heart Foundation Future Leader Fellowship awarded to LM; NHMRC early career fellowship awarded to AJ.

Isospin Amplitudes in Λ_{b}^{0}→J/ψΛ(Σ^{0}) and Ξ_{b}^{0}→J/ψΞ^{0}(Λ) Decays

Ratios of isospin amplitudes in hadron decays are a useful probe of the interplay between weak and strong interactions and allow searches for physics beyond the standard model. We present the first results on isospin amplitudes in b-baryon decays, using data corresponding to an integrated luminosity of 8.5  fb^{-1}, collected with the LHCb detector in pp collisions at center of mass energies of 7, 8, and 13 TeV. The isospin amplitude ratio |A_{1}(Λ_{b}^{0}→J/ψΣ^{0})/A_{0}(Λ_{b}^{0}→J/ψΛ)|, where the subscript on A indicates the final-state isospin, is measured to be less than 1/21.8 at 95% confidence level. The Cabibbo suppressed Ξ_{b}^{0}→J/ψΛ decay is observed for the first time, allowing for the measurement |A_{0}(Ξ_{b}^{0}→J/ψΛ)/A_{1/2}(Ξ_{b}^{0}→J/ψΞ^{0})|=0.37±0.06±0.02, where the uncertainties are statistical and systematic, respectively.

First Observation of Excited Ω_{b}^{-} States

We report four narrow peaks in the Ξ_{b}^{0}K^{-} mass spectrum obtained using pp collisions at center-of-mass energies of 7, 8, and 13 TeV, corresponding to a total integrated luminosity of 9  fb^{-1} recorded by the LHCb experiment. Referring to these states by their mass, the mass values are m[Ω_{b}(6316)^{-}]=6315.64±0.31±0.07±0.50  MeV, m[Ω_{b}(6330)^{-}]=6330.30±0.28±0.07±0.50  MeV, m[Ω_{b}(6340)^{-}]=6339.71±0.26±0.05±0.50  MeV, m[Ω_{b}(6350)^{-}]=6349.88±0.35±0.05±0.50  MeV, where the uncertainties are statistical, systematic, and the last is due to the knowledge of the Ξ_{b}^{0} mass. The natural widths of the three lower mass states are consistent with zero, and the 90% confidence-level upper limits are determined to be Γ[Ω_{b}(6316)^{-}]<2.8  MeV, Γ[Ω_{b}(6330)^{-}]<3.1  MeV and Γ[Ω_{b}(6340)^{-}]<1.5  MeV. The natural width of the Ω_{b}(6350)^{-} peak is 1.4_{-0.8}^{+1.0}±0.1  MeV, which is 2.5σ from zero and corresponds to an upper limit of 2.8 MeV. The peaks have local significances ranging from 3.6σ to 7.2σ. After accounting for the look-elsewhere effect, the significances of the Ω_{b}(6316)^{-} and Ω_{b}(6330)^{-} peaks are reduced to 2.1σ and 2.6σ, respectively, while the two higher mass peaks exceed 5σ. The observed peaks are consistent with expectations for excited Ω_{b}^{-} resonances.

Search for A^{'}→μ^{+}μ^{-} Decays

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. These searches look for A^{'}→μ^{+}μ^{-} decays using a data sample corresponding to an integrated luminosity of 5.5  fb^{-1} collected with the LHCb detector. Neither search finds evidence for a signal, and 90% confidence-level exclusion limits are placed on the γ-A^{'} kinetic mixing strength. The promptlike A^{'} search explores the mass region from near the dimuon threshold up to 70 GeV and places the most stringent constraints to date on dark photons with 214<m(A^{'})≲740  MeV and 10.6<m(A^{'})≲30  GeV. The search for long-lived A^{'}→μ^{+}μ^{-} decays places world-leading constraints on low-mass dark photons with lifetimes O(1)  ps.

The cumulative success of ovulation induction therapy with gonadotrophins in therapy-naïve anovulatory women: An observational study

BACKGROUND

The use of gonadotrophins as a first-line treatment for anovulatory infertility has been limited by a perception of a risk of multi-fetal gestation and ovarian hyperstimulation syndrome (OHSS). However, it has recently been recognised as an acceptable first-line treatment if appropriate monitoring is performed.

AIMS

To determine the cumulative live birth rate, incidence of multiple gestation, cycle cancellation rate and incidence of OHSS for therapy-naïve anovulatory women undergoing ovulation induction with gonadotrophins.

MATERIALS AND METHODS

A prospective observational study of 258 patients undergoing ovulation induction with a 'low-dose step-up' protocol was performed over a three-year period across two fertility centres (40% of patients were currently or recently prescribed metformin).

RESULTS

Twenty-six percent of patients required concurrent use of luteinising hormone. The cumulative pregnancy and live birth rates were 22.5% and 18.2%, 40.3% and 34.5%, 47.7% and 41.1% after completion of the first, second and third cycles of stimulation, respectively, with a median duration of stimulation of 15 days. No patients developed OHSS and 10.5% of cycles were cancelled due to an excessive or no follicular response. The multiple pregnancy rate was 2%. The cumulative pregnancy rate was reduced for women over 35 years of age (23.8 vs 55.3%, P = 0.006) and for women with a body mass index greater than 25 kg/m² (40.6 vs 56.7%, P = 0.027)_. CONCLUSIONS: This study demonstrated that ovulation induction with gonadotrophin therapy, in the context of appropriate monitoring, is a safe and effective treatment for young therapy-naïve patients with anovulatory infertility.

[Derotational Intertrochanteric Osteotomy in Habitual Dislocation of the Patella]

PURPOSE OF THE STUDY The preoperative planning in habitual dislocation of the patella should take into account all pathologies and the procedure should address all abnormalities. One of them might be also the rotational deformity of the femur. The purpose of this prospective study was to confirm the hypothesis that the only correction of pathological femoral anteversion by derotational intertrochanteric osteotomy (in the absence of another pathology) or the correction of femoral anteversion with simultaneous reconstruction of the patellofemoral joint provide adequate stability for the patellofemoral joint, with respect to the elimination of the risk of recurrent dislocation of the patella. MATERIAL AND METHODS In the course of 15 years, 17 patients (20 knee joints) with habitual dislocation of the patella were included in the study, in whom the CT scan also confirmed the femoral anteversion of 35° and greater. The group was female-dominant, often with BMI > 30. The mean age was 26 years. In 4 cases only derotational intertrochanteric osteotomy was performed, in 16 patients the osteotomy was followed by the stabilization of the patella in the knee region (always individually in dependence on the diagnosed pathology), of whom in 2 cases as the second step procedure because of thrombophilic disorders detected earlier. Immediately after the surgery, or at 6 weeks postoperatively (depending on the knee procedure done), individual rehabilitation was commenced. Partial weight bearing was recommended for the period of 3 months after the surgery. The mean follow-up period was 39 months (minimum of 36 months). RESULTS In one case a failure of osteosynthesis was observed and revision osteosynthesis with an intramedullary nail was performed. In all the other cases, primary healing of the osteotomy was achieved. The other complications were less significant (1 case of asymptomatic deep vein thrombosis of the lower limb, evacuation of subcutaneous haematoma in 1 case, 3 cases of the knee stiffness solved by manipulation under general anaesthesia at 6 weeks after surgery). Recurrent patellar dislocation was not observed in any of the patients. No pain in the upper thigh was reported by patients during the last follow-up control (at least 3 years postoperatively). Three female patients reported an isolated feeling of patellar instability. DISCUSSION There are very few studies focusing on the femoral derotational osteotomy for habitual dislocation of the patella in world literature. If any at all, they concern supracondylar and not intertrochanteric femoral osteotomy and the groups of patients were smaller than the group evaluated by us. CONCLUSIONS Preoperative planning for habitual dislocation of the patella should definitely reflect all pathologies. Therefore, the femoral derotational osteotomy should certainly be mastered by the orthopaedic surgeon, though it is a larger and more exacting procedure than patellar stabilizations in the knee region. Indications for this type of osteotomy should include anteversion greater than 30°, or 35°. The derotational intertrochanteric osteotomy alone or its combination with the stabilization of the patella in the knee region brings reliable results with no risk of recurrent dislocation. Key words: patella, habitual dislocation, femur, anteversion, derotational osteotomy.

[Occult Injuries to Posterior Pelvic Segment in Elderly Patients with Pubic Rami Fractures]

PURPOSE OF THE STUDY The incidence of pelvic fractures in geriatric population has been increasing. The diagnostic method of first choice is plain pelvic anteroposterior X-ray which, however, mostly reveals merely the pubic rami fractures. The pain caused by undiagnosed lesion of the posterior pelvic segment may substantially reduce the patient s mobility, thus also their self-sufficiency which is crucial in elderly patients. The purpose of this prospective study was to evaluate the incidence of an occult injury to the posterior pelvic ring in patients with an X-ray finding of pubic rami fractures only. MATERIAL AND METHODS Throughout a three-year period (2017-2019), the incidence of an occult injury to the posterior pelvic ring was evaluated by means of a CT scan in 50 patients aged 65 years and over, in whom the plain anteroposterior pelvic radiograph initially revealed only the pubic rami fractures. The mean age of 35 women and 15 men was 76 years (the range of 65-94 years). RESULTS In 15 patients (30%) only, the CT scan confirmed the isolated pubic rami fracture. In the remaining 35 cases (70%), the CT scan revealed an injury to the posterior pelvic segment, namely in 32 cases ipsilaterally, in one case contralaterally and in two patients bilaterally. In 4 patients (8%) only, signs of the injury to the posterior pelvic segment were subsequently found on the plain X-ray of the pelvis. DISCUSSION Diagnosis of a pubic rami fracture in geriatric patients solely based on the performed X-ray can be misleading. It has been proven in our prospective study that majority of injuries to posterior pelvic ring is not detected on the plain X-ray, which is also the conclusion arrived at by foreign authors. The CT scan alone can safely determine the actual extent of the pelvic injury. While the isolated injuries to the anterior pelvic ring show biomechanical stability, and thus are less painful and can be successfully treated non-operatively, the associated injuries to the posterior pelvic ring can cause a certain degree of instability, which has to be reflected in treatment strategy. CONCLUSIONS Injuries to the posterior pelvic segment in geriatric population are much more frequent than expected. They are, however, rarely distinguishable on a plain radiograph. Often times, only the pubic rami fractures are clearly visible. The fractures of posterior segment tend to be accompanied by a higher number of complications and a worse prognosis. A reliable method to detect these injuries is the unenhanced CT scan of the pelvis that should be performed routinely in all the patients with pubic rami fractures identified on a radiograph. In cases when pain substantially limits the mobilisation of the patients, minimally invasive surgical treatment should be considered. Key words: pelvic ring injury, pubic rami, geriatric population.

Observation of New Resonances in the Λ_{b}^{0}π^{+}π^{-} System

We report the observation of a new structure in the Λ_{b}^{0}π^{+}π^{-} spectrum using the full LHCb data set of pp collisions, corresponding to an integrated luminosity of 9  fb^{-1}, collected at sqrt[s]=7, 8, and 13 TeV. A study of the structure suggests its interpretation as a superposition of two almost degenerate narrow states. The masses and widths of these states are measured to be m_{Λ_{b}(6146)^{0}}=6146.17±0.33±0.22±0.16  MeV,m_{Λ_{b}(6152)^{0}}=6152.51±0.26±0.22±0.16  MeV,Γ_{Λ_{b}(6146)^{0}}=2.9±1.3±0.3  MeV,Γ_{Λ_{b}(6152)^{0}}=2.1±0.8±0.3  MeV,with a mass splitting of Δm=6.34±0.32±0.02  MeV, where the first uncertainty is statistical, the second systematic. The third uncertainty for the mass measurements derives from the knowledge of the mass of the Λ_{b}^{0} baryon. The measured masses and widths of these new excited states suggest their possible interpretation as a doublet of Λ_{b}(1D)^{0} states.