The first search for ultra-rare K+ decays into the π+e+e−e+e− final state is reported, using a dataset collected by the NA62 experiment at CERN in 2017–2018. An upper limit of 1.4×10−8 at 90% CL is ...obtained for the branching ratio of the K+→π+e+e−e+e− decay, predicted in the Standard Model to be (7.2±0.7)×10−11. Upper limits at 90% CL are obtained at the level of 10−9 for the branching ratios of two prompt decay chains involving pair-production of hidden-sector mediators: K+→π+aa, a→e+e− and K+→π+S, S→A′A′, A′→e+e−.
Searches for lepton number violating K+→π−e+e+ and K+→π−π0e+e+ decays have been performed using the complete dataset collected by the NA62 experiment at CERN in 2016–2018. Upper limits of 5.3×10−11 ...and 8.5×10−10 are obtained on the decay branching fractions at 90% confidence level. The former result improves by a factor of four over the previous best limit, while the latter result represents the first limit on the K+→π−π0e+e+ decay rate.
Performance of the NA62 trigger system Cortina Gil, E.; Kleimenova, A.; Minucci, E. ...
The journal of high energy physics,
03/2023, Letnik:
2023, Številka:
3
Journal Article
Recenzirano
Odprti dostop
A
bstract
The NA62 experiment at CERN targets the measurement of the ultra-rare
K
+
→
π
+
ν
ν
¯
decay, and carries out a broad physics programme that includes probes for symmetry violations and ...searches for exotic particles. Data were collected in 2016–2018 using a multi-level trigger system, which is described highlighting performance studies based on 2018 data.
SUMMARY
The diagnosis of the antiphospholipid syndrome (APS) requires both a typical clinical event plus a persistently positive test in an assay for either anticardiolipin (aCL) antibodies or a ...lupus anticoagulant (LA). Enzyme linked immunosorbent assays (ELISA) specific for autoantibodies against β2-glycoprotein I (β2GPI) or prothrombin are also used, but none of the tests are adequately sensitive or specific. A chromogenic assay was developed that measures the effect of test antibody or plasma samples on in vitro thrombin formation. It is able to detect both LA and β2GPI-dependent aCL antibodies and may have greater specificity for APS than currently available tests. Using this method various monoclonal antibodies (MoAbs) were examined, from mice immunized with β2GPI, mice with a spontaneous animal model of APS, and from three humans with APS. Plasma and affinity purified antibodies from patients with APS and control groups were also examined. Thrombin inhibition was more sensitive to perturbation by MoAbs than a combination of tests for LA (P < 0·05) and at lower antibody concentrations (12·5 µg/ml versus 100 µg/ml). There was a significant correlation between inhibition of thrombin generation and the level of MoAb reactivity to β2GPI (r = 0·90; P < 0·001) but not to CL (r = 0·06; P = 0·76). Plasma and affinity purified antibodies from patients with APS also inhibited thrombin generation, and significantly more so than patients with aPL from causes other than APS. APS patient samples showed thrombin inhibition in the presence of anti-β2GPI or antiprothrombin antibodies. All MoAbs binding β2GPI showed inhibition of thrombin generation, while MoAbs binding domain I of β2GPI had more LA effect.
Measurement of the K+ → π+γγ decay Kleimenova, A.; Padolski, S.; Petrov, Y. ...
Physics letters. B,
March 2024, 2024-03-00, 2024-03-01, Letnik:
850
Journal Article
Recenzirano
Odprti dostop
A sample of 3984 candidates of the K+→π+γγ decay, with an estimated background of 291±14 events, was collected by the NA62 experiment at CERN during 2017–2018. In order to describe the observed ...di-photon mass spectrum, the next-to-leading order contribution in chiral perturbation theory was found to be necessary. The decay branching ratio in the full kinematic range is measured to be (9.61±0.17)×10−7. The first search for production and prompt decay of an axion-like particle with gluon coupling in the process K+→π+a, a→γγ is also reported.
A search for the K+→μ−νe+e+ decay, forbidden within the Standard Model by either lepton number or lepton flavour conservation depending on the flavour of the emitted neutrino, has been performed ...using the dataset collected by the NA62 experiment at CERN in 2016–2018. An upper limit of 8.1×10−11 is obtained for the decay branching fraction at 90% CL, improving by a factor of 250 over the previous search.
A
bstract
Measurement of the ultra-rare
K
+
→
π
+
ν
ν
¯
decay at the NA62 experiment at CERN requires high-performance particle identification to distinguish muons from pions. Calorimetric ...identification currently in use, based on a boosted decision tree algorithm, achieves a muon misidentification probability of 1
.
2 × 10
−
5
for a pion identification efficiency of 75% in the momentum range of 15–40 GeV/
c
. In this work, calorimetric identification performance is improved by developing an algorithm based on a convolutional neural network classifier augmented by a filter. Muon misidentification probability is reduced by a factor of six with respect to the current value for a fixed pion-identification efficiency of 75%. Alternatively, pion identification efficiency is improved from 72% to 91% for a fixed muon misidentification probability of 10
−
5
.
We describe a case of a Salmonella typhimurium mediastinal abscess in a patient with systemic lupus erythematosus (SLE). Patients with SLE are predisposed to nontyphoidal salmonella infection with a ...high incidenceof bacteraemiaand abscessformation.Our case is the first report of a mediastinalabscess from Salmonella typhimurium in an SLE patient and highlights the need for thorough assessment and treatment of SLE patients who have this organism identified.
PDF
