Simulation of the Belle II silicon vertex detector Kaleta, M.; Adamczyk, K.; Aggarwal, L. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
06/2022, Letnik:
1032
Journal Article
Recenzirano
Belle II is the next generation B Factory experiment operating at the SuperKEKB accelerator complex at KEK in Tsukuba, Japan. It is expected to collect 50 ab−1 of data, with a target instantaneous ...luminosity of 6.5 × 1035 cm−2s−1, which is about 30 times larger than its predecessor, Belle. In view of the ever increasing Belle II data sample, accurate simulation of the detector is growing in importance. This poses a challenging task of compromising between the realistic modeling of the response of individual detector components and reasonable performance in terms of CPU time of the simulation. In this paper we describe the simulation of the silicon vertex detector, its performance against collision data and optimization.
ANCA-associated vasculitides (AAV) are a heterogeneous group of rare diseases with unknown aetiology and the clinical spectrum ranging from life-threatening systemic disease, through single organ ...involvement to minor isolated skin changes. Thus, there is an unmet need for phenotype identification, especially among patients with granulomatosis with polyangiitis (GPA). Patients with microscopic polyangiitis (MPA) seem to be clinically much more uniform. Recently, three subcategories of AAV have been proposed and described as non-severe AAV, severe PR3-AAV, and severe MPO-AAV.
In line with these attempts, we decided to use an unbiased approach offered by latent class analysis (LCA) to subcategorise GPA and MPA in a large cohort of Polish AAV patients included in a multicentre POLVAS registry.
LCA of our AAV group identified a four-class model of AAV, including previously proposed three subphenotypes and revealing a fourth (previously not described) clinically relevant subphenotype. This new subphenotype includes only GPA patients, usually diagnosed at a younger age as compared to other groups, and characterised by multiorgan involvement, high relapse rate, relatively high risk of death, but no end-stage kidney disease.
Based on multiple clinical and serological variables, LCA methodology identified 4-class model of AAV. This newly described fourth class of AAV may be of clinical relevance and may require prompt diagnosis and aggressive treatment due to the multiorgan involvement, high risk of relapse and marked mortality among these relatively young GPA subjects.
We report searches for B0 → invisible and B0 → invisible + γ decays, where the energy of the photon is required to be larger than 0.5 GeV. These results are obtained from a 711 fb−1 data sample that ...contains 772 × 106 BB pairs and was collected near the Υ(4S) resonance with the Belle detector at the KEKB e+e− collider. We observe no significant signal for either decay and set upper limits on their branching fractions at 90% confidence level of B(B0 → invisible ) < 7.8 × 10−5 and B(B0 → invisible + γ ) < 1.6 × 10−5.
We report the measurement of branching fractions and CP-violation asymmetries in B → ϕϕK decays based on a 711 fb−1 data sample containing 772 × 106 B¯B events. The data were recorded at the Υ(4S) ...resonance with the Belle detector at the KEKB asymmetric-energy e+e− collider. For B+ → ϕϕK+, the branching fraction and CP-violation asymmetry measured below the ηc threshold ... respectively. Similarly, the branching fraction obtained for ... below the ηc threshold is ... . We also measure the CP-violation symmetry for ... within the ηc region ... .(ProQuest: ... denotes formulae omitted.)
Beam background study for the Belle II Silicon Vertex Detector Tanigawa, H.; Adamczyk, K.; Aihara, H. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2020, Letnik:
982
Journal Article
Recenzirano
The Belle II experiment aims to accumulate 50ab−1 of e+e− collision data at the SuperKEKB asymmetric energy collider (Tsukuba, Japan). The first physics data using all Belle II detectors were taken ...in spring 2019.
In the vast physics program of the Belle II experiment, the vertex detector plays a crucial role for the determination of the B-meson decay vertices. It consists of two inner layers of pixelated silicon detectors and four outer layers of double-sided silicon strip detectors (SVD).
To achieve a design luminosity of 8×1035cm−2s−1, 40 times higher than the recorded luminosity of its predecessor, the SuperKEKB collider squeezes the beams to a vertical size of 50 nm (“nano-beam scheme”) and doubles the beam currents.
Therefore, the detectors are required to tolerate intense beam induced background due to the very high luminosity. During the 2019 spring run we measured the occupancy rate in the SVD to estimate the level of the beam induced background. With the low initial luminosity, the observed beam induced background mostly originated from Touschek processes and beam-gas scattering within individual beams. Since these different background contributions depend differently on accelerator conditions, such as the beam current, beam size and pressure, they can be disentangled. We estimate the background rate of each contribution and compare them with simulated ones. The results enable us to predict the background levels at increased beam currents and luminosity in the coming years. They also hint at background mitigation measures for running at higher luminosity. In this proceeding we present the results of our study of the beam induced background in the SVD and the prospects for future operation.
We present a determination of the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element V sub(cb) using the decay B arrow right Dscriptlnu sub(scriptl)(scriptl= e, mu ) based on 711fb super(-1) ...of e super(+)e super(-) arrow right Gamma(4S) data recorded by the Belle detector and containing 772x10 super(6)BB pairs. One B meson in the event is fully reconstructed in a hadronic decay mode, while the other, on the signal side, is partially reconstructed from a charged lepton and either a D super(+) or D super(0) meson in a total of 23 hadronic decay modes. The isospin-averaged branching fraction of the decay B arrow right Dscriptlnu sub(scriptl) is found to be Bernoulli(B super(0) arrow right D super(?)scriptl super(+)nu sub(s criptl))=(2.31+ or -0.03(stat)+ or -0.11(syst))% . Analyzing the differential decay rate as a function of the hadronic recoil with the parametrization of Caprini, Lellouch, and Neubert and using the form-factor prediction scriptG(1)=1.0541+ or -0.0083 calculated by FNAL/MILC, we obtain eta sub(EW)V sub(cb)=(40.12+ or -1.34)x10 super(-3), where eta sub(EW) is the electroweak correction factor. Alternatively, assuming the model-independent form-factor parametrization of Boyd, Grinstein, and Lebed and using lattice QCD data from the FNAL/MILC and HPQCD collaborations, we find eta sub(EW)V sub(cb)=(41.10+ or -1.14)x10 super(-3)
We report the first measurement of the lepton forward-backward asymmetry scriptA sub(FB) as a function of the squared four-momentum of the dilepton system, q super(2), for the electroweak penguin ...process B arrow right X sub(s)scriptl super(+)scriptl super(-) with a sum of exclusive final states, where scriptl is an electron or a muon and X sub(s) is a hadronic recoil system with an s quark. The results are based on a data sample containing 772x10 super(6)BB pairs recorded at the Gamma(4S) resonance with the Belle detector at the KEKB e super(+)e super(-) collider. scriptA sub(FB) for the inclusive B arrow right X sub(s)scriptl super(+)scriptl super(-) is extrapolated from the sum of 10 exclusive X sub(s) states whose invariant mass is less than 2GeV/c super(2). For q super(2)>10.2GeV super(2)/c super(2), scriptA sub(FB)<0 is excluded at the 2.3sigma level, where sigma is the standard deviation. For q super(2)<4.3GeV super(2)/c super(2) , the result is within 1.8sigma of the standard model theoretical expectation.
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