First measurements of beam backgrounds at SuperKEKB Lewis, P.M.; Jaegle, I.; Nakayama, H. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
01/2019, Volume:
914
Journal Article
Peer reviewed
Open access
The high design luminosity of the SuperKEKB electron–positron collider is expected to result in challenging levels of beam-induced backgrounds in the interaction region. Properly simulating and ...mitigating these backgrounds is critical to the success of the Belle II experiment. We report on measurements performed with a suite of dedicated beam background detectors, collectively known as BEAST II, during the so-called Phase 1 commissioning run of SuperKEKB in 2016, which involved operation of both the high energy ring (HER) of 7 GeV electrons as well as the low energy ring (LER) of 4 GeV positrons. We describe the BEAST II detector systems, the simulation of beam backgrounds, and the measurements performed. The measurements include standard ones of dose rates versus accelerator conditions, and more novel investigations, such as bunch-by-bunch measurements of injection backgrounds and measurements sensitive to the energy spectrum and angular distribution of fast neutrons. We observe beam–gas, Touschek, beam–dust, and injection backgrounds. As there is no final focus of the beams in Phase 1, we do not observe significant synchrotron radiation, as expected. Measured LER beam–gas backgrounds and Touschek backgrounds in both rings are slightly elevated, on average three times larger than the levels predicted by simulation. HER beam–gas backgrounds are on average two orders of magnitude larger than predicted. Systematic uncertainties and channel-to-channel variations are large, so that these excesses constitute only 1–2 sigma level effects. Neutron background rates are higher than predicted and should be studied further. We will measure the remaining beam background processes, due to colliding beams, in the imminent commissioning Phase 2. These backgrounds are expected to be the most critical for Belle II, to the point of necessitating replacement of detector components during the Phase 3 (full-luminosity) operation of SuperKEB.
Summary of Session 2: Data analysis—algorithms and tools Kiesling, C.
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2006, Volume:
559, Issue:
1
Journal Article
Peer reviewed
This report summarizes the Session 2 (“Data Analysis—Algorithms and Tools”), reviewing shortly the evolvement of this session during the series of ACAT workshops, emphasizing the highlights and ...recent developments of methods presented at this workshop, and presenting some thoughts as regards to the possible future development of the session within the ACAT workshop series.
The Belle II Silicon Vertex Detector Friedl, M.; Ackermann, K.; Aihara, H. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2013, Volume:
732
Journal Article
Peer reviewed
Open access
The KEKB machine and the Belle experiment in Tsukuba (Japan) are now undergoing an upgrade, leading to an ultimate luminosity of 8×1035cm−2s−1 in order to measure rare decays in the B system with ...high statistics.
The previous vertex detector cannot cope with this 40-fold increase of luminosity and thus needs to be replaced. Belle II will be equipped with a two-layer Pixel Detector surrounding the beam pipe, and four layers of double-sided silicon strip sensors at higher radii than the old detector. The Silicon Vertex Detector (SVD) will have a total sensitive area of 1.13m2 and 223,744 channels—twice as many as its predecessor.
All silicon sensors will be made from 150mm wafers in order to maximize their size and thus to reduce the relative contribution of the support structure. The forward part has slanted sensors of trapezoidal shape to improve the measurement precision and to minimize the amount of material as seen by particles from the vertex. Fast-shaping front-end amplifiers will be used in conjunction with an online hit time reconstruction algorithm in order to reduce the occupancy to the level of a few percent at most. A novel “Origami” chip-on-sensor scheme is used to minimize both the distance between strips and amplifier (thus reducing the electronic noise) as well as the overall material budget.
This report gives an overview on the status of the Belle II SVD and its components, including sensors, front-end detector ladders, mechanics, cooling and the readout electronics.
We present the concept of a track trigger for the Belle II experiment, based on a neural network approach, that is able to reconstruct the z (longitudinal) position of the event vertex within the ...latency of the first level trigger. The trigger will thus be able to suppress a large fraction of the dominating background from events outside of the interaction region. The trigger uses the drift time information of the hits from the Central Drift Chamber (CDC) of Belle II within narrow cones in polar and azimuthal angle as well as in transverse momentum (sectors), and estimates the z-vertex without explicit track reconstruction. The preprocessing for the track trigger is based on the track information provided by the standard CDC trigger. It takes input from the 2D (r - ) track finder, adds information from the stereo wires of the CDC, and finds the appropriate sectors in the CDC for each track in a given event. Within each sector, the z-vertex of the associated track is estimated by a specialized neural network, with a continuous output corresponding to the scaled z-vertex. The input values for the neural network are calculated from the wire hits of the CDC.
Admiral Raoul Castex is France's most important modern naval strategist. Military historian Eugenia Kiesling offers the essence of Castex's original five volume study, Théories Stratégiques, in a ...useful one-volume abridgment and a very readable translation. It emphasizes the admiral's method of strategic analysis while omitting most of the chapters of historical narrative. Included are chapters defining strategy and relating it to policy and geography, analyzing the role of maritime forces and the significance of command at sea, prescribing a theory of conduct of operations, and introducing Castex's favorite themes: strategic manoeuvre, stratégie générale, and the theory of “perturbation”. Two narrative chapters on German operations in the North Sea from 1914 to 1916 remain as examples of the author's historical style. The introduction places Castex's work in four distinct contexts: the international debate among naval theorists on the nature and importance of “command at sea,” the controversy within France between advocates of the “historical” and “material” schools of naval strategy, the contemporary concern over coordinated naval strategy for total war, and his contribution to the formulation of French strategy between the world wars. In an era of expanding global responsibilities and shrinking national economies, Castex's balanced view of naval power offers many insights for today's new generation of naval thinkers.
We present a determination of the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element |Vcb| using the decay B → Dℓνℓ (ℓ = e,μ) based on 711 fb–1 of e+e– → Υ(4S) data recorded by the Belle ...detector and containing 772 × 106 BB¯ pairs. Here, 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+ or D0 meson in a total of 23 hadronic decay modes. The isospin-averaged branching fraction of the decay B → Dℓνℓ is found to be B(B0 → D–ℓ+νℓ) = (2.31 ± 0.03(stat) ± 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 G(1) = 1.0541 ± 0.0083 calculated by FNAL/MILC, we obtain ηEW|Vcb| = (40.12 ± 1.34) × 10–3, where ηEW 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 ηEW|Vcb| = (41.10 ± 1.14) × 10–3.
We discuss several popular statistical learning methods used in high-energy- and astro-physics analysis. After a short motivation for statistical learning we present the most popular algorithms and ...discuss several examples from current research in particle- and astro-physics. The statistical learning methods are compared with each other and with standard methods for the respective application.
We present a search for lepton-flavor-violating τ decays into three leptons (electrons or muons) using 782 fb−1 of data collected with the Belle detector at the KEKB asymmetric-energy e+e− collider. ...No evidence for these decays is observed and we set 90% confidence level upper limits on the branching fractions between 1.5×10−8 and 2.7×10−8.
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