E. Won

Belle DAQ system upgrade at 2001

Abstract We renewed the data acquisition system for the Belle experiment. Previous data acquisition system, which has been used since December 1998, did not have level 2 trigger facility. To improve the data reduction factor and total throughput, we replaced event builder, online computer farm and the storage system. The event builder and online computer farm are unified into one system. This event building farm uses commodity hardware and newly appended level 2 trigger functionality. This data acquisition system started its operation since last autumn and is very stable. We took 36 fb −1 with new DAQ system, it had already overtaken 30 fb −1 that is total amount of previous DAQ system.

Large dynamic range photon detector with a temperature-stabilized Si-based multi-pixel photon counter

We present an efficient fluorescence detector in the visible region of the spectrum with a photon detection dynamic range over 10 (6) photons/s made of a temperature-stabilized Si-based multi-pixel photon counter at temperature down to 5 degrees C. We show that effective cooling of the device by means of a compact thermo-electric cooler brings several advantages, such as high gain, low dark noise rate, and thus high signal-to-noise ratio in the efficient fluorescence detection at 398.9 nm from the (1)S(0) ? (1)P(1) transition of the ytterbium atoms in an effusive atomic beam. We present also a comparison of the fluorescence detection efficiencies between the device and a side-on photo-multiplier tube with known gain positioned at the symmetric location from the ytterbium atomic beam.

Level 1 Trigger System for the Belle II Experiment

The super-KEKB B factory, currently under construction at the KEK High Energy Accelerator Research Organization in Japan, has a goal of producing 50 ab-1 of integrated luminosity, thus allowing the Belle II experiment to study rare decays of B mesons, D mesons, and τ leptons. Such large statistics on these decays provide an experimental probe of physics beyond the Standard Model. An online trigger system is indispensable to Belle II to reduce the number of beam background events associated with high electron and positron beam currents, as well as to enhance physics-oriented events. For this purpose, we have designed the Belle II online trigger system with two kinds of primary Level 1 trigger components: a track trigger and an energy trigger. The track trigger is composed of 2-dimensional and 3-dimensional tracking algorithms, and the energy trigger implements algorithms based on total energy, isolated clusters, and identification of Bhabha events. In addition, precise event trigger timing and muon tagging information are provided by the time-of-propagation detector and iron flux return muon detector, respectively.

Upgrade of the Level 1 Global Trigger System in the Belle Experiment

In this paper, we describe design and development of the new global decision logic units for the Belle detector at the KEK B-factory. The new units consist of two identical 9U VME modules which are designed using the programmable logic techniques. Each module has an inexpensive programmable logic device that has high density input and output lines. Performance tests of these new modules and existing system are compared and showed good results. Utilizing the nature of the logic device on the board, we also examine possibility of the implementation of an artificial neural network algorithm to the new trigger board for a more efficient data acquisition.

A software framework for pipelined arithmetic algorithms in field programmable gate arrays

Abstract Pipelined algorithms implemented in field programmable gate arrays are extensively used for hardware triggers in the modern experimental high energy physics field and the complexity of such algorithms increases rapidly. For development of such hardware triggers, algorithms are developed in C++ , ported to hardware description language for synthesizing firmware, and then ported back to C++ for simulating the firmware response down to the single bit level. We present a C++ software framework which automatically simulates and generates hardware description language code for pipelined arithmetic algorithms.

Three-dimensional fast tracker for the central drift chamber based level-1 trigger system in the Belle II experiment

The Belle II detector at the SuperKEKB accelerator has a level-1 trigger implemented in field-programmable gate arrays. Due to the high luminosity of the beam, a trigger that effectively rejects beam-induced background is required. A three-dimensional tracking algorithm for the level-1 trigger that uses the Belle II central drift chamber detector response is being developed to reduce the recorded beam background while having a high efficiency for physics of interest. In this paper, we describe the three-dimensional track trigger that finds and fits track parameters that we developed.

A Proposed Muon Facility in RAON/Korea

Muons were discovered by Carl D. Anderson and Seth Neddermeyer at Caltech in 1936 [1] and later confirmed in 1937 [2]. Since then, the parity and charge conjugation violation in the decay of muons were discovered by Garwin, Lederman, and Weinrich [3]. The potential applications of polarized muons to condensed matter science were recognized by authors in the paper [3], by stating that “It seems possible that polarized positive and negative muons will become a powerful tool for exploring magnetic fields in nuclei, atoms and interatomic regions”. Their idea is later realized in many places now and this technique is commonly called the muon spin relaxation, rotation, and resonance (μSR from now on) [4]. At present, world-leading μSR facilities include Paul Scherrer Institute (PSI) in Switzerland, Tri-University Meson Facility (TRIUMF) in Canada, and Japan Proton Accelerator Research Complex (J-PARC) in Japan. These facilities provide continuous or pulsed polarized muons and depending on the purpose of the condensed matter science applications, one method is more appropriate than the other. On the other hand in the particle physics community, a long-waited discovery of Higgs particle is finally made in 2012 [5]. But unfortunately its properties are consistent with the prediction from the standard model of particle physics so far, indicating that there is a strong need to look at much higher energy scale than the energy scale that Large Hadron Collider (LHC) facility can directly look at, in order to look for the particle physics beyond standard model [6]. One way of looking at the higher energy scale experimentally is to look at charged lepton flavor violations (cLFV from now on) and muon is one of the most promising systems to look at cLFV at this moment. A rare isotope accelerator is under construction since 2012 in the Republic of Korea, near Daejeon city that is located at the central part of Korean pennsula [7]. We, a small group of high energy physicists is proposing a muon facility utilizing this rare isotope accelerator in order to realize a μSR facility for the first time in Korea and to realize a cLFV experiment also for the first time in Korea. In this presentation, first the major science goals of the project are discussed briefly, and a proposed muon facility for both μSR and cLFV science will be discussed.

GroundBIRD: observations of CMB polarization with fast scan modulation and MKIDs

Polarized patterns in the cosmic microwave background (CMB) radiation contains rich knowledge for early stage of the universe. In particular their odd-parity patterns at large angular scale (> 1°), primordial B-modes, are smoking-gun evidence for the cosmic inflation. The GroundBIRD experiment aims to detect these B-modes with a ground-based apparatus that includes several novel devices: a high-speed rotational scan system, cold optics, and microwave kinetic inductance detectors (MKIDs). We plan to start observations in the Canary Islands in 2017. In this paper, we present the status of the development of our instruments. We established an environment that allows operation of our MKIDs in an optical configuration, in which the MKIDs observe radiations from the outside of the telescope aperture. We have also constructed MKID prototypes, and we are testing them in the optical configuration.

Belle-II high level trigger at SuperKEKB

A next generation B-factory experiment, Belle II, is now being constructed at KEK in Japan. The upgraded accelerator SuperKEKB is designed to have the maximum luminosity of 8 × 1035 cm−2s−1 that is a factor 40 higher than the current world record. As a consequence, the Belle II detector yields a data stream of the event size ~1 MB at a Level 1 rate of 30 kHz. The Belle II High Level Trigger (HLT) is designed to reduce the Level 1 rate to 1/5 by performing the real time full event reconstruction and by applying the physics level event selection as the software trigger. In this paper, the development of the high level trigger system for Belle II and its performance is discussed.