55994477
BEAM BACKGROUND AND MDI DESIGN FOR SUPERKEKB/BELLE-II
The Belle experiment, operated at the asymmetric electron-positron collider KEKB, had accumulated a data sample with an integrated luminosity of more than 1 ab −1 before the shutdown in June 2010. We have started upgrading both the accelerator and the detector, SuperKEKB and Belle-II, to achieve the target luminosity of 8 × 10 35 cm −2 s −1 . With the increased luminosity, the beam background will be severe. The development of MachineDetector Interface (MDI) design is crucial to cope with the increased background and protect Belle-II detector. We will present the estimation of impact from each beam background sources at SuperKEKB and our countermeasures for them, such as collimators to stop Touschek-scattered beam particles, Tungsten shield to protect inner detectors from shower particles, and dedicated beam pipe design around interaction point to stop synchrotron radiation, etc.
56000332
PROGRESS OF DESIGN STUDY OF INTERACTION REGION QUADRUPOLES FOR THE SUPER-KEKB
For KEKB upgrade, we are studying the design of the final focus quadrupoles to achieve very small β-functions at the interaction point (IP). For each beam, the final beam focusing system consists of quadrupole-doublet of the superconducting and permanent magnets. In this paper, the design progress of final focusing magnets is reported.
16601897
Mechanisms affecting performance of the BaBar resistive plate chambers and searches for remediation
The BaBar experiment at PEPII relies on the instrumentation of the flux return (IFR) for both muon identification and KL detection. The active detector is composed of resistive plate chambers (RPCs) operated in streamer mode. Since the start of operation the RPCs have suffered persistent efficiency deterioration and dark current increase problems. The ‘‘autopsy’’ of bad BaBar RPCs revealed that in many cases uncured linseed oil droplets had formed on the inner surface of the Bakelite plates, leading to current paths from oil ‘‘stalagmites’’ bridging the 2mm gap. In this paper, a possible model of this ‘‘stalagmite’’ formation and its effect on the dark current and efficiency of RPC chambers is presented. Laboratory test results strongly support this model. ARTICLE IN PRESS *Corresponding author. Tel.: +1-609-258-4391; fax: +1-609-258-6360. E-mail address: changguo@princeton.edu (C. Lu). 0168-9002/03/$ see front matter r 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0168-9002(03)01292-0 Based upon this model we are searching for solutions to eliminate the unfavorable effect of the oil stalagmites. The lab tests show that the stalagmite resistivity increases dramatically if exposed to the air, an observation that points to a possible way to remedy the damage and increase the efficiency. We have seen that flowing an oxygen gas mixture into the chamber helps to polymerize the uncured linseed oil. Consequently, the resistivity of the bridged oil stalagmites increases, as does that of the oil coating on the frame edges and spacers, significantly reducing the RPC dark currents and low-efficiency regions. We have tested this idea on two chambers removed from BaBar because of their low efficiency and high dark current. These test results are reported in the paper, and two other remediation methods also mentioned. We continue to study this problem, and try to find new treatments with permanent improvement. r 2003 Elsevier Science B.V. All rights reserved.
185755181
The SuperKEKB accelerator status
55994477
BEAM BACKGROUND AND MDI DESIGN FOR SUPERKEKB/BELLE-II
The Belle experiment, operated at the asymmetric electron-positron collider KEKB, had accumulated a data sample with an integrated luminosity of more than 1 ab −1 before the shutdown in June 2010. We have started upgrading both the accelerator and the detector, SuperKEKB and Belle-II, to achieve the target luminosity of 8 × 10 35 cm −2 s −1 . With the increased luminosity, the beam background will be severe. The development of MachineDetector Interface (MDI) design is crucial to cope with the increased background and protect Belle-II detector. We will present the estimation of impact from each beam background sources at SuperKEKB and our countermeasures for them, such as collimators to stop Touschek-scattered beam particles, Tungsten shield to protect inner detectors from shower particles, and dedicated beam pipe design around interaction point to stop synchrotron radiation, etc.
54880563
Design and Status of the SuperKEKB Accelerator Control Network System
We have upgraded the accelerator control network system for SuperKEKB, the next generation B-factory experiment in Japan. The designed network system has the higher performance based on the wider bandwidth data transfer, and more reliable and redundant configuration. For the SuperKEKB beamline construction and accelerator components maintenance, we have installed the new wireless network system consists with the Leaky Coaxial (LCX) cable antennas and collinear antennas into the 3 km circumference accelerator tunnel. In this paper, we describe the design and current status of the SuperKEKB accelerator control network system.
123376999
Development of a super-fluid 4He target system for an experimental search for nuclear K¯ states
Abstract A super-fluid He 4 target system has been successfully developed to experimentally search for deeply bound K ¯ nuclei. From the experimental requirements, the amount of material around the liquid-helium target was drastically suppressed by using two approaches. One was to utilize the properties of super-fluid helium of extremely high thermal conductivity and low vapor pressure. The other was to develop a thin-walled CFRP vacuum chamber and a PET-based target cell. The wall thickness of the CFRP vacuum chamber was only 0.9 mm with the inner diameter of 310 mm. The dimensions of the target cell were 200 mm inner diameter and 150 mm length with the volume of 4.7 l, and it equipped 75 μ m thick beam windows made of a PET film. The present target system achieved a temperature of 1.3 K, and was stably operated throughout the experiment with the operational pressure below 40 mbar and a liquid-helium consumption rate of 45 l / day .
123052618
Instability of the Chiral Quantum Baryon
The chiral quantum baryon which is stabilised by the quantum effect is discussed within the nonlinear σ-model with the pion mass term. It is shown that the quantum baryon does not exist mathematically even if the pion mass term is taken into account
15085801
Search for a kaonic nuclear state via 4He(K−, N) reaction at rest
Very recently, we have performed a couple of experiments, KEK PS-E549/E570, for the detailed study of the strange tribaryon S 0(3115) obtained in KEK PS-E471. These experiments were performed to accumulate much higher statistics with improved experimental apparatus especially for the better proton spectroscopy of the 4He(stopped K −, N) reaction. In contrast to the previous proton spectrum, no narrow (∼ 20 MeV) peak structure was found either in the inclusive 4He(stopped K −, p) or in the semi-inclusive 4He(stopped K −, pX ±) reaction channel, which is equivalent to the previous E471 event trigger condition. Detailed analysis of the present data and simulation shows that the peak, corresponding to S 0(3115), has been an experimental artifact. Present analysis does not exclude the possible existence of a much wider structure. To be sensitive to such structure and for better understanding of the non-mesonic K − absorption reaction channel, detailed analysis of the data is in progress.
119990534
Muon density enhancement with a tapered capillary method
The focusing effect of a muon beam with a tapered capillary method has been investigated in a range from 4.2 MeV to 9.2 MeV (i.e. from 30 MeV/c to 45 MeV/c in momentum). We injected the muon beam into a pair of narrowing (tapered) plates and tubes made of glass, copper and gold‐coated copper, and measured the energy distribution of the muon leaving from the outlet. The plates were tilted from an inlet of 40 mm to an outlet of 20 mm. The density enhancement was more prominent with the plates made of heavier elements. The largest beam density enhancement at 10 mm downstream of the outlet was 1.3 with the gold‐coated copper narrowing plates. The enhancement was composed of muons scattered with a small angle. Their energy was slightly less than that of the initial beam. This effect did not depend on the surface roughness. The result strongly suggests a simple and effective way to increase the muon beam density for a small target.
123947708
A Search for Deeply-bound Kaonic Nuclear States by In-flight $^3$He($K^-, n$) Reaction at J-PARC
F. Sakuma, S. Ajimura, G. Beer, H. Bhang, M. Bragadireanu P. Buehler, L. Busso, M. Cargnelli, S. Choi, C. Curceanu S. Enomoto, D. Faso, H. Fujioka, Y. Fujiwara, T. Fukuda C. Guaraldo, T. Hashimoto, R.S. Hayano, T. Hiraiwa, M. Iio M. Iliescu, K. Inoue, Y. Ishiguro, T. Ishikawa, S. Ishimoto T. Ishiwatari, K. Itahashi, M. Iwai, M. Iwasaki, Y. Kato S. Kawasaki, P. Kienle, H. Kou, Y. Ma, J. Marton, Y. Matsuda Y. Mizoi, O. Morra , T. Nagae, H. Noumi, H. Ohnishi, S. Okada H. Outa, K. Piscicchia, M. Poli Lener, A. Romero Vidal Y. Sada, A. Sakaguchi, M. Sato, A. Scordo, M. Sekimoto, H. Shi D. Sirghi, F. Sirghi, K. Suzuki, S. Suzuki, T. Suzuki K. Tanida, H. Tatsuno, M. Tokuda, D. Tomono, A. Toyoda K. Tsukada, O. Vazquez Doce, E. Widmann, B.K. Wuenschek T. Yamaga, T. Yamazaki, H. Yim, Q. Zhang, J. Zmeskal