125753081
Magnetic Field Measurement System for the SuperKEKB Final Focus Superconducting Magnets
SuperKEKB final beam focusing system consists of different types of superconducting magnets: 8 quadrupole magnets, 4 solenoids and 43 corrector coils. In order to measure the field performances of the magnets and the coils, KEK prepared one set of harmonic coil system during the production stage in a factory, and two sets of harmonic coil systems for the cold tests at 4K for the vertical cryostat test stand in KEK. In this paper, we report these magnetic field measurement systems
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.
13435498
Study of top-quark production and decay vertices with LCD fast simulation
We report a study of top-quark reconstruction in e+e−→tt events at a 500 GeV linear collider using the LCD Fast simulator. The initial study of top-quark anomalous couplings is also reported. The final states of 4 jets and lepton as well as 6 jets are used. Using the 4 jets and lepton final state, we estimate the preliminary sensitivities for form factors at the γ/Z0tt vertex. In the 6 jets reconstruction, we show abilities of the top-quark charge identification and the c-quark tagging in W decays.
15071400
LCD ROOT simulation and analysis tools
The North American Linear Collider Detector group has developed a simulation program package based on the ROOT system. The package consists of Fast simulation, the reconstruction of the Full simulated data, and physics analysis utilities.
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.
122815017
Statistical equations and methods applied to the precision muon (g-2) experiment at BNL
Abstract In the muon ( g - 2 ) experiment at Brookhaven National Laboratory, the spin precession frequency ω a is obtained from a standard χ 2 minimization fit applied to the time distribution of decay electrons. The unusually high accuracy ( ∼ 0.5 ppm ) of the experiment puts stringent requirements on the quality of the fit and the level of understanding of the statistical properties of the fitted parameters. We discuss the properties of the fits and their implications on the derived value for ω a , including estimates of the effect of an imperfect fit function, methods of including additional external information to reduce the error, the effects of splitting the data into many smaller subsets of data, applying different weighting methods to the data using energy information, and various tests of data suitability.
118407007
Recent Development of a point positive muon source at the RIKEN‐RAL muon facility
We report recent progress of slow muon beam line constructed at the RIKEN‐RAL muon facility. The slow muons are muons which are re‐accelerated from the one at thermal velocity. This beam is expected to have very small emittance compared with conventional muon beam, where muons are obtained from decays of pions at rest or on move. Especially, its smallness of energy spread will make it possible to apply μSR technique to the studies of thin films, multilayered systems, nanomaterials, and other objects of restricted dimensionality. Intense slow muon beams which can be realized at future neutrino factories will be a valuable tool for material science.
122256238
Kaonic hydrogen X-ray experiment at KEK
Abstract For the further understanding of the K -N interaction in the low energy region, we are performing a measurement of K − p X rays at KEK which adopts a new technique to improve the signal-to-background ratio (S/N); specifying the final state of the K − p reaction and using a gaseous hydrogen target (4 atm at 100 K). With this technique three orders of magnitude better S/N and one order higher statistics are expected as compared to previous experiments.
104275874
Spectroscopy of $\eta '$ mesic nuclei using $(p,d)$ reaction
122361271
Progress in development of new μSR spectrometer at RIKEN-RAL
A new μSR spectrometer has been developed at the RIKEN-RAL Muon Facility, UK. The spectrometer comprises two significantly advantageous devices of accurate magnets and multi-channel counter system for efficient use of the highly intense muon beam. A commissioning test to commence operation is in progress toward new μSR experiments under various conditions.