125625632
EVALUATION OF THE DETECTOR BG FOR SuperKEKB
SuperKEKB is the upgrade plan of the current B-factory experiment with the KEKB accelerator at KEK. Its luminosity is designed to be 8×1035/cm2/s (40 times higher than KEKB) and the integrated luminosity is expected to be 50 ab−1. In SuperKEKB, it is important to evaluate the beam induced BG and design the interaction region (IR) to assure the stable detector operation. To estimate the beam induced BG, we construct the beam-line simulation based on the GEANT4 simulation. To study the particle BG features, we did the background studies during the 2009 fall Belle runs. In this paper, we report the BG evaluation for SuperKEKB. IR DESIGN FOR SUPERKEKB For the next generation B-factory experiment in Japan, SuperKEKB, the high luminosity e+e− asymmetric collider at the B mesons CM energy, is planed as an upgrade of the current KEKB [1]. It is designed to achieve a luminosity of 8×1035/cm2/s, 40 times higher than the highest luminosity record at KEKB, by employing higher beam currents and smaller interaction point (IP) beam sizes. For SuperKEKB, we deign that the 7 GeV electrons stored in the high-energy ring (HER) and the 4 GeV positrons in the low-energy ring (LER) collide at IP with a finite crossing angle of 83 mrad. The large crossing angle helps to separate quickly the two beams and to position the final quadrupole magnets closer to IP to achieve small β-functions at IP. We have separated quadrupole magnets for the two beams on each side in this design. Parameters are listed in Table 1, here x and y directions are defined as the horizontal and vertical directions, respectively. In the higher luminosity machine operations, the higher beam-induced background to the Belle II detector is expected. To assure the stable detector operations under such high luminosity experiments, the IR design based on the beam-induced background estimations compared to the present level is important. In this paper, we discuss the expected beam-induced background at SuperKEKB. Note that all expectations strongly depend on the beam optics. Then the numbers will be updated after fixing the beam optics and the IR design. ∗masako.iwasaki@kek.jp Table 1: SuperKEKB Beam Parameters LER HER Unit Beam Energy 4.0 7.0 GeV β∗ x / β ∗ y 32 / 0.27 25 / 0.41 mm x / y 3.2 / 12.8 2.4 / 8.4 nm / pm IP beam size (x) 10.2 7.75 μ m IP beam size (y) 0.059 0.059 μ m Bunch length 6 5 mm Beam current 3.60 2.62 A Crossing angle 83 mrad Luminosity 8× 10 cm−2 s−1 EVALUATION OF POSSIBLE BEAM-INDUCED BACKGROUNDS In this section, we describe the possible background sources in SuperKEKB: synchrotron radiation (SR) from upstream of the high energy ring (HER), backscattering of SR from HER downstream, scattering of the beam on residual gas1, Touschek scattering, radiative Bhabha scattering, and electron-positron pair production via the two photon process e+e− → e+e−e+e−. SR from Upstream (SR Upstream) It is important to evaluate the upstream SR background to design the IP-chamber to protect the inner detectors of the pixel detector(PXD) and the silicon vertex detector (SVD). Here we design the IP-chamber to avoid the direct SR hit from HER to the detector. Figure 1 shows a rough sketch of the current IP-chamber design for SuperKEKB. The baseline design of the IP chamber is similar to the current IP-chamber [2]. In SuperKEKB, as shown in the figure, there are crotched structures both left and right sides, since IP chamber is connected to the two separate quadrupole magnets in both ends. In SuperKEKB, the polarity of the last bend is designed so that SR fan from the bend do not directly hit the central part of the IP chamber. Then we expect SR from the last bend is stopped by the crotched part. For further detailed estimations, we also perform GEANT4 based beam1In what follows, we will use the expression ’beam-gas scattering’ or just ’beam-gas’ for this kind of scattering. Proceedings of IPAC’10, Kyoto, Japan TUPEB019 01 Circular Colliders A02 Lepton Colliders 1557 Figure 1: Picture of IP chamber. line simulations, since the SR background level depends on the HER current, beam-optics (magnet positions, magnetic field strength, and beam orbits), and the geometry of the IR components. As a result, no direct SR hits from HER are expected by assuming the current beam optics and IPchamber design. Backscattering of SR from Downstream (SR Backscattering) The final focusing magnet for the HER downstream side is called ’QCS-R’, where R stands for the right hand side. The magnet QCS-R provides the final focusing of the LER beam. In the current KEKB case, it also works as a bending magnet to separate the outgoing HER beam from the LER. Then, strong SR is emitted because of this bending. These strong SR emissions once destroyed the SVD. On the other hand, in SuperKEKB case, two separate quadrupole magnets are located in both R and L sides, and beam orbits of both incoming and outgoing beams are on center of the magnets. Then we expect much lower background than current KEKB. Based on the optics calculations, we expect 1/800 of the current KEKB backscattering SR at SuperKEKB. To confirm this, careful simulation studies will also be necessary after fixing the beam optics.
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.
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.
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.
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.
22969599
Conceptual design of a radial vane silicon tracker for a new measurement of the muon anomalous magnetic moment g-2 and electric dipole moment at J-PARC
A new measurement of the anomalous magnetic moment (g-2) and electric dipole moment (EDM) of the positive muon at J-PARC is proposed. In this experiment, we plan to use a radial vane silicon detector for detecting muon decay positrons. Specification and design study of the detector has been promoted. In order to determine detector parameters, we are developing simulation and positron track reconstruction tools. First version of those using Geant4 and Hough transform method in ideal condition was constructed. We are improving these tools close to real condition and the multi-track finding efficiency has been investigated. In this paper, we report the progress of the studies in simulation and track finding tools for the optimization of the detector parameters.
120551306
Experimental Search for Kaonic Nuclear Bound States in the 4He(stopped K-,n) Reaction
We made an experimental search for deeply bound kaonic nuclear states ppnK - in 4 He(stopped K - , n) reaction. The experiment is performed in September and October 2002 and the analysis is in progress. The experimental procedure and the present status of the analysis are described.
123013869
An Application of the Glauber Approximation to High Energy Heavy-Ion Collisions. I Theoretical Formulation
122423259
RESULTS FROM THE MUON G-2 EXPERIMENT
37764222
Specification and design of a radial vane silicon tracker for a new measurement of the muon anomalous magnetic moment g-2 and electric dipole moment at J-PARC
A new measurement of the anomalous magnetic moment (g-2) and electric dipole moment (EDM) of the positive muon at J-PARC is proposed. In this experiment, we plan to use a radial vane silicon detector for detecting muon decay positrons. Specification and design study of the detector has been promoted. In order to confirm validity of use of the radial vane silicon detector and decide detector parameters, we are developing simulation and positron track reconstruction tools. First version of those using Geant4 and Hough transform method in ideal condition was constructed and the track finding efficiency was investigated. In parallel, for understanding the detector response, we began to test the most recent double sided silicon strip detector in existence. In this paper, we report the progress of the simulation and the experimental studies for the optimization of the detector parameters.