117118383
Sigma-hypernuclei with stopped kaons
122600834
Muon catalyzed fusion experiments on muonic deuterium atom deceleration in thin solid deuterium films
Abstract Muon catalyzed fusion was investigated in a series of thin solid deuterium films by detecting protons from dd fusion. Two different contributions to the total fusion yield resulting from dμ atoms emitted from a primary hydrogen layer and from incident muons directly stopped in the deuterium film itself were observed. The thickness dependence of the fusion yield suggested the importance of molecular effects in dμ elastic scattering in D 2 .
124815658
Measure of the spatial size for the monopole excitation in proton scattering
124123633
SEARCH FOR LORENTZ AND CPT VIOLATION EFFECTS IN MUON SPIN PRECESSION
121882195
Discovery of the repulsive energy shift of the kaonic hydrogen 1s state
Abstract The aim in this manuscript is to clarify the progress in understanding the nature of the K ¯ N interaction at the lowest energy, given by the recent kaonic hydrogen X-ray experiment at KEK [1]. We have observed a clear spectrum showing the kaonic hydrogen K α line, for the first time. The analysis gives the repulsive energy shift to be Δ E (1 s ) = −323 ± 63(statistical) ± 11 (systematic) eV and the energy width to be Λ(1 s ) = 407 ± 208 ± 100 eV. This result is consistent with analyses of the previous low-energy scattering data and resolves the long-standing kaonic hydrogen puzzle.
117791711
Radioactive Muonic Atom Studies with Intense Muon Beams
New intense muon beams with flux several orders of magnitude higher than at present muon facilities would allow many novel experimental studies that were until now statistically not feasible. The investigation of the nuclear properties of short‐lived nuclei using muonic atom spectroscopy would become possible. In this paper, the recent progress of a feasibility study at RIKEN‐RAL muon facility using the cold hydrogen film method to produce radioactive muonic atoms is being reported. The first experimental results have just been obtained with stable argon ions implanted in solid deuterium films.
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.
119756253
R&D status of a large-aperture hybrid avalanche photo-detector
This paper reports on the R&D status of a large-aperture Hybrid Avalanche Photo-Detector (HAPD). We have developed a 13-inch aperture HAPD and its readout system. The HAPD is a photo-detector expected to replace the photomultiplier tube (PMT) in next-generation imaging water Cherenkov detectors such as Hyper Kamiokande. We will present the recent progress made in readout system development. The readout system involves a fast sampling device. The sampling depth (number of cells) has been extended to 256 from 64 in order to measure longer waveform length. The variation in AC gain is now fixed and the input analog bandwidth improved.
120221589
Hartree-Bogoliubov Theory of Quark Matter: Condensation Energy in Strange Quark Matter
185755181
The SuperKEKB accelerator status
123251544
Thermodynamic Properties of Color Superconducting Quark Matter
Thermodynamics for color superconducting quark matter is investigated on the basis of the one-gluon-exchange model. Thermodynamic quantities are calculated by using a mean field (BCS) approximation. It is shown that there exists a phase transition of second order between the superconducting phase and normal phase. The pressure and density become larger in the superconducting phase. The specific heat and compressibility have a discontinuity at the critical temperature.