67846515
A Modified Glauber Approximation and the Formation of Shock Waves in High-Energy Heavy Ion Collisions
Coherent features in high energy heavy ion collisions are investigated from a microscopic viewpoint. A modified Glauber approximation which enables us to include the slowing down of the relative motion between the centers of masses of both nuclei is presented. The generation of the shock wave is shown to be suppressed by this slowing down effect. As an application inclusive nucleon spectra and the two-particle correlation are calculated in the case of Ne+U collision at 400 Me V! A. l ) (which are referred to as I hereafter) we investigated a possible microscopic mechanism for shock wave generation in high energy heavy ion collisions. The nuclear excitation induced by a nuclear collision was de­ scribed in terms of phonons. It was shown that as the collision proceeds phonons are coherently excited and show a characteristic feature of the shock wave. In this treatment the action of the projectile on the target was replaced by that of a potential moving with a constant velocity. We may construct this potential by superposing the nucleonic potential between projectile nucleons and the target ones with amplitudes of nucleonic states in both nuclei. To treat both systems equally from a microscopic viewpoint, one of the authors (M.I) proposed a formalism which is essentially an application of the Glauber approximation to the process. 2 ) The assembly of nucleons in the projectile nucleus was assumed to move in a group during the collision and the Glauber approximation was applied to the relative motion between the centers of masses of the projectile and the target nucleus. In this treatment the deceleration of the relative motion due to the nuclear excitation was not taken into account. In this paper we extend the Glauber approximation so as to take into account the slowing down of the relative motion. In § 2 the formulation of the modified Glauber approximation is presented.
118969678
Tetraquark particle in the string model
We discuss the possibility of the existence of tetraquark states made of four quarks in the string (flux tube) model. The new particle is composed of a diquark and an antidiquark which are connected by a color flux. It is shown that the vibrational and rotational excited states of the string explain some non-qq mesons observed experimentally. Moreover we discuss the decay widths of such tetraquarks with the use of the Schwinger mechanism.
119408373
Fluctuation modes in color-superconductors
We investigate fluctuation effects of a gap parameter in color-superconductors. The fluctuation modes in the super phase are described by two scalar fields of diquarks. One of them is a Nambu-Goldstone boson and the other is a diquark boson whose mass is about twice of the gap energy (an extended quasi-supersymmetry). In the normal phase the fluctuation becomes a precursory (soft) mode whose amplitude increases near the critical temperature.
120691222
Superconductivity of Quark Matter at Finite Temperature
25502171
Rotating Bag Model for Hadrons
The MIT bag model!) has been quite successful in reproducing the observed masses and other static properties of the low-lying hadrons. It is very important to discuss whether or not excited states of the hadrons (resonances) can be explained in the framework of the bag model. A number of excited states have been described successfully by considering collective excitations of the bag.) In particular, Johnson and Thorn) investigated a series of excited states known as the Regge trajectory by using the rotating bag model. They assumed that the rotating bag has stringlike shape with two ends by the centrifugal force and the transverse length is negligible compared with its longitudinal one. From this onedimensional bag model, they succeeded in reproducing the experimental value of the Regge slope very well. Furthermore it was showt: by Wakimaru and one of the present authors (M. I.) that this simple model can explain not only the Regge slope but also the energy spectra of the trajectories.) On the other hand, Eguchi and Migdal et aJ.5) also discussed the excited states by using their string models 'which are independent of the bag model. Any string model which has been proposed is based on the assumption that the shape is stringlike or one-dimensional. Is the assumption of the stringlike shape, however, surely true? section of the stringlike bag, which we call tube, can be given by
123223657
A Vibrational Bag Model for Baryons
Surface monopole vibration of baryons is investigated on the basis of the soliton bag model. We derive a relativistic Lagrangian for the surface motion whose mass parameter is proportional to square of the bag radius. With the use of the WKB approximation, the energy spectra of Pl1 and F" resonances are reproduced by our model fairly well. The static properties of the nucleon are alsO studied in our vibrational bag model and compared with those of the static bag model. Our model predicts that the nucleon consists of the central high·density part and the surrounding low-density part. It is also shown that our model is capable to predict the experimental data as well as the static bag model.
56017544
New precision era of experiments on strong interaction with strangeness at DAFNE/LNF-INFN
The strong-interaction shifts and widths of kaonic hydrogen, deuterium, 3 He, and 4 He were measured in the SIDDHARTA experiment. The most precise values of the shift and width of the kaonic hydrogen 1s state were determined to be ϵ1s = −283 ± 36(stat) ±6(syst) eV and Γ1s = 541 ±89(stat) ±22(syst) eV. The upper limit of the kaonic deuterium Kα yield was found to be ≤ 0.39%. In addition, the shifts and widths of the kaonic 3 He and 4 He 2p states were determined to be ϵ2p( 3 He) = −2 ± 2(stat) ± 4(syst) eV and Γ2p( 3 He) = 6 ± 6(stat) ± 7(syst) eV; ϵ2p( 4 He) = +5 ± 3(stat) ± 4(syst) eV and Γ2p( 4 He) = 14 ±8(stat) ±5(syst) eV. These values are important for the constraints of the low-energy ¯ KN interaction in theoretical approaches.
119761366
Ultra Slow Muon Microscope at MUSE / J-PARC
We report current constructing states of the Ultra Slow Muon Beam at U-line / MUSE / J-PARC, which are supported by thermal muonium (Mu, μ+e−) production with the most intense pulsed slow muon beam, laser resonant ionization, and transportation of Ultra Slow Muon Beam. A thermal Mu is produced by a hot tungsten foil in a Mu-production chamber. At the laser resonant ionization process, a thermal Mu is ionized by coherent vacuum ultraviolet radiation and coherent 355-nm radiation. The coherent radiation sources are developed at RIKEN, installed in a laser cabin, and connected via a VUV steering chamber with the Mu-production chamber.
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 .
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.
120844992
J-PARC Muon Science Facility with use of 3 GeV Proton Beam
The J-PARC muon science experimental area is planned to be located in the integrated building of the facility for materials and life science study. One muon target will be installed upstream of the neutron target in Phase 1. Under the limited budget of phase 1, it is not possible to install all the secondary beam lines, therefore, any group who is interested in either from the EDM experimental group, or the muon cooling experimental group, or the μ SR group is welcome to join us with constructing its dedicated secondary muon beam line.