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We report on the progress in flavor identification tools developed for a future e + e − linear collider such as the International Linear Collider (ILC) and Compact Linear Collider (CLIC). Building on the work carried out by the LCFIVertex collaboration, we employ new strategies in vertex finding and jet finding, and introduce new discriminating variables for jet flavor identification. We present the performance of the new algorithms in the conditions simulated using a detector concept designed for the ILC. The algorithms have been successfully used in ILC physics simulation studies, such as those presented in the ILC Technical Design Report.

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We report on a study of top pair production at the International Linear Collider (ILC) around center of mass energy (E CM ) = 350 GeV using an ILD detector simulator based on the Detailed Baseline Design (DBD) configuration. Here we will report on a result of 6-Jet final state, tt → bW bW → bqqbqq. A result for the 4-Jet final state, tt → bW bW → bqqblν, which has almost the same statics as that of the 6-Jet final state will be included in the future. For an energy scan of 11 center of mass energy points (340 -350GeV) and two beam polarization combinations (P(e + , e − ) = (±0.3, ∓0.8)) with 10 fb −1 each, the statistical errors on the top quark Yukawa coupling, its mass and width are estimated. The results are δy t = 4.2%, δm t = 16 MeV in potential subtracted scheme (PS), and δΓ t = 21 MeV.

A novel scheme for the focusing of high-energy leptons in future linear colliders was proposed in 2001 [P. Raimondi and A. Seryi, Phys. Rev. Lett. 86, 3779 (2001)]. This scheme has many advantageous properties over previously studied focusing schemes, including being significantly shorter for a given energy and having a significantly better energy bandwidth. Experimental results from the ATF2 accelerator at KEK are presented that validate the operating principle of such a scheme by demonstrating the demagnification of a 1.3 GeV electron beam down to below 65 nm in height using an energy-scaled version of the compact focusing optics designed for the ILC collider.

This paper introduces a new approach to measure the muon magnetic moment anomaly a µ = (g − 2)/2, and the muon electric dipole moment (EDM) d µ at the J-PARC muon facility. The goal of our experiment is to measure a µ and d µ using an independent method with a factor of 10 lower muon momentum, and a factor of 20 smaller diameter storage-ring solenoid compared with previous and ongoing muon g − 2 experiments with unprecedented quality of the storage magnetic field. Additional significant differences from the present experimental method include a factor of 1,000 smaller transverse emittance of the muon beam (reaccelerated thermal muon beam), its efficient vertical injection into the solenoid, and tracking each decay positron from muon decay to obtain its momentum vector. The precision goal for a µ is statistical uncertainty of 450 part per billion (ppb), similar to the present experimental uncertainty, and a systematic uncertainty less than 70 ppb. The goal for EDM is a sensitivity of 1.5 × 10 −21 e • cm.

We report the first direct measurement of the hyperfine transition of the ground state positronium. The hyperfine structure between ortho-positronium and para-positronium is about 203 GHz. We develop a new optical system to accumulate about 10 kW power using a gyrotron, a mode converter, and a Fabry-Pérot cavity. The hyperfine transition has been observed with a significance of 5.4 standard deviations. The transition probability is measured to be A = 3.1 +1.6 −1.2 × 10 −8 s −1 for the first time, which is in good agreement with the theoretical value of 3.37 × 10 −8 s −1 .Positronium (Ps) [1], a bound state of an electron and a positron, is a purely leptonic system and is a good target to study quantum electrodynamics (QED) in bound state. The triplet (1 3 S 1 ) state of Ps, ortho-positronium (o-Ps), decays into three gamma rays with a lifetime of τ o = 142 ns [2,3]. On the other hand, the singlet (1 1 S 0 ) state of Ps, para-positronium (p-Ps), decays into two gamma rays in τ p = 125 ps [4]. The energy level of the ground state o-Ps is higher than that of the ground state p-Ps due to the spin-spin interaction between the electron and the positron. This difference is called the hyperfine structure of the ground state positronium (Ps-HFS), which is about 203 GHz. Although precise measurements of Ps-HFS have been performed in 1970s and 1980s [5,6], all of them are indirect measurements using Zeeman splitting of about 3 GHz caused by a static magnetic field of about 1 T. There is a discrepancy of 3.9 standard deviations (15 ppm) between the measured and the theoretical value [7]. The largest systematic uncertainty common to all previous measurements is the non-uniformity of the static magnetic field. It is important to directly measure Ps-HFS, in order to avoid the systematic uncertainty of the static magnetic field. Here we present a direct observation of the hyperfine transition between Ps-HFS, which is the first great step toward a direct measurement of Ps-HFS. The hyperfine transition of the ground state Ps, which is M 1 transition, has not yet been observed directly, since the transition probability (Einstein's A coefficient is A = 3.37 × 10 −8 s −1 [8]) is 10 14 times smaller than the decay rate of o-Ps (7.0401(6)×10 6 s −1 [2,3]). In order to cause sufficient amount of stimulated emission from o-Ps to p-Ps, we develop a new optical system which consists of a gyrotron as a sub-THz radiation source, a mode converter to convert the gyrotron output to a Gaussian beam, and a Fabry-Pérot cavity to accumulate high power sub-THz radiation. The gyrotron is a novel FIG. 1: Schematic diagrams of our experimental setup. Top view of the gas chamber is shown in the box. M1 and M2 are parabolic mirrors made of aluminum. We use a gold mesh plane mirror with a transmittance of about 3 % as a beam splitter (BS). Three pyroelectric detectors (PY) are used to monitor the incident, the reflected and the transmitted power.high power radiation source for sub-THz to THz region, which enables us to perform a direct measurement of the...