S. Kawada

S. Kawada
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High Energy Physics - Experiment (9)
 
High Energy Physics - Phenomenology (5)
 
Physics - Instrumentation and Detectors (3)
 
Physics - Accelerator Physics (2)

Publications Authored By S. Kawada

We have developed a novel technique for the measurement of the avalanche fluctuation of gaseous detectors using a UV laser. The technique is simple and requires a short data-taking time of about ten minutes. Furthermore, it is applicable for relatively low gas gains. Read More

For the International Large Detector concept at the planned International Linear Collider, the use of time projection chambers (TPC) with micro-pattern gas detector readout as the main tracking detector is investigated. In this paper, results from a prototype TPC, placed in a 1 T solenoidal field and read out with three independent GEM-based readout modules, are reported. The TPC was exposed to a 6 GeV electron beam at the DESY II synchrotron. Read More

We evaluate the measurement precision of the production cross section times the branching ratio of the Higgs boson decaying into tau lepton pairs at the International Linear Collider (ILC). We analyze various final states associated with the main production mechanisms of the Higgs boson, the Higgs-strahlung and WW-fusion processes. The statistical precision of the production cross section times the branching ratio is estimated to be 2. Read More

We evaluate the expected measurement accuracy of the branching ratio of the Standard Model Higgs boson decaying into tau pairs at the ILC with a full simulation of the ILD detector concept. We assume a Higgs mass of 125 GeV, a branching ratio of BR($h \to \tau ^+ \tau ^-$) = 6.32%, a beam polarization of electron (positron) of -0. Read More

The purpose of ILD-TPC Asia group is realization of high precision Time Projection Chamber (TPC) with Gas Electron Multiplier (GEM) as a central tracker in International Linear Collider (ILC). We have been studying the many R&D items to build the real detector as a member of LCTPC collaboration. This paper describes the our efforts for realization of the ILD-TPC, the result of test beam using large prototype TPC, local field distortion, positive ion effects and gate devices, and cooling electronics which are key items to build ILD-TPC. Read More

We evaluate the expected measurement accuracy of the branching ratio of the Standard Model Higgs boson decaying into tau lepton pairs $h \to \tau ^+ \tau ^-$ at the ILC with a center-of-mass energy of $\sqrt{s} = 500$ GeV with a full simulation of the ILD detector. We assume a Higgs mass of $M_h = 125$ GeV, a branching ratio of $\mathrm{BR}(h \to \tau ^+ \tau ^-) = 6.32 \%$, beam polarizations of $P(e^+, e^-) = (-0. Read More

2013Oct

This report summarizes the work of the Energy Frontier Higgs Boson working group of the 2013 Community Summer Study (Snowmass). We identify the key elements of a precision Higgs physics program and document the physics potential of future experimental facilities as elucidated during the Snowmass study. We study Higgs couplings to gauge boson and fermion pairs, double Higgs production for the Higgs self-coupling, its quantum numbers and $CP$-mixing in Higgs couplings, the Higgs mass and total width, and prospects for direct searches for additional Higgs bosons in extensions of the Standard Model. Read More

In a conventional positron source driven by a few GeV electron beam, a high amount of heat is loaded into a positron converter target to generate intense positrons required by linear colliders, and which would eventually damage the converter target. A hybrid target, composed of a single crystal target as a radiator of intense gamma--rays, and an amorphous converter target placed downstream of the crystal, was proposed as a scheme which could overcome the problem.This paper describes the development of an intense positron source with the hybrid target. Read More

The ILC Higgs White Paper is a review of Higgs Boson theory and experiment at the International Linear Collider (ILC). Theory topics include the Standard Model Higgs, the two-Higgs doublet model, alternative approaches to electroweak symmetry breaking, and precision goals for Higgs boson experiments. Experimental topics include the measurement of the Higgs cross section times branching ratio for various Higgs decay modes at ILC center of mass energies of 250, 500, and 1000 GeV, and the extraction of Higgs couplings and the total Higgs width from these measurements. Read More

We evaluate the measurement accuracy of the branching ratio of $h \to \tau ^+ \tau ^-$ at $\sqrt{s} = 250$ GeV and 500 GeV at the ILC with the ILD detector simulation. For the $\sqrt{s} = 250$ GeV, we assume the Higgs mass of $M_h = 120$ GeV, branching ratio of $\mathrm{Br}(h \to \tau ^+ \tau ^-) = 8.0 \ %$, beam polarization of $P(e^-, e^+) = (-0. Read More

We studied the feasibility of the measurement of Higgs pair creation at a Photon Linear Collider (PLC). From the sensitivity to the anomalous self-coupling of the Higgs boson, the optimum $\gamma \gamma$ collision energy was found to be around 270 GeV for a Higgs mass of 120 GeV/$c^2$. We found that large backgrounds such as $\gamma \gamma \rightarrow W^+W^-, ZZ,$ and $b\bar{b}b\bar{b}$, can be suppressed if correct assignment of tracks to parent partons is achieved and Higgs pair events can be observed with a statistical significance of $\sim 5 \sigma$ by operating the PLC for 5 years. Read More

We studied the feasibility of measurement of Higgs pair creation in a gamma gamma collider. We found the optimum collision energy is around 270 GeV from the sensitivity study with Higgs boson mass of 120 GeV/c^2. Main backgrounds are gamma gamma to WW, gamma gamma to ZZ, and gamma gamma to bbbb at the optimum collision energy. Read More

A possible solution to realize a conventional positron source driven by a several-GeV electron beam for the International Linear Collider is proposed. A 300 Hz electron linac is employed to create positrons with stretching pulse length in order to cure target thermal load. ILC requires about 2600 bunches in a train which pulse length is 1 ms. Read More