sample work

Shiraishi's Research

About my research

As a physics graduate student at the University of Chicago, I participate in analysis in Accelerator and High Energy Physics as advised by Professor Young-Kee Kim. I worked on top quark decay width analysis as part of CDF and on beam diffusion measurements as part of the Crystal Collimation Experiment in the Tevatron at Fermilab. Currently, I work on laser plasma acceleration in the LOASIS Program at LBNL.

Staging of Laser Wakefield Accelerators at LOASIS

The LOASIS group, Lasers, Optical Accelerator Systems Integrated Studies, researches laser plasma acceleration in the Accelerator & Fusion Research Division at Lawrence Berkeley National Laboratory. As part of this program lead by Dr. Wim Leemans, I participate in an experiment to demonstrate the staging of acceleration units to produce higher energy electrons. Currently, we are developing a new diagnostic to monitor the quality of laser-guiding in a preformed density channel using a wavefront sensor. This technique is crucial for operating the second staging unit efficiently.

Beam Diffusion in Tevatron

Beam losses in high energy colliders can result in serious damage to the accelerator and detector components and create an unacceptable background environment for experiments. One source of beam loss is diffusion caused by effects such as beam scattering with residual gas in vacuum chamber, noise in the radio frequency acceleration system and power supplies, and beam-beam collisions. We measure the diffusion rate in the Fermilab Tevatron using the flying wire beam profile monitor. We have developed a new technique for interpreting the flying wire data, and we measure (8.93+/-0.01)x10-3 mm2/hour and (6.24+/-0.01)x10-3 mm2/hour of horizontal and vertical diffusion rate, respectively.

Crystal Collimation

In order to minimize the effects from beam losses, beam collimation systems are employed to localize beam losses in predetermined locations. The crystal collimation experiment explores the use of bent silicon crystals to improve collimation efficiency. I participated in beam tests at CERN (H8RD22) and experiments in Tevatron (T980) to study how high energy particles pass through bent silicon crystals to develop the collimation system.

Top Quark Decay Width

We present the first direct experimental bound on the total decay width of the top quark using 955pb-1 of the Tevatron's ppbar collisions recorded by the Collider Detector at Fermilab. We identify 253 top-antitop pair candidate events. The distribution of reconstructed top quark mass from these events is fitted to templates representing different values of the top quark width. Using a confidence interval based on likelihood ratio ordering, we extract an upper limit at 95% C.L. of Gammat < 13.1 GeV for an assumed top quark mass of 175 GeV/c2

Laser Plasma Accelerator


A laser pulse traveling through a plasma, indicated by the ellipse at right, accelerates bunches of free electrons (center) in its wake.

Crystal Collimation


Silicon crystals have diamond structure. Atoms create characteristic electric potential wells in the crystal which steers the particles.

Top quark production


One way to produce top and antitop quark pair at Collider Detector at Fermilab.