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Radiation Laboratory
last update, 16-April-2009

Location  Room 254/256, in the Main Research Building at RIKEN, Wako
Address  Radiation Lab, RIKEN, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan
Telephone  +81-48-467-9347
Fax +81-48-462-4641
Novel StriPixel Detector, the mass-production prototype, for PHENIX Silicon Vertexl Detector

Welcome to our home page.  The Radiation Laboratory is one of the eldest research groups in RIKEN, now belonging to Nishina Center for Accelerator-Based Science. The major activity of Radiation Laboratory is to perform an experiment using high-energy polarized-proton collisions and heavy-ion collisions at BNL-RHIC in USA, through cooperations with RIKEN-BNL Research Center. We are also performing ion source developments and novel detector developments. In January-April 2009, collisions of polarized polarized proton at the center of mass energy of  500 GeV have been succesfully performed, toward the determineation of anti-quark polarization in the proton using W boson production.

Our Activities
Spin Physics at RHIC
Heavy Ion Physics at BNL
Meson in Nuclear Matter
  How the spin of proton is formed with 3 quarks and gluons? This is a very fundament question in QCD, Quantum Chromodynamic. The RHIC Spin Project has been established to solve this problem by colliding two polarized protons for the first time in history.
  Collisions of polarized protons are measured with the PHENIX detector at RHIC
PHENIX collaboration

 Collaboration with accelerator group, theorists,  and other RHIC experiments is the key for the success of the program. The RBRC experimental group is conducting RSC, Rhic Spin Collaboration.


  Research program is organized in PHENIX Spin Physics Working Group, and  analysis of the PHENIX data is performed at CCJ combined with RIKEN super computer cluster.
  Recent analysis on the asymmetry of  the neutral pion production has shown that the gluon polarization in proton is surprisingly small, i.e. gluon is less likely  the career of proton spin.   Natural ansatz from this discovery is existence of significant orbital motion in the proton.

Gluon Polarization in Proton
Click above to enlarge

 At RHIC QGP, Quark Gluon Plasma, should be created by colliding two gold nuclei, through which we can study the state of early Universe just after the Big Bang. 
  Very recently, enhanced e+e- pair yield above hadronic sources is observed in Au+Au collisions at RHIC. The characteristic temperature is determined to be 221 MeV. This will be the key measurement to determine the nature of the hot and dens matter RHIC created.
Direct photon in AA
Click above to get a preprint
  While RHIC creates nuclear matter with high temperature, study of dense nuclear matter was being performed at KEK, and phi meson modification at normal nuclear density was discovered as shown  below.

Click above to get a preprint

 To extend our research further we proposed a new experiment to be done at J-PARC.

Click above to get the proposal
QCD Theory
PHENIX Detector Upgrade 
Laser Ion Source
Neutrons, optics and detection
  Theory group in Radiation Laboratory is studying theoretical aspects of physics at RHIC. Our global analysis for world-wide asymmetry  data showed the  gluon polarization in proton is strongly constraneted with recent data from RHIC.
.marco's figure
Click above to get a preprint
To enhance physics capability of PHENIX even further, PHENIX Detector Upgrade R&D is on going through the collaboration with BNL instrumentation division, CERN-ALICE and CERN-NA60. 

Wire bonding
120 micron pitch wire bonding for Pixel Detector. Click Above to see the Ladder.

  Developments of laser-induced plasma ion source is going as a collaboration with BNL Accelerator Division. This source ejects the world highest intensity of carbon and aluminum beam so far, and will be used for an ion injector for RHIC.  This method is so compact and can be useful for cancer therapy as well. 

RFQ used for the ion source

  By combining novel methods for neutron optics with super conducting tunnel-junction detector, we aim to perform precise measurements for neutron decays. Applications go also to neutron interference and neutron scattering. 

Sextupole magnet to focus cold  neutron

Recent Memorial Events
 Hiromi Okada, former Junior Research Associate of Radiation Lab., received RHIC & AGS thesis award 2007. R. Muto, former Special Doctral Fellow of Radiation Lab., received 2007 Young Scientist Award of the Physical Society of Japan. H En'yo and S. Yokkaichi received Significant Achievement Award in RIKEN, March 2008.
phi in Riken Research
Click above to go to  RIKEN Research Article

  Five-year MoU between RIKEN and BNL was signed  by BNL Director S, Aronson and RIKEN President R. Noyori, Jan. 2007.

  T. D. Lee, Director emeritus of RIKEN BNL Research Center  has awarded for The Order of the Rising Sun, Gold and Silver Star (旭日重光章), Jan. 2007.
Another art

  Phenix  event display was chosen for  RIKEN Art & Science Exhibition.

Members (April 2009)
bold names are recent additions

Old member list(2008)
Old member list(2007)
Old member list(2006)
Old member list(2005)
Old member list(2004)
Old member list(2003)

People Left from Radiation Lab.

Radiation Laboratory


Name Other 
Activity @
Chief Scientist Hideto Enyo RBRC PHENIX,JPARC W
Vice Chief Scientist Takashi Ichihara RBRC, RIBF PHENIX,RIB W

Yasuyuki Akiba RBRC (Exp. G.L.)
Scientist Yasushi Watanabe RBRC PHENIX,RIB W

Atsushi Taketani RBRC PHENIX W

Yoshie Ohtake
Neutron Optics W


Itaru Nakagawa RBRC PHENIX B

Satoshi Yokkaichi RBRC PHENIX,JPARC W
Collaborating Scientist Naohito Saito KEK PHENIX

Kazuyoshi Kurita Rikkyo-U PHENIX

Kiyoshi Tanida Korea-U PHENIX

Tsutomu Mibe KEK PHENIX
Foregin Postdoctoral Researcher
Stephen Baumgart
From Yale U. Starting in Oct. '09. 
Special Postdoctoral Researcher Kazuya Aoki

Masayuki Niiyama
Contract Researcher Maki Kurosawa

Tomoaki Nakamura

Ken'ichi Nakano

Yoshinori Fukao

Yohei Nakatsugawa

Entrustee Katsuya Hirota JNOP  Neutron/STJ W
Technical Staff Junpei Kanaya
Senior Visiting Scientist Ken Imai Kyoto-U PHENIX K

ToshiAki Shibata TITech PHENIX T

Hirohiko Shimizu KEK Netron/STJ K

Takashi Nakano
Osaka-U, RCNP
Students  Kohei Syoji Kyoto-U, Intern

Takashi Kanesue Kyusyu-U,JSPS BNL-CAD B

Jun Tamura T.I.Tech,JRA BNL-CAD B

Yoshichika Seki Kyoto-U, JSPS Neutron W

Yorito Yamaguchi CNS-U-Tokyo, JRA PHENIX B

Misaki Oouchida  Hiroshima-U,JRA PHENIX B

Kenichi Karatsu Kyoto-U,JRA PHENIX B

Seiji Dairaku Kyoto-U, Intern

Yoki Aramaki CNS,U-Tokyo, JRA PHENIX B

Satoshi Sano CNS,U-Tokyo, JRA PHENIX,ALICE B

Kimiaki Hashimoto Rikkyo-U, JRA PHENIX W

Miki Kasai Rikkyo-U, JRA

Yosuke Haki Rikkyo-U, SPT PHENIX W

Katsuro Nakamura Kyoto-U, JSPS PHENIX W

Dosatsu Sakata
Tsukuba-U, JRA

Ryu Sun Yong
Osaka-U, IPA


Name Other Affiliation @
Senior Visiting Researcher Koichi Yazaki T.W.U W
Contract Researcher Yu Maezawa

Hideaki Iida

Students Satoru Ueda Tsukuba-U, RBRC-theory B

Noriko Kiyama

Karen Sakuma
RIKEN-BNL Research Center


Name Other 
Center Director Nick Samios BNL B
Director Emeritus T.D. Lee Columbia U. B
Associate Director Hideto En'yo Radiation Lab W


Name Other 
Group Leader Yasuyuki Akiba RIKEN
Deputy Group Leader Abhay L. Deshpande SUNY
RHIC Fellow  David Kawall Yale
Fellow Kensuke Okada

Ralf Seidl

Stefan Bathe
Research Associate Kieran Boyle
RIKEN Special Postdoctoral Researcher  Manabu Togawa
Akihisa Takahara
CNS, U-tokyo
Collaborating Scientist Akio Ogawa BNL

Zheng Li BNL

Alexander Bazilevsky BNL

Masahiro Okamura BNL-CAD

Theory ( Japanese member)

Other Non-Japanese members can be found here

Name Other 
Group Leader L. Mclerran BNL
Deputy Group Leader Anthony Baltz BNL
RHIC Physics Fellow Taku Izubuchi BNL
Fellow Yasumichi Aoki
Research Associate Tomomi Ishikawa
RIKEN Special Postdoctoral Researcher Toru Kojo
Visiting Scientist Shigemi Ohta KEK

Administration, Secretary

Office at RBRC Ryosuke Maruyama

Emiko Adachi
Secretary Doris Rueger

Pam Esposito

Taeko Itoh

Susan Foster
Office at Wako Hiroshi Miyamoto

Keiko Suzuki


OUT REACHES ( in Japanese)

★ 素粒子クォークの仕組みを解明する
@mic go! go! 〜原子と原子核 基礎講座〜
(Jippiコンパク ト)
phi decay
@mic gogo

book by Enyo