KM 50

Accomplishments and mysteries in quark flavor physics

~ 50th Anniversary of Kobayashi-Maskawa Theory

The Kobayashi-Maskawa theory, the theory that explains the mechanism of CP violation in the elementary particle physics, was published on February 1st, 1973, and the year 2023 marks its 50th anniversary. On February 11th, 2023, KEK, together with KMI of Nagoya University, organizes a symposium "Accomplishments and mysteries in quark flavor physics ~ 50th Anniversary of Kobayashi-Maskawa Theory (KM 50)" to celebrate the magnificent theoretical idea and experimental discoveries, which verified the theory with ever improving precision in the last 50 years. The symposium consists of scientific talks by theorists and experimentalists to describe the accomplishments in the past years and remaining mysteries to be addressed in the future. We coordially invite colleagues to join us at this memorial moment.

Preceeding the symposium, there is also an associated workshop "KEK Flavor Factories 2023 (KEK-FF 2023)" on February 9th and 10th, 2023, which focuses more on the detailed discussions on the current status of the field. Participants are encouraged to join this event, too.

Date February 9th-10th, 2023 (KEK-FF 2023)
February 11th, 2023 (KM 50)
Venue KEK Tsukuba Campus, Kobayashi Hall
(Tsukuba, Japan)
On-line participation will also be made possible, though not encouraged.

Scientific program

will be posted on the indico page (under construction).

Confirmed speakers

KM 50
  • Adrian Bevan (Queen Mary, London)
  • Andrzej Buras (TUM)
  • Aida El-Khadra (Illinois)
  • Gino Isidori (Zurich)
  • Patrick Koppenburg (Nikhef)
  • Zoltan Ligeti (LBNL)
  • Matthias Neubert (Mainz)
  • Stephen Olsen (Chung Ang)
  • Amarjit Soni (BNL)
  • Nanae Taniguchi (KEK)
  • Taku Yamanaka (Osaka)
KEK-FF 2023
  • Marzia Bordone (CERN)
  • Lu Cao (DESY, Belle)
  • Bernat Capdevila (UAB Barcelona and Cambridge)
  • Claudia Cornella (Mainz)
  • Sasha Glazov (DESY, Belle II)
  • Wolfgang Gradl (Mainz)
  • Gudrun Hiller (TU Dortmund)
  • Martin Hoferichter (Bern)
  • Thibaud Humair (MPP, Belle II)
  • Matthew Kenzie (Warwick)
  • Peter Lewis (Bonn, Belle II)
  • David Marzocca (INFN)
  • Yu Nakazawa (KEK, Belle II)
  • Anton Poluektov (Marseille-CPPM)
  • Chien Yeah Seng (FRIB, U of Washington)
  • Nicola Serra (Zurich)
  • Yuki Sue (Nagoya, Belle II)
  • Vincenzo Vagnoni (INFN, Bologna)
  • GuangJuan Wang (KEK)
  • Oliver Witzel (Siegen)
  • Qidong Zhou (Nagoya, Belle II)
  • Roman Zwicky (Edinburgh)


Registration fee is 3,000 JPY plus 6,000 JPY (for KEK-FF 2023 reception) and 10,000 JPY (for KM 50 banquet). An invoice will be sent to each participant, according to one's attendance of each event. The registration can be made through the indico page. The registration deadline has passed (December 23, 2022).

We plan to broadcast the event through zoom webinar. The link will be announced later. No recording will be made available.


The restriction upon entering Japan due to COVID-19 has been lifted (as of October 11, 2022). The visa exemption policy is the same as before COVID. See the page of the Ministry of Foreign Affairs of Japan for more detailed official information.

Convenient airports are Haneda airport and Narita airport. Both can be accessed by trains and buses to Tsukuba Center. The bus service is currently reduced due to the COVID situation.

From the Narita airport, the easiest way for Tsukuba is to use a highway bus. They leave at 9:30, 10:40, 13:00, 16:20, 17:50, 22:30, or 5-10 min later depending on the airport terminal. It takes about one hour for Tsukuba Center. You should purchase a ticket (2,400 JPY) at the bus ticket counter in the arrival hall. The bus stop will be announced there. If the bus schedule does not fit your arrival time, you can also use trains, though more complicated. (You have to change trains at least twice.) For details, please try Japan Transit Planner.

From the Haneda airport, the bus schedule for Tsukuba is quite limited (leaving at 9:20, 12:15, 17:05, 19:05). Don't forget to purchase a ticket at the counter (1,900 JPY). It takes about two hours for Tsukuba Center. Using trains may be more useful. Typically you use Tokyo Monorail to Hamamatsu-cho, then Yamanote-Line (or KeihinTohoku-Line running in parallel) to Akihabara, and then Tsukuba Express to Tsukuba. You can check with Japan Transit Planner. Trains are sufficiently often that you don't really have to check the time. (But be careful about the last train of the day.)

Participants are asked to book their hotels or the KEK dormitory by themselves. Our suggestions for the hotels are Urban Hotel Tsukuba (closest to KEK, 20-30 min walk), Hotel Nikko Tsukuba (at the Tsukuba Center, use the local bus to KEK) or Daiwa Roynet Hotel Tsukuba (at the Tsukuba Center, use the local bus to KEK). The bus schedule can be downloaded from here. Those who want to stay at the KEK dormitory have to make a user registration to KEK first. In case you need a help, please contact the email address shown below.


KM 50

Naohito Saito (chair, IPNS, KEK), Shoji Hashimoto, Junji Hisano (KMI, Nagoya) Toru Iijima (KMI, Nagoya) Mikihiko Nakao, Mihiko Nojiri, Tadashi Nomura, Shoji Uno
(* IPNS, KEK if not specified)

KEK-FF 2023 Advisory Board

Aida El-Khadra (Illinois), Emi Kou (IJClab), Thomas Mannel (Siegen), Diego Tonelli (Trieste)

KEK-FF 2023 Organizers

Motoi Endo, Shoji Hashimoto (chair), Akimasa Ishikawa, Takashi Kaneko, Teppei Kitahara (KMI, Nagoya) Shohei Nishida
(* IPNS, KEK if not specified)


All inquiries can be directed to