Belle II Collaboration

24/01/2025

Belle II has now published 45 physics papers, as of the end of last year. We look forward to publishing many more papers in 2025!

https://www.belle2.org/research/physics/publications

17/01/2025

An English version of the article about and operations for 2024 and the new luminosity word record of 5.1 x 10³⁴ cm⁻²s⁻¹ is now available on the 高エネルギー加速器研究機構 素粒子原子核研究所/ website.
Read it here:

KEK素粒子原子核研究所の公式ページ

27/12/2024

Today, on our final day of data taking for this year, the SuperKEKB accelerator broke the luminosity world record, and set a new record luminosity of 5.1 x 10³⁴ cm⁻²s⁻¹! Congratulations and Thank You !

More information here (in Japanese):
https://www2.kek.jp/ipns/ja/news/6972/

【SuperKEKB/Belle II実験は今年の運転を無事終了しました】
https://www2.kek.jp/ipns/ja/news/6972/

加速器、測定器ともに2024年の運転が、本日完了しました。
最終日の本日未明、瞬間ルミノシティ世界最高記録も更新しました👏

Belle II実験グループは加速器グループと連携して、SuperKEKBの性能向上に努めてきました。今期は、以前から問題になっていたSBL(ビームが突然不安定になる現象）の原因究明が進み、安定な運転ができるようになりました。

Belle II実験グループは今期の運転で取得したデータも追加して解析を進め、新物理現象の探索を進めます。

18/11/2024

The Belle II collaboration is proud to support the 2024 International Day of LGBTQIA+ People in Science, Technology, Engineering, and Mathematics. We are committed to fostering an open, diverse, and inclusive working environment that nurtures growth and development of all, and believe that an array of values, interests, experiences, and cultural viewpoints enriches our learning and our workplace. We include these principles in our code of conduct, read more here: https://belle2.jp/diversity/

01/11/2024

KEK IPNS (高エネルギー加速器研究機構 素粒子原子核研究所) has published a new article about the recent Belle II Physics Week, including interviews with physicists.
You can read the article here:

KEK素粒子原子核研究所の公式ページ

31/10/2024

Happy Dark Matter Day!
Belle2 is in searching for "ghostly" invisible particles; their discovery could illuminate one of the most fascinating mysteries of the Universe: Dark Matter.
Dark Matter constitutes about 85% of the matter in our Universe and we do not know its nature.
Belle II has published a number of papers searching for new particles that are part of a hypothesized dark hidden sector. Discovering such particles might solve the enigma of Dark Matter.

Belle II publications include the search for the Z', a new
hypothetical boson introduced in many Beyond Standard Model theories,
https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.130.231801 ,
https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.131.121802 ,
https://journals.aps.org/prd/abstract/10.1103/PhysRevD.109.112015 , and the search for a Long-Lived particle in B meson decays
https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.130.231801 .
Other analyses performed at Belle II are the search for a dark Higgs
boson in association with a dark photon
https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.130.071804 ,
and the search for an alpha boson in tau decays
https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.130.181803 .

31/10/2024

Happy Halloween from Belle II!
The group at Uppsala University have been celebrating by demonstrating their fantastic pumpkin carving skills!

21/10/2024

Over 150 physicists gathered at KEK for this year's Belle II Physics Week, including a number of particle physics theorists, and members of other experiments including the ATLAS Experiment at CERN and LHCb Experiment at CERN. The theme of the week was studying the tau and dark sector at Belle II. In the mornings we held a school with lectures on recent experimental and theoretical aspects of tau and dark sector physics. In the afternoons there were workshops focusing on special topics at the interface of theory and experiment.

Many students and postdocs attended, participating in lively interactions during the coffee breaks and workshop sessions. Many also took the opportunity to present their work during our poster session. The award for best poster was won by Han Eol Cho of Hanyang University for the poster "Search for lepton-flavor-violating tau -> l pi0 decays at Belle II".

We thank the KEK Theory Center for organising the event, and Toshiko Yuasa Lab (TYL), Kobayashi-Maskawa Institute, and KEK/LBNL for their support of Physics Week.

08/10/2024

Over 250 Belle II researchers gathered at .JP this week for the 49th Belle II General Meeting. At this we are on the threshold of the resumption of Run 2 after the 2024 summer shutdown. This gathering gives us the chance to review the results of our spring 2024 running period, which began in February after our 18 month Long Shutdown. With our partners who operate the accelerator, we are planning the future of Run 2.

29/09/2024

Happy Birthday CERN!
お誕生日おめでとうございます (Otanjōbi omedetō gozaimasu)!
Congratulations on 70 years of exploring the frontiers of physics, and best wishes for the celebrations!

25/07/2024

The 42nd International Conference on High Energy Physics recently finished in Prague, Czechia. Fourteen-hundred participants gathered to present and discuss the latest results across the whole of particle physics.

The excellent organization of the meeting led to a convivial environment for discussions and catching up with old friends; Belle II member Zdeněk Doležal chaired the local organizing committee.

Members of the Belle II collaboration presented 17 talks, 15 parallel and two plenary, at the conference, spanning a wide range of topics including CKM physics, τ physics, CP violation, Dark Sector, lepton flavour violation, hadron spectroscopy, the Belle II upgrade programme and more. results on gamma, R(D*) and B→K*ττ were highlighted in the closing summary talk by Prof. Marumi Kado.

03/07/2024

Raynette van Tonder (McGill) has received a DFG (Deutsche Forschungsgemeinschaft) Walter-Benjamin Fellowship for 221430€ to perform the first study of the charged lepton forward-backward asymmetry of inclusive semileptonic B decays using Belle II data. This measurement of the asymmetry in the distribution of the angle between the B meson and the lepton in the lepton-neutrino rest frame (see attached figure) will lead to more precise determinations of the CKM matrix element |V_cb|, shedding new light on the longstanding puzzle between inclusive and exclusive measurements. The research project will be hosted by the Karlsruhe Institute of Technology (KIT).

26/06/2024

The 10th annual Belle II Summer Workshop was held from 16-21 June 2024 at the scenic and historic University of Mississippi campus in Oxford, MS, USA. Our summer workshops aim to educate Belle II early career researchers (undergraduates, graduate students and postdocs) in data analysis, AI/ML and GRID computing techniques.

There were pedagogical presentations on the Belle II physics program, recent results and upgrades. Topics included B physics, charm physics, tau physics, dark sector searches and the Chiral Belle polarization upgrade. The first day featured the Belle II Explorer workshop intended to introduce students and faculty at minority serving institutions (MSI) to particle physics and the Belle II experiment. In addition, there were interactive professional development and DEI workshops.

There were several workshop excursions including a hike and visit to Rowan Oak, the house of Nobel Literature laureate and renowned American author, William Faulkner (1897-1962). https://en.wikipedia.org/wiki/William_Faulkner
Many Belle II collaborators recognised Faulkner as the man pictured on the side of a can of Boss Coffee, one of the major canned coffee brands in Japan.

05/06/2024

Over 230 Belle II researchers have gathered at KEK 高エネルギー加速器研究機構 this week for the 48th Belle II General Meeting. This gives us the opportunity to review our progress since resuming data taking operations in February after our 18 month Long Shutdown. Together with experts from the accelerator, we are meeting face to face, brainstorming, and planning for the future of Run 2.

We are also preparing results for the conference in Prague, Czechia (https://ichep2024.org/), and we have just submitted our 45th Journal publication: https://www.belle2.org/research/physics/publications