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Belle II experiment

April 09, 2023

Coordinates: 36°9′28″N 140°4′30″E / 36.15778°N 140.07500°E / 36.15778; 140.07500

The Belle II experiment is a particle physics experiment designed to study the properties of B mesons (heavy particles containing a beauty quark) and other particles. Belle II is the successor to the Belle experiment, and commissioned at the SuperKEKB[1] accelerator complex at KEK in Tsukuba, Ibaraki prefecture, Japan. The Belle II detector was "rolled in" (moved into the collision point of SuperKEKB) in April 2017.[2][3] Belle II started taking data in early 2018.[1] Over its running period, Belle II is expected to collect around 50 times more data than its predecessor mostly due to a 40-fold increase in an instantaneous luminosity provided by SuperKEKB as compared to the previous KEKB accelerator.[1]

The opened Belle II detector before installation of the inner tracking detectors.

Physics program

Many interesting analyses of the Belle and BaBar experiments were limited by statistical uncertainties, which was the main motivation to build a new generation of B-factory - Belle II.

The target dataset is 50 ab−1 at Belle II[4] compared to 988 fb−1 (with 711 fb−1 at the Υ(4S) energy) at Belle.[5] The dataset of good runs from Belle II before Long shutdown 1 was 424 fb−1 (with 363 fb−1 at the Υ(4S) energy.)[6]

This immense dataset would allow studies of rare physics processes, which were out of reach for the previous e+ e− experiments and improve precision on the already measured physics observables.

The physics program of Belle II includes the studies of the following particles or processes:[7]

The majority of the Belle II dataset will be recorded at Upsilon(4S) center-of-mass energy, while a small portion of it will be taken at Upsilon(5S) and as energy scans.

Detector composition

Belle II is a general purpose high-energy particle physics detector with almost full solid angle coverage. It has a cylindrical shape to cover the e+ e− collisions happening on the central axis of the detector. The detector is asymmetric in beam direction, because the initial energy of the electron beam is larger than the positron beam. Much of the original Belle detector has been upgraded[4] to cope with the higher instantaneous luminosity provided by the SuperKEKB accelerator.[1]

The main components are the following, from the innermost to the outermost systems.:[4]

  • Beryllium beam pipe at a minimum radius of 10 mm from the beam
  • PiXel Detector (PXD) is composed from two cylindrical layers of depleted field effect transistor (DEPFET) pixels,[8] provide as precise position measurement of the charged particle trajectories. First layer is only 14 mm away from the beam. So far, only two ladders of the second PXD layer have been installed.[9]
  • Silicon Vertex Detector (SVD) - 8 layers of silicon strip sensors arranged in cylindrical barrel and an inclined endcap towards electron direction for better coverage. The SVD and PXD detectors sometimes are referred as VerteX Detector (VXD). The total VXD size has been tuned to cover most of the typical   travel distance.
  • Central Drift Chamber (CDC) is a wire chamber central tracking system, which provides the measurement of momentum and charge of the charged particles produced by the collisions as well as particle type identification (PID) via their energy depositions.
  • Aerogel ring-imaging Cherenkov detector[10] (aRICH) provides PID information about the charged particle going into the forward direction.
  • Time Of Propagation (TOP)[11] counter consisting of quartz bars utilising totally internally reflected Cherenkov photons and measuring the time of propagation, which is used for PID.
  • Electromagnetic calorimeter (ECL)[12] a highly segmented array of thallium-doped caesium iodide CsI(Tl) crystals assembled in a projective geometry to measure energies of the neutral final state particles such as photons,   and neutrons, as well as PID.
  • Superconducting solenoid, which provides a 1.5 tesla magnetic field, which bends the trajectories of the final state charged particles to measure their charge and momentum.
  •   and Muon detector (KLM)[13] used to identify   energy depositions as well as for muon PID.
 
Construction work on the Central Drift Chamber (CDC) of the Belle II experiment

Timeline

The Belle II experiment data taking is separated into three phases:[14]

  • Phase I — completed Feb–June 2016: SuperKEKB commissioning to characterize the beam environment;
  • Phase II — started early 2018, running without the nominal inner silicon-based VXD tracking system to measure the beam-induced background radiation in the innermost tracking system. During this phase the VXD subdetector has been replaced by Beam Exorcism for a Stable ExperimenT II or BEAST II system which was used to test various tracking technologies and a total integrated luminosity of 500 pb  has been collected;[15]
  • Phase III — started 2019: data taking with the complete Belle II detector;

On November 22, 2018, the Belle II detector was completed with the installation of the VerteX Detector (VXD).[16] On March 25, 2019, the first collisions of the actual physics program were detected.[17]

On 15 June 2020, the SuperKEKB reached an instantaneous luminosity of 2.22×1034 cm−2s−1 — surpassing the LHC's record of 2.14×1034 cm−2s−1 set with proton–proton collisions in 2018. A few days later, SuperKEKB pushed the luminosity record to 2.4×1034 cm−2s−1.[18] In June 2022 the luminosity record was nearly doubled to 4.7×1034 cm−2s−1.[19]

Scientific personnel

The Belle II experiment is being governed by Belle II Collaboration,[20] which is an international worldwide scientific community.

The Belle II Collaboration has designed, produced, assembled and is currently operating the Belle II experiment. The collaboration handles the collision data recorded at the experiment, performs the data analysis and delivers the results in form of scientific journal articles, conference talks, etc.

As on May 30, 2019, it included 970 members from 112 institutes and 26 countries around the globe.[21]

Experiment software

In October 2021 the Software development team within the Belle II Collaboration has published Belle II Analysis Software Framework or basf2[22] as open-source software on GitHub.[23]

This is the main package used to simulate, reconstruct and analyse the recorded collision events at the Belle II experiment and there are several other separate satellite packages, used for DAQ, computation of the systematic uncertainties, etc.

The backend of the reconstruction and analysis libraries are written in C++,[24] while the analysis steering and facade are implemented in Python[24] language.

To coordinate the software development, the Belle II Collaboration uses industrial collaboration tools such as Atlassian Jira, Confluence and git-based BitBucket service.

See also

Image gallery

References

  1. ^ a b c d "SuperKEKB". www-superkekb.kek.jp. Retrieved 2017-04-28.
  2. ^ "Belle II Experiment on Twitter". Twitter. Retrieved 2017-05-07.
  3. ^ "Belle II rolls in - CERN Courier". cerncourier.com. 19 May 2017. Retrieved 2017-05-22.
  4. ^ a b c Abe, T.; et al. (October 2010). "Belle II Technical Design Report". arXiv:1011.0352 [physics.ins-det].
  5. ^ Bevan, A. J.; Golob, B.; Mannel, Th; Prell, S.; Yabsley, B. D.; Aihara, H.; Anulli, F.; Arnaud, N.; Aushev, T. (2014-11-01). "The Physics of the B Factories". The European Physical Journal C. 74 (11): 3026. arXiv:1406.6311. Bibcode:2014EPJC...74.3026B. doi:10.1140/epjc/s10052-014-3026-9. ISSN 1434-6044. S2CID 9063079.
  6. ^ "Belle II Luminosity - Belle II - DESY Confluence". confluence.desy.de. Retrieved 2022-08-03.
  7. ^ Abe, T.; Adachi, I.; Adamczyk, K.; Ahn, S.; Aihara, H.; Akai, K.; Aloi, M.; Andricek, L.; Aoki, K.; Arai, Y.; Arefiev, A. (2010-11-01). "Belle II Technical Design Report". arXiv:1011.0352 [physics.ins-det].
  8. ^ Casarosa, Giulia (2015). "Inner tracking devices at the Belle II experiment". Proceedings, 2015 European Physical Society Conference on High Energy Physics (EPS-HEP 2015) : Vienna, Austria, July 22-29, 2015. p. 255.
  9. ^ "Belle II Germany Meeting". indico.belle2.org (Indico). Retrieved 2022-01-11.
  10. ^ Nishida, S.; et al. (2014). "Aerogel RICH for the Belle II forward PID". Nuclear Instruments and Methods in Physics Research Section A. 766: 28–31. Bibcode:2014NIMPA.766...28N. doi:10.1016/j.nima.2014.06.061.
  11. ^ Inami, Kenji (2014). "TOP counter for particle identification at the Belle II experiment". Nuclear Instruments and Methods in Physics Research Section A. 766: 5–8. Bibcode:2014NIMPA.766....5I. doi:10.1016/j.nima.2014.07.006.
  12. ^ "Electromagnetic Calorimeter | Belle II Experiment". belle2.jp. Retrieved 2017-05-07.
  13. ^ Aushev, T.; et al. (2015). "A scintillator based endcap KL and muon detector for the Belle II experiment". Nuclear Instruments and Methods in Physics Research Section A. 789: 134–142. arXiv:1406.3267. Bibcode:2015NIMPA.789..134A. doi:10.1016/j.nima.2015.03.060. S2CID 118613296.
  14. ^ N.Braun - Hadron Spectroscopy Studies at Belle II
  15. ^ "Belle II: Erfolgreicher Einbau des BEAST-Detektors". www.mpp.mpg.de (in German). Retrieved 2022-01-11.
  16. ^ @belle2collab (22 November 2018). "VerteX Detector (VXD) successfully installed in #Belle2. The Belle II detector is now complete!" (Tweet) – via Twitter.
  17. ^ Kick-off of the Belle II Phase 3 Physics Run
  18. ^ "KEK reclaims luminosity record". CERN Courier. 2020-06-30. Retrieved 2022-01-11.
  19. ^ "Belle II". www.belle2.org. Retrieved 2022-08-03.
  20. ^ "Contact". www.belle2.org. Retrieved 2022-01-03.
  21. ^ "Public GeneralSlides - Belle II - DESY Confluence". confluence.desy.de. Retrieved 2022-01-03.
  22. ^ Kuhr, T.; Pulvermacher, C.; Ritter, M.; Hauth, T.; Braun, N. (December 2019). "The Belle II Core Software". Computing and Software for Big Science. 3 (1): 1. arXiv:1809.04299. doi:10.1007/s41781-018-0017-9. ISSN 2510-2036. S2CID 119342160.
  23. ^ The Belle II Collaboration (2021-10-19), Belle II Analysis Software Framework (basf2), doi:10.5281/zenodo.5574115, retrieved 2022-01-07
  24. ^ a b The Belle II Collaboration (2021). "Search · · belle2/basf2". GitHub. doi:10.5281/zenodo.5574115. Retrieved 2022-01-07.

External links

 
Wikimedia Commons has media related to Belle II experiment.
  • Belle II public webpage
  • Belle II collaboration webpage
  • German Belle II webpage
  • A Search for New Physics - The Belle II Experiment
  • Inside Japan's big physics - Belle II
  • Record for SuperKEKB-Belle II experiment on INSPIRE-HEP
  • Record for SuperKEKB project on INSPIRE-HEP

April 09, 2023
belle, experiment, coordinates, 15778, 07500, 15778, 07500, particle, physics, experiment, designed, study, properties, mesons, heavy, particles, containing, beauty, quark, other, particles, belle, successor, belle, experiment, commissioned, superkekb, acceler. Coordinates 36 9 28 N 140 4 30 E 36 15778 N 140 07500 E 36 15778 140 07500 The Belle II experiment is a particle physics experiment designed to study the properties of B mesons heavy particles containing a beauty quark and other particles Belle II is the successor to the Belle experiment and commissioned at the SuperKEKB 1 accelerator complex at KEK in Tsukuba Ibaraki prefecture Japan The Belle II detector was rolled in moved into the collision point of SuperKEKB in April 2017 2 3 Belle II started taking data in early 2018 1 Over its running period Belle II is expected to collect around 50 times more data than its predecessor mostly due to a 40 fold increase in an instantaneous luminosity provided by SuperKEKB as compared to the previous KEKB accelerator 1 The opened Belle II detector before installation of the inner tracking detectors Contents 1 Physics program 2 Detector composition 3 Timeline 4 Scientific personnel 5 Experiment software 6 See also 7 Image gallery 8 References 9 External linksPhysics program EditMany interesting analyses of the Belle and BaBar experiments were limited by statistical uncertainties which was the main motivation to build a new generation of B factory Belle II The target dataset is 50 ab 1 at Belle II 4 compared to 988 fb 1 with 711 fb 1 at the Y 4S energy at Belle 5 The dataset of good runs from Belle II before Long shutdown 1 was 424 fb 1 with 363 fb 1 at the Y 4S energy 6 This immense dataset would allow studies of rare physics processes which were out of reach for the previous e e experiments and improve precision on the already measured physics observables The physics program of Belle II includes the studies of the following particles or processes 7 B meson Charm meson Bottomonium Charmonium Tau lepton Dark sector Low multiplicity processesThe majority of the Belle II dataset will be recorded at Upsilon 4S center of mass energy while a small portion of it will be taken at Upsilon 5S and as energy scans Detector composition EditBelle II is a general purpose high energy particle physics detector with almost full solid angle coverage It has a cylindrical shape to cover the e e collisions happening on the central axis of the detector The detector is asymmetric in beam direction because the initial energy of the electron beam is larger than the positron beam Much of the original Belle detector has been upgraded 4 to cope with the higher instantaneous luminosity provided by the SuperKEKB accelerator 1 The main components are the following from the innermost to the outermost systems 4 Beryllium beam pipe at a minimum radius of 10 mm from the beam PiXel Detector PXD is composed from two cylindrical layers of depleted field effect transistor DEPFET pixels 8 provide as precise position measurement of the charged particle trajectories First layer is only 14 mm away from the beam So far only two ladders of the second PXD layer have been installed 9 Silicon Vertex Detector SVD 8 layers of silicon strip sensors arranged in cylindrical barrel and an inclined endcap towards electron direction for better coverage The SVD and PXD detectors sometimes are referred as VerteX Detector VXD The total VXD size has been tuned to cover most of the typical K S 0 displaystyle K S 0 travel distance Central Drift Chamber CDC is a wire chamber central tracking system which provides the measurement of momentum and charge of the charged particles produced by the collisions as well as particle type identification PID via their energy depositions Aerogel ring imaging Cherenkov detector 10 aRICH provides PID information about the charged particle going into the forward direction Time Of Propagation TOP 11 counter consisting of quartz bars utilising totally internally reflected Cherenkov photons and measuring the time of propagation which is used for PID Electromagnetic calorimeter ECL 12 a highly segmented array of thallium doped caesium iodide CsI Tl crystals assembled in a projective geometry to measure energies of the neutral final state particles such as photons K L 0 displaystyle K L 0 and neutrons as well as PID Superconducting solenoid which provides a 1 5 tesla magnetic field which bends the trajectories of the final state charged particles to measure their charge and momentum K L 0 displaystyle K L 0 and Muon detector KLM 13 used to identify K L 0 displaystyle K L 0 energy depositions as well as for muon PID Construction work on the Central Drift Chamber CDC of the Belle II experimentTimeline EditThe Belle II experiment data taking is separated into three phases 14 Phase I completed Feb June 2016 SuperKEKB commissioning to characterize the beam environment Phase II started early 2018 running without the nominal inner silicon based VXD tracking system to measure the beam induced background radiation in the innermost tracking system During this phase the VXD subdetector has been replaced by Beam Exorcism for a Stable ExperimenT II or BEAST II system which was used to test various tracking technologies and a total integrated luminosity of 500 pb 1 displaystyle 1 has been collected 15 Phase III started 2019 data taking with the complete Belle II detector On November 22 2018 the Belle II detector was completed with the installation of the VerteX Detector VXD 16 On March 25 2019 the first collisions of the actual physics program were detected 17 On 15 June 2020 the SuperKEKB reached an instantaneous luminosity of 2 22 1034 cm 2s 1 surpassing the LHC s record of 2 14 1034 cm 2s 1 set with proton proton collisions in 2018 A few days later SuperKEKB pushed the luminosity record to 2 4 1034 cm 2s 1 18 In June 2022 the luminosity record was nearly doubled to 4 7 1034 cm 2s 1 19 Scientific personnel EditThe Belle II experiment is being governed by Belle II Collaboration 20 which is an international worldwide scientific community The Belle II Collaboration has designed produced assembled and is currently operating the Belle II experiment The collaboration handles the collision data recorded at the experiment performs the data analysis and delivers the results in form of scientific journal articles conference talks etc As on May 30 2019 it included 970 members from 112 institutes and 26 countries around the globe 21 Experiment software EditIn October 2021 the Software development team within the Belle II Collaboration has published Belle II Analysis Software Framework or basf2 22 as open source software on GitHub 23 This is the main package used to simulate reconstruct and analyse the recorded collision events at the Belle II experiment and there are several other separate satellite packages used for DAQ computation of the systematic uncertainties etc The backend of the reconstruction and analysis libraries are written in C 24 while the analysis steering and facade are implemented in Python 24 language To coordinate the software development the Belle II Collaboration uses industrial collaboration tools such as Atlassian Jira Confluence and git based BitBucket service See also EditB factory B B oscillation LHCb experimentImage gallery EditThis section is empty You can help by adding to it January 2022 References Edit a b c d SuperKEKB www superkekb kek jp Retrieved 2017 04 28 Belle II Experiment on Twitter Twitter Retrieved 2017 05 07 Belle II rolls in CERN Courier cerncourier com 19 May 2017 Retrieved 2017 05 22 a b c Abe T et al October 2010 Belle II Technical Design Report arXiv 1011 0352 physics ins det Bevan A J Golob B Mannel Th Prell S Yabsley B D Aihara H Anulli F Arnaud N Aushev T 2014 11 01 The Physics of the B Factories The European Physical Journal C 74 11 3026 arXiv 1406 6311 Bibcode 2014EPJC 74 3026B doi 10 1140 epjc s10052 014 3026 9 ISSN 1434 6044 S2CID 9063079 Belle II Luminosity Belle II DESY Confluence confluence desy de Retrieved 2022 08 03 Abe T Adachi I Adamczyk K Ahn S Aihara H Akai K Aloi M Andricek L Aoki K Arai Y Arefiev A 2010 11 01 Belle II Technical Design Report arXiv 1011 0352 physics ins det Casarosa Giulia 2015 Inner tracking devices at the Belle II experiment Proceedings 2015 European Physical Society Conference on High Energy Physics EPS HEP 2015 Vienna Austria July 22 29 2015 p 255 Belle II Germany Meeting indico belle2 org Indico Retrieved 2022 01 11 Nishida S et al 2014 Aerogel RICH for the Belle II forward PID Nuclear Instruments and Methods in Physics Research Section A 766 28 31 Bibcode 2014NIMPA 766 28N doi 10 1016 j nima 2014 06 061 Inami Kenji 2014 TOP counter for particle identification at the Belle II experiment Nuclear Instruments and Methods in Physics Research Section A 766 5 8 Bibcode 2014NIMPA 766 5I doi 10 1016 j nima 2014 07 006 Electromagnetic Calorimeter Belle II Experiment belle2 jp Retrieved 2017 05 07 Aushev T et al 2015 A scintillator based endcap KL and muon detector for the Belle II experiment Nuclear Instruments and Methods in Physics Research Section A 789 134 142 arXiv 1406 3267 Bibcode 2015NIMPA 789 134A doi 10 1016 j nima 2015 03 060 S2CID 118613296 N Braun Hadron Spectroscopy Studies at Belle II Belle II Erfolgreicher Einbau des BEAST Detektors www mpp mpg de in German Retrieved 2022 01 11 belle2collab 22 November 2018 VerteX Detector VXD successfully installed in Belle2 The Belle II detector is now complete Tweet via Twitter Kick off of the Belle II Phase 3 Physics Run KEK reclaims luminosity record CERN Courier 2020 06 30 Retrieved 2022 01 11 Belle II www belle2 org Retrieved 2022 08 03 Contact www belle2 org Retrieved 2022 01 03 Public GeneralSlides Belle II DESY Confluence confluence desy de Retrieved 2022 01 03 Kuhr T Pulvermacher C Ritter M Hauth T Braun N December 2019 The Belle II Core Software Computing and Software for Big Science 3 1 1 arXiv 1809 04299 doi 10 1007 s41781 018 0017 9 ISSN 2510 2036 S2CID 119342160 The Belle II Collaboration 2021 10 19 Belle II Analysis Software Framework basf2 doi 10 5281 zenodo 5574115 retrieved 2022 01 07 a b The Belle II Collaboration 2021 Search belle2 basf2 GitHub doi 10 5281 zenodo 5574115 Retrieved 2022 01 07 External links Edit Wikimedia Commons has media related to Belle II experiment Belle II public webpage Belle II collaboration webpage German Belle II webpage A Search for New Physics The Belle II Experiment Inside Japan s big physics Belle II Record for SuperKEKB Belle II experiment on INSPIRE HEP Record for SuperKEKB project on INSPIRE HEP Retrieved from https en wikipedia org w index php title Belle II experiment amp oldid 1134319996, wikipedia, wiki, book, books, library,

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