SuperKEKB [1] is a particle collider located at KEK (High Energy Accelerator Research Organisation) in Tsukuba, Ibaraki Prefecture, Japan. SuperKEKB collides electrons with positrons at the centre-of-momentum energy close to the mass of the Υ(4S) resonance making it a second-generation B-factory for the Belle II experiment. The accelerator is an upgrade to the KEKB accelerator, providing approximately 40 times higher luminosity, [2] due mostly to superconducting quadrupole focusing magnets. [1] The accelerator achieved "first turns" (first circulation of electron and positron beams) in February 2016. [3] First collisions occurred on 26 April 2018. [4] At 20:34 on 15 June 2020, SuperKEKB achieved the world’s highest instantaneous luminosity for a colliding-beam accelerator, setting a record of 2.22×1034 cm−2s−1. [5]
The SuperKEKB design reuses many components from KEKB. [1] Under normal operation, SuperKEKB collides electrons at 7 GeV with positrons at 4 GeV [2] (compared to KEKB at 8 GeV and 3.5 GeV respectively). The centre-of-momentum energy of the collisions is therefore at the mass of the Υ(4S) resonance (10.58 GeV/c2). [6] The accelerator will also perform short runs at energies of other Υ resonances, in order to obtain samples of other B mesons and baryons. [1] The asymmetry in the beam energy provides a relativistic Lorentz boost to the B meson particles produced in the collision. The direction of the higher-energy beam determines the 'forward' direction, and that affects the design of much of the Belle II detector.
As with KEKB, SuperKEKB consists of two storage rings: one for the high-energy electron beam (the High Energy Ring, HER) and one for the lower energy positron beam (the Low Energy Ring, LER). The accelerator has a circumference of 3016 m with four straight sections and experimental halls in the centre of each, named "Tsukuba", "Oho", "Fuji", and "Nikko". [2] The Belle II experiment is located at the single interaction point in Tsukuba Hall. [7]
The target luminosity for SuperKEKB is 6.5×1035 cm−2s−1, this is 30 times larger than the luminosity at KEKB. [8] The improvement is mostly due to a so-called 'nano-beam' scheme, originally proposed [9] for the cancelled [10] SuperB experiment. In the nano-beam scheme at SuperKEKB, the beams are squeezed in the vertical direction and the crossing angle is increased, which reduces the area of the crossing. [1] The luminosity is further increased by a factor of two, due to a higher beam current than KEKB. [1] The focus and crossing angle is achieved by two new superconducting quadrupole magnets at the interaction point [1] that were installed in February 2017. [11]
On June 15, 2020, SuperKEKB set a new world record for the highest instantaneous luminosity for a colliding-beam accelerator: 2.22×1034 cm−2s−1. (On June 21, 2020, SuperKEKB broke its own record and achieved an instantaneous luminosity of 2.40×1034 cm−2s−1.) The previous world record of 2.14×1034 cm−2s−1 was achieved by LHC in 2018. [12] [13]
SuperKEKB [1] is a particle collider located at KEK (High Energy Accelerator Research Organisation) in Tsukuba, Ibaraki Prefecture, Japan. SuperKEKB collides electrons with positrons at the centre-of-momentum energy close to the mass of the Υ(4S) resonance making it a second-generation B-factory for the Belle II experiment. The accelerator is an upgrade to the KEKB accelerator, providing approximately 40 times higher luminosity, [2] due mostly to superconducting quadrupole focusing magnets. [1] The accelerator achieved "first turns" (first circulation of electron and positron beams) in February 2016. [3] First collisions occurred on 26 April 2018. [4] At 20:34 on 15 June 2020, SuperKEKB achieved the world’s highest instantaneous luminosity for a colliding-beam accelerator, setting a record of 2.22×1034 cm−2s−1. [5]
The SuperKEKB design reuses many components from KEKB. [1] Under normal operation, SuperKEKB collides electrons at 7 GeV with positrons at 4 GeV [2] (compared to KEKB at 8 GeV and 3.5 GeV respectively). The centre-of-momentum energy of the collisions is therefore at the mass of the Υ(4S) resonance (10.58 GeV/c2). [6] The accelerator will also perform short runs at energies of other Υ resonances, in order to obtain samples of other B mesons and baryons. [1] The asymmetry in the beam energy provides a relativistic Lorentz boost to the B meson particles produced in the collision. The direction of the higher-energy beam determines the 'forward' direction, and that affects the design of much of the Belle II detector.
As with KEKB, SuperKEKB consists of two storage rings: one for the high-energy electron beam (the High Energy Ring, HER) and one for the lower energy positron beam (the Low Energy Ring, LER). The accelerator has a circumference of 3016 m with four straight sections and experimental halls in the centre of each, named "Tsukuba", "Oho", "Fuji", and "Nikko". [2] The Belle II experiment is located at the single interaction point in Tsukuba Hall. [7]
The target luminosity for SuperKEKB is 6.5×1035 cm−2s−1, this is 30 times larger than the luminosity at KEKB. [8] The improvement is mostly due to a so-called 'nano-beam' scheme, originally proposed [9] for the cancelled [10] SuperB experiment. In the nano-beam scheme at SuperKEKB, the beams are squeezed in the vertical direction and the crossing angle is increased, which reduces the area of the crossing. [1] The luminosity is further increased by a factor of two, due to a higher beam current than KEKB. [1] The focus and crossing angle is achieved by two new superconducting quadrupole magnets at the interaction point [1] that were installed in February 2017. [11]
On June 15, 2020, SuperKEKB set a new world record for the highest instantaneous luminosity for a colliding-beam accelerator: 2.22×1034 cm−2s−1. (On June 21, 2020, SuperKEKB broke its own record and achieved an instantaneous luminosity of 2.40×1034 cm−2s−1.) The previous world record of 2.14×1034 cm−2s−1 was achieved by LHC in 2018. [12] [13]