SuperKEKB SuperKEKB SuperKEKB— The leading accelerator on the luminosity frontier —The SuperKEKB accelerator aims to allow us to discover new physics phenomena by studying theinteractions of particles called B-mesons produced by the collisions of electrons and positrons (the antimattercounterpart of the electron, with a positive electrical charge).

Number of Events

The SuperKEKB accelerator aims to deliver an integrated luminosity of 50 abby achieving a peak luminosity about 30 times higher than KEKB.

400350300250200
150
100500One way to discover new physics phenomena is to use accelerators to reach higher and higher energies
of particle collisions, but it is not the only way. Producing an extremely high number of particles, allowing
for very precise measurements of their properties and decays allows the SuperKEKB accelerator to explore
physics phenomena that cannot be investigated just by increasing the energy of particle collisions. Thisapproach to discovering new physics is often called exploring the “luminosity frontier” and SuperKEKB,
which will produce a number of B-meson and anti-B-meson pairs far exceeding the number produced by its
predecessor, KEKB, will be at the forefront of the exploration of the luminosity frontier.

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The SuperKEKB accelerator consists of two rings, an electron ring and a positron ring, together with aninjector that supplies electrons and positrons to the rings. The two rings are located side-by-side in a tunnel
with a circumference of approximately 3 km, situated about 11 meters underground. During operations, theelectron beam (with an energy of 7 GeV) and the positron beam (4 GeV) are circulated in opposite directions
around each ring at close to the speed of light. The two beams are designed to collide at only one point,called the interaction point - this is where the Belle II detector is installed to record interactions of the particles
created by the collisions.

ＢＢ-6-4-20∆t(ps)

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Visualization of simulated interactions of dark matter-related particles
within the Belle II detector

Explore New Physics with SuperKEKB/Belle IIIn 2001, the Belle experiment and the KEKB accelerator discovered CP violation in the decays of B mesons. CP
violation refers to a difference between how matter and antimatter behave, and understanding this difference canhelp us explain how the early universe evolved to give rise to the matter dominated universe that we see around
us today. Belle was able to find a difference between the decay times of B mesons and anti-B mesons when0
they decay into specific types of particles, such as J/ψ and K s particles. A theoretical mechanism for CP violation
had been proposed in the 1960s, in what is now known as the Kobayashi-Maskawa Theory – the experimental
evidence from Belle and KEKB confirmed this theory, and led to Prof. Kobayashi and Prof. Maskawa being awarded
with a Nobel Prize for Physics in 2008.

The SuperKEKB accelerator isMore SuperKEKB }an electron-positron collider

http://www-superkekb.kek.jp

that was built to aid us
in our quest to unlock
the many mysteries ofelementary particle physics.

However, the amount of CP violation as observed and explained by the Kobayashi-Maskawa Theory is far
too small to explain the disappearance of the antimatter from the universe. Therefore there must be newphysics, beyond the well established Standard Model of particle physics, that provides additional sources of CPviolation. The SuperKEKB accelerator can produce a significantly higher number of B mesons than its predecessor,
KEKB – with a goal of collecting a dataset 50 times larger. This will allow SuperKEKB and Belle’s successor, Belle II, toplay a leading role in the search for new physics beyond the standard model.
High Energy Accelerator Research Organization / SuperKEKB Accelerator

2023.9High Energy Accelerator Research Organization / SuperKEKB Accelerator

A quantity called luminosity is used to describe the performance of an accelerator, with a higher luminosity
corresponding to a higher rate of particle collisions – to study rare physics phenomena an extremely highluminosity is required. The KEKB accelerator, the predecessor of SuperKEKB, achieved the world's highest
luminosity at the time. From 2001 onward, the KEKB accelerator broke the world record for luminosity
multiple times, eventually achieving a luminosity of more than twice its design value. The KEKB accelerator
ended its operations in June 2010 and was upgraded to become the SuperKEKB accelerator, in order toachieve an even higher luminosity.
Many accelerator upgrades and improvements were made with a goal of increasing the luminosity by
about 30 times compared with the KEKB accelerator; these included increasing the beam currents to 3.6 A(positron) and 2.6 A (electron), and reducing the dimensions of the particle beams to an extremely small
size (about 10 μm in width and 50 – 60 nm in height), resulting in beams that are sometimes referred to as“nanobeams”.
We will collect a very large dataset for physics research while continuing to achieve high luminosity withthe SuperKEKB accelerator.

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Central Control Room

4

SuperKEKBBeam Transport LineConducting
7 NormalCavities (ARES Cavities)

Main Rings (MR) (HER + LER)NIKKO

Control hundreds of thousands of machine parametersin the central control room.

2 Superconducting Cavities

Sextupole Magnets with
11 Variable Tilting Angles

9 Final focus system

Interaction Point(IP)93

TSUKUBA

38Transport electrons and positrons from LINAC to MR
efficiently.

32Accelerator
5 Linear(electron-positron LINAC)

Bunch by Bunch
14 Feedback

Those sextupole magnets with the tilting stage rotate ±30°around the beam axis to correct chromatic aberration.

134 Beam Transport Line

Suppresses beam instabilities.

12 Beam Position Monitors

15 Beam pipes

Beam position monitors that measure beam position
with precision of better than 4 μ m.

To keep high quality beams for a long time, the inside of
the metal beam pipes where the beams pass through areevacuated down to ultra high vacuum region (~10–8 Pa).

13 X-Ray Monitor

16 Damping Ring (DR)61
Stable acceleration of large beam currents by the uniquethree-cavity system. (ARES: Accelerator Resonantlycoupled with Energy Storage)

Provides electrons and positrons continuously to the MR.
Aiming to accumulate a beam current of 2.6 A. Japan's
world-leading superconducting acceleration technology.

3Cryogenic Cooling
System713OHO

7FUJI

8 Belle II Detector

14

The final focus system consisting of superconducting
magnets squeezes the beams at the interaction point.

10 Magnets

7

6 Klystrons

positron source
Electron Ring (e–)
HER
Positron Ring (e+)
LER

Beam Transport Line
Normal Conducting Cavities
Superconducting Cavities
Klystron

10 ～ 12 、15 is installed all aroundHelium gas is liquefied to cool the superconducting
accelerating cavity to 4K by the helium liquefaction
refrigeration system with low helium consumption.

The world's highest output radio frequency powersources are installed in NIKKO, FUJI, OHO, and DR.

Investigate the decay of B mesons produced in the SuperKEKB
accelerator and study elementary particle physics.

16 Damping Ring (DR)RF Electron Gun(electron source)

5 Linear Accelerator (LINAC)
There are about 1000 quadrupole magnets, 220
dipole magnets, 200 sextupole magnets and 1100
corrector magnets installed in the MR to control
the beams.

Monitors the vertical and horizontal beam size.

Decreases the dimensions of the positron beam toincrease the efficiency of injection into the MR.