620
K. Hübner et al.
parameter of 0.13 has been achieved and that round beams give a solid luminosity
enhancement.
10.3.3.25 SUPERKEKB
SuperKEKB at KEK is an asymmetric two ring collider upgraded from KEKB and
made to measure CP violation in the BB system to extend the understanding of the
CKM matrix [118]. This collider has a 7.0 GeV High Energy Ring HER for e− and a
4.0 GeV Low Energy Ring LER for e+. The luminosity goal is 8 × 10 35 cm −2 s −1 .
The design beam currents will be doubled from KEK to 2.6 A on 3.6 A. The
nano-beam scheme for increased luminosity decreases the overlapping length of
colliding particles to about 0.25 mm with a 41.4 mrad half crossing angle [111]. The
interaction region beta functions will be about 30/0.3 mm (h/v) with a bunch length
of about 5.5 mm. The two rings without the interaction region were commissioning
in 2016 where 1.01 A of e− were successfully stored in the HER and 0.87 A of e+
stored in the LER. The installation of the interaction region will be completed in
early 2018 when luminosity commissioning will begin.
10.4 Asymmetric B-Factories
K. Oide
10.4.1 Physics Motivation
The idea of asymmetric B-factories was first introduced by P. Oddone in 1987
[119] to collide e + e − beams with different energies to measure the CP-asymmetry
between the decay of B 0 and B 0 mesons. The asymmetry of the energies of two
beams boosts the generated particles longitudinally, then the difference of the decay
time can be measured by the difference of the vertices, which was expected to be in
about an order of 100 μm. The center-of-mass energy of the collision is set to the
ϒ(4S) resonance at 10.58 GeV. A very high luminosity around 10 34 cm −2 s −1 was
required, which was more than 100 times higher than what had been achieved in
colliders by that time.
10.4.2 Double Ring Collider
There may be several ways to realize the asymmetric collision. One way is to build
a linear–linear or a ring–linear collider. Such a linear machine needs a very strong
K. Hübner et al.
parameter of 0.13 has been achieved and that round beams give a solid luminosity
enhancement.
10.3.3.25 SUPERKEKB
SuperKEKB at KEK is an asymmetric two ring collider upgraded from KEKB and
made to measure CP violation in the BB system to extend the understanding of the
CKM matrix [118]. This collider has a 7.0 GeV High Energy Ring HER for e− and a
4.0 GeV Low Energy Ring LER for e+. The luminosity goal is 8 × 10 35 cm −2 s −1 .
The design beam currents will be doubled from KEK to 2.6 A on 3.6 A. The
nano-beam scheme for increased luminosity decreases the overlapping length of
colliding particles to about 0.25 mm with a 41.4 mrad half crossing angle [111]. The
interaction region beta functions will be about 30/0.3 mm (h/v) with a bunch length
of about 5.5 mm. The two rings without the interaction region were commissioning
in 2016 where 1.01 A of e− were successfully stored in the HER and 0.87 A of e+
stored in the LER. The installation of the interaction region will be completed in
early 2018 when luminosity commissioning will begin.
10.4 Asymmetric B-Factories
K. Oide
10.4.1 Physics Motivation
The idea of asymmetric B-factories was first introduced by P. Oddone in 1987
[119] to collide e + e − beams with different energies to measure the CP-asymmetry
between the decay of B 0 and B 0 mesons. The asymmetry of the energies of two
beams boosts the generated particles longitudinally, then the difference of the decay
time can be measured by the difference of the vertices, which was expected to be in
about an order of 100 μm. The center-of-mass energy of the collision is set to the
ϒ(4S) resonance at 10.58 GeV. A very high luminosity around 10 34 cm −2 s −1 was
required, which was more than 100 times higher than what had been achieved in
colliders by that time.
10.4.2 Double Ring Collider
There may be several ways to realize the asymmetric collision. One way is to build
a linear–linear or a ring–linear collider. Such a linear machine needs a very strong