Letter of Intent for KEK Super B Factory Part I: Physics

Entries / (0.2 GeV/c 2 )
300 (a) (b)
200
100
0
15
10
5
0
(c)
0 1 2 3 4
Mll (GeV/c 2 0 1 2 3
)
MXs (GeV/c 2 )
Figure 1.12: M(ℓ + ℓ − ) (left) and M(Xs) (right) distributions for B → Xsℓ + ℓ − from Belle (points
with error bars), compared with the Standard Model predictions before (top) and after (bottom)
including detector acceptance effects.
M(Xs) and M(ℓ + ℓ − ) are shown in Figure 1.12, in which no significant deviation from the
Standard Model is observed.
1.2.5 Prospects
With a data sample of ∼ 500 fb −1 , the statistical errors will be reduced to about half of the
present errors. The value of sin 2φ1 will be measured with an accuracy less than 5% using
b → ccs processes. Though uncertainties are still large, φ2 and φ3 will be measured. Together
with some improvement in |Vcb| and |Vub| measurements, the KM scheme for CP -violation will
be further confirmed. Direct CP -violation will be observed in several decay modes, which also
strongly supports the KM scheme.
Results will be available for new measurements that are sensitive to new physics, such as measurements
of forward-backward asymmetry of lepton-pairs in B → K (∗) ℓ + ℓ − , time-dependent
CP -violation of radiative decays, etc. If the effect of new physics is large, it may manifest
itself in the above ways in a similar fashion to the current indication of as the CP -violation in
b → sqq decays (if it remains as currently measured). However, the confirmation of the new
physics effects and understanding its nature will require much larger data samples, which will
be the primary goal of the proposed SuperKEKB and upgraded Belle detector in this LoI.
References
[1] S. L. Glashow, J. Iliopoulos and L. Maiani, “Weak Interactions With Lepton – Hadron
Symmetry,” Phys. Rev. D 2, 1285 (1970).
23
(d)