The general LHCb physics
programme includes a large sample of precise measurements which will
give information on physics beyond the Standard Model,
in a manner which is complementary to the direct particle searches carried
out at ATLAS and CMS.
The primary interest of B decays lies
in the multitude of modes which can be studied to learn more about CP
violation. In the mixing processes (see Feynman box diagrams below) new
physics particles can appear in these loops, giving signatures inconsistent
with the Standard Model. These signatures can be looked at by precise
measurements of the Bs oscillation parameter Δ ms.
Similarly to the mixing scenarios, new physics particles can appear in the
Bd(s) → hh -where h can be a π or a K- loop
diagram (see the Feynman diagram for the
Bd → K+ π- decays
below).
Furthermore, the combined measurement of the Bd → ππ
and of the Bs → KK time-dependent CP
asymmetries allows to determine the Unitarity Triangle angle γ
up to U-spin flavour symmetry breaking corrections.
More details on the RAL activities available here .
The Unitarity Triangle angle γ can also be measured by means of the
combined Gronau-London-Wyler (GLW) and Atwood Dunietz-Soni (ADS) methods
in the Bd → DK* decays.
The advantage of this method is that is a self-tagged method where the tag
of the B can be determined from the tag of the K*.
More details available here
.
Flavor Changing Neutral Currents (FCNC) are forbidden in the Standard Model at
the tree level by the GIM mechanism.
As a consequence FCNC only appear in the Standard Model when 2nd
order loop diagrams are considered. Therefore decays which depend on FCNC,
so-called rare decays, are very sensitive to ``new physics'' phenomena,
where, in addition, a strong dependence on virtually exchanged particles
might be observed. Loop decays, which then become the dominant contribution,
are very sensitive to ``new physics'' phenomena, due to a strong dependence
on virtually exchanged particles; this is the reason why these decays can
provide very sensitive tests of the Standard Model.
A typical example is given by the Bs → φμμ.
J.Nardulli@rl.ac.uk