Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Precision tests with Kl3 and Kl2 decays   The analysis made in 2000 indicated that the unitarity relation Vud^2 + Vus^2
+ Vub^2 = 1 might be broken at the 2.3 sigma level. At that time, however, Vus
was inferred from old experimental data. Since then, a great experimental and
theoretical effort has been invested to understand the source of that
discrepancy. Thanks to the new and improved measurements by BNL-E865, KLOE,
KTeV, ISTRA+ and NA48, the old Kl3 decay rate got shifted so that the new Vus
is now consistent with unitarity. On the theory side, much progress in the
lattice QCD has been made in order to tame the systematic uncertainties related
to the computation of the Kl3 form factors.
  This joint progress allowed to assess the validity of the CKM unitarity
relation at the level of less than 1%. The key challenge of the future lattice
studies will be to simulate lighter pions in the region in which ChPT
predictions apply. Also interesting is the recent progress in accurately
computing the kaon and pion decay constants on the lattice, which then give us
access to Vus and Vud from the corresponding leptonic decays.
  In addition, we discuss that the Kl3 and Kl2 decays offer the possibility to
test various scenarios of physics beyond Standard Model.

27
The categories of this paper are: comp-gas
19
The categories of this paper are: eess
12
The categories of this paper are: nucl-th
6
The categories of this paper are: astro-ph
20
The categories of this paper are: acc-phys
28
The categories of this paper are: alg-geom
5
The categories of this paper are: gr-qc
11
The categories of this paper are: hep-lat
15
The categories of this paper are: nucl-ex
34
The categories of this paper are: chem-ph
2
The categories of this paper are: math
1
The categories of this paper are: cs
32
The categories of this paper are: atom-ph
33
The categories of this paper are: plasm-ph
30
The categories of this paper are: q-alg
8
The categories of this paper are: hep-ex