1,667 research outputs found

### The B -> pi pi, pi K Puzzles: Implications for Hadron Physics, New Physics and Rare Decays

The B-meson system is an interesting probe for the exploration of strong
interactions, the quark-flavour sector of the Standard Model, and the search
for new physics. In this programme, non-leptonic B decays, which are
particularly challenging from the point of view of QCD, play a key role. After
discussing strategies to deal with the corresponding hadronic matrix elements
of four-quark operators and popular avenues for new physics to manifest itself
in B decays, we focus on puzzling patterns in the B-factory data for B -> pi
pi, pi K decays; we explore their implications for hadron physics, new physics
and rare K and B decays.Comment: 10 pages, 2 figures, plenary talk at the International Conference on
QCD and Hadronic Physics, Peking University, Beijing, China, 16-20 June 2005,
to appear in the Proceeding

### Waiting for Clear Signals of New Physics in B and K Decays

We classify the extensions of the Standard Model (SM) according to the
structure of local operators in the weak effective Hamiltonian and the presence
or absence of new flavour and CP-violating interactions beyond those
represented by the CKM matrix. In particular we review characteristic
properties of models with minimal flavour violation (MFV), models with
significant contributions from Higgs penguins and models with enhanced Z^0
penguins carrying a large new CP-violating phase. Within the latter models, the
anomalous behaviour of certain B\to\pi K observables implies large departures
from the SM predictions for rare and CP-violating K and B decays. Most
spectacular is the enhancement of Br(K_L->pi^0 nu nubar) by one order of
magnitude and a strong violation of the MFV relation
(\sin2\beta)_{\pi\nu\bar\nu}=(\sin2\beta)_{\psi K_S}. On the other hand our
prediction for (\sin2\beta)_{\phi K_S}\approx 0.9 differs from the Belle result
by the sign but is consistent with the BaBar value. We give a personal shopping
list for the coming years.Comment: Main latex-file, 4 figures, 22 page

### The B -> pi K Puzzle and its Relation to Rare B and K Decays

The Standard-Model interpretation of the ratios of charged and neutral B-> pi
K rates, R_c and R_n, respectively, points towards a puzzling picture. Since
these observables are affected significantly by colour-allowed electroweak (EW)
penguins, this ``B -> pi K puzzle'' could be a manifestation of new physics in
the EW penguin sector. Performing the analysis in the R_n-R_c plane, which is
very suitable for monitoring various effects, we demonstrate that we may, in
fact, move straightforwardly to the experimental region in this plane through
an enhancement of the relevant EW penguin parameter q. We derive analytical
bounds for q in terms of a quantity L, that measures the violation of the
Lipkin sum rule, and point out that strong phases around 90 deg are favoured by
the data, in contrast to QCD factorisation. The B -> pi K modes imply a
correlation between q and the angle gamma that in the limit of negligible
rescattering effects and colour suppressed EW penguins depends only on the
value of L. Concentrating on a minimal flavour-violating new-physics scenario
with enhanced Z^0 penguins, we find that the current experimental values on
B -> X_s mu^+ mu^- require roughly L pi K data give L =
5.7 +- 2.4, L has either to move to smaller values once the B -> pi K data
improve or new sources of flavour and CP violation are needed. In turn, the
enhanced values of L seen in the B -> pi K data could be accompanied by
enhanced branching ratios for rare decays. Most interesting turns out to be the
correlation between the B -> pi K modes and BR(K^+ -> pi^+ nu nu), with the
latter depending approximately on a single ``scaling'' variable \bar L= L
(|V_{ub}/V_{cb}|/0.086)^2.3.Comment: 19 pages, 7 figures, a few typos corrected and two references adde

### Limitations in Measuring the Angle $\beta$ by Using $SU(3)$ Relations for $B$-Meson Decay-Amplitudes

Flavour $SU(3)$ symmetry of strong interactions and certain dynamical
assumptions have been used in a series of recent publications to extract weak
CKM phases from $B$-decays into $\{\pi\pi,\pi K, K\bar K\}$ final states. We
point out that irrespectively of $SU(3)$-breaking effects the presence of
QCD-penguin contributions with internal $u$- and $c$-quarks precludes a clean
determination of the angle $\beta$ in the unitarity triangle by using the
branching ratios only. This difficulty can be overcome by measuring in addition
the ratio $x_d/x_s$ of $B^0_d-\bar B^0_d$ to $B^0_s-\bar B^0_s$ mixings. The
measurement of the angle $\gamma$ is unaffected by these new contributions.
Some specific uncertainties related to $SU(3)$-breaking effects and electroweak
penguin contributions are briefly discussed.Comment: 15 pages (LaTeX) + 5 figures included, Munich Technical University
preprint TUM-T31-69/9

### On fermion masses and mixing in a model with $A_4$ symmetry

In a recently proposed multi-Higgs extension of the standard model in which
discrete symmetries, $A_4$ and $Z_3$ are imposed we show that, after
accommodating the fermion masses and the mixing matrices in the charged
currents, the mixing matrices in the neutral currents induced by neutral
scalars are numerically obtained. However, the flavor changing neutral currents
are under control mainly by mixing and/or mass suppressions in the neutral
scalar sector.Comment: Version accepted for publication in International Journal of Modern
Physics A. In this version we added a discussion on the charged lepton and
neutrino masses. The title has been changed. Other minor changes do not
modify the conclusion

### New Aspects of B -> pi pi, pi K and their Implications for Rare Decays

We analyse the B -> pi pi, pi K modes in the light of the most recent
B-factory data, and obtain the following new results: (i) the B0 -> pi+ pi-,
pi- K+ modes prefer gamma=(74+-6)deg, which - together with |V_ub/V_cb| -
allows us to determine the ``true'' unitarity triangle and to search for
CP-violating new-physics contributions to B0_d-\bar B0_d mixing; (ii) the B ->
pi K puzzle reflected in particular by the low experimental value of the ratio
R_n of the neutral B -> pi K rates persists and still favours new physics in
the electroweak penguin sector with a new CP-violating phase phi ~ -90deg,
although now also phi ~ +90deg can bring us rather close to the data; (iii) the
mixing-induced B0 -> pi0 K_S CP asymmetry is a sensitive probe of the sign of
this phase, and would currently favour phi ~ +90deg, as well as the direct CP
asymmetry of B+- -> pi0 K+-, which suffers, however, from large hadronic
uncertainties; (iv) we investigate the sensitivity of our B -> pi K analysis to
large non-factorizable SU(3)-breaking effects and find that their impact is
surprisingly small so that it is indeed exciting to speculate on new physics;
(v) assuming that new physics enters through Z0 penguins, we study the
interplay between B -> pi K and rare B, K decays and point out that the most
recent B-factory constraints for the latter have interesting implications,
bringing us to a few scenarios for the future evolution of the data, where also
the mixing-induced CP violation in B0 -> pi0 K_S plays a prominent role.Comment: Two references added, to appear in the European Physical Journal

### Randall-Sundrum Corrections to the Width Difference and CP-Violating Phase in $B^0_s$-Meson Decays

We study the impact of the Randall-Sundrum setup on the width difference
$\Delta\Gamma_s$ and the CP-violating phase $\phi_s$ in the $\bar
B_s^0$-$B_s^0$ system. Our calculations are performed in the general framework
of an effective theory, based on operator product expansion. The result can
thus be used for many new physics models. We find that the correction to the
magnitude of the decay amplitude $\Gamma_{12}$ is below 4% for a realistic
choice of input parameters. The main modification in the
$\Delta\Gamma_s/\beta_s$-plane is caused by a new CP-violating phase in the
mixing amplitude, which allows for a better agreement with the experimental
results of CDF and D\O from $B_s^0\rightarrow J/\psi\phi\,$ decays. The
best-fit value of the CP asymmetry $S_{\psi\phi}$ can be reproduced, while
simultaneously the theoretical prediction for the semileptonic CP asymmetry
$A_{\rm SL}^s$ can enter the $1\sigma$ range.Comment: 12 pages, 1 table, 3 figures, references added, comments added, minor
correction in numerics, conclusions unchanged, accepted for publication in
Physical Review

### Strong Phases in the Decays B to pi pi

Two sources of strong phases in the decays $B$ to $\pi\pi$ are identified:
(1) "quasi-elastic scattering" corresponding to intermediate states like
$\pi\pi$ and $\rho\rho$, (2) ``$c\bar{c}$'' corresponding to intermediate
states like $D\bar{D}$ and $D^{*}\bar{D}^{*}$. Possibilities of using data to
identify these two sources are discussed and illustrated. Present data suggests
both sources may be significant.Comment: 6 pages, 1 figure

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