Stefan Recksiegel

Anatomy of prominent B and K decays and signatures of CP-violating new physics in the electroweak penguin sector

The recent observation of Bd → � 0 � 0 at the B factories with a surprisingly large branching ratio represents a challenge for theory, and complements the amazingly small Bd → � + � − rate. We point out that all puzzling B → �� features can be accommodated in the Standard Model (SM) through non-factorizable hadronic interference effects, extract the relevant parameters, and predict the CP asymmetries of Bd → � 0 � 0 . Using thenSU(3) flavour-symmetry and plausible dynamical assumptions, we fix the hadronicB → �K parameters through theirB → �� counterparts, and determine the CKM angle , with a result in remarkable accordance with the usual fits for the unitarity triangle. We may then analyse the B → �K system in the SM, where we find agreement with the experimental picture, with the exception of those observables that are significantly affected by electroweak (EW) penguins, thereby suggesting new physics (NP) in this sector. Indeed, a moderate enhancement of these topologies and a large CP-violating NP phase allow us to describe any currently observed feature of the B → �K modes, and to predict the CP-violating Bd → � 0 KS observables. If we then restrict ourselves to a specific scenario where NP enters only through Z 0 penguins, we obtain a link to rare K and B decays, where the most spectacular NP effects are an enhancement of the KL → � 0 �¯ rate by one order of magnitude with BR(KL → � 0 �¯

Rare and CP-Violating K and B Decays in the Littlest Higgs Model with T-Parity

We calculate the most interesting rare and CP-violating K and B decays in the Littlest Higgs model with T-parity. We give a collection of Feynman rules including v 2 =f 2 contributions that are presented here for the first time and could turn out to be useful also for applications outside flavour physics. We adopt a modelindependent parameterization of rare decays in terms of the gauge independent functions Xi; Yi; Zi (i = K;d;s), which is in particular useful for the study of the breaking of the universality between K, Bd and Bs systems through non-MFV interactions. Performing the calculation in the unitary and ’t Hooft-Feynman gauge, we find that the final result contains a divergence which signals some sensitivity to the ultraviolet completion of the theory. Including an estimate of this contribution, we calculate the branching ratios for the decays K + ! � + �¯ �, KL ! � 0 �¯, Bs;d ! � + � − , B ! Xs;d�¯ �, KL ! � 0 ` + ` − and B ! Xs;d` + ` − , paying particular

B ¿ pipi, New Physics in B ¿ piK, and Implications for Rare K and B Decays

The measured B-->pipi,piK branching ratios (BRs) exhibit puzzling patterns. We point out that the B-->pipi hierarchy can be nicely accommodated in the standard model (SM) through nonfactorizable hadronic interference effects, whereas the B-->piK system may indicate new physics (NP) in the electroweak (EW) penguin sector. Using the B-->pipi data and the SU(3) flavor symmetry, we fix the hadronic B-->piK parameters and show that any currently observed feature of the B-->piK system can be easily explained through enhanced EW penguin diagrams with a large CP-violating NP phase. This in turn implies in particular an enhancement of the K(L)-->pi(0)nunu rate by 1 order of magnitude, with BR(K(L)-->pi(0)nunu) approximately 4BR(K+-->pi(+)nunu), BR(K(L)-->pi(0)e(+)e(-))=O(10(-10)), and (sin(2beta)(pinunu)<0. We address also other rare K and B decays and B(d)-->phiK(S).

Another look at the flavour structure of the Littlest Higgs model with T-parity

Abstract We discuss the mixing matrix V H d that describes the charged and neutral current interactions between ordinary down-quarks and up- and down-mirror quarks in the Littlest Higgs model with T-parity (LHT). We point out that this matrix in addition to three mixing angles contains three physical complex phases and not only one as used in the present literature. We explain the reason for the presence of two additional phases, propose a new standard parameterization of V H d and briefly comment on the relevance of these new phases for the phenomenology of FCNC processes in the LHT model. In a separate paper we present a detailed numerical analysis, including these new phases, of K and B physics, with particular attention to the most interesting rare decays.

The effect of H^\pm on B^\pm -> \tau^\pm \nu and B^\pm -> \mu^\pm \nu

The hitherto unobserved purely leptonic decays B^\pm -> \tau^\pm \nu and B^\pm -> \mu^\pm \nu are of much interest at current and future runs of the e+e- B factories. Such decays are sensitive to charged Higgs bosons (H^\pm) at the tree-level and provide essentially model independent constraints on \tan\beta/m_{H^\pm}. We include the large corrections to the H^\pm-ub coupling induced by virtual SUSY effects and show that the bounds on \tan\beta/m_{H^\pm} can be significantly weakened or strengthened.The hitherto unobserved purely leptonic decays B± → τ±ντ and B± → μ±νμ are of much interest in current and future runs of the e+e−B factories. Such decays are sensitive to charged Higgs bosons (H±) at the tree-level and provide important constraints on tan β/mH±. We include the large corrections to the H±ub coupling induced by virtual SUSY effects and show that the bounds on tan β/mH± can be significantly weakened or strengthened.

The effect of H± on B± → τ±ντ and B± → μ±νμ

The hitherto unobserved purely leptonic decays B^\pm -> \tau^\pm \nu and B^\pm -> \mu^\pm \nu are of much interest at current and future runs of the e+e- B factories. Such decays are sensitive to charged Higgs bosons (H^\pm) at the tree-level and provide essentially model independent constraints on \tan\beta/m_{H^\pm}. We include the large corrections to the H^\pm-ub coupling induced by virtual SUSY effects and show that the bounds on \tan\beta/m_{H^\pm} can be significantly weakened or strengthened.The hitherto unobserved purely leptonic decays B± → τ±ντ and B± → μ±νμ are of much interest in current and future runs of the e+e−B factories. Such decays are sensitive to charged Higgs bosons (H±) at the tree-level and provide important constraints on tan β/mH±. We include the large corrections to the H±ub coupling induced by virtual SUSY effects and show that the bounds on tan β/mH± can be significantly weakened or strengthened.

The \(B\to\pi K\) puzzle and its relation to rare B and K decays

Abstract.The standard-model interpretation of the ratios of charged and neutral

Littlest Higgs model with T-parity confronting the new data on D0–D¯0 mixing

B\to\pi K

CP violation in D0−bar D0 oscillations: general considerations and applications to the Littlest Higgs model with T-parity

rates, Rc and Rn, respectively, points towards a puzzling picture. Since these observables are affected significantly by colour-allowed electroweak (EW) penguins, this “

Fine and hyperfine splittings of charmonium and bottomonium: an improved perturbative QCD approach

B\to\pi K