CP Violation in D0 - anti-D0 Oscillations: General Considerations and Applications to the Littlest Higgs Model with T-Parity

The observed D0 - anti-D0 oscillations provide a new stage in our search for New Physics in heavy flavour dynamics. The theoretical verdict on the observed values of x_D and y_D remains ambiguous: while they could be totally generated by Standard Model dynamics, they could also contain a sizable or even leading contribution from New Physics. Those oscillations are likely to enhance the observability of CP violation as clear manifestations of New Physics. We present general formulae for D0 - anti-D0 oscillations, concentrating on the case of negligible direct CP violation. In particular we derive a general formula for the time-dependent mixing-induced CP asymmetry in decays to a CP eigenstate and its correlation with the semileptonic CP asymmetry a_SL(D0) in D0(t) -> l nu K. We apply our formalism to the Littlest Higgs model with T-parity, using the time-dependent CP asymmetry in D -> K_S phi as an example. We find observable effects at a level well beyond anything possible with CKM dynamics. Comparisons with CP violation in the K and B systems offer an excellent test of this scenario and reveal the specific pattern of flavour and CP violation in the D0 - anti-D0 system predicted by this model. We discuss a number of charm decays that could potentially offer an insight in the dynamics of CP violation in D decays. We also apply our formalism to B_s - anti-B_s mixing.Comment: 26 pages, 9 png figures, 1 table. v2: eq. (A.1) corrected, minor clarifying comments and few references added. v3: typos corrected, matches published versio

Top quark chromomagnetic dipole moment in the littlest Higgs model with T-parity

The littlest Higgs model with T-parity, which is called $LHT$ model, predicts the existence of the new particles, such as heavy top quark, heavy gauge bosons, and mirror fermions. We calculate the one-loop contributions of these new particles to the top quark chromomagnetic dipole moment $(CMDM)$ $\Delta K$. We find that the contribution of the $LHT$ model is one order of magnitude smaller than the standard model prediction value.Comment: latex files, 12 pages, 3 figure

Minimal Flavour Violation and Beyond

Starting from the effective-theory framework for Minimal Flavour Violation, we give a systematic definition of next-to-minimal (quark) flavour violation in terms of a set of spurion fields exhibiting a particular hierarchy with respect to a small (Wolfenstein-like) parameter. A few illustrative examples and their consequences for charged and neutral decays with different quark chiralities are worked out in some detail. Our framework can be used as a model-independent classification scheme for the parameterization of flavour structure from physics beyond the Standard Model.Comment: 17 pages, no figures, phenomenological discussion extended, references adde

Brief review of the searches for the rare decays Bs0→μ+μ−B^0_s \rightarrow \mu^+ \mu^- and B0→μ+μ−B^0 \rightarrow \mu^+ \mu^-

The current experimental status of the searches for the very rare decays $B^0_s \rightarrow \mu^+ \mu^-$ and $B^0 \rightarrow \mu^+ \mu^-$ is discussed. These channels are highly sensitive to various extensions of the Standard Model, specially in the scalar and pseudoscalar sector. The recent, most sensitive measurements from the CDF, ATLAS, CMS and LHCb collaborations are discussed and the combined upper exclusion limit on the branching fractions determined by the LHC experiments is shown to be $4.2\times 10^{-9}$ for $B^0_s \rightarrow \mu^+ \mu^-$ and $0.8\times 10^{-9}$ for $B^0 \rightarrow \mu^+ \mu^-$. The implications of these tight bounds on a selected set of New Physics models is sketched.Comment: 20 pages, 15 figures, invited review for Modern Physics Letters

Precise limits from lepton flavour violating processes on the Littlest Higgs model with T-parity

We recalculate the leading one-loop contributions to mu > e gamma and mu -> eee in the Littlest Higgs model with T-parity, recovering previous results for the former. When all the Goldstone interactions are taken into account, the latter is also ultraviolet finite. The present experimental limits on these processes require a somewhat heavy effective scale ~2.5 TeV, or the flavour alignment of the Yukawa couplings of light and heavy leptons at the ~10% level, or the splitting of heavy lepton masses to a similar precision. Present limits on tau decays set no bounds on the corresponding parameters involving the tau leptonComment: 41 pages, 11 figures; v3: matches published version in JHE

Photon-induced production of the mirror quarks from the LHTLHT model at the LHCLHC

The photon-induced processes at the $LHC$ provide clean experimental conditions due to absence of the proton remnants, which might produce complementary and interesting results for tests of the standard model and for searching of new physics. In the context of the littlest $Higgs$ model with T-parity, we consider the photon-induced production of the mirror quarks at the $LHC$. The cross sections for various production channels are calculated and a simply phenomenology analysis is performed by assuming leptonic decays.Comment: 20 pages, 10 figure

Electroweak and Flavour Structure of a Warped Extra Dimension with Custodial Protection

We present the electroweak and flavour structure of a model with a warped extra dimension and the bulk gauge group SU(3) x SU(2)_L x SU(2)_R x P_LR x U(1)_X. The presence of SU(2)_R implies an unbroken custodial symmetry in the Higgs system allowing to eliminate large contributions to the T parameter, whereas the P_LR symmetry and the enlarged fermion representations provide a custodial symmetry for flavour diagonal and flavour changing couplings of the SM Z boson to left-handed down-type quarks. We diagonalise analytically the mass matrices of charged and neutral gauge bosons including the first KK modes. We present the mass matrices for quarks including heavy KK modes and discuss the neutral and charged currents involving light and heavy fields. We give the corresponding complete set of Feynman rules in the unitary gauge.Comment: 74 pages, 2 figures. clarifying comments and references added, version to be published in JHE

On CP Asymmetries in Two-, Three- and Four-Body D Decays

Indirect and direct CP violations have been established in K_L and B_d decays. They have been found in two-body decay channels -- with the exception of K_L to pi^+ pi^- e^+ e^- transitions. Evidence for direct CP asymmetry has just appeared in LHCb data on A_{CP}(D^0 to K^+ K^-) - A_{CP}(D^0 to pi^+ pi^-) with 3.5 sigma significance. Manifestations of New Dynamics (ND) can appear in CP asymmetries just below experimental bounds. We discuss D^{\pm}_{(s)}, D^0/\bar D^0 and D_L/D_S transitions to 2-, 3- and 4-body final states with a comment on predictions for inclusive vs. exclusive CP asymmetries. In particular we discuss T asymmetries in D to h_1 h_2 l^+ l^- in analogy with K_L to pi^+ pi^- e^+ e^- transitions due to interference between M1, internal bremsstrahlung and possible E1 amplitudes. Such an effect depends on the strength of CP violation originating from the ND -- as discussed here for Little Higgs Models with T parity and non-minimal Higgs sectors -- but also in the interferences between these amplitudes even in the Standard Model (SM). More general lessons can be learnt for T asymmetries in non-leptonic D decays like D to h_1h_2 h_3 h_4. Such manifestations of ND can be tested at LHCb and other Super-Flavour Factories like the projects at KEK near Tokyo and at Tor Vergata/Frascati near Rome.Comment: 27 pages, 6 figures. Revised with current results from LHCb and HFAG and further interpretation

The Impact of a 4th Generation on Mixing and CP Violation in the Charm System

We study D0-D0 mixing in the presence of a fourth generation of quarks. In particular, we calculate the size of the allowed CP violation which is found at the observable level well beyond anything possible with CKM dynamics. We calculate the semileptonic asymmetry a_SL and the mixing induced CP asymmetry eta_fS_f which are correlated with each other. We also investigate the correlation of eta_fS_f with a number of prominent observables in other mesonic systems like epsilon'/epsilon, Br(K_L -> pi0 nu nu), Br(K+ -> pi+ nu nu), Br(B_s ->mu+ mu-), Br(B_d -> mu+ mu-) and finally S_psi phi in the B_s system. We identify a clear pattern of flavour and CP violation predicted by the SM4 model: While simultaneous large 4G effects in the K and D systems are possible, accompanying large NP effects in the B_d system are disfavoured. However this behaviour is not as pronounced as found for the LHT and RSc models. In contrast to this, sizeable CP violating effects in the B_s system are possible unless extreme effects in eta_fS_f are found, and Br(B_s ->mu+ mu-) can be strongly enhanced regardless of the situation in the D system. We find that, on the other hand, S_psi phi > 0.2 combined with the measured epsilon'/epsilon significantly diminishes 4G effects within the D system.Comment: 22 pages, 23 figures, v2 (references added

Particle-Antiparticle Mixing, epsilon_K, Delta Gamma_q, A_SL^q, A_CP(B_d -> psi K_S), A_CP(B_s -> psi phi) and B -> X_{s,d} gamma in the Littlest Higgs Model with T-Parity

We calculate a number of observables related to particle-antiparticle mixing in the Littlest Higgs model with T-parity (LHT). The resulting effective Hamiltonian for Delta F=2 transitions agrees with the one of Hubisz et al., but our phenomenological analysis goes far beyond the one of these authors. In particular, we point out that the presence of mirror fermions with new flavour and CP-violating interactions allows to remove the possible Standard Model (SM) discrepancy between the CP asymmetry S_{psi K_S} and large values of |V_ub| and to obtain for the mass difference Delta M_s < (Delta M_s)_SM as suggested by the recent result by the CDF collaboration. We also identify a scenario in which simultaneously significant enhancements of the CP asymmetries S_{phi psi} and A_SL^q relative to the SM are possible, while satisfying all existing constraints, in particular from the B -> X_s gamma decay and A_CP(B -> X_s gamma) that are presented in the LHT model here for the first time. In another scenario the second, non-SM, value for the angle gamma=-(109+-6) from tree level decays, although unlikely, can be made consistent with all existing data with the help of mirror fermions. We present a number of correlations between the observables in question and study the implications of our results for the mass spectrum and the weak mixing matrix of mirror fermions. In the most interesting scenarios, the latter one turns out to have a hierarchical structure that differs significantly from the CKM one.Comment: 51 pages, 20 figures, 1 table. Extended discussion of the phases in the new mixing matrix V_Hd, some references added or updated, conclusions unchanged. Final version published in JHE