2,070 research outputs found
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
Emerging -Anomaly from Tree-Level Determinations of and the Angle
We point out that the recently increased value of the angle in the
Unitarity Triangle (UT), determined in tree-level decays to be
by the LHCb collaboration, combined with
the most recent value of implies an enhancement of
over the data in the ballpark of . This is roughly by a factor of two
larger than the enhancement of that is independent of .
This disparity of enhancements is problematic for models with Constrained
Minimal Flavour Violation (CMFV) and also for models. In view of the
prospects of measuring with the precision of by Belle II
and LHCb in the coming years, we propose to use the angles and
together with and as the fundamental parameters of the
CKM matrix until from tree-level decays will be known precisely.
Displaying as functions of clearly demonstrates the
tension between the value of from tree-level decays, free from new
physics (NP) contributions, and calculated in CMFV and
models and thus exhibits the presence of NP contributions to beyond these frameworks. We calculate the values of and
as functions of and and discuss the implications
of our results for and rare and decays. We also briefly
discuss a future strategy in which , possibly affected by NP, is
replaced by .Comment: 15 pages, 8 figures, 3 tables. v2: Clarifying comments and one figure
added, conclusions unchanged. Matches published versio
Messages on Flavour Physics Beyond the Standard Model
I present a brief summary of the main results on flavour physics beyond the
Standard Model that have been obtained in 2008 by my collaborators and myself
at the TUM. In particular I list main messages coming from our analyses of
flavour and CP-violating processes in Supersymmetry, the Littlest Higgs model
with T-Parity and a warped extra dimension model with custodial protection for
flavour violating boson couplings.Comment: 7 pages, no figures, espcrc.sty Talk given at the Second Workshop on
Theory, Phenomenology and Experiments in Heavy Flavour Physics, June 16-18,
2008, Capri, Ital
Rare K and B Decays in a Warped Extra Dimension with Custodial Protection
We present a complete study of rare K and B meson decays in a warped extra
dimensional model with a custodial protection of (both diagonal and
non-diagonal) Z d_L^i \bar d_L^j couplings, including K^+ -> pi^+ nu anti-nu,
K_L -> pi^0 nu anti-nu, K_L -> pi^0 l^+ l^-, K_L -> mu^+ mu^-, B_{s,d} -> mu^+
mu^-, B -> K nu anti-nu, B -> K^* nu anti-nu and B -> X_{s,d} nu anti-nu. In
this model in addition to Standard Model one loop contributions these processes
receive tree level contributions from the Z boson and the new heavy electroweak
gauge bosons. We analyse all these contributions that turn out to be dominated
by tree level Z boson exchanges governed by right-handed couplings to down-type
quarks. Imposing all existing constraints from Delta F=2 transitions analysed
by us recently and fitting all quark masses and CKM mixing parameters we find
that a number of branching ratios for rare K decays can differ significantly
from the SM predictions, while the corresponding effects in rare B decays are
modest, dominantly due to the custodial protection being more effective in B
decays than in K decays. In order to reduce the parameter dependence we study
correlations between various observables within the K system, within the B
system and in particular between K and B systems, and also between Delta F=2
and Delta F=1 observables. These correlations allow for a clear distinction
between this new physics scenario and models with minimal flavour violation or
the Littlest Higgs Model with T-parity, and could give an opportunity to future
experiments to confirm or rule out the model. We show how our results would
change if the custodial protection of Z d_L^i bar d^j_L couplings was absent.
In the case of rare B decays the modifications are spectacular.Comment: 50 pages, 17 figures. v2: minor clarifying comments and references
added. v3: few clarifying comments added, 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 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 . We find that the contribution of the model is one order of magnitude
smaller than the standard model prediction value.Comment: latex files, 12 pages, 3 figure
Brief review of the searches for the rare decays and
The current experimental status of the searches for the very rare decays
and 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 for and for . 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
FCNC Processes in the Littlest Higgs Model with T-Parity: an Update
We update our 2006-2007 results for FCNC processes in the Littlest Higgs
model with T-parity (LHT). The removal of the logarithmic UV cutoff dependence
in our previous results through a new contribution to the Z^0-penguin diagrams
identified by Goto et al. and del Aguila et al., while making the deviations
from the SM expectations in the quark sector less spectacular, still allows for
sizable new physics effects in K -> pi nu anti-nu and K_L -> pi^0 l^+ l^-
decays and in the CP-asymmetry S_{psi phi} with the latter unaffected by the
new contribution. We extend our analysis by a study of the fine-tuning required
to fit the data on epsilon_K and by the inclusion of the decay K_L -> mu^+
mu^-. A number of correlations can distinguish this model from the custodially
protected Randall-Sundrum model analysed recently. We also reconsider lepton
flavour violating decays, including now a discussion of fine-tuning. While the
l_i -> l_j gamma decays are unaffected by the removal of the logarithmic cutoff
dependence, the branching ratios for decays with three leptons in the final
state, like mu -> 3 e are lowered by almost an order of magnitude. In spite of
this, the pattern of lepton flavour violation in the LHT model can still be
distinguished from the one in supersymmetric models.Comment: 30 pages, 14 figures, 5 tables. Clarifying comments added, matches
published versio
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