68 research outputs found
Theory of CP violation in B decays
The study of CP violation in -meson decays has already reached a high
level of precision, which will be pushed even higher in the future era of
Belle-II and the LHCb upgrade. %Important probes of CP violation are the
and mixing phases and the CKM angle . Here, the
theoretical challenge is to control the uncertainties from strong interactions
to distinguish between the Standard Model and possible New Physics effects. In
this talk, I will present a selected overview of recent theoretical
developments in this field. This includes, in particular, the semileptonic
asymmetry and extractions of the CKM angle and the
and mixing phases. I focus on recently proposed strategies in
which the theory uncertainties can be controlled through data using flavour
symmetries of the strong interaction. A newly found puzzle in the
system is highlighted and a theoretically clean way to determine the underlying
electroweak penguin parameters is discussed. Finally, the recent progress to
describe three-body decays in QCD factorization is discussed.Comment: To be published in the proceedings of The International Conference on
B-Physics at Frontier Machines - BEAUTY2018, La Biodola, Elba Island, Italy,
6-11 May, 2018 and in the proceedings of the XIV International Conference on
Heavy Quarks and Leptons (HQL2018), Yamagata, Japan, May 27- June 1, 201
Towards New Frontiers with Decays
Exploring correlations between the CP asymmetries of
following from an isospin relation, we uncover new tensions with the Standard
Model in data for neutral decays. Should this intriguing picture
originate from New Physics, a modified electroweak penguin sector provides a
key scenario. It includes models with extra bosons, which offer attractive
ways to resolve anomalies in measurements. We
present a new strategy to reveal the underlying physics, apply it to current
data, and discuss the excellent prospects for Belle II.Comment: 7 pages, 3 figure
determination from inclusive decays: an alternative method
The determination of relies on the Heavy-Quark Expansion and the
extraction of the non-perturbative matrix elements from inclusive
decays. The proliferation of these matrix elements complicates their extraction
at and higher, thereby limiting the extraction.
Reparametrization invariance links different operators in the Heavy-Quark
expansion thus reducing the number of independent operators at to
eight for the total rate. We show that this reduction also holds for spectral
moments as long as they are defined by reparametrization invariant
weight-functions. This is valid in particular for the leptonic invariant mass
spectrum (), i.e. the differential rate and its moments. Currently,
is determined by fitting the energy and hadronic mass moments, which
do not manifest this parameter reduction and depend on the full set of 13
matrix elements up to . In light of this, we propose an experimental
analysis of the moments to open the possibility of a model-independent
extraction from semileptonic decays including the terms in a
fully data-driven way.Comment: 16 pages, 2 figures. v2: version published in JHEP, references added
plus minor change
Reparametrization Invariance and Partial Re-Summations of the Heavy Quark Expansion
We extend existing work on reparametrization invariance (RPI) of the
heavy-quark expansion. We discuss the total rates of inclusive processes and
obtain results which have a manifest RPI and can be expressed through matrix
elements of operators and states defined in full QCD. This approach leads to a
partial re-summation of higher-order terms in the heavy-quark expansion and has
the advantage that the number of independent parameters is reduced.Comment: 22 page
The heavy quark expansion for inclusive semileptonic charm decays revisited
The Heavy Quark Expansion (HQE) has become an extremely powerful tool in flavor physics. For charm decays, where the expansion parameters Ξ±(m) and Ξ/m are bigger than for bottom decays, it remains to be seen if the HQE can be applied with similar success. Nevertheless, to make optimal use of the plethora of data already available and coming in the near future, a better understanding of HQE for charm decays is crucial. This paper discusses in detail how the HQE for charm decays is set up, what is the role of four-quark (weak annihilation) operators and how this compares to the well understood bottom decays. Subtleties concerning radiative corrections and the charm mass scheme are briefly discussed. An experimental study of the relevant HQE hadronic matrix elements will then show if the HQE expansion for charm converges well enough. Besides serving as an important cross check for inclusive B decays, in the end, this study might open the road for inclusive |V| and |V| extractions
Alternative Treatment of the Quark Mass in the Heavy Quark Expansion
The treatment of the quark mass plays an important role when it comes to
increasing the precision of the predictions of the heavy quark expansion for
inclusive heavy hadron decays. Various short-distance mass schemes have been
invented to minimize the uncertainties induced by the quark mass, which needs
to be extracted from other, independent observables. We suggest to replace the
quark mass directly by an observable such as e.g. the inverse moments of the
cross section for hadrons. We investigate this alternative
strategy and study its impact on the perturbative series.Comment: 20 page
Five-particle contributions to the inclusive rare decays
We calculate tree-level contributions to the inclusive rare decays. At the partonic level they stem from the
five-particle process , with . While for transitions such five-body final states
contribute at the same order in the Wolfenstein expansion compared to the
three-body partonic decay, they are CKM suppressed in decays. In the
perturbative expansion, we include all leading-order contributions, as well as
partial next-to-leading order QCD and QED effects. In the case of the
differential branching ratio, we present all results completely analytically in
terms of polylogarithmic functions of at most weight three. We also consider
the differential forward-backward asymmetry, where all except one interference
could be obtained analytically. From a phenomenological point of view the newly
calculated contributions are at the percent level or below.Comment: 23 pages, 3 figures (Matches published version
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