6,347 research outputs found
Highlights of the B-Physics Landscape
The exploration of the quark-flavour sector of the Standard Model is one of
the hot topics in particle physics of this decade. In these studies, which show
a fruitful interplay between theory and experiment, the B-meson system offers a
particularly interesting laboratory. After giving an introduction to
quark-flavour mixing and CP violation as well as to the theoretical tools to
deal with non-leptonic B decays, we discuss popular avenues for new physics to
enter the roadmap of quark-flavour physics. This allows us to have a detailed
look at the B-factory benchmark modes , and , with a particular emphasis of the impact of new
physics. We then perform an analysis of the puzzle, which may
indicate new sources of CP violation in the electroweak penguin sector, and
discuss its implications for rare B and K decays. The next topic is given by
penguin processes, which are now starting to become accessible at the
B factories, thereby representing a new territory of the B-physics landscape.
Finally, we discuss the prospects for B-decay studies at the Large Hadron
Collider, where the -meson system plays an outstanding role.Comment: 64 pages, 19 figures, invited topical review for Journal of Physics
G: Nuclear and Particle Physic
Exploring CP Violation through B Decays
The B-meson system provides many strategies to perform stringent tests of the
Standard-Model description of CP violation. In this brief review, we discuss
implications of the currently available B-factory data on the angles alpha,
beta and gamma of the unitarity triangle, emphasize the importance of Bs
studies at hadronic B experiments, and discuss new, theoretically clean
strategies to determine gamma.Comment: 22 pages, 4 figures, invited brief review for Modern Physics Letters
B -> pi pi, New Physics in B -> pi K and Implications for Rare K and B Decays
The measured B -> pi pi, pi K branching ratios exhibit puzzling patterns. We
point out that the B -> pi pi hierarchy can be nicely accommodated in the
Standard Model (SM) through non-factorizable hadronic interference effects,
whereas the B -> pi K system may indicate new physics (NP) in the electroweak
(EW) penguin sector. Using the B -> pi pi data and the SU(3) flavour symmetry,
we may fix the hadronic B -> pi K parameters, which allows us to show that any
currently observed feature of the B -> pi K system can be easily explained
through enhanced EW penguins with a large CP-violating NP phase. Restricting
ourselves to a specific scenario, where NP enters only through Z^0 penguins, we
derive links to rare K and B decays, where an enhancement of the K_L-> pi^0 nu
nu_bar rate by one order of magnitude, with BR(K_L -> pi^0 nu nu_bar) > BR(K^+
-> pi^+ nu nu_bar), BR(K_L -> pi^0 e^+ e^-)=O(10^{-10}), (\sin2\beta)_{pi nu
nu_bar} K* mu^+ mu^-,
are the most spectacular effects. We address also other rare K and B decays,
epsilon'/epsilon and B_d -> phi K_S.Comment: 6 pages, LaTeX, reference added and a few typos correced, to appear
in Physical Review Letter
B Physics in the LHC Era: Selected Topics
We have just entered a new round in the testing of the flavour sector of the
Standard Model through high-precision measurements of B-meson decays. A
particularly exciting aspect is the exploration of the B_s-meson system at
LHCb. We focus on two particularly promising probes of new physics which may
give us first solid evidence for New Physics at the LHC: the strongly
suppressed rare decay B_s^0 -> mu^+mu^- and CP-violating effects in the B_s^0
-> J/psi phi channel. We discuss recent theoretical developments related to
these measurements and shall also sketch other highlights of the B-physics
programme in the LHC era.Comment: 8 pages, 3 figures, invited talk at the 3rd Workshop on Theory,
Phenomenology and Experiments in Heavy Flavour Physics, Capri, Italy, 5-7
July 2010, to appear in the Proceeding
Limitations in Measuring the Angle by Using Relations for -Meson Decay-Amplitudes
Flavour symmetry of strong interactions and certain dynamical
assumptions have been used in a series of recent publications to extract weak
CKM phases from -decays into final states. We
point out that irrespectively of -breaking effects the presence of
QCD-penguin contributions with internal - and -quarks precludes a clean
determination of the angle in the unitarity triangle by using the
branching ratios only. This difficulty can be overcome by measuring in addition
the ratio of to mixings. The
measurement of the angle is unaffected by these new contributions.
Some specific uncertainties related to -breaking effects and electroweak
penguin contributions are briefly discussed.Comment: 15 pages (LaTeX) + 5 figures included, Munich Technical University
preprint TUM-T31-69/9
In Pursuit of New Physics in the B System
The B-meson system offers interesting probes for the search of physics beyond
the Standard Model. After addressing possible signals of new-physics
contributions to the B -> phi K and B -> pi K decay amplitudes, we focus on the
data for B^0_q-\bar B^0_q mixing (q = d, s), giving a critical discussion of
their interpretation in terms of model-independent new-physics parameters. We
address, in particular, the impact of the uncertainties of the relevant input
parameters, discuss benchmarks for future precision measurements at the LHC,
and explore the prospects for new CP-violating effects in the B_s-meson system,
which could be detected at the LHC.Comment: 8 pages, 7 figures, invited talk at the 1st Workshop on Theory,
Phenomenology and Experiments in Heavy Flavour Physics, Anacapri, Capri,
Italy, 29-31 May 2006, to appear in the Proceeding
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
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
Approximate Minimum Diameter
We study the minimum diameter problem for a set of inexact points. By
inexact, we mean that the precise location of the points is not known. Instead,
the location of each point is restricted to a contineus region (\impre model)
or a finite set of points (\indec model). Given a set of inexact points in
one of \impre or \indec models, we wish to provide a lower-bound on the
diameter of the real points.
In the first part of the paper, we focus on \indec model. We present an
time
approximation algorithm of factor for finding minimum diameter
of a set of points in dimensions. This improves the previously proposed
algorithms for this problem substantially.
Next, we consider the problem in \impre model. In -dimensional space, we
propose a polynomial time -approximation algorithm. In addition, for
, we define the notion of -separability and use our algorithm for
\indec model to obtain -approximation algorithm for a set of
-separable regions in time
Model Independent Bound on the Unitarity Triangle from CP Violation in B-> pi+ pi- and B-> psi K_S
We derive model independent lower bounds on the CKM parameters (1-rhobar) and
etabar as functions of the mixing-induced CP asymmetry S in B-> pi+ pi- and
sin(2 beta) from B->psi K_S. The bounds do not depend on specific results of
theoretical calculations for the penguin contribution to B-> pi+ pi-. They
require only the very conservative condition that a hadronic phase, which
vanishes in the heavy-quark limit, does not exceed 90 degrees in magnitude. The
bounds are effective if -sin(2 beta) < S < 1. Dynamical calculations indicate
that the limits on rhobar and etabar are close to their actual values.Comment: 5 pages, 2 figure
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