5,079 research outputs found
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
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
Controlling Molecular Scattering by Laser-Induced Field-Free Alignment
We consider deflection of polarizable molecules by inhomogeneous optical
fields, and analyze the role of molecular orientation and rotation in the
scattering process. It is shown that molecular rotation induces spectacular
rainbow-like features in the distribution of the scattering angle. Moreover, by
preshaping molecular angular distribution with the help of short and strong
femtosecond laser pulses, one may efficiently control the scattering process,
manipulate the average deflection angle and its distribution, and reduce
substantially the angular dispersion of the deflected molecules. We provide
quantum and classical treatment of the deflection process. The effects of
strong deflecting field on the scattering of rotating molecules are considered
by the means of the adiabatic invariants formalism. This new control scheme
opens new ways for many applications involving molecular focusing, guiding and
trapping by optical and static fields
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
General Lower Bounds for b -> d Penguin Processes
For the exploration of flavour physics, b -> d penguin processes are an
important aspect, with the prominent example of \bar B^0_d -> K^0 \bar K^0. We
recently derived lower bounds for the CP-averaged branching ratio of this
channel in the Standard Model; they were found to be very close to the
corresponding experimental upper limits, thereby suggesting that \bar B^0_d ->
K^0 \bar K^0 should soon be observed. In fact, the BaBar collaboration
subsequently announced the first signals of this transition. Here we point out
that it is also possible to derive lower bounds for \bar B -> \rho \gamma
decays, which are again surprisingly close to the current experimental upper
limits. We show that these bounds are realizations of a general bound that
holds within the Standard Model for b -> d penguin processes, allowing further
applications to decays of the kind B^\pm -> K^{(\ast)\pm} K^{(\ast)} and B^\pm
-> \pi^\pm \ell^+ \ell^-, \rho^\pm \ell^+ \ell^-.Comment: Minor changes, to appear as rapid communication in Phys. Rev
Non-factorizable contributions to
It is pointed out that decays of the type have no
factorizable contributions, unless at least one of the charmed mesons in the
final state is a vector meson. The dominant contributions to the decay
amplitudes arise from chiral loop contributions and tree level amplitudes
generated by soft gluon emissions forming a gluon condensate. We predict that
the branching ratios for the processes ,
and are all of
order , while has a
branching ratio 5 to 10 times bigger. We emphasize that the branching ratios
are sensitive to corrections.Comment: 4 pages, 4 figures. Based on talk by J.O. Eeg at BEACH 2004, 6th
international conference on Hyperons, Charm and Beauty Hadrons, Illionois
Institute of Technology, Chicago, june. 27 - july 3, 200
Using B_s^0 Decays to Determine the CP Angles \alpha and \gamma
Dighe, Gronau and Rosner have shown that, by assuming SU(3) flavor symmetry
and first-order SU(3) breaking, it is possible to extract the CP angles \alpha
and \gamma from measurements of the decay rates of B_d^0(t) --> \pi^+\pi^-,
B_d^0 --> \pi^- K^+ and B^+ --> \pi^+ K^0, along with their charge-conjugate
processes. We extend their analysis to include the SU(3)-related decays B_s^0
--> \pi^+ K^-, B_s^0(t) --> K^+ K^- and B_s^0 --> K^0 {\bar K^0}. There are
several advantages to this extension: discrete ambiguities are removed, fewer
assumptions are necessary, and the method works even if all strong phases
vanish. In addition, we show that \gamma can be obtained cleanly, with no
penguin contamination, by using the two decays B_s^0(t) --> K^+ K^- and B_s^0
--> K^0 {\bar K^0}.Comment: 28 pages, LaTe
Jet-like tunneling from a trapped vortex
We analyze the tunneling of vortex states from elliptically shaped traps.
Using the hydrodynamic representation of the Gross-Pitaevskii (Nonlinear
Schr\"odinger) equation, we derive analytically and demonstrate numerically a
novel type of quantum fluid flow: a jet-like singularity formed by the
interaction between the vortex and the nonhomogenous field. For strongly
elongated traps, the ellipticity overwhelms the circular rotation, resulting in
the ejection of field in narrow, well-defined directions. These jets can also
be understood as a formation of caustics since they correspond to a convergence
of trajectories starting from the top of the potential barrier and meeting at a
certain point on the exit line. They will appear in any coherent wave system
with angular momentum and non-circular symmetry, such as superfluids,
Bose-Einstein condensates, and light.Comment: 4 pages, 4 figure
Project {\tt SANC} (former {\tt CalcPHEP}): Support of Analytic and Numeric calculations for experiments at Colliders
The project, aimed at the theoretical support of experiments at modern and
future accelerators -- TEVATRON, LHC, electron Linear Colliders (TESLA, NLC,
CLIC) and muon factories, is presented. Within this project a four-level
computer system is being created, which must automatically calculate, at the
one-loop precision level the pseudo- and realistic observables (decay rates and
event distributions) for more and more complicated processes of elementary
particle interaction, using the principle of knowledge storing.
It was already used for a recalculation of the EW radiative corrections for
Atomic Parity Violation [1] and complete one-loop corrections for the process
[2-4]; for the latter an, agreement up to 11 digits with
FeynArts and the other results is found. The version of {\tt SANC} that we
describe here is capable of automatically computing the decay rates and the
distributions for the decays in the one-loop
approximation.Comment: 3 Latex, Presented at ICHEP2002, Amsterdam, July 24-30, 2000;
Submitted to Proceeding
Soliton control in modulated optically-induced photonic lattices
We discuss soliton control in reconfigurable optically-induced photonic
lattices created by three interfering beams. We reveal novel dynamical regimes
for strongly localized solitons, including binary switching and soliton
revivals through resonant wave mixing.Comment: 7 pages, 5 figures. Content modifie
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