3,646 research outputs found
On Branching Ratios of Decays and the Search for New Physics in
The LHCb experiment has recently established a sizable width difference
between the mass eigenstates of the -meson system. This phenomenon leads
to a subtle difference at the 10% level between the experimental branching
ratios of decays extracted from time-integrated, untagged data samples
and their theoretical counterparts. Measuring the corresponding effective
-decay lifetimes, both branching ratio concepts can be converted into each
other. The rare decay and the search for New Physics
through this channel is also affected by this effect, which enhances the
Standard-Model reference value of the branching ratio by O(10%), while the
effective lifetime offers a new observable to search for physics beyond the
Standard Model that is complementary to the branching ratio.Comment: 6 pages, invited talk at the 4th Workshop on Theory, Phenomenology
and Experiments in Heavy Flavour Physics, Capri, Italy, 11-13 June 2012, to
appear in the Proceeding
The influence of negative-energy states on proton-proton bremsstrahlung
We investigate the effect of negative-energy states on proton-proton
bremsstrahlung using a manifestly covariant amplitude based on a T-matrix
constructed in a spectator model. We show that there is a large cancellation
among the zeroth-order, single- and double-scattering diagrams involving
negative-energy nucleonic currents. We thus conclude that it is essential to
include all these diagrams when studying effects of negative-energy states.Comment: 12 pages revtex and 3 figure
Exploring Decays in the Presence of a Sizable Width Difference
The decays allow a theoretically clean
determination of , where is the -
mixing phase and the usual angle of the unitarity triangle. A sizable
decay width difference was recently established, which
leads to subtleties in analyses of the branching
ratios but also offers new "untagged" observables, which do not require a
distinction between initially present or mesons. We
clarify these effects and address recent measurements of the ratio of the
, branching ratios. In
anticipation of future LHCb analyses, we apply the SU(3) flavour symmetry of
strong interactions to convert the -factory data for , decays into predictions of the
observables, and discuss strategies for the
extraction of , with a special focus on untagged observables and
the resolution of discrete ambiguities. Using our theoretical predictions as a
guideline, we make simulations to estimate experimental sensitivities, and
extrapolate to the end of the planned LHCb upgrade. We find that the interplay
between the untagged observables, which are accessible thanks to the sizable
, and the mixing-induced CP asymmetries, which require tagging,
will play the key role for the experimental determination of .Comment: 21 pages, 7 figures, matches published versio
A Roadmap to Control Penguin Effects in and
Measurements of CP violation in and decays play key roles in testing the quark-flavour sector of the
Standard Model. The theoretical interpretation of the corresponding observables
is limited by uncertainties from doubly Cabibbo-suppressed penguin topologies.
With continuously increasing experimental precision, it is mandatory to get a
handle on these contributions, which cannot be calculated reliably in QCD. In
the case of the measurement of from ,
the -spin-related decay offers a tool to
control the penguin effects. As the required measurements are not yet
available, we use data for decays with similar dynamics and the flavour
symmetry to constrain the size of the expected penguin corrections. We predict
the CP asymmetries of and present a scenario to
fully exploit the physics potential of this decay, emphasising also the
determination of hadronic parameters and their comparison with theory. In the
case of the benchmark mode used to determine the
- mixing phase the penguin effects can be
controlled through and
decays. The LHCb collaboration has recently presented pioneering results on
this topic. We analyse their implications and present a roadmap for controlling
the penguin effects.Comment: 34 pages, 16 figures, matching published versio
Vortex solitons in photonic crystal fibers
We demonstrate the existence of vortex soliton solutions in photonic crystal
fibers. We analyze the role played by the photonic crystal fiber defect in the
generation of optical vortices. An analytical prediction for the angular
dependence of the amplitude and phase of the vortex solution based on group
theory is also provided. Furthermore, all the analysis is performed in the
non-paraxial regime.Comment: 4 pages, 4 figure
Extracting gamma and Penguin Topologies through CP Violation in B_s^0 -> J/psi K_S
The B_s^0 -> J/psi K_S decay has recently been observed by the CDF
collaboration and will be of interest for the LHCb experiment. This channel
will offer a new tool to extract the angle gamma of the unitarity triangle and
to control doubly Cabibbo-suppressed penguin corrections to the determination
of sin(2beta) from the well-known B_d^0 -> J/psi K_S mode with the help of the
U-spin symmetry of strong interactions. While any competitive determination of
gamma is interesting, the latter aspect is particularly relevant as LHCb will
enter a territory of precision which makes the control of doubly
Cabibbo-suppressed Standard-Model corrections mandatory. Using the data from
CDF and the e^+e^- B factories as a guideline, we explore the sensitivity for
gamma and the penguin parameters and point out that the B_s^0-\bar B_s^0 mixing
phase phi_s, which is only about -2 deg in the Standard Model but may be
enhanced through new physics, is a key parameter for these analyses. We find
that the mixing-induced CP violation S(B_s^0 -> J/psi K_S) shows an interesting
correlation with sin(phi_s), which serves as a target region for the first
measurement of this observable at LHCb.Comment: 20 pages, 8 figure
Trilinear Gauge Boson Couplings in the MSSM
We study the C and P even WW\gamma and WWZ trilinear gauge boson vertices
(TGV's), in the context of the MSSM assuming that the external W's are on their
mass shell. We find that for energies less than 200 GeV squark and slepton
contributions to the aforementioned couplings are two orders of magnitude
smaller than those of the Standard Model (SM). In the same energy range the
bulk of the supersymmetric Higgs corrections to the TGV's is due to the
lightest neutral Higgs, h_0, whose contribution is like that of a Standard
Model Higgs of the same mass. The contributions of the Neutralinos and
Charginos are sensitive to the input value for the soft gaugino mass M_{1/2},
being more pronounced for values M_{1/2} < 100 GeV. In this case and in the
unphysical region, 0 < \sqrt{s} < 2 M_W , their contributions are substantially
enhanced resulting in large corrections to the static quantities of the W
boson. However, such an enhancement is not observed in the physical region. In
general for 2 M_W < \sqrt{s} < 200 GeV the MSSM predictions differ from those
of the SM but they are of the same order of magnitude. To be detectable
deviations from the SM require sensitivities reaching the per mille level and
hence unlikely to be observed at LEP200. For higher energies SM and MSSM
predictions exhibit a fast fall off behaviour, in accord with unitarity
requirements, getting smaller,in most cases, by almost an order of magnitude
already at energies \sqrt{s} 0.5 TeV.Comment: 16 pages, late
Towards new frontiers in the exploration of charmless non-leptonic B decays
Non-leptonic decays into charmless final states offer an important
laboratory to study CP violation and the dynamics of strong interactions.
Particularly interesting are and decays,
which are related by the -spin symmetry of strong interactions, and allow
for the extraction of CP-violating phases and tests of the Standard Model. The
theoretical precision is limited by -spin-breaking corrections and
innovative methods are needed in view of the impressive future experimental
precision expected in the era of Belle II and the LHCb upgrade. We have
recently proposed a novel method to determine the - mixing
phase from the , system, where
semileptonic ,
decays are a new ingredient and the theoretical situation is very favourable.
We discuss this strategy in detail, with a focus on penguin contributions as
well as exchange and penguin-annihilation topologies which can be probed by a
variety of non-leptonic decays into charmless final states. We show that a
theoretical precision as high as for can be
attained in the future, thereby offering unprecedented prospects for the search
for new sources of CP violation.Comment: 50 pages, 25 figure
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