1,480 research outputs found
Strong Phases and Factorization for Color Suppressed Decays
We prove a factorization theorem in QCD for the color suppressed decays B0->
D0 M0 and B0-> D*0 M0 where M is a light meson. Both the color-suppressed and
W-exchange/annihilation amplitudes contribute at lowest order in LambdaQCD/Q
where Q={mb, mc, Epi}, so no power suppression of annihilation contributions is
found. A new mechanism is given for generating non-perturbative strong phases
in the factorization framework. Model independent predictions that follow from
our results include the equality of the B0 -> D0 M0 and B0 -> D*0 M0 rates, and
equality of non-perturbative strong phases between isospin amplitudes,
delta(DM) = delta(D*M). Relations between amplitudes and phases for M=pi,rho
are also derived. These results do not follow from large Nc factorization with
heavy quark symmetry.Comment: 38 pages, 6 figs, typos correcte
Low Mach number effect in simulation of high Mach number flow
In this note, we relate the two well-known difficulties of Godunov schemes:
the carbuncle phenomena in simulating high Mach number flow, and the inaccurate
pressure profile in simulating low Mach number flow. We introduced two simple
low-Mach-number modifications for the classical Roe flux to decrease the
difference between the acoustic and advection contributions of the numerical
dissipation. While the first modification increases the local numerical
dissipation, the second decreases it. The numerical tests on the double-Mach
reflection problem show that both modifications eliminate the kinked Mach stem
suffered by the original flux. These results suggest that, other than
insufficient numerical dissipation near the shock front, the carbuncle
phenomena is strongly relevant to the non-comparable acoustic and advection
contributions of the numerical dissipation produced by Godunov schemes due to
the low Mach number effect.Comment: 9 pages, 1 figur
Nonfactorizable contributions to decays
While the factorization assumption works well for many two-body nonleptonic
meson decay modes, the recent measurement of with
, and shows large deviation from this assumption. We
analyze the decays in the perturbative QCD approach based on
factorization theorem, in which both factorizable and nonfactorizable
contributions can be calculated in the same framework. Our predictions for the
Bauer-Stech-Wirbel parameters, and and and , are
consistent with the observed and branching ratios,
respectively. It is found that the large magnitude and the large
relative phase between and come from color-suppressed
nonfactorizable amplitudes. Our predictions for the , branching ratios can be confronted with
future experimental data.Comment: 25 pages with Latex, axodraw.sty, 6 figures and 5 tables, Version
published in PRD, Added new section 5 and reference
Information-Based Hierarchical Planning for a Mobile Sensing Network in Environmental Mapping
This article investigates the problem of information-based sampling design and path planning for a mobile sensing network to predict scalar fields of monitored environments. A hierarchical framework with a built-in Gaussian Markov random field model is proposed to provide adaptive sampling for efficient field reconstruction. In the proposed framework, a nonmyopic planner is operated at a sink to navigate the mobile sensing agents in the field to the sites that are most informative. Meanwhile, a myopic planner is carried out on board each agent. A tradeoff between computationally intensive global optimization and efficient local greedy search is incorporated into the system. The mobile sensing agents can be scheduled online through an anytime algorithm to visit and observe the high-information sites. Experiments on both synthetic and real-world datasets are used to demonstrate the feasibility and efficiency of the proposed planner in model exploitation and adaptive sampling for environmental field mapping
The quantum cryptographic switch
We illustrate using a quantum system the principle of a cryptographic switch,
in which a third party (Charlie) can control to a continuously varying degree
the amount of information the receiver (Bob) receives, after the sender (Alice)
has sent her information. Suppose Charlie transmits a Bell state to Alice and
Bob. Alice uses dense coding to transmit two bits to Bob. Only if the 2-bit
information corresponding to choice of Bell state is made available by Charlie
to Bob can the latter recover Alice's information. By varying the information
he gives, Charlie can continuously vary the information recovered by Bob. The
performance of the protocol subjected to the squeezed generalized amplitude
damping channel is considered. We also present a number of practical situations
where a cryptographic switch would be of use.Comment: 7 pages, 4 Figure
Parametrization of projector-based witnesses for bipartite systems
Entanglement witnesses are nonpositive Hermitian operators which can detect
the presence of entanglement. In this paper, we provide a general
parametrization for orthonormal basis of and use it to
construct projector-based witness operators for entanglement detection in the
vicinity of pure bipartite states. Our method to parameterize entanglement
witnesses is operationally simple and could be used for doing symbolic and
numerical calculations. As an example we use the method for detecting
entanglement between an atom and the single mode of quantized field, described
by the Jaynes-Cummings model. We also compare the detection of witnesses with
the negativity of the state, and show that in the vicinity of pure stats such
constructed witnesses able to detect entanglement of the state.Comment: 12 pages, four figure
Heavy-to-light transition form factors and their relations in light-cone QCD sum rules
The improved light-cone QCD sum rules by using chiral current correlator is
systematically reviewed and applied to the calculation of all the
heavy-to-light form factors, including all the semileptonic and penguin ones.
By choosing suitable chiral currents, the light-cone sum rules for all the form
factors are greatly simplified and depend mainly on one leading twist
distribution amplitude of the light meson. As a result, relations between these
form factors arise naturally. At the considered accuracy these relations
reproduce the results obtained in the literature. Moreover, since the explicit
dependence on the leading twist distribution amplitudes is preserved, these
relations may be more useful to simulate the experimental data and extract the
information on the distribution amplitude.Comment: 1+16 pages, no figure
Quantum-noise-induced macroscopic revivals in second-harmonic generation
We investigate the behavior of the fundamental and second-harmonic fields in phase-matched traveling plane-wave second-harmonic generation, using the full-operator equations of motion. We find that, after a certain interaction length, both the macroscopic and quantum-statistical properties of the harmonic and fundamental fields are qualitatively different from those found in previous analyses. The mean fields do not vary in a monotonic way, but oscillate with the propagation length, leading to an unexpected periodic revival of the fundamental field, triggered by the quantum fluctuations always present in the mode. Accordingly, the amplitude noise of the fundamental, previously predicted to be perfectly squeezed for long interaction lengths, actually reaches a very small minimum for a definite length, then increases again
General Stability Analysis of Synchronized Dynamics in Coupled Systems
We consider the stability of synchronized states (including equilibrium
point, periodic orbit or chaotic attractor) in arbitrarily coupled dynamical
systems (maps or ordinary differential equations). We develop a general
approach, based on the master stability function and Gershgorin disc theory, to
yield constraints on the coupling strengths to ensure the stability of
synchronized dynamics. Systems with specific coupling schemes are used as
examples to illustrate our general method.Comment: 8 pages, 1 figur
Hadronic Charmed Meson Decays Involving Tensor Mesons
Charmed meson decays into a pseudoscalar meson P and a tensor meson T are
studied. The charm to tensor meson transition form factors are evaluated in the
Isgur-Scora-Grinstein-Wise (ISGW) quark model. It is shown that the
Cabibbo-allowed decay is dominated by the
W-annihilation contribution and has the largest branching ratio in
decays. We argue that the Cabibbo-suppressed mode
should be suppressed by one order of magnitude relative to . When the finite width effect of the tensor resonances is taken
into account, the decay rate of is generally enhanced by a factor of
. Except for , the predicted branching ratios
of decays are in general too small by one to two orders of magnitude
compared to experiment. However, it is very unlikely that the
transition form factors can be enhanced by a factor of within the
ISGW quark model to account for the discrepancy between theory and experiment.
As many of the current data are still preliminary and lack sufficient statistic
significance, more accurate measurements are needed to pin down the issue.Comment: 11 page
- …