4,692 research outputs found
Direct CP violation in two-body hadronic charmed meson decays
Motivated by the recent observation of CP violation in the charm sector by
LHCb, we study direct CP asymmetries in the standard model (SM) for the singly
Cabibbo-suppressed two-body hadronic decays of charmed mesons using the
topological-diagram approach. In this approach, the magnitude and the phase of
topological weak annihilation amplitudes which arise mainly from final-state
rescattering can be extracted from the data. Consequently, direct CP asymmetry
at tree level can be reliably estimated. In general, it
lies in the range . Short-distance QCD
penguins and penguin annihilation are calculated using QCD factorization. Their
effects are generally small, especially for modes. Since weak penguin
annihilation receives long-distance contributions from the color-allowed tree
amplitude followed by final-state rescattering, it is expected to give the
dominant contribution to the direct CP violation in the decays
and in which is absent. The maximal
, the direct CP asymmetry difference between the
above-mentioned two modes, allowed in the SM is around -0.25%, more than
away from the current world average of .Comment: 19 pages, 2 figures; typos correcte
Exclusive Hadronic D Decays to eta' and eta
Hadronic decay modes and
are studied in the generalized
factorization approach. Form factors for transitions
are carefully evaluated by taking into account the wave function normalization
of the eta and eta'. The predicted branching ratios are generally in agreement
with experiment except for and
; the calculated decay rates for the first two decay modes
are too small by an order of magnitude. We show that the weak decays and followed by resonance-induced final-state
interactions (FSI), which are amenable technically, are able to enhance the
branching ratios of and dramatically
without affecting the agreement between theory and experiment for and . We argue that it is difficult to understand
the observed large decay rates of and
simultaneously; FSI, W-annihilation and the production of excess eta' from
gluons are not helpful in this regard. The large discrepancy between the
factorization hypothesis and experiment for the ratio of
and remains as an enigma.Comment: 15 pages, 1 figure, to appear in Phys. Rev. D. Form factors for D to
eta and eta' transitions are slightly change
Relation Between Quantum Speed Limits And Metrics On U(n)
Recently, Chau [Quant. Inform. & Comp. 11, 721 (2011)] found a family of
metrics and pseudo-metrics on -dimensional unitary operators that can be
interpreted as the minimum resources (given by certain tight quantum speed
limit bounds) needed to transform one unitary operator to another. This result
is closely related to the weighted -norm on . Here we
generalize this finding by showing that every weighted -norm on
with 1\le p \le \limitingp induces a metric and a
pseudo-metric on -dimensional unitary operators with quantum
information-theoretic meanings related to certain tight quantum speed limit
bounds. Besides, we investigate how far the correspondence between the
existence of metrics and pseudo-metrics of this type and the quantum speed
limits can go.Comment: minor amendments, 6 pages, to appear in J.Phys.
Factorial Moments in a Generalized Lattice Gas Model
We construct a simple multicomponent lattice gas model in one dimension in
which each site can either be empty or occupied by at most one particle of any
one of species. Particles interact with a nearest neighbor interaction
which depends on the species involved. This model is capable of reproducing the
relations between factorial moments observed in high--energy scattering
experiments for moderate values of . The factorial moments of the negative
binomial distribution can be obtained exactly in the limit as becomes
large, and two suitable prescriptions involving randomly drawn nearest neighbor
interactions are given. These results indicate the need for considerable care
in any attempt to extract information regarding possible critical phenomena
from empirical factorial moments.Comment: 15 pages + 1 figure (appended as postscript file), REVTEX 3.0,
NORDITA preprint 93/4
Good Quantum Convolutional Error Correction Codes And Their Decoding Algorithm Exist
Quantum convolutional code was introduced recently as an alternative way to
protect vital quantum information. To complete the analysis of quantum
convolutional code, I report a way to decode certain quantum convolutional
codes based on the classical Viterbi decoding algorithm. This decoding
algorithm is optimal for a memoryless channel. I also report three simple
criteria to test if decoding errors in a quantum convolutional code will
terminate after a finite number of decoding steps whenever the Hilbert space
dimension of each quantum register is a prime power. Finally, I show that
certain quantum convolutional codes are in fact stabilizer codes. And hence,
these quantum stabilizer convolutional codes have fault-tolerant
implementations.Comment: Minor changes, to appear in PR
Implications of Recent Measurements
The recent measurements of the color-suppressed modes imply non-vanishing relative final-state interaction (FSI)
phases among various decay amplitudes. Depending on whether or
not FSIs are implemented in the topological quark-diagram amplitudes, two
solutions for the parameters and are extracted from data using
various form-factor models. It is found that is not universal:
and with a relative phase
of order between and . If FSIs are not included in
quark-diagram amplitudes from the outset, and
will become smaller. The large value of compared to
or naive expectation implies the importance of
long-distance FSI contributions to color-suppressed internal -emission via
final-state rescatterings of the color-allowed tree amplitude.Comment: 17 pages. The Introduction is substantially revised and the order of
the presentation in Sec. 2 is rearranged. To appear in Phys. Re
Cabibbo-allowed nonleptonic weak decays of charmed baryons
Cabibbo-allowed nonleptonic weak decays of charmed baryons
\lamc,~\xin,~\xip and into an octet baryon and a pseudoscalar
meson are analyzed. The nonfactorizable contributions are evaluated under pole
approximation, and it turns out that the -wave amplitudes are dominated by
the low-lying \halfm resonances, while -wave ones governed by the
ground-state \halfp poles. The MIT bag model is employed to calculate the
coupling constants, form factors and baryon matrix elements. Our conclusions
are: (i) waves are no longer dominated by commutator terms; the
current-algebra method is certainly not applicable to parity-violating
amplitudes, (ii) nonfactorizable exchange effects are generally important;
they can be comparable to and somtimes even dominate over factorizable
contributions, depending on the decay modes under consideration, (iii)
large- approximation for factorizable amplitudes also works in the heavy
baryon sector and it accounts for the color nonsuppression of \lamc\ri
p\bar{K}^0 relative to \lamc\ri\Lambda\pi^+, (iv) a measurement of the decay
rate and the sign of the asymmetry parameter of certain proposed decay
modes will help discern various models; especially the sign of in
\lamc\ri\Sigma\pi decays can be used to unambiguously differentiate recent
theoretical schemes from current algebra, and (v) waves are the dominant
contributions to the decays \lamc\ri\Xi^0 K^+ and \xin\ri\Sigma^+ K^-, but
they are subject to a large cancellation; this renders present theoretical
predictions on these two channels unreliable.Comment: PHYZZX, 31 pages, 3 tables, IP-ASTP-10-93, ITP-SB-93-2
Wolfenstein Parametrization Re-examined
The Wolfenstein parametrization of the Kobayashi-Maskawa (KM)
matrix is modified by keeping its unitarity up to the accuracy of
. This modification can self-consistently lead to the
off-diagonal asymmetry of : =
with , which is comparable in magnitude with the Jarlskog parameter of
violation . We constrain the ranges of
and by using the current experimental data, and point out that the
possibility of a symmetric KM matrix has almost been ruled out.Comment: 5 Latex pages including a figure; Two references are adde
Relation between CKM and MNS Matrices Induced by Bi-Maximal Rotations in the Seesaw Mechanism
It is found that the seesaw mechanism not only explains the smallness of
neutrino masses but also accounts for the large mixing angles simultaneously,
even if the unification of the neutrino Dirac mass matrix with that of up-type
quark sector is realized. In this mechanism, we show that the mixing matrix of
the Dirac-type mass matrix gets extra rotations from the diagonalization of
Majorana mass matrix. Assuming that the mixing angles to diagonalize the
Majorana mass matrix are extremely small, we find that the large mixing angles
of leptonic sector found in atmospheric and long baseline reactor neutrino
oscillation experiments can be explained by these extra rotations. We also find
that provided the mixing angle around y-axis to diagonalize the Majorana mass
matrix vanishes, we can derive the information about the absolute values of
neutrino masses and Majorana mass responsible for the neutrinoless double beta
decay experiment through the data set of neutrino experiments. In the
simplified case that there is no CP phase, we find that the neutrino masses are
decided as and that there are no solution which
satisfy (inverted mass spectrum). Then, including all CP phases,
we reanalyze the absolute values of neutrino masses and Majorana mass
responsible for the neutrinoless double beta decay experiment.Comment: 19 pages, 7 figures, revtex4, to appear in J.PHYS.SOC.JA
Branching Ratio and CP Violation of B to pi pi Decays in Perturbative QCD Approach
We calculate the branching ratios and CP asymmetries for B^0 to pi^+pi^-, B^+
to pi^+pi^0 and B^0 to pi^0pi^0 decays, in a perturbative QCD approach. In this
approach, we calculate non-factorizable and annihilation type contributions, in
addition to the usual factorizable contributions. We found that the
annihilation diagram contributions are not very small as previous argument. Our
result is in agreement with the measured branching ratio of B to pi^+pi^- by
CLEO collaboration. With a non-negligible contribution from annihilation
diagrams and a large strong phase, we predict a large direct CP asymmetry in
B^0 to pi^+pi^-, and pi^0pi^0, which can be tested by the current running B
factories.Comment: Latex, 28 pages including 11 figures; added contents and figures,
corrected typo
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