3,993 research outputs found
Exploring CP Violation through Correlations in B --> pi K, B_d --> pi^+pi^-, B_s --> K^+K^- Observable Space
We investigate allowed regions in observable space of B --> pi K, B_d -->
pi^+pi^- and B_s --> K^+K^- decays, characterizing these modes in the Standard
Model. After a discussion of a new kind of contour plots for the
system, we focus on the mixing- induced and direct CP asymmetries of the decays
B_d --> pi^+pi^- and B_s--> K^+K^-. Using experimental information on the
CP-averaged B_d --> pi^{+/-}K^{+/-} and B_d --> pi^+pi^- branching ratios, the
relevant hadronic penguin parameters can be constrained,implying certain
allowed regions in observable space. In the case of B_d --> pi^+pi^-, an
interesting situation arises now in view of the recent B-factory measurements
of CP violation in this channel, allowing us to obtain new constraints on the
CKM angle gamma as a function of the B^0_d--\bar{B^0_d} mixing phase
phi_d=2beta, which is fixed through A_{CP}^{mix}(B_d --> J/psi K_S) up to a
twofold ambiguity. If we assume that A_{CP}^{mix}(B_d --> pi^+pi^-) is
positive, as indicated by recent Belle data, and that phi_d is in agreement
with the ``indirect'' fits of the unitarity triangle, also the corresponding
values for gamma around 60 degrees can be accommodated. On the other hand, for
the second solution of phi_d, we obtain a gap around gamma ~ 60 degrees. The
allowed region in the space of A_{CP}^{mix}(B_s --> K^+K^-) and
A_{CP}^{dir}(B_s --> K^+K^-) is very constrained in the Standard Model, thereby
providing a narrow target range for run II of the Tevatron and the experiments
of the LHC era.Comment: 34 pages, LaTeX, 12 figures. More detailed introduction and a few
Comments added, conclusions unchanged. To appear in Phys. Rev.
Weak Phase From Ratio of Rates
The ratio of partial decay rates for charged and neutral mesons to final states provides information on the weak phase when augmented with information on the CP-violating asymmetry
in the mode. The requirements for a useful determination of
are examined in the light of present information about the decays , , and the corresponding charge-conjugate
modes. The effects of electroweak penguins and rescattering corrections are
noted, and proposals are made for estimating and measuring their importance.Comment: 16 pages, latex, 3 figures, revised version sent to Phys. Rev.
Exploring CP Violation with Decays
We point out that the pure ``tree'' decays are
particularly well suited to extract the CKM angle through amplitude
relations. In contrast to conceptually similar strategies using or decays, the advantage of the approach is that
the corresponding triangles have three sides of comparable length and do not
involve small amplitudes. Decays of the type -- the
-spin counterparts of -- can be added to the
analysis, as well as channels, where the - and -mesons are
replaced by higher resonances.Comment: 9 pages, LaTeX, 3 figures, reference adde
A Possibility of large electro-weak penguin contribution in B -> K pi modes
We discuss about a possibility of large electro-weak penguin contribution in
B -> K pi from recent experimental data. The several relations among the
branching ratios which realize when the contributions from tree type and
electro-weak penguin are small compared with the gluon penguin and can be
treated as the expansion parameters do not satisfy the data. The difference
comes from the r^2 terms which is the square of the ratio with the gluon
penguin and the main contribution comes from electro-weak penguin. We find that
the contribution from electro-weak penguin may be large to explain the
experimental data. If the magnitude estimated from experiment is quite large
compared with the theoretical estimation, then it may be including some new
physics effects.Comment: 11 pages, 1 figure, Typos correcte
Rescattering Information from Decays
Rescattering effects can modify the dependence on the weak phase of the ratio of rates for and . A test for these effects based on the
processes has been suggested. It is pointed out that the
rates for the processes , which are expected to be {\it
dominated} by rescattering and for which considerably better experimental
bounds exist, are likely to provide a more stringent constraint on these
effects.Comment: 22 pages, latex, 7 figures, to be published in Phys. Rev. D. Minor
corrections and addition
Strong and Weak Phases from Time-Dependent Measurements of
Time-dependence in and \ob(t) \to \pi^+ \pi^- is
utilized to obtain a maximal set of information on strong and weak phases. One
can thereby check theoretical predictions of a small strong phase
between penguin and tree amplitudes. A discrete ambiguity between and may be resolved by comparing the observed
charge-averaged branching ratio predicted for the tree amplitude alone, using
measurements of and factorization, or by direct comparison of
parameters of the Cabibbo-Kobayashi-Maskawa (CKM) matrix with those determined
by other means. It is found that with 150 fb from BaBar and Belle, this
ambiguity will be resolvable if no direct CP violation is found. In the
presence of direct CP violation, the discrete ambiguity between and
becomes less important, vanishing altogether as . The role of measurements involving the lifetime difference between
neutral eigenstates is mentioned briefly.Comment: 14 pages, LaTeX, 5 figures, to be published in Phys. Rev. D. Updated
version with one reference change
Combining CP Asymmetries in Decays
We prove an approximate relation, to leading order in dominant terms, between
CP-violating rate differences in and
. We show how data from these two processes may be
combined in order to enhance the significance of a nonzero result.Comment: 9 pages, latex, no figures, submitted to Phys. Rev. Letters, revise
: Status and Prospects
Several years ago, it was pointed out that the U-spin-related decays
, and , offer interesting strategies for the extraction of the angle gamma of
the unitarity triangle. Using the first results from the Tevatron on the
decays and the B-factory data on modes, we compare the determinations
of gamma from both strategies, study the sensitivity on U-spin-breaking
effects, discuss the resolution of discrete ambiguities, predict observables
that were not yet measured but will be accessible at LHCb, explore the
extraction of the width difference from untagged rates, and address the impact of new physics. The data for the
, system favour the BaBar measurement of
direct CP violation in , which will be used in the numerical
analysis, and result in a fortunate situation, yielding
, where the latter errors correspond
to a generous estimate of U-spin-breaking effects. On the other hand, the
, analysis leaves us with
, and points to a value of the branching ratio that is larger than the current Tevatron result. An
important further step will be the measurement of mixing-induced CP violation
in , which will also allow us to extract the -- mixing phase unambiguously with the help of at the
LHC. Finally, the measurement of direct CP violation in will
make the full exploitation of the physics potential of the modes possible.Comment: 28 pages, 10 figure
Vibration analysis of moving machine tool axes based on phase information in video data
Vibrations of machine tools limit quality and productivity and therefore need to be analyzed. Video based vibration analysis using spatial phase information could in principle reduce measuring effort significantly. However, feasibility of these approaches for moving machine tool axes and relative movement between camera and object is yet to be shown. This paper investigates an approach for stabilizing linear axis movement to analyze vibration. It is shown that shaker induced vibration on a linearly moving clamping tower can be derived for low frequencies. However, influences of actual cutting processes as well as compensation of unwanted camera vibration needs further investigation
A Critical Study of B Decays to Light Pseudoscalar
Motivated by the large branching ratios observed for the process
, we examine critically all the ingredients that go into
estimates of B decays into two light pseudoscalars. Within factorization
approximation, we examine several assumptions on the input parameters that
could have a strong bearing on the predictions. Among these are (i) the QCD
scale (ii) value of the form factors (iii) value of the light quark
masses, and in particular (iv) the value , (v) charm content
of . It is possible to account for all the data without invoking
new physics, though future experiments will provide tighter constraints on the
parameter space. We fin that CP violating asymmetries are in the observable
range for some modes.Comment: 29 pages(Latex), 17 figures, a few changes have been made, version to
appear in Phys.Rev.
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