97 research outputs found
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
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.
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
Exploring the Unitarity Triangle through CP violation observables in
We discuss the determination of the CKM parameters from the forthcoming
violation observables in decays. Combining the information on
mixing induced CP violation in , with the
precision observable and the -- mixing phase
, we propose a determination of the unitarity triangle . Computing the penguin parameters within QCD
factorization yield precise determination of , reflected
by a weak dependence on the which is shown as a second order effect.
The impact of the direct CP violation observable on the penguin
parameters are investigated and a lower bound on is extracted. We also
discuss the effect of the -- new physics mixing phase on
the penguin parameters and . Using the SU(3)-flavour
symmetry argument and the current -factories data provided by the modes, we complement the CP-violating
observables in a variety of ways, in particular we find that .
Finally we analyze systematically the SU(3)-symmetry breaking factor within QCD
factorization.Comment: 22 pages, 6 figures, typos corrected, reference and some remarks
adde
In Pursuit of New Physics with B_s Decays
The presence of a sizeable CP-violating phase in B_s^0-B_s^0-bar mixing would
be an unambiguous signal of physics beyond the Standard Model. We analyse
various possibilities to detect such a new phase considering both tagged and
untagged decays. The effects of a sizeable width difference Delta Gamma between
the B_s mass eigenstates, on which the untagged analyses rely, are included in
all formulae. A novel method to find this phase from simple measurements of
lifetimes and branching ratios in untagged decays is proposed. This method does
not involve two-exponential fits, which require much larger statistics. For the
tagged decays, an outstanding role is played by the observables of the
time-dependent angular distribution of the B_s -> J/psi [-> l^+ l^-] \phi [->
K^+K^-] decay products. We list the formulae needed for the angular analysis in
the presence of both a new CP-violating phase and a sizeable Delta Gamma, and
propose methods to remove a remaining discrete ambiguity in the new phase. This
phase can therefore be determined in an unambiguous way.Comment: minor changes, lattice prediction of Delta Gamma updated, appears in
PR
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
: 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
Determination of the angle from nonleptonic decays
We note that the two body nonleptonic pure tree decays and the corresponding vector-vector modes are well suited to extract the weak phase
of the unitarity triangle. The CP violating phase can be determined
cleanly as these decay modes are free from the penguin pollutions.Comment: 12 pages, LaTeX, 2 references added, Minor changes in the text, to
appear in Phys. Rev.
Measurement of the Lifetime Difference of Mesons: Possible and Worthwhile?
We estimate the decay width difference in the
system including contributions and next-to-leading order QCD
corrections, and find it to be around 0.3%. We explicitly show that the time
measurements of an untagged decaying to a single final state
isotropically can only be sensitive to quadratic terms in , and hence the use of at least two different final states is desired.
We discuss such pairs of candidate decay channels for the final states and
explore the feasibility of a measurement through
them. The measurement of this width difference is essential for an accurate
measurement of at the LHC. The nonzero width difference may also
be used to identify new physics effects and to resolve a twofold discrete
ambiguity in the - mixing phase. We also derive an upper bound
on the value of in the presence of new physics, and
point out some differences in the phenomenology of width differences in the
and systems.Comment: latex, 31 pages, revised versio
Verification and Validation of a Three-Dimensional Composite Impact Model with Tabulated Input
A material model which incorporates several key capabilities which have been identified by the aerospace community as lacking in the composite impact models currently available in the commercial transient dynamic finite element code LS-DYNA has been developed. The material model utilizes experimentally based tabulated input to define the evolution of plasticity and damage as opposed to specifying discrete input parameters (such as modulus and strength. The plasticity portion of the orthotropic, three-dimensional, macroscopic composite constitutive model is based on an extension of the Tsai-Wu composite failure model into a generalized yield function with a non-associative flow rule. The capability to account for the rate and temperature dependent deformation response of composites has also been incorporated into the material model. For the damage model, a strain equivalent formulation is utilized to allow for the uncoupling of the deformation and damage analyses. In the damage model, a diagonal damage tensor is defined to account for the directionally dependent variation of damage. However, the terms in the damage matrix are semi-coupled such that the damage in a particular coordinate direction is a function of the stresses and plastic strains in all of the coordinate directions. For the failure model, a tabulated approach is utilized in which a stress or strain based invariant is defined as a function of the location of the current stress state in stress space to define the initiation of failure, which allows an arbitrarily shaped failure surface to be defined. A systematic series of validation and verification studies, at a variety of length scales ranging from single element simulations to simulations of a flat panel impact test, have been performed to fully exercise and evaluate the capabilities of the developed model
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