30 research outputs found
CP Violation in B -> pi K Decays
I briefly review CP violation in the B system, concentrating on B -> pi K
decays. I discuss how to deal with electroweak-penguin contributions to these
decays using flavour SU(3). With these, I show that the entire unitarity
triangle can be extracted from measurements of B -> pi K decays. Finally, I
examine the signals for new physics in these decays and the possibilities for
measuring them.Comment: 8 pages, no figure, plain latex, To be published in the proceedings
of MRST 2004: From Quarks to Cosmology, Concordia University, Montreal, May
2004, references adde
Diagrammatic Analysis of Charmless Three-Body B Decays
We express the amplitudes for charmless three-body B decays in terms of
diagrams. In addition, we show how to use Dalitz-plot analyses to obtain decay
amplitudes which are symmetric or antisymmetric under the exchange of two of
the final-state particles. When annihilation-type diagrams are neglected, as in
two-body decays, many of the exact, purely isospin-based results are modified,
leading to new tests of the standard model (SM). Some of the tests can be
performed now, and we find that present data agree with the predictions of the
SM. Furthermore, contrary to what was thought previously, it is possible to
cleanly extract weak-phase information from three-body decays, and we discuss
methods for B -> K pi pi, K K Kbar, K Kbar pi and pi pi pi.Comment: 30 pages, 10 figures, reference updated, sentences added regarding
indirect CP violation and CP of the final state. Significant text added
describing how to obtain symmetric/antisymmetric decay amplitudes, results of
the comparison of the predictions of the SM with present data for several
decays, and the momentum dependence of the diagram
Extraction of the CP-violating phase using and decays
Using the B{\sc a}B{\sc ar}\ measurements of the Dalitz plots for , , , , and decays, we demonstrate that it is
possible to cleanly extract the weak phase . We find four possible
solutions. Three of these -- , , and -- are in
disagreement with the SM, while one -- -- is consistent with the SM.
An advantage of this Dalitz-plot method is that one can obtain many independent
measurements of , thereby reducing its statistical error. An accurate
determination of the errors, however, requires detailed knowledge of the data.Comment: 9 pages, 2 figures, version accepted for publication in Physics
Letters
Extracting alpha from B0(d) --> K0 anti-K0 Decays
We propose a new method for obtaining the CP phase alpha, based on
measurements of B0(d) --> K0 anti-K0, along with theoretical input. Due to the
similarities of QCD factorization (QCDf) and perturbative QCD (pQCD), this
input is basically the same for each of these models. Although the theoretical
error is large at present, many of the contributing quantities will be better
known in the future, leading to a smaller error. One outstanding question is
the extent to which the precision on quark masses, especially m_c/m_b, can be
improved. If one assumes that new physics is not present, the method can be
used to predict the values of CP asymmetries in B0(d) --> K0 anti-K0: 0.02 <=
A_{dir}^2 + A_{mix}^2 <= 0.125. A result outside this range would signal the
existence of long-distance effects beyond those included in models of
nonleptonic decays based on factorization (such as QCDf and pQCD), or the
presence of new physics.Comment: 5 pages, To appear in PR
Sujets variés concernant les désintégrations hadroniques des mésons B
Thèse numérisée par la Division de la gestion de documents et des archives de l'Université de Montréal
Hadronic B Decays: A General Approach
In this paper, we propose a general approach for describing hadronic B
decays. Using this method, all amplitudes for such decays can be expressed in
terms of contractions, though the matrix elements are not evaluated. Many years
ago, Buras and Silvestrini proposed a similar approach. However, our technique
goes beyond theirs in several ways. First, we include recent theoretical and
experimental developments which indicate which contractions are negligible, and
which are expected to be smaller than others. Second, we show that all B-decay
diagrams can be simply expressed in terms of contractions. This constitutes a
formal proof that the diagrammatic method is rigourous. Third, we show that one
reproduces the relations between tree and electroweak-penguin diagrams
described by Neubert and Rosner, and by Gronau, Pirjol and Yan. Fourth,
although the previous results hold to all orders in alpha_s, we show that it is
also possible to work order-by-order in this approach. In this way it is
possible to make a connection with the matrix-element evaluation methods of QCD
factorization (QCDfac) and perturbative QCD (pQCD). Finally, using the
contractions approach, we re-evaluate the question of whether there is a ``B ->
pi K puzzle.'' At O(alpha_s^0), we find that the diagram ratio |C'/T| is about
0.17, a factor of 10 too small to explain all the B -> pi K data. Both QCDfac
and pQCD find that, at O(\alpha_s^1), the value of |C'/T'| may be raised to
only about 2-3 times its lowest-order value. We therefore conclude that,
assuming the effect is not a statistical fluctuation, it is likely that the
value of |C'/T'| is similar to its O(\alpha_s^0) result, and that there really
is a B -> pi K puzzle.Comment: 33 pages, plain latex, 10 figures (included