36067168
Dimensional regularization and perturbative solution of the chiral Schwinger model.
The anomalous chiral Schwinger model is regulated by the method of dimensional regularization and is solved by diagrammatic perturbative expansion. It is shown that there is a regulation ambiguity in the solution. The result disagrees with Das's assertion and agrees with that of Jackiw, Rajaraman, and others.
17940028
Perturbative QCD analysis of B meson decays.
The resummation of large QCD radiative corrections, including leading and next-to-leading logarithms, in the pion electromagnetic form factor is reviewed. A similar formalism is applied to exclusive processes involving heavy mesons, and leads to Sudakov suppression for the semileptonic decay {ital B}{r_arrow}{pi}{ital l}{nu}. It is found that, with the inclusion of Sudakov effects, a perturbative QCD analysis of this decay is reliable for the energy fraction of the pion above 0.4. Combining predictions from soft pion theorems we estimate that the upper limit of the matrix element {parallel}{ital V}{sub {ital ub}}{parallel} is 2.8{endash}4.8{times}10{sup {minus}3} from different models of the {ital B} meson wave function. {copyright} {ital 1996 The American Physical Society.}
23954147
Heavy-quark symmetry and chiral dynamics.
The flavor and spin symmetry of the heavy quarks and the spontaneously broken approximate SU(3){sub {ital L}}{times} SU(3){sub {ital R}} chiral symmetry of the light quarks are exploited to formulate a theory describing the low-energy interactions of the heavy mesons ({ital Q{bar q}} bound states) and heavy baryons ({ital Qq}{sub 1}{ital q2} bound states) with the Goldstone bosons {pi}, {ital K}, and {eta}. The theory contains only three parameters independent of the number of heavy-quark species involved. They can be determined by the decays {ital D}{sup *}{r arrow}{ital D}+{pi}, {Sigma}{sub {ital c}}{r arrow}{Lambda}{sub {ital c}}+{pi}, and {Sigma}{sub {ital c}}{sup *}{r arrow}{Sigma}{sub {ital c}}+{pi}. Theoretically, these coupling constants are related, through partial conservation of axial-vector current, to the axial charges of the heavy mesons and the heavy baryons. They are all calculable in the nonrelativistic quark model by using the spin wave functions of these particles alone. The theory is applied to strong decays and semileptonic weak decays of the heavy mesons and baryons. The implications are also discussed.
42674415
PQCD analysis of inclusive semileptonic decays of B mesons.
We develop the perturbative QCD formalism for inclusive semileptonic {ital B} meson decays, which includes Sudakov suppression from the resummation of large radiative corrections near the high end of charged lepton energy. Transverse degrees of freedom of partons are introduced to facilitate the factorization of {ital B} meson decays. Ambiguities appearing in the quark-level analysis are then avoided. A universal distribution function, arising from the nonperturbative Fermi motion of the {ital b} quark, is constructed according to the heavy quark effective field theory based operator product expansion, through which the mean and the width of the distribution function are related to hadronic matrix elements of local operators. Charged lepton spectra of the {ital B}{r_arrow}{ital X}{sub {ital ul}}{nu} decay are presented. We find 50{percent} suppression near the end point of the spectrum. The overall suppression on the total decay rate is 8{percent} for the free quark model, and is less than 7{percent} for the use of smooth distribution functions. With our predictions, it is then possible to extract the Cabibbo-Kobayashi-Maskawa matrix element {parallel}{ital V}{sub {ital ub}}{parallel} from experimental data. We also discuss possible implications of our analysis when confronted with the rather small observed semileptonic branching ratio in {ital B} mesonmore » decays. {copyright} {ital 1996 The American Physical Society.}« less
43012116
Are there really no experimental limits on a light Higgs boson from kaon decay?
We reexamine the theoretical estimates of the decay {ital K}{r arrow}{pi}{ital H} and the experimental constraints on the existence of a light Higgs boson from this process. We find that (i) pole diagrams generated from the Higgs-boson--gluon coupling via a loop of heavy quarks do contribute to {ital K}{r arrow}{pi}{ital H}, (ii) there is an additional contribution to the {ital K}{r arrow}{pi}{ital H} amplitude coming from the effective {ital KHW} and {pi}{ital HW} couplings, (iii) even if {ital B}, the unknown parameter in the chiral-Lagrangian description of {ital K}{endash}{pi}{ital H} transitions, is nonzero and even if the real part of the {ital K}{r arrow}{pi}{ital H} amplitude is canceled accidentally, the imaginary contribution alone suffices to rule out a Higgs boson lighter than 2{ital m}{sub {pi}}, and (iv) whether Higgs bosons in the mass range 2{ital m}{sub {pi}}{lt}m{sub H}{lt}350 MeV are excluded by the imaginary part of the {ital K}{r arrow}{pi}{ital H} amplitude depends on the branching ratio of {ital H}{r arrow}{mu}{sup +}{mu}{sup {minus}} and the top-quark mass. Decay modes {ital K}{sub {ital L}}{r arrow}{pi}{sup +}{pi}{sup {minus}}H and {ital K}{sup +}{r arrow}l{sup +}{nu}H are briefly discussed.
13594754
Heavy-flavor-conserving nonleptonic weak decays of heavy baryons.
The heavy-flavor-conserving nonleptonic weak decays of heavy baryons are studied in a formalism that incorporates both heavy-quark symmetry and chiral symmetry. The phenomenological {Delta}{ital S}=1 nonleptonic weak chiral Lagrangian for these transitions contains two independent coupling constants that describe the transitions between two flavor-SU(3) antitriplet heavy baryons, and the transitions between two flavor-SU(3) sextet heavy baryons. In the MIT bag model and the diquark model, only transitions between antitriplets are allowed. The coupling constants for these transitions are calculated in both models. The result is applied to specific nonleptonic decays such as {Xi}{sub {ital c}}{r arrow}{Lambda}{sub {ital c}}{pi}, and the branching ratios are found to be of the order of 10{sup {minus}4}. An example of a nonleptonic decay due to symmetry breaking is provided by {Omega}{sub {ital c}}{r arrow}{Xi}{sub {ital c}}{sup {prime}}{pi}, which is estimated to have a smaller branching ratio, of the order of 10{sup {minus}5}.
45380547
Glueball components of the meson f2(1270).
It is shown that in order to explain the ratios {ital x} and {ital y} of the helicity amplitudes for the process {ital J}/{psi}{r arrow}{gamma}+{ital f}{sub 2}(1270) and the experimental datum {ital R}={ital B}({psi}{prime}({bold 3685}){r arrow}{gamma}+{bold f}{sub {bold 2}}({bold 1270}))/{ital B}({ital J}/{psi}{r arrow}{gamma}+{ital f}{sub {bold 2}}({bold 1270})) =(9{plus minus}3)% in terms of the mixture between the meson {ital f}{sub 2}(1270) and a 2{sup ++} glueball, two {ital D}-wave components have to be considered in addition to the {ital S}-wave component of the 2{sup ++} glueball.