Showing papers by "Johan Bijnens published in 2011"
TL;DR: In this paper, the authors extended the results of the massive O(N) nonlinear sigma model to other observables and derived expressions at leading order in the large N expansion at all orders in the loop expansion for the decay constant, vacuum expectation value, meson meson scattering and the scalar and vector form factors.
44 citations
TL;DR: In this article, the meson-meson scattering at next-to-next-leading order in the chiral expansion for QCD-like theories with general n degenerate flavors for the cases with a complex, real and pseudo-real representation was discussed.
Abstract: We discuss meson-meson scattering at next-to-next-to-leading order in the chiral expansion for QCD-like theories with general n degenerate flavours for the cases with a complex, real and pseudo-real representation. i.e. with global symmetry and breaking pattern SU(n)
L
× SU(n)
R
→ SU(n)
V
, SU(2n) → SO(2n) and SU(2n) → Sp(2n). We obtain fully analytical expressions for all these cases. We discuss the general structure of the amplitude and the structure of the possible intermediate channels for all three cases. We derive the expressions for the lowest partial wave scattering length in each channel and present some representative numerical results. We also show various relations between the different cases in the limit of large n.
44 citations
TL;DR: In this paper, the authors studied how general two Higgs doublet models can be constrained by considering their properties under renormalization group evolution of the Yukawa couplings and found that the latter condition can be used to limit the amount of Z2 symmetry breaking allowed in a given model.
Abstract: We study how general two Higgs doublet models can be constrained by considering their properties under renormalization group evolution of the Yukawa couplings. We take into account both the appearance of a Landau pole as well as off-diagonal Yukawa couplings leading to flavour changing neutral currents in violation with experimental constraints at the electroweak scale. We find that the latter condition can be used to limit the amount of Z2 symmetry breaking allowed in a given model.
41 citations
TL;DR: In this paper, the authors used three-flavour hard pion Chiral Perturbation Theory (HPChPT) in both the heavy meson and a relativistic formulation to calculate the chiral logarithms m(2) log (m(2)/mu(2)) contributing to the formfactors of the B-(s) -> pi, K, eta and D-(s, K) transitions at momentum transfer q( 2) away from the endpoint q(max)(2) = (m (B) - m(M
36 citations
13 citations
TL;DR: In this paper, the meson-meson scattering at next-to-next-leading order in the chiral expansion for QCD-like theories with general $n$ degenerate flavors for the cases with a complex, real and pseudo-real representation was discussed.
Abstract: We discuss meson-meson scattering at next-to-next-to-leading order in the chiral expansion for QCD-like theories with general $n$ degenerate flavours for the cases with a complex, real and pseudo-real representation. I.e. with global symmetry and breaking pattern $SU(n)_L\times SU(n)_R\to SU(n)_V$, $SU(2n)\to SO(2n)$ and $SU(2n)\to Sp(2n)$. We obtain fully analytical expressions for all these cases. We discuss the general structure of the amplitude and the structure of the possible intermediate channels for all three cases. We derive the expressions for the lowest partial wave scattering length in each channel and present some representative numerical results. We also show various relations between the different cases in the limit of large $n$.
4 citations
TL;DR: In this paper, the authors apply hard pion chiral perturbation theory to charmonium decays to ππ, KK and ηη, and show that the leading chiral logarithm is absent for χc0, φc2 → PP.
Abstract: We apply hard pion Chiral Perturbation Theory to charmonium decays to ππ, KK and ηη. We first discuss why we expect to be able to provide results for the chiral logarithms in χc0 and χc2 decays to two pseudoscalars while for the decays from J/ψ, ψ(nS) and χc1 no simple prediction is possible. The leading chiral logarithm turns out to be absent for χc0, χc2 → PP. This result is true for all fully chiral singlet states of spin zero and two.
4 citations
TL;DR: In this article, the vector, axial-vector, scalar and pseudo-scalar two-point functions up to two-loop level in the low-energy effective field theory for three different QCD-like theories were calculated.
Abstract: We calculated the vector, axial-vector, scalar and pseudo-scalar two-point functions up to two-loop level in the low-energy effective field theory for three different QCD-like theories. In addition we also calculated the pseudo-scalar decay constant $G_M$. The QCD-like theories we used are those with fermions in a complex, real or pseudo-real representation with in general n flavours. These case correspond to global symmetry breaking pattern of $SU(n)_L\times SU(n)_R\to SU(n)_V$, $SU(2n)\to SO(2n)$ or $SU(2n)\to Sp(2n)$. We also estimated the S parameter for those different theories.
1 citations
TL;DR: In this article, the authors apply hard conjecture chiral perturbation theory to charmonium and show that the leading chiral logarithm is absent for all singlet states of spin zero and two.
Abstract: We apply hard pion Chiral Perturbation Theory to charmonium decays to $\pi\pi$, $KK$ and $\eta\eta$. We first discuss why we expect to be able to provide results for the chiral logarithms in $\chi_{c0}$ and $\chi_{c2}$ decays to two pseudoscalars while for the decays from $J/\psi$, $\psi(nS)$ and $\chi_{c1}$ no simple prediction is possible. The leading chiral logarithm turns out to be absent for $\chi_{c0},\chi_{c2}\to PP$. This result is true for all fully chiral singlet states of spin zero and two.
Posted Content•
TL;DR: In this paper, a short introduction to hard pion chiral perturbation theory and an overview of the available applications for the semileptonic decays is given. And it is pointed out that the reults for the decays obey the LEET relation between $f+$ and $f_-$.
Abstract: In this talk I give a short introduction to hard pion Chiral Perturbation Theory and an overview of the available applications $K\to\pi\pi$, $B,D\to D,\pi,K,\eta$ semileptonic decays and $\chi_{c0,2}\to\pi\pi,KK$. It is pointed out that the reults for the semileptonic decays obey the LEET relation between $f_+$ and $f_-$.