Ref Arxiv: hep-ph/0103135
DOI: 10.2001EPJC...20..659G
Ref. & Cit.: NASA ADS
Résumé:

The process $\gamma\gamma\to Z H $ first arises at the one loop level, and as such it provides us with remarkable tests of the structure of the electroweak Higgs sector. These tests are complementary to those in the gauge sector involving $\gamma\gamma\to \gamma\gamma, \gamma Z, ZZ$. We show that in the standard model (SM) where H=HSM, as well as in the supersymmetric case where H=h0, H0 or A0, observables exist (like e.g. the energy dependence, angular distribution, photon polarization dependence or final Z polarization) which present rather spectacular properties. Such properties involve strong threshold effects with steps, bumps or peaks, reflecting the type of Higgs and heavy quarks and chargino masses and couplings predicted by the SM and supersymmetric models.

Ref HAL: hal-00347339_v1
Ref Arxiv: hep-ph/9912527
DOI: 10.1016/S0550-3213(00)00198-X
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
53 citations
Résumé:

We study the associated production of charged Higgs bosons with $W$ gaugebosons in high energy $e^+ e^-$ collisions at the one loop level. We presentthe analytical results and give a detailed discussion for the total crosssection predicted in the context of a general Two Higgs Doublet Model (THDM).

Commentaires: Latex, 31 pages, 6 figures, cosmetically improved and one reference added Journal: Nucl.Phys. B581 (2000) 34-60; Erratum-ibid. 2004 (2004) 400-401

Ref Arxiv: hep-ph/0012235
DOI: 10.1016/S0920-5632(01)01137-9
Ref. & Cit.: NASA ADS
35 citations
Résumé:

We review the analysis of the quark and gluon substructures of the scalar mesons from QCD spectral sum rules and some low-energy theorems applied to the scalar QCD anomaly current. The present data favour equal components of \bar uu+ \bar dd and of gg in the wave functions of the low-mass (below 1 GeV) scalar mesons, which make the wide \sigma and the narrow f_0(980) as \eta'-like particles, which can have strong couplings to meson pairs through OZI violations. A coherent picture of the other I=0 scalar mesons spectra within this mixing scheme is shortly discussed. We also expect the a_0(980) to be the lowest isovector \bar ud state, and the K^*_0(1430) its \bar ds partner.

Commentaires: Two-column latex files, 8 pages

Ref Arxiv: hep-ph/0012019
DOI: 10.1016/S0920-5632(01)01154-9
Ref. & Cit.: NASA ADS
11 citations
Résumé:

Recent ALEPH/OPAL data on the V-A spectral functions from hadronic tau decays are used for fixing the QCD continuum threshold at which the first and second Weinberg sum rules should be satisfied in the chiral limit, and for predicting the values of the low-energy constants f_\pi,~m_{\pi^+}-m_{\pi^0} and {L}_{10}. Some DMO-like sum rules and the $\tau$-total hadronic widths R_{\tau,V-A} are also used for extracting the values of the D=6,~8 QCD vacuum condensates and the corresponding (in the chiral limit) electroweak kaon penguin matrix elements Q^{3/2}_{8,7}\ra_{2\pi},, where a deviation from the vacuum saturation estimate has been obtained. Combining these results with the one of the QCD penguin matrix element Q^{1/2}_{6}\ra_{2\pi} obtained from a (maximal) \bar qq-gluonium mixing scheme from the scalar meson sum rules, we deduce, in the Electroweak Standard Model (ESM), the conservative upper bound for the CP-violating ratio: \epsilon'/\epsilon \leq (22\pm 9) 10^{-4}, in agreement with the present measurements.

Commentaires: This is a summary of the paper “New QCD Estimate of the Kaon Penguin Matrix Elements” hep-ph/0004247 (Nucl. Phys. B in press).

Ref Arxiv: hep-ph/0009108
Ref. & Cit.: NASA ADS
Résumé:

Within the increasing experimental evidence of the existence of the I=0 scalar low mass and wide \sigma meson, we review the {\it first} analysis of its quark and gluon substructure from QCD spectral sum rules and some low-energy theorems. The present data favour equal components of \bar uu+ \bar dd and of gg in its wave function, which make the wide sigma and the narrow f_0(980) as \eta'-like particles. A coherent picture of the other I=0 scalar mesons spectra within this mixing scheme is shortly discussed. We also expect the a_0(980) to be the lowest isovector \bar ud state, and the K^*_0(1430) its \bar ds partner.

Commentaires: Plenary talk given at the Workshop on `` Possible existence of the Light $\sigma$-resonance and its applications to hadron physics" (Yukawa Institute for Theoretical Physics, Kyoto, Japan, 11-14th June 2000) and Review talk given at the QCD 00 International Euroconference (15th anniversary) Montpellier, France 6-13th July 2000

Ref Arxiv: hep-ph/0010205
DOI: 10.1103/PhysRevD.63.053013
Ref. & Cit.: NASA ADS
49 citations
Résumé:

The production of a tt¯ pair from lepton-antilepton annihilation is considered for values of the center of mass energy much larger than the top-quark mass, typically of a few TeV size. In this regime a number of simplifications occur that allow us to derive the leading asymptotic terms of various observables using the same theoretical description that was used for light quark production. Explicit examples are shown for the standard model and the minimal supersymmetric standard model cases.

Ref Arxiv: hep-ph/0004247
DOI: 10.1016/S0550-3213(00)00618-0
Ref. & Cit.: NASA ADS
45 citations
Résumé:

Firstly, we use the recent ALEPH/OPAL data on the V-A spectral functions for fixing the continuum threshold with which the first and second Weinberg sum rules should be satisfied in the chiral limit. Then, we predict the values of the low-energy constants m_{\pi^+}-m_{\pi^0}, {L}_{10}, and test the values of the electroweak kaon penguin matrix elements _{2\pi} obtained from DMO--like sum rules. Secondly, we use the data on the \tau-total hadronic width R_{\tau,V/A} for extracting , in the {MS}\bar scheme, and propose some new sum rules for < Q_7^{3/2}>_{2\pi} in the chiral limit, where the latter require more accurate data for the spectral functions near the $\tau$-mass. Thirdly, we analyze the effects to the matrix element _{2\pi}, of the S_2\equiv(\bar uu+\bar dd) component of the I=0 scalar meson, with its parameters fixed from QCD spectral sum rules. Our results should stimulate a further attention on the r\^ole of the (expected large) gluonium component of the I=0 scalar meson and of the associated operator in the K--->\pi\pi amplitude. Finally, using our previous determinations, we deduce, in the Standard Model (SM), the conservative upper bound for the CP-violating ratio: \epsilon'/\epsilon < (22\pm 9) 10^{-4}, which is in agreement with the present measurements.