Pionic couplings to the lowest heavy-light mesons of positive and negative parity

We present the method and compute the strong couplings of the lowest and first orbitally excited heavy-light mesons to a soft pion in the static heavy quark limit on the lattice. Besides the usual g^ and \~g couplings, we were able to make the first computation of the coupling h using the relevant radial distributions. Our results are obtained from the simulations of QCD with Nf=2 light Wilson-Clover quarks, combined with the improved static quark actions. The hierarchy among couplings that emerges from our study is \~g < g^ < h.Comment: 22 pages, 6 figure

g-coupling (g_B*Bpi,g_D*Dpi); A quark model with Dirac equation

We discuss the strong coupling of heavy mesons to a pion g, in the heavy quark limit. This quantity is quite remarkable since its values as estimated by different methods (various quark models and the QCD sum rules), are surprisingly different. The present quark models are mostly based on free spinors and their predictions depend crucially on the choice of the light quark mass. We propose a quark model based on the Dirac equation in a central potential, which gives a more refined description of Dirac spinors. We show that within such a Dirac model, the value of g is stable and large: g = 0.6(1), where we assume no quark current renormalization ((g_A)q = 1). Such a large result is strongly constrained by requiring that the model parameters fit the spectrum; we show that this implies a large ``effective'' light mass. It is also supported phenomenologically by a similar situation with heavy baryons, as well as by experience with nucleon (if one invokes additivity). We also calculate the couplings to heavy meson excitations, and show that the Adler-Weisberger sum rule is well saturated by a few levels (in contrast to the case of small g). We discuss uncertainties of our approach, and rise several questions which remain to be answered. The main mystery is the large, unusual discrepancy with QCD sum rules for g, whereas a good agreement is found for orbital excitations.Comment: 20 pages, LaTeX file, uses JHEP.cls, (2 references added

H(650) -> W+W-/ZZ predicts H++ -> W+W+ and H+ -> ZW+, as indicated by LHC data

Several indications for neutral scalars are observed at the LHC. One of them, a broad resonance peaked at about 650 GeV which we call H(650), was first observed by an outsider combining published histograms from ATLAS and CMS on ZZ ->4 leptons searches, and this combination shows a local significance close to 4 s.d. Since then, CMS has reported two other indications at the same mass, with similar local significances: H ->WW -> lepton nu lepton nu and H->bbh(125) where h(125) ->2 photons. ATLAS has completed its analysis of ZZ->4 leptons from which we infer an indication for H(650) with 3.5 s.d. significance. Assuming that the mass is already known from the former set, and combining these three results, one gets a global statistical significance above 6 s.d. H(650) has a coupling to WW similar to h(125) and therefore we argue that a sum rule (SR) required by unitarity for WW scattering implies that there should be a compensating effect from a doubly charged scalar H++, with a large coupling to W+W+. We therefore predict that this mode should become visible through the vector boson fusion process W+W+->H++, naturally provided by LHC. A recent indication for H++(450)->W+W+ from ATLAS allows a model independent interpretation of this result through the SR constraint which gives BR(H++->W+W+)=10%, implying the occurrence of additional decay modes H+W+ and H+H+ from one or several light H+ with masses below mH++ - mW or MH++/2, that is mH+ ZW, indicated by ATLAS and CMS. Both channels suggest a scalar field content similar to the Georgi Machacek model with triplets, at variance with the models usually considered.Comment: 17 pages, 6 figures, Work in preparation of the 2023 ECFA Workshop on Higgs/EW/Top factories in Paestum (Salerno) / Italy from 11 - 13 October 202

On the significance of B-decays to radially excited D

We discuss the possibilities of testing the recent claims of a relatively large value of the B --> D' transition form factor through B0--> D' pi+ and B- --> D' pi- decay modes. To estimate the width of the latter we need the decay constant of the radially excited D-meson that we computed in lattice QCD with Nf=2 dynamical flavors and after taking the continuum limit we found f(D')=117(25) MeV. We also provide an update for the values of the D-meson decay constants obtained by using maximally twisted mass QCD.Comment: 16 pages including 5 tables and 3 figures [published version

Pseudoscalar Vertex and Quark Masses

We analyse available data on the quark pseudoscalar vertex and extract the contribution og the Goldstone boson pole. The strength of the pole is found to be quite large at presently accessible scales. We draw the important consequences of this finding for the various definitions of quark masses.Comment: LATTICE99 (Improvement and Renormalization), 3 p., 3 fi

The strong decays of K1 resonances

We investigate the K1--> K pi pi strong interaction decays. Using the 3P0 quark-pair-creation model to derive the basic parametrization, we discuss in detail how to obtain the various partial wave amplitudes into the possible quasi-two-body decay channels as well as their relative phases from the currently available experimental data. We obtain the K1 mixing angle to be thetaK1= 60 deg, in agreement with previous works. Our study can be applied to extract the information needed for the photon polarization determination of the radiative B--> K1 gamma decay.Comment: 57 pages, 10 figure

The controversy about "1/m_Q duality violation" ; a quark model point of view

A detailed discussion based on exact calculations, possible in the non relativistic quark model, is given to show that there is no 1/m_Q term in the heavy quark expansion of totally integrated semileptonic decay rates. More generally, it is shown that OPE holds with very few terms in the expansion, at least in the harmonic oscillator model.Comment: 10 pages, full articl

Searches for scalars at LHC and interpretation of the findings

In view of the future Higgs factories, this work presents the status of scalar searches at the LHC with an emphasis on the H(650) resonance which has been observed in WW, ZZ and h(95)h(125) channels, with a cumulative evidence of about 7 s.d. global significance. Its interpretation in models, restricted to extension of the scalar sector by SU(2) singlets and doublets, is clearly excluded, while its interpretation in models with additional triplets requires an extension with respect to the conventional Georgi-Machacek model. A general picture of these searches is updated, showing that h(95) is also reaching a similar level of evidence while two other candidates, A(400) and h(151), although less prominent, are above the 4 s.d. global evidence.Comment: 14 pages, 9 figures, Work presented by F. Richard at the ECFA workshop on Higgs/EW/top factories in DESY, October 202