Sample records for antimesons

  1. On unitarity relations and their application to meson–antimeson mixing

    Indian Academy of Sciences (India)

    G V Dass


    In view of the recent observation of nonexponential decay features for a certain quantummechanical system, we revisit our earlier study of the small-time behaviour of the meson–antimeson complex wherein the commonly employed Weisskopf–Wigner approximation could be tested, in principle. We find that the experiments for this testing are difficult because of (i) the smallness of the times required for this study, (ii) the high accuracy required for probing the nonleading terms (which distinguish this approximation from the general theory) in the small-time behaviour of the relevant probabilities and (iii) the crude knowledge of the required ‘flavour-tagging’ procedures, as available at present.

  2. Heavy Quark Symmetries: Molecular partners of the X(3872 and Zb(10610/Zb′(10650

    Directory of Open Access Journals (Sweden)

    Guo Feng-Kun


    Full Text Available In this work, we have made use of the identification of the X(3872 and Zb(10610/Zb′(10650 as heavy meson-heavy antimeson molecules to establish some consequences derived from the symmetries that these heavy meson-heavy antimeson systems must have. We show the most general effective lagrangian that respects these symmetries only depends on four undetermined low energy constants (LECs, which will be fitted to reproduce the experimental data about the resonances we are identifying as molecular states. Then, we obtain a whole new set of states in the spectrum that could also be thought as heavy meson-heavy antimeson molecules. Finally, using another different symmetry: Heavy Antiquark-Diquark Symmetry, we can also establish a set of pentaquark-like states taking advantage of the previous LEC calculation.

  3. Meson-meson bound states in a (2+1)-dimensional strongly coupled lattice QCD model (United States)

    Faria da Veiga, Paulo A.; O'Carroll, Michael; Neto, Antônio Francisco


    We consider bound states of two mesons (antimesons) in lattice quantum chromodynamics in an Euclidean formulation. For simplicity, we analyze an SU(3) theory with a single flavor in 2+1 dimensions and two-dimensional Dirac matrices. For a small hopping parameter κ and small plaquette coupling g-20, such that 0antimeson-antimeson) bound state solution to the Bethe-Salpeter equation up to the two-meson threshold. Remarkably the absence of such a bound state is an effect of a potential which is nonlocal in space at order κ2, i.e., the leading order in the hopping parameter κ. A local potential appears only at order κ4 and is repulsive. The relevant spectral properties for our model are unveiled by considering the correspondence between the lattice Bethe-Salpeter equation and a lattice Schrödinger resolvent equation with a nonlocal potential.

  4. Quark mixing in the discrete dark matter model

    CERN Document Server

    Toorop, Reinier de Adelhart; Morisi, Stefano


    We consider a model in which dark matter is stable as it is charged under a Z2 symmetry that is residual after an A4 flavour symmetry is broken. We consider the possibility to generate the quark masses by charging the quarks appropriately under A4. We find that it is possible to generate the CKM mixing matrix by an interplay of renormalisable and dimension-six operators. In this set-up, we predict the third neutrino mixing angle to be large and the dark matter relic density to be in the correct range. However, low energy observables - in particular meson-antimeson oscillations - strongly limit the available parameter space.

  5. Probing the perturbative dynamics of exclusive meson pair production

    CERN Document Server

    Harland-Lang, L A; Ryskin, M G; Stirling, W J


    We present the results of a recent novel application of the `hard exclusive' perturbative formalism to the process gg --> MMbar at large angles, where M (Mbar) is a light meson (anti-meson). As well as discussing the important theoretical features of the relevant leading-order gg --> qqbar(gg) qqbar(gg) 6-parton amplitudes, we also comment on their phenomenological implications. In particular, we consider the central exclusive production of meson pairs at comparatively large transverse momentum k_t, which is expected to proceed via this mechanism. We show that this leads to various non-trivial predictions for a range of exclusive processes, and that the cross sections for the eta' and eta mesons display significant sensitivity to any valence gg component of the meson wavefunctions.

  6. A lattice QCD determination of potentials between pairs of static-light mesons

    Energy Technology Data Exchange (ETDEWEB)

    Hetzenegger, Martin


    Potentials between pairs of static-light mesons are interesting in a sense that they give insights in the nature of strong interactions from first principles for multiquark systems. For large heavy quark masses, e.g., the spectra of heavy-light mesons are determined by excitations of the light quark and gluonic degrees of freedom. In particular, the vector-pseudoscalar splitting vanishes and a static-light meson can be interpreted as either a B, a B{sup *}, a D or a D{sup *} heavy-light meson. Calculating potentials between two static-light mesons also enables investigations of possible bound tetraquark states or for particles that are close to the meson-antimeson threshold, such as the X(3872) or the Z{sup +}(4430).

  7. On the Role of One Pion Exchange and Heavy Quark Spin Symmetry in Heavy Meson Molecules

    Directory of Open Access Journals (Sweden)

    Pavón Valderrama M.


    Full Text Available In this contribution we consider the theoretical description of heavy mesonantimeson molecules from the effective field theory perspective. We are interested in the role of one pion exchange and heavy quark spin symmetry in the low energy description of the molecular states. We find that pion exchanges are weaker than naively expected. As a consequence, at lowest order in the effective expansion, the heavy meson-antimeson dynamics are driven by contact range interactions that are in turn heavily constrained by heavy quark spin symmetry. We find that if the X(3872 DD¯*${m{Dar D*}}$ is a bound state with quantum numbers JPC = 1++, we should expect the existence of a 2++ DD¯*${m{Dar D*}}$ molecule with a mass of 4012 MeV. If we also assume the X(3915 resonance to be molecular, we end up deriving the location of three new states with masses of 3710, 3820 and 3855 MeV.

  8. Spectroscopy of mesonic molecules with heavy-light flavour mesons

    CERN Document Server

    Rathaud, D P


    In this work, we have calculated the mass spectra and decay properties of dimesonic (meson-antimeson) bound state in the variational scheme. The intermesonic interaction considered as the Hellmann potential and One Pion Exchange potential. The mass spectra of the $D\\bar{D^{*}}$, $D\\bar{D_{s}^{*}}$, $D_{s}\\bar{D^{*}}$, $D_{s}\\bar{D_{s}^{*}}$, $D^{*}\\bar{D^{*}}$, $D_{s}^{*}\\bar{D_{s}^{*}}$, $D\\bar{B^{*}}$, $D\\bar{B_{s}^{*}}$, $D_{s}\\bar{B^{*}}$, $D_{s}\\bar{B_{s}^{*}}$, $B^{*}\\bar{D}$,$B^{*}\\bar{D_{s}}$, $B\\bar{B^{*}}$, $B_{s}\\bar{B^{*}}$, $B_{c}\\bar{B^{*}}$, $B^{*}\\bar{B^{*}}$, $B^{*}\\bar{B_{s}^{*}}$, $B_{s}^{*}\\bar{B_{s}^{*}}$ etc.. are calculated. The states X(3872), $X_{2c}(4013)$ ,$Z_{b}(10610)/X_{b}$ and $Z_{b}(10650)/X_{b2}$ are compared with $D\\bar{D^{*}}$, $D^{*}\\bar{D^{*}}$, $B\\bar{B^{*}}$ and $B^{*}\\bar{B^{*}}$ dimesonic bound states. To probe the molecular structure of the compared states, we have calculated the decay properties sensitive to their long and short distance structure of hadorinc molecul...

  9. The mass spectra and decay properties of dimesonic states, using the Hellmann potential

    CERN Document Server

    Rai, Ajay Kumar


    Mass spectra of the dimesonic (meson - antimeson) molecular states are computed using the Hellmann potential in variational approach, which consists of relativistic correction to kinetic energy term as well as to the potential energy term. To the study of molecular bound state system, the Hellmann potential of the form $V(r)=-\\frac{\\alpha_{s}}{r} + \\frac{B e^{-Cr}}{r}$ is being used. The one pion exchange potential (OPEP) is also incorporated in the mass calculation. The digamma decay width and decay width of the dimesonic system are evaluated using the wave function. The experimental states such as $f_{0}(980)$, $b_{1}(1235)$, $h_{1}(1380)$, $a_{0}(1450)$, $f_{0}(1500)$, $f_{2}'(1525)$, $f_{2}(15 65)$, $f_{1}(1595)$, $a_{2}(1700)$, $f_{0}(1710)$, $f_{2}(1810)$ are compared with dimesonic states. Many of these states (mass- es and their decay properties) are close to our theoretical predictions.

  10. A Three Doublet Lepton-Specific Model

    CERN Document Server

    Merchand, Marco


    In the lepton-specific version of two Higgs doublet models, a discrete symmetry is used to couple one Higgs, $\\Phi_2$, to quarks and the other, $\\Phi_1$, to leptons. The symmetry eliminates tree level flavor changing neutral currents (FCNC). Motivated by strong constraints on such currents in the quark sector from meson-antimeson mixing, and by hints of $h \\to \\mu\\tau$ in the lepton sector, we study a simple three Higgs doublet model in which one doublet couples to quarks and the other two to leptons. Unlike most other studies of three Higgs doublet models, we impose no flavor symmetry and just use a $Z_2$ symmetry to constrain the Yukawa couplings. We present the model and discuss the various mixing angles. Constraining the parameters to be consistent with observations of the Higgs boson at the LHC, we study the properties of the charged Higgs boson(s) in the model, focusing on the case in which the charged Higgs is above the top threshold. It is found that one can have the branching fraction of the charged ...

  11. Partners of the X(3872) and heavy quark spin symmetry breaking (United States)

    Entem, D. R.; Ortega, P. G.; Fernández, F.


    Since the discovery of the X(3872) the study of heavy meson molecules has been the subject of many investigations. Different experiments have looked for its spin partners and the bottom analogs. On the theoretical side different approaches have been used to understand this state. Some of them as Effective Field Theories (EFT) that impose Heavy Quark Spin Symmetry (HQSS) and so they make predictions for the partners of the X(3872), suggesting the existence of a JPC = 2++ partner in the charm sector or JPC = 1++ or 2++ analogs in the bottom sector. In this work, in order to understand the X(3872), we use a Chiral Quark Model in which, due to the proximity to the DD* threshold, we include cc ¯ states coupled to meson-antimeson DD* molecular components. In this coupled channel model the relative position of the bare cc ¯ states with two meson thresholds are very important. We have looked for the X(3872) partners and we do not find a bound state in the D* D* JPC = 2++. In the bottom sector we find the opposite situation where the B* B* with JPC = 2++ is bounded while the JPC = 1++ is not. These results show how the coupling with cc ¯ states can induce different results than those expected by HQSS. The reason is that this symmetry is worse in the open heavy meson sector than in the hidden heavy meson sector.

  12. The custodially protected Randall-Sundrum model. Theoretical aspects and flavour phenomenology

    Energy Technology Data Exchange (ETDEWEB)

    Blanke, Monika


    Models with a warped extra dimension, so-called Randall-Sundrum models, provide an appealing solution to the gauge and flavour hierarchy problems of the Standard Model. After introducing the theoretical basics of such models, we concentrate on a specific model whose symmetry structure is extended to protect the T parameter and the Zb{sub L} anti b{sub L} coupling from large corrections. We introduce the basic action and discuss in detail effects of electroweak symmetry breaking and the flavour structure of the model. Then we analyse meson-antimeson mixing and rare decays that are affected by new tree level contributions from the Kaluza-Klein modes of the gauge bosons and from the Z boson in an important manner. After deriving analytic expressions for the most important K and B physics observables, we perform a global numerical analysis of the new effects in the model in question. We confirm the recent findings that a stringent constraint on the model is placed by CP-violation in K{sup 0} - anti K{sup 0} mixing. However, even for Kaluza-Klein particles in the reach of the LHC an agreement with all available data can be obtained without significant fine-tuning. We find possible large effects in either CP-violating effects in the B{sub s} - anti B{sub s} system or in the rare K decays, but not simultaneously. In any case the deviations from the Standard Model predictions in the rare B decays are small and difficult to measure. The specific pattern of new flavour effects allows to distinguish this model from other New Physics frameworks, which we demonstrate explicitly for the case of models with Minimal Flavour Violation and for the Littlest Higgs model with T-parity. (orig.)

  13. Two approaches towards the flavour puzzle. Dynamical minimal flavour violation and warped extra dimensions

    Energy Technology Data Exchange (ETDEWEB)

    Albrecht, Michaela E.


    out the flavour and electroweak (EW) sector, including a derivation of Feynman rules. Moreover, we determine the contributions to the effective Hamiltonian for meson-antimeson mixing due to KK gluon and KK photon exchange. (orig.)