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Register a new userComposite Vector Mesons from QCD to the Little Higgs
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Authors
Maurizio Piai
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We review how the rho meson can be modeled in an effective theory and discuss the implications of applying this approach to heavier spin-one resonances. Georgis vector limit is explored, and its relationship to locality in a deconstructed extra-dimension is discussed. We then apply the formalism for rhos to strongly coupled theories of electroweak symmetry breaking, studying the lightest spin-one techni-rho resonances. Understanding these new particles in Little Higgs models can shed light on previously incalculable, ultraviolet sensitive physics, including the mass of the Higgs boson.
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We study $bar qq$-hybrid mixing for the light vector mesons and $bar qq$-glueball mixing for the light scalar mesons in Monte-Carlo based QCD Laplace sum rules. By calculating the two-point correlation function of a vector $bar qgamma_mu q$ (scalar $bar q q$) current and a hybrid (glueball) current we are able to estimate the mass and the decay constants of the corresponding mixed physical state that couples to both currents. Our results do not support strong quark/gluonic mixing for either the $1^{--}$ or the $0^{++}$ states.
A previous formal derivation of the effective chiral Lagrangian for low-lying pseudoscalar mesons from first-principles QCD without approximations [Wang et al., Phys. Rev. D61, (2000) 54011] is generalized to further include scalar, vector, and axial-vector mesons. In the large Nc limit and with an Abelian approximation, we show that the properties of the newly added mesons in our formalism are determined by the corresponding underlying fundamental homogeneous Bethe--Salpeter equation in the ladder approximation, which yields the equations of motion for the scalar, vector, and axial-vector meson fields at the level of an effective chiral Lagrangian. The masses appearing in the equations of motion of the meson fields are those determined by the corresponding Bethe--Salpeter equation.
We calculate the tree-level expressions for the electroweak precision observables in the SU(5)/SO(5) littlest Higgs model. The source for these corrections are the exchange of heavy gauge bosons, explicit corrections due to non-linear sigma-model dynamics and a triplet Higgs VEV. Weak isospin violating contributions are present because there is no custodial SU(2) global symmetry. The bulk of these weak isospin violating corrections arise from heavy gauge boson exchange while a smaller contribution comes from the triplet Higgs VEV. A global fit is performed to the experimental data and we find that throughout the parameter space the symmetry breaking scale is bounded by f > 4 TeV at 95% C.L. Stronger bounds on f are found for generic choices of the high energy gauge couplings. We find that even in the best case scenario one would need fine tuning of less than a percent to get a Higgs mass as light as 200 GeV.
We develop a non-perturbative analysis of the electro-production of heavy vector mesons ($phi$, $J/Psi$) from threshold to high energy. We use the holographic construction with bulk confinement enforced through a soft wall. Using Witten diagrams, we evaluate the pertinent cross sections for heavy vector mesons ($phi$, $J/Psi$) production and study their dependence on both the incoming virtual photon polarization as well as the outgoing polarization of the heavy meson. Our results for $J/Psi$ electro-production compares well with the available HERA data at low and intermediate $Q^2$, and for a wide range of momentum transfer. We also predict the quasi-real electro-production of $J/Psi$ near threshold.
The magnetic and quadrupole moments of the vector and axial-vector mesons containing heavy quark are estimated within the light cone sum rules method. Our predictions on magnetic moments for the vector mesons are compared with the results obtained by other approaches.
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