Dynamically Spontaneous Symmetry Breaking and Masses of Lightest Nonet Scalar Mesons as Composite Higgs Bosons

Based on the (approximate) chiral symmetry of QCD Lagrangian and the bound state assumption of effective meson fields, a nonlinearly realized effective chiral Lagrangian for meson fields is obtained from integrating out the quark fields by using the new finite regularization method. As the new method preserves the symmetry principles of the original theory and meanwhile keeps the finite quadratic term given by a physically meaningful characteristic energy scale $M_c$, it then leads to a dynamically spontaneous symmetry breaking in the effective chiral field theory. The gap equations are obtained as the conditions of minimal effective potential in the effective theory. The instanton effects are included via the induced interactions discovered by 't Hooft and found to play an important role in obtaining the physical solutions for the gap equations. The lightest nonet scalar mesons($\sigma$, $f_0$, $a_0$ and $\kappa$) appearing as the chiral partners of the nonet pseudoscalar mesons are found to be composite Higgs bosons with masses below the chiral symmetry breaking scale $\Lambda_{\chi} \sim 1.2$ GeV. In particular, the mass of the singlet scalar (or the $\sigma$) is found to be $m_{\sigma} \simeq 677$ MeV.Comment: 15 pages, Revtex, published version, Eur. Phys. J. C (2004) (DOI) 10.1140/epjcd/s2004-01-001-

Momentum imbalance of isolated photon-tagged jet production at RHIC and LHC

In collisions of ultra-relativistic nuclei, photon-tagged jets provide a unique opportunity to compare jet production and modification due to parton shower formation and propagation in strongly-interacting matter at vastly different center-of-mass energies. We present first results for the cross sections of jets tagged by an isolated photon to ${\cal O}(\alpha_{\rm em} \alpha_s^2)$ in central Au+Au reactions with $\sqrt{s_{NN}}=200$ GeV at RHIC and central Pb+Pb reactions with $\sqrt{s_{NN}}=2.76$ TeV at LHC. We evaluate the increase in the transverse momentum imbalance of the observed $\gamma$+jet state, induced by the dissipation of the parton shower energy due to strong final-state interactions. Theoretical predictions to help interpret recent and upcoming experimental data are presented.Comment: 4 pages, 3 eps figures, 1 table. Version to appear in PR

g-2 in composite models of leptons

Based on the bound state description of the muon and general relativistic covariant quantum field theory, we illustrate with a simple composite model that the observed deviation of (g-2)_\mu can be a demonstration of the substructure of the muon and give the constraints on the radius of the muon in different cases of light constituents and heavy constituents.Comment: 14 pages, 4 eps figures, revtex, several arguments and some references renewe

Twist-3 contribution to the pion electromagnetic form factor

Non-leading contribution to the pion electromagnetic form factor which comes from the pion twist-3 wave function is analyzed in the modified hard scattering approach (MHSA) proposed by Li and Sterman. This contribution is enhanced significantly due to bound state effect (the twist-3 wave function is independent of the fractional momentum carried by the parton and has a large factor $\sim m_\pi^2/m_0$ with $m_\pi$ being the pion meson mass and $m_0$ being the mean u- and d-quark masses). Consequently, although it is suppressed by the factor $1/Q^2$, the twist-3 contribution is comparable with and even larger than the leading twist (twist-2) contribution at intermediate energy region of $Q^2$ being $2 \sim 40 {GeV}^2$.Comment: 10 pages, 2 fgures, latex. More discussions on the Sudakov effect added, references added. To appear in European Physical Journal C (Zeitschrift fur Physik C