Relaxing Lorentz invariance in general perturbative anomalies

We analyze the role of Lorentz symmetry in the perturbative non-gravitational anomalies for a single family of fermions. The theory is assumed to be translational invariant, power-counting renormalizable and based on a local action, but is allowed to have general Lorentz violating operators. We study the conservation of global and gauge currents associate with general internal symmetry groups and find, by using a perturbative approach, that Lorentz symmetry does not participate in the clash of symmetries that leads to the anomalies. We first analyze the triangle graphs and prove that there are regulators for which the anomalous part of the Ward identities exactly reproduces the Lorentz invariant case. Then we show, by means of a regulator independent argument, that the anomaly cancellation conditions derived in Lorentz invariant theories remain necessary ingredients for anomaly freedom.Comment: 18 pages, 1 figure. Few comments added. Article published in Physical Review

Phase Equilibria Modeling of Low-Grade Metamorphic Martian Rocks

We report on modeling low-grade (up to 300 °C) metamorphic reactions with Martian starting materials

Neutral ZZ boson pair production due to radion resonance in the Randall-Sundrum model: prospects at the CERN LHC

The Neutral $Z$ boson pair production due to radion resonance at the Large Hadron Collider (LHC) is an interesting process to explore the notion of warped geometry (Randall-Sundrum model). Because of the enhanced coupling of radion with a pair of gluons due to trace enomaly and top(quark) loop, the radion can provide larger event rate possibility as compared to any New Physics effect. Using the proper radion-top-antitop (with the quarks being off-shell) coupling, we obtain the correct radion production rate at LHC and explore several features of a heavier radion decaying into a pair of real $Z$ bosons which subsequently decays into charged $4 l (l=e, \mu)$ leptons (the gold-plated mode). Using the signal and background event rate, we obtain bounds on radion mass $m_\phi$ and radion vev \vphi at the $5\sigma$, $10\sigma$ discovery level.Comment: 17 pages, 4 figures, minor changes in the text, result unchanged. Version to appear in Phys. Rev.

Singularities of Scattering Amplitudes on Unphysical Sheets and Their Interpretation

The analytic structure of two-particle scattering amplitudes on the unphysical sheet of the Riemann surface reached by crossing the two-particle cut is discussed. The singularities of the amplitudes there are shown to be poles and their physical interpretation is studied. The way in which bound states appear on the physical sheet in the Mandelstam representation, both as isolated poles and as cuts, is traced in detail. The properties of partial wave amplitudes and of the full amplitude as a function of energy and angle and of energy and momentum transfer are discussed. Finally, a few remarks are made in connection with unstable states

Effects of an extra U(1) axial condensate on the strong decays of pseudoscalar mesons

We consider a scenario (supported by some lattice results) in which a U(1)-breaking condensate survives across the chiral transition in QCD. This scenario has important consequences for the pseudoscalar-meson sector, which can be studied using an effective Lagrangian model. In particular, generalizing the results obtained in two previous papers, where the effects on the radiative decays eta,eta' --> gamma gamma were studied, in this paper we study the effects of the U(1) chiral condensate on the strong decays of the "light" pseudoscalar mesons, i.e., eta,eta' --> 3pi^0; eta,eta' --> pi^+ pi^- pi^0; eta' --> eta pi^0 pi^0; eta' --> eta pi^+ pi^-; and also on the strong decays of an exotic ("heavy") SU(3)-singlet pseudoscalar state eta_X, predicted by the model.Comment: One misprint in Eq. (2.10) has been eliminated; Eqs. (B.8) and (B.9) in Appendix B have been corrected; 46 pages, 1 tabl

Form factors in β decay and μ capture

We suppose that β decay and μ capture are described by a universal vector and axial vector Lagrangian and we consider, via dispersion relation techniques, the properties of the corresponding S-matrix elements. Owing to the strong interactions of the nucleons, the structure of the S matrix is expected to be more complicated than that of the Lagrangian. In the former, vector and axial vector terms appear, but with coefficients which in general depend on the invariant nucleon momentum transfer; they can be thought of as Fermi interaction form factors. Moreover, two additional kinds of terms can appear in the S-matrix elements: one which simulates a direct pseudoscalar coupling and one which simulates a direct coupling involving derivatives of the nucleon wave functions. The latter is probably too small to have any experimental significance. The former, though negligible in β decay, may be appreciable in μ capture. We estimate the effective pseudoscalar coupling coefficient there to be about eight times as large as the axial vector coefficient. More generally, we investigate the structure of the various form factors; and we also reconsider, in further refinement, a recent quantitative discussion which we have given of π→μ+ν decay

A soluble problem in dispersion theory

The Lee model is modified by addition of a new field θ′ and a weak coupling N+θ→N+θ′, which leads to instability of the V particle: V→N+θ→N+θ′. The decay amplitude is calculated to lowest order in the weak coupling by dispersion relation methods. In effect we are required to study a set of simultaneous dispersion relations. The problem is completely soluble and serves to clarify the essential structure of dispersion methods. The results agree with what one obtains, more easily in the present case, by direct methods

Distribution amplitudes and decay constants for (π,K,ρ,K∗)(\pi,K,\rho,K^*) mesons in light-front quark model

We present a calculation of the quark distribution amplitudes(DAs), the Gegenbauer moments, and decay constants for $\pi,\rho,K$ and $K^*$ mesons using the light-front quark model. While the quark DA for $\pi$ is somewhat broader than the asymptotic one, that for $\rho$ meson is very close to the asymptotic one. The quark DAs for $K$ and $K^*$ show asymmetric form due to the flavor SU(3)-symmetry breaking effect. The decay constants for the transversely polarized $\rho$ and $K^*$ mesons($f^T_\rho$ and $f^T_{K^*}$) as well as the longitudinally polarized ones($f_\rho$ and $f_{K^*}$) are also obtained. Our averaged values for $f^T_V/f_V$, i.e. $(f^T_\rho/f_\rho)_{\rm av}=0.78$ and $(f^T_{K^*}/f_{K^*})_{\rm av}=0.84$, are found to be consistent with other model predictions. Especially, our results for the decay constants are in a good agreement with the SU(6) symmetry relation, $f^T_{\rho(K^*)}=(f_{\pi(K)}+f_{\rho(K^*)})/2$.Comment: 12 pages, 6figure

Decay of the pi meson

A quantitative study of π→μ+ν decay is presented using the techniques of dispersion theory. The discussion is based on a model in which the decay occurs through pion disintegration into a nucleon-antinucleon pair, the latter annihilating via a Fermi interaction to produce the leptons. The weak vertex contains effectively both axial vector and pseudoscalar couplings even if one adopts the point of view of a universal axial vector and vector Fermi interaction. The pion-nucleon vertex which enters our model is also calculated using dispersion techniques. Under the assumption that this vertex is damped for large momentum transfers, we obtain a result for the pion lifetime largely independent of the detailed properties of the vertex and one which is in very close agreement with experiment. The precise prediction of our theory depends on the energy dependence of the complex phase shift for nucleon-antinucleon scattering in the 1S0 isotopic triplet state

Long-range magnetic fields in the ground state of the Standard Model plasma

In thermal equilibrium the ground state of the plasma of Standard Model particles is determined by temperature and exactly conserved combinations of baryon and lepton numbers. We show that at non-zero values of the global charges a translation invariant and homogeneous state of the plasma becomes unstable and the system transits into a new state, containing a large-scale magnetic field. The origin of this effect is the parity-breaking character of weak interactions and chiral anomaly. This situation can occur in the early Universe and may play an important role in its subsequent evolution.Comment: 6 pages. Comments are welcom