Top quark production and flavor physics

Because of the top quark’s very large mass, about 175 GeV, it now provides the best window into flavor physics. Thus, pair–production of top quarks at the Tevatron Collider is the best probe of this physics until the Large Hadron Collider turns on in the next century. I will discuss aspects of the mass and angular distributions that can be measured in tt production with the coming large data samples from the Tevatron and even larger ones from the LHC.Accepted manuscrip

Technicolor

Technicolor, with extended technicolor, is the theory of dynamical electroweak and flavor symmetry breaking at energies far below the Planck scale. To motivate it, I describe the most important difficulties of the standard electroweak model of symmetry breaking by elementary scalar bosons. I then tell how technicolor deals with these difficulties in a way that is both technically and physically natural. Finally, I discuss the problems of technicolor, both past and present.Accepted manuscrip

Color-singlet technipions at the Tevatron

I discuss production and detection at the Tevatron collider of pairs of light (MπT = 100–200GeV) color-singlet technipions that are expected in all nonminimal models of technicolor. Gluon fusion production rates can be as large as O(1 pb). Topcolor-assisted technicolor is required to prevent top quarks from decaying at t → πT^+b. An intriguing consequence of this is that the decays πT^+ → τ+ντ, and may also be suppressed so that πT^+ → W^+γ and πT^0 → γγ are significant. These modes have spectactular signatures at the Tevatron.First author draf

CP violation and mixing in technicolor models

Vacuum alignment in technicolor models provides an attractive origin for the quarks' CP violation and, possibly, a natural solution for the strong-CP problem of QCD. We discuss these topics in this paper. Then we apply them to determine plausible mixing matrices for left and right-handed quarks. These matrices determine the Cabibbo-Kobayashi-Maskawa matrix as well as new mixing angles and phases that are observable in extended technicolor (ETC) and topcolor (TC2) interactions. We determine the contributions of these new interactions to CP-violating and mixing observables in the K0, Bd and Bs systems. Consistency with mixing and CP violation in the K0 system requires assuming that ETC interactions are electroweak generation-conserving even if technicolor has a walking gauge coupling. Large ETC gauge boson masses and small intergenerational mixing then result in negligibly small ETC contributions to B-meson mixing and CP violation and to Re(ϵ′/ϵ). We confirm our earlier strong lower bounds on TC2 gauge boson masses from Bd–¯¯¯Bd mixing. We then pay special attention to the possibility that current experiments indicate a deviation from standard model expectations of the values of sin2β measured in Bd→J/ψKS, ϕKS, η′KS, and πKS, studying the ability of TC2 to account for these. We also determine the TC2 contribution to ΔMBs and to Re(ϵ′/ϵ), and find them to be appreciable.First author draf

Explicit correlation and basis set superposition error: The structure and energy of carbon dioxide dimer

We have investigated the slipped parallel and t-shaped structures of carbon dioxide dimer [(CO₂)₂] using both conventional and explicitly correlated coupled cluster methods, inclusive and exclusive of counterpoise (CP) correction. We have determined the geometry of both structures with conventional coupled cluster singles doubles and perturbative triples theory [CCSD(T)] and explicitly correlated cluster singles doubles and perturbative triples theory [CCSD(T)-F12b] at the complete basis set (CBS) limits using custom optimization routines. Consistent with previous investigations, we find that the slipped parallel structure corresponds to the global minimum and is 1.09 kJ mol⁻¹ lower in energy. For a given cardinal number, the optimized geometries and interaction energies of (CO₂)₂ obtained with the explicitly correlated CCSD(T)-F12b method are closer to the CBS limit than the corresponding conventional CCSD(T) results. Furthermore, the magnitude of basis set superposition error (BSSE) in the CCSD(T)-F12b optimized geometries and interaction energies is appreciably smaller than the magnitude of BSSE in the conventional CCSD(T) results. We decompose the CCSD(T) and CCSD(T)-F12b interaction energies into the constituent HF or HF CABS, CCSD or CCSD-F12b, and (T) contributions. We find that the complementary auxiliary basis set (CABS) singles correction and the F12b approximation significantly reduce the magnitude of BSSE at the HF and CCSD levels of theory, respectively. For a given cardinal number, we find that non-CP corrected, unscaled triples CCSD(T)-F12b/VXZ-F12 interaction energies are in overall best agreement with the CBS limit

Relating Noncommutative SO(2,3) Gravity to the Lorentz-Violating Standard-Model Extension

We consider a model of noncommutative gravity that is based on a spacetime with broken local SO(2,3) symmetry. We show that the torsion-free version of this model is contained within the framework of the Lorentz-violating Standard-Model Extension. We analyze in detail the relation between the torsion-free, quadratic limits of the broken SO(2,3) model and the Standard-Model Extension. As part of the analysis,we construct the relevant geometric quantities to quadratic order in the metric perturbation around a flat background.Comment: 10 pages, accepted in Symmetr