arXiv subjects
Publications and source records attributed to David Atwood.
CP violation effects in $e^+ e^- \to t\bar tg$ are examined. CP-odd, $T_n$-odd and $T_n$-even observables can both be used to extract information on the real and imaginary parts of Feynman amplitudes. Two Higgs doublet model with CP violating phase from neutral Higgs exchange is used to estimate possible effects.
Resonance width effects in charged $B$ decays to neutral $D$ mesons and excited kaon states $K_i$ around 1400 MeV are shown to lead to large calculable final state phases. $CP$ asymmetries are defined for any charged $B$ decay to three pseudoscalar mesons involving intermediate overlapping resonance states. Asymmetries up to about 10$\%$ are found in $B^+\to K^+_i D^0\to (Kπ)^+ D^0$. Decay distributions can be used to determine the weak phase $γ$ of the Cabibbo-Kobayashi-Maskawa (CKM) matrix. No separation of the contributions from individual resonances is required.
We explore the influence of an anomalous chromomagnetic moment, $κ$, onthe production characteristics of top quark pairs at the Tevatron. We find that for top quarks in the 170 GeV mass range, present searches are probing values of $κ$ of order ${1 \over 3}$. For $κ$'s in this range we find that significant enhancements in the both the $q \bar q,~gg \to t \bar t$ production cross sections are obtained. Once top has been verified and QCD uncertainties are under control, future high statistics measurements at the Tevatron will eventually be sensitive to values of $κ$ with magnitudes smaller than 0.10-0.15. We discuss a class of scalar technicolor models which may produce large values of $κ$ in conjunction with generation of $m_t$.
In a wide class of models -- including the standard model -- flavor-changing neutral currents are suppressed by an approximate chiral symmetry of the low-energy lagrangian. This symmetry allows the derivation of general relations among low-energy flavour-changing processes. We derive one such: the relative sizes of the decay rates b --> s gamma, b --> d gamma and s --> d gamma. Together with a unitarity-related lower bound on the rate for the strangeness-changing hyperon decay Omega^- --> Xi^- γwe obtain a reasonably model-independent lower bound for the inclusive b --> s gamma rate.