Fermi Space Telescope highlights

The Fermi Space Mission has had a remarkable first two years of operation in low-Earth orbit, collecting over 380 million events, and revealing unprecedented details of the gamma-ray sky. The Large Area Telescope (LAT) has lived up to expectations. Being the first all-sky monitor in almost real time has revealed a wealth of transient phenomena. Some highlights of the discoveries made by the Fermi-LAT in the past two years are presented. Possible future directions for this highly successful mission will be discussed

CP Nonconservation in e+e−→ttˉge^+e^-\to t\bar tg

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.Comment: 9 pages, 4 Figures, Late

CP Nonconservation in ppˉ→tbˉXp\bar p\to t\bar b X at the Tevatron

The reaction $p\bar p\to t\bar bX$ is found to be rather rich in exhibiting several different types of CP asymmetries. The spin of the top quark plays an important role. Asymmetries are related to form factors arising from radiative corrections of the $tbW$ production vertex due to non-standard physics. As illustrations, effects are studied in two Higgs Doublet Models and in Supersymmetric Models; asymmetries up to a few percent may be possible.Comment: 14 pages, 3 figures. Note: replaced due to minor problems that appeared on some postscript previewers. No change in conten

Determining the top-antitop and ZZZZ Couplings of a Neutral Higgs Boson of Arbitrary CP Nature at the NLC

The optimal procedure for extracting the coefficients of different components of a cross section which takes the form of unknown coefficients times functions of known kinematical form is developed. When applied to \epem\to t\anti t+Higgs production at \rts=1\tev and integrated luminosity of 200\fbi, we find that the t\anti t\toHiggs CP-even and CP-odd couplings and, to a lesser extent, the $ZZ\to$Higgs (CP-even) coupling can be extracted with reasonable errors, assuming the Higgs sector parameter choices yield a significant production rate. Indeed, the composition of a mixed-CP Higgs eigenstate can be determined with sufficient accuracy that a SM-like CP-even Higgs boson can be distinguished from a purely CP-odd Higgs boson at a high level of statistical significance, and vice versa.Comment: 8 pages, full postscript file also available via anonymous ftp at ftp://ucdhep.ucdavis.edu/gunion/eetottbh.p

Polarized Single Top Production at Leptonic Colliders from Broken R Parity Interactions Incorporating CP Violation

The contribution from the R parity violating interactions in the associated production of a top quark with a charm antiquark is examined for high energy leptonic colliders. We concentrate on the reactions associated with the semileptonic top decay. A set of characteristic dynamical distributions for the signal events is evaluated and the results contrasted against those from the standard model W-boson pair production background. Next, we turn to a study of a CP-odd observable, associated with the top spin, which leads to an asymmetry in the energy distribution of the emitted charged leptons for the pair of CP-conjugate final states, $b \bar l \nu \bar c$ and $\bar b l \bar \nu c$. A non vanishing asymmetry arises from a CP-odd phase, embedded in the R parity violating coupling constants, through interference terms between the R parity violating amplitudes at both the tree and loop levels.Comment: revtex file. 17 pages. 7 postscript figures. 1 table. The revised version includes an estimate of experimental uncertainties. Submitted to Phys. Rev.

Search for anomalous top-gluon couplings at LHC revisited

Through top-quark pair productions at LHC, we study possible effects of nonstandard top-gluon couplings yielded by SU(3)xSU(2)xU(1) invariant dimension-6 effective operators. We calculate the total cross section and also some distributions for p p -> t tbar X as functions of two anomalous-coupling parameters, i.e., the chromoelectric and chromomagnetic moments of the top, which are constrained by the total cross section sigma(p pbar -> t tbar X) measured at Tevatron. We find that LHC might give us some chances to observe sizable effects induced by those new couplings.Comment: One comment and related two refs. added. Final version (to appear in Eur.Phys.J. C

Weak dipole moment of τ\tau in e+e−e^+e^- collisions with longitudinally polarized electrons

It is pointed out that certain CP-odd momentum correlations in the production and subsequent decay of tau pairs in $e^+e^-$ collisions get enhanced when the $e^-$ is longitudinally polarized. Analytic expressions for these correlations are obtained for the single-pion decay mode of $\tau$ when $\tau^+\tau^-$ have a ``weak" dipole form factor (WDFF) coupling to $Z$ . For $e^+e^-$ collisions at the $Z$ peak, a sensitivity of about 1-5$\times 10^{-17}$\mbox{$e$ cm} for the $\tau$ WDFF can be reached using a {\em single} $\tau^+\tau^-$ decay channel, with $10^6\, Z$'s likely to be available at the SLC at Stanford with $e^-$ polarization of 62\%-75\%.Comment: 9 pages, Latex, PRL-TH-93/17 (Revised

Large Tree Level CP Violation in e+e−→ttˉH0e^+e^-\to t\bar{t}H^0 in The Two Higgs Doublet Model

We find a large CP violation effect within the Two-Higgs-Doublet-Model for the reaction $e^+e^-\to t\bar{t}H^0$ at future linear colliders. The CP-asymmetry arises already at the tree level as a result of interference between diagrams with $H^0$ emission from $t$ (and $\bar{t}$) and its emission from a $Z^0$ and can be about 10--20\%. In the best case one needs a few hundred $t\bar{t}H^0$ events to observe CP violation at the 3$\sigma$ level.Comment: UU encoded tar compressed tex file with postscript figure