Spin Alignment of Heavy Meson Revisited

Using heavy quark effective theory a factorized form for inclusive production rate of a heavy meson can be obtained, in which the nonperturbative effect related to the heavy meson can be characterized by matrix elements defined in the heavy quark effective theory. Using this factorization, predictions for the full spin density matrix of a spin-1 and spin-2 meson can be obtained and they are characterized only by one coefficient representing the nonperturbative effect. Predictions for spin-1 heavy meson are compared with experiment performed at $e^+e^-$ colliders in the energy range from $\sqrt{s}=10.5$GeV to $\sqrt{s}=91$GeV, a complete agreement is found for $D^*$- and $B^*$-meson. There are distinct differences from the existing approach and they are discussed.Comment: 6 pages, Talk given at 3rd Circum-Pan-Pacific Symposium on "High Energy Spin Physics", Beijing, China, 8-13, 200

Non-zero transversity distribution of the pion in a quark-spectator-antiquark model

We calculate the non-zero (na\"{i}ve) T-odd transverse momentum dependent transversity distribution h_1^{\perp}(x,\kp^2) of the pion in a quark-spectator-antiquark model. The final-state interaction is modelled by the approximation of one gluon exchange between the quark and the antiquark spectator. Using our model result we estimate the unsuppressed cos2$\phi$ azimuthal asymmetry in unpolarized $\pi^-p$ Drell-Yan process. We find that the transverse momentum dependence of h_1^{\perp}(x,\kp^2) of the pion is the same as that of h_1^{\perp}(x,\kp^2) of the proton calculated from the quark-scalar-diquark model, although the $x$ dependencies of them are different from each other. This suggests a connection between cos2$\phi$ asymmetries in Drell-Yan processes with different initial hadrons.Comment: 6 LaTex Pages in Revtex format, 5 figures. Version to appear in PR

Azimuthal asymmetry in unpolarized πN\pi N Drell-Yan process

Taking into account the effect of final state interaction, we calculate the non-zero (na\"{i}ve) $T$-odd transverse momentum dependent distribution h_1^{\perp}(x,\kp^2) of the pion in a quark-spectator-antiquark model with effective pion-quark-antiquark coupling as a dipole form factor. Using the model result we estimate the $\cos 2\phi$ asymmetries in the unpolarized $\pi^- N$ Drell-Yan process which can be expressed as $h_1^{\perp}\times\bar{h}_1^{\perp}$. We find that the resulting h_{1\pi}^\p(x,\kp^2) has the advantage to reproduce the asymmetry that agrees with the experimental data measured by NA10 Collaboration. We estimate the $\cos2\phi$ asymmetries averaged over the kinematics of NA10 experiments for 140, 194 and 286 GeV $\pi^-$ beam and compare them with relevant experimental data.Comment: 11 pages, 4 figures, to appear in PL

Revisiting spin alignment of heavy mesons in its inclusive production

In the heavy quark limit inclusive production rate of a heavy meson can be factorized, in which the nonperturbative effect related to the heavy meson can be characterized by matrix elements defined in the heavy quark effective theory. Using this factorization, predictions for the full spin density matrix of a spin-1 and spin-2 meson can be obtained and they are characterized only by one coefficient representing the nonperturbative effect. Predictions for spin-1 heavy meson are compared with experiment performed at $e^+e^-$ colliders in the energy range from $\sqrt{s}=10.5$GeV to $\sqrt{s}=91$GeV, a complete agreement is found for $D^*$- and $B^*$-meson. For $D^{**}$ meson, our prediction suffers a large correction, as indicated by experimental data. There exists another approach by taking heavy mesons as bound systems, in which the total angular momentum of the light degrees of freedom is 1/2 and 3/2 for spin-1 and spin-2 meson respectively, then the diagonal parts of spin density matrices can be obtained. However, there are distinct differences in the predictions from the two approaches and they are discussed in detail.Comment: 14 pages with one figur

Gauge invariance, causality and gluonic poles

We explore the electromagnetic gauge invariance of the hadron tensor of the Drell-Yan process with one transversely polarized hadron. The special role is played by the contour gauge for gluon fields. The prescription for the gluonic pole in the twist 3 correlator is related to causality property and compared with the prescriptions for exclusive hard processes. As a result of we get the extra contributions, which naively do not have an imaginary phase. The single spin asymmetry for the Drell-Yan process is enhanced by the factor of two.Comment: 9 pages, 2 figures; References and acknowledgements added

Could Large CP Violation Be Detected at Colliders?

We argue that CP--violation effects below a few tenths of a percent are probably undetectable at hadron and electron colliders. Thus only operators whose contributions interfere with tree--level Standard Model amplitudes are detectable. We list these operators for Standard Model external particles and some two and three body final state reactions that could show detectable effects. These could test electroweak baryogenesis scenarios.Comment: 11pp, LaTeX, UM--TH--92--27(massaged to make TeX output cleaner), no picture

Compact Drawings of 1-Planar Graphs with Right-Angle Crossings and Few Bends

We study the following classes of beyond-planar graphs: 1-planar, IC-planar, and NIC-planar graphs. These are the graphs that admit a 1-planar, IC-planar, and NIC-planar drawing, respectively. A drawing of a graph is 1-planar if every edge is crossed at most once. A 1-planar drawing is IC-planar if no two pairs of crossing edges share a vertex. A 1-planar drawing is NIC-planar if no two pairs of crossing edges share two vertices. We study the relations of these beyond-planar graph classes (beyond-planar graphs is a collective term for the primary attempts to generalize the planar graphs) to right-angle crossing (RAC) graphs that admit compact drawings on the grid with few bends. We present four drawing algorithms that preserve the given embeddings. First, we show that every $n$-vertex NIC-planar graph admits a NIC-planar RAC drawing with at most one bend per edge on a grid of size $O(n) \times O(n)$. Then, we show that every $n$-vertex 1-planar graph admits a 1-planar RAC drawing with at most two bends per edge on a grid of size $O(n^3) \times O(n^3)$. Finally, we make two known algorithms embedding-preserving; for drawing 1-planar RAC graphs with at most one bend per edge and for drawing IC-planar RAC graphs straight-line

CP Violation in γγ→t tˉ\gamma \gamma \to t~\bar{t} within the Minimal Supersymmetric Standard Model

The complete analysis of the CP violation in the process $\gamma \gamma \to t \bar{t}$ in frame of the Minimal Supersymmetric Model(MSSM) is presented. The CP-odd observables for describing the CP violating effects in polarized and unpolarized photon collisions, are calculated. We investigate the possible CP violation sources induced by the complex soft breaking parameters and study the CP violating effects contributed by gluino, neutralino and chargino sectors appearing in the loop diagrams. We find that it is possible to observe the CP violation effects in top quark pair production via polarized and unpolarized photon fusions by using optimal observables and favorable parameters.Comment: 15 pages, LaTex, including 14 figures in eps file

CP-Violatiing Asymmetries in e^+e^-\ra t\bar{t} with Longitudinally Polarized Elecrtons

New CP-violating asymmetries of decay leptons in e^+\,e^-\;\ra\;t\,\bar{t}, arising from electric and weak dipole couplings of $t\,\bar{t}$ to $\gamma$ and $Z$, are examined in the case of unpolarized and longitudinally polarized electrons. The new asymmetries measured together with the old ones can help to determine independently the real and imaginary parts of the electric as well as weak dipole couplings. Longitudinal beam polarization, if present, obviates the need for the simultaneous measurement of more than one asymmetry, and enhances considerably the sensitivity to the CP-violating parameters. Numerical results are presented for the Next Linear Collider with $\sqrt{s}=500$ GeV and $\int{\cal L}\,dt\;=\;10\,{\rm fb}^{-1}$.Comment: 12 pages LaTex,PRL-TH-94/3

CP-violating asymmetries in top-quark production and decay in e+e−e^+ e^- annihilation within the MSSM

We obtain analytic formulae for the cross section of the sequential processes of $e^+ e^- \to t \bar t$ and $t \to b l \nu$ in the laboratory frame where the dependence on triple product correlations of the type (\hat(q}_1 x \hat{q}_2 . \hat{q}_3), induced by CP violation both in the production and the decay are explicitely shown. Different observables sensitive to CP violation are defined and calculated in the Minimal Supersymmetric Standard Model (MSSM). The observables sensitive to CP violation are of the order of $10^-3$. The dependence on the masses of the supersymmetric particles is also shown.Comment: 17 pages of LateX plus five uuencoded Postscript figures, LateX file and PS-figures are also available via anonymous ftp at ftp://info.oeaw.ac.at/pub/hephy-pub/62