Physics at e-e- Colliders

An overview of the physics motivations for e-e- colliders is presented.Comment: 10 pages. Opening lecture of the 3nd International Workshop on Electron-Electron Interactions at TeV Energies (e-e-99), University of California, Santa Cruz, 10-12 December 199

Consequences of a Possible Di-Gamma Resonace at TRISTAN

If high mass di-gamma events observed at LEP are due to the production of a di-gamma resonance via its leptonic coupling, its consequences can be observed at TRISTAN. We find that a predicted $Z$ decay branching rate is too small to account for the observed events if the resonance spin is zero, due to a strong cancellation in the decay amplitudes. Such a cancellation is absent if the resonance has a spin two. We study the consequences of a tensor production in the processes $e^+e^- \to e^+e^-$, $\mu^+\mu^-$ and $\gamma\,\gamma$ at TRISTAN energies. Complete helicity amplitudes with tensor boson exchange contributions are given, and the signal can clearly be identified from various distributions. TRISTAN experiments are also sensitive to the virtual tensor boson exchange effects, which reduce to the contact interaction terms in the high mass limit.Comment: 23 pages in revtex, 7 figures (not included) available upon request, KEK-TH-35

Annihilation Diagrams in Two-Body Nonleptonic Decays of Charmed Mesons

In the pole-dominance model for the two-body nonleptonic decays of charmed mesons $D \rightarrow PV$ and $D \rightarrow VV$, it is shown that the contributions of the intermediate pseudoscalar and the axial-vector meson poles cancel each other in the annihilation diagrams in the chiral limit. In the same limit, the annihilation diagrams for the $D \rightarrow PP$ decays vanish independently.Comment: 9 pages (+ 3 figures available upon request), UR-1316, ER-40685-766, IC/93/21

Single scalar top production with polarized beams in ep collisions at HERA

From the point of view of the R-parity breaking supersymmetric model, we propose a scalar top (stop) search with longitudinally polarized electron (e-) and positron(e+) beams which will soon be available at the upgraded HERA. Fully polarized e- or e+ beams could produce the stop two times as much as unpolarized beams, while they increase background events due to the process of the standard model by about 30% in comparison with unpolarized ones. We show that right-handed e+ beams at HERA is efficient to produce the stop in the model. With 1 fb**(-1) of integrated luminosity we estimate reach in the coupling constant lambda'(131) for masses of the stop in the range 160-400 GeV. We can set a 95% confidence-level exclusion limit for lambda'(131) > 0.01-0.05 in the stop mass range of 240-280 GeV if no singal of the stop is observed. We also point out that y(=Q**2/sx) distributions of e+ coming from the stop shows the different behavior from those of the standard model.Comment: 12 pages, 6 eps figure

Decay of the Z Boson into Scalar Particles

In extensions of the standard model, light scalar particles are often possible because of symmetry considerations. We study the decay of the Z boson into such particles. In particular, we consider for illustration the scalar sector of a recently proposed model of the 17-keV neutrino which satisfies all laboratory, astrophysical, and cosmological constraints.Comment: 11 pages (2 figures, not included) (Revised, Oct 1992). Some equations have been corrected and 1 figure has been eliminate

Ultra-high energy cosmic rays may come from clustered sources

Clustering of cosmic-ray sources affects the flux observed beyond the cutoff imposed by the cosmic microwave background and may be important in interpreting the AGASA, Fly's Eye, and HiRes data. The standard deviation, sigma, in the predicted number, N, of events above 10^{20} eV is sigma/N = 0.9(r_0/10 Mpc)^{0.9}, where r_0 is the unknown scale length of the correlation function (r_0 = 10 Mpc for field galaxies). Future experiments will allow the determination of r_0 through the detection of anisotropies in arrival directions of ~ 10^{20} eV cosmic-rays over angular scales of Theta ~ r_0/30 Mpc.Comment: Accepted for publication in Astrophysical Journa

Spectroscopy of doubly charmed baryons: Ξcc+\Xi_{cc}^{+} and Ξcc++\Xi_{cc}^{++}

Using the quark-diquark approximation in the framework of Buchm\" uller-Tye potential model, we investigate the spectroscopy of doubly charmed baryons: $\Xi_{cc}^{++}$ and $\Xi_{cc}^{+}$. Our results include the masses, parameters of radial wave functions of states with the different excitations of both diquark and light quark-diquark system. We calculate the values of fine and hyperfine splittings of these levels and discuss some new features, connected to the identity of heavy quarks, in the dynamics of hadronic and radiative transitions between the states of these baryons.Comment: 10 pages, Latex file, 1 fig, corrected some typo

Cosmological Origin for Cosmic Rays Above 101910^{19} eV

The cosmic ray spectrum at $10^{19}{\rm eV}-10^{20}{\rm eV}$, reported by the Fly's Eye and the AGASA experiments, is shown to be consistent with a cosmological distribution of sources of protons, with a power law generation spectrum ${\rm d}\ln N/{\rm d}\ln E=-2.3\pm0.5$ and energy production rate of $4.5\pm1.5\times10^{44}{\rm erg}\ {\rm Mpc}^{-3}\ {\rm yr}^{-1}$. The two events measured above $10^{20}{\rm eV}$ are not inconsistent with this model. Verifying the existence of a ``black-body cutoff'', currently observed with low significance, would require $\sim30$ observation-years with existing experiments, but only $\sim1$ year with the proposed $\sim5000\ {\rm km}^2$ detectors. For a cosmological source distribution, no anisotropy is expected in the angular distribution of events with energies up to $\sim5\times10^{19}{\rm eV}$.Comment: uuencoded gz-compressed postscript file, including 2 figures; To appear in the October 10 (1995) issue of the Ap. J. Letter