Detecting Gluino-Containing Hadrons

When SUSY breaking produces only dimension-2 operators, gluino and photino masses are of order 1 GeV or less. The gluon-gluino bound state has mass 1.3-2.2 GeV and lifetime > 10^{-5} - 10^{-10} s. This range of mass and lifetime is largely unconstrained because missing energy and beam dump techniques are ineffective. With only small modifications, upcoming K^0 decay experiments can study most of the interesting range. The lightest gluino-containing baryon (uds-gluino) is long-lived or stable; experiments to find it and the uud-gluino are also discussed.Comment: 13 pp, 1 figure (uuencoded). Descendant of hep-ph/9504295, hep-ph/9508291, and hep-ph/9508292, focused on experimental search techniques. To be published in Phys Rev Let

Dark Matter and the Baryon Asymmetry

We present a mechanism to generate the baryon asymmetry of the Universe which preserves the net baryon number created in the Big Bang. If dark matter particles carry baryon number $B_X$, and $\sigma^{\rm annih}_{\bar{X}} < \sigma^{\rm annih}_{X}$, the $\bar{X}$'s freeze out at a higher temperature and have a larger relic density than $X$'s. If m_X \lsi 4.5 B_X GeV and the annihilation cross sections differ by $\mathcal{O}$(10%) or more, this type of scenario naturally explains the observed $\Omega_{DM} \approx 5 \Omega_b$. Two concrete examples are given, one of which can be excluded on observational grounds

Experiments to Find or Exclude a Long-Lived, Light Gluino

Gluinos in the mass range ~1 1/2 - 3 1/2 GeV are absolutely excluded. Lighter gluinos are allowed, except for certain ranges of lifetime. Only small parts of the mass-lifetime parameter space are excluded for larger masses unless the lifetime is shorter than ~ 2 10^{-11} (m_{gluino}/ GeV) sec. Refined mass and lifetime estimates for R-hadrons are given, present direct and indirect experimental constraints are reviewed, and experiments to find or definitively exclude these possibilities are suggested.Comment: 27 pp, latex with 1 uufiled figure, RU-94-35. New version amplifies discussion of some points and corresponds to version for Phys. Rev.

Possible manifestation of heavy stable colored particles in cosmology and cosmic rays

We discuss the cosmological implications as well as possible observability of massive, stable, colored particles which often appear in the discussion of physics beyond the standard model. We argue that if their masses are more than a few hundred GeV and if they saturate the halo density and/or occur with closure density of the universe, they are ruled out by the present WIMP search experiments as well as the searches for anomalous heavy isotopes of ordinary nuclei. We then comment on the possibility that these particles as well as the monopoles could be responsible for the ultra high energy cosmic rays with energy $\geq 10^{20}$ eV and point out that their low inelasticity argues against this.Comment: 9 pages; UMD-PP-98-1

Recalculation of Proton Compton Scattering in Perturbative QCD

At very high energy and wide angles, Compton scattering on the proton (gamma p -> gamma p) is described by perturbative QCD. The perturbative QCD calculation has been performed several times previously, at leading twist and at leading order in alpha_s, with mutually inconsistent results, even when the same light-cone distribution amplitudes have been employed. We have recalculated the helicity amplitudes for this process, using contour deformations to evaluate the singular integrals over the light-cone momentum fractions. We do not obtain complete agreement with any previous result. Our results are closest to those of the most recent previous computation, differing significantly for just one of the three independent helicity amplitudes, and only for backward scattering angles. We present results for the unpolarized cross section, and for three different polarization asymmetries. We compare the perturbative QCD predictions for these observables with those of the handbag and diquark models. In order to reduce uncertainties associated with alpha_s and the three-quark wave function normalization, we have normalized the Compton cross section using the proton elastic form factor. The theoretical predictions for this ratio are about an order of magnitude below existing experimental data.Comment: Latex, 23 pages, 13 figures. Checked numerical integration one more way; added results for one more proton distribution amplitude; a few other minor changes. Version to appear in Phys. Rev.

Statistical Matrix for Electroweak Baryogenesis

In electroweak baryogenesis, a domain wall between the spontaneously broken and unbroken phases acts as a separator of baryon (or lepton) number, generating a baryon asymmetry in the universe. If the wall is thin relative to plasma mean free paths, one computes baryon current into the broken phase by determining the quantum mechanical transmission of plasma components in the potential of the spatially changing Higgs VEV. We show that baryon current can also be obtained using a statistical density operator. This new formulation of the problem provides a consistent framework for studying the influence of quasiparticle lifetimes on baryon current. We show that when the plasma has no self-interactions, familiar results are reproduced. When plasma self-interactions are included, the baryon current into the broken phase is related to an imaginary time temperature Green's function.Comment: 20 pages, no figures, Late

LIGHT PHOTINOS AS DARK MATTER

There are good reasons to consider models of low-energy supersymmetry with very light photinos and gluinos. In a wide class of models the lightest $R$-odd, color-singlet state containing a gluino, the $\r0$, has a mass in the 1-2 GeV range and the slightly lighter photino, \pho, would survive as the relic $R$-odd species. For the light photino masses considered here, previous calculations resulted in an unacceptable photino relic abundance. But we point out that processes other than photino self-annihilation determine the relic abundance when the photino and $R^0$ are close in mass. Including \r0\longleftrightarrow\pho processes, we find that the photino relic abundance is most sensitive to the $\r0$-to-\pho mass ratio, and within model uncertainties, a critical density in photinos may be obtained for an $\r0$-to-\pho mass ratio in the range 1.2 to 2.2. We propose photinos in the mass range of 500 MeV to 1.6 GeV as a dark matter candidate, and discuss a strategy to test the hypothesis.Comment: uuencoded compressed tar file containing 32 page LaTeX file and eight postscript figure

Interacting Dark Matter and Dark Energy

We discuss models for the cosmological dark sector in which the energy density of a scalar field approximates Einstein's cosmological constant and the scalar field value determines the dark matter particle mass by a Yukawa coupling. A model with one dark matter family can be adjusted so the observational constraints on the cosmological parameters are close to but different from what is predicted by the Lambda CDM model. This may be a useful aid to judging how tightly the cosmological parameters are constrained by the new generation of cosmological tests that depend on the theory of structure formation. In a model with two families of dark matter particles the scalar field may be locked to near zero mass for one family. This can suppress the long-range scalar force in the dark sector and eliminate evolution of the effective cosmological constant and the mass of the nonrelativistic dark matter particles, making the model close to Lambda CDM, until the particle number density becomes low enough to allow the scalar field to evolve. This is a useful example of the possibility for complexity in the dark sector.Comment: 15 pages, 6 figures; added a reference and a minor correctio