[en] We present the results of a search for the production of light elements in p(bar sign)p collisions at the Fermilab Tevatron collider. Momentum, time of flight, and dE/dx measurements are used to distinguish nuclei from elementary particles. A production ratio for deuterium to hydrogen is calculated and compared to the primordial value of the big bang model. Some evidence for tritium is found and none for helium isotopes. (c) 2000 The American Physical Society

[en] Inclusive dijet production at large pseudorapidity intervals (Δη ) between the two jets has been suggested as a regime for observing Balitsky-Fadin-Kuraev-Lipatov (BFKL) dynamics. We have measured the dijet cross section for large Δη in pp(bar sign) collisions at √(s)=1800 and 630 GeV using the D0 detector. The partonic cross section increases strongly with the size of Δη . The observed growth is even stronger than expected on the basis of BFKL resummation in the leading logarithmic approximation. The growth of the partonic cross section can be accommodated with an effective BFKL intercept of α_BFKL(20 GeV )=1.65±0.07 . (c) 2000 The American Physical Society

[en] The result of a search for gaugino pair production with a trilepton signature is reinterpreted in the framework of minimal supergravity (MSUGRA) with R-parity violation via leptonic λ Yukawa couplings. The search used 95 pb^-1 of pp(bar sign) collisions at √(s)=1.8 TeV recorded by the DOe detector at the Fermilab Tevatron. A large domain of the MSUGRA parameter space is excluded for λ₁₂₁, λ₁₂₂≥10^-4. (c) 2000 The American Physical Society

[en] Events in p(bar sign)p collisions at √(s)=1.8 TeV with total transverse energy exceeding 500 GeV are used to set limits on quark substructure. The data are consistent with next-to-leading order QCD calculations. We set a lower limit of 2.0 TeV at 95% confidence on the energy scale Λ_LL for compositeness in quarks, assuming a model with a left-left isoscalar contact interaction term. The limits on Λ_LL are found to be insensitive to the sign of the interference term in the Lagrangian. (c) 2000 The American Physical Society

[en] The D0 collaboration has performed a study of spin correlation in tt(bar sign) production for the process tt(bar sign)→bW⁺b(bar sign) W^- , where the W bosons decay to eν or μν . A sample of six events was collected during an exposure of the D0 detector to an integrated luminosity of approximately 125 pb^-1 of √(s)=1.8 TeV pp(bar sign) collisions. The standard model (SM) predicts that the short lifetime of the top quark ensures the transmission of any spin information at production to the tt(bar sign) decay products. The degree of spin correlation is characterized by a correlation coefficient κ . We find that κ>-0.25 at the 68% confidence level, in agreement with the SM prediction of κ=0.88 . (c) 2000 The American Physical Society