[en] Measurements of the cosmic-ray p/p ratio are compared with predictions from an inhomogeneous disk-diffusion model of p production and propagation within the Galaxy, combined with a calculation of the modulation of the interstellar cosmic-ray spectra as the particles propagate through the heliosphere to the Earth. The predictions agree with the observed p/p spectrum. Adding a finite p lifetime to the model, we obtain the limit τ_p>0.8 Myr (90% CL). (c) 2000 The American Astronomical Society

[en] In supersymmetric theories of nature the Higgsino fermionic superpartner of the Higgs boson can arise as the lightest standard model superpartner depending on the couplings between the Higgs and supersymmetry breaking sectors. In this Brief Report the production and decay of Higgsino pairs to the Goldstone fermion of supersymmetry breaking and the Higgs boson h, or gauge bosons Z or γ are considered. Relatively clean diboson final states hh, hγ, hZ, Zγ, or ZZ with a large amount of missing energy result. The latter channels provide novel discovery modes for supersymmetry at high energy colliders since events with Z bosons are generally rejected in supersymmetry searches. In addition, final states with real Higgs bosons can potentially provide efficient channels to discover and study a Higgs signal at the Fermilab Tevatron run II. (c) 2000 The American Physical Society

[en] We have studied the ''wrong-sign'' process D⁰→K⁺π^- to search for D⁰-D⁰ mixing. The data come from 9.0 fb^-1 of e⁺e^- collisions at √(s)≅10 GeV recorded with the CLEO II.V detector. We measure the relative rate of the wrong-sign process D⁰→K⁺π^- to the Cabibbo-favored process D⁰→K⁺π^- to be R=(0.332^+0.063_-0.065±0.040 )% . We study D⁰→K⁺π^- as a function of decay time to distinguish direct doubly Cabibbo-suppressed decay from D⁰-D⁰ mixing. The amplitudes that describe D⁰-D⁰ mixing, x^' and y^' , are consistent with zero. At the 95% C.L. and without assumptions concerning charge-parity (CP ) violating parameters, we find (1/2)x^'2<0.041% and -5.8%< y^'<1.0% . (c) 2000 The American Physical Society

[en] Simultaneous nonlinear realizations of supersymmetry and softly broken scale and chiral symmetries are investigated. To guarantee Nambu-Goldstone realizations of the symmetries, the Goldstino decay constant is forced to vary as the explicit soft scale and chiral symmetry breaking parameters. Consequently, it must vanish in the chiral limit and the simultaneous nonlinear realizations of the super and scale symmetries prove inconsistent. (c) 2000 The American Physical Society

[en] The radiative decay of the next-to-lightest neutralino into a lightest neutralino and a photon is analyzed in the minimal supersymmetric standard model. We find that significant regions of the supersymmetric parameter space with large radiative branching ratios (up to about 100%) do exist. The radiative channel turns out to be enhanced when the neutralino tree-level decays are suppressed either open-quotes kinematically close-quote close-quote or open-quotes dynamically.close-quote close-quote In general, in the regions allowed by data from CERN LEP and not characterized by asymptotic values of the supersymmetric parameters, the radiative enhancement requires tanβ≅1 and/or M₁≅M₂, and negative values of μ. We present typical scenarios where these conditions are satisfied, relaxing the usual relation M₁=(5)/(3)tan²θ_WM₂, i.e., gaugino mass unification at the grand unified theory scale. The influence of varying the top-squark masses and mixing angle when the radiative decay is enhanced is also considered. Some phenomenological consequences of the above picture are discussed. copyright 1997 The American Physical Society

[en] Within the minimal supersymmetric standard model we study the three body decay of the lighter top squark t₁→bWχ₁⁰ and compare this decay with the flavor-changing two body decay t₁→cχ₁⁰. Here χ₁⁰ is the lightest neutralino which we assume to be the lightest supersymmetric particle. We do this for scenarios where two body decays at the tree level are forbidden for the light top squark. We give the complete analysis for the three body decay and compare it with the mentioned two body decay. We discuss our numerical results in view of the upgraded Fermilab Tevatron, the CERN LHC, and a 500 GeV e⁺e^- Linear Collider. copyright 1997 The American Physical Society

[en] Previously, in the context of the minimal supersymmetric standard model (without a priori assumptions of parameter unification), we studied the constraints on weak-scale SUSY parameters from chargino production at CERN LEP II, using as observables m_χ1^±,m_χ1⁰, the cross section and the leptonic branching fraction. Here, exploiting the high degree of polarization in chargino production, we add to our earlier work the forward-backward asymmetries of the visible hadrons and leptons in chargino decays. For a chargino that is mostly gaugino, the parameter space can now be restricted to a small region; tanβ is constrained, the soft electroweak gaugino and electron sneutrino masses are determined to about 10%, and the sign of μ may be determined. Constraints for a chargino that is mostly Higgsino are much weaker, but still disfavor the hypothesis that the chargino is mostly gaugino. For a chargino which is a roughly equal mixture of Higgsino and gaugino, we find intermediate results. copyright 1997 The American Physical Society

[en] Searches for pair-production of supersymmetric particles under the assumption that R-parity is violated via a single dominant LL anti E,LQ anti D or anti U anti D anti D coupling are performed using the data collected by the ALEPH collaboration at centre-of-mass energies of 181-184 GeV. The observed candidate events in the data are in agreement with the standard model expectations. Upper limits on the production cross-sections and lower limits on the masses of charginos, sleptons, squarks and sneutrinos are derived. (orig.)

[en] We study the production process e⁺e^- → χ₁⁰χ₂⁰ and the subsequent decay χ₂⁰ → χ₁⁰l⁺l^- with polarized e⁺ and e^- beams, including the spin correlations between production and decay. We work out the advantages of polarizing both beams. We study in detail the angular distribution and the forward-backward asymmetry of the decay lepton as well as the opening angle distribution between the decay leptons. We investigate the dependence on the masses of e_L and eR and on the mixing character of the neutralinos. In particular we study the dependence on the gaugino mass parameter M₁. (orig.)

[en] The status of two on-going studies concerning important aspects of the phenomenology of gauge-mediated supersymmetry breaking (GMSB) models at TeV colliders is reported. The first study deals with the characteristics of the light Higgs boson spectrum allowed by the (minimal and non-minimal) GMSB framework. Today's most accurate GMSB model generation and two-loop Feynman-diagrammatic calculation of m_h have been combined. The Higgs masses are shown in dependence of various model parameters at the messenger and electroweak scales. In the minimal model, an upper limit on m_h of about 124 GeV is found for m_t=175 GeV. The second study is focused on the measurement of the fundamental SUSY breaking scale √(F) at the LHC in the GMSB scenario where a stau is the next-to-lightest SUSY particle (NLSP) and decays into a gravitino with cτ_NLSP in the range 0.5 m to 1 km. This implies the measurement of mass and lifetime of long lived sleptons. The identification is performed by determining the time of flight in the ATLAS muon chambers. Accessible range and precision on √(F) achievable with a counting method are assessed. (orig.)