Testing Supergravity Grand Unification at Future Accelerator and Underground Experiments

The full parameter space of supergravity grand unified theory with $SU(5)$ type $p \rightarrow \bar{\nu} K$ proton decay is analysed using renormalization group induced electroweak symmetry breaking under the restrictions that the universal scalar mass $m_o$ and gluino mass are $\leq 1$ TeV (no extreme fine tuning) and the Higgs triplet mass obeys $M_{H_3}/M_G < 10$. Future proton decay experiments at SuperKamiokande or ICARUS can reach a sensitivity for the $\bar{\nu} K$ mode of $(2-5) \times 10^{33}$ yr allowing a number of predictions concerning the SUSY mass spectrum. Thus either the $p \rightarrow\bar{\nu} K$ decay mode will be seen at these experiments or a chargino of mass $m_{\tilde{W}} < 100$ GeV will exist and hence be observable at LEP2. Further, if $(p \rightarrow \bar{\nu} K) > 1.5 \times 10^{33}$ yr, then either the light Higgs has mass $m_h \leq 95$ GeV or $m_{\tilde{W}} \leq 100$ GeV i.e. either the light Higgs or the light chargino (or both) would be observable at LEP2. Thus, the combination of future accelerator and future underground experiments allow for strong experimental tests of this theory.Comment: 7 figures available upon request, CTP-TAMU-32/93, NUB-TH-3066/93 and SSCL-Preprint-44

J1420--0545: The radio galaxy larger than 3C236

We report the discovery of the largest giant radio galaxy, J1420-0545: a FR type II radio source with an angular size of 17.4' identified with an optical galaxy at z=0.3067. Thus, the projected linear size of the radio structure is 4.69 Mpc (if we assume that H_{0}=71 km\s\Mpc, Omega_{m}=0.27, and Omega_{\Lambda}=0.73). This makes it larger than 3C236, which is the largest double radio source known to date. New radio observations with the 100 m Effelsberg telescope and the Giant Metrewave Radio Telescope, as well as optical identification with a host galaxy and its optical spectroscopy with the William Herschel Telescope are reported. The spectrum of J1420-0545 is typical of elliptical galaxies in which continuum emission with the characteristic 4000A discontinuity and the H and K absorption lines are dominated by evolved stars. The dynamical age of the source, its jets' power, the energy density, and the equipartition magnetic field are calculated and compared with the corresponding parameters of other giant and normal-sized radio galaxies from a comparison sample. The source is characterized by the exceptionally low density of the surrounding IGM and an unexpectedly high expansion speed of the source along the jet axis. All of these may suggest a large inhomogeneity of the IGM.Comment: 20 pages, 5 figures, 3 table

Light Neutralinos in B-Decays

We consider the decays of a $B_s$-meson into a pair of lightest supersymmetric particles (LSP) in the minimal supersymmetric standard model. It is found that the parameter space for light LSP's in the range of 1 GeV can be appreciably constrained by looking for such decays.Comment: 9 pages, LaTex, 2 figures (hard copies of the figures available from the Authors on request

Magnetic, Thermal, and Transport Properties of Layered Arsenides BaRu2As2 and SrRu2As2

The magnetic, thermal and transport properties of polycrystalline BaRu2As2 and SrRu2As2 samples with the ThCr2Si2 structure were investigated by means of magnetic susceptibility chi(T), electrical resistivity rho(T), and heat capacity Cp(T) measurements. The temperature (T) dependence of rho indicates metallic character for both compounds with residual resistivity ratios rho(310 K)/rho(2 K) of 17 and 5 for the Ba and Sr compounds, respectively. The Cp(T) results reveal a low-T Sommerfeld coefficient gamma = 4.9(1) and 4.1(1) mJ/mol K^2 and Debye temperature \Theta_D = 271(7) K and 271(4) K for the Ba and Sr compounds, respectively. The chi (T) was found to be diamagnetic with a small absolute value for both compounds. No transitions were found for BaRu2As2 above 1.8 K. The chi(T) data for SrRu2As2 exhibit a cusp at \sim 200 K, possibly an indication of a structural and/or magnetic transition. We discuss the properties of BaRu2As2 and SrRu2As2 in the context of other ThCr2Si2-type and ZrCuSiAs-type transition metal pnictides.Comment: 6 pages, 6 figures; v2: additional discussion of the relationship with FeAs-type materials and the importance of Stoner enhancement of the susceptibilit

Gaugino Mass Nonuniversality and Dark Matter in SUGRA, Strings and D Brane Models

The effects of nonuniversality of gaugino masses on dark matter are examined within supersymmetric grand unification, and in string and D brane models with R parity invariance. In SU(5) unified models nonuniversality in the gaugino sector can be generated via the gauge kinetic energy function which may depend on the 24, 75 and 200 dimensional Higgs representations. We also consider string models which allow for nonuniversality of gaugino masses and D brane models where nonuniversality arises from embeddings of the Standard Model gauge group on five branes and nine branes. It is found that with gaugino mass nonuniversality the range of the LSP mass can be extended much beyond the range allowed in the universal SUGRA case, up to about 600 GeV even without coannihilation effects in some regions of the parameter space. The effects of coannihilation are not considered and inclusion of these effects may further increase the allowed neutralino mass range. Similarly with the inclusion of gaugino mass nonuniversality, the neutralino-proton ($\chi -p$) cross-section can increase by as much as a factor of 10 in some of regions of the parameter space. An analysis of the uncertainties in the quark density content of the nucleon is given and their effects on $\chi -p$ cross-section are discussed. The predictions of our analysis including nonuniversality is compared with the current limits from dark matter detectors and implications for future dark matter searches are discussed.Comment: Revised version, 23 pages, Latex, and 7 figure

SUSY signals at HERA in the no-scale flipped SU(5) supergravity model

Sparticle production and detection at HERA are studied within the recently proposed no-scale flipped $SU(5)$ supergravity model. Among the various reaction channels that could lead to sparticle production at HERA, only the following are within its limit of sensitivity in this model: $e^-p\to \tilde e^-_{L,R}\chi^0_i+X, \tilde \nu_e\chi^-_1+X$, where $\chi^0_i(i=1,2)$ are the two lightest neutralinos and $\chi^-_1$ is the lightest chargino. We study the elastic and deep-inelastic contributions to the cross sections using the Weizs\"acker-Williams approximation. We find that the most promising supersymmetric production channel is right-handed selectron ($\tilde e_{R}$) plus first neutralino ($\chi^0_1$), with one hard electron and missing energy signature. The $\tilde\nu_e\chi^-_1$ channel leads to comparable rates but also allows jet final states. A right-handedly polarized electron beam at HERA would shut off the latter channel and allow preferentially the former one. With an integrated luminosity of {\cal L}=100\ipb, HERA can extend the present LEPI lower bounds on $m_{\tilde e_R}, m_{\tilde\nu_e},m_{\chi^0_1}$ by \approx25\GeV, while {\cal L}=1000\ipb will make HERA competitive with LEPII. We also show that the Leading Proton Spectrometer (LPS) at HERA is an excellent supersymmetry detector which can provide indirect information about the sparticle masses by measuring the leading proton longitudinal momentum distribution.Comment: 11 pages, 8 figures (available upon request as uuencoded file or separate ps files), tex (harvmac) CTP-TAMU-15/93, CERN/LAA/93-1

Dijet Production at Hadron Colliders in Theories with Large Extra Dimensions

We consider the production of high invariant mass jet pairs at hadron colliders as a test for TeV scale gravitational effects. We find that this signal can probe effective Planck masses of about 10 TeV at the LHC with center of mass energy of 14 TeV and 1.5 TeV at the Tevatron with center of mass energy of 2 TeV. These results are compared to analogous scattering processes at leptonic colliders.Comment: 15 pages with 3 figure

R-parity Conservation via the Stueckelberg Mechanism: LHC and Dark Matter Signals

We investigate the connection between the conservation of R-parity in supersymmetry and the Stueckelberg mechanism for the mass generation of the B-L vector gauge boson. It is shown that with universal boundary conditions for soft terms of sfermions in each family at the high scale and with the Stueckelberg mechanism for generating mass for the B-L gauge boson present in the theory, electric charge conservation guarantees the conservation of R-parity in the minimal B-L extended supersymmetric standard model. We also discuss non-minimal extensions. This includes extensions where the gauge symmetries arise with an additional U(1)_{B-L} x U(1)_X, where U(1)_X is a hidden sector gauge group. In this case the presence of the additional U(1)_X allows for a Z' gauge boson mass with B-L interactions to lie in the sub-TeV region overcoming the multi-TeV LEP constraints. The possible tests of the models at colliders and in dark matter experiments are analyzed including signals of a low mass Z' resonance and the production of spin zero bosons and their decays into two photons. In this model two types of dark matter candidates emerge which are Majorana and Dirac particles. Predictions are made for a possible simultaneous observation of new physics events in dark matter experiments and at the LHC.Comment: 38 pages, 7 fig

Flux focusing eddy current probe

A flux-focusing electromagnetic sensor which uses a ferromagnetic flux-focusing lens simplifies inspections and increases detectability of fatigue cracks and material loss in high conductivity material. The unique feature of the device is the ferrous shield isolating a high-turn pick-up coil from an excitation coil. The use of the magnetic shield is shown to produce a null voltage output across the receiving coil in the presence of an unflawed sample. A redistribution of the current flow in the sample caused by the presence of flaws, however, eliminates the shielding condition and a large output voltage is produced, yielding a clear unambiguous flaw signal. The maximum sensor output is obtained when positioned symmetrically above the crack. Hence, by obtaining the position of the maximum sensor output, it is possible to track the fault and locate the area surrounding its tip. The accuracy of tip location is enhanced by two unique features of the sensor; a very high signal-to-noise ratio of the probe's output which results in an extremely smooth signal peak across the fault, and a rapidly decaying sensor output outside a small area surrounding the crack tip which enables the region for searching to be clearly defined. Under low frequency operation, material thinning due to corrosion damage causes an incomplete shielding of the pick-up coil. The low frequency output voltage of the probe is therefore a direct indicator of the thickness of the test sample

Spin correlations and exchange in square lattice frustrated ferromagnets

The J1-J2 model on a square lattice exhibits a rich variety of different forms of magnetic order that depend sensitively on the ratio of exchange constants J2/J1. We use bulk magnetometry and polarized neutron scattering to determine J1 and J2 unambiguously for two materials in a new family of vanadium phosphates, Pb2VO(PO4)2 and SrZnVO(PO4)2, and we find that they have ferromagnetic J1. The ordered moment in the collinear antiferromagnetic ground state is reduced, and the diffuse magnetic scattering is enhanced, as the predicted bond-nematic region of the phase diagram is approached.Comment: 4 pages, 4 figure