8,722 research outputs found

    LHC Reach for Gauge Mediated Supersymmetry Breaking Models Via Prompt Photon Channels

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    We evaluate the supersymmetry reach of the Large Hadron Collider within the gauge-mediated low energy supersymmetry breaking framework, assuming that a neutralino is the second lightest sparticle and that it decays promptly into a gravitino which escapes detection. We find that the maximum reach is obtained via a search for inclusive \gamma\gamma+\eslt events coming dominantly from chargino and neutralino production. Assuming an integrated luminosity of 10~fb1fb^{-1}, we find that LHC experiments will be able to probe values of the model parameter \Lambda \alt 400 TeV, corresponding to mtg2.8m_{\tg} \leq 2.8 TeV. A measure of the model parameter Λ\Lambda may be possible from the photon pTp_T spectrum.Comment: 10 page Revtex file plus 4 EPS figure

    Trileptons from Chargino-Neutralino Production at the CERN Large Hadron Collider

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    We study direct production of charginos and neutralinos at the CERN Large Hadron Collider. We simulate all channels of chargino and neutralino production using ISAJET 7.07. The best mode for observing such processes appears to be pp\to\tw_1\tz_2\to 3\ell +\eslt. We evaluate signal expectations and background levels, and suggest cuts to optimize the signal. The trilepton mode should be viable provided m_{\tg}\alt 500-600~GeV; above this mass, the decay modes \tz_2\to\tz_1 Z and \tz_2\to H_{\ell}\tz_1 become dominant, spoiling the signal. In the first case, the leptonic branching fraction for ZZ decay is small and additional background from WZWZ is present, while in the second case, the trilepton signal is essentially absent. For smaller values of mtgm_{\tg}, the trilepton signal should be visible above background, especially if μmtg|\mu|\simeq m_{\tg} and m_{\tell}\ll m_{\tq}, in which case the leptonic decays of \tz_2 are enhanced. Distributions in dilepton mass m(ˉ)m(\ell\bar{\ell}) can yield direct information on neutralino masses due to the distribution cutoff at m_{\tz_2}-m_{\tz_1}. Other distributions that may lead to an additional constraint amongst the chargino and neutralino masses are also examined.Comment: preprint nos. FSU-HEP-940310 and UH-511-786-94, 13 pages (REVTEX) plus 7 uuencoded figures attache

    Hidden SUSY at the LHC: the light higgsino-world scenario and the role of a lepton collider

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    While the SUSY flavor, CP and gravitino problems seem to favor a very heavy spectrum of matter scalars, fine-tuning in the electroweak sector prefers low values of superpotential mass \mu. In the limit of low \mu, the two lightest neutralinos and light chargino are higgsino-like. The light charginos and neutralinos may have large production cross sections at LHC, but since they are nearly mass degenerate, there is only small energy release in three-body sparticle decays. Possible dilepton and trilepton signatures are difficult to observe after mild cuts due to the very soft p_T spectrum of the final state isolated leptons. Thus, the higgsino-world scenario can easily elude standard SUSY searches at the LHC. It should motivate experimental searches to focus on dimuon and trimuon production at the very lowest p_T(\mu) values possible. If the neutralino relic abundance is enhanced via non-standard cosmological dark matter production, then there exist excellent prospects for direct or indirect detection of higgsino-like WIMPs. While the higgsino-world scenario may easily hide from LHC SUSY searches, a linear e^+e^- collider or a muon collider operating in the \sqrt{s}\sim 0.5-1 TeV range would be able to easily access the chargino and neutralino pair production reactions.Comment: 20 pages including 12 .eps figure

    Testing the gaugino AMSB model at the Tevatron via slepton pair production

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    Gaugino AMSB models-- wherein scalar and trilinear soft SUSY breaking terms are suppressed at the GUT scale while gaugino masses adopt the AMSB form-- yield a characteristic SUSY particle mass spectrum with light sleptons along with a nearly degenerate wino-like lightest neutralino and quasi-stable chargino. The left- sleptons and sneutrinos can be pair produced at sufficiently high rates to yield observable signals at the Fermilab Tevatron. We calculate the rate for isolated single and dilepton plus missing energy signals, along with the presence of one or two highly ionizing chargino tracks. We find that Tevatron experiments should be able to probe gravitino masses into the ~55 TeV range for inoAMSB models, which corresponds to a reach in gluino mass of over 1100 GeV.Comment: 14 pages including 6 .eps figure

    Reach of the Fermilab Tevatron for minimal supergravity in the region of large scalar masses

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    The reach of the Fermilab Tevatron for supersymmetric matter has been calculated in the framework of the minimal supergravity model in the clean trilepton channel. Previous analyses of this channel were restricted to scalar masses m_0<= 1 TeV. We extend the analysis to large values of scalar masses m_0\sim 3.5 TeV. This includes the compelling hyperbolic branch/focus point (HB/FP) region, where the superpotential \mu parameter becomes small. In this region, assuming a 5\sigma (3\sigma) signal with 10 (25) fb^{-1} of integrated luminosity, the Tevatron reach in the trilepton channel extends up to m_{1/2}\sim 190 (270) GeV independent of \tan\beta . This corresponds to a reach in terms of the gluino mass of m_{\tg}\sim 575 (750) GeV.Comment: 11 page latex file including 6 EPS figures; several typos corrected and references adde

    Adoption of E-Marketing by Direct-Market Farms in the Northeastern United States

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    Many farms have begun operating websites in order to promote their businesses. This study uses data from a 2005 survey of farms in the northeastern United States to identify characteristics of farmers, farms, and farm businesses associated with website adoption. Following a technology-adoption framework, a probit model of website use is estimated to identify significant relationships. Sales location, product type, number of advertising methods used, high-speed Internet connection, land tenure arrangement, and gross farm sales is found to be significantly related to website adoption.Marketing,

    SUPERSYMMETRY REACH OF AN UPGRADED TEVATRON COLLIDER

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    We examine the capability of a s=2\sqrt{s}=2 TeV Tevatron ppˉp\bar p collider to discover supersymmetry, given a luminosity upgrade to amass 25 fb125\ fb^{-1} of data. We compare with the corresponding reach of the Tevatron Main Injector (1 fb11\ fb^{-1} of data). Working within the framework of minimal supergravity with gauge coupling unification and radiative electroweak symmetry breaking, we first calculate the regions of parameter space accessible via the clean trilepton signal from \tw_1\tz_2\to 3\ell +\eslt production, with detailed event generation of both signal and major physics backgrounds. The trilepton signal can allow equivalent gluino masses of up to mtg600700m_{\tg}\sim 600-700 GeV to be probed if m0m_0 is small. If m0m_0 is large, then mtg500m_{\tg}\sim 500 GeV can be probed for μ0\mu 0 and large values of m0m_0, the rate for \tz_2\to\tz_1\ell\bar{\ell} is suppressed by interference effects, and there is {\it no} reach in this channel. We also examine regions where the signal from \tw_1\overline{\tw_1}\to \ell\bar{\ell}+\eslt is detectable. Although this signal is background limited, it is observable in some regions where the clean trilepton signal is too small. Finally, the signal \tw_1\tz_2\to jets+\ell\bar{\ell} +\eslt can confirm the clean trilepton signal in a substantial subset of the parameter space where the trilepton signal can be seen. We note that although the clean trilepton signal may allow Tevatron experiments to identify signals in regions of parameter space beyond the reach of LEP II, the dilepton channels generally probe much the same region as LEP II.Comment: 19 page REVTEX file; a uuencoded PS file with PS figures is available via anonymous ftp at ftp://hep.fsu.edu/preprints/baer/FSUHEP950301.u

    Argentina's default and the lack of dire consequences

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    We analyze the 2001 Argentine default on its foreign debt and its consequences in terms of the existing literature on sovereign debt default. It is our purpose to evaluate this experience and to see to what extent the Argentine case requires a re-thinking on the nature and consequences of defaults. We show that the Argentine case contradicts many of their standard predictions, in particular its posterior lack of access to international credit, restriction to international trade and negative economic growth. Moreover, it corroborates the historical fact that many defaulters “get away with it.

    Mixed Higgsino Dark Matter from a Large SU(2) Gaugino Mass

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    We observe that in SUSY models with non-universal GUT scale gaugino mass parameters, raising the GUT scale SU(2) gaugino mass |M_2| from its unified value results in a smaller value of -m_{H_u}^2 at the weak scale. By the electroweak symmetry breaking conditions, this implies a reduced value of \mu^2 {\it vis \`a vis} models with gaugino mass unification. The lightest neutralino can then be mixed Higgsino dark matter with a relic density in agreement with the measured abundance of cold dark matter (DM). We explore the phenomenology of this high |M_2| DM model. The spectrum is characterized by a very large wino mass and a concomitantly large splitting between left- and right- sfermion masses. In addition, the lighter chargino and three light neutralinos are relatively light with substantial higgsino components. The higgsino content of the LSP implies large rates for direct detection of neutralino dark matter, and enhanced rates for its indirect detection relative to mSUGRA. We find that experiments at the LHC should be able to discover SUSY over the portion of parameter space where m_{\tg} \alt 2350-2750 ~GeV, depending on the squark mass, while a 1 TeV electron-positron collider has a reach comparable to that of the LHC. The dilepton mass spectrum in multi-jet + \ell^+\ell^- + \eslt events at the LHC will likely show more than one mass edge, while its shape should provide indirect evidence for the large higgsino content of the decaying neutralinos.Comment: 36 pages with 26 eps figure

    Sparticle mass spectra from SU(5) SUSY GUT models with bτb-\tau Yukawa coupling unification

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    Supersymmetric grand unified models based on the gauge group SU(5) often require in addition to gauge coupling unification, the unification of b-quark and τ\tau-lepton Yukawa couplings. We examine SU(5) SUSY GUT parameter space under the condition of bτb-\tau Yukawa coupling unification using 2-loop MSSM RGEs including full 1-loop threshold effects. The Yukawa-unified solutions break down into two classes. Solutions with low tan\beta ~3-11 are characterized by gluino mass ~1-4 TeV and squark mass ~1-5 TeV. Many of these solutions would be beyond LHC reach, although they contain a light Higgs scalar with mass <123 GeV and so may be excluded should the LHC Higgs hint persist. The second class of solutions occurs at large tan\beta ~35-60, and are a subset of tbτt-b-\tau unified solutions. Constraining only bτb-\tau unification to ~5% favors a rather light gluino with mass ~0.5-2 TeV, which should ultimately be accessible to LHC searches. While our bτb-\tau unified solutions can be consistent with a picture of neutralino-only cold dark matter, invoking additional moduli or Peccei-Quinn superfields can allow for all of our Yukawa-unified solutions to be consistent with the measured dark matter abundance.Comment: 19 pages, 5 figures, 1 table, PDFLate
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