Chih-hao Chen

Signals for minimal supergravity at the CERN Large Hadron Collider. II. Multilepton channels.

We use ISAJET to perform a detailed study of the multilepton signals expected from cascade decays of supersymmetric particle produced at the CERN LHC. Our analysis is performed within the framework of the minimal supergravity model with gauge coupling unification and radiative electroweak symmetry breaking. We delineate the regions of parameter space where jets plus missing energy plus 1, 2 (opposite-sign and same-sign dileptons), and 3 isolated lepton events should be visible above standard model backgrounds. We find that if any {ital E}/{sub {ital T}} signal at the LHC is to be attributed to gluino and/or squark production, and if {ital m}{sub {tilde {ital g}}}{approx_lt}1 TeV, then several of these signals must be simultaneously observable. Furthermore, assuming 10fb{sup {minus}1} of integrated luminosity, we find that the reach for supersymmetry in the 1l+jets+{ital E}/{sub {ital T}} channel extends to {ital m}{sub {tilde {ital g}}}{approximately}2300(1600) GeV for {ital m}{sub {tilde {ital q}}}{approximately}{ital m}{sub {tilde {ital g}}} ({ital m}{sub {tilde {ital q}}}{approximately}1.5{ital m}{sub {tilde {ital g}}}), and exceeds the corresponding reach in the 0l+{ital E}/{sub {ital T}} channel. We show that measurements of the various topological cross sections, jet, and {ital B}-hadron multiplicities in these events, together with the charge asymmetry for singlemorexa0» lepton and same-sign dilepton events, and flavor asymmetry for opposite-sign dilepton events, serve to narrow the allowed range of underlying SUGRA parameter values. We also delineate parameter regions where signals with clean isolated dilepton (from slepton production) and trilepton events (from chargino or neutralino production) are visible at the LHC, and examine the extent to which these signals can be separated from other SUSY sources. {copyright} {ital 1996 The American Physical Society.}«xa0less

Searching for invisible and almost invisible particles at e+ e- colliders

We explore the techniques, cross sections, and expected signal significance for detecting invisible and almost invisible particles at CERN {ital e}{sup +}{ital e}{sup {minus}} collider LEP2 and the NLC (next linear {ital e}{sup +}{ital e}{sup {minus}} collider) by means of a hard photon tag. Examples from supersymmetry include the lightest chargino and second lightest neutralino when their masses are nearly the same as that of the lightest neutralino [the LSP (lightest supersymmetric particle)], and invisibly decaying sneutrinos. The importance of particular features of the detectors is discussed. {copyright} {ital 1996 The American Physical Society.}

Collider phenomenology for supersymmetry with large tan Beta

If the parameter tan{beta} of the minimal supersymmetric model is large, then b and {tau} Yukawa interactions are important. These can significantly modify the masses and decays of sparticles. We describe new calculations which allow a reliable exploration of large tan{beta} values, and discuss implications for collider experiments. For large values of tan{beta} , charginos and neutralinos may dominantly decay to {tau} leptons or b quarks. The usual cross sections for multilepton signatures may be greatly reduced, but supersymmetry may be detectable via new signals involving {tau} {close_quote}s or b {close_quote}s in the final state. {copyright} {ital 1997} {ital The American Physical Society}

Supersymmetry reach of Fermilab Tevatron upgrades: A comparative study

We use ISAJET to perform a detailed comparison of the supersymmetry reach of the current Fermilab Tevatron (100 pb{sup {minus}1}) with that of the Main Injector (2 fb{sup {minus}1}) and the proposed TeV33 upgrade designed to yield an integrated luminosity of 25 fb{sup {minus}1}. Our analysis is performed within the framework of the minimal supergravity model with gauge coupling unification and radiative electroweak symmetry breaking. For each of these three luminosity options, we delineate the regions of parameter space where jets plus missing energy plus 0, 1, 2 (opposite-sign and same-sign dileptons), and 3 isolated lepton signals from the cascade decays of sparticles should be visible above standard model backgrounds. We compare these with the parameter regions where signals in the clean isolated dilepton and trilepton channels (from chargino or neutralino and slepton production) should be observable. {copyright} {ital 1996 The American Physical Society.}

Impact of hadronic decays of the lightest neutralino on the reach of the CERN LHC

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Multichannel search for minimal supergravity at [ital p[bar p]] and [ital e][sup +][ital e][sup [minus]] colliders

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Probing gauge-mediated supersymmetry breaking models at the Fermilab Tevatron via delayed decays of the lightest neutralino

parity is not conserved, the lightest supersymmetric particle could decay via lepton-number-violating or baryon-number-violating interactions. The latter case is particularly insidious since it leads to a reduction of the

Supersymmetry reach of Tevatron upgrades: The Large tan Beta case

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Supersymmetry reach of Fermilab Tevatron upgrades: The large tanthinsp{beta} case

as well as leptonic signals for supersymmetry. We evaluate cross sections for jets plus

Supersymmetry reach of Fermilab Tevatron upgrades: The largetanβcase

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