We study gauge mediation of supersymmetry breaking in SU(5) supersymmetric grand unified theory with gauge fields as messengers. The generated soft supersymmetry breaking parameters lead to close to maximal mixing scenario for the Higgs mass and highly red
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Figure2:Allowedregionofparameterspaceandthedegreeof netuningintheMSUSY tanβplaneforpuregaugemediation,Nmess=0andbG=3.TheshadedregionsareexcludedbydirectsearchesforSUSYandHiggsparticles.WeusethelimitsonthemassofthelightestHiggsboson,mh0>114.4GeV,thelighteststop,mt >95.7GeV,thelighteststau,mτ >81.9GeV,andthelightestchargino,mχ±>117GeV.Theregiondenotedas“tachyon”isexcludedduetotachyonicspectrum.TheblackdashedlineseparatesregionswheresneutrinoorstauisNLSP.
Sincethereareonlytwoparametersinthismodel,itiseasytoexplorethewhole
parameterspace.InFig.2weshowallowedparameterspaceinMSUSY–tanβplane,togetherwithregionsexcludedbydirectsearchesforSUSYandHiggsparticles.Moderatetolargetanβisallowedand,asusual,assmallMSUSYwhichstillsatis esthelimitontheHiggsmassispreferredbynaturalness.InmostregionoftheparameterspacesneutrinoisNLSPforsmalltanbeta(gravitinoistheLSP)andstauisNSLPforlargetanbetaduetolargemixingoftheleftandright-handedstau.Arepresentativepointfromthisregionisgiveninthe rst(stauNLSP)andthethirdcolumn(sneutrinoNLSP)ofTable1.Aswewilldiscusslater,smallcontributionsfromgravitymediationcaneasilypushsneutrinoorstauabovethelightestneutralinoleadingtoalargeregionwhereneutralinois(N)LSP.
4.2GaugemediationwithgravitycontributionintheHiggssector
Addingacontributionfromgravitymediationopensapossibilityofgeneratingtheµhttp://www.77cn.com.cnparableinsizesoftmassessquaredforHuandHdarealsogenerated.WeparameterizeadditionalcontributiontotheHiggssoftmasses
22squaredby:cHuMSUSYandcHdMSUSY.Anexampleoftherenormalizationgrouprunning
ofsoftSUSYbreakingparametersinthiscaseisgiveninFig.3anddetailedinformationaboutthisscenariocanbefoundinthesecondcolumnofTable1.Addinggravitycontribu-tiontosoftHiggsmassessquareddoesnotsigni cantlya ectrunningofothersoftSUSY