SU(5)xU(1): a string paradigm of a TOE and its experimental consequences

Abstract

We present a string-inspired/derived supergravity model based on the flipped $SU(5)\times U(1)$ structure supplemented by a minimal set of additional matter representations such that unification occurs at the string scale ($\sim 10^{18}\text{GeV}$). This model is complemented by two string supersymmetry breaking scenaria: the $SU(N,1)$ no-scale supergravity model and a dilaton-induced supersymmetry breaking scenario. Both imply universal soft supersymmetry breaking parameters: $m_0=0,A=0$ and $m_0=\text{coeff}1\sqrt{3}{m}_{1/2},A=-m_{1/2}$ respectively. In either case the models depend on only three parameters: $m_t$, $\tan \beta$, and $m_{\tilde{g}}$. We present a comparative study of the sparticle and Higgs spectra of both models and conclude that even though both can be partially probed at the Tevatron, LEPII, and HERA, a larger fraction of the parameter space of the no-scale model is actually accessible. In both cases there is a more constrained version which allows to determine $\tan \beta$ in terms of $m_t,m_{\tilde{g}}$. In the strict no-scale case we find that the value of $m_t$ determines the sign of $\mu$ ($\mu >0:m_t\text{lsim}135\text{GeV}$, $\mu <0:m_t\text{gsim}140\text{GeV}$) and whether the lightest Higgs boson mass is above or below $100\text{GeV}$. In the more constrained version of the dilaton scenario, $\tan \beta \approx 1.4-1.6$ and $m_t\text{lsim}155\text{GeV}$, $61\text{GeV}\text{lsim}{m}_h\text{lsim}91\text{GeV}$ follow. Thus, continuing Tevatron top-quark searches and LEPI,II Higgs searches could probe this restricted scenario completely.

Comments: CERN-TH.6926/93, CTP-TAMU-33/93, LaTeX, 33 pages, 11 embedded figures. Significant numerical correction to the dilaton scenario. Complete ps file (7943 blocks,3.33MB) available via anonymous ftp from site tamsun.tamu.edu in directory incoming, filename: CTP-TAMU-33-93.ps