### Abstract

We explore the extent to which string theories with higher-level gauge symmetries and non-standard hypercharge normalizations can reconcile the discrepancy between the string unification scale and the GUT scale extrapolated from the Minimal Supersymmetric Standard Model (MSSM). We determine the phenomenologically allowed regions of (k_{y}, k_{2}, k_{3}) parameter space, and investigate the proposal that there might exist string models with exotic hypercharge normalizations k_{y} which are less than their usual value k_{y} = 5/3. For a broad class of heterotic string models (encompassing most realistic string models which have been constructed), we prove that k_{y} ≥ 5/3. Beyond this class, however, we show that there exist consistent MSSM embeddings which lead to k_{y} < 5/3. We also consider the constraints imposed on k_{y} by demanding charge integrality of all unconfined string states, and show that only a limited set of hypercolor confining groups and corresponding values of k_{y} are possible.

Original language | English (US) |
---|---|

Pages (from-to) | 44-99 |

Number of pages | 56 |

Journal | Nuclear Physics B |

Volume | 467 |

Issue number | 1-2 |

State | Published - May 13 1996 |

Externally published | Yes |

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### ASJC Scopus subject areas

- Nuclear and High Energy Physics

### Cite this

*Nuclear Physics B*,

*467*(1-2), 44-99.

**String unification, higher-level gauge symmetries, and exotic hypercharge normalizations.** / Dienes, Keith R; Faraggi, Alon E.; March-Russell, John.

Research output: Contribution to journal › Article

*Nuclear Physics B*, vol. 467, no. 1-2, pp. 44-99.

}

TY - JOUR

T1 - String unification, higher-level gauge symmetries, and exotic hypercharge normalizations

AU - Dienes, Keith R

AU - Faraggi, Alon E.

AU - March-Russell, John

PY - 1996/5/13

Y1 - 1996/5/13

N2 - We explore the extent to which string theories with higher-level gauge symmetries and non-standard hypercharge normalizations can reconcile the discrepancy between the string unification scale and the GUT scale extrapolated from the Minimal Supersymmetric Standard Model (MSSM). We determine the phenomenologically allowed regions of (ky, k2, k3) parameter space, and investigate the proposal that there might exist string models with exotic hypercharge normalizations ky which are less than their usual value ky = 5/3. For a broad class of heterotic string models (encompassing most realistic string models which have been constructed), we prove that ky ≥ 5/3. Beyond this class, however, we show that there exist consistent MSSM embeddings which lead to ky < 5/3. We also consider the constraints imposed on ky by demanding charge integrality of all unconfined string states, and show that only a limited set of hypercolor confining groups and corresponding values of ky are possible.

AB - We explore the extent to which string theories with higher-level gauge symmetries and non-standard hypercharge normalizations can reconcile the discrepancy between the string unification scale and the GUT scale extrapolated from the Minimal Supersymmetric Standard Model (MSSM). We determine the phenomenologically allowed regions of (ky, k2, k3) parameter space, and investigate the proposal that there might exist string models with exotic hypercharge normalizations ky which are less than their usual value ky = 5/3. For a broad class of heterotic string models (encompassing most realistic string models which have been constructed), we prove that ky ≥ 5/3. Beyond this class, however, we show that there exist consistent MSSM embeddings which lead to ky < 5/3. We also consider the constraints imposed on ky by demanding charge integrality of all unconfined string states, and show that only a limited set of hypercolor confining groups and corresponding values of ky are possible.

UR - http://www.scopus.com/inward/record.url?scp=0030581990&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0030581990&partnerID=8YFLogxK

M3 - Article

AN - SCOPUS:0030581990

VL - 467

SP - 44

EP - 99

JO - Nuclear Physics B

JF - Nuclear Physics B

SN - 0550-3213

IS - 1-2

ER -