Constraints on Left-Right Symmetric and $E_6$ Superstring Models from the Number of Light Neutrino Species

Abstract

Using the experimental value for the rate $R_{exp}^{LEP}={\Gamma }_{inv}/{\Gamma }_{l\bar{l}}=5.942\pm 0.016$, we derive constraints on the number of light neutrino species with the invisible width method in the framework of a left-right symmetric model (LRSM) and a $E_6$ superstring model as a function of their respective mixing angles for the neutral vector gauge bosons. Using the above LEP result we get the constraints $-1.6\times 10^{-3}\le \varphi \le 1.1\times 10^{-3}$ and $-1.3\times 10^{-2}\le {\varphi }_{E_6}\le 0.4\times 10^{-2}$, which are stronger than those obtained in previous studies of these models.

9 pages, 4 figures, Submit to Modern Physics Letter A

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• The Cosmological Parameters 2006
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• Effective number of neutrinos and baryon asymmetry from BBN and WMAP
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• Bounding the magnetic and electric dipole moments of tau nu from the process e+e- --> nu bar nu gamma in E6 Superstring Models
• Bounding the Tau Neutrino Magnetic Moment from the Process E+ E- --> Gamma Nu Anti-Nu

Cited by in corpus (4)

• Probing the ZZgamma and Zgammagamma Couplings Through the Process e+e- --> nu anti-nu gamma
• Emissivity of neutrinos in supernova in a left-right symmetric model
• Bounds on the anomalous $HZ\gamma$ vertex arising from the process $e^{+}{e}^{-}\to {\tau }^{+}{\tau }^{-}\gamma$
• Stellar energy loss rates in the pair-annihilation process beyond the standard model