arXiv subjects

Mirjam Cvetic

Publications and source records attributed to Mirjam Cvetic.

135 records · Page 8Linked to original sources

arXiv1993

Determination of $Z'$ Gauge Couplings to Quarks and Leptons at Future Hadron Colliders

We point out that at future hadron colliders the ratio of cross sections for $pp\to Z'\to \ell^+\ell^-$ in two rapidity bins is a useful probe of the relative couplings of the $Z'$ to $u$ and $d$ quarks. Combined with the forward-backward asymmetry, the rare decay modes $Z'\to W \ellν_\ell$, and three associated productions $pp\to Z'V$ ($V=Z,W,γ$), and assuming inter-family universality, small $Z-Z'$ mixing, and the $Z'$ charge commuting with the $SU_{2L}$ generators, three out of four normalized couplings could be extracted. An analysis of the statistical uncertainties expected for the above probes at the LHC for typical models with $M_{Z'}\simeq1$ TeV shows that one lepton coupling and two combinations of quark couplings could be determined to around 5\%, 20\%, and 30\%, respectively. This allows for a clear distinction between models.

hep-ph↗

arXiv1992

Domain Walls in $N=1$ Supergravity

We discuss a study of domain walls in $N=1, d=4$ supergravity. The walls saturate the Bogomol'nyi bound of wall energy per unit area thus proving stability of the classical solution. They interpolate between two vacua whose cosmological constant is non-positive and in general different. The matter configuration and induced geometry are static. We discuss the field theoretic realization of these walls and classify three canonical configurations with examples. The space-time induced by a wall interpolating between the Minkowski (topology $\Re^{4}$) and anti-de~Sitter (topology $S^{1}(time) \times \Re^{3}(space)$) vacua is discussed. (Comments in chapter 6 on AdS-Minkowski wall induced space-time have been slightly changed)

hep-th↗

arXiv1992

Signatures for Heavy $\bf Z'$ Bosons at Hadron Colliders

We discuss three promising diagnostic probes of the couplings of a possible heavy $Z'$ boson at hadron colliders: the forward-backward asymmetry into leptons, the rare decay $Z' \ra W^{\pm} \ell^{\mp} ν$, and associated production $pp \ra Z'W,\; Z'Z$. A general model-independent framework is proposed for interpreting these and other data. Clean tests of whether a new $W'$ couples to right-handed currents, of the ratio $g_R/g_L$ of gauge couplings, and of the non-abelian vertex in left-right symmetric models are described.

hep-ph↗

arXiv1992

Stringy Origin of Neutrino Masses within the Minimal Supersymmetric Standard Model

We present a ``gravity-induced'' seesaw mechanism, which accommodates neutrino masses ($m_ν\propto m_u^2/M_I$, with $m_u$ the corresponding quark mass and $M_I\simeq 4\times10^{11}$ GeV) compatible with the MSW study of the Solar neutrino deficit within the minimal supersymmetric Standard Model (the grand desert with the gauge coupling unification at $M_U\simeq 2\times10^{16}$ GeV). We show that for large radius ($R^2/α'={\cal O}(20)$) Calabi-Yau spaces, threshold corrections ensure $M_U^2=M_C^2/{\cal O} (2R^2/α')$ and the magnitude of the non-renormalizable terms in the superpotential yields $M_I= {\cal O}(e^{-R^2/α'})M_C$. Here $M_C=g\times 5.2\times 10^{17}$GeV is the scale of the tree level (genus zero) gauge coupling ($g$) unification.

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arXiv1992

Stability of Vacua and Domain Walls in Supergravity and Superstring Theory

We address the possibility of false vacuum decay in $N=1$ supergravity theories, including those corresponding to superstring vacua. By establishing a Bogomol'nyi bound for the energy density stored in the domain wall of the $O(4)$ invariant bubble, we show that supersymmetric vacua remain absolutely stable against false vacuum decay into another supersymmetric vacuum, including those from a Minkowski to an anti-deSitter (AdS) one. As a consequence, there are no compact static spherical domain walls, while on the other hand there exist planar domain walls interpolating between non-degenerate supersymmetric vacua, e.g. between Minkowski (topology $\Re^{4}$) and AdS (topology $S^{1}(time) \times \Re^{3}(space)$) vacua. (Talk presented at the XXVI International Conference on High Energy Physics August 6-12, 1992, Dallas, Texas)

hep-th↗

arXiv1992

Nonperturbative Stability of Supergravity and Superstring Vacua

We investigate the possibility of false vacuum decay in $N=1$ supergravity theories. By establishing a Bogomol'nyi bound for the energy density stored in the domain wall of the $O(4)$ invariant bubble, we show that supersymmetric vacua remain absolutely stable against false vacuum decay into another supersymmetric vacuum. This conforms with and completes the previous perturbative analysis of Weinberg. Implications for dynamical supersymmetry breaking and decompactification instabilities in superstring theory are discussed. In addition, we show that there are no compact static spherical domain walls.

hep-th↗

arXiv1992

Neutrino Masses within the Minimal Supersymmetric Standard Model

We investigate the possibility of accommodating neutrino masses compatible with the MSW study of the Solar neutrino deficit within the minimal supersymmetric Standard Model. The ``gravity-induced'' seesaw mechanism based on an interplay of nonrenormalizable and renormalizable terms in the superpotential allows neutrino masses $m_ν\propto m_u^2/M_I$, with $m_u$ the corresponding quark mass and $M_I\simeq 4\times10^{11}$ GeV, while at the same time ensuring the grand desert with the gauge coupling unification at $M_U\simeq 2\times10^{16}$ GeV. The proposed scenario may be realized in a class of string vacua, {\it i.e.,} large radius ($R^2/α'={\cal O}(20)$) $(0,2)$ Calabi-Yau spaces. In this case $M_U^2=M_C^2/{\cal O} (2R^2/α')$ and $M_I= {\cal O}(e^{-R^2/α'})M_C$. Here $M_C=g\times 5.2\times 10^{17}$GeV is the scale of the tree level (genus zero) gauge coupling ($g$) unification.

hep-th↗

arXiv1992

Stringy Domain Walls and Other Stringy Topological Defects

We point out that the moduli sector of the $(2,2)$ string compactification with its nonperturbatively preserved non-compact symmetries is a framework to study global topological defects. Based on the target space modular invariance of the nonperturbative superpotential of the four-dimensional $N=1$ supersymmetric string vacua, topologically stable stringy domain walls are found. Explicit supersymmetric solutions for the modulus field and the metric, which saturate the Bogomol'nyi bound, are presented. They interpolate between {\it non-degenerate} vacua. As a corollary, this defines a new notion of vacuum degeneracy of supersymmetric vacua. Nonsupersymmetric stringy domain walls are discussed as well. The moduli sectors with more than one modulus and the non-compact continous symmetry preserved allow for global monopole-type and texture-type configurations.

hep-th↗

arXiv1992

Static Domain Walls in N=1 Supergravity

We study supersymmetric domain walls in N=1 supergravity theories, including those with modular-invariant superpotentials arising in superstring compactifications. Such domain walls are shown to saturate the Bogomol'nyi bound of wall energy per unit area. We find \sl static \rm and \sl reflection asymmetric \rm domain wall solutions of the self-duality equations for the metric and the matter fields. Our result establishes a new class of domain walls beyond those previously classified. As a corollary, we define a precise notion of vacuum degeneracy in the supergravity theories. In addition, we found examples of global supersymmetric domain walls that do not have an analog when gravity is turned on. This result establishes that in the case of extended topological defects gravity plays a crucial, nontrivial role.

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