D-term Supersymmetry Breaking Research Articles

No-scale supergravity with new Fayet-Iliopoulos term

We find a new class of N=1 no-scale supergravity models with F- and D-term supersymmetry breaking, using a new Fayet-Iliopoulos term. The minimal setup contains one U(1) vector multiplet and one neutral chiral multiplet parametrizing SL(2,R)/U(1) manifold, with constant superpotential and linear gauge kinetic function. In our construction the FI term is field-dependent, and one can obtain flat vanishing potential (Minkowski vacuum) with broken SUSY, and global SL(2,R) invariance (self-duality) of the bosonic equations of motion. The spectrum of the model includes a massive spin-1/2 field as well as a vector, a scalar, and a pseudo-scalar – all classically massless. We discuss several modifications/extensions of the model as well as the introduction of matter fields. We also find a two-field extension of already existing no-scale model.

From linear to non-linear SUSY and back again

We show that couplings of the goldstino field, appearing when global supersymmetry is broken, can always be described in superspace by means of a nilpotent chiral superfield X, satisfying X2 = 0. This applies to both F-term and D-term supersymmetry breaking, even when the supersymmetry breaking model admits a linear description.

Deformations, moduli stabilisation and gauge couplings at one-loop

We investigate deformations of {mathrm{mathbb{Z}}}_2 orbifold singularities on the toroidal orbifold {T}^6/left({mathrm{mathbb{Z}}}_2times {mathrm{mathbb{Z}}}_6right) with discrete torsion in the framework of Type IIA orientifold model building with intersecting D6-branes wrapping special Lagrangian cycles. To this aim, we employ the hypersurface formalism developed previously for the orbifold {T}^6/left({mathrm{mathbb{Z}}}_2times {mathrm{mathbb{Z}}}_6right) with discrete torsion and adapt it to the left({mathrm{mathbb{Z}}}_2times {mathrm{mathbb{Z}}}_6times Omega mathrm{mathcal{R}}right) point group by modding out the remaining {mathrm{mathbb{Z}}}_3 subsymmetry and the orientifold projection Omega mathrm{mathcal{R}} . We first study the local behaviour of the {mathrm{mathbb{Z}}}_3times Omega mathrm{mathcal{R}} invariant deformation orbits under non-zero deformation and then develop methods to assess the deformation effects on the fractional three-cycle volumes globally. We confirm that D6-branes supporting USp(2N) or SO(2N) gauge groups do not constrain any deformation, while deformation parameters associated to cycles wrapped by D6-branes with U(N) gauge groups are constrained by D-term supersymmetry breaking. These features are exposed in global prototype MSSM, Left-Right symmetric and Pati-Salam models first constructed in [1, 2], for which we here count the number of stabilised moduli and study flat directions changing the values of some gauge couplings.Finally, we confront the behaviour of tree-level gauge couplings under non-vanishing deformations along flat directions with the one-loop gauge threshold corrections at the orbifold point and discuss phenomenological implications, in particular on possible LARGE volume scenarios and the corresponding value of the string scale Mstring, for the same global D6-brane models.

Linking natural supersymmetry to flavour physics

With the aim of linking natural supersymmetry to flavour physics, a model is proposed based on a family symmetry G \times U(1), where G is a discrete nonabelian subgroup of SU(2), with both F-term and (abelian) D-term supersymmetry breaking. A good fit to the fermion masses and mixing is obtained with the same U(1) charges for the left- and right- handed quarks of the first two families and the right-handed bottom quark, and with zero charge for the left-handed top-bottom doublet and the the right handed top. The model shows an interesting indirect correlation between the correct prediction for the V_{ub}/V_{cb} ratio and large right-handed rotations in the (s,b) sector, required to diagonalise the Yukawa matrix. For the squarks, one obtains almost degenerate first two generations. The main source of the FCNC and CP violation effects is the splitting between the first two families and the right-handed sbottom determined by the relative size of F-term and D-term supersymmetry breaking. The presence of the large right-handed rotation implies that the bounds on the masses of the first two families of squarks and the right handed sbottom are in a few to a few tens TeV range. The picture that emerges is light stops and left handed sbottom and much heavier other squarks.

μ PROBLEM, SO(10) SUSY GUT AND HEAVY GLUINO LSP

we present a solution to the μ problem in an SO(10) supersymmetric grand unified (SUSY GUT) model with gauge mediated (GMSB) and D-term supersymmetry breaking. A Peccei-Quinn (PQ) symmetry is broken at the messenger scale and enables the generation of the μ term. The invisible axion (Goldstone boson of PQ symmetry breaking) is a cold dark matter candidate. At low energy, our model leads to a phenomenologically acceptable version of the minimal supersymmetric standard model (MSSM) with novel particle phenomenology. Either the gluino or the gravitino is the lightest supersymmetric particle (LSP). The phenomenological constraints on the model result in a Higgs with mass ~ 86 – 91 GeV and tan β ~ 9 – 14.

Solution to the μ problem in the presence of a heavy gluino LSP

In this paper we present a solution to the $\mu$ problem in an SO(10) supersymmetric grand unified model with gauge mediated and D-term supersymmetry breaking. A Peccei-Quinn symmetry is broken at the messenger scale $M\sim 10^{12}$ GeV and enables the generation of the $\mu$ term. The boundary conditions defined at $M$ lead to a phenomenologically acceptable version of the minimal supersymmetric standard model with novel particle phenomenology. Either the gluino or the gravitino is the lightest supersymmetric particle (LSP). If the gravitino is the LSP, then the gluino is the next-to-LSP (NLSP) with a lifetime on the order of one month or longer. In either case this heavy gluino, with mass in the range 25 - 35 GeV, can be treated as a stable particle with respect to experiments at high energy accelerators. Given the extensive phenomenological constraints we show that the model can only survive in a narrow region of parameter space resulting in a light neutral Higgs with mass $\sim 86 - 91$ GeV and $\tan\beta \sim 9 - 14$. In addition the lightest stop and neutralino have mass $\sim 100 - 122$ GeV and $\sim 50 - 72$ GeV, respectively. Thus the model will soon be tested. Finally, the invisible axion resulting from PQ symmetry breaking is a cold dark matter candidate.