General soft terms from Supergravity including D-terms

We derive general expressions for soft terms in supergravity where D-terms contribute significantly to the supersymmetry breaking. Such D-terms can produce large splitting between scalar and fermionic partners in the spectrum. By requiring that supersymmetry breaking sets the cosmological constant to zero, we then parameterize the soft terms when D-terms dominate over F-terms or are comparable to them. We present an application of our results to the split supersymmetry scenario and briefly address the issue of moduli stabilisation.Comment: 6 Pages, no figures. To appear in proceedings of the XXXXth Rencontres de Moriond "Electroweak Interactions and Unified Theories", La Thuile, Italy, March 5-12, 2005; V2 Typos in eq.(9) corrected and other improvement

A little more Gauge Mediation and the light Higgs mass

We consider minimal models of gauge mediated supersymmetry breaking with an extra $U(1)$ factor in addition to the Standard Model gauge group. A $U(1)$ charged, Standard Model singlet is assumed to be present which allows for an additional NMSSM like coupling, $\lambda H_u H_d S$. The U(1) is assumed to be flavour universal. Anomaly cancellation in the MSSM sector requires additional coloured degrees of freedom. The $S$ field can get a large vacuum expectation value along with consistent electroweak symmetry breaking. It is shown that the lightest CP even Higgs boson can attain mass of the order of 125 GeV.Comment: 29 pages, 7 Figures; v2: updated references 30 pages, minor wordings modified, to appear in Nucl. Phys.

Bulk Majorana mass terms and Dirac neutrinos in Randall Sundrum Model

We present a novel scheme where Dirac neutrinos are realized even if lepton number violating Majorana mass terms are present. The setup is the Randall-Sundrum framework with bulk right handed neutrinos. Bulk mass terms of both Majorana and Dirac type are considered. It is shown that massless zero mode solutions exist when the bulk Dirac mass term is set to zero. In this limit, it is found that the effective 4D small neutrino mass is primarily of Dirac nature with the Majorana type contributions being negligible. Interestingly, this scenario is very similar to the one known with flat extra dimensions. Neutrino phenomenology is discussed by fitting both charged lepton masses and neutrino masses simultaneously. A single Higgs localised on the IR brane is highly constrained as unnaturally large Yukawa couplings are required to fit charged lepton masses. A simple extension with two Higgs doublets is presented which facilitates a proper fit for the lepton masses.Comment: 13 Pages, Few clarifications included and added references. Figure removed. Published in PR

Clockwork for Neutrino Masses and Lepton Flavor Violation

We investigate the generation of small neutrino masses in a clockwork framework which includes Dirac mass terms as well as Majorana mass terms for the new fermions. We derive analytic formulas for the masses of the new particles and for their Yukawa couplings to the lepton doublets, in the scenario where the clockwork parameters are universal. When the Majorana masses all vanish, the zero mode of the clockwork sector forms a Dirac pair with the active neutrino, with a mass which is in agreement with oscillations experiments for a sufficiently large number of clockwork gears. On the other hand, when the Majorana masses do not vanish, neutrino masses are generated via the seesaw mechanism. In this case, and due to the fact that the effective Yukawa couplings of the higher modes can be sizable, neutrino masses can only be suppressed by postulating a large Majorana mass for all the gears. Finally, we discuss the constraints on the mass scale of the clockwork fermions from the non-observation of the rare leptonic decay $\mu\rightarrow e\gamma$.Comment: 11 pages, 7 figure

Flavored Co-annihilations

Neutralino dark matter in supersymmetric models is revisited in the presence of flavor violation in the soft supersymmetry breaking sector. We focus on flavor violation in the sleptonic sector and study the implications for the co-annihilation regions. Flavor violation is introduced by a single $\tilde{\mu}_R-\tilde{\tau}_R$ insertion in the slepton mass matrix. Limits on this insertion from BR($\tau \to \mu + \gamma$) are weak in some regions of the parameter space where cancellations happen within the amplitudes. We look for overlaps in parameter space where both the co-annihilation condition as well as the cancellations within the amplitudes occur. In mSUGRA, such overlap regions are not existent, whereas they are present in models with non-universal Higgs boundary conditions (NUHM). The effect of flavor violation is two fold: (a) it shifts the co-annihilation regions towards lighter neutralino masses (b) the co-annihilation cross sections would be modified with the inclusion of flavor violating diagrams which can contribute significantly. Even if flavor violation is within the presently allowed limits, this is sufficient to modify the thermally averaged cross-sections by about (10-15)% in mSUGRA and (20-30)% in NUHM, depending on the parameter space. In the overlap regions, the flavor violating cross sections become comparable and in some cases even dominant to the flavor conserving ones. A comparative study of the channels is presented for mSUGRA and NUHM cases.Comment: 38 pages, 28 figures. Significantly expanded and improved version with a new section on channels and new appendices on mSUGRA and cross-sections, version accepted for publication in JHE

Neutrino Mass Constraints on R violation and HERA anomaly

R parity violating trilinear couplings $\lambda'_{1jk}$ of the minimal supersymmetric standard model (MSSM) are constrained from the limit on the electron neutrino mass. Strong limits on these couplings follow from the earlier neglected contribution due to sneutrino vacuum expectation values. The limits on most of the $\lambda'_{1jk}$ couplings derived here are stronger than the existing ones for a wide range in parameters of MSSM. These limits strongly constrain the interpretation of recent HERA results in $e^+ p$ scattering in terms of production of squarks through $R$ violating couplings. In particular, the interpretation in terms of $\tilde{t}_L$ production off strange quark as suggested recently is not viable for wide ranges in MSSM parameters.Comment: 15 pages with 5 figures, minor typos corrected and a new reference adde