118351491
Lepton flavor violation in low-scale seesaw models: SUSY and non-SUSY contributions
A bstractTaking the supersymmetric inverse seesaw mechanism as the explanation for neutrino oscillation data, we investigate charged lepton flavor violation in radiative and 3-body lepton decays as well as in neutrinoless μ − e conversion in muonic atoms. In contrast to former studies, we take into account all possible contributions: supersymmetric as well as non-supersymmetric. We take CMSSM-like boundary conditions for the soft supersymmetry breaking parameters. We find several regions where cancellations between various contributions exist, reducing the lepton flavor violating rates by an order of magnitude compared to the case where only the dominant contribution is taken into account. This is in particular important for the correct interpretation of existing data as well as for estimating the reach of near future experiments where the sensitivity will be improved by one to two orders of magnitude. Moreover, we demonstrate that ratios like BR(τ → 3μ)/BR(τ → μe+e−) can be used to determine whether the supersymmetric contributions dominate over the W± and H± contributions or vice versa.
118633236
Implications of gauge kinetic mixing on Z' and slepton production at the LHC
We consider a supersymmetric version of the standard model extended by an additional U(1)_{B-L}. This model can be embedded in an mSUGRA-inspired model where the mass parameters of the scalars and gauginos unify at the scale of grand unification. In this class of models the renormalization group equation evolution of gauge couplings as well as of the soft SUSY-breaking parameters require the proper treatment of gauge kinetic mixing. We first show that this has a profound impact on the phenomenolgy of the Z' and as a consequence the current LHC bounds on its mass are reduced significantly from about 1920 GeV to 1725 GeV. They are even further reduced if the Z' can decay into supersymmetric particles. Secondly, we show that in this way sleptons can be produced at the LHC in the 14 TeV phase with masses of several hundred GeV. In the case of squark and gluino masses in the multi-TeV range, this might become an important discovery channel for sleptons up to 650 GeV (800 GeV) for an integrated luminosity of 100 fb^{-1} (300 fb^{-1}).
118587432
SO(10) inspired gauge-mediated supersymmetry breaking
We consider a supersymmetric model motivated by a SO(10) grand unified theory: the gauge sector near the supersymmetry scale consists of SU(3)_c x SU(2)_L x U(1)_R x U(1)_{B-L}. We embed this model in minimal gauge mediation and incorporate neutrino data via an inverse seesaw mechanism. Also in this restricted model, the additional D terms can rise the light Higgs mass in a sizable way. Therefore, it is much easier to obtain m_h \simeq 125 GeV without the need to push the supersymmetry spectrum to extremely large values as it happens in models with minimal supersymmetric standard model particle content only. We show that this model predicts a diphoton rate of the Higgs equal to or smaller than the standard model expectation. We discuss briefly the collider phenomenology with a particular focus on the next to lightest supersymmetric particle in which this model offers the sneutrino as an additional possiblity. Moreover, we point out that, also in this model variant, supersymmetry can be discovered in Z' decays even in scenarios in which the strongly interacting particles are too heavy to be produced at a sizable rate at the LHC with 14 TeV. In addition, we show that lepton flavor violating observables constrain the size of the neutrino Yukawa couplings for which, in particular, muon decays and \mu-e conversion in heavy atoms are of particular importance. Once these constraints are fulfilled the rates for \tau decays are predicted to be below the reach of near-future experiments.
53529353
Higher dimensional effective operators for direct dark matter detection
A bstractWe discuss higher dimensional effective operators describing interactions between fermionic dark matter and Standard Model particles. They are typically suppressed compared to the leading order effective operators, which can explain why no conclusive direct dark matter detection has been made so far. The ultraviolet completions of the effective operators, which we systematically study, require new particles. These particles can potentially have masses at the TeV scale and can therefore be phenomenologically interesting for LHC physics. We demonstrate that the lowest order options require Higgsportal interactions generated by dimension six operators. We list all possible tree-level completions with extra fermions and scalars, and we discuss the LHC phenomenology of a specific example with extra heavy fermion doublets.
120538467
Neutrino mass from higher than d=5 effective operators with discrete symmetries
In beyond Standard Model physics scenarios one often has to extend the Higgs sector and introduce additional (discrete) symmetries. In such models it is possible that the Weinberg operator is forbidden and the leading contribution to neutrino mass is generated by operators with mass dimension d > 5. These higher-dimensional operators are stronger suppressed and therefore the new physics scale can be as low as the TeV scale. With this approach it is possible to test neutrino mass models at colliders, such as the LHC. We will demonstrate how these operators can be systematically studied and present an exemplary implementation of such a model and its phenomenological consequences. We also show how it can be embedded into an SU(5) GUT framework. Finally we present a specific realization of this model where we can have tri-bimaximal mixing with large deviations due to a softly broken symmetry.
118011302
Big bang nucleosynthesis : the morning after
119187487
Neutrino mass from a d=7 effective operator in a SUSY-GUT framework
A bstractModels, where neutrino mass originates from physics at the TeV scale and which are potentially testable at the LHC, need additional suppression mechanisms to describe the smallness of neutrino masses. We consider models in which neutrino mass is generated from the d = 7 operator LLHuHuHdHu in the context of SUSY-GUTs containing an SU(5) subgroup, where the d = 5 Weinberg operator can be forbidden by a discrete symmetry. That is, we identify the embeddings in GUT multiplets and their consequences for phenomenology and renormalization group evolution. We use a specific example to exemplify the challenges. In this case, additional heavy d-quarks are predicted, which are constrained by cosmology, in particular, by big bang nucleosynthesis and direct searches for heavy nuclei. We show that in the NMSSM extension of the model, the discrete symmetry needs to be broken, which can be the origin of deviations from tri-bimaximal mixings. Finally we demonstrate that our example is the only tree level decomposition which is consistent with perturbativity up to the GUT scale and neutrino mass generation by a leading d = 7 contribution.