Expectations for the muon g-2 in simplified models with dark matter

We investigate simplified models of new physics that can accommodate the measured value of the anomalous magnetic moment of the muon and the relic density of dark matter. We define a set of renormalizable, SU(2)$\times$U(1) invariant extensions of the Standard Model, each comprising an inert $Z_2$-odd scalar field and one or more vector-like pairs of colorless fermions that communicate to the muons through Yukawa-type interactions. The new sectors are classified according to their transformation properties under the Standard Model gauge group and all models are systematically confronted with a variety of experimental constraints: LEP mass bounds, direct LHC searches, electroweak precision observables, and direct searches for dark matter. We show that scenarios featuring only one type of new fermions become very predictive once the relic density and collider constraints are taken into account, as in this case $g-2$ is not enhanced by chirality flip. Conversely, for models where an additional source of chiral-symmetry violation is generated via fermion mixing, the constraints are much looser and new precision experiments with highly suppressed systematic uncertainties may be required to test the parameter space.Comment: 38 pages, 12 figures. Added constraints from CMS soft opposite-sign leptons and ATLAS h to gamma gamma. References added, typos fixed. Matches published versio

The discreet charm of higgsino dark matter - a pocket review

We give a brief review of the current constraints and prospects for detection of higgsino dark matter in low-scale supersymmetry. In the first part we argue, after performing a survey of all potential dark matter particles in the MSSM, that the (nearly) pure higgsino is the only candidate emerging virtually unscathed from the wealth of observational data of recent years. In doing so by virtue of its gauge quantum numbers and electroweak symmetry breaking only, it maintains at the same time a relatively high degree of model-independence. In the second part we properly review the prospects for detection of a higgsino-like neutralino in direct underground dark matter searches, collider searches, and indirect astrophysical signals. We provide estimates for the typical scale of the superpartners and fine tuning in the context of traditional scenarios where the breaking of supersymmetry is mediated at about the scale of Grand Unification and where strong expectations for a timely detection of higgsinos in underground detectors are closely related to the measured 125 GeV mass of the Higgs boson at the LHC.Comment: 30 pages, 7 figures. Invited review for Advances in High Energy Physics. v3: References added, matches published versio

MSSM fits to the ATLAS 1 lepton excess

We use the framework of the p19MSSM to perform a fit to the mild excesses over the Standard Model background recently observed in three bins of the ATLAS 1-lepton + (b-)jets + MET search. We find a few types of spectra that can fit the emerging signal and at the same time are not excluded by other LHC searches. They can be grouped roughly in two categories. The first class is characterized by the presence of one stop or stop and sbottoms with mass in the ballpark of 700-800 GeV and a neutralino LSP of mass around 400 GeV, with or without the additional presence of an intermediate chargino. In the second type of scenarios the stop, lightest chargino, sbottom if present, and the neutralino are about or heavier than ~650 GeV and the signal originates from cascade decays of squarks of the 1st and 2nd generation, which should have a mass of 1.1-1.2 TeV. For the best-fit scenarios, we compare the global chi-squared with respect to several ATLAS and CMS searches with the corresponding chi-squared of the Standard Model expectation, showing that the putative signal is also favored globally with respect to the background only hypothesis. We point out that if the observed excess persists in the next round of data, it should be accompanied by associated significant excesses in all-hadronic final state searches.Comment: 21 pages, 2 figures. Added recast of CMS 1-lepton search. Added global analysis of chi-squared contributions from all implemented searches. Added references. Matches published versio

Gauge contribution to the 1/NF1/N_F expansion of the Yukawa coupling beta function

We provide a closed analytical form for the gauge contribution to the beta function of a generic Yukawa coupling in the limit of large $N_F$, where $N_F$ is the number of heavy vector-like fermions charged under an abelian or non-abelian gauge group. The resummed expression is finite and for the abelian case presents a pole at the same location as for the corresponding gauge beta function. When applied to new physics scenarios characterized by large Yukawa couplings, the contribution calculated here can cure their pathological UV behavior and make the couplings asymptotically free.Comment: 18 pages, 4 figures. Added clarification on our choice of gauge, which was previously stated incorrectly. Typos fixed. References adde

Two ultimate tests of constrained supersymmetry

We examine the prospects of using two alternative and complementary ways to explore the regions that are favored by global constraints in two simple unified supersymmetric models: the CMSSM and the NUHM. First, we consider BR(Bs->\mu\mu), which has recently been for the first time measured by LHCb. In the CMSSM we show that ultimate, but realistic, improvement in the determination of the observable to about 5-10% around the Standard Model value would strongly disfavor the A-funnel region, while not affecting much the other favored regions. Second, we show that all the favored regions of the CMSSM will be, for the most part, sensitive to direct dark matter searches in future one-tonne detectors. A signal at low WIMP mass (<=450 GeV) and low spin-independent cross section would then strongly favor the stau coannihilation region while a signal at higher WIMP mass (~800 GeV to ~1.2 TeV) would clearly point to the region where the neutralino is higgsino-like with mass ~1 TeV. A nearly complete experimental testing of the CMSSM over multi-TeV ranges of superpartner masses, far beyond the reach of direct SUSY searches at the LHC, can therefore be achievable. In the NUHM, in contrast, similar favored regions exist but a sample study reveals that even a precise determination of BR(Bs->\mu\mu) would have a much less constraining power on the model, including the A-funnel region. On the other hand, this could allow one to, by detecting in one-tonne detectors a signal for 500 GeV<m_{\chi}<800 GeV, strongly disfavor the CMSSM.Comment: 32 pages, 11 figures. Discussion of the properties of the higgsino region extended. One figure added. Version published in JHE

Flavored gauge mediation in the Peccei-Quinn NMSSM

We investigate a particular version of the Peccei-Quinn (PQ) NMSSM characterized by an economical and rigidly hierarchical flavor structure and based on flavored gauge mediation and on some considerations inspired by string theory GUTs. In this way we can express the Lagrangian of the PQ NMSSM through very few parameters. The obtained model is studied numerically and confronted with the most relevant phenomenological constraints. We show that typical spectra are for the most part too heavy to be significantly probed at the LHC, but regions of the parameter space exist yielding signatures that might possibly be observed during Run II. We also calculate the fine tuning of the model. We show that, in spite of the appearance of large scales in the superpotential and soft terms, it does not exceed the tuning present in the MSSM for equivalent spectra, which is of the order of 10^4.Comment: 23 pages, 3 figures. Some clarifications added to the text, JHEP published versio

Low fine tuning in the MSSM with higgsino dark matter and unification constraints

We examine the issue of fine tuning in the MSSM with GUT-scale boundary conditions. We identify specific unification patterns and mass relations that can lead to a significant lowering of the fine tuning due to gauginos, scalars, and the \mu\ parameter, relative to the simplest unification conditions. We focus on a phenomenologically interesting region that is favored by the Higgs mass and the relic density where the dark matter is a nearly pure higgsino with mass given by \mu~1 TeV while the scalars and gauginos have masses in the multi-TeV regime. There, we find that the fine tuning can be reduced to the level of a few percent. Despite the gluino mass in the ballpark of 2 TeV, resulting mass spectra will be hard to explore at the LHC, but good prospects for detection come from dark matter direct detection experiments. Finally, we demonstrate with a specific example how the conditions and mass relations giving low fine tuning can originate in the context of supergravity and Grand Unified Theories.Comment: 35 pages, 8 figures. Figure 2 added, minor changes. Version published in JHE

Blind Spots for Direct Detection with Simplified DM Models and the LHC

Using the existing simplified model framework, we build several dark matter models which have suppressed spin-independent scattering cross section. We show that the scattering cross section can vanish due to interference effects with models obtained by simple combinations of simplified models. For weakly interacting massive particle (WIMP) masses $\gtrsim$10 GeV, collider limits are usually much weaker than the direct detection limits coming from LUX or XENON100. However, for our model combinations, LHC analyses are more competitive for some parts of the parameter space. The regions with direct detection blind spots can be strongly constrained from the complementary use of several Large Hadron Collider (LHC) searches like mono-jet, jets + missing transverse energy, heavy vector resonance searches, etc. We evaluate the strongest limits for combinations of scalar + vector, "squark" + vector, and scalar + "squark" mediator, and present the LHC 14 TeV projections.Comment: 9 Pages, Talk presented at the conference "Varying Constants and Fundamental Cosmology - VARCOSMOFUN'16" (Szczecin, Poland), Published in Universe (proceedings of VARCOSMOFUN'16