The pMSSM10 after LHC run 1

100

169

A summary of the constraints from the ATLAS experiment on R-parityconserving supersymmetry is presented. Results from 22 separate ATLAS searches are considered, each based on analysis of up to 20.3 fb −1 of proton-proton collision data at centre-of-mass energies of √ s = 7 and 8 TeV at the Large Hadron Collider. The results are interpreted in the context of the 19-parameter phenomenological minimal supersymmetric standard model, in which the lightest supersymmetric particle is a neutralino, taking into account constraints from previous precision electroweak and flavour measurements as well as from dark matter related measurements. The results are presented in terms of constraints on supersymmetric particle masses and are compared to limits from simplified models. The impact of ATLAS searches on parameters such as the dark matter relic density, the couplings of the observed Higgs boson, and the degree of electroweak fine-tuning is also shown. Spectra for surviving supersymmetry model points with low fine-tunings are presented. The ATLAS collaboration 58 Keywords: Hadron-Hadron Scattering IntroductionDuring the first run of the Large Hadron Collider (LHC), the ATLAS [1] and CMS [2] Collaborations performed a wide range of searches for supersymmetry (SUSY) [3][4][5][6][7][8][9][10][11], using proton-proton (pp) collision data at centre-of-mass energies ( √ s) of 7 and 8 TeV. SUSY, a theoretically favoured framework for extending the Standard Model (SM), is able to address some of its unanswered questions, particularly the hierarchy problem [12][13][14][15], which is related to the fine-tuning needed to obtain the correct mass for the observed Higgs boson. SUSY can also provide credible dark matter candidates [16,17] and can improve the unification of the electroweak and strong interactions [18][19][20][21][22][23][24][25][26].The minimal supersymmetric extension of the Standard Model (MSSM) [27][28][29][30][31] predicts partners for each of the SM states. It predicts a pair of scalar partners -one for each fermion chirality -for each of the SM quarks and leptons. These spin-zero partner particles are known as squarks (q) and sleptons (˜ ) respectively. In the first two generations the pair of chiral partners is largely unmixed, so the mass states can be labelledẽ L andẽ R , where the L and R subscripts denote the scalar partners of the left-and right-handed Standard Model fermion states respectively. In the third generation of quarks and leptons the mixing between the scalars is larger, and the mixed states are labelled by their mass indices e.g.t 1 and t 2 , wheret 1 is lighter by construction. Each state in the SM gluon colour octet has a spinhalf partner known as a gluinog. There are a total of eight spin-half partners of the electroweak gauge and Higgs bosons: the neutral bino (superpartner of the U(1) gauge field); the winos, which are a charged pair and a neutral particle (superpartners of the W bosons of the SU(2) L gauge fields); and the Higgsinos, which are two neutral particles and a charged pai...

Section: Jhep10(2015)134mentioning

confidence: 99%

Summary of the ATLAS experiment’s sensitivity to supersymmetry after LHC Run 1 — interpreted in the phenomenological MSSM

Aad

Bergeås

Brenner

et al. 2015

100

169

“…Studies in the context of ultraviolet (UV) complete models like the Minimal Supersymmetric Standard Model (MSSM) allow for the most comprehensive combination of experimental data sets [7][8][9][10][11], but it is usually difficult to generalize their results to other models. Effective field theories (EFTs), on the other hand, offer highly modelindependent results, but their applicability is more restricted, especially in high energy…”

Section: Introductionmentioning

confidence: 99%

The coannihilation codex

Baker

Brod

Hedri

et al. 2015

121

We present a general classification of simplified models that lead to dark matter (DM) coannihilation processes of the form DM + X → SM 1 + SM 2 , where X is a coannihilation partner for the DM particle and SM 1 , SM 2 are Standard Model fields. Our classification also encompasses regular DM pair annihilation scenarios if DM and X are identical. Each coannhilation scenario motivates the introduction of a mediating particle M that can either belong to the Standard Model or be a new field, whereby the resulting interactions between the dark sector and the Standard Model are realized as tree-level and dimension-four couplings. We construct a basis of coannihilation models, classified by the SU(3) C × SU(2) L × U(1) Y quantum numbers of DM, X and M. Our main assumptions are that dark matter is an electrically neutral color singlet and that all new particles are either scalars, Dirac or Majorana fermions, or vectors. We illustrate how new scenarios arising from electroweak symmetry breaking effects can be connected to our electroweak symmetric simplified models. We offer a comprehensive discussion of the phenomenological features of our models, encompassing the physics of thermal freeze-out, direct and indirect detection constraints, and in particular searches at the Large Hadron Collider (LHC). Many novel signatures that are not covered in current LHC searches are emphasized, and new and improved LHC analyses tackling these signatures are proposed. We discuss how the coannihilation simplified models can be used to connect results from all classes of experiments in a straightforward and transparent way. This point is illustrated with a detailed discussion of the phenomenology of a particular simplified model featuring leptoquark-mediated dark matter coannihilation.

“…The no-observation of DM is starting to put some pressure on the so-called WIMP Miracle paradigm, which posits that the observed relic abundance can be explained by DM candidates which are weakly interacting massive particles (WIMPs) with masses in the 10s of GeV to a few TeV range (assuming simple 2 → 2 DM annihilation to SM particles and the standard thermal freeze-out mechanism). A growing number of such WIMP models of DM are being strongly constrained by, or at least show tension with the experimental limits, including supersymmetric DM realisations discussed in [3][4][5][6][7][8][9][10][11][12][13][14] as well as other models considered in e.g. [15,16].…”

Section: Jhep06(2017)041mentioning

confidence: 99%

Simplified models of dark matter with a long-lived co-annihilation partner

Khoze

Plascencia

Sakurai

2017

We introduce a new set of simplified models to address the effects of 3-point interactions between the dark matter particle, its dark co-annihilation partner, and the Standard Model degree of freedom, which we take to be the tau lepton. The contributions from dark matter co-annihilation channels are highly relevant for a determination of the correct relic abundance. We investigate these effects as well as the discovery potential for dark matter co-annihilation partners at the LHC. A small mass splitting between the dark matter and its partner is preferred by the co-annihilation mechanism and suggests that the co-annihilation partners may be long-lived (stable or meta-stable) at collider scales. It is argued that such long-lived electrically charged particles can be looked for at the LHC in searches of anomalous charged tracks. This approach and the underlying models provide an alternative/complementarity to the mono-jet and multi-jet based dark matter searches widely used in the context of simplified models with s-channel mediators. We consider four types of simplified models with different particle spins and coupling structures. Some of these models are manifestly gauge invariant and renormalizable, others would ultimately require a UV completion. These can be realised in terms of supersymmetric models in the neutralino-stau co-annihilation regime, as well as models with extra dimensions or composite models.