Vernon Barger

Supersymmetric models with the anomaly-mediated supersymmetry (SUSY) breaking (AMSB) form for soft SUSY breaking terms arise in two different settings:(1) extra-dimensional models where SUSY breaking occurs in a sequestered sector, and (2) 4− d models with dynamical SUSY breaking in a hidden sector where scalars gain masses of order the gravitino mass m 3/2, but gaugino masses and trilinear soft terms are assumed to be of the AMSB form. Both models run into serious conflicts with (1) LHC sparticle and Higgs mass constraints,(2) constraints from winolike weakly interacting massive particle dark matter searches, and (3) bounds from naturalness. These conflicts may be avoided by introducing minor changes to the underlying phenomenological models consisting of nonuniversal bulk scalar Higgs masses and A terms, providing a setting for natural anomaly mediation (nAMSB). In nAMSB, the wino is …

Supersymmetric models with a strongly interacting superconformal hidden sector (HS) may drive soft SUSY breaking scalar masses, bilinear soft term B\mu and Higgs combinations m_{H_{u,d}}^2+\mu^2 to small values at some intermediate scale, leading to unique sparticle mass spectra along with possibly diminished finetuning in spite of a large superpotential parameter. We set up a computer code to calculate such spectra, which are then susceptible to a variety of constraints: 1. possible charge-or-color breaking (CCB) minima in the scalar potential, 2. unbounded from below (UFB) scalar potential, 3. improper electroweak symmetry breaking, 4. a charged or sneutrino lightest SUSY particle (LSP), 5. generating m_h~ 125 GeV, 6. consistency with LHC sparticle mass limits, and 7. naturalness. We find this bevy of constraints leaves little or no viable parameter space for the case where hidden sector dynamics dominates MSSM running, even for the case of non-universal gaugino masses. For the case with moderate HS running with comparable MSSM running, and with universal gaugino masses, then the finetuning is ameliorated, but nonetheless remains high. Viable spectra with moderate HS running and with low finetuning and large mu can be found for non-universal gaugino masses.

In natural supersymmetric models defined by no worse than a part in thirty electroweak fine-tuning, winos and binos are generically expected to be much heavier than Higgsinos. Moreover, the splitting between the Higgsinos is expected to be small, so that the visible decay products of the heavier Higgsinos are soft, rendering the Higgsinos quasi-invisible at the LHC. Within the natural supersymmetry (SUSY) framework, heavy electroweak gauginos decay to W, Z or h bosons plus Higgsinos in the ratio∼ 2∶ 1∶ 1, respectively. This is in sharp contrast to models with a binolike lightest superpartner and very heavy Higgsinos, where the charged (neutral) wino essentially always decays to a W (h) boson and an invisible bino. Wino pair production at the LHC, in natural SUSY, thus leads to V V, V h and h h+ E T final states (V= W, Z) where, for TeV scale winos, the vector bosons and h daughters are considerably …

Superstring flux compactifications can stabilize all moduli while leading to an enormous number of vacua solutions, each leading to different 4−d laws of physics. While the string landscape provides at present the only plausible explanation for the size of the cosmological constant, it may also predict the form of weak scale supersymmetry which is expected to emerge. Rather general arguments suggest a power-law draw to large soft terms, but these are subject to an anthropic selection of a not-too-large value for the weak scale. The combined selection allows one to compute relative probabilities for the emergence of supersymmetric models from the landscape. Models with weak scale naturalness appear most likely to emerge since they have the largest parameter space on the landscape. For finetuned models such as high-scale SUSY or split SUSY, the required weak scale finetuning shrinks their parameter space to tiny volumes, making them much less likely to appear compared to natural models. Probability distributions for sparticle and Higgs masses from natural models show a preference for Higgs mass mh∼125 GeV, with sparticles typically beyond the present LHC limits, in accord with data. From these considerations, we briefly describe how natural SUSY is expected to be revealed at future LHC upgrades. This article is a contribution to the Special Edition of the journal Entropy, honoring Paul Frampton on his 80th birthday.

The total cross section of the process μ− μ+→ ν μ ν¯ μ t t¯ H has strong dependence on the CP phase ξ of the top Yukawa coupling, where the ratio of ξ= π and ξ= 0 (SM) grows to 670 at s= 30 TeV, 3400 at 100 TeV. We study the cause of the strong energy dependence and identify its origin as the (E/m W) 2 growth of the weak boson fusion sub-amplitudes, W L− W L+→ t t¯ H, with the two W's are longitudinally polarized. We repeat the study in the SMEFT framework where EW gauge invariance is manifest and find that the highest energy cross section is reduced to a quarter of the complex top Yukawa model result, with the same energy power. By applying the Goldstone boson (GB) equivalence theorem, we identify the origin of this strong energy growth of the SMEFT amplitudes as associated with the dimension-6 π− π+ t t H vertex, where π±denotes the GB of W±. We obtain the unitarity bound on the coefficient of …

We continue our examination of prospects for the discovery of heavy Higgs bosons of natural SUSY (natSUSY) models at the high luminosity LHC (HL-LHC), this time focusing on charged Higgs bosons. In natSUSY, higgsinos are expected at the few hundred GeV scale whilst electroweak gauginos inhabit the TeV scale and the heavy Higgs bosons, H, A and H± could range up tens of TeV without jeopardizing naturalness. For TeV-scale heavy SUSY Higgs bosons H, A and H±, as currently required by LHC searches, SUSY decays into gaugino plus higgsino can dominate H± decays provided these decays are kinematically accessible. The visible decay products of higgsinos are soft making them largely invisible, whilst the gauginos decay to W, Z or h plus missing transverse energy (ET). Charged Higgs bosons are dominantly produced at LHC14 via the parton subprocess, gb→H±t. In this paper, we examine the viability of observing signatures from H±→τν, H±→tb and H±→W,Z,h+ET events produced in association with a top quark at the HL-LHC over large Standard Model (SM) backgrounds from (mainly) tt¯, tt¯V and tt¯h production (where V=W,Z). We find that the greatest reach is found via the SM H±(→τν)+t channel with a subdominant contribution from the H±(→tb)+t channel. Unlike for neutral Higgs searches, the SUSY decay modes appear to be unimportant for H± searches at the HL-LHC. We delineate regions of the mA vs. tanβ plane, mostly around mA∼ 1–2 TeV, where signals from charged Higgs bosons would serve to confirm signals of a heavy, neutral Higgs boson at the 5σ level or, alternatively, to exclude heavy Higgs bosons at the …

The supersymmetrized DFSZ axion model is especially compelling in that it contains 1. the SUSY solution to the gauge hierarchy problem, 2. the Peccei-Quinn (PQ) solution to the strong CP problem and 3. the Kim-Nilles solution to the SUSY μ problem. In a string setting, where a discrete R-symmetry ( for example) may emerge from the compactification process, a high-quality accidental axion (accion) can emerge from the accidental, approximate remnant global U (1) PQ symmetry where the decay constant f a is linked to the SUSY breaking scale, and is within the cosmological sweet zone. In this setup, one also expects the presence of stringy remnant moduli fields ϕ i. Here, we consider the situation of a single light modulus ϕ coupled to the PQMSSM in the early universe, with mixed axion plus higgsino-like WIMP dark matter. We evaluate dark matter and dark radiation production via nine coupled Boltzmann …

We propose a solution to the recent W mass measurement by embedding the Standard Model within E 6 models. The presence of a new U (1) group shifts the W boson mass at the tree level and introduces a new gauge boson Z′ which has been searched for at collider experiments. In this article, we identify the parameter space that explains the new W mass measurement and is consistent with current experimental Z′ searches. As U (1) extensions can be accommodated in supersymmetric models, we also consider the supersymmetric scenario of E 6 models, and show that a 125 GeV Higgs may be easily achieved in such settings.