We consider supersymmetric (SUSY) models wherein the strong CP problem is solved by the Peccei-Quinn (PQ) mechanism with a concommitant axion/axino supermultiplet. We examine R-parity conserving models where the neutralino is the lightest SUSY particle, so that a mixture of neutralinos and axions serve as cold dark matter (a Z 1 CDM). The mixed a Z 1 CDM scenario can match the measured dark matter abundance for SUSY models which typically give too low a value of the usual thermal neutralino abundance, such as models with wino-like or higgsino-like dark matter. The usual thermal neutralino abundance can be greatly enhanced by the decay of thermally-produced axinos (ã) to neutralinos, followed by neutralino re-annihilation at temperatures much lower than freeze-out. In this case, the relic density is usually neutralino dominated, and goes as ∼ (f a /N )/m 3/2 a . If axino decay occurs before neutralino freeze-out, then instead the neutralino abundance can be augmented by relic axions to match the measured abundance. Entropy production from late-time axino decays can diminish the axion abundance, but ultimately not the neutralino abundance. In a Z 1 CDM models, it may be possible to detect both a WIMP and an axion as dark matter relics. We also discuss possible modifications of our results due to production and decay of saxions. In the appendices, we present expressions for the Hubble expansion rate and the axion and neutralino relic densities in radiation, matter and decaying-particle dominated universes.

Radiatively-driven natural supersymmetry (RNS) potentially reconciles the Z and Higgs boson masses close to ∼ 100 GeV with gluinos and squarks lying beyond the TeV scale. Requiring no large cancellations at the electroweak scale in constructing M Z = 91.2 GeV while maintaining a light Higgs scalar with m h ≃ 125 GeV implies a sparticle mass spectrum including light higgsinos with mass ∼ 100 − 300 GeV, electroweak gauginos in the 300 − 1200 GeV range, gluinos at 1 − 4 TeV and top/bottom squarks in the 1-4 TeV range (probably beyond LHC reach), while first/second generation matter scalars can exist in the 5-30 TeV range (far beyond LHC reach). We investigate several characteristic signals for RNS at LHC14. Gluino pair production yields a reach up to mg ∼ 1.7 TeV for 300 fb −1 . Wino pair production -pp → W 2 Z 4 and W 2 W 2 -leads to a unique same-sign diboson (SSdB) signature accompanied by modest jet activity from daughter higgsino decays; this signature provides the best reach up to mg ∼ 2.1 TeV within this framework. Wino pair production also leads to final states with (W Z → 3ℓ) + E miss T as well as 4ℓ + E miss T which give confirmatory signals up to mg ∼ 1.4 TeV. Directly produced light higgsinos yield a clean, soft trilepton signature (due to very low visible energy release) which can be visible, but only for a not-too-small a Z 2 − Z 1 mass gap. The clean SSdB signal -as well as the distinctive mass shape of the dilepton mass distribution from Z 2,3 → Z 1 ℓℓ decays if this is accessible -will mark the presence of light higgsinos which are necessary for natural SUSY. While an e + e − collider operating with √ s ∼ 600 GeV should unequivocally reveal the predicted light higgsinos, the RNS model with m 1/2 1 TeV may elude all LHC14 search strategies even while maintaining a high degree of electroweak naturalness.-1 -

In supersymmetric models with light higgsinos (which are motivated by electroweak naturalness arguments), the direct production of higgsino pairs may be difficult to search for at LHC due to the low visible energy release from their decays. However, the wino pair production reaction) also occurs at substantial rates and leads to final states including equally opposite-sign (OS) and same-sign (SS) diboson production. We propose a novel search channel for LHC14 based on the SS diboson plus missing ET final state which contains only modest jet activity. Assuming gaugino mass unification, and an integrated luminosity > ∼ 100 fb −1 , this search channel provides a reach for SUSY well beyond that from usual gluino pair production.

Abstract:We calculate the relic abundance of mixed axion/neutralino cold dark matter which arises in R-parity conserving supersymmetric (SUSY) models wherein the strong CP problem is solved by the Peccei-Quinn (PQ) mechanism with a concommitant axion/saxion/axino supermultiplet. By numerically solving the coupled Boltzmann equations, we include the combined effects of 1. thermal axino production with cascade decays to a neutralino LSP, 2. thermal saxion production and production via coherent oscillations along with cascade decays and entropy injection, 3. thermal neutralino production and re-annihilation after both axino and saxion decays, 4. gravitino production and decay and 5. axion production both thermally and via oscillations. For SUSY models with too high a standard neutralino thermal abundance, we find the combined effect of SUSY PQ particles is not enough to lower the neutralino abundance down to its measured value, while at the same time respecting bounds on late-decaying neutral particles from BBN. However, models with a standard neutralino underabundance can now be allowed with either neutralino or axion domination of dark matter, and furthermore, these models can allow the PQ breaking scale f a to be pushed up into the 10 14 − 10 15 GeV range, which is where it is typically expected to be in string theory models.

We present the calibration strategy for the 20 kton liquid scintillator central detector of the Jiangmen Underground Neutrino Observatory (JUNO). By utilizing a comprehensive multiple-source and multiple-positional calibration program, in combination with a novel dual calorimetry technique exploiting two independent photosensors and readout systems, we demonstrate that the JUNO central detector can achieve a better than 1% energy linearity and a 3% effective energy resolution, required by the neutrino mass ordering determination.