Casting Light on BSM Physics with SM Standard Candles

TL;DR

The paper proposes retooling SM standard candles, notably the $W^+W^-$ cross section, to constrain light electroweak states such as sleptons that evade traditional LEP and LHC searches, thereby bridging a gap in EW-scale sensitivity. It develops a slepton-based simplified model and shows that WW measurements can place bounds on sleptons, closing parts of the LEP-LHC gap and, in certain parameter regions, even improve agreement between data and the SM prediction. The authors connect these collider constraints to broader issues, including Bino-like dark matter relic density and the muon g-2 anomaly, highlighting regions where a single slepton/Bino parameter space can address multiple clues. This work illustrates the value of fully exploiting SM EW processes as probes of new physics and motivates continued use of WW and other standard candles for EW-scale BSM exploration.

Abstract

The Standard Model (SM) has had resounding success in describing almost every measurement performed by the ATLAS and CMS experiments. In particular, these experiments have put many beyond the SM models of natural Electroweak Symmetry Breaking into tension with the data. It is therefore remarkable that it is still the LEP experiment, and not the LHC, which often sets the gold standard for understanding the possibility of new color-neutral states at the electroweak (EW) scale. Recently, ATLAS and CMS have started to push beyond LEP in bounding heavy new EW states, but a gap between the exclusions of LEP and the LHC typically remains. In this paper we show that measurements of SM Standard Candles can be repurposed to set entirely complementary constraints on new physics. To demonstrate this, we use WW cross section measurements to set bounds on a set of slepton-based simplified models which fill in the gaps left by LEP and dedicated LHC searches. Having demonstrated the sensitivity of the WW measurement to light sleptons, we also find regions where sleptons can improve the fit of the data compared to the NLO SM WW prediction alone. Remarkably, in those regions the sleptons also provide for the right relic-density of Bino-like Dark Matter and provide an explanation for the longstanding 3 sigma discrepancy in the measurement of (g-2)_μ.