# Scalar Dark Energy Field coupling to the SM¶

Jon Butterworth, Christoph Englert, Peter Richardson, Michael Spannowsky

A study of the model which is introduced and discussed by Brax, Burrage, Englert and Spannowsky in [118]. A neutral scalar dark energy field of mass $$M_\phi$$ couples to Standard Model particles via various Effective Field Theory (EFT) operators which are suppressed by powers of a scale parameter $$M_{SCALE}$$.

Following [118], we concentrate on the couplings $$C_1$$ and $$C_2$$ which appear in front on the leading EFT operators, setting the others to zero. This means that $$\phi$$ is pair-produced and stable, so the dominant signatures are expected to involve missing transverse energy.

First setting $$C_1 = C_2 = 1$$, we scan in $$M_\phi$$ and $$M_{SCALE}$$.

Heatmap and contour for all available 13 TeV data in Rivet 2.7 as of 4/6/2019:

The cut-off in sensitivity is independent of $$M_\phi$$ over this range, at $$M_{SCALE} \approx 1$$ TeV, slightly higher than the 820 GeV or so estimated in [118] for $$C_2 = 1$$ using 8 TeV monojet data. In the current scan the most sensitive measurement is the ATLAS missing energy ratio [7], as expected.

We then set $$M_\phi = 0.1$$ GeV, the nominal value chosen in [118], and setting $$C_2 = 1 - C_1$$, we scan in $$C_1$$ and $$M_{SCALE}$$.

Heatmap and contour for all available 7,8 and 13 TeV data in Rivet 2.7 as of 4/6/2019:

Again the results are comparable to [118], with a cut off in sensitivity at around 200 GeV for $$C_1 = 1, C_2 = 0$$ and around 1 TeV for $$C_1 = 0, C_2 = 1$$. And again, the missing energy measurement drives the sensitivity, although many other measurements have sensitivity up $$M_{SCALE}$$ of a few 100 GeV.

This model was also studied in [24].

The model files are available in the directory Standard_Model_cosmo_UFO here .

This research was supported by the Munich Institute for Astro- and Particle Physics (MIAPP) of the DFG cluster of excellence “Origin and Structure of the Universe (2019)