# Scalar Dark Energy Field coupling to the SM¶

A study of the model which is introduced and discussed by Brax, Burrage, Englert and Spannowsky in [101]. 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 [101], 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 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 [101] for \(C_2 = 1\) using 8 TeV monojet data. In the current scan the most sensitive measurement is the ATLAS missing energy ratio [6], as expected.

We then set \(M_\phi = 0.1\) GeV, the nominal value chosen in [101], 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 as of 4/6/2019:

Again the results are comparable to [101], 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 [14].

*Jon Butterworth, thanks to Christoph Englert, Peter Richardson, Michael Spannowsky*

*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)*