$R$-Axion at Colliders

We study the effective theory of a generic class of hidden sectors where supersymmetry is broken together with an approximate $R$-symmetry at low energy. The light spectrum contains the gravitino and the pseudo-Nambu-Goldstone boson of the $R$-symmetry, the $R$-axion. We derive new model-independent constraints on the $R$-axion decay constant for $R$-axion masses ranging from GeV to TeV, which are of relevance for hadron colliders, lepton colliders, and $B$ factories. The current bounds allow for the exciting possibility that the first sign of supersymmetry will be the $R$-axion. We point out its most distinctive signals, providing a new experimental handle on the properties of the hidden sector and a solid motivation for searches of axionlike particles.

Figure 1

Shaded areas show LHC8 and LHC13 [34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49], LHCb [50, 51], BABAR [52, 53, 54], and Belle [55] exclusions. Contours show signal strengths at the LHC13 and Higgs and $Z$ boson branching ratios. The tiny area in the lower right corner where $m_a\approx 4\pi f_a$ lies beyond the regime of validity of our effective description.