Exploiting jet binning to identify the initial state of high-mass resonances

TL;DR

The work introduces a model-independent jet-veto strategy to determine the initial-state partons responsible for producing a new high-mass color-singlet resonance by classifying events into 0-jet and $\ge 1$-jet samples using a low $p_T^{\rm cut}$ threshold and SCET-based resummation. The key idea is that the ratio $\sigma_0(p_T^{\rm cut})/\sigma_{\ge 1}(p_T^{\rm cut})$ is highly sensitive to whether the production is gluon- or quark-initiated, while being largely insensitive to the detailed decay of the resonance; the EFT description at scale $p_T^{\rm cut}$ provides robust, model-independent predictions with controlled uncertainties. The authors demonstrate the method for a $m_X=750$ GeV scalar and show that, with realistic experimental uncertainties (and an inclusive cross-section uncertainty around $20\%$), one can distinguish among $u$, $c$, $b$, and gluon initial states and constrain the corresponding Wilson coefficients $C_i$ via a combined fit. This approach enables an early, theoretically clean determination of the production mechanism for new resonances at the LHC and can be extended to photoproduction as well.

Abstract

If a new high-mass resonance is discovered at the Large Hadron Collider, model-independent techniques to identify the production mechanism will be crucial to understand its nature and effective couplings to Standard Model particles. We present a powerful and model-independent method to infer the initial state in the production of any high-mass color-singlet system by using a tight veto on accompanying hadronic jets to divide the data into two mutually exclusive event samples (jet bins). For a resonance of several hundred GeV, the jet binning cut needed to discriminate quark and gluon initial states is in the experimentally accessible range of several tens of GeV. It also yields comparable cross sections for both bins, making this method viable already with the small event samples available shortly after a discovery. Theoretically, the method is made feasible by utilizing an effective field theory setup to compute the jet cut dependence precisely and model independently and to systematically control all sources of theoretical uncertainties in the jet binning, as well as their correlations. We use a 750 GeV scalar resonance as an example to demonstrate the viability of our method.

Figures (2)

• Figure 1: The ratio $\sigma_{0}(p_T^{\rm cut})/\sigma_{\geq 1}(p_T^{\rm cut})$ for $u$ (red), $c$ (yellow), $b$ quarks (blue) and gluons (green). The lines show the central values and the bands the theoretical uncertainties.
• Figure 2: $\Delta\chi^2=1$-contours for various scenarios. (a) gluon signal, (b) mixed gluon/$u$-quark signal, (c) $u$-quark signal, (d) $b$-quark signal, (e) $c$-quark signal, (f) gluon signal. The constraints from $\sigma_{0}$ and $\sigma_{\ge1}$ are shown by the blue and green bands, respectively. The combined constraint from both are shown by the orange/yellow regions. The inner darker regions correspond to theory uncertainties only, while the full lighter bands include both theory and assumed experimental uncertainties.