Kinematical variables towards new dynamics at the LHC

TL;DR

The paper introduces kinematic variables $M_R$ and $M_{R^*}$, along with dimensionless razor quantities $R$ and $R^*$, to identify and characterize pair-produced heavy states decaying to visible and invisible particles at the LHC. By moving to frame-dependent constructions (R-frame and, when needed, R*-frames) and exploiting boost invariance, the authors show how these variables reveal mass-difference scales and suppress Standard Model backgrounds across multiple final states, including SUSY dijet + MET and Higgs decays to WW. The framework provides a pathway to both discovery and subsequent mass spectroscopy through feature peaks near $M_{\Delta}$ and related combinations, while remaining robust against detector effects and mis-measurements. The work outlines generalizations to unequal masses, multi-object final states, and ill-defined boost configurations, broadening applicability to diverse new-physics scenarios at the LHC.

Abstract

At the LHC, many new physics signatures feature the pair-production of massive particles with subsequent direct or cascading decays to weakly-interacting particles, such as SUSY scenarios with conserved conserved R-parity or $H \to W(\ellν)W(\ellν)$. We present a set of dimension-less variables that can assist the early discovery of processes of this type in conjunction with a set of variables with mass dimension that will expedite the characterization of these processes.

Figures (11)

• Figure 1: Distribution of $\gamma_{CM}$ for $q\bar{q}$-like and $gg$-like production at $\sqrt{s} = 14~\mathrm{TeV}$ for different values of $M_{G}$.
• Figure 2: Distribution of $M_{R}$, in units of $\gamma_{CM}M_{\Delta}$, for different values of $\gamma_{CM}$. Distributions are normalized such that their maximum value is equal to one.
• Figure 3: Distribution of $M_{R}$, in units of $M_{\Delta}\sqrt{1+\delta}$, for different values of $\delta$. Distributions are normalized such that the maximum value is equal to 1.
• Figure 4: Distribution of $M_{R}$ when one (left) or both (right) of the particles $G_{i}$ decays to an intermediate particle $S_{i}$ with mass $M_{S} = M_{G}(1-\delta)$, for different values of $\delta$. Distributions are normalized such that the maximum value is equal to 1
• Figure 5: Distribution of $M_{R}$ for the di-lepton final state in $H\to WW$ as a function of $M_{H}$, where we have made the approximations $p_{T}^{H} = 0$ and neglected spin-correlations.