Digging deeper for new physics in the LHC data

Abstract

In this paper, we describe a novel, model-independent technique of "rectangular aggregations" for mining the LHC data for hints of new physics. A typical (CMS) search now has hundreds of signal regions, which can obscure potentially interesting anomalies. Applying our technique to the two CMS jets+MET SUSY searches, we identify a set of previously overlooked ∼ 3σ excesses. Among these, four excesses survive tests of inter-and intra-search compatibility, and two are especially interesting: they are largely overlapping between the jets+MET searches and are characterized by low jet multiplicity, zero b-jets, and low MET and H T . We find that resonant color-triplet production decaying to a quark plus an invisible particle provides an excellent fit to these two excesses and all other data -including the ATLAS jets+MET search, which actually sees a correlated excess. We discuss the additional constraints coming from dijet resonance searches, monojet searches and pair production. Based on these results, we believe the wide-spread view that the LHC data contains no interesting excesses is greatly exaggerated.

An update on the LHC monojet excess

“…We dubbed this the "monojet excess" because it is characterized by low jet multiplicity, no b-jets, and low / E T and H T . We found that the anomaly's kinematic distributions could not be well-fit by supersymmetry-like pair production of colored particles, or in simplified models for dark matter pair production [1]. Instead, a good fit was obtained using a colored scalar φ, resonantly produced through couplings to quarks, and decaying to an invisible massive Dirac fermion ψ and a Standard Model quark (the "mono-φ" model), see Fig.…”

“…1.To avoid decays of the ψ back to visible states, its Dirac partner ψ can be coupled to invisible states N andÑ . The interaction Lagrangian for the minimal model is [1] −L ⊇ gφ * q c i ψ+λφq c i q c j +m ψ ψψ +m 2 φ |φ| 2 +g ψ NÑ +h.c.(1) Here, the q i are the right-handed quarks. The scalar φ is a color-triplet, and its charge can be + 2 3 or − 1 3 .…”

“…In a previous work [1], we developed a "rectangular aggregation" technique which attempted to overcome these biases by combining signal regions in a more modelindependent way. This was based on the simple observation that any signal can populate multiple neighboring bins, and therefore aggregating signal regions within larger kinematic ranges can extract information about underlying excesses without making assumptions about a specific signal model.…”

“…The anomaly is in some tension with null results from the CMS dark matter+jets exotica search [6] (CMS048), but a production cross section on the order of 0.5 pb can evade the 95%CL limits from that search, while still maintaining a local 3σ preference for signal over background in CMS036 and ATLAS022. 1 This letter serves as an update to the original analysis, containing three new points concerning the monojet excess:…”

“…(We are following standard CMS terminology, see e.g. [8]) The pre-fit backgrounds are the simple aggregation of the background counts and the sum of covariance matrix for the bins populated by signal (as detailed in [1]). The post-fit values refer to a combined fit of all the signal regions in the presence of a new-physics signal which only populates a specific subset of all the bins.…”