CMS-PAS-EXO-19-004

CMS-PAS-EXO-19-004
Search for dijet resonances in events with three jets from proton-proton collisions at $\sqrt{s}= $ 13 TeV
CMS Collaboration
August 2019

Abstract: A search for a narrow resonance, with a mass between 350 and 700 GeV and decaying into a pair of jets, is performed in proton-proton collisions with at least three jets in the final state. The data sample corresponds to an integrated luminosity of 18.3 fb$^{-1}$ collected at $\sqrt{s}= $ 13 TeV with the CMS detector. Data are collected with a technique known as "data scouting", in which the events are reconstructed, selected, and recorded at a high rate in a compact form by the high-level trigger. The three-jet final state provides sensitivity to lower values of the dijet mass than in previous searches using the data scouting technique. The spectrum of the dijet invariant mass, from the two jets with largest transverse momenta in the event, is searched for a bump arising from a dijet resonance. No significant excess is found and 95% confidence level upper limits are presented on the production cross section of narrow resonances. The corresponding upper limits on the coupling, of a vector particle interacting only with quarks, is between 0.10 and 0.15 depending on the resonance mass.
Links: CDS record (PDF) ; CADI line (restricted) ; These preliminary results are superseded in this paper, PLB 805 (2020) 135448. The superseded preliminary plots can be found here.

Figures	Summary	Additional Figures & Tables	References	CMS Publications

Figures
png pdf	Figure 1: Dijet mass spectra (points) compared to a fitted parameterization of the background (solid curve) where the fit is performed in the range 290 $ < m_{jj} < $ 1000 GeV. The dashed lines represent the dijet mass distribution from 700, 550, and 400 GeV resonance signals excluded at 95% CL by this analysis.
png pdf	Figure 2: The 95% CL upper limits on the product of the cross section, branching fraction, and acceptance as a function of resonance mass for a vector particle decaying into a pair of jets. The acceptance is calculated for the analysis selection, namely three widejets with $ {p_{\mathrm {T}}} > $ 72 GeV and $\|\eta \| < 2.5$, and $\|\eta _1 - \eta _2\| < $ 1.1. The observed limits (solid), expected limits (dashed) and their variation at the 1 and 2 standard deviation levels (shaded bands) are shown. The dotted horizontal line shows the expected cross section times acceptance for a DM mediator (see text).
png pdf	Figure 3: The 95% CL upper limits on the universal quark coupling $g^{\prime}_q$ as a function of resonance mass for a vector resonance that only couples to quarks. The observed limits (solid), expected limits (dashed) and their variation at the 1 and 2 standard deviation levels (shaded bands) are shown. The dotted horizontal line shows the coupling strength for which the cross section for dijet production in this model is the same as for a DM mediator (see text).

Summary

A search for narrow vector resonances of mass between 350 and 700 GeV decaying into two jets has been performed in proton-proton collisions at $\sqrt{s} = $ 13 TeV. The search used 18.3 fb$^{-1}$ of integrated luminosity collected with the CMS experiment. Data have been taken using a special technique, data scouting, for which the trigger had the lowest possible threshold on the sum of the transverse momenta of the jets in the event. Events with three-jets are used to satisfy the trigger threshold at a lower dijet mass than is possible with only two high ${p_{\mathrm{T}}}$ jets in the final state. Jets with $\Delta R < $ 1.1 have been merged into wide jets. The dijet mass has been calculated from the two leading wide jets with highest transverse momenta. Events have been selected by requiring three wide jets with ${p_{\mathrm{T}}} > $ 72 GeV, reconstructed from jets within $ |\eta| < $ 2.5, and requiring the two wide jets forming the dijet satisfy $|\eta_1 - \eta_2| < $ 1.1. The background shape has been fitted by using a parametric function, while the signal shape has been obtained using simulations. The dijet mass distribution has shown no significant peak in the range 290 $ < m_{jj} < $ 1000 GeV and therefore upper limits have been set on the production cross section of a signal. We have set 95% CL upper limits on the coupling to quarks $g^{\prime}_q$ in the range 0.10 - 0.15 for a vector particle interacting only with quarks. This search excludes a simplified model of interactions between quarks and dark matter particles of mass 1 GeV mediated by a vector boson with coupling strengths of, respectively, $g_{q}=$ 0.25 and $g_{DM}=$ 1, and mass between 350 and 700 GeV. Among the searches for resonances decaying into light jets, this search sets the most stringent upper limits on coupling to quarks of vector particles with a mass between 350 and 450 GeV.

Additional Figures
png pdf	Additional Figure 1: Acceptance for a vector resonance decaying into a jet pair as a function of the resonance mass The acceptance is calculated for the analysis selection, namely three widejets with ${p_{\mathrm {T}}} > $ 72 GeV and $\|\eta \| < $ 2.5, and $\|\eta _1 - \eta _2\| < $ 1.1. The errors are dominated by the uncertainties on the parton shower modeling used in signal simulations.
png pdf	Additional Figure 2: Comparison of the dijet mass distribution of the nominal selection (black), control selection without correction (red), and control selection with correction (blue) for data (solid histograms) and a simulation of a signal from a resonance with a mass of 400 GeV (dashed histograms). The correction, applied as a function of the product of the two largest jet transverse momenta in the event, is obtained as the ratio of the numbers of events passing the signal selection to those passing the control selection. For ease of readability, the dijet mass distributions of the signal have been scaled by an arbitrary factor. The bottom plot shows the relative difference between the dijet mass distributions of the data from the control and nominal selections. The yield of the uncorrected control selection for data is 95.7% of the nominal selection. The overlap between the two data selections is about 35% of the nominal selection. The yield of the uncorrected control selection for signal simulation of a 400- GeV resonance is about 50% of the nominal selection.

Additional Tables
png pdf	Additional Table 1: Fraction of data and simulated signal events passing different stages of the analysis selection. The selection corresponding to each line includes the selection of the upper lines.

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