CMS-EXO-14-005

CMS-EXO-14-005 ; CERN-EP-2016-090
Search for narrow resonances in dijet final states at $\sqrt{s}= $ 8 TeV with the novel CMS technique of data scouting
CMS Collaboration
30 April 2016
Phys. Rev. Lett. 117 (2016) 031802
Abstract: A search for narrow resonances decaying into dijet final states is performed on data from proton-proton collisions at a center-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 18.8 fb$^{-1}$. The data were collected with the CMS detector using a novel technique called data scouting, in which the information associated with these selected events is much reduced, permitting collection of larger data samples. This technique enables CMS to record events containing jets at a rate of 1 kHz, by collecting the data from the high-level-trigger system. In this way, the sensitivity to low-mass resonances is increased significantly, allowing previously inaccessible couplings of new resonances to quarks and gluons to be probed. The resulting dijet mass distribution yields no evidence of narrow resonances. Upper limits are presented on the resonance cross sections as a function of mass, and compared with a variety of models predicting narrow resonances. The limits are translated into upper limits on the coupling of a leptophobic resonance $\mathrm{ Z }'_B$ to quarks, improving on the results obtained by previous experiments for the mass range from 500 to 800 GeV.
Links: e-print arXiv:1604.08907 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; CADI line (restricted) ;

Figures & Tables	Summary	References	CMS Publications

Figures
png pdf	Figure 1: The reconstructed dijet mass distribution (black points) fitted with the function of Eq. 1 (red solid line). The bottom panel compares the data and the fit result, normalized by the statistical uncertainty in the data, for each bin. The predicted distributions of narrow resonance signals for a hypothetical leptophobic resonance $\mathrm{ Z }'_B$ with two different mass and coupling values are shown in both panels (dash-dotted curves). This dijet mass distribution complements that observed at higher mass [19].
png pdf	Figure 2: The reconstructed dijet mass distributions for simulated RS gravitons decaying to quark-antiquark, excited quarks decaying to quark-gluon, and RS gravitons decaying to gluon-gluon, for a resonance mass of 900 GeV.
png pdf	Figure 3: Observed 95% CL upper limits on $\sigma \mathcal {B}A$ for a narrow resonance decaying to gluon-gluon final states (open circles), quark-gluon final states (solid circles), and quark-quark final states (open triangles) compared with theoretical predictions for various resonance models.
png pdf	Figure 4: Observed 95% CL upper limits on the coupling $g_B$ of a hypothetical leptophobic resonance $\mathrm{ Z }'_B \to \mathrm{ q } \mathrm{ \bar{q} } $ [21] as a function of its mass. The results from this study are compared to results obtained with similar searches at different collider energies [21,14].

Tables
png pdf	Table 1: Observed upper limits at 95% CL on $\sigma \mathcal {B}A$ for resonances decaying to $\mathrm{ q } \mathrm{ q } $, $\mathrm{ q } \mathrm{g} $, and $\mathrm{g} \mathrm{g} $ final states as a function of the resonance mass.

Summary

In summary, a search for narrow resonances decaying into two jets was performed using data from proton-proton collisions recorded by the CMS experiment at $\sqrt{s}= $ 8 TeV, corresponding to an integrated luminosity of 18.8 fb$^{-1}$. The novel technique of data scouting was used; by reducing the information stored per event, multijet events could be collected in sufficiently large samples that a sensitive search for dijet resonances down to masses as low as 500 GeV was possible. No evidence for a narrow resonance is found. Model-independent upper limits on production cross sections are derived for quark-quark, quark-gluon, and gluon-gluon resonances. Based on these results, new limits are set on an extensive selection of narrow $s$-channel resonances over mass ranges not excluded by previous searches at hadron colliders. Bounds on the coupling of a hypothetical leptophobic resonance decaying to quark-antiquark are also provided, as a function of the resonance mass. The limits obtained are the most stringent to date in the dijet final state for narrow resonance masses between about 500 and 800 GeV.

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