CMS-PAS-EXO-19-018

CMS-PAS-EXO-19-018
Search for a narrow resonance decaying to a pair of muons in proton-proton collisions at 13 TeV
CMS Collaboration
August 2019

Abstract: A search is presented for a narrow resonance decaying to a pair of muons using 13 TeV proton-proton collision data recorded by the CMS experiment at the CERN LHC. The search in the 45-75 and 110-200 GeV resonance mass ranges uses fully reconstructed event data, corresponding to an integrated luminosity of 137 fb$^{-1}$. The search in the 11.5-45.0 GeV mass range uses 96.6 fb$^{-1}$ of data collected using a dedicated set of high rate dimuon triggers with low thresholds, which store a reduced amount of trigger level information. No significant resonant peaks are observed. The search sets the strongest constraints on a hypothetical dark photon heavier than 11.5 GeV.
Links: CDS record (PDF) ; CADI line (restricted) ; These preliminary results are superseded in this paper, PRL 124 (2020) 131802. The superseded preliminary plots can be found here.

Figures	Summary	References	CMS Publications

Figures
png pdf	Figure 1: Dimuon invariant mass distributions of events selected with the standard and scouting dimuon triggers. Events are required to pass all the selection requirements. The distribution shown in red corresponds to the data collected using the standard triggers, corresponding to a total integrated luminosity of 137 fb$^{-1}$. The distribution shown in green corresponds to the data collected using the scouting muon triggers, corresponding to a total integrated luminosity of 96.6 fb$^{-1}$. The inset figure shows the dimuon mass distribution of events in the barrel category in the mass range 23.9-26.1 GeV. A function describing the background is fit to this data and a 25 GeV dark photon signal corresponding to $\epsilon ^{2} = 4 \times 10^{-5}$ is added.
png pdf	Figure 2: Expected and observed 95% CL upper limits on the product of the signal cross section ($\sigma $), branching fraction to a pair of muons (B), and acceptance (A) as a function of the mass of a narrow resonance. Results obtained using scouting data are to the left of the vertical dashed purple line, whereas results obtained using data from the standard triggers are to the right.
png pdf	Figure 3: Expected and observed 90% CL upper limits on $\epsilon ^{2}$ as a function of the $\mathrm {Z}_{\mathrm {D}}$ mass. Results obtained using scouting data are to the left of the vertical dashed purple line, whereas results obtained using data from the standard triggers are to the right. Limits from the dark photon search performed by the LHCb Collaboration [9] are shown in red, and 95% CL constraints from the measurements of the electroweak observables, are shown in light blue [4].

Summary

We have presented a search for a narrow resonance decaying to a pair of muons using proton-proton collision data recorded by the CMS experiment at $\sqrt{s} = $ 13 TeV. The search in the 45-75 and 110-200 GeV resonance mass ranges uses fully reconstructed data, containing a pair of muons with transverse momenta greater than 20 and 10 GeV, and corresponding to an integrated luminosity of 137 fb$^{-1}$. The search in the resonance mass range of 11.5-45.0 GeV is performed using data collected with a set of high rate dimuon triggers, corresponding to an integrated luminosity of 96.6 fb$^{-1}$. This is the first search that uses data with reduced trigger level muon information, collected with dimuon scouting triggers that have significantly lower transverse momentum thresholds compared to the ones used to collect data for complete reconstruction. The data are found to be consistent with the background prediction. The search sets the strongest constraints to date on the kinetic mixing coefficient of a dark photon with mass greater than 11.5 GeV.

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