Search for dark matter and large extra dimensions in monojet events in pp collisions at sqrt(s) = 7 TeV

TL;DR

This CMS study searches for new physics in events with a high-pT jet and missing transverse momentum at √s = 7 TeV, using 5.0 fb^-1 of data to probe dark matter production via a heavy mediator and large extra dimensions in ADD. Signal models are explored with MadGraph+Pythia6 (DM) and Pythia8 (ADD), while dominant SM backgrounds are constrained with data-driven methods exploiting Z→μμ and W→μν control samples. No excess is observed; the results yield 90% CL limits on DM–nucleon cross sections for spin-dependent and spin-independent interactions, with strongest low-mass spin-independent constraints and broad spin-dependent coverage, plus improved MD limits for ADD. The findings provide complementary collider constraints to direct/indirect detection and advance the monojet channel’s sensitivity to light DM and extra-dimensional scenarios.

Abstract

A search has been made for events containing an energetic jet and an imbalance in transverse momentum using a data sample of pp collisions at a center-of-mass energy of 7 TeV. This signature is common to both dark matter and extra dimensions models. The data were collected by the CMS detector at the LHC and correspond to an integrated luminosity of 5.0 inverse femtobarns. The number of observed events is consistent with the standard model expectation. Constraints on the dark matter-nucleon scattering cross sections are determined for both spin-independent and spin-dependent interaction models. For the spin-independent model, these are the most constraining limits for a dark matter particle with mass below 3.5 GeV, a region unexplored by direct detection experiments. For the spin-dependent model, these are the most stringent constraints over the 0.1-200 GeV mass range. The constraints on the Arkani-Hamed, Dimopoulos, and Dvali model parameter MD determined as a function of the number of extra dimensions are also an improvement over the previous results.

Figures (5)

• Figure 1: The distribution of (a) $E_{\mathrm{T}}^{\text{miss}}$ and (b) $p_{\mathrm{T}}\xspace(\,\mathrm{j}_1)$ for data (black full points with error bars) and simulation (histograms) for $E_{\mathrm{T}}^{\text{miss}}\xspace > 350$${\,\text{Ge\spaceV\space/\space}c}$ after the full event selection criteria are applied. The ${Z}({gn}{gn})$+jets and ${W}$+jets backgrounds are normalized to their estimates from data. An example of a dark matter signal (for axial-vector couplings and $M_{\chi} = 1$${\,\text{Ge\spaceV\space/\space}c^\text{2}}$) is shown as a dashed blue histogram and an ADD signal (with ${M_\mathrm{D}}\xspace=2\,\text{Te\spaceV}\xspace$, $\delta=3$) is shown as a dotted red histogram.
• Figure 2: The dimuon invariant mass distribution in the dimuon control sample in data (black full points with error bars) and simulation (histogram) for $60 < M_{\mu\mu} < 120$${\,\text{Ge\spaceV\space/\space}c^\text{2}}$. The MC prediction has been normalized to the data yields. There is no significant non-${Z}$ background.
• Figure 3: The transverse mass distribution $M_{\rm T}$ in the single muon data control sample and MC predictions for $\mathrm{W}\xspace (\mu \nu )$, ${\rm t\bar{t}}$, ${Z}\xspace (\mu \mu)$, and single top-quark production. The MC predictions have been normalized to the data yields. Data are dominated by $\mathrm{W}\xspace (\mu \nu )$ events.
• Figure 4: Comparison of the 90% CL upper limits on the dark matter-nucleon scattering cross section versus mass of dark matter particle for the (left) spin-independent and (right) spin-dependent models with results from CMS using monophoton signature CMSMonophotons, CDF Aaltonen:2012jb, XENON100 bib:XENON100, CoGeNT bib:COGENT, COUPPbib:COUPP, CDMS II bib:CDMSII2011bib:CDMSII2010, Picasso bib:PICASSO, SIMPLE SIMPLE1, IceCube IceCube:2011aj, and Super-K SUPERK collaborations.
• Figure 5: Comparison of lower limits on $M_D$ versus the number of extra dimensions with ATLAS bib:ATLASMonoJet, LEP bib:ALEPHbib:OPALbib:DELPHIbib:L3, CDF bib:CDFMonoPhoton, and D0 bib:D0MonoPhoton.