CMS-EXO-15-009

CMS-EXO-15-009 ; CERN-EP-2017-047
Search for new physics with dijet angular distributions in proton-proton collisions at $\sqrt{s} = $ 13 TeV
CMS Collaboration
29 March 2017
JHEP 07 (2017) 013
Abstract: A search is presented for extra spatial dimensions, quantum black holes, and quark contact interactions in measurements of dijet angular distributions in proton-proton collisions at $\sqrt{s} = $ 13 TeV. The data were collected with the CMS detector at the LHC and correspond to an integrated luminosity of 2.6 fb$^{-1}$. The distributions are found to be in agreement with predictions from perturbative quantum chromodynamics that include electroweak corrections. Limits for different contact interaction models are obtained in a benchmark model, valid to next-to-leading order in QCD, in which only left-handed quarks participate, with quark contact interactions excluded up to a scale of 11.5 or 14.7 TeV for destructive or constructive interference, respectively. The production of quantum black holes is excluded for masses below 7.8 or 5.3 TeV, depending on the model. The lower limits for the scales of virtual graviton exchange in the Arkani-Hamed-Dimopoulos-Dvali model of extra spatial dimensions are in the range 7.9-11.2 TeV, and are the most stringent set of limits available.
Links: e-print arXiv:1703.09986 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; HepData record ; CADI line (restricted) ;

Figures & Tables	Summary	References	CMS Publications

Figures
png pdf	Figure 1: Normalized $ {\chi _{\text {dijet}}} $ distributions for 2.6 fb$^{-1}$ of integrated luminosity at $\sqrt {s} = $ 13 TeV . The corrected distributions in data are compared to NLO predictions (black dotted line). The vertical bar on each data point represents statistical and systematic experimental uncertainties combined in quadrature. The horizontal bar indicates the bin width. Theoretical uncertainties are indicated by the gray bands. Also shown are the predictions for QCD+QBH with $n_{\mathrm {ED}}= $ 6 and $M_{\mathrm {QBH}}= $ 7.5 TeV (green dashed-dotted line), QCD+CI with $\Lambda _{\mathrm {LL}}^{+}= $ 11 TeV (red solid line), and QCD+ADD with $\Lambda _{\mathrm {T}} (\mathrm {GRW})= $ 10 TeV (blue dashed line).
png pdf	Figure 2: Normalized $ {\chi _{\text {dijet}}} $ distributions for 2.6 fb$^{-1}$ of integrated luminosity in the highest three mass bins. The corrected distributions in data are compared to NLO predictions with non-perturbative corrections (black dotted line). The vertical bar on each data point represents statistical and systematic experimental uncertainties combined in quadrature. The horizontal bar indicates the bin width. Theoretical uncertainties are indicated by the gray band. Also shown are the predictions for various QBH, CI, and ADD models.
png pdf	Figure 2-a: Normalized $ {\chi _{\text {dijet}}} $ distributions for 2.6 fb$^{-1}$ of integrated luminosity in the $M_{\mathrm{jj}} > $ 4.8 TeV mass bin. The corrected distribution in data is compared to NLO predictions with non-perturbative corrections (black dotted line). The vertical bar on each data point represents statistical and systematic experimental uncertainties combined in quadrature. The horizontal bar indicates the bin width. Theoretical uncertainties are indicated by the gray band. Also shown are the predictions for various QBH, CI, and ADD models.
png pdf	Figure 2-b: Normalized $ {\chi _{\text {dijet}}} $ distributions for 2.6 fb$^{-1}$ of integrated luminosity in the 4.2 $ < M_{\mathrm{jj}} < $ 4.8 TeV mass bin. The corrected distribution in data is compared to NLO predictions with non-perturbative corrections (black dotted line). The vertical bar on each data point represents statistical and systematic experimental uncertainties combined in quadrature. The horizontal bar indicates the bin width. Theoretical uncertainties are indicated by the gray band. Also shown are the predictions for various QBH, CI, and ADD models.
png pdf	Figure 2-c: Normalized $ {\chi _{\text {dijet}}} $ distributions for 2.6 fb$^{-1}$ of integrated luminosity in the 3.6 $ < M_{\mathrm{jj}} < $ 4.2 TeV mass bin. The corrected distribution in data is compared to NLO predictions with non-perturbative corrections (black dotted line). The vertical bar on each data point represents statistical and systematic experimental uncertainties combined in quadrature. The horizontal bar indicates the bin width. Theoretical uncertainties are indicated by the gray band. Also shown are the predictions for various QBH, CI, and ADD models.

Tables
png pdf	Table 1: Summary of main experimental and theoretical uncertainties in the normalized ${\chi _{\text {dijet}}}$ distributions. Although the change in the ${\chi _{\text {dijet}}}$ distribution from each uncertainty is taken into account in the statistical analysis, this table summarizes the uncertainty in just the smallest ${\chi _{\text {dijet}}}$ bin, for the smallest and largest bins in dijet mass. The uncertainty in the dijet bin with largest mass is dominated by the statistical experimental contribution, while the theoretical contribution is dominated by the uncertainty in the NLO QCD scale.
png pdf	Table 2: Observed and expected exclusion limits at 95% CL for various CI, ADD, and QBH models.

Summary

Normalized dijet angular distributions have been measured at $\sqrt{s} = $ 13 TeV with the CMS detector over a wide range of dijet invariant masses. The distributions are found to be in agreement with predictions of perturbative QCD and are used to set lower limits on the contact-interaction scale for a variety of quark-compositeness models that include next-to-leading order QCD corrections, models with large extra dimensions, and models of quantum black-hole production. The 95% confidence level lower limits for the contact interaction scale $\Lambda$ are in the range 8.4-18.6 TeV. Also excluded are quantum black holes with masses up to 7.8 TeV in the ADD model for $n_{\mathrm{ED}} = $ 6, and up to 5.3 TeV in the Randall-Sundrum model for $n_{\mathrm{ED}}= $ 1. The lower limits for the scales of ADD models, $\Lambda_{\mathrm{T}}$ (GRW) and $M_{\mathrm{S}}$ (HLZ), are in the range 7.9-11.2 TeV, and are the most stringent set of limits available.

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