Search for resonances and quantum black holes using dijet mass spectra in proton-proton collisions at $\sqrt{s}$ = 8 CMS.TeV

Abstract

A search for resonances and quantum black holes is performed using the dijet mass spectra measured in proton-proton collisions at $\sqrt{s}=8$ CMS.TeV with the CMS detector at the LHC. The data set corresponds to an integrated luminosity of 19.7$fb^{-1}$. In a search for narrow resonances that couple to quark-quark, quark-gluon, or gluon-gluon pairs, model-independent upper limits, at 95% confidence level, are obtained on the production cross section of resonances, with masses above 1.2 CMS.TeV. When interpreted in the context of specific models the limits exclude: string resonances with masses below 5.0 CMS.TeV; excited quarks below 3.5 CMS.TeV; scalar diquarks below 4.7 CMS.TeV; W bosons below 1.9 CMS.TeV or between 2.0 and 2.2 CMS.TeV; Z bosons below 1.7 CMS.TeV; and Randall-Sundrum gravitons below 1.6 CMS.TeV. A separate search is conducted for narrow resonances that decay to final states including b quarks. The first exclusion limit is set for excited b quarks, with a lower mass limit between 1.2 and 1.6 CMS.TeV depending on their decay properties. Searches are also carried out for wide resonances, assuming for the first time width-to-mass ratios up to 30%, and for quantum black holes with a range of model parameters. The wide resonance search excludes axigluons and colorons with mass below 3.6 CMS.TeV, and color-octet scalars with mass below 2.5 CMS.TeV. Lower bounds between 5.0 and 6.3 CMS.TeV are set on the masses of quantum black holes.

Results on HepData

Figures included in the PAPER EXO-12-059 (click on the plot to get the corresponding .pdf file)

Figure Caption
tagging_rate_bb.png Tagging efficiencies for 0b, 1b, and 2b selections as a function of the resonance mass for bb decay modes, for an RS graviton G decaying to a bb pair. The hatched regions represent the uncertainties in the tagging efficiencies corresponding to the variation of the b-tagging scale factors within their uncertainties.
tagging_rate_bg.png Tagging efficiencies for 0b, 1b, and 2b selections as a function of the resonance mass for bg decay modes, for an excited quark b* decaying to a b-quark and a gluon. The hatched regions represent the uncertainties in the tagging efficiencies corresponding to the variation of the b-tagging scale factors within their uncertainties.
tagging_rate_qq.png Tagging efficiencies for 0b, 1b, and 2b selections as a function of the resonance mass for qq/gg (where q=u, d, s) decay modes, for an RS graviton G decaying to two gluons or to a qq pair, with q=u, d, or s. The hatched regions represent the uncertainties in the tagging efficiencies corresponding to the variation of the b-tagging scale factors within their uncertainties.
defaultfit_pull_withsignal_new.png Inclusive dijet mass spectrum from wide jets (points) compared to a fit (solid curve) and to predictions including detector simulation of multijet events and signal resonances. The predicted multijet shape (QCD MC) has been scaled to the data (see text). The vertical error bars are statistical only and the horizontal error bars are the bin widths. For comparison, the signal distributions for a W resonance of mass 1.9 CMS.TeV and an excited quark of mass 3.6 CMS.TeV are shown. The bin-by-bin fit residuals scaled to the statistical uncertainty of the data, $(data-fit)/\sigma_{data}$, are shown at the bottom and compared with the expected signal contributions. The bin widths, the data points, and the statistical uncertainties on the data points are reported in this text file
DijetFit_0tag.png Dijet mass spectrum (points) in the 0 b-tag multiplicity bin compared to a fit (solid curve). The vertical error bars are statistical only and the horizontal error bars are the bin widths. For comparison, signal distributions are shown for an excited b quark of mass 1800 CMS.GeV, a Z` of mass 2200 CMS.GeV, an RS graviton of mass 2800 CMS.GeV, and a Z` of mass 3200 CMS.GeV. The bin-by-bin fit residuals scaled to the statistical uncertainty of the data, $(data-fit)/\sigma_{data}$, are shown at the bottom of each plot.
DijetFit_1tag.png Dijet mass spectrum (points) in the 1 b-tag multiplicity bin compared to a fit (solid curve). The vertical error bars are statistical only and the horizontal error bars are the bin widths. For comparison, signal distributions are shown for an excited b quark of mass 1800 CMS.GeV, a Z` of mass 2200 CMS.GeV, an RS graviton of mass 2800 CMS.GeV, and a Z` of mass 3200 CMS.GeV. The bin-by-bin fit residuals scaled to the statistical uncertainty of the data, $(data-fit)/\sigma_{data}$, are shown at the bottom of each plot.
DijetFit_2tag.png Dijet mass spectrum (points) in the 2 b-tag multiplicity bin compared to a fit (solid curve). The vertical error bars are statistical only and the horizontal error bars are the bin widths. For comparison, signal distributions are shown for an excited b quark of mass 1800 CMS.GeV, a Z` of mass 2200 CMS.GeV, an RS graviton of mass 2800 CMS.GeV, and a Z` of mass 3200 CMS.GeV. The bin-by-bin fit residuals scaled to the statistical uncertainty of the data, $(data-fit)/\sigma_{data}$, are shown at the bottom of each plot.
comparison_obsval_new.png The observed 95% CL upper limits on $\sigma B A$ for narrow dijet resonances. Limits on gluon-gluon, quark-gluon, and quark-quark narrow resonances from the inclusive analysis, compared to LO theoretical predictions for several resonance models.
limit_rsg_2.png The observed 95% CL upper limits on $\sigma B A$ for narrow dijet resonances. Combined limits on gg/bb resonances for different values of $f_{bb}$. The theoretical cross section for an RS graviton is shown for comparison.
limit_zprime_2.png The observed 95% CL upper limits on $\sigma B A$ for narrow dijet resonances. Combined limits on qq/bb resonances for different values of $f_{bb}$. The theoretical cross section for a Z` is shown for comparison.
qq_limit_new.png The observed 95% CL upper limits on $\sigma B A$ for narrow resonances decaying into qq final states. The limits are shown as points and solid lines. Also shown are the expected limits (dot-dashed dark lines) and their variation at the $1\sigma$ and $2\sigma$ levels (shaded bands). Predicted cross sections calculated at LO for various narrow resonances are also shown.
qg_limit_new.png The observed 95% CL upper limits on $\sigma B A$ for narrow resonances decaying into qg final states. The limits are shown as points and solid lines. Also shown are the expected limits (dot-dashed dark lines) and their variation at the $1\sigma$ and $2\sigma$ levels (shaded bands). Predicted cross sections calculated at LO for various narrow resonances are also shown.
gg_limit_new.png The observed 95% CL upper limits on $\sigma B A$ for narrow resonances decaying into gg final states. The limits are shown as points and solid lines. Also shown are the expected limits (dot-dashed dark lines) and their variation at the $1\sigma$ and $2\sigma$ levels (shaded bands). Predicted cross sections calculated at LO for various narrow resonances are also shown.
RS_graviton_limit_new.png The observed 95% CL upper limits on $\sigma B A$ for RS graviton resonances. The limits are shown as points and solid lines. Also shown are the expected limits (dot-dashed dark lines) and their variation at the $1\sigma$ and $2\sigma$ levels (shaded bands). Predicted cross sections calculated at LO for various narrow resonances are also shown.
limit_bstar.png Observed and expected 95% CL upper limits on $\sigma B A$ with systematic uncertainties included, for b* $\rightarrow$ bg resonances, compared with the LO theoretical cross section for excited b-quark production.
qq_resonanceshape_diffwidth_comparison.png Dijet mass distributions for qq resonances with masses of 1, 2, 3, 4, and 5 CMS.TeV and two different values of $\Gamma/M$ (10% and 1.5%). The corrections for the difference in the JES between a parametric simulation and the GEANT4-based CMS simulation have been applied.
gg_resonanceshape_diffwidth_comparison.png Dijet mass distributions for gg resonances with masses of 1, 2, 3, 4, and 5 CMS.TeV and two different values of $\Gamma/M$ (10% and 1.5%). The corrections for the difference in the JES between a parametric simulation and the GEANT4-based CMS simulation have been applied.
fastsim_qqlimit_observed_final.png Observed 95% CL upper limits on $\sigma B A$ as a function of the resonance mass for different values of the width-to-mass ratio $\Gamma/M$, computed for $qq \rightarrow G \rightarrow qq$.
fastsim_gglimit_observed_final.png Observed 95% CL upper limits on $\sigma B A$ as a function of the resonance mass for different values of the width-to-mass ratio $\Gamma/M$, computed for $gg \rightarrow G \rightarrow gg$.
qq_axigluon_newlimit.png Observed 95% CL upper limits on $\sigma B A$ with systematic uncertainties included for axigluon/coloron wide resonances, compared to the corresponding theoretical predictions. The axigluon/coloron resonances have a relative width $\Gamma/M$ between 5% and 10%. More details on the cross section calculations for wide resonances are reported in the Appendix.
gg_S8_newlimit.png Observed 95% CL upper limits on $\sigma B A$ with systematic uncertainties included for S8 wide resonances, compared to the corresponding theoretical predictions. The S8 resonances have a relative width $\Gamma/M$ between 5% and 10%. More details on the cross section calculations for wide resonances are reported in the Appendix.
BH_resonance_mass.png Dijet mass distribution for QBHs with $M_{QBH}^{min}$ from 2 to 6.5 CMS.TeV. The signal shape is almost independent both of the number of extra dimensions $n$ and the scale $M_{D}$.
BH_limitMD2TeV.png Observed 95% CL upper limits on $\sigma B A$ as a function of $M_{QBH}^{min}$, compared to theoretical predictions with fundamental Planck scale, $M_{D}$, of 2 CMS.TeV, and number of extra dimensions $n$ ranging from 1 to 6.
BH_limitMD3TeV.png Observed 95% CL upper limits on $\sigma B A$ as a function of $M_{QBH}^{min}$, compared to theoretical predictions with fundamental Planck scale, $M_{D}$, of 3 CMS.TeV, and number of extra dimensions $n$ ranging from 1 to 6.
BH_limitMD4TeV.png Observed 95% CL upper limits on $\sigma B A$ as a function of $M_{QBH}^{min}$, compared to theoretical predictions with fundamental Planck scale, $M_{D}$, of 4 CMS.TeV, and number of extra dimensions $n$ ranging from 1 to 6.
BH_limitMD5TeV.png Observed 95% CL upper limits on $\sigma B A$ as a function of $M_{QBH}^{min}$, compared to theoretical predictions with fundamental Planck scale, $M_{D}$, of 5 CMS.TeV, and number of extra dimensions $n$ ranging from 1 to 6.
excluded_BHmass.png Observed 95% CL lower limits on $M_{QBH}^{min}$ as a function of the Planck scale $M_{D}$ and the number of extra dimensions $n$.

Table Caption
tab1.png Observed 95% CL upper limits on $\sigma B A$ for narrow qq, qg, and gg resonances, from the inclusive analysis for signal masses between 1.2 and 5.5 CMS.TeV.
tab2.png Observed 95% CL upper limits on $\sigma B A$ for narrow gg/bb, qq/bb, and bg resonances from the b-enriched analysis, for signal masses between 1.2 and 4.0 CMS.TeV. The upper limits are given for different ratios $f_{bb}$ for gg/bb and qq/bb resonances, and for 100% branching fraction into bg.
tab3.png Observed and expected 95% CL exclusions on the mass of various resonances. Systematic uncertainties are taken into account. For excited b quark the expected mass limit is below the range of this analysis. For the axigluon/coloron and color-octet scalar only observed mass limits are computed.
tab4.png Observed 95% CL upper limits on $\sigma B A$ as a function of resonance mass for several values of the width-to-mass ratio $\Gamma/M$, computed for $qq \rightarrow G \rightarrow qq$ and $gg \rightarrow G \rightarrow gg$. The missing entries correspond to the region where the two conditions for the validity of the wide resonance analysis are not satisfied (see text).
tab5.png Observed 95% CL upper limits on $\sigma B A$ for QBHs from the inclusive analysis. These limits are valid for the number of extra dimensions $n$ considered in this paper, ranging from 1 to 6. Cross section limits are presented only for $M_{QBH}^{min} >= M_{D}$ for different values of $M_{D}$, as described in the text.
tab6.png Observed 95% CL lower limits on $M_{QBH}^{min}$ for different numbers of extra dimensions $n$ and several values of $M_{D}$.
tab7.png Correction factors defined as the ratio of the full cross section obtained from Eqs. (5)-(7) to the cross section from the narrow-width approximation calculations, as a function of the resonance mass, for qq and gg resonances and for eight different resonance widths in proton-proton collisions at $\sqrt{s}=8$ CMS.TeV.

Public Supplemental Material (click on the plot to get the corresponding .png file)

Figure Caption
204541_32_52508234_3d.png Display for the event with the highest di-wide-jet mass (5.2 CMS.TeV) in the data (3D view).
204541_32_52508234_rho_phi.png Display for the event with the highest di-wide-jet mass (5.2 CMS.TeV) in the data ($\rho/\phi$ view).



Responsible: FrancescoSantanastasio

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Topic revision: r7 - 2015-09-07 - FrancescoSantanastasio
 
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