CMS-PAS-SMP-15-001

CMS-PAS-SMP-15-001
Combination of results from the ATLAS and CMS experiments on anomalous triple gauge couplings from ${ZZ}$ production in ${pp}$ collisions at a center-of-mass energy of 7 TeV at the LHC
CMS Collaboration
July 2016

Abstract: A procedure is presented to combine data from the ATLAS and CMS experiments on $ZZ$ production to obtain constraints on anomalous neutral triple gauge boson couplings. Statistical and systematic uncertainties and their correlations are taken into account. Data from $pp$ collisions at a center-of-mass energy of 7 TeV delivered by the LHC are used. The datasets correspond to integrated luminosities of 4.6 and 5.0 fb$^{-1}$ for ATLAS and CMS, respectively. The combination is performed in the fully leptonic decay channels $ZZ \to \ell^+ \ell^- \nu \bar{\nu}$ (ATLAS) and $ZZ \to \ell^+ \ell^- \ell'^+ \ell'^-$ (ATLAS, CMS). Combined limits on the coupling parameters are $ -0.010 < f_4^\gamma < 0.011 $, $ -0.0087 < f_4^Z < 0.0091 $, $ -0.011 < f_5^\gamma < 0.010 $, and $ -0.0091 < f_5^Z < 0.0089 $ at 95% C.L., where all other parameters are fixed to the standard model values. These results represent the first combined limits of the ATLAS and CMS collaborations for anomalous gauge boson couplings.
Links: CDS record (PDF) ; inSPIRE record ; CADI line (restricted) ;

Figures & Tables	Summary	References	CMS Publications

Figures
png pdf	Figure 1: One-parameter observed deltaNLL limits on aTGCs for $\Lambda = \infty $. All anomalous coupling parameters other than the measured one are set to their SM values.
png pdf	Figure 2-a: Two-parameter expected and observed deltaNLL combined limits on aTGCs for $\Lambda = \infty $. All anomalous coupling parameters other than the measured one are set to their SM values.
png pdf	Figure 2-b: Two-parameter expected and observed deltaNLL combined limits on aTGCs for $\Lambda = \infty $. All anomalous coupling parameters other than the measured one are set to their SM values.

Tables
png pdf	Table 1: Observed and predicted event yields in bins of leading $Z$ ${p_{\mathrm {T}}}$ in the $ZZ \to \ell ^+ \ell ^- \ell '^+ \ell '^-$ channel for ATLAS. The first uncertainty is statistical while the second is systematic.
png pdf	Table 2: Observed and predicted event yields in the $ZZ \to \ell ^+ \ell ^- \bar{\nu } \nu $ channel for ATLAS. The first uncertainty is statistical while the second is systematic.
png pdf	Table 3: Summary of systematic uncertainties, as relative percentages of the correction factor $C_{ { {Z} {Z}} }$ or the acceptance $A_{ { {Z} {Z}} }$ of the fiducial region for ATLAS.
png pdf	Table 4: Observed and predicted number of $ {Z} {Z}$ events for CMS.
png pdf	Table 5: Relative systematic uncertainties in the $ZZ$ measurement for CMS.
png pdf	Table 6: List of fully correlated uncertainties between experiments.
png pdf	Table 7: List of uncorrelated uncertainties between experiments.
png pdf	Table 8: Expected 95% confidence intervals from one-parameter fits for ATLAS, CMS and combined ATLAS and CMS experimental data inputs and for $\Lambda = \infty $. All anomalous coupling parameters other than the measured one are set to their SM values.
png pdf	Table 9: Observed 95% confidence intervals from one-parameter fits for ATLAS, CMS and combined ATLAS and CMS experimental data inputs and for $\Lambda = \infty $. All anomalous coupling parameters other than the measured one are set to their SM values.

Summary

The combination of anomalous TGC limits from ATLAS and CMS using the $ZZ$ production channel in $pp$ collisions at a center-of-mass energy of 7 TeV at the LHC is presented. The datasets correspond to integrated luminosities of $4.6$ and 5.0 fb$^{-1}$ for ATLAS and CMS, respectively. Combined 95% C.L. limits from one-parameter fits on aTGC parameters are: $ -0.010 < f_4^\gamma < 0.011$, $ -0.0087 < f_4^Z < 0.0091$, $ -0.011 < f_5^\gamma < 0.010$, $-0.0091 < f_5^Z < 0.0089 $. The combination improves the sensitivity to aTGC parameters by about 20% relative to the sensitivity of a single experiment. Negligible is the effect of the systematic uncertainties on the limits on aTGC parameters. These results represent the first combined limits of the ATLAS and CMS collaborations for anomalous gauge boson couplings. Nevertheless, they are not competitive with respect to recent results using 8 TeV data from the LHC [21] because of the larger data-set with four times the integrated luminosity compared to 7 TeV data-set. This analysis outlines a combination procedure that can serve as guidance for future combinations of aTGC parameters at the LHC.

References
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