CMS-PAS-EXO-16-008

CMS-PAS-EXO-16-008
Search for new physics with high-mass $\tau$ lepton pairs in pp collisions at $\sqrt{s}$ = 13 TeV with the CMS detector
CMS Collaboration
June 2016

Abstract: A search for physics beyond the standard model in events containing $\tau$ lepton pairs of high mass is performed using 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 2.2 fb$^{-1}$. The observation is in good agreement with the standard model prediction. An upper limit at 95% CL on the product of cross section times branching fraction into $\tau$ lepton pairs is calculated as a function of the resonance mass for the Sequential Standard Model. In this model, the presence of $Z'$ bosons decaying into $\tau$ lepton pairs is excluded for $Z'$ masses below 2.1 TeV.
Links: CDS record (PDF) ; inSPIRE record ; CADI line (restricted) ; These preliminary results are superseded in this paper, JHEP 02 (2017) 048. The superseded preliminary plots can be found here.

Figures & Tables	Summary	References	CMS Publications

Figures
png pdf	Figure 1-a: $m(\tau _{1},\tau _{2}$, ${E_{\mathrm {T}}} )$ distribution for all four final states: (a) ${\tau _\mu \tau _{\textrm {h}}} $, (b) ${\tau _e\tau _{\textrm {h}}} $, (c) ${\tau _e\tau _\mu } $, and (d) ${\tau _{\textrm {h}}\tau _{\textrm {h}}} $. The dashed line represents the mass distribution for a $Z'_{SSM} \rightarrow \tau \tau $ with mass of 1500 GeV , in which the event yield is scaled by a factor 10. The rightmost bin includes events with a reconstructed mass greater than 900 GeV.
png pdf	Figure 1-b: $m(\tau _{1},\tau _{2}$, ${E_{\mathrm {T}}} )$ distribution for all four final states: (a) ${\tau _\mu \tau _{\textrm {h}}} $, (b) ${\tau _e\tau _{\textrm {h}}} $, (c) ${\tau _e\tau _\mu } $, and (d) ${\tau _{\textrm {h}}\tau _{\textrm {h}}} $. The dashed line represents the mass distribution for a $Z'_{SSM} \rightarrow \tau \tau $ with mass of 1500 GeV , in which the event yield is scaled by a factor 10. The rightmost bin includes events with a reconstructed mass greater than 900 GeV.
png pdf	Figure 1-c: $m(\tau _{1},\tau _{2}$, ${E_{\mathrm {T}}} )$ distribution for all four final states: (a) ${\tau _\mu \tau _{\textrm {h}}} $, (b) ${\tau _e\tau _{\textrm {h}}} $, (c) ${\tau _e\tau _\mu } $, and (d) ${\tau _{\textrm {h}}\tau _{\textrm {h}}} $. The dashed line represents the mass distribution for a $Z'_{SSM} \rightarrow \tau \tau $ with mass of 1500 GeV , in which the event yield is scaled by a factor 10. The rightmost bin includes events with a reconstructed mass greater than 900 GeV.
png pdf	Figure 1-d: $m(\tau _{1},\tau _{2}$, ${E_{\mathrm {T}}} )$ distribution for all four final states: (a) ${\tau _\mu \tau _{\textrm {h}}} $, (b) ${\tau _e\tau _{\textrm {h}}} $, (c) ${\tau _e\tau _\mu } $, and (d) ${\tau _{\textrm {h}}\tau _{\textrm {h}}} $. The dashed line represents the mass distribution for a $Z'_{SSM} \rightarrow \tau \tau $ with mass of 1500 GeV , in which the event yield is scaled by a factor 10. The rightmost bin includes events with a reconstructed mass greater than 900 GeV.
png pdf	Figure 2-a: 95% CL upper limits on the product of the cross section times branching fraction into $\tau $ lepton pairs as a function of $Z'_{SSM}$ mass for (a) ${\tau _\mu \tau _{\textrm {h}}} $, (b) ${\tau _e\tau _{\textrm {h}}} $, (c) ${\tau _e\tau _\mu } $, (d) ${\tau _{\textrm {h}}\tau _{\textrm {h}}}$ final states, and (e) their combined 95% CL upper limits.
png pdf	Figure 2-b: 95% CL upper limits on the product of the cross section times branching fraction into $\tau $ lepton pairs as a function of $Z'_{SSM}$ mass for (a) ${\tau _\mu \tau _{\textrm {h}}} $, (b) ${\tau _e\tau _{\textrm {h}}} $, (c) ${\tau _e\tau _\mu } $, (d) ${\tau _{\textrm {h}}\tau _{\textrm {h}}}$ final states, and (e) their combined 95% CL upper limits.
png pdf	Figure 2-c: 95% CL upper limits on the product of the cross section times branching fraction into $\tau $ lepton pairs as a function of $Z'_{SSM}$ mass for (a) ${\tau _\mu \tau _{\textrm {h}}} $, (b) ${\tau _e\tau _{\textrm {h}}} $, (c) ${\tau _e\tau _\mu } $, (d) ${\tau _{\textrm {h}}\tau _{\textrm {h}}}$ final states, and (e) their combined 95% CL upper limits.
png pdf	Figure 2-d: 95% CL upper limits on the product of the cross section times branching fraction into $\tau $ lepton pairs as a function of $Z'_{SSM}$ mass for (a) ${\tau _\mu \tau _{\textrm {h}}} $, (b) ${\tau _e\tau _{\textrm {h}}} $, (c) ${\tau _e\tau _\mu } $, (d) ${\tau _{\textrm {h}}\tau _{\textrm {h}}}$ final states, and (e) their combined 95% CL upper limits.
png pdf	Figure 2-e: 95% CL upper limits on the product of the cross section times branching fraction into $\tau $ lepton pairs as a function of $Z'_{SSM}$ mass for (a) ${\tau _\mu \tau _{\textrm {h}}} $, (b) ${\tau _e\tau _{\textrm {h}}} $, (c) ${\tau _e\tau _\mu } $, (d) ${\tau _{\textrm {h}}\tau _{\textrm {h}}}$ final states, and (e) their combined 95% CL upper limits.

Tables

png pdf

Table 1:
Number of events observed in data compared to expected background yields and hypothetical $Z^{'}_{SSM}$ signals of mass 1.0, 1.5, and 2.0 TeV . The expected signal yields are computed at NLO accuracy, using a k-factor of 1.3. The top table gives inclusive yields; the bottom table gives yields requiring $m(\tau _{1},\tau _{2}, {E_{\mathrm {T}}} ) > $ 300 GeV. The uncertainties quoted on the background yields represent the combined statistical and systematic uncertainties.

Summary

A search for new physics beyond the standard model in events containing $\tau$ lepton pairs of high mass has been performed, using data corresponding to an integrated luminosity of 2.2 fb$^{-1}$ collected by the CMS detector in pp collisions at $\sqrt{s} = 13 TeV$. The observed mass spectra in the ${\tau_\mu\tau_{\textrm{h}}} $, ${\tau_e\tau_{\textrm{h}}} $, $\tau_h \tau_h$, and ${\tau_e\tau_\mu}$ channels are consistent with the SM expectations and an upper limit at 95% CL on the product of cross section times branching fraction into $\tau$ lepton pairs has been determined as a function of the $Z'$ mass. The presence of $Z'$ bosons decaying to $\tau$ leptons is excluded by the data for $Z'$ masses below 2.1 TeV in the SSM.

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