CMS-PAS-EXO-17-002

CMS-PAS-EXO-17-002
Search for excited states of light and heavy flavor quarks in the $\gamma$+jets final state in proton-proton collisions at $\sqrt{s}= $ 13 TeV
CMS Collaboration
July 2017

Abstract: A search for excited states of light and heavy flavor quarks decaying into the $\gamma$+jets final state is presented. The analysis is based on data corresponding to an integrated luminosity of 35.9 fb$^{-1}$ collected by the CMS experiment in proton-proton collisions at $\sqrt{s}= $ 13 TeV in 2016 at the LHC. Events containing at least one photon and one jet with high transverse momenta are selected and the $\gamma$+jets invariant mass distribution is searched for a resonance peak. The upper limits on the cross section times branching fraction are evaluated as a function of the excited quark masses. At 95% confidence level, the most stringent limits are presented in $\gamma$+jets final state to exclude the excited light quarks with masses below 5.5 TeV and the excited b quarks with masses below 1.8 TeV for coupling multiplier $f = 1.0$.
Links: CDS record (PDF) ; CADI line (restricted) ; These preliminary results are superseded in this paper, PLB 781 (2018) 390. The superseded preliminary plots can be found here.

Figures & Tables	Summary	References	CMS Publications

Figures
png pdf	Figure 1: Acceptance times efficiency for ${ {\mathrm {q}^\star } }$ and ${ {\mathrm {b}^\star } }$ signal for coupling $f = 1.0$ as a function of generated M$_{{ {\mathrm {q}^\star } }}$ or M$_{{ {\mathrm {b}^\star } }}$ mass using MC simulation.
png pdf	Figure 2: The $\gamma$+jets invariant mass distribution in data (black points) for the inclusive category used for the ${ {\mathrm {q}^\star } }$ analysis, after final selection. The result of the fit to the data using the parametrization defined in Eq. 2 is shown with the blue dashed curve. The bin-by-bin pull, (Data-Fit)/stat. unc., where stat. unc. refers to the statistical uncertainty in data, is also presented. Simulations of excited quark signals are shown for mass points 1.0 and 5.0 TeV for $f = 1.0$ and for mass point 2.0 TeV for $f = 0.5$.
png pdf	Figure 3: The $\gamma$+b-jets invariant mass distribution in data (black points) used for the ${ {\mathrm {b}^\star } }$ analysis, after final selection for (a) 1 b tag category and (b) 0 b tag category. The result of the fit to the data using the parametrization defined in Eq. 2 is shown with the blue dashed curve. The bin-by-bin pull, (Data-Fit)/stat. unc., where stat. unc. refers to the statistical uncertainty in data, is also presented. Simulations of excited b quark signals are shown under 1 and 0 b tag category for masses 1.0 and 2.0 TeV for $f = 1.0$.
png pdf	Figure 3-a: The $\gamma$+b-jets invariant mass distribution in data (black points) used for the ${ {\mathrm {b}^\star } }$ analysis, after final selection for 1 b tag category. The result of the fit to the data using the parametrization defined in Eq. 2 is shown with the blue dashed curve. The bin-by-bin pull, (Data-Fit)/stat. unc., where stat. unc. refers to the statistical uncertainty in data, is also presented. Simulations of excited b quark signals are shown under 1 and 0 b tag category for masses 1.0 and 2.0 TeV for $f = 1.0$.
png pdf	Figure 3-b: The $\gamma$+b-jets invariant mass distribution in data (black points) used for the ${ {\mathrm {b}^\star } }$ analysis, after final selection for 0 b tag category. The result of the fit to the data using the parametrization defined in Eq. 2 is shown with the blue dashed curve. The bin-by-bin pull, (Data-Fit)/stat. unc., where stat. unc. refers to the statistical uncertainty in data, is also presented. Simulations of excited b quark signals are shown under 1 and 0 b tag category for masses 1.0 and 2.0 TeV for $f = 1.0$.
png pdf	Figure 4: The expected and observed 95% CL upper limits on $\sigma \times \text {B}$ for excited quark search in $\gamma$+jets final state corresponding to coupling $f = 1.0$. The limits are compared with the theoretical predictions for excited quark production. The uncertainties at 1 and 2 standard deviations (s.d.) levels are shown as green and yellow shaded bands around expected limit.
png pdf	Figure 5: The expected and observed 95% CL upper limits on $\sigma \times \text {B}$ for excited b quark search in $\gamma$+b-jets final state corresponding to coupling $f = 1.0$. The limits are compared with the theoretical predictions for excited b quark production. The uncertainties at 1 and 2 standard deviations (s.d.) levels are shown as green and yellow shaded bands around expected limit.
png pdf	Figure 6: The observed and expected excluded regions for ${ {\mathrm {q}^\star } }$ and ${ {\mathrm {b}^\star } }$ at 95% CL as a function of M$_{{ {\mathrm {q}^\star } }}$, M$_{{ {\mathrm {b}^\star } }}$ and the coupling strength $f$.

Tables
png pdf	Table 1: Summary of the dominant sources of uncertainties and their effect on yield.

Summary

We have presented a search for excited states of light and heavy flavor quarks in the $\gamma$+jets and $\gamma$+b-jets final states, respectively. The search is performed with data collected at $\sqrt{s} =$ 13 TeV in 2016, which corresponds to an integrated luminosity of 35.9 fb$^{-1}$.

The 95% CL upper limits are placed on $\sigma\times\text{B}$ for $ {\mathrm{q}^\star} $ and $ {\mathrm{b}^\star} $ production in $\gamma$+jets and $\gamma$+b-jets final states, respectively. Comparing these cross section upper limits with theoretical predictions, an excited quark within mass range 1.0 $ < \text{M}_{ {\mathrm{q}^\star} } < $ 5.5 TeV and an excited b quark within mass range 1.0 $ < \text{M}_{ {\mathrm{b}^\star} } < $ 1.8 TeV are excluded at 95% CL for coupling multipliers $f = 1.0$. We present the first result on the search of excited b quark at $\sqrt{s} = $ 13 TeV at the LHC. These are best results to date for $ {\mathrm{q}^\star} $ and $ {\mathrm{b}^\star} $ searches in $\gamma$+jets final state at the LHC.

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