CMS-EXO-17-030

CMS-EXO-17-030 ; CERN-EP-2018-247
Search for pair-produced three-jet resonances in proton-proton collisions at $\sqrt{s}= $ 13 TeV
CMS Collaboration
23 October 2018
Phys. Rev. D 99 (2019) 012010
Abstract: A search has been performed for pair-produced resonances decaying into three jets. The proton-proton collision data used for this analysis were collected with the CMS detector in 2016 at a center-of-mass energy of 13 TeV and correspond to an integrated luminosity of 35.9 fb$^{-1}$. The mass range from 200 to 2000 GeV is explored in four separate mass regions. The observations show agreement with standard model expectations. The results are interpreted within the framework of $R$-parity violating SUSY, where pair-produced gluinos decay to a six quark final state. Gluino masses below 1500 GeV are excluded at 95% confidence level. An analysis based on data with multijet events reconstructed at the trigger level extends the reach to masses as low as 200 GeV. Improved analysis techniques have led to enhanced sensitivity, allowing the most stringent limits to date to be set on gluino pair production.
Links: e-print arXiv:1810.10092 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; CADI line (restricted) ;

Figures & Tables	Summary	References	CMS Publications

Figures
png pdf	Figure 1: Pair masses within the triplet as described in Eq. (1) plotting superimposed $\hat{m}(3,2)^2_{\text {high}}$ vs. $\hat{m}(3,2)^2_{\text {low}}$, $\hat{m}(3,2)^2_{\text {high}}$ vs. $\hat{m}(3,2)^2_{\text {mid}}$ and $\hat{m}(3,2)^2_{\text {mid}}$ vs. $\hat{m}(3,2)^2_{\text {low}}$. QCD multijet triplets (left) cluster at the edge, while triplets from signal events ($m_{\tilde{g}} = $ 800 GeV, right) fill the center.
png pdf	Figure 1-a: Pair masses within the triplet as described in Eq. (1) plotting superimposed $\hat{m}(3,2)^2_{\text {high}}$ vs. $\hat{m}(3,2)^2_{\text {low}}$, $\hat{m}(3,2)^2_{\text {high}}$ vs. $\hat{m}(3,2)^2_{\text {mid}}$ and $\hat{m}(3,2)^2_{\text {mid}}$ vs. $\hat{m}(3,2)^2_{\text {low}}$. QCD multijet triplets cluster at the edge.
png pdf	Figure 1-b: Pair masses within the triplet as described in Eq. (1) plotting superimposed $\hat{m}(3,2)^2_{\text {high}}$ vs. $\hat{m}(3,2)^2_{\text {low}}$, $\hat{m}(3,2)^2_{\text {high}}$ vs. $\hat{m}(3,2)^2_{\text {mid}}$ and $\hat{m}(3,2)^2_{\text {mid}}$ vs. $\hat{m}(3,2)^2_{\text {low}}$. Triplets from signal events ($m_{\tilde{g}} = $ 800 GeV) fill the center.
png pdf	Figure 2: right : The $D^2_{[3,2]}$ variable as described in Eq. (2) for signal (gluino of mass 400 GeV) and QCD multijet triplets. left : The $D^2_{[(6,3)+(3,2)]}$ distribution as described in Eq. (4), for signal (gluino of mass 400 GeV) and QCD multijet triplets. The distributions are made after nominal selection criteria.
png pdf	Figure 2-a: The $D^2_{[(6,3)+(3,2)]}$ distribution as described in Eq. (4), for signal (gluino of mass 400 GeV) and QCD multijet triplets. The distribution is made after nominal selection criteria.
png pdf	Figure 2-b: The $D^2_{[3,2]}$ variable as described in Eq. (2) for signal (gluino of mass 400 GeV) and QCD multijet triplets. The distribution is made after nominal selection criteria.
png pdf	Figure 3: The triplet invariant mass versus the triplet scalar ${p_{\mathrm {T}}}$ for a gluino of mass 400 GeV decaying to jets. The filled color represents correctly reconstructed signal triplets, while the contour lines and gray scatter points represent wrongly combined triplets. The red dashed line illustrates the $\Delta $ cut; triplets to the right of the line pass the selection criterion.
png pdf	Figure 4: Mass distributions and background-only fits for each of the mass regions. Region 1 (top left) is fit to the blackbody-like function described in Eq. (7) as well as ${{\mathrm {t}\overline {\mathrm {t}}}}$ simulation, while the Region 2 and 3 (top right and bottom left) are fit to the four parameter function from Eq. (8), while the Region 4 (bottom right) is fit to three parameter function from Eq. (8) with $p_3$ set to zero. The vertical gray lines indicate the mass regions. The gluino signal normalized to the cross section expected from [35] is shown in purple.
png pdf	Figure 4-a: Mass distribution and background-only fit for mass region 1; fit to the blackbody-like function described in Eq. (7) as well as ${{\mathrm {t}\overline {\mathrm {t}}}}$ simulation. The vertical gray lines indicate the mass regions. The gluino signal normalized to the cross section expected from [35] is shown in purple.
png pdf	Figure 4-b: Mass distribution and background-only fit for mass region 2; fit to the four parameter function from Eq. (8). The vertical gray lines indicate the mass regions. The gluino signal normalized to the cross section expected from [35] is shown in purple.
png pdf	Figure 4-c: Mass distribution and background-only fit for mass region 3; fit to the four parameter function from Eq. (8). The vertical gray lines indicate the mass regions. The gluino signal normalized to the cross section expected from [35] is shown in purple.
png pdf	Figure 4-d: Mass distribution and background-only fit for mass region 4; fit to to three parameter function from Eq. (8) with $p_3$ set to zero. The vertical gray lines indicate the mass regions. The gluino signal normalized to the cross section expected from [35] is shown in purple.
png pdf	Figure 5: Observed and expected frequentist CLs limits on cross section times branching fraction are calculated in the asymptotic approximation. The solid red curve shows the prediction for the gluino pair productions from [35]. The band around the theory curve indicates the uncertainty associated with PDF and scale choices. The gray vertical lines indicate the boundaries between the mass regions.

Tables
png pdf	Table 1: Gluino mass ranges used in this analysis, and selection criteria used. Note that the Gluino mass ranges upper two rows in the table use events collected using the PF Scouting trigger, while the lower two rows in the table use events collected using jets-${H_{\mathrm {T}}}$ trigger. The symbol `$ > $' and `$ < $' represent the direction of the cut.
png pdf	Table 2: Summary of the systematic uncertainties in the signal yield. For the uncertainty affecting the distribution (shape), the value represents the percentage difference in the nominal value of the systematic uncertainty. These systematic uncertainties are applied to the signal.

Summary

A search has been performed for pair-produced resonances decaying into three jets. The proton-proton collision data used for this analysis were collected with the CMS detector in 2016 at a center-of-mass energy of $\sqrt{s}= $ 13 TeV and correspond to an integrated luminosity of 35.9 fb$^{-1}$. The mass range from 200 to 2000 GeV is explored in four separate mass regions. The observations show agreement with standard model expectations. The results are interpreted within the framework of $R$-parity violating SUSY, where pair-produced gluinos decay to a six quark final state. Gluino masses below 1500 GeV are excluded at 95% confidence level. An analysis based on data with multijet events reconstructed at the trigger level extends the reach to masses as low as 200 GeV. Improved analysis techniques have led to enhanced sensitivity, allowing the most stringent limits to date to be set on gluino pair production.

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