CMS-EXO-22-013

CMS-EXO-22-013 ; CERN-EP-2024-275
Search for $t$ -channel scalar and vector leptoquark exchange in the high-mass dimuon and dielectron spectra in proton-proton collisions at $\sqrt{s} =$ 13 TeV
CMS Collaboration
25 March 2025
Submitted to J. High Energy Phys.
Abstract: A search for $t$ -channel exchange of leptoquarks (LQs) is performed in dimuon and dielectron spectra using proton-proton collision data collected at $\sqrt{s}=$ 13 TeV with the CMS detector at the CERN LHC. The data correspond to an integrated luminosity of 138 fb $^{-1}$ . Eight scenarios are considered, in which scalar or vector LQs couple up or down quarks to muons or electrons, for dilepton invariant masses above 500 GeV. The LQ masses are probed up to 5 TeV, beyond a regime probed by previous pair-production and single-production searches. The differential distributions of dilepton events are fit to templates that model the nonresonant LQ exchange and various standard model background processes. Limits are set on LQ-fermion coupling strengths for scalar and vector LQ masses in the 1-5 TeV range at 95% confidence level, establishing stringent limits on first- and second-generation LQs.
Links: e-print arXiv:2503.20023 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; HepData record ; CADI line (restricted) ;

Figures & Tables	Summary	References	CMS Publications

Figures
png pdf	Figure 1: Leading order Feynman diagrams for SM DY production (left) and $t$ -channel LQ exchange (right). The LQ amplitude interferes with the $\mathrm{Z}/\gamma^{*}$ amplitude.
png pdf	Figure 2: A comparison of data and expected background distributions in the dilepton invariant mass (upper row), $c_\mathrm{R}$ (middle row), and dilepton rapidity (lower row). The left (right) plots show the $\mu\mu$ ( $\mathrm{e}\mathrm{e}$ ) channel. The blue histogram represents the signal yield of a hypothetical 2.5 TeV $\mathrm{S_{\mu u}}$ ( $\mathrm{S_{e u}}$ ) with $y_{\mathrm{\mu u}}\,(y_{\mathrm{e u}})=$ 2.0, while the yellow histogram represents the signal yield of a hypothetical 2.5 TeV $\mathrm{V_{\mu u}}\, (\mathrm{V_{e u}})$ with $g_{\mathrm{\mu u}}\,(g_{\mathrm{e u}})=$ 1.0. The black points with error bars represent the data and their statistical uncertainties. The background expectation is shown as stacked histograms. The hatched band shows the total systematic uncertainty in the expected background yield. The lower panels show the ratios of the data to the expectation. The gray bands represent the normalized uncertainty in the predicted yield. The error bars in the ratio plot represent the normalized statistical uncertainty in the data.
png pdf	Figure 2-a: A comparison of data and expected background distributions in the dilepton invariant mass (upper row), $c_\mathrm{R}$ (middle row), and dilepton rapidity (lower row). The left (right) plots show the $\mu\mu$ ( $\mathrm{e}\mathrm{e}$ ) channel. The blue histogram represents the signal yield of a hypothetical 2.5 TeV $\mathrm{S_{\mu u}}$ ( $\mathrm{S_{e u}}$ ) with $y_{\mathrm{\mu u}}\,(y_{\mathrm{e u}})=$ 2.0, while the yellow histogram represents the signal yield of a hypothetical 2.5 TeV $\mathrm{V_{\mu u}}\, (\mathrm{V_{e u}})$ with $g_{\mathrm{\mu u}}\,(g_{\mathrm{e u}})=$ 1.0. The black points with error bars represent the data and their statistical uncertainties. The background expectation is shown as stacked histograms. The hatched band shows the total systematic uncertainty in the expected background yield. The lower panels show the ratios of the data to the expectation. The gray bands represent the normalized uncertainty in the predicted yield. The error bars in the ratio plot represent the normalized statistical uncertainty in the data.
png pdf	Figure 2-b: A comparison of data and expected background distributions in the dilepton invariant mass (upper row), $c_\mathrm{R}$ (middle row), and dilepton rapidity (lower row). The left (right) plots show the $\mu\mu$ ( $\mathrm{e}\mathrm{e}$ ) channel. The blue histogram represents the signal yield of a hypothetical 2.5 TeV $\mathrm{S_{\mu u}}$ ( $\mathrm{S_{e u}}$ ) with $y_{\mathrm{\mu u}}\,(y_{\mathrm{e u}})=$ 2.0, while the yellow histogram represents the signal yield of a hypothetical 2.5 TeV $\mathrm{V_{\mu u}}\, (\mathrm{V_{e u}})$ with $g_{\mathrm{\mu u}}\,(g_{\mathrm{e u}})=$ 1.0. The black points with error bars represent the data and their statistical uncertainties. The background expectation is shown as stacked histograms. The hatched band shows the total systematic uncertainty in the expected background yield. The lower panels show the ratios of the data to the expectation. The gray bands represent the normalized uncertainty in the predicted yield. The error bars in the ratio plot represent the normalized statistical uncertainty in the data.
png pdf	Figure 2-c: A comparison of data and expected background distributions in the dilepton invariant mass (upper row), $c_\mathrm{R}$ (middle row), and dilepton rapidity (lower row). The left (right) plots show the $\mu\mu$ ( $\mathrm{e}\mathrm{e}$ ) channel. The blue histogram represents the signal yield of a hypothetical 2.5 TeV $\mathrm{S_{\mu u}}$ ( $\mathrm{S_{e u}}$ ) with $y_{\mathrm{\mu u}}\,(y_{\mathrm{e u}})=$ 2.0, while the yellow histogram represents the signal yield of a hypothetical 2.5 TeV $\mathrm{V_{\mu u}}\, (\mathrm{V_{e u}})$ with $g_{\mathrm{\mu u}}\,(g_{\mathrm{e u}})=$ 1.0. The black points with error bars represent the data and their statistical uncertainties. The background expectation is shown as stacked histograms. The hatched band shows the total systematic uncertainty in the expected background yield. The lower panels show the ratios of the data to the expectation. The gray bands represent the normalized uncertainty in the predicted yield. The error bars in the ratio plot represent the normalized statistical uncertainty in the data.
png pdf	Figure 2-d: A comparison of data and expected background distributions in the dilepton invariant mass (upper row), $c_\mathrm{R}$ (middle row), and dilepton rapidity (lower row). The left (right) plots show the $\mu\mu$ ( $\mathrm{e}\mathrm{e}$ ) channel. The blue histogram represents the signal yield of a hypothetical 2.5 TeV $\mathrm{S_{\mu u}}$ ( $\mathrm{S_{e u}}$ ) with $y_{\mathrm{\mu u}}\,(y_{\mathrm{e u}})=$ 2.0, while the yellow histogram represents the signal yield of a hypothetical 2.5 TeV $\mathrm{V_{\mu u}}\, (\mathrm{V_{e u}})$ with $g_{\mathrm{\mu u}}\,(g_{\mathrm{e u}})=$ 1.0. The black points with error bars represent the data and their statistical uncertainties. The background expectation is shown as stacked histograms. The hatched band shows the total systematic uncertainty in the expected background yield. The lower panels show the ratios of the data to the expectation. The gray bands represent the normalized uncertainty in the predicted yield. The error bars in the ratio plot represent the normalized statistical uncertainty in the data.
png pdf	Figure 2-e: A comparison of data and expected background distributions in the dilepton invariant mass (upper row), $c_\mathrm{R}$ (middle row), and dilepton rapidity (lower row). The left (right) plots show the $\mu\mu$ ( $\mathrm{e}\mathrm{e}$ ) channel. The blue histogram represents the signal yield of a hypothetical 2.5 TeV $\mathrm{S_{\mu u}}$ ( $\mathrm{S_{e u}}$ ) with $y_{\mathrm{\mu u}}\,(y_{\mathrm{e u}})=$ 2.0, while the yellow histogram represents the signal yield of a hypothetical 2.5 TeV $\mathrm{V_{\mu u}}\, (\mathrm{V_{e u}})$ with $g_{\mathrm{\mu u}}\,(g_{\mathrm{e u}})=$ 1.0. The black points with error bars represent the data and their statistical uncertainties. The background expectation is shown as stacked histograms. The hatched band shows the total systematic uncertainty in the expected background yield. The lower panels show the ratios of the data to the expectation. The gray bands represent the normalized uncertainty in the predicted yield. The error bars in the ratio plot represent the normalized statistical uncertainty in the data.
png pdf	Figure 2-f: A comparison of data and expected background distributions in the dilepton invariant mass (upper row), $c_\mathrm{R}$ (middle row), and dilepton rapidity (lower row). The left (right) plots show the $\mu\mu$ ( $\mathrm{e}\mathrm{e}$ ) channel. The blue histogram represents the signal yield of a hypothetical 2.5 TeV $\mathrm{S_{\mu u}}$ ( $\mathrm{S_{e u}}$ ) with $y_{\mathrm{\mu u}}\,(y_{\mathrm{e u}})=$ 2.0, while the yellow histogram represents the signal yield of a hypothetical 2.5 TeV $\mathrm{V_{\mu u}}\, (\mathrm{V_{e u}})$ with $g_{\mathrm{\mu u}}\,(g_{\mathrm{e u}})=$ 1.0. The black points with error bars represent the data and their statistical uncertainties. The background expectation is shown as stacked histograms. The hatched band shows the total systematic uncertainty in the expected background yield. The lower panels show the ratios of the data to the expectation. The gray bands represent the normalized uncertainty in the predicted yield. The error bars in the ratio plot represent the normalized statistical uncertainty in the data.
png pdf	Figure 3: The observed data in the dimuon channel and the fitted signal-plus-background templates, shown for the $\mathrm{S_{\mu u}}$ (left) and $\mathrm{S_{\mu d}}$ (right) scenarios with a candidate $m_{\text{LQ}}$ of 2.5 TeV. The black points are the observed data, the stacked histograms represent the backgrounds, and the yellow histogram shows the fitted LQ signal scaled by $-$ 10. Distributions of events are binned in the reconstructed $m_{\ell\ell}$ (vertical red dashed lines), $\|y\|$ (vertical black dashed lines), and $c_\mathrm{R}$ (Section 7). The lower panels show the ratios of the data to the expectation. The gray bands represent the normalized uncertainty in the predicted yield. The error bars in the ratio plot represent the normalized statistical uncertainty in the data.
png pdf	Figure 3-a: The observed data in the dimuon channel and the fitted signal-plus-background templates, shown for the $\mathrm{S_{\mu u}}$ (left) and $\mathrm{S_{\mu d}}$ (right) scenarios with a candidate $m_{\text{LQ}}$ of 2.5 TeV. The black points are the observed data, the stacked histograms represent the backgrounds, and the yellow histogram shows the fitted LQ signal scaled by $-$ 10. Distributions of events are binned in the reconstructed $m_{\ell\ell}$ (vertical red dashed lines), $\|y\|$ (vertical black dashed lines), and $c_\mathrm{R}$ (Section 7). The lower panels show the ratios of the data to the expectation. The gray bands represent the normalized uncertainty in the predicted yield. The error bars in the ratio plot represent the normalized statistical uncertainty in the data.
png pdf	Figure 3-b: The observed data in the dimuon channel and the fitted signal-plus-background templates, shown for the $\mathrm{S_{\mu u}}$ (left) and $\mathrm{S_{\mu d}}$ (right) scenarios with a candidate $m_{\text{LQ}}$ of 2.5 TeV. The black points are the observed data, the stacked histograms represent the backgrounds, and the yellow histogram shows the fitted LQ signal scaled by $-$ 10. Distributions of events are binned in the reconstructed $m_{\ell\ell}$ (vertical red dashed lines), $\|y\|$ (vertical black dashed lines), and $c_\mathrm{R}$ (Section 7). The lower panels show the ratios of the data to the expectation. The gray bands represent the normalized uncertainty in the predicted yield. The error bars in the ratio plot represent the normalized statistical uncertainty in the data.
png pdf	Figure 4: The observed data in the dielectron channel and the fitted signal-plus-background templates, shown for the $\mathrm{S_{e u}}$ (left) and $\mathrm{S_{e d}}$ (right) scenarios with a candidate $m_{\text{LQ}}$ of 2.5 TeV. The black points are the observed data, the stacked histograms represent the backgrounds, and the yellow histogram shows the fitted LQ signal scaled by-10. Distributions of events are binned in the reconstructed $m_{\ell\ell}$ (vertical red dashed lines), $\|y\|$ (vertical black dashed lines), and $c_\mathrm{R}$ (Section 7). The lower panels show the ratios of the data to the expectation. The gray bands represent the normalized uncertainty in the predicted yield. The error bars in the ratio plot represent the normalized statistical uncertainty in the data.
png pdf	Figure 4-a: The observed data in the dielectron channel and the fitted signal-plus-background templates, shown for the $\mathrm{S_{e u}}$ (left) and $\mathrm{S_{e d}}$ (right) scenarios with a candidate $m_{\text{LQ}}$ of 2.5 TeV. The black points are the observed data, the stacked histograms represent the backgrounds, and the yellow histogram shows the fitted LQ signal scaled by-10. Distributions of events are binned in the reconstructed $m_{\ell\ell}$ (vertical red dashed lines), $\|y\|$ (vertical black dashed lines), and $c_\mathrm{R}$ (Section 7). The lower panels show the ratios of the data to the expectation. The gray bands represent the normalized uncertainty in the predicted yield. The error bars in the ratio plot represent the normalized statistical uncertainty in the data.
png pdf	Figure 4-b: The observed data in the dielectron channel and the fitted signal-plus-background templates, shown for the $\mathrm{S_{e u}}$ (left) and $\mathrm{S_{e d}}$ (right) scenarios with a candidate $m_{\text{LQ}}$ of 2.5 TeV. The black points are the observed data, the stacked histograms represent the backgrounds, and the yellow histogram shows the fitted LQ signal scaled by-10. Distributions of events are binned in the reconstructed $m_{\ell\ell}$ (vertical red dashed lines), $\|y\|$ (vertical black dashed lines), and $c_\mathrm{R}$ (Section 7). The lower panels show the ratios of the data to the expectation. The gray bands represent the normalized uncertainty in the predicted yield. The error bars in the ratio plot represent the normalized statistical uncertainty in the data.
png pdf	Figure 5: The observed data in the dimuon channel and the fitted signal-plus-background templates, shown for the $\mathrm{V_{\mu u}}$ (left) and $\mathrm{V_{\mu d}}$ (right) scenario with a candidate $m_{\text{LQ}}$ of 2.5 TeV. The black points are the observed data, the stacked histograms represent the backgrounds, and the yellow histogram shows the fitted LQ signal scaled by-10. Distributions of events are binned in the reconstructed $m_{\ell\ell}$ (vertical red dashed lines), $\|y\|$ (vertical black dashed lines), and $c_\mathrm{R}$ (Section 7). The lower panels show the ratios of the data to the expectation. The gray bands represent the normalized uncertainty in the predicted yield. The error bars in the ratio plot represent the normalized statistical uncertainty in the data.
png pdf	Figure 5-a: The observed data in the dimuon channel and the fitted signal-plus-background templates, shown for the $\mathrm{V_{\mu u}}$ (left) and $\mathrm{V_{\mu d}}$ (right) scenario with a candidate $m_{\text{LQ}}$ of 2.5 TeV. The black points are the observed data, the stacked histograms represent the backgrounds, and the yellow histogram shows the fitted LQ signal scaled by-10. Distributions of events are binned in the reconstructed $m_{\ell\ell}$ (vertical red dashed lines), $\|y\|$ (vertical black dashed lines), and $c_\mathrm{R}$ (Section 7). The lower panels show the ratios of the data to the expectation. The gray bands represent the normalized uncertainty in the predicted yield. The error bars in the ratio plot represent the normalized statistical uncertainty in the data.
png pdf	Figure 5-b: The observed data in the dimuon channel and the fitted signal-plus-background templates, shown for the $\mathrm{V_{\mu u}}$ (left) and $\mathrm{V_{\mu d}}$ (right) scenario with a candidate $m_{\text{LQ}}$ of 2.5 TeV. The black points are the observed data, the stacked histograms represent the backgrounds, and the yellow histogram shows the fitted LQ signal scaled by-10. Distributions of events are binned in the reconstructed $m_{\ell\ell}$ (vertical red dashed lines), $\|y\|$ (vertical black dashed lines), and $c_\mathrm{R}$ (Section 7). The lower panels show the ratios of the data to the expectation. The gray bands represent the normalized uncertainty in the predicted yield. The error bars in the ratio plot represent the normalized statistical uncertainty in the data.
png pdf	Figure 6: The observed data in the dielectron channel and the fitted signal-plus-background templates, shown for the $\mathrm{V_{e u}}$ (left) and $\mathrm{V_{e d}}$ (right) scenario with a candidate $m_{\text{LQ}}$ of 2.5 TeV. The black points are the observed data, the stacked histograms represent the backgrounds, and the yellow histogram shows the fitted LQ signal scaled by-10. Distributions of events are binned in the reconstructed $m_{\ell\ell}$ (vertical red dashed lines), $\|y\|$ (vertical black dashed lines), and $c_\mathrm{R}$ (Section 7). The lower panels show the ratios of the data to the expectation. The gray bands represent the normalized uncertainty in the predicted yield. The error bars in the ratio plot represent the normalized statistical uncertainty in the data.
png pdf	Figure 6-a: The observed data in the dielectron channel and the fitted signal-plus-background templates, shown for the $\mathrm{V_{e u}}$ (left) and $\mathrm{V_{e d}}$ (right) scenario with a candidate $m_{\text{LQ}}$ of 2.5 TeV. The black points are the observed data, the stacked histograms represent the backgrounds, and the yellow histogram shows the fitted LQ signal scaled by-10. Distributions of events are binned in the reconstructed $m_{\ell\ell}$ (vertical red dashed lines), $\|y\|$ (vertical black dashed lines), and $c_\mathrm{R}$ (Section 7). The lower panels show the ratios of the data to the expectation. The gray bands represent the normalized uncertainty in the predicted yield. The error bars in the ratio plot represent the normalized statistical uncertainty in the data.
png pdf	Figure 6-b: The observed data in the dielectron channel and the fitted signal-plus-background templates, shown for the $\mathrm{V_{e u}}$ (left) and $\mathrm{V_{e d}}$ (right) scenario with a candidate $m_{\text{LQ}}$ of 2.5 TeV. The black points are the observed data, the stacked histograms represent the backgrounds, and the yellow histogram shows the fitted LQ signal scaled by-10. Distributions of events are binned in the reconstructed $m_{\ell\ell}$ (vertical red dashed lines), $\|y\|$ (vertical black dashed lines), and $c_\mathrm{R}$ (Section 7). The lower panels show the ratios of the data to the expectation. The gray bands represent the normalized uncertainty in the predicted yield. The error bars in the ratio plot represent the normalized statistical uncertainty in the data.
png pdf	Figure 7: Upper limits at 95% CL on the LQ-fermion couplings, $\|y_{\mathrm{\mu u}}\|$ (left) and $\|y_{\mathrm{\mu d}}\|$ (right), as a function of $m_{\text{LQ}}$ for scalar LQs coupled to muons. The black points show the observed limits, the red line shows the expected limits, and the yellow and blue bands show the variations on the expected limit at 68% and 95% CL, respectively.
png pdf	Figure 7-a: Upper limits at 95% CL on the LQ-fermion couplings, $\|y_{\mathrm{\mu u}}\|$ (left) and $\|y_{\mathrm{\mu d}}\|$ (right), as a function of $m_{\text{LQ}}$ for scalar LQs coupled to muons. The black points show the observed limits, the red line shows the expected limits, and the yellow and blue bands show the variations on the expected limit at 68% and 95% CL, respectively.
png pdf	Figure 7-b: Upper limits at 95% CL on the LQ-fermion couplings, $\|y_{\mathrm{\mu u}}\|$ (left) and $\|y_{\mathrm{\mu d}}\|$ (right), as a function of $m_{\text{LQ}}$ for scalar LQs coupled to muons. The black points show the observed limits, the red line shows the expected limits, and the yellow and blue bands show the variations on the expected limit at 68% and 95% CL, respectively.
png pdf	Figure 8: Upper limits at 95% CL on the LQ-fermion couplings, $\|y_{\mathrm{e u}}\|$ (left) and $\|y_{\mathrm{e d}}\|$ (right), as a function of $m_{\text{LQ}}$ for scalar LQs coupled to electrons. The black points show the observed limits, the red line shows the expected limits, and the yellow and blue bands show the variations on the expected limit at 68% and 95% CL, respectively.
png pdf	Figure 8-a: Upper limits at 95% CL on the LQ-fermion couplings, $\|y_{\mathrm{e u}}\|$ (left) and $\|y_{\mathrm{e d}}\|$ (right), as a function of $m_{\text{LQ}}$ for scalar LQs coupled to electrons. The black points show the observed limits, the red line shows the expected limits, and the yellow and blue bands show the variations on the expected limit at 68% and 95% CL, respectively.
png pdf	Figure 8-b: Upper limits at 95% CL on the LQ-fermion couplings, $\|y_{\mathrm{e u}}\|$ (left) and $\|y_{\mathrm{e d}}\|$ (right), as a function of $m_{\text{LQ}}$ for scalar LQs coupled to electrons. The black points show the observed limits, the red line shows the expected limits, and the yellow and blue bands show the variations on the expected limit at 68% and 95% CL, respectively.
png pdf	Figure 9: Upper limits at 95% CL on the LQ-fermion couplings, $\|g_{\mathrm{\mu u}}\|$ (left) and $\|g_{\mathrm{\mu d}}\|$ (right), as a function of $m_{\text{LQ}}$ for vector LQs coupled to muons. The black points show the observed limits, the red line shows the expected limits, and the yellow and blue bands show the variations on the expected limit at 68% and 95% CL, respectively.
png pdf	Figure 9-a: Upper limits at 95% CL on the LQ-fermion couplings, $\|g_{\mathrm{\mu u}}\|$ (left) and $\|g_{\mathrm{\mu d}}\|$ (right), as a function of $m_{\text{LQ}}$ for vector LQs coupled to muons. The black points show the observed limits, the red line shows the expected limits, and the yellow and blue bands show the variations on the expected limit at 68% and 95% CL, respectively.
png pdf	Figure 9-b: Upper limits at 95% CL on the LQ-fermion couplings, $\|g_{\mathrm{\mu u}}\|$ (left) and $\|g_{\mathrm{\mu d}}\|$ (right), as a function of $m_{\text{LQ}}$ for vector LQs coupled to muons. The black points show the observed limits, the red line shows the expected limits, and the yellow and blue bands show the variations on the expected limit at 68% and 95% CL, respectively.
png pdf	Figure 10: Upper limits at 95% CL on the LQ-fermion couplings, $\|g_{\mathrm{e u}}\|$ (left) and $\|g_{\mathrm{e d}}\|$ (right), as a function of $m_{\text{LQ}}$ for vector LQs coupled to electrons. The black points show the observed limits, the red line shows the expected limits, and the yellow and blue bands show the variations on the expected limit at 68% and 95% CL, respectively.
png pdf	Figure 10-a: Upper limits at 95% CL on the LQ-fermion couplings, $\|g_{\mathrm{e u}}\|$ (left) and $\|g_{\mathrm{e d}}\|$ (right), as a function of $m_{\text{LQ}}$ for vector LQs coupled to electrons. The black points show the observed limits, the red line shows the expected limits, and the yellow and blue bands show the variations on the expected limit at 68% and 95% CL, respectively.
png pdf	Figure 10-b: Upper limits at 95% CL on the LQ-fermion couplings, $\|g_{\mathrm{e u}}\|$ (left) and $\|g_{\mathrm{e d}}\|$ (right), as a function of $m_{\text{LQ}}$ for vector LQs coupled to electrons. The black points show the observed limits, the red line shows the expected limits, and the yellow and blue bands show the variations on the expected limit at 68% and 95% CL, respectively.

Tables
png pdf	Table 1: Properties of the $R_2$ , $\widetilde{R}_2$ , and $U_3$ LQs from Ref. [18]. This paper describes a search for $R_2$ LQs with RL couplings and charge 5/3, $\widetilde{R}_2$ LQs with RL couplings and charge 2/3, and $U_3$ LQs with charges 2/3 and 5/3.
png pdf	Table 2: The contributions of the statistical uncertainty and of individual sources of systematic uncertainty to the total variance in the fitted value of $y_{\text{LQ}}^2$ ( $g_{\text{LQ}}^2$ ) for a scalar (vector) $m_{\text{LQ}}$ of 2.5 TeV. For a given source of uncertainty, the impact is determined by fixing its associated nuisance parameter to the postfit value and evaluating the change in the total uncertainty.
png pdf	Table 3: Best fit values of $A_0$ , $A_4$ , and $y_{\text{LQ}}^2$ for scalar LQ models. The Feldman-Cousins confidence interval for $y_{\text{LQ}}^2$ is shown at 68% CL. Results are shown for a candidate $m_{\text{LQ}}$ of 2.5 TeV.
png pdf	Table 4: Best fit values of $A_0$ , $A_4$ , and $g_{\text{LQ}}^2$ for vector LQ models. The Feldman-Cousins confidence interval for $g_{\text{LQ}}^2$ is shown at 68% CL. Results are shown for a candidate $m_{\text{LQ}}$ of 2.5 TeV.

Summary

A search for the

$t$ -channel exchange of leptoquarks (LQs) coupled to first- and second-gen\-eration fermions has been presented. The search uses proton-proton collision data at

$\sqrt{s}=$ 13 TeV, corresponding to an integrated luminosity of 138 fb

$^{-1}$ . Both scalar and vector LQs are considered, with masses between 1 and 5 TeV, for exclusive LQ couplings to an up or a down quark and a muon or an electron. The

$t$ -channel exchange of an LQ modifies the dilepton angular distributions at masses well below the resonance mass of the LQ. A template fit to the angular and invariant mass distributions of high-mass dilepton events is used to distinguish the signal process from the dominant Drell-Yan background, incorporating the interference effects. No evidence for such LQs is observed. Limits are set at 95% confidence level on the LQ-fermion couplings. For scalar LQs with masses in the 1-5 TeV range, coupling values greater than 0.4-1.3 (0.3-1.0) are excluded for LQs coupled to a muon or an electron, and an up (down) quark, and couplings greater than 0.3-1.4 (0.1-0.5) are excluded for the respective vector LQs. This search is sensitive to LQs with significantly higher masses than prior single- and pair-production searches, establishing stringent limits on LQs with masses up to 5 TeV.

References
1	J. C. Pati and A. Salam	Lepton number as the fourth color	PRD 10 (1974) 275
2	H. Georgi and S. L. Glashow	Unity of all elementary particle forces	PRL 32 (1974) 438
3	G. Senjanovic and A. Sokorac	Light Leptoquarks in SO(10)	Z. Phys. C 20 (1983) 255
4	S. Davidson and S. Descotes-Genon	Minimal flavour violation for leptoquarks	JHEP 11 (2010) 073	1009.1998
5	I. Dorsner and P. Fileviez Perez	Unification without supersymmetry: Neutrino mass, proton decay and light leptoquarks	NPB 723 (2005) 53	hep-ph/0504276
6	W. Buchmuller and D. Wyler	Constraints on SU(5) type leptoquarks	PLB 177 (1986) 377
7	B. Gripaios, M. Nardecchia, and S. A. Renner	Composite leptoquarks and anomalies in $b$ -meson decays	JHEP 05 (2015) 006	1412.1791
8	B. Gripaios	Composite leptoquarks at the LHC	JHEP 02 (2010) 045	0910.1789
9	E. Farhi and L. Susskind	Technicolor	Phys. Rept. 74 (1981) 277
10	S. Dimopoulos	Technicolored signatures	NPB 168 (1980) 69
11	B. Schrempp and F. Schrempp	Light leptoquarks	PLB 153 (1985) 101
12	M. J. Baker et al.	The coannihilation codex	JHEP 12 (2015) 120	1510.03434
13	S.-M. Choi, Y.-J. Kang, H. M. Lee, and T.-G. Ro	Lepto-Quark portal dark matter	JHEP 10 (2018) 104	1807.06547
14	R. Barbier et al.	R-parity violating supersymmetry	Phys. Rept. 420 (2005) 1	hep-ph/0406039
15	Muon $g{-}2$ Collaboration	Measurement of the positive muon anomalous magnetic moment to 0.46 ppm	PRL 126 (2021) 141801	2104.03281
16	S. Borsanyi et al.	Leading hadronic contribution to the muon magnetic moment from lattice QCD	Nature 593 (2021) 51	2002.12347
17	I. Doršner, S. Fajfer, and O. Sumensari	Muon $g{-}2$ and scalar leptoquark mixing	JHEP 06 (2020) 089	1910.03877
18	I. Doršner et al.	Physics of leptoquarks in precision experiments and at particle colliders	Phys. Rept. 641 (2016) 1	1603.04993
19	CMS Collaboration	Search for a third-generation leptoquark coupled to a $\tau$ lepton and a b quark through single, pair, and nonresonant production in proton-proton collisions at $\sqrt{s} =$ 13 TeV	JHEP 05 (2024) 311	CMS-EXO-19-016 2308.07826
20	ATLAS Collaboration	Search for pair production of third-generation leptoquarks decaying into a bottom quark and a $\tau$ -lepton with the ATLAS detector	EPJC 83 (2023) 1075	2303.01294
21	CMS Collaboration	Searches for additional Higgs bosons and for vector leptoquarks in $\tau\tau$ final states in proton-proton collisions at $\sqrt{s} =$ 13 TeV	JHEP 07 (2023) 073	CMS-HIG-21-001 2208.02717
22	ATLAS Collaboration	Search for pairs of scalar leptoquarks decaying into quarks and electrons or muons in $\sqrt{s} =$ 13 TeV $pp$ collisions with the ATLAS detector	JHEP 10 (2020) 112	2006.05872
23	CMS Collaboration	Search for single production of scalar leptoquarks in proton-proton collisions at $\sqrt{s} =$ 8 TeV	PRD 93 (2016) 032005	CMS-EXO-12-043 1509.03750
24	CMS Collaboration	Search for pair production of first-generation scalar leptoquarks at $\sqrt{s} =$ 13 TeV	PRD 99 (2019) 052002	CMS-EXO-17-009 1811.01197
25	CMS Collaboration	Search for pair production of second-generation leptoquarks at $\sqrt{s}=$ 13 TeV	PRD 99 (2019) 032014	CMS-EXO-17-003 1808.05082
26	CMS Collaboration	Search for pair production of first and second generation leptoquarks in proton-proton collisions at $\sqrt{s} =$ 8 TeV	PRD 93 (2016) 032004	CMS-EXO-12-041 1509.03744
27	N. Raj	Anticipating nonresonant new physics in dilepton angular spectra at the LHC	PRD 95 (2017) 015011	1610.03795
28	A. Crivellin, D. Müller, and L. Schnell	Combined constraints on first generation leptoquarks	PRD 103 (2021) 115023	2104.06417
29	I. Bigaran and R. R. Volkas	Getting chirality right: Single scalar leptoquark solutions to the $(g{-}2)_{e,\mu}$ puzzle	PRD 102 (2020) 075037	2002.12544
30	I. Dorsner	Novel leptoquark pair production @LHC	PoS CORFU 111, 2023 link
31	D. J. Robinson, B. Shakya, and J. Zupan	Right-handed neutrinos and R(D $^{*}$ )	JHEP 02 (2019) 119	1807.04753
32	D. Bečirević, N. Košnik, O. Sumensari, and R. Zukanovich Funchal	Palatable leptoquark scenarios for lepton flavor violation in exclusive $b\to s\ell_1\ell_2$ modes	JHEP 11 (2016) 035	1608.07583
33	CMS Collaboration	HEPData record for this analysis	link
34	J. C. Collins and D. E. Soper	Angular distribution of dileptons in high-energy hadron collisions	PRD 16 (1977) 2219
35	CMS Collaboration	Measurement of the Drell-Yan forward-backward asymmetry at high dilepton masses in proton-proton collisions at $\sqrt{s} =$ 13 TeV	JHEP 08 (2022) 063	CMS-SMP-21-002 2202.12327
36	E. Mirkes	Angular decay distribution of leptons from W bosons at NLO in hadronic collisions	NPB 387 (1992) 3
37	E. Mirkes and J. Ohnemus	Angular distributions of Drell-Yan lepton pairs at the Tevatron: Order $\alpha-s^{2}$ corrections and Monte Carlo studies	PRD 51 (1995) 4891	hep-ph/9412289
38	CMS Collaboration	The CMS experiment at the CERN LHC	JINST 3 (2008) S08004
39	CMS Collaboration	Development of the CMS detector for the CERN LHC Run 3	JINST 19 (2024) P05064	CMS-PRF-21-001 2309.05466
40	CMS Collaboration	Performance of the CMS Level-1 trigger in proton-proton collisions at $\sqrt{s} =$ 13 TeV	JINST 15 (2020) P10017	CMS-TRG-17-001 2006.10165
41	CMS Collaboration	The CMS trigger system	JINST 12 (2017) P01020	CMS-TRG-12-001 1609.02366
42	CMS Collaboration	Particle-flow reconstruction and global event description with the CMS detector	JINST 12 (2017) P10003	CMS-PRF-14-001 1706.04965
43	CMS Collaboration	Technical proposal for the Phase-II upgrade of the Compact Muon Solenoid	CMS Technical Proposal CERN-LHCC-2015-010, CMS-TDR-15-02, 2015 CDS
44	CMS Collaboration	Performance of the CMS muon detector and muon reconstruction with proton-proton collisions at $\sqrt{s}=$ 13 TeV	JINST 13 (2018) P06015	CMS-MUO-16-001 1804.04528
45	CMS Collaboration	Electron and photon reconstruction and identification with the CMS experiment at the CERN LHC	JINST 16 (2021) P05014	CMS-EGM-17-001 2012.06888
46	CMS Collaboration	Pileup mitigation at CMS in 13 TeV data	JINST 15 (2020) P09018	CMS-JME-18-001 2003.00503
47	J. Alwall et al.	The automated computation of tree-level and next-to-leading order differential cross sections, and their matching to parton shower simulations	JHEP 07 (2014) 079	1405.0301
48	T. Sjöstrand et al.	An introduction to PYTHIA 8.2	Comput. Phys. Commun. 191 (2015) 159	1410.3012
49	CMS Collaboration	Extraction and validation of a new set of CMS PYTHIA8 tunes from underlying-event measurements	EPJC 80 (2020) 4	CMS-GEN-17-001 1903.12179
50	CMS Collaboration	Event generator tunes obtained from underlying event and multiparton scattering measurements	EPJC 76 (2016) 155	CMS-GEN-14-001 1512.00815
51	R. D. Ball et al.	A first unbiased global NLO determination of parton distributions and their uncertainties	NPB 838 (2010) 136	1002.4407
52	NNPDF Collaboration	Parton distributions for the LHC Run II	JHEP 04 (2015) 040	1410.8849
53	NNPDF Collaboration	Precision determination of the strong coupling constant within a global PDF analysis	EPJC 78 (2018) 408	1802.03398
54	P. Nason	A new method for combining NLO QCD with shower Monte Carlo algorithms	JHEP 11 (2004) 040	hep-ph/0409146
55	S. Frixione, P. Nason, and C. Oleari	Matching NLO QCD computations with parton shower simulations: the POWHEG method	JHEP 11 (2007) 070	0709.2092
56	S. Alioli, P. Nason, C. Oleari, and E. Re	A general framework for implementing NLO calculations in shower Monte Carlo programs: the POWHEG BOX	JHEP 06 (2010) 043	1002.2581
57	S. Frixione, P. Nason, and G. Ridolfi	A positive-weight next-to-leading-order Monte Carlo for heavy flavour hadroproduction	JHEP 09 (2007) 126	0707.3088
58	CMS Collaboration	Investigations of the impact of the parton shower tuning in Pythia8 in the modelling of $\mathrm{t\overline{t}}$ at $\sqrt{s}=$ 8 and 13 TeV	CMS Physics Analysis Summary, 2016 CMS-PAS-TOP-16-021	CMS-PAS-TOP-16-021
59	T. Melia, P. Nason, R. Rontsch, and G. Zanderighi	$W^+ W^-$ , $W Z$ and $Z Z$ production in the POWHEG BOX	JHEP 11 (2011) 078	1107.5051
60	P. Nason and G. Zanderighi	$W^+ W^-$ , $W Z$ and $Z Z$ production in the POWHEG-BOX-V2	EPJC 74 (2014) 2702	1311.1365
61	L. Forthomme	CepGen - A generic central exclusive processes event generator for hadron-hadron collisions	Comput. Phys. Commun. 271 (2022) 108225	1808.06059
62	J. A. M. Vermaseren	Two photon processes at very high-energies	NPB 229 (1983) 347
63	S. Baranov, O. Düenger, H. Shooshtari, and J. Vermaseren	LPAIR: A generator for lepton pair production	in Workshop on Physics at HERA, 1991
64	T. Sjöstrand, S. Mrenna, and P. Z. Skands	PYTHIA 6.4 physics and manual	JHEP 05 (2006) 026	hep-ph/0603175
65	A. Suri and D. R. Yennie	The space-time phenomenology of photon absorbtion and inelastic electron scattering	Annals Phys. 72 (1972) 243
66	J. M. Campbell, R. K. Ellis, and W. T. Giele	A multi-threaded version of MCFM	EPJC 75 (2015) 246	1503.06182
67	T. Gehrmann et al.	$W^+W^-$ production at hadron colliders in next to next to leading order QCD	PRL 113 (2014) 212001	1408.5243
68	M. Czakon and A. Mitov	Top++: A program for the calculation of the top-pair cross-section at hadron colliders	Comput. Phys. Commun. 185 (2014) 2930	1112.5675
69	A. Crivellin and L. Schnell	Complete Lagrangian and set of Feynman rules for scalar leptoquarks	Comput. Phys. Commun. 271 (2022) 108188	2105.04844
70	GEANT4 Collaboration	GEANT4 -- a simulation toolkit	NIM A 506 (2003) 250
71	CMS Collaboration	Performance of the reconstruction and identification of high-momentum muons in proton-proton collisions at $\sqrt{s} =$ 13 TeV	JINST 15 (2020) P02027	CMS-MUO-17-001 1912.03516
72	CMS Collaboration	Measurement of the differential Drell-Yan cross section in proton-proton collisions at $\sqrt{s} =$ 13 TeV	JHEP 12 (2019) 059	CMS-SMP-17-001 1812.10529
73	CMS Collaboration	Search for physics beyond the standard model in dilepton mass spectra in proton-proton collisions at $\sqrt{s}=$ 8 TeV	JHEP 04 (2015) 025	CMS-EXO-12-061 1412.6302
74	Particle Data Group Collaboration	Review of particle physics	PRD 110 (2024) 030001
75	CMS Collaboration	Measurement of the top quark forward-backward production asymmetry and the anomalous chromoelectric and chromomagnetic moments in pp collisions at $\sqrt{s} =$ 13 TeV	JHEP 06 (2020) 146	CMS-TOP-15-018 1912.09540
76	A. Manohar, P. Nason, G. P. Salam, and G. Zanderighi	How bright is the proton? A precise determination of the photon parton distribution function	PRL 117 (2016) 242002	1607.04266
77	A. V. Manohar, P. Nason, G. P. Salam, and G. Zanderighi	The photon content of the proton	JHEP 12 (2017) 046	1708.01256
78	J. S. Conway	Incorporating nuisance parameters in likelihoods for multisource spectra	PHYSTAT (2011) 115	1103.0354
79	CMS Collaboration	Precision luminosity measurement in proton-proton collisions at $\sqrt{s} =$ 13 TeV in 2015 and 2016 at CMS	EPJC 81 (2021) 800	CMS-LUM-17-003 2104.01927
80	CMS Collaboration	CMS luminosity measurement for the 2017 data-taking period at $\sqrt{s} =$ 13 TeV	CMS Physics Analysis Summary, 2018 link	CMS-PAS-LUM-17-004
81	CMS Collaboration	CMS luminosity measurement for the 2018 data-taking period at $\sqrt{s} =$ 13 TeV	CMS Physics Analysis Summary, 2019 link	CMS-PAS-LUM-18-002
82	CMS Collaboration	The CMS statistical analysis and combination tool: \textscCombine	Comput. Softw. Big Sci. 8 (2024) 19	CMS-CAT-23-001 2404.06614
83	G. J. Feldman and R. D. Cousins	Unified approach to the classical statistical analysis of small signals	PRD 57 (1998) 3873	physics/9711021
84	T. Junk	Confidence level computation for combining searches with small statistics	NIM A 434 (1999) 435	hep-ex/9902006
85	A. L. Read	Presentation of search results: The CL $_{\text{s}}$ technique	JPG 28 (2002) 2693
86	G. Cowan, K. Cranmer, E. Gross, and O. Vitells	Asymptotic formulae for likelihood-based tests of new physics	EPJC 71 (2011) 1554	1007.1727