MASS LIMITS for Leptoquarks from Single Production INSPIRE search

2025

ATLS

$\mathit g_{{{\mathit d}} {{\mathit e}}}$ = 1

$>2050$

2024

CMS

B(${{\mathit u}}{{\mathit \tau}}$) = 1

$>1800$

2024

CMS

B(${{\mathit d}}{{\mathit \tau}}$) = 1

$>780$

⁴

2024

CMS

Third generation

$\bf{>1280}$

⁵

2023

ATLS

LQ $\rightarrow$ ${{\mathit b}}{{\mathit \tau}}$

$> 550$

⁶

2021

CMS

Third generation

$\text{none 150 - 740}$

⁷

2018

CMS

Third generation

$>1755$

⁸

KHACHATRYAN

CMS

First generation

$\bf{>660}$

⁹

KHACHATRYAN

CMS

Second generation

$> 304$

¹⁰

ABRAMOWICZ

2012

ZEUS

First generation

$>73$

¹¹

1993

DLPH

Second generation

• • • We do not use the following data for averages, fits, limits, etc. • • •

¹²

2022

ATLS

LQ $\rightarrow$ ${{\mathit u}}{{\mathit e}^{-}}$ , ${{\mathit c}}{{\mathit \mu}^{-}}$

¹³

TUMASYAN

2021

CMS

First generation

¹⁴

DEY

ICCB

${{\mathit \nu}}$ ${{\mathit q}}$ $\rightarrow$ LQ $\rightarrow$ ${{\mathit \nu}}{{\mathit q}}$

¹⁵

2011

Lepton-flavor violation

$> 300$

¹⁶

2011

First generation

¹⁷

ABAZOV

2007

Second generation

$> 295$

¹⁸

AKTAS

2005

First generation

¹⁹

2005

ZEUS

Lepton-flavor violation

$>298$

²⁰

2003

ZEUS

First generation

$>197$

²¹

ABBIENDI

2002

OPAL

First generation

²²

2002

ZEUS

Repl. by CHEKANOV 2005A

$>290$

²³

2001

First generation

$>204$

²⁴

2001

ZEUS

First generation

²⁵

2000

ZEUS

First generation

$>161$

²⁶

1999

DLPH

First generation

$>200$

²⁷

1999

First generation

²⁸

1997

ZEUS

Lepton-flavor violation

$>168$

²⁹

1993

ZEUS

First generation

¹ AAD 2025BN search for single production of a scalar leptoquark in ${{\mathit p}}{{\mathit p}}$ collisions at $\sqrt {s }$ = 13 TeV and at $\sqrt {s }$ = 13.6 TeV. The quoted limit assumes leptoquark production in ${{\mathit d}}{{\mathit e}}$ collisions with coupling strength $\mathit g_{{{\mathit d}} {{\mathit e}}}$ = 1. Masses below 3.1 TeV, 4.3 TeV, and 2.8 TeV are excluded at 95$\%$ CL for $\mathit g_{{{\mathit b}} {{\mathit e}}}$ = 3.5, $\mathit g_{{{\mathit s}} {{\mathit \mu}}}$ = 3.5 and $\mathit g_{{{\mathit b}} {{\mathit \mu}}}$ = 3.5, respectively. See their Figs. $14 - 17$ for exclusion limits in mass-coupling plane.

² HAYRAPETYAN 2024C search for single production of scalar leptoquarks decaying to ${{\mathit q}}{{\mathit \tau}^{+}}$ (${{\mathit q}}$ = ${{\mathit u}}$ , ${{\mathit d}}$ , ${{\mathit s}}$ , ${{\mathit b}}$) in ${{\mathit p}}{{\mathit p}}$ collisions at $\sqrt {s }$ = 13 TeV. The limit quoted above is for a leptoquark produced in ${{\mathit \tau}}{{\mathit u}}$ collisions and the leptoquark coupling strength ${{\mathit \lambda}}$ = 1. See their Fig. 4 for limits in mass-coupling plane.

³ HAYRAPETYAN 2024C search for single production of scalar leptoquarks decaying to ${{\mathit q}}{{\mathit \tau}^{+}}$ (${{\mathit q}}$ = ${{\mathit u}}$ , ${{\mathit d}}$ , ${{\mathit s}}$ , ${{\mathit b}}$) in ${{\mathit p}}{{\mathit p}}$ collisions at $\sqrt {s }$ = 13 TeV. The limit quoted above is for a leptoquark produced in ${{\mathit \tau}}{{\mathit d}}$ collisions and the leptoquark coupling strength ${{\mathit \lambda}}$ = 1. See their Fig. 4 for limits in mass-coupling plane.

⁴ HAYRAPETYAN 2024Z search for scalar and vector leptoquarks decaying to ${{\mathit b}}{{\mathit \tau}}$ and produced through single, pair, and nonresonantly in ${{\mathit p}}{{\mathit p}}$ collisions at $\sqrt {s }$ = 13 TeV. The limit quoted above is derived solely from single production limit and assumes scalar leptoquark decaying to ${{\mathit b}}{{\mathit \tau}}$. The leptoquark coupling strength ${{\mathit \lambda}}$ = 1 is assumed. See their Fig. 7 and Fig. 8 for combined limits in mass-coupling plane.

⁵ AAD 2023BZ search for single production of charge 4/3 scalar leptoquarks decaying to ${{\mathit b}}{{\mathit \tau}^{-}}$, and charge 2/3 vector leptoquarks decaying to ${{\overline{\mathit b}}}{{\mathit \tau}^{-}}$ in ${{\mathit p}}{{\mathit p}}$ collisions at $\sqrt {s }$ = 13 TeV. The limit quoted above assumes a scalar leptoquark with B(${{\mathit b}}{{\mathit \tau}}$) = 1 and the leptoquark coupling strength ${{\mathit \lambda}}$ = 1.0. The limit becomes ${{\mathit M}_{{{LQ}}}}$ $>$ 1530 GeV for ${{\mathit \lambda}}$ = 2.5.

⁶ SIRUNYAN 2021J search for single production of charge $−$1/3 scalar leptoquarks decaying to ${{\mathit t}}{{\mathit \tau}^{-}}$ and ${{\mathit b}}{{\mathit \nu}}$, and charge 2/3 vector leptoquarks decaying to ${{\mathit t}}{{\mathit \nu}}$ and ${{\mathit b}}{{\mathit \tau}^{+}}$ in ${{\mathit p}}{{\mathit p}}$ collisions at $\sqrt {s }$ = 13 TeV. The limit quoted above assumes a scalar leptoquark with B(${{\mathit t}}{{\mathit \tau}}$) = B(${{\mathit b}}{{\mathit \nu}}$) = 0.5 and the leptoquark coupling strength ${{\mathit \lambda}}$ = 1.5. The limit becomes ${{\mathit M}_{{{LQ}}}}$ $>$ 750 GeV for ${{\mathit \lambda}}$ = 2.5.

⁷ SIRUNYAN 2018BJ search for single production of charge 2/3 scalar leptoquarks decaying to ${{\mathit \tau}}{{\mathit b}}$ in ${{\mathit p}}{{\mathit p}}$ collisions at $\sqrt {s }$ = 13 TeV. The limit above assumes B(${{\mathit \tau}}{{\mathit b}}$) = 1 and the leptoquark coupling strength $\lambda $ = 1.

⁸ KHACHATRYAN 2016AG search for single production of charge $\pm{}$1/3 scalar leptoquarks using ${{\mathit e}}{{\mathit e}}{{\mathit j}}$ events in ${{\mathit p}}{{\mathit p}}$ collisions at $\sqrt {s }$ = 8 TeV. The limit above assumes B(${{\mathit e}}{{\mathit q}}$) = 1 and the leptoquark coupling strength ${{\mathit \lambda}}$ = 1.

⁹ KHACHATRYAN 2016AG search for single production of charge $\pm{}$1/3 scalar leptoquarks using ${{\mathit \mu}}{{\mathit \mu}}{{\mathit j}}$ events in ${{\mathit p}}{{\mathit p}}$ collisions at $\sqrt {s }$ = 8 TeV. The limit above assumes B(${{\mathit \mu}}{{\mathit q}}$) = 1 and the leptoquark coupling strength $\lambda $ = 1.

¹⁰ ABRAMOWICZ 2012A limit is for a scalar, weak isoscalar, charge $-1$/3 leptoquark coupled with ${{\mathit e}_{{{R}}}}$. See their Figs. $12 - 17$ and Table 4 for states with different quantum numbers.

¹¹ Limit from single production in ${{\mathit Z}}$ decay. The limit is for a leptoquark coupling of electromagnetic strength and assumes B(${{\mathit \ell}}{{\mathit q}}$) = 2/3. The limit is 77 GeV if first and second leptoquarks are degenerate.

¹² AAD 2022E leptoquarks decaying both to ${{\mathit u}}{{\mathit e}^{-}}$ and ${{\mathit c}}{{\mathit \mu}^{-}}$ are constrained from the comparison of the production cross sections for ${{\mathit e}^{+}}{{\mathit \mu}^{-}}$ and ${{\mathit e}^{-}}{{\mathit \mu}^{+}}$ in ${{\mathit p}}{{\mathit p}}$ collisions at $\sqrt {s }$ = 13 TeV. Scalar leptoquarks with $\mathit M_{LQ}$ $<$ 1880 GeV are excluded for ${{\mathit g}^{eu}}$ = ${{\mathit g}}{}^{{{\mathit \mu}} {{\mathit c}}}$ = 1.

¹³ TUMASYAN 2021D search for energetic jets + $\not E_T$ events in ${{\mathit p}}{{\mathit p}}$ collisions at $\sqrt {s }$ = 13 TeV. The branching fraction for the decay of the leptoquark into an electron neutrino and up quark is assumed to be 100$\%$ ($\beta $ = 0). See their Fig. 12 for exclusion limits in mass-coupling plane.

¹⁴ DEY 2016 use the 2010-2012 IceCube PeV energy data set to constrain the leptoquark production cross section through the ${{\mathit \nu}}$ ${{\mathit q}}$ $\rightarrow$ LQ $\rightarrow$ ${{\mathit \nu}}{{\mathit q}}$ process. See their Figure 4 for the exclusion limit in the mass-coupling plane.

¹⁵ AARON 2011A search for various leptoquarks with lepton-flavor violating couplings. See their Figs.$~2 - 3$ and Tables$~1 - 4$ for detailed limits.

¹⁶ The quoted limit is for a scalar, weak isoscalar, charge $-1$/3 leptoquark coupled with ${{\mathit e}_{{{R}}}}$. See their Figs. $3 - 5$ for limits on states with different quantum numbers.

¹⁷ ABAZOV 2007E search for leptoquark single production through ${{\mathit q}}{{\mathit g}}$ fusion process in ${{\mathit p}}{{\overline{\mathit p}}}$ collisions. See their Fig. 4 for exclusion plot in mass-coupling plane.

¹⁸ AKTAS 2005B limit is for a scalar, weak isoscalar, charge $−$1/3 leptoquark coupled with ${{\mathit e}_{{{R}}}}$. See their Fig. 3 for limits on states with different quantum numbers.

¹⁹ CHEKANOV 2005 search for various leptoquarks with lepton-flavor violating couplings. See their Figs.6--10 and Tables 1--8 for detailed limits.

²⁰ CHEKANOV 2003B limit is for a scalar, weak isoscalar, charge $−$1/3 leptoquark coupled with ${{\mathit e}_{{{R}}}}$. See their Figs.$~11 - 12$ and Table$~$5 for limits on states with different quantum numbers.

²¹ For limits on states with different quantum numbers and the limits in the mass-coupling plane, see their Fig.$~$4 and Fig.$~$5.

²² CHEKANOV 2002 search for various leptoquarks with lepton-flavor violating couplings. See their Figs.$~6 - 7$ and Tables$~5 - 6$ for detailed limits.

²³ For limits on states with different quantum numbers and the limits in the mass-coupling plane, see their Fig.$~$3.

²⁴ See their Fig.$~$14 for limits in the mass-coupling plane.

²⁵ BREITWEG 2000E search for $\mathit F$=0 leptoquarks in ${{\mathit e}^{+}}{{\mathit p}}$ collisions. For limits in mass-coupling plane, see their Fig.$~$11.

²⁶ ABREU 1999G limit obtained from process ${{\mathit e}}$ ${{\mathit \gamma}}$ $\rightarrow\mathit LQ+q$. For limits on vector and scalar states with different quantum numbers and the limits in the coupling-mass plane, see their Fig.$~$4 and Table$~$2.

²⁷ For limits on states with different quantum numbers and the limits in the mass-coupling plane, see their Fig.$~$13 and Fig.$~$14. ADLOFF 1999 also search for leptoquarks with lepton-flavor violating couplings. ADLOFF 1999 supersedes AID 1996B.

²⁸ DERRICK 1997 search for various leptoquarks with lepton-flavor violating couplings. See their Figs.$~$5--8 and Table$~$1 for detailed limits.

²⁹ DERRICK 1993 search for single leptoquark production in ${{\mathit e}}{{\mathit p}}$ collisions with the decay ${{\mathit e}}{{\mathit q}}$ and ${{\mathit \nu}}{{\mathit q}}$. The limit is for leptoquark coupling of electromagnetic strength and assumes B(${{\mathit e}}{{\mathit q}}$) = B(${{\mathit \nu}}{{\mathit q}}$) = 1/2. The limit for B(${{\mathit e}}{{\mathit q}}$) = 1 is 176 GeV. For limits on states with different quantum numbers, see their Table$~$3.

References:

2025BN

JHEP 2512 180

Search for resonant leptoquark production via lepton-jet signatures in $pp$ collisions at $\sqrt{s} = 13$ TeV and $\sqrt{s} = 13.6$ TeV with the ATLAS detector

2024Z

JHEP 2405 311

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

2024C

PRL 132 061801

Search for scalar leptoquarks produced in lepton-quark collisions and coupled to $\tau$ leptons

2023BZ

JHEP 2310 001

Search for leptoquarks decaying into the b$\tau$ final state in $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector

2022E

PL B830 137106

A search for an unexpected asymmetry in the production of e+?? and e??+ pairs in proton?proton collisions recorded by the ATLAS detector at

\sqrt{s} = 13

TeV

2021J

PL B819 136446

Search for singly and pair-produced leptoquarks coupling to third-generation fermions in proton-proton collisions at $\sqrt{s} =$ 13 TeV

TUMASYAN

2021D

JHEP 2111 153

Search for new particles in events with energetic jets and large missing transverse momentum in proton-proton collisions at $ \sqrt{s} $ = 13 TeV

2018BJ

JHEP 1807 115

Search for a singly produced third-generation scalar leptoquark decaying to a $\tau$ lepton and a bottom quark in proton-proton collisions at $\sqrt{s} =$ 13 TeV

DEY

JHEP 1604 187

Constraints on Leptoquark Models from IceCube Data

KHACHATRYAN

2016AG

PR D93 032005

Search for Single Production of Scalar Leptoquarks in Proton-Proton Collisions at $\sqrt {s }$ = 8 TeV

Also

PR D95 039906 (errat.)

Erratum to KHACHATRYAN 2016AG: Search for Single Production of Scalar Leptoquarks in Proton-Proton Collisions at $\sqrt {s }$ = 8 TeV

ABRAMOWICZ

2012A

PR D86 012005

Search for First-Generation Leptoquarks at HERA

2011A

PL B701 20

Search for Lepton Flavour Violation at HERA

2011B

PL B704 388

Search for First Generation Leptoquarks in ${{\mathit e}}{{\mathit p}}$ Collisions at HERA

ABAZOV

2007E

PL B647 74

Search for Single Production of Scalar Leptoquarks in ${{\mathit p}}{{\overline{\mathit p}}}$ Collisions Decaying into Muons and Quarks with the ${D0}$ Detector

AKTAS

2005B

PL B629 9

Search for Leptoquark Bosons in ${{\mathit e}}{{\mathit p}}$ Collisions at HERA

2005A

EPJ C44 463

Search for Lepton-Flavor Violation at HERA

2003B

PR D68 052004

A Search for Resonance Decays to Lepton + Jet at HERA and Limits on Leptoquarks

ABBIENDI

2002B

PL B526 233

Search for Leptoquarks in Electron Photon Scattering at $\sqrt {s }_{ee}$ up to 209 GeV at LEP

2002

PR D65 092004

Search for Lepton Flavor Violation in ${{\mathit e}^{+}}{{\mathit p}}$ Collisions at HERA

2001C

PL B523 234

A Search for Leptoquark Bosons in ${{\mathit e}^{-}}$ ${{\mathit p}}$ Collisions at HERA

2001

PR D63 052002

Search for Resonance Decays to an ${{\overline{\mathit \nu}}}$ plus Jet in ${{\mathit e}^{+}}$ ${{\mathit p}}$ Scattering at DESY HERA

2000E

EPJ C16 253

Search for Resonances Decaying to ${{\mathit e}^{+}}$ jet in ${{\mathit e}^{+}}$ ${{\mathit p}}$ Interactions at HERA

1999G

PL B446 62

Search for Leptoquarks and FCNC in ${{\mathit e}^{+}}$ ${{\mathit e}^{-}}$ Annihilations at $\sqrt {s }$ = 183 GeV

1999

EPJ C11 447

A Search for Leptoquark Bosons and Lepton Flavor Violation in ${{\mathit e}^{+}}$ ${{\mathit p}}$ Collisions at HERA

Also

EPJ C14 553 (errat.)

Erratum: ADLOFF 1999 A Search for Leptoquark Bosons and Lepton Flavour Violation in ${{\mathit e}^{+}}$ ${{\mathit p}}$ Collisions at HERA

1997

ZPHY C73 613

Search for Lepton Flavor Violation in ${{\mathit e}}{{\mathit p}}$ Collisions at 300 GeV Center of Mass Energy

1993J

PL B316 620

Limits on the Production of Scalar Leptoquarks from ${{\mathit Z}^{0}}$ Decays at LEP