nLab leptoquark

Idea

Leptoquarks is the name given to hypothetical fundamental particles which combine the properties of both quarks and leptons from the standard model of particle physics.

They naturally arise in grand unified theories (e.g. Murayama-Yanagida 92, also AFG 17, III.A)

Properties

Experimental hints

The existence of leptoquarks could potentially explain both

1. the apparently observed flavour anomalies

   (Bauer-Neubert 16, CCDM 16, CCL 17, Crivellin 17 Falkowski17, Müeller 18, Matsuzaki-Nishiwaki 18, Monteux-Rajaraman 18, AMST 18, BDFKFS 18, Crivellin 18, MMR 18, Blanke-Crivellin 18, Kumar-London 19, section 2.2.1, MVT 19, MVK 19, Cata-Mannel 19)

2. the apparently observed anomaly in the anomalous magnetic moments of the muon and also of the electron (CCDM 16, Müller 18)

From Crivellin 18, p. 2:

the global fit $[$ to flavour anomalies $]$ even shows compelling evidence for New Physics $[$… $]$ The vector leptoquark (LQ) $SU(2)_L$ singlet with hypercharge $-4/3$ arising in the famous Pati-Salam model is capable of explaining all the $[$flavour $]$ anomalies and therefore several attempts to construct a UV completion for this LQ to address the anomalies have been made. It can give a sizeable effect in $b \to c(u)\tau \nu$ data without violating bounds from $b \to s(d)\nu \bar \nu$ and/or direct searches, provides (at tree level) a $C_9 = - C_{10}$ solution to $b \to s \ell^+ \ell^-$ data and does not lead to proton decay at any order in perturbation theory.

Experimental constraints

Constraints on the possible parameter space for leptoquarks from LHC data (BGGSS 18, BSS 18, ATLAS 19)

Theoretical conceptualization

Leptoquarks naturally arise in grand unified theories (…, Murayama-Yanagida 92, BDFKFS 18)

References

General

• Nima Assad, Bartosz Fornal, Benjamin Grinstein, Baryon Number and Lepton Universality Violation in Leptoquark and Diquark Models, Phys. Lett. B777 (2018) 324-331 (arXiv:1708.06350)

• Achintya Rao, The hunt for leptoquarks is on, 2018

Leptoquark effective field theory:

• Valerio Gherardi, David Marzocca, Elena Venturini, Matching scalar leptoquarks to the SMEFT at one loop (arXiv:2003.12525)

• Andreas Crivellin, Christoph Greub, Dario Müller, Francesco Saturnino, Scalar Leptoquarks in Leptonic Processes (arXiv:2010.06593)

See also

• Wikipedia, Leptoquark

Experiment

Constraints from experiment (LHC):

• I. Doršner, S. Fajfer, A. Greljo, J. F. Kamenik, N. Košnik, Physics of leptoquarks in precision experiments and at particle colliders, Physics Reports Volume 641, 17 June 2016, Pages 1-68 (arXiv:1603.04993)

• M. Tanabashi et al. (Particle Data Group), 115. Leptoquarks Phys. Rev. D 98, 030001 (2018) (pdf)

• CMS Collaboration, Search for third-generation scalar leptoquarks decaying to a top quark and a $\tau$ lepton at $\sqrt{s} = 13$ TeV, Eur. Phys. J. C 78 (2018) 707 (arXiv:1803.02864)

• Andrei Angelescu, Damir Bečirević, Darius A. Faroughy, Olcyr Sumensari, Closing the window on single leptoquark solutions to the $B$-physics anomalies, JHEP10(2018)183 (arXiv:1808.08179)

• Aritra Biswas, Dilip Kumar Ghosh, Nivedita Ghosh, Avirup Shaw, Abhaya Kumar Swain, Novel collider signature of $U_1$ Leptoquark and $B \to \pi$ observables (arXiv:1808.04169)

• Aritra Biswas, Avirup Shaw, Abhaya Kumar Swain, Collider signature of $V_2$ Leptoquark with $b \to s$ flavour observables (arXiv:1811.08887)

• Salvatore Rappoccio, section 6 of The experimental status of direct searches for exotic physics beyond the standard model at the Large Hadron Collider, Reviews in Physics 4 (2019) 100027 (arXiv:1810.10579)

• ATLAS collaboration, Searches for scalar leptoquarks and differential cross-section measurements in dilepton-dijet events in proton-proton collisions at a centre-of-mass energy of s√ = 13 TeV with the ATLAS experiment (arXiv:1902.00377)

• ZEUS Collaboration, Limits on contact interactions and leptoquarks at HERA (arXiv:1902.03048)

Alternative detection channel:

• Priyotosh Bandyopadhyay, Saunak Dutta, Anirban Karan, Investigating the Production of Leptoquarks by Means of Zeros of Amplitude at Photon Electron Collider (arXiv:2003.11751)

Claim that $U(1)$-leptoquark at 1.5 TeV could both explain the flavor anomalies as well as fit all current experimental constraints:

• Arvind Bhaskar, Diganta Das, Tanumoy Mandal, Subhadip Mitra, Cyrin Neeraj, Precise LHC limits on the U1 leptoquark parameter space (arXiv:2110.07638)

Claim of an apparent $3\sigma$-excess of possible leptoquark decay products:

• CMS Collaboration, The search for a third-generation leptoquark coupling to a τ lepton and a b quark through single, pair and nonresonant production at $\sqrt{s} = 13 TeV$ (2022) [cds:2815309]

  Measurements of [B meson decay rates] collectively deviate from the SM predictions by about four standard deviations. New physics with larger couplings to the third-generation quarks and leptons could explain this anomaly. Leptoquark (LQ) models have recently received onsiderable theoretical interest as a possible explanation.

  $[\cdots]$

  For a representative LQ mass of 2 TeV and a coupling strength of $2.5$, an excess with a significance of 3.4 standard deviations above the standard model expectation is observed in the data.

Relation to flavour anomalies

As a potential solution of the apparent B meson flavour anomaly:

• Martin Bauer, Matthias Neubert, One Leptoquark to Rule Them All: A Minimal Explanation for $R_{D^{(\ast)}}$, $R_K$ and $(g-2)_\mu$, Phys. Rev. Lett. 116, 141802 (2016) (arXiv:1511.01900)

• Estefania Coluccio Leskow, Andreas Crivellin, Giancarlo D’Ambrosio, Dario Müller, $(g-2)_\mu$, Lepton Flavour Violation and Z Decays with Leptoquarks: Correlations and Future Prospects, Phys. Rev. D 95, 055018 (2017) (arXiv:1612.06858)

• Yi Cai, John Gargalionis, Michael A. Schmidt, Raymond R. Volkas, Reconsidering the One Leptoquark solution: flavor anomalies and neutrino mass (arXiv:1704.05849)

• Lorenzo Calibbi, Andreas Crivellin, Tianjun Li, A model of vector leptoquarks in view of the $B$-physics anomalies, Phys. Rev. D 98, 115002 (2018) (arXiv:1709.00692)

• Andreas Crivellin, New Physics in Flavour Observables (arXiv:1706.00929)

• Adam Falkowski, Leptoquarks strike back, November 2017

• Dario Müller, Leptoquarks in Flavour Physics, EPJ Web of Conferences 179, 01015 (2018) (arXiv:1801.03380)

• Shinya Matsuzaki, Kenji Nishiwaki, Kei Yamamoto, Simultaneous interpretation of K and B anomalies in terms of chiral-flavorful vectors (arXiv:1806.02312)

• Angelo Monteux, Arvind Rajaraman, B Anomalies and Leptoquarks at the LHC: Beyond the Lepton-Quark Final State, Phys. Rev. D 98, 115032 (2018) (arXiv:1803.05962)

• Ufuk Aydemir, Djordje Minic, Chen Sun, Tatsu Takeuchi, $B$-decay anomalies and scalar leptoquarks in unified Pati-Salam models from noncommutative geometry, JHEP 09 (2018) 117 (arXiv:1804.05844)

• Damir Bečirević, Ilja Doršner, Svjetlana Fajfer, Nejc Košnik, Darius A. Faroughy, Olcyr Sumensari, Scalar leptoquarks from GUT to accommodate the $B$-physics anomalies, Phys. Rev. D 98, 055003 (2018) (arXiv:1806.05689)

• Tanumoy Mandal, Subhadip Mitra, Swapnil Raz, $R_{D^{(\ast)}}$ in minimal leptoquark scenarios: impact of interference on the exclusion limits from LHC data (arXiv:1811.03561)

• Jason Aebischer, Andreas Crivellin, Christoph Greub, QCD Improved Matching for Semi-Leptonic B Decays with Leptoquarks (arXiv:1811.08907)

• Jacky Kumar, David London, New physics in $b \to s e^+ e^-$? (arXiv:1901.04516)

• Ivo de Medeiros Varzielas, Jim Talbert, Simplified Models of Flavourful Leptoquarks (arXiv:1901.10484)

• Michael J. Baker, Javier Fuentes-Martin, Gino Isidori, Matthias König, High-pT Signatures in Vector-Leptoquark Models (arXiv:1901.10480)

• Natascia Vignaroli, Seeking leptoquarks in the $t \bar t$ plus missing energy channel at the high-luminosity LHC (arXiv:1808.10309)

• Ufuk Aydemir, Tanumoy Mandal, Subhadip Mitra, A single TeV-scale scalar leptoquark in SO(10) grand unification and B-decay anomalies (arXiv:1902.08108)

• Ivo de Medeiros Varzielas, Stephen F. King, Origin of Yukawa couplings for Higgs and leptoquarks (arXiv:1902.09266)

• Oscar Cata, Thomas Mannel, Linking lepton number violation with $B$ anomalies (arXiv:1903.01799)

• Bhubanjyoti Bhattacharya, Alakabha Datta, Saeed Kamali, David London, CP Violation in $\bar B^0 \to D^{\ast +} \mu^- \bar \nu_\mu$, (arXiv:1903.02567)

• Han Yan, Ya-Dong Yang, Xing-Bo Yuan, Phenomenology of $b \to c \tau \bar \nu$ decays in a scalar leptoquark model (arXiv:1905.01795)

• Alakabha Datta, Divya Sachdeva, John Waite, A unified explanation of $b \to s\mu^= \mu^-$ anomalies, neutrino masses and $B \to \pi K$ puzzle (arXiv:1905.04046)

• Andrei Angelescu, Single Leptoquark Solutions to the $B$-physics Anomalies, contribution to the 2019 EW session of the 54th Rencontres de Moriond (arXiv:1905.06044)

• Andreas Crivellin, Francesco Saturnino, Explaining the Flavor Anomalies with a Vector Leptoquark (Moriond 2019 update) (arXiv:1906.01222)

• Innes Bigaran, John Gargalionis, Raymond R. Volkas, A near-minimal leptoquark model for reconciling flavour anomalies and generating radiative neutrino masses (arXiv:1906.01870)

• Javier Fuentes-Martin, Gino Isidori, Matthias König, Nudzeim Selimovic, Vector Leptoquarks Beyond Tree Level (arxiv:1910.13474)

• Gudrun Hiller, Dennis Loose, Ivan Nišandžić, Flavorful leptoquarks at the LHC and beyond: Spin 1 (arXiv:2103.12724)

• J. Kriewald, C. Hati, J. Orloff, A. M. Teixeira, A combined explanation of the B-meson decay anomalies with a single vector leptoquark (arXiv:2012.06315)

• Andrei Angelescu, Damir Bečirević, Darius A. Faroughy, Florentin Jaffredo, Olcyr Sumensari, On the single leptoquark solutions to the B-physics anomalies (arXiv:2103.12504)

• Jason Aebischer, Gino Isidori, Marko Pesut, Ben A. Stefanek, Felix Wilsch, Confronting the vector leptoquark hypothesis with new low- and high-energy data [arXiv:2210.13422]

within GUT-models and specifically within Pati-Salam models:

• Julian Heeck, Daniele Teresi, Pati-Salam explanations of the B-meson anomalies, JHEP 12 (2018) 103 (arXiv:1808.07492)

• Julian Heeck, Daniele Teresi, Pati-Salam and lepton universality in B decays (arXiv:1905.05211)

• Oleg Popov, Michael A. Schmidt, Graham White, $R_2$ as a single leptoquark solution to $R_{D^{(\ast)}}$ and $R_{K^{(\ast)}}$ (arXiv:1905.06339)

• Andreas Crivellin, Francesco Saturnino, Correlating Tauonic B Decays to the Neutron EDM via a Scalar Leptoquark (arXiv:1905.08257)

• Michal Malinský, Lepton non-universality in $B$-decays in the minimal leptoquark gauge model (arXiv:1906.09174)

• Jordan Bernigaud, Ivo de Medeiros Varzielas, Jim Talbert, Finite Family Groups for Fermionic and Leptoquark Mixing Patterns (arXiv:1906.11270)

• Junichiro Kawamura, Stuart Raby, Andreas Trautner, Complete Vector-like Fourth Family and new $U(1)'$ for Muon Anomalies (arXiv:1906.11297)

• Leandro Da Rold, Federico Lamagna, A vector leptoquark for the B-physics anomalies from a composite GUT (arXiv:1906.11666)

• C. Hati, J. Kriewald, J. Orloff, A.M. Teixeira, A nonunitary interpretation for a single vector leptoquark combined explanation to the B-decay anomalies (arXiv:1907.05511)

• Shyam Balaji, Michael A. Schmidt, A unified $SU(4)$ theory for the $R_D^{(\ast)}$ and $R_K^{(\ast)}$ anomalies (arXiv:1911.08873)

• Shaikh Saad, Anil Thapa, A Common Origin of Neutrino Masses and $R_{D^\ast}$, $R_{K^\ast}$ Anomalies (arXiv:2004.07880)

• P. S. Bhupal Dev, Rukmani Mohanta, Sudhanwa Patra, Suchismita Sahoo, Unified explanation of flavor anomalies, radiative neutrino mass and ANITA anomalous events in a vector leptoquark model (arXiv:2004.09464)

• Suman Kumbhakar, Rukmani Mohanta, Investigating the effect of $U_1$ vector leptoquark on $b \to u \tau \bar\nu$ mediated B decays (arXiv:2008.04016)

• Valerio Gherardi, David Marzocca, Elena Venturini, Low-energy phenomenology of scalar leptoquarks at one-loop accuracy (arXiv:2008.09548)

• Andreas Crivellin, Dario Mueller, Francesco Saturnino, Leptoquarks in Oblique Corrections and Higgs Signal Strength: Status and Prospects (arXiv:2006.10758)

• Marco Ciuchini, Marco Fedele, Enrico Franco, Ayan Paul, Luca Silvestrini, Mauro Valli, Lessons from the $B^{0,+} \to B^{\ast, 0,+} \mu^+ \mu^-$ angular analysis (arXiv:2011.01212)

In the Standard Model Effective Theory (SMEFT) [41, 42], the significance of NewPhysics from the global $b \to s \ell^+ \ell^-$ analysis increases with the inclusion of new data, reaching a maximum of almost 6σ for the simple hypothesis of a non-vanishing $[$leptoquark contribution$]$.

• Admir Greljo, Peter Stangl, Anders Eller Thomsen, A Model of Muon Anomalies (arXiv:2103.13991)

• Andreas Crivellin, Luc Schnell, Complete Set of Feynman Rules for Scalar Leptoquarks (arXiv:2105.04844)

• We-Fu Chang, One colorful resolution to the neutrino mass generation, three lepton flavor universality anomalies, and the Cabibbo angle anomaly (arXiv:2105.06917)

• Mario Fernández Navarro, Stephen F. King, $B$-anomalies in a twin Pati-Salam theory of flavour [arXiv:2209.00276]

and on branes:

• Javier Fuentes-Martin, Gino Isidori, Julie Pagès, Ben A. Stefanek,

  Flavor Non-universal Pati-Salam Unification and Neutrino Masses, Physics Letters B Volume 820, 10 September 2021, 136484 (arXiv:2012.10492, talk recording)

leptoquarks for explaining both the flavour anomalies and the (g-2)-anomalies:

• Hyun Min Lee, Leptoquark Option for B-meson Anomalies and Leptonic Signatures (arXiv:2104.02982)

• Mingxuan Du, Jinhan Liang, Zuowei Liu, Van Que Tran, A vector leptoquark interpretation of the muon $g-2$ and $B$ anomalies (arXiv:2104.05685)

• Kayoung Ban, Yongsoo Jho, Youngjoon Kwon, Seong Chan Park, Seokhee Park, Po-Yan Tseng, A comprehensive study of vector leptoquark on the B-meson and Muon $g-2$ anomalies (arXiv:2104.06656)

• Alexandre Carvunis, Andreas Crivellin, Diego Guadagnoli, Shireen Gangal, The Forward-Backward Asymmetry in $B \to D^\ast \ell \nu$: One more hint for Scalar Leptoquarks? (arXiv:2106.09610)

• Alessandra D’Alise et al., Standard model anomalies: Lepton flavour non-universality, g-2 and W-mass $[$arXiv:2204.03686$]$

A leptoquark model meant to address all of the flavour anomalies, the (g-2)-anomaly and the Cabibbo anomaly at once:

• David Marzocca, Sokratis Trifinopoulos, A Minimal Explanation of Flavour Anomalies: B-Meson Decays, Muon Magnetic Moment, and the Cabbibo Angle (arXiv:2104.05730)

and within Randall-Sundrum models

• Andreas Crivellin, Explaining the Flavour Anomalies with the Pati-Salam Vector Leptoquark, PoS LHCP2018 (2018) 269 (spire:1713260, doi:10.22323/1.321.0269)

• Monika Blanke, Andreas Crivellin, $B$ Meson Anomalies in a Pati-Salam Model within the Randall-Sundrum Background, Phys. Rev. Lett. 121, 011801 (2018) (arXiv:1801.07256)

and as a possible explanation also of the anomalies seen at the ANITA experiment:

• Bhavesh Chauhan, Subhendra Mohanty, A common leptoquark solution of flavor and ANITA anomalies (arXiv:1812.00919)

As dark matter candidates

Leptoquarks as candidates for dark matter:

• Francesco D’Eramo, Nejc Košnik, Federico Pobbe, Aleks Smolkovič, Olcyr Sumensari, Leptoquarks and Real Singlets: A Richer Scalar Sector Behind the Origin of Dark Matter (arXiv:2012.05743)

• Genevieve Bélanger et al. Leptoquark Manoeuvres in the Dark: a simultaneous solution of the dark matter problem and the RD anomalies (arXiv:2111.08027)

Appearance in GUTs

Appearance in GUT-theories:

• H. Murayama, T. Yanagida, A viable $SU(5)$ GUT with light leptoquark bosons, Mod.Phys.Lett. A7 (1992) 147-152 (spire:315898, doi:10.1142/S0217732392000070)

• Heek-Teresi 18, Heek-Teresi 19

In string phenomenology

Discussion of leptoquarks within string phenomenology:

• Ricardo Perez-Martinez, Saul Ramos-Sanchez, Patrick K.S. Vaudrevange , The landscape of promising non-supersymmetric string models (arXiv:2105.03460)