Abstract
If electroweak symmetry breaking arises via strongly-coupled physics, the observed suppression of flavour-changing processes suggests that fermion masses should arise via mixing of elementary fermions with composite fermions of the strong sector. The strong sector then carries colour charge, and may contain composite leptoquark states, arising either as TeV scale resonances, or even as light, pseudo-Nambu-Goldstone bosons. The latter, since they are coupled to colour, get a mass of the order of several hundred GeV, beyond the reach of current searches at the Tevatron. The same generic mechanism that suppresses flavour-changing processes suppresses leptoquark-mediated rare processes, making it conceivable that the many stringent constraints may be evaded. The leptoquarks couple predominantly to third-generation quarks and leptons, and the prospects for discovery at LHC appear to be good. As an illustration, a model based on the Pati-Salam symmetry is described, and its embedding in models with a larger symmetry incorporating unification of gauge couplings, which provide additional motivation for leptoquark states at or below the TeV scale, is discussed.
Article PDF
Similar content being viewed by others
Avoid common mistakes on your manuscript.
References
D.B. Kaplan, Flavor at SSC energies: a new mechanism for dynamically generated fermion masses, Nucl. Phys. B 365 (1991) 259 [SPIRES].
T. Gherghetta and A. Pomarol, Bulk fields and supersymmetry in a slice of AdS, Nucl. Phys. B 586 (2000) 141 [hep-ph/0003129] [SPIRES].
S.J. Huber, Flavor violation and warped geometry, Nucl. Phys. B 666 (2003) 269 [hep-ph/0303183] [SPIRES].
K. Agashe, G. Perez and A. Soni, Flavor structure of warped extra dimension models, Phys. Rev. D 71 (2005) 016002 [hep-ph/0408134] [SPIRES].
C. Csáki, A. Falkowski and A. Weiler, The flavor of the composite Pseudo-Goldstone Higgs, JHEP 09 (2008) 008 [arXiv:0804.1954] [SPIRES].
S. Casagrande, F. Goertz, U. Haisch, M. Neubert and T. Pfoh, Flavor physics in the Randall-Sundrum model: I. Theoretical setup and electroweak precision tests, JHEP 10 (2008) 094 [arXiv:0807.4937] [SPIRES].
M.E. Albrecht, M. Blanke, A.J. Buras, B. Duling and K. Gemmler, Electroweak and flavour structure of a warped extra dimension with custodial protection, JHEP 09 (2009) 064 [arXiv:0903.2415] [SPIRES].
M.A. Luty and T. Okui, Conformal technicolor, JHEP 09 (2006) 070 [hep-ph/0409274] [SPIRES].
R. Rattazzi, V.S. Rychkov, E. Tonni and A. Vichi, Bounding scalar operator dimensions in 4D CFT, JHEP 12 (2008) 031 [arXiv:0807.0004] [SPIRES].
V.S. Rychkov and A. Vichi, Universal constraints on conformal operator dimensions, Phys. Rev. D 80 (2009) 045006 [arXiv:0905.2211] [SPIRES].
K. Agashe, R. Contino and R. Sundrum, Top compositeness and precision unification, Phys. Rev. Lett. 95 (2005) 171804 [hep-ph/0502222] [SPIRES].
J.C. Pati and A. Salam, Lepton number as the fourth color, Phys. Rev. D 10 (1974) 275 [Erratum ibid. D 11 (1975) 703] [SPIRES].
K. Agashe and G. Servant, Warped unification, proton stability and dark matter, Phys. Rev. Lett. 93 (2004) 231805 [hep-ph/0403143] [SPIRES].
K. Agashe and G. Servant, Baryon number in warped GUTs: Model building and (dark matter related) phenomenology, JCAP 02 (2005) 002 [hep-ph/0411254] [SPIRES].
D.B. Kaplan and H. Georgi, SU(2) × U(1) breaking by vacuum misalignment, Phys. Lett. B 136 (1984) 183 [SPIRES].
H. Georgi and D.B. Kaplan, Composite Higgs and custodial SU(2), Phys. Lett. B 145 (1984) 216 [SPIRES].
M.J. Dugan, H. Georgi and D.B. Kaplan, Anatomy of a composite Higgs model, Nucl. Phys. B 254 (1985) 299 [SPIRES].
K. Agashe, R. Contino and A. Pomarol, The minimal composite Higgs model, Nucl. Phys. B 719 (2005) 165 [hep-ph/0412089] [SPIRES].
R. Contino, L. Da Rold and A. Pomarol, Light custodians in natural composite Higgs models, Phys. Rev. D 75 (2007) 055014 [hep-ph/0612048] [SPIRES].
R. Barbieri, B. Bellazzini, V.S. Rychkov and A. Varagnolo, The Higgs boson from an extended symmetry, Phys. Rev. D 76 (2007) 115008 [arXiv:0706.0432] [SPIRES].
A.D. Medina, N.R. Shah and C.E.M. Wagner, Gauge-Higgs unification and radiative electroweak symmetry breaking in warped extra dimensions, Phys. Rev. D 76 (2007) 095010 [arXiv:0706.1281] [SPIRES].
G. Panico, E. Ponton, J. Santiago and M. Serone, Dark matter and electroweak symmetry breaking in models with warped extra dimensions, Phys. Rev. D 77 (2008) 115012 [arXiv:0801.1645] [SPIRES].
Y. Hosotani, K. Oda, T. Ohnuma and Y. Sakamura, Dynamical electroweak symmetry breaking in SO(5) × U(1) gauge-Higgs unification with top and bottom quarks, Phys. Rev. D 78 (2008) 096002 [Erratum ibid. D 79 (2009) 079902] [arXiv:0806.0480] [SPIRES].
C. Anastasiou, E. Furlan and J. Santiago, Realistic composite Higgs models, Phys. Rev. D 79 (2009) 075003 [arXiv:0901.2117] [SPIRES].
G.F. Giudice, C. Grojean, A. Pomarol and R. Rattazzi, The strongly-interacting light higgs, JHEP 06 (2007) 045 [hep-ph/0703164] [SPIRES].
A. Manohar and H. Georgi, Chiral quarks and the nonrelativistic quark model, Nucl. Phys. B 234 (1984) 189 [SPIRES].
H. Georgi and L. Randall, Flavor conserving CP-violation in invisible axion models, Nucl. Phys. B 276 (1986) 241 [SPIRES].
R. Contino, T. Kramer, M. Son and R. Sundrum, Warped/composite phenomenology simplified, JHEP 05 (2007) 074 [hep-ph/0612180] [SPIRES].
K. Agashe, R. Contino, L. Da Rold and A. Pomarol, A custodial symmetry for \( Zb\bar b \), Phys. Lett. B 641 (2006) 62 [hep-ph/0605341] [SPIRES].
S. Davidson, G. Isidori and S. Uhlig, Solving the flavour problem with hierarchical fermion wave functions, Phys. Lett. B 663 (2008) 73 [arXiv:0711.3376] [SPIRES].
C. Csaki, A. Falkowski and A. Weiler, The flavor of the composite pseudo-Goldstone Higgs, op. cit..
B.A. Campbell and A. Ismail, Leptonic pion decay and physics beyond the electroweak Standard model, arXiv:0810.4918 [SPIRES].
Y. Kuno and Y. Okada, Muon decay and physics beyond the standard model, Rev. Mod. Phys. 73 (2001) 151 [hep-ph/9909265] [SPIRES].
S. Davidson, D.C. Bailey and B.A. Campbell, Model independent constraints on leptoquarks from rare processes, Z. Phys. C 61 (1994) 613 [hep-ph/9309310] [SPIRES].
SINDRUM II collaboration, W.H. Bertl et al., A search for μ − e conversion in muonic gold, Eur. Phys. J. C 47 (2006) 337 [SPIRES].
H.K. Dreiner, G. Polesello and M. Thormeier, Bounds on broken R-parity from leptonic meson decays, Phys. Rev. D 65 (2002) 115006 [hep-ph/0112228] [SPIRES].
Particle Data Group collaboration, C. Amsler et al., Review of particle physics, Phys. Lett. B 667 (2008) 1 [SPIRES].
P. Fileviez Perez, T. Han, T. Li and M.J. Ramsey-Musolf, Leptoquarks and neutrino masses at the LHC, Nucl. Phys. B 819 (2009) 139 [arXiv:0810.4138] [SPIRES].
H.K. Dreiner, M. Krämer and B. O’Leary, Bounds on R-parity violation from leptonic and semi- leptonic meson decays, Phys. Rev. D 75 (2007) 114016 [hep-ph/0612278] [SPIRES].
Y.-G. Xu, R.-M. Wang and Y.-D. Yang, Probe R-parity violating supersymmetry effects in B → K (*) ℓ + ℓ − and B s → ℓ + ℓ − decays, Phys. Rev. D 74 (2006) 114019 [hep-ph/0610338] [SPIRES].
MEGA collaboration, M. Ahmed et al., Search for the lepton-family-number nonconserving decay μ + → e + γ, Phys. Rev. D 65 (2002) 112002 [hep-ex/0111030] [SPIRES].
Belle collaboration, K. Hayasaka et al., New search for τ → μγ and τ → eγ decays at Belle, Phys. Lett. B 666 (2008) 16 [arXiv:0705.0650] [SPIRES].
BABAR collaboration, B. Aubert et al., Search for lepton flavor violation in the decay τ ± → μ ±γ, Phys. Rev. Lett. 95 (2005) 041802 [hep-ex/0502032] [SPIRES].
B. Gripaios, A. Pomarol, F. Riva and J. Serra, Beyond the minimal composite Higgs model, JHEP 04 (2009) 070 [arXiv:0902.1483] [SPIRES].
B. Gripaios, Anomaly holography, the Wess-Zumino-Witten term and electroweak symmetry breaking, Phys. Lett. B 663 (2008) 419 [arXiv:0803.0497] [SPIRES].
D0 collaboration, V.M. Abazov et al., Search for third generation scalar leptoquarks decaying into τb, Phys. Rev. Lett. 101 (2008) 241802 [arXiv:0806.3527] [SPIRES].
D0 collaboration, V.M. Abazov et al., Search for third-generation leptoquarks in \( p\bar p \) collisions at \( \sqrt s = 1.96 - TeV \), Phys. Rev. Lett. 99 (2007) 061801 [arXiv:0705.0812] [SPIRES].
B. Schrempp and F. Schrempp, Light leptoquarks, Phys. Lett. B 153 (1985) 101 [SPIRES].
J. Learned, F. Reines and A. Soni, Limits on nonconservation of Baryon number, Phys. Rev. Lett. 43 (1979) 907 [Erratum ibid. 43 (1979) 1626] [SPIRES].
S.R. Coleman, J. Wess and B. Zumino, Structure of phenomenological Lagrangians. 1, Phys. Rev. 177 (1969) 2239 [SPIRES].
S.R. Coleman and E.J. Weinberg, Radiative corrections as the origin of spontaneous symmetry breaking, Phys. Rev. D 7 (1973) 1888 [SPIRES].
M. Krämer, T. Plehn, M. Spira and P.M. Zerwas, Pair production of scalar leptoquarks at the LHC, Phys. Rev. D 71 (2005) 057503 [hep-ph/0411038] [SPIRES].
V.A. Mitsou, N.C. Benekos, I. Panagoulias and T.D. Papadopoulou, Prospects for scalar leptoquark discovery at the LHC, Czech. J. Phys. 55 (2005) B659 [hep-ph/0411189] [SPIRES].
C.G. Lester and D.J. Summers, Measuring masses of semiinvisibly decaying particles pair produced at hadron colliders, Phys. Lett. B 463 (1999) 99 [hep-ph/9906349] [SPIRES].
A. Barr, C. Lester and P. Stephens, m T2 : The Truth behind the glamour, J. Phys. G 29 (2003) 2343 [hep-ph/0304226] [SPIRES].
A.J. Barr and C. Gwenlan, The race for supersymmetry: using m T2 for discovery, Phys. Rev. D 80 (2009) 074007 [arXiv:0907.2713] [SPIRES].
MEG collaboration, F. Cei, The MEG experiment at PSI, Nucl. Phys. Proc. Suppl. 188 (2009) 309 [SPIRES].
T.E. Browder, T. Gershon, D. Pirjol, A. Soni and J. Zupan, New physics at a super flavor factory, arXiv:0802.3201 [SPIRES].
SuperKEKB Physics Working Group collaboration, A.G. Akeroyd et al., Physics at super B factory, hep-ex/0406071 [SPIRES].
M. Bona et al., SuperB: a high-luminosity asymmetric e +e− super flavor factory. Conceptual design report, arXiv:0709.0451 [SPIRES].
A. Serin and R. Stroynowski, Study of lepton number violating decay tau-mu gamma in ATLAS, ATLAS-PHYS/1997-114 (1997).
R. Santinelli, Study of CMS sensitivity to neutrinoless tau decay at LHC, eConf C 0209101 (2002) WE14 [Nucl. Phys. Proc. Suppl. 123 (2003) 234] [hep-ex/0210033] [SPIRES].
B.L. Roberts, M. Grassi and A. Sato, Intense muon physics working group summary (NuFact05), Nucl. Phys. Proc. Suppl. 155 (2006) 123 [hep-ex/0510055] [SPIRES].
Mu2e collaboration, R.M. Carey et al. Proposal to search for μ − N → e − N with a single event sensitivity below 10 -16, FERMILAB-PROPOSAL-0973 (2008) [SPIRES].
Author information
Authors and Affiliations
Corresponding author
Additional information
ArXiv ePrint: 0910.1789
Rights and permissions
Open Access This is an open access article distributed under the terms of the Creative Commons Attribution Noncommercial License (https://creativecommons.org/licenses/by-nc/2.0), which permits any noncommercial use, distribution, and reproduction in any medium, provided the original author(s) and source are credited.
About this article
Cite this article
Gripaios, B. Composite leptoquarks at the LHC. J. High Energ. Phys. 2010, 45 (2010). https://doi.org/10.1007/JHEP02(2010)045
Received:
Revised:
Accepted:
Published:
DOI: https://doi.org/10.1007/JHEP02(2010)045