Leptoquark

Leptoquarks are hypothetical particles that would interact with quarks and leptons. They are bosons and carry lepton numbers (number representing the difference between the number of leptons and the number of antileptons in an elementary particle reaction) and baryon numbers (Baryons (three quarks) have a baryon number of +1, mesons (one quark, one antiquark) have a baryon number of 0, and antibaryons (three antiquarks) have a baryon number of −1. ).  The other quantum numbers for the Leptoquarks, like spin, fractional electric charge, and weak isospin vary among theories. 

Leptoquarks are found in various extensions to the Standard Model, such as Technicolor theories, theories of Quark-lepton unification (like the Pati-Salam model), or GUTs based on SU(5), SO(10) and  E6. 

Leptoquarks are currently being looked for in experiments ATLAS and CMSS at the LHC in CERN. 

If they exist, leptoquarks are to be heavier than all currently known elementary particles. This is otherwise, they would have already been discovered.  By definition, leptoquarks would decay directly into a quark and a lepton or antilepton.  Like most other elementary particles, they live for a very short time and not present in ordinary matter. However, it is a potential that they are produced in high energy particle collisions such as in particle colliders or from cosmic rays hitting the Earth's atmosphere.