Possible spin-32quarks and scaling violations in neutrino reactions

Abstract

The relevance of possible spin-3/2 fundamental fermions in connection with models of subquark structure is discussed. The Bjorken limit for production of spin-3/2 partons is investigated and the departures from the wellknown spin-112 behavior are examined. The pattern of scaling violation for these processes can be clearly separated from the predictions of quantum chromodynamics.Since the discovery of the T (Ref. 1) and the T (Ref. 2) a remarkable symmetry between quarks and leptons has seemed to emerge. In the standard model3 of unified weak and electromagnetic interactions, to each leptonic family there corresponds a quark family. Even if the experimental evidence for the top quark and the T neutrino i s not completely settled, there are strong theoretica14 arguments that this i s the most feasible model. We a r e then naturally tempted to investigate whether this set of six leptons and six quarks (the latter in three color states each) i s the ultimate set of fundamental fermionic components of matter.The interest in this problem has recently led (see Refs. 5 and 6 for earlier references) to proposals of many models for a more fundamental structure. We are, however, very far from a definite answer, mainly due to the fact that a structure of quarks and leptons would involve phenomena at distances of the order of 10-l6 cm o r smaller, which a r e not experimentally accessible at present.An important step along this direction would be the experimental discovery of a fundamental fermion with spin 2. This might then give indications on whether the currently known families a r e really fundamental o r not; on whether both quarks and leptons a r e fundamental o r if they are on a different level7; on whether the families a r e to be simply repeated or whether we should consider each one a s composed of spin $ and spin 2 fermions.We have previously presented a discussion of these possibilities5 for the leptonic sector and investigated in a phenomenological and model-independent way some of the experimental consequences of such a hypothesis. In this paper we turn our attention to the quark sector.A first possibility is to consider that spin-; .quarks would appear in an independent and sequential family: (u, d),

Higher-spin particles at high-energy colliders

“…In high-energy particle physics, both spin-3/2 leptons [54][55][56][57][58][59][60][61][62][63] and spin-3/2 quarks [64][65][66][67][68] have been considered in the past. For instance, the production of spin-3/2 particles at hadron colliders has been discussed in refs.…”

Excited Muon Searches at the FCC-Based Muon-Hadron Colliders

“…Excited leptons with spin-1/2 and weak-isospin-1/2 are considered as the lowest radial and orbital excitations. Excited states with higher spins also appear in composite models [10][11][12][13][14].…”

Production and decay of single heavy spin-3/2 leptons in high energy electron-positron collisions

“…In composite models ordinary spin-1/2 leptons and quarks are thought to be formed by more fundamental fermions. If this hypothesis is correct, then excited spin-3/2 states are expected to exist [1]. Composite fermions in enlarged groups ( relative to the standard group) also imply spin-3/2 fermions [2].…”

“…The phenomenology of spin-3/2 lepton production has been studied for electron-positron collisions [1], hadronic reactions [9] and more recently, for the electron-proton collider HERA [10] and the e − γ mode of the next generation of electron-positron colliders [11]. In this paper we turn our attention to the production and decay of a single spin-3/2 lepton in e + e − collisions at LEP2 and NLC energies.…”

“…These problems make difficult a comparison of theoretical predictions for spin-3/2 objects with any possible "new physics" experimental signal. Some time ago it was pointed out [1] that some of these difficulties could be ameliorated for the coupling of spin-3/2 fermions to massive electroweak gauge bosons. Although this hypothesis is not a solution of the problems concerning spin-3/2 fields, one expects that it will allow that reliable phenomenological estimates be made, in the same spirit of the effective Fermi theory for weak interactions.…”