Abstract
An experimental program has been approved at the Thomas Jefferson National Accelerator Facility to measure the (ep,e’K+)Y reactions using the CLAS12 setup in Hall B. Data have been obtained using a 7.5 GeV electron beam, impinging upon a liquid hydrogen target in the CLAS12 center. Scattered electrons have been detected in an angle range of 2.5° to 4.5° by the Forward Tagger (FT) and at angles greater than 5° in the CLAS12 Forward Detector, allowing to measure the KY electroproduction differential cross section and to probe the Q2 evolution of the N* resonances electrocouplings in the Q2 range from 0.05 GeV2 to 3 GeV2. The study of the Q2 dependence of the electrocouplings will provide a crucial tool to investigate the possible hybrid nature of the N* resonances. Preliminary results from CLAS12 data are compared with simulated data using a realistic Gent Regge plus resonance event generator
Highlights
Besides regular mesons and baryons a number of "exotic" hadrons have been conjectured, states having more valence quarks than the three quark configuration for baryons or the quark-antiquark one for mesons, namely tetraquarks and pentaquarks, or states having valence gluons in their structure, hybrid mesons and hybrid baryons
Hybrid baryons are hypothetical three quark states with gluonic degrees of freedom. Their existence is allowed by Quantum Chromo Dynamics (QCD), and Lattice QCD (LQCD) calculations predict the existence of several hybrid states 1.3 GeV above the nucleon ground state [1]
The ongoing program at the Thomas Jefferson National Accelerator Facility (Jefferson Laboratory) in Newport News (VA) employs photoproduction and electroproduction reactions to study the excitation of nucleons in the nucleon resonance mass range up to 3 GeV and proved to be successful; a program concerning the search for hybrid baryons is in progress
Summary
Besides regular mesons and baryons a number of "exotic" hadrons have been conjectured, states having more valence quarks than the three quark configuration for baryons or the quark-antiquark one for mesons, namely tetraquarks and pentaquarks, or states having valence gluons in their structure, hybrid mesons and hybrid baryons. Hybrid baryons are hypothetical three quark states with gluonic degrees of freedom. A useful approach has been recently employed in the study of the Roper resonance N(1440)1/2+, that has been considered as a candidate for the lowest mass hybrid baryon [2]. To dismiss this possibility [3] [4] [5], meson electroproduction data were exploited, studying the photon virtuality (Q2) evolution of the electrocouplings, that should present a different low Q2 behavior for hybrids with respect to regular states. The task is to perform an extensive study of K+Λ, K+Σ and pπ+π− electroproduction reactions, in the kinematic region that covers the mass range up to 3 GeV and in the Q2 range
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