Photoproduction of Scalar Mesons, and Upgrade of the CLAS Electromagnetic Calorimeter at Jefferson Lab
Shloka Chandavar Jefferson Laboratory
Host: Sheldon Stone
The standard quark model makes no allowance for the existence of gluons outside hadrons; however lattice QCD calculations predict bound states of two or more gluons, called glueballs. According to lattice calculations, the lightest of these experimentally unverified particles is expected to have mass in the range of 1−1.8 GeV and JPC = 0++. Themixing of glueball states with neighbouring meson states complicates their identification. The f0(1500) is one of several candidates for the lightest glueball, whose presence in the K0 sK0 s channel was investigated in photoproduction using the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab. This was done by studying the reaction, γp → fJp → K0 sK0 s p → 2(π+π−)p using data from the g12 experiment. A moments analysis was performed on this data to characterize the spin properties of the resonance observed at 1.5 GeV. Results from the analysis of this data will be presented.
The g12 experiment ran with the CLAS6 detector, so named because of its capability to work with a maximum electron beam energy of 6 GeV. Jefferson Lab has since upgraded its facility to produce electron beam with double that energy. The higher beam energy means that the energy of electrons and photons impinging on the detector will be too high to be contained by the existing CLAS6 electromagnetic calorimeter (EC). Several of the experiments commissioned to be performed using CLAS12 require the accurate detection of neutral pions via their decay into two photons. At the energies of CLAS12, the calorimeter needs to have a very good position resolution in order to be able to detect these two photons and to avoid their labeling as a single photon. It was thus necessary to update the detector sub-system in order to improve its functionality at higher energies. To do this, another calorimeter, the preshower calorimeter (PCAL) is to be placed in front of the EC, the testing and construction of which will be discussed.