The first study of quasi-free Compton scattering on the neutron in the energy range of Eγ = 0.75 − 1.5 GeV is presented. The data reveals a narrow peak at W ∼ 1.685 GeV. This result, being considered in conjunction with the recent evidence for a narrow structure at W ∼ 1.68 GeV in the η photoproduction on the neutron, suggests the existence of a new nucleon resonance with unusual properties: the mass M ∼ 1.685 GeV, the narrow width Γ ≤ 30 MeV, and the much stronger photoexcitation on the neutron than on the proton. PACS numbers:Many properties of known baryons were transparently explained by the constituent quark model(CQM) [1] that treats baryons as bound system of three valence quarks in the ground or excited state. Some baryon properties remain a mystery: almost half of the CQM-predicted nucleon and ∆ resonances [2] still escape the reliable experimental identification [3] (so-called "missing resonances").The chiral quark soliton model (χQSM) is an alternative view of baryons which are treated as space/flavor rotational excitations of a classical object -a chiral mean-field. χQSM predicts the lowest-mass multiplets of baryons to be the 1/2 + octet and 3/2 + decuplet -exactly as CQM does. The χQSM predictions for higher multiplets are different from CQM [4].Thus, the experimental study of baryon resonances provides benchmark information for the development of theoretical models and for finding relations between them.

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The novel CLAS12 Detector is being currently developed for the CEBAF upgrade to 12 GeV. One its component will be the Central Time-of-Flight system (CTOF). The CTOF will provide the detection and the identification of charged particles emitted at the central angles from 40 • to 130 • . The design goal is to achieve the time-of-flight resolution σ T OF = 50 ps.This study examined the CTOF prototype counter. The counter was made of Bicron-408 scintillation bar viewed by magnetic-resistant fine-mesh HP R7761-70 and R5924-70 photomultiplier tubes through 600 mm and 700 mm long light guides respectively. The measurement was done using 35 MeV protons of MC50 Cyclotron at Korea Institute of Radiological and Medical Sciences. The light transfer efficiencies of the light guides were determined to be 54% and 48%. The proton light output was extrapolated to that of minimum-ionizing particles (MIPs) using the calibration with cosmic-ray muons. The dependence of the time-of-flight resolution on the energy deposited by minimum ionizing particles was derived as σ T OF (L) = 120.7±1.64ps √ L(MeV ). The expected CTOF resolution for MIPs was estimated to be σ T OF ≤ 50 ps.

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