Nuclear reactions of 19,20C on a liquid hydrogen target measured with the superconducting TOF spectrometer

Reaction cross sections with various kinds of breakup channels for neutron-rich carbon isotopes 18–20C and for 9Be impinging on a liquid hydrogen target were investigated at 40 MeV/nucleon. The nuclides of interest were produced via projectile fragmentation from a 63 MeV/nucleon 40Ar beam and were separated in flight at the RIKEN projectile fragment separator (RIPS). The combination of the large-acceptance superconducting TOF spectrometer, TOMBEE (TOF Mass analyzer for exotic BEam Experiment), with a liquid hydrogen target, CRYPTA (CRYogenic ProTon and Alpha target system), enables simultaneous measurements of several reaction channels: the reaction cross sections (image), individual elemental fragmentation cross sections (image), charge-changing cross sections (image), neutron-removal cross sections (image), and charge-pickup cross sections (image) for 19,20C; image, image, and image for 18C; and image for 9Be. The present image of 9Be on proton, image, measured in the inverse kinematics, was consistent with the previous measurements using proton beams at different laboratories. The image of 19C and 20C on proton were determined to be image and image, respectively. Taking into account the beam energy and target dependence of image, the present image are found to be considerably enhanced compared with those measured at around 1 GeV/nucleon. The image appears to increase with the mass number of the projectiles, and it significantly contributes to image in the present energy range. The finite-range optical-limit and few-body Glauber model analyses were performed for image to study the nuclear matter density distributions and to derive the relative strength of the s-wave components of the valence neutrons in 19C and 20C. A neutron halo structure of 19C is confirmed with an s-wave dominance of the valence neutron when the effect of the charge-pickup reaction is taken into account. The large image of 19C and image of 20C also support the decoupled structures of 18C +n and 18Cimage, respectively. The image of 19C and 20C agree with each other within their experimental uncertainties, which might indicate a similar proton density distribution in 19C and 20C. The image decreases monotonically without the even–odd effect as the number of removed protons increases.