Effects of N^(*)(1440) resonance on subthreshold kaon, antikaon and antiproton production

We study the effects of $N^{*}(1440)$ resonance on the production of kaons, antikaons and antiprotons in heavy-ion collisions at subthreshold energies. Using free-space widths for the $\Delta(1232)$ and the $N^{*}(1440)$ resonance and free-space thresholds for particle production, it is found that the $N^{*}$-baryon interactions contribute about 10\%, 25\% and 80\% to the yield of kaon, antikaon and antiproton, respectively. Doubling the widths of resonances due to possible medium effects, both the total and the $N^{*}$ induced antiproton yield decrease by about a factor of 3. Using a reduced antiproton production threshold in a nuclear medium as a result of dropping in-medium nucleon and antiproton masses, the total and the $N^{*}$ induced antiproton yield increase by a factor of 35 and 27, respectively, and the contribution of the $N^{*}$ induced collisions is reduced to about 50\% of the total.