Sensitivity of NEXT-100 to neutrinoless double beta decay

NEXT-100 is an electroluminescent high-pressure xenon gas time projection chamber that will search for the neutrinoless double beta ($\beta \beta 0\nu$) decay of Xe-136. The detector possesses two features of great value for $\beta \beta 0 \nu$searches:energyresolutionbetterthan1\mathrm{\%}FWHMatthe$Q$ value of Xe-136 and track reconstruction for the discrimination of signal and background events. This combination results in excellent sensitivity, as discussed in this paper. Material-screening measurements and a detailed Monte Carlo detector simulation predict a background rate for NEXT-100 of at most $4\times {10}^{-4}$ counts keV${}^{-1}$ kg${}^{-1}$ yr${}^{-1}$. Accordingly, the detector will reach a sensitivity to the \bbonu-decay half-life of $2.8\times {10}^{25}$ years (90% CL) for an exposure of 100 $\mathrm{k}\mathrm{g}\cdot \mathrm{y}\mathrm{e}\mathrm{a}\mathrm{r}$, or $6.0\times {10}^{25}$ years after a run of 3 effective years.