Particles with large transverse momentum (p_T) produced during the initial phase of a nuclear collision can be used to probe the dense excited matter created during the collision process. The p_T spectra of neutral pions and charged hadrons in Au+Au and d+{Au} collisions GeV are compared to p+p spectra at the same \sqrt {s_NN}. In central Au+Au collisions a factor of 4-5 suppression of high p_T neutral pion and charged hadron yields is observed compared to expectations from scaled p+p results. No suppression of high p_T particles is observed in d+{Au} collisions, suggesting that the observed suppression in central Au+Au collisions is due to the produced dense matter.

PACS numbers: 25.75.--q