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The Cognitive Radio (CR) is a recent technology that aims at increasing the spectrum utilization under the current static spectrum management. With appropriate CR MAC protocols, the unlicensed users, also called secondary users (SUs), are able to access the unused portion of spectrum in an opportunistic way. These protocols should also provide a coordinated access between the SUs and protect the licensed users (or primary users, PUs) from the induced interference. In this paper, we propose a novel multi-channel cognitive MAC protocol based on a cooperative spectrum access among the SUs, which enhances the throughput of the cognitive radio network (CRN) subject to a SU transmit power constraint. Our proposed protocol introduces a new reactive sensing period and a novel recovery scheme to instantly detect the presence of a PU, and proposes an adaptive handoff to preserve the continuity of the SU transmission. The results of simulation show the effectiveness of our protocol. The aggregate throughput of the SUs is improved and the handoff delay is considerably reduced.