The ALICE collaboration have released two papers based on measurements from a single day of data-taking in September when the Large Hadron Collider (LHC) collided protons with lead ions for the first time.
The first paper presents measurements of the charged hadron density produced in proton-ion collisions and compares the result with the same measurement performed in proton-proton and ion-ion collisions. The second compares the transverse momentum distributions of charged hadrons measured in proton-ions and proton-proton collisions.
The short run in September gave the experiments a first taste of proton-nucleus collisions before the main run in January to February 2013, the last LHC physics before the accelerator is shut down for maintenance. This will give the experiments vital data to benchmark the lead-lead collision data taken in 2010 and 2011 and also open up exploration of new physics topics.
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