Dijet measurements in pPb collisions

Results on dijet production in pPb collisions at 5.02 TeV are discussed with a focus on dijet pseudorapidity, ηdijetηdijet, and centrality classification biases on it. The normalized ηdijetηdijet distributions from data and from calculations with CT10 proton parton distribution function (pPDF) and with EPS09 nuclear parton distribution function (nPDF) are compared. Despite the agreement between data and theoretical calculations for an inclusive centrality selection, as the raw transverse energy deposited in the forward calorimeter (forward activity) increases, ηdijetηdijet distribution shifts towards lead beam direction an amount that is larger than what would be expected from the impact parameter dependence of nPDFs. To understand the driving mechanism of this shift an additional measurement of 〈ηdijet〉〈ηdijet〉 as a function of forward activity in the lead direction is carried out in differential bins of forward activity in the proton direction. The shift is reduced by keeping forward activity in the proton direction in a narrow interval.