pi0-h+/- Jet Correlations in d + Au Collisions at √ sNN = 200 GeV

Various quark gluon plasma signatures have been experimentally established in Au+Au and Pb+Pb collisions at RHIC and LHC, such as elliptical flow and jet quenching. For decades, the quark gluon plasma was believed not to be created in p+A collisions. However, recent experimental discoveries of collective flow in p+Pb and d+Au collisions indicate a hot nuclear medium and a thermal equilibrium in such small systems. An energy loss analysis would be a good alternative measurement for such pictures.;Di-hadron correlation measurements are widely used in jet analysis. In this study, pi0-h+/- azimuthal correlations and the per trigger yields in d+Au collisions at √sNN = 200 GeV are measured and compared with p+p collisions at the same energy. In order to cancel out part of the systematic uncertainties and measure the subtle jet modifications, a new quantity RI is proposed and measured from data. In central d+Au collisions, RI shows a clear suppression in large zT regions and a delicate enhancement of about 2sigma in low z T regions. Such jet modifications are qualitatively similar, but in a much smaller scale, to the ones observed in central Au+Au collisions, which are attributed to the jet quenching and energy loss in a quark gluon plasma created in central Au+Au collisions.;No theory is available to explain this new experimental phenomenon. To constrain the cold nuclear matter effects, we perform a series of simulations to investigate the possible physics origin of these modifications. Various kT setting in Pythia and Hijing simulations are not able to reproduce the features observed in data. Also, the gluon jet mixing and nuclear modification of the parton distribution functions are studied. None of them are sufficient to explain the RI modification observed in central d+Au collisions.;No significant away-side IdA modifications is observed in peripheral d+Au collisions. This result suggests that previous unexpected RdA enhancement in peripheral d+Au collisions from pi0 and jet reconstruction analysis might come from an issue with the determination of N coll scale factor instead of a real enhancement in physics data.;Regardless of the theoretical origin, the data provide constraints that should be able to set concrete limits on the contributions of various cold nuclear or possibly hot QGP-like effects.