Жоғары энергиялы адрон-адрон шашырауындағы Дрелл-Ян процесі

Process in high energy hadron–hadron scattering

The Drell–Yan process occurs in high energy hadron–hadron scattering. It takes place when a quark of one hadron and an antiquark of another hadron annihilate, creating a virtual photon or Z boson which then decays into a pair of oppositely charged leptons. Importantly, the energy of the colliding quark antiquark pair can be almost entirely transformed into the mass of new particles. This process was first suggested by Sidney Drell and Tung Mow Yan in 1970 to describe the production of lepton–antilepton pairs in high energy hadron collisions. Experimentally, this process was first observed by J. H. Christenson et al. in proton–uranium collisions at the Alternating Gradient Synchrotron.

The Drell–Yan process is studied both in fixed target and collider experiments. It provides valuable information about the parton distribution functions (PDFs) which describe the way the momentum of an incoming high energy nucleon is partitioned among its constituent partons. These PDFs are basic ingredients for calculating essentially all processes at hadron colliders. Although PDFs should be derivable in principle, current ignorance of some aspects of the strong force prevents this. Instead, the forms of the PDFs are deduced from experimental data.

PDFs are determined using the world data from deep inelastic scattering, Drell–Yan process, etc. The Drell–Yan process is closely related to the deep inelastic scattering; the Feynman diagram of the Drell–Yan process is obtained if the Feynman diagram of deep inelastic scattering is rotated by 90°. A time like virtual photon or Z boson is produced in s channel in the Drell–Yan process while a space like virtual photon or Z boson is produced in t channel in the deep inelastic scattering.