Then, the parton shower that preceded the hard interaction is subsequently reconstructed, evolving partons from the hard interaction scale Q backward in time towards smaller Q where the PDF f is evaluated. The color coherence in initial state radiation is slightly more complicated but still follows the same angular ordering. Interference between initial state and final state radiation is implemented in herwig but not in pythia . The independent variable, t , which is how the evolution of α$_{s}$ ( t ) is parametrized, is not unique. In the pythia showering algorithm, the squared mass m 2 of the branching parton is used as the evolution variable. herwig uses t = m $^{2}$/ (2 z (1 − z )) where z = E$_{b}$/E$_{a}$ is ratio of daughter parton energy ( E$_{b}$ ) to the parent parton energy ( E$_{a}$ ). In recent versions of pythia , the option of t = p$_{T}$ of the branching parton is also available as the evolution variable. Occasionally, the radiated parton is at a sufficiently large angle to the parent parton and carries enough energy that it leads to an identifiable jet. Because these jets are typically of lower p$_{T}$ , it does not dominate the event kinematics. However, this lower p$_{T}$ radiation becomes important in studies of jet multiplicity. This part of ISR/FSR can be considered as a part of the hard scatter ̂ σ$_{ij}$ or treated independently. For instance, we see in Figure 1 two boxes surrounding the hard scatter. The dashed box surrounds the leading order scatter, while the dotted box surrounds a next-to-leading order diagram. At NLO pQCD, one parton emitted from either incoming or outgoing parton is part of the short distance hard cross section ̂ σ$_{ij}$ . In LO event generators, these parton emissions are treated quasi-independently of the hard scatter and are part of leading-log showering process. The partons from the incoming hadrons which do not participate in the hardest scatter in an event also interact, but these interactions are normally soft. The particles produced in these multi-parton interactions are, on average, isotropically distributed in the allowed y − φ [19] space and can overlap with the jets produced in the hard interactions. Being soft, multi-parton interactions are in the non-perturbative regime and thus are implemented in event generators using phenomenological models. The parameters of these multi-parton interaction models have been tuned to reproduce the transverse energy and multiplicity distributions of the particles observed far away from the hard jets in collider data [20, 21]. The beam remnants, the partons which do not participate either in hard or multi- parton interactions, go along the beam direction. However, they do carry color and to become color-singlets, they must exchange (soft) partons with the rest of the event. The particles produced in multi-parton interactions and from the hadronization of beam remnants 7