Difference between revisions of "Hard"
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Hard is an adjective often used to describe the energy and or momentum of (an object involved in) a scattering process in collider physics. The energy is usually large enough that in calculations of such processes a perturbative expansion in the [[coupling]] strength may be employed. This distinguishes such a process or object from something which is [[soft]], or has low energy and or momentum. | Hard is an adjective often used to describe the energy and or momentum of (an object involved in) a scattering process in collider physics. The energy is usually large enough that in calculations of such processes a perturbative expansion in the [[coupling]] strength may be employed. This distinguishes such a process or object from something which is [[soft]], or has low energy and or momentum. | ||
For example, in a [[general-purpose event generator]] the hard event is usually calculated at [[fixed order]] using a [[matrix-element generator]] and evolved to lower energies (typically the [[hadronisation]] scale <math>\Lambda_{QCD}</math>) using a [[parton shower]]. | For example, in a [[general-purpose event generator]] the hard event is usually calculated at [[fixed order]] using a [[matrix-element generator]] and evolved to lower energies (typically the [[hadronisation]] scale <math>\Lambda_{QCD}</math>) using a [[parton shower]]. | ||
Latest revision as of 15:47, 1 August 2017
Hard is an adjective often used to describe the energy and or momentum of (an object involved in) a scattering process in collider physics. The energy is usually large enough that in calculations of such processes a perturbative expansion in the coupling strength may be employed. This distinguishes such a process or object from something which is soft, or has low energy and or momentum.
For example, in a general-purpose event generator the hard event is usually calculated at fixed order using a matrix-element generator and evolved to lower energies (typically the hadronisation scale 
) using a parton shower.
