Underlying event

In particle physics, underlying event (UE) refers to the additional interactions of two particle beams at a collision point beyond the main collision under study. Specifically, the term is used for hadron collider events which do not originate from the primary hard scattering (high energy, high momentum impact) process.[1] The term was first defined in 2002.[2][3]

Further explanation

Underlying events can be thought of as the remnants of scattering interactions.[4][5] The UE may involve contributions from both "hard" and "soft" processes (here “soft” refers to interactions with low p-T, i.e. transverse momentum, transfer[6]).

These are important both in the simulation of particle experiments (often using event generators); and interpretation and analysis of data so as to filter out the desired signals.[7]

Features

Contents of UE include initial and final state radiation, beam-beam remnants, multiple parton interactions, pile-up, noise.[5]

See also

References

  1. ^ "Underlying Event – a definitive study by CDF - Collider Blog". Collider Blog.
  2. ^ Barnaföldi, Gergely Gábor; Agócs, András G.; Lévai, Péter (2011). Underlying Event Studies for LHC Energies. Vol. 1348. AIP. p. 124. arXiv:1101.4155v1. doi:10.1063/1.3579440.
  3. ^ Affolder, T.; Akimoto, H.; Akopian, A.; Albrow, M. G.; Amaral, P.; et al. (CDF Collaboration) (2002-04-22). "Charged jet evolution and the underlying event in proton-antiproton collisions at 1.8 TeV". Physical Review D. 65 (9). American Physical Society (APS): 092002. doi:10.1103/physrevd.65.092002. hdl:1969.1/181493. ISSN 0556-2821.
  4. ^ Lecture 10: QCD at Colliders, page 20. Particle Physics, Dr Victoria Martin, Spring Semester 2013.
  5. ^ a b Mazumdar, Kajari. "Underlying events in p-p collisions at LHC" (PDF). tifr.res.in. Retrieved 23 March 2022.
  6. ^ Aad, G.; Abbott, B.; Abdallah, J.; Abdelalim, A. A.; Abdesselam, A.; et al. (The ATLAS Collaboration) (2011-05-31). "Measurement of underlying event characteristics using charged particles inppcollisions at GeV and 7 TeV with the ATLAS detector". Physical Review D. 83 (11): 112001. arXiv:1012.0791v2. doi:10.1103/physrevd.83.112001. ISSN 1550-7998.
  7. ^ Butterworth, Jon (2006). "Underlying Events" (PDF). ucl.ac.uk. London. Wilhelm and Else Heraeus-Seminar on “New Event Generators for Particle Physics Experiments”