John Campbell, Joey Huston, and Frank Krauss
- Published in print:
- 2017
- Published Online:
- March 2018
- ISBN:
- 9780199652747
- eISBN:
- 9780191749148
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/oso/9780199652747.003.0005
- Subject:
- Physics, Particle Physics / Astrophysics / Cosmology
This chapter centres around the treatment of QCD emissions to all orders. After introductory remarks about the analytic properties of the radiation pattern, some of the most striking phenomenological ...
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This chapter centres around the treatment of QCD emissions to all orders. After introductory remarks about the analytic properties of the radiation pattern, some of the most striking phenomenological consequences of non-trivial quantum effects, in particular, the angular ordering property of QCD, are highlighted. Next, analytic resummation techniques are considered, expanding on the treatment of transverse momentum resummation from Chapter 2, and introducing the idea of threshold resummation. BFKL resummation, which resums large logarithms emerging in the high-energy limit, is also introduced. In the second part of this chapter, the probabilistic simulation of QCD radiation through the parton shower is discussed. After a detailed introduction to different schemes and algorithms, the discussion of the combination of the parton shower with fixed-order matrix elements beyond the Born approximation is considered, with a discussion of matching with NLO calculations and the merging with multijet matrix elements.Less
This chapter centres around the treatment of QCD emissions to all orders. After introductory remarks about the analytic properties of the radiation pattern, some of the most striking phenomenological consequences of non-trivial quantum effects, in particular, the angular ordering property of QCD, are highlighted. Next, analytic resummation techniques are considered, expanding on the treatment of transverse momentum resummation from Chapter 2, and introducing the idea of threshold resummation. BFKL resummation, which resums large logarithms emerging in the high-energy limit, is also introduced. In the second part of this chapter, the probabilistic simulation of QCD radiation through the parton shower is discussed. After a detailed introduction to different schemes and algorithms, the discussion of the combination of the parton shower with fixed-order matrix elements beyond the Born approximation is considered, with a discussion of matching with NLO calculations and the merging with multijet matrix elements.
Robin Devenish and Amand Cooper-Sarkar
- Published in print:
- 2003
- Published Online:
- January 2010
- ISBN:
- 9780198506713
- eISBN:
- 9780191709562
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780198506713.003.0009
- Subject:
- Physics, Particle Physics / Astrophysics / Cosmology
This chapter is concerned with physics at low values of Bjorken x, below 0.01, where the q-qbar sea and gluon are the dominant partons and increasing rapidly as x decreases. It starts with an ...
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This chapter is concerned with physics at low values of Bjorken x, below 0.01, where the q-qbar sea and gluon are the dominant partons and increasing rapidly as x decreases. It starts with an overview of the approaches considered and their regions of validity in the ln(1/x)-ln(Q2 ) plane. Then follows an account of the ‘standard’ approaches: DGLAP equations at low x and the Regge approach to total cross-sections. The hard and soft Pomerons are introduced and explained, followed by the BFKL equation. Angular ordering of gluon radiation and the CCFM approach to DIS comes next. These aforementioned approaches are linear and lead to an undamped increasing structure function as x decreases, which will violate unitarity eventually. This problem and how non-linear effects ameliorate it are covered next. The last section gives a comparison of the low-x approaches with structure-function data and outlines the need for precision measurements of other observables.Less
This chapter is concerned with physics at low values of Bjorken x, below 0.01, where the q-qbar sea and gluon are the dominant partons and increasing rapidly as x decreases. It starts with an overview of the approaches considered and their regions of validity in the ln(1/x)-ln(Q2 ) plane. Then follows an account of the ‘standard’ approaches: DGLAP equations at low x and the Regge approach to total cross-sections. The hard and soft Pomerons are introduced and explained, followed by the BFKL equation. Angular ordering of gluon radiation and the CCFM approach to DIS comes next. These aforementioned approaches are linear and lead to an undamped increasing structure function as x decreases, which will violate unitarity eventually. This problem and how non-linear effects ameliorate it are covered next. The last section gives a comparison of the low-x approaches with structure-function data and outlines the need for precision measurements of other observables.
