Robin Devenish and Amanda 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/9780198506713.003.0006
- Subject:
- Physics, Particle Physics / Astrophysics / Cosmology
This chapter discusses how Parton Distribution Functions (parton momentum densities) are extracted from data. It starts with an outline of the general framework based on NLO QCD. Next, the concept of ...
More
This chapter discusses how Parton Distribution Functions (parton momentum densities) are extracted from data. It starts with an outline of the general framework based on NLO QCD. Next, the concept of the global fit is introduced and the choice of reactions and data sets discussed. The following section gives a detailed account of some global fits. Particular attention is paid to the extraction of the gluon distribution since most cross-sections at hadron colliders are dominated by gluon induced processes. Sources of information on PDFs from non-DIS processes are considered. Next, uncertainties arising from the theoretical framework and from the model assumptions are considered. Experimental sources of uncertainty are examined, together with the problems of defining a reasonable measure of the error on a parton density and how to estimate it. The final two sections cover the ‘dynamically generated’ partons of the GRV group and prospects for improving our knowledge of the gluon distribution.Less
This chapter discusses how Parton Distribution Functions (parton momentum densities) are extracted from data. It starts with an outline of the general framework based on NLO QCD. Next, the concept of the global fit is introduced and the choice of reactions and data sets discussed. The following section gives a detailed account of some global fits. Particular attention is paid to the extraction of the gluon distribution since most cross-sections at hadron colliders are dominated by gluon induced processes. Sources of information on PDFs from non-DIS processes are considered. Next, uncertainties arising from the theoretical framework and from the model assumptions are considered. Experimental sources of uncertainty are examined, together with the problems of defining a reasonable measure of the error on a parton density and how to estimate it. The final two sections cover the ‘dynamically generated’ partons of the GRV group and prospects for improving our knowledge of the gluon distribution.
Robin Devenish and Amanda 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/9780198506713.003.0007
- Subject:
- Physics, Particle Physics / Astrophysics / Cosmology
The advantages and disadvantages of various methods of determining the strong coupling αs from DIS data are considered including the use of moments of the measured structure functions and the ...
More
The advantages and disadvantages of various methods of determining the strong coupling αs from DIS data are considered including the use of moments of the measured structure functions and the conventional method in which αs is determined in an NLO QCD fit along with the parton momentum densities. The estimation of experimental and theoretical uncertainties is discussed in detail. Various possible extensions to the theoretical framework are summarised. The remaining sections consider jet production at HERA. The importance of using the Breit frame is covered and a brief outline given of the QCD calculation of the dijet cross-section. Jet measures, including the cone and k_T algorithms, which provide the link between the final state hadrons and the underlying partonic structure, are outlined. It is shown that NLO QCD gives a good description of dijet data. Then measurement of αs and the running of αs from jet production rates at large Q2 are discussed.Less
The advantages and disadvantages of various methods of determining the strong coupling αs from DIS data are considered including the use of moments of the measured structure functions and the conventional method in which αs is determined in an NLO QCD fit along with the parton momentum densities. The estimation of experimental and theoretical uncertainties is discussed in detail. Various possible extensions to the theoretical framework are summarised. The remaining sections consider jet production at HERA. The importance of using the Breit frame is covered and a brief outline given of the QCD calculation of the dijet cross-section. Jet measures, including the cone and k_T algorithms, which provide the link between the final state hadrons and the underlying partonic structure, are outlined. It is shown that NLO QCD gives a good description of dijet data. Then measurement of αs and the running of αs from jet production rates at large Q2 are discussed.
