pegasus:overview
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====== Overview ====== | ====== Overview ====== | ||
- | Here we give a some information and explanations about the important features of PEGASUS. | + | Here we give some information and explanations about the important features of PEGASUS. |
===== Physical problem and solution ===== | ===== Physical problem and solution ===== | ||
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However, theoretical description of a number of high energy processes proceeding with large momentum | However, theoretical description of a number of high energy processes proceeding with large momentum | ||
transfer and containing multiple hard scales needs for transverse momentum dependent (TMD) parton (quark | transfer and containing multiple hard scales needs for transverse momentum dependent (TMD) parton (quark | ||
- | or gluon) distributions in a proton. These quantities encode the nonperturbative information on proton | + | or gluon) distributions in a proton |
Balitsky-Fadin-Kuraev-Lipatov (BFKL) or Catani-Ciafaloni-Fiorani-Marchesini (CCFM) evolution equations. | Balitsky-Fadin-Kuraev-Lipatov (BFKL) or Catani-Ciafaloni-Fiorani-Marchesini (CCFM) evolution equations. | ||
The hadron-level Monte-Carlo event generator [[https:// | The hadron-level Monte-Carlo event generator [[https:// | ||
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PEGASUS is a newly developed parton-level Monte-Carlo event generator | PEGASUS is a newly developed parton-level Monte-Carlo event generator | ||
designed to calculate cross sections for a wide range of hard QCD processes, | designed to calculate cross sections for a wide range of hard QCD processes, | ||
- | which incorporates the TMD gluon dynamics in a proton. | + | which incorporates the TMD gluon dynamics in a proton |
It provides all necessary components, including | It provides all necessary components, including | ||
off-shell (dependent on the transverse momenta) production | off-shell (dependent on the transverse momenta) production | ||
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The calculations using PEGASUS include a few general steps common for all of the processes. | The calculations using PEGASUS include a few general steps common for all of the processes. | ||
- | When PEGASUS is running, one can select the colliding particles, proton-proton, | + | When PEGASUS is running, one can select the colliding particles, proton-proton, |
- | and set their center-of-mass energy. The default setting corresponds to the LHC Run II setup. | + | and set beam energies. The default setting corresponds to the LHC Run II setup. |
Then one can select factorization scheme (TMD or collinear one) for each of the colliding particles, choose corresponding parton density function and set the parameters, important | Then one can select factorization scheme (TMD or collinear one) for each of the colliding particles, choose corresponding parton density function and set the parameters, important | ||
for further Monte-Carlo simulation, namely, number of iterations and number of simulated events per iteration. | for further Monte-Carlo simulation, namely, number of iterations and number of simulated events per iteration. | ||
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* If there are several contributing subprocesses, | * If there are several contributing subprocesses, | ||
- | The generated events can be accumulated in Les Houches Event ('' | + | The generated events can be accumulated in a Les Houches Event ('' |
===== Implemented TMD gluon densities in a proton ===== | ===== Implemented TMD gluon densities in a proton ===== | ||
^ Set ^ Order of a< | ^ Set ^ Order of a< | ||
- | | LLM' | + | | LLM (CCFM) |
| A0 (CCFM) | | A0 (CCFM) | ||
| B0 (CCFM) | | B0 (CCFM) | ||
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| JH' | | JH' | ||
| KLSZ' | | KLSZ' | ||
- | | PB NLO set 1 | 2 | 4 | 118 | [[https:// | + | | PB NLO set 1 | 2 | 4 | 118 | [[https:// |
- | | PB NLO set 2 | 2 | 4 | 118 | [[https:// | + | | PB NLO set 2 | 2 | 4 | 118 | [[https:// |
The A0+, A0-, B0+, B0-, JH' | The A0+, A0-, B0+, B0-, JH' | ||
to estimate the scale uncertainties of the CCFM-based calculations, | to estimate the scale uncertainties of the CCFM-based calculations, | ||
- | + | In principle, any other TMD gluon density in a proton could be used: | |
- | Additionally, any other TMD gluon density in a proton could be used: | + | one just have to upload it from the separate data file prepared in the standard |
- | one just have to upload it from the separate data file (prepared in the standard | + | |
===== Strong coupling and masses of particles ===== | ===== Strong coupling and masses of particles ===== | ||
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with respect to the number of active flavors and QCD scale. | with respect to the number of active flavors and QCD scale. | ||
This choice is done automatically with the choice of the TMD and/or conventional | This choice is done automatically with the choice of the TMD and/or conventional | ||
- | parton densities | + | parton densities. There is no possibility to change it manually since this setup is essential for determination of corresponding parton distributions. |
The masses of all particles (quarks, gauge bosons, heavy quarkonia etc), | The masses of all particles (quarks, gauge bosons, heavy quarkonia etc), | ||
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* Polarization information is not preserved. | * Polarization information is not preserved. | ||
* A parton carries a tag according to the standard [[http:// | * A parton carries a tag according to the standard [[http:// | ||
- | * Conventional (collinear) parton densities in a proton are numbered according to the [[https:// | + | * Conventional (collinear) parton densities in a proton |
The produced '' | The produced '' | ||
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We are also grateful to Maria Mikova, Natalia Ovechkina and Anastasia Zotova for their support and help for the design of the program. | We are also grateful to Maria Mikova, Natalia Ovechkina and Anastasia Zotova for their support and help for the design of the program. | ||
- | Contributions to the physics in PEGASUS were provided by Anatoly Kotikov (JINR, Dubna) | + | Contributions to the physics in PEGASUS were provided by Anatoly Kotikov (JINR, Dubna), |
- | Nizami Abdulov | + | Gennady Lykasov |
- | and Andrey Prokhorov | + | |
We are especially grateful to Nikolai Zotov, who guided and supervised our first steps in High Energy Physics, | We are especially grateful to Nikolai Zotov, who guided and supervised our first steps in High Energy Physics, | ||
who encouraged our progress in k< | who encouraged our progress in k< | ||
pegasus/overview.1693651163.txt.gz · Last modified: 02/09/2023 13:39 by lipatov