pegasus:overview
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pegasus:overview [09/12/2019 19:15] – lipatov | pegasus:overview [15/04/2024 10:12] – lipatov | ||
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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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The multi-purpose Monte-Carlo event generators are commonly used tools for | The multi-purpose Monte-Carlo event generators are commonly used tools for | ||
theoretical description of the collider measurements. | theoretical description of the collider measurements. | ||
- | Most of them (for example, [[http:// | + | Most of them (for example, [[http:// |
+ | [[https:// | ||
or collinear QCD factorization, | or collinear QCD factorization, | ||
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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extremely user friendly interface, which allows one | extremely user friendly interface, which allows one | ||
to easily implement various kinematical cuts into the calculations. | to easily implement various kinematical cuts into the calculations. | ||
- | Generated events (weighted or unweighted) can be stored in the | + | Generated events (weighted or unweighted) can be stored in the [[https:// |
- | Les Houches Event file or presented "on the fly" with convenient | + | |
built-in tool [[pegasus: | built-in tool [[pegasus: | ||
+ | |||
+ | The underlying physics in [[https:// | ||
+ | [[https:// | ||
+ | basically the same. However, PEGASUS simplifies setting | ||
+ | the parameters and kinematic constraints (through the menu, with | ||
+ | no programming); | ||
+ | it provides a choice between weighted and unweighted events; | ||
+ | and it operates with a graphics interface, which is detached in the | ||
+ | console version (if a long-time calculation is needed). These features | ||
+ | make PEGASUS more flexible and better adjustable to the user's needs. | ||
===== Calculation steps ===== | ===== Calculation steps ===== | ||
- | The calcualtions | + | The calculations |
- | When PEGASUS is running, one can select the colliding particles, proton-proton | + | When PEGASUS is running, one can select the colliding particles, proton-proton, proton-antiproton, proton-nucleus or electron-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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* From the list of available processes one can select the necessary process and then (optionally) correct the default kinematical restrictions, | * From the list of available processes one can select the necessary process and then (optionally) correct the default kinematical restrictions, | ||
- | * For each of the observables one can manually edit the default binning according to own wishes. As another option, the binning can be uploaded immediately from the data file. Several commonly used formats (such as '' | + | * For each of the observables one can manually edit the default binning according to own wishes. As another option, the binning can be uploaded immediately from the data file. Several commonly used formats (such as '' |
* The user-defined setup for any process (total center-of-mass energy, selected parton densities, kinematical restrictions, | * The user-defined setup for any process (total center-of-mass energy, selected parton densities, kinematical restrictions, | ||
* Weighted or unweighted events can be generated. This option is available via main menu //Edit -> Settings -> Generated events// or via popup menu. | * Weighted or unweighted events can be generated. This option is available via main menu //Edit -> Settings -> Generated events// or via popup menu. | ||
- | * If one needs to generate the Les Houches Event file, one has to mark corresponding option before the calculation starts. Note that this option affects the speed of the calculations. | + | * If one needs to generate the [[https:// |
* The calculation will start by choosing the corresponding option in main menu (// | * The calculation will start by choosing the corresponding option in main menu (// | ||
* 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 (CCFM) | ||
| A0 (CCFM) | | A0 (CCFM) | ||
| B0 (CCFM) | | B0 (CCFM) | ||
| JH' | | JH' | ||
| JH' | | JH' | ||
- | | KMR (MMHT'2014) | 1 | 5 | 211 | [[https:// | + | | KLSZ'2020 (KMR) | 1 | 4 | 143 | [[https:// |
- | | KMR (NNPDF3.1) | + | | PB NLO set 1 | 2 | 4 | 118 | [[https:// |
- | | KMR (DAS set 1) | 1 | 4 | 143 | [[https:// | + | | PB NLO set 2 | 2 | 4 | 118 | [[https:// |
- | | KMR (DAS set 2) | 1 | 4 | 143 | [[https:// | + | |
- | | PB NLO set 1 | 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: | ||
+ | one just have to upload it from the separate data file prepared in the standard [[https:// | ||
===== Strong coupling and masses of particles ===== | ===== Strong coupling and masses of particles ===== | ||
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The Les Houche Event '' | The Les Houche Event '' | ||
- | We mention the basic features of the '' | + | We mention the basic features of the '' |
* The generated events could be weighted or unweighted. In first case, the sum of all the weights is the total cross section of the subprocess. | * The generated events could be weighted or unweighted. In first case, the sum of all the weights is the total cross section of the subprocess. | ||
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* Conventional (collinear) parton densities in a proton are numbered according to the [[https:// | * Conventional (collinear) parton densities in a proton are numbered according to the [[https:// | ||
- | The produced '' | + | The produced '' |
to be compatible with such Monte Carlo generators as [[http:// | to be compatible with such Monte Carlo generators as [[http:// | ||
===== Random number generator ===== | ===== Random number generator ===== | ||
- | Since all the internal variables in PEGASUS are declared as double precision ones, double precision random numbers have to be generated in the Monte-Carlo simulations. The random number generator [[http:// | + | Since all the internal variables in PEGASUS are declared as double precision ones, double precision random numbers have to be generated in the Monte-Carlo simulations. The random number generator [[http:// |
===== References ===== | ===== References ===== | ||
- | * A.V. Lipatov, M.A. Malyshev, S.P. Baranov, | + | * A.V. Lipatov, M.A. Malyshev, S.P. Baranov, |
===== Acknowledgements ====== | ===== Acknowledgements ====== | ||
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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), | ||
+ | Gennady Lykasov (JINR, Dubna) and Nizami Abdulov. We thank Vladimir Lyubushkin (JINR, Dubna) and Alsu Bagdatova (LPI, Moscow), who contributed significantly to the functionality and stability of PEGASUS. | ||
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.txt · Last modified: 15/04/2024 10:14 by lipatov