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We replace the old PACIAE 2.1 and PACIAE 2.2 program series with new ones, respectively. In the new program series, the method of creation of the partonic initial state is changed, an option for calling PYEVNT or PYEVNW in PYTHIA is added, and the few bugs in the calculation for the reduction of strange quark suppression are corrected. New version program summary Program Title: PACIAE version 2.1 & 2.2 Program Files doi: http://dx.doi.org/10.17632/w3g68dj4d9.1 Licensing provisions: CC By 4.0 Programming language: FORTRAN 77 Journal reference of previous version: Comput. Phys. Comm. 184 (2013) 1476, 193 (2015) 89. Does the new version supersede the previous version?: Yes Nature of problem: PYEVNT is the subroutine in PYTHIA to administer the generation of a high-pT event via calls a number of subroutines. PYEVNW is the new subroutine in PYTHIA to administer the generation of an event for new multiple interactions scenario. In previous PACIAE versions only PYEVNT is called, while both PYEVNT and PYEVNW can be called in this new version. Solution method: There has been added a parameter of mstp81 in PACIAE programs and input files of usux.dat (for 21a or 22a) and usu.dat (for 21b, 21c ,22b and 22c). The PACIAE will call PYEVNT when mstp81=1( default) and call PYEVNW when mstp81=21. Reasons for the new version: The method of creation of the partonic initial state is changed, an option for calling PYEVNT or PYEVNW in PYTHIA is added, and the few bugs in the calculation for the reduction of strange quark suppression are corrected in the new version. Summary of revisions: The PACIAE model [1] is a parton and hadron cascade model based on PYTHIA [2]. PACIAE model consists of four stages of the parton initiation, the parton evolution (rescattering), the hadronization, and the hadron evolution (rescattering). The stage of parton initiation is just by means of PYTHIA model and the rest are modeled by us [1]. PYTHIA model is for the high energy elementary particle collisions such as hadron–hadron and lepton–hadron collisions, but PACIAE model is also for high energy lepton–nucleus, hadron–nucleus and nucleus–nucleus collisions. So far, the PACIAE model has three series of PACIAE 2.0 (catalogue identifier: AEKI_v1_0) [1], PACIAE 2.1 (AEKI_v2_0) [3], and PACIAE 2.2 (AEKI_v2_2) [4]. The discrepancy between PACIAE 2.0 and PACIAE 2.1 is just the sampling of momentum x and y components at fixed p T . In the PACIAE 2.0 it is sampled on the circle with radius of p T , but on the circumference of ellipse with half major and minor axes of p T ( 1 + δ p ) and p T ( 1 − δ p ) , respectively in PACIAE 2.1. Including the reaction of lepton–nucleon and lepton–nucleus is the distinction of PACIAE 2.2 series from the PACIAE 2.1. Each series of PACIAE 2.0, PACIAE 2.1 and PACIAE 2.2 consists of a, b, and c packages. The package of PACIAE 2.1a, for instance, is for the high energy elementary collisions, while the PACIAE 2.1b as well as PACIAE 2.1c for the high energy hadron–nucleus and nucleus–nucleus collisions. We refer to [1] for the difference between PACIAE 2.0b and PACIAE 2.0c (PACIAE 2.1b and PACIAE 2.1c as well as PACIAE 2.2b and PACIAE 2.2c). In this replacement the modifications are as follows: 1. The method of creation of a partonic initial state is changed from setting mstj(1)=0 (or mstp(111)=0) before “CALL PYINIT” to adding a “RETURN” statement before the statement of “CALL PYEXEC” in subroutine PYEVNT (PYEVNW) in p21b.f. 2. Correcting the mistakes in the calculation for the mechanism of reduction of strange quark suppression. 3. Calling PYEVNT or PYEVNW is controlled by mstp(81) (=1 or 21) instead of calling PYEVNT only originally. References [1] Ben-Hao Sa, Dai-Mei Zhou, Yu-Liang Yan, Xiao-Mei Li, Sheng-Qin Feng, Bao-Guo Dong, and Xu Cai, Comput. Phys. Comm. 183 (2012) 333. [2] Sjostrand T, Mrenna S, Skands P, J. High Energy Phys., 05 (2006) 026, arXiv:hep-ph/0603175. [3] Ben-Hao Sa, Dai-Mei Zhou, Yu-Liang Yan, Bao-Guo Dong, and Xu Cai, Comput. Phys. Comm. 184 (2013) 1476. [4] Dai-Mei Zhou, Yu-Liang Yan, Xing-Long Li, Xiao-Mei Li, Bao-Guo Dong, Xu Cai, and Ben-Hao Sa, Comput. Phys. Comm. 193 (2015) 89. |
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