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Manuscript Title: SHARE with CHARM
Authors: M. Petran, J. Letessier, J. Rafelski, G. Torrieri
Program title: SHARE with CHARM
Catalogue identifier: ADVD_v3_0
Distribution format: tar.gz
Journal reference: Comput. Phys. Commun. 185(2014)2056
Programming language: FORTRAN77, C++.
Computer: PC, Intel 64-bit, 3 GB RAM (not hardware dependent).
Operating system: GNU Linux: Ubuntu, Debian, Fedora (not OS dependent).
RAM: 615 MB
Keywords: SHARE, Statistical hadronization model, SHM, Quark-gluon plasma, QGP, Strangeness production, Charm production, Hadron fluctuations, Relativistic heavy-ion collisions, RHIC, LHC.
Classification: 11.2, 11.3.

External routines: Standard C++ library, CERNLIB library

Does the new version supersede the previous version?: Yes

Nature of problem:
The Understanding of hadron production incorporating the four u, d, s, c quark flavors is essential for the understanding of the properties of quark-gluon plasma created in relativistic heavy-ion collisions in the large-hadron collider (LHC) energy domain. We describe hadron production by a hot fireball within the statistical hadronization model (SHM) allowing for the chemical nonequilibrium of all quark flavors individually. By fitting particle abundances subject to bulk property constraints in the source, we find the best SHM model parameters. This approach allows the testing of physical hypotheses regarding hadron production mechanisms in relativistic heavy-ion collisions, physical properties of the source at hadronization and the validity of the statistical hadronization model itself. The abundance of light hadrons made of u, d and s constituent quarks [2] and their fluctuations [3] were the core physics contents of the prior releases SHAREv1.x and v2.x respectively. We now consider the hadronization of the heavier charm quarks, a phenomenon of relevance in the analysis of recent and forthcoming LHC results. We introduce bulk matter constraints such as a prescribed charge to baryon ratio originating in the initial state valance u and d quark content of colliding nuclei. More generally, all the bulk physical properties of the particle source such as energy, entropy, pressure, strangeness content and baryon number of the fireball at hadronization are evaluated and all of these can be used as fit constraints. The charm quark degree of freedom is handled as follows: given an input number of charm quark pairs at the time of charm chemical freeze-out, we populate charm hadron yield according to rules of statistical hadronization for a prescribed set of parameters associated with the particle source, such as bulk matter fugacities. A seperate charm hadronization temperature can be chosen and fitted, and as an option it is possible to make this temperature the same as the fitted hadronization temperature of u, d, s-quarks. Charm hadron resonances decay feeding "stable" charm hadrons. These stable charm hadrons are so short-lived that within current technological detector capabilities practically all their decay products are feeding light hadron yields. These charm decay feeds are changing the abundances of produced hadrons in a pattern that differs from particle to particle.

Solution method:
SHARE with CHARM builds in its approach upon the numerical method developed for its predecessor, SHARE [2, 3] for the evaluation of the distribution of light (u, d, s) hadrons. SHARE with CHARM distributes a prescribed number Nccbar of charm c + cbar quarks into individual charm hadrons applying statistical hadronization rules in a newly added computation module 'CHARM' obtaining the yields evaluating appropriate series of Bessel functions. Similarly to light hadrons, the charm hadrons decays are evaluated using pre-existent tables derived from PDG listing [1], proceeding from the heaviest to the lightest particle. The yields of each hadron are obtained using decay branching ratio tables of the mother particle yield - where data was not available, an appropriate theoretical model was implemented to assure that all particles decayed with 100% probability. Each of the resultant daughter hadron contributions is added to this u, d, s hadron yield computed independently for the related set of SHM parameters in the SHARE module. The total yield is subsequently subject to the weak decays (WD) of strange hadrons. A user generated or default WD control file defines what portion of the u, d, s particle yield decays weakly feeding other particles in turn, and which fraction given the detection capability is observed. Once final observable hadron yields are so obtained, we compare these with the experimental data aiming in an iteration to find the best set of prescribed SHM parameters for the yield of u, d, s hadrons observed.. The CHARM module is associated with two new SHM parameters, the charm hadronization temperature Tcharm (which can be defaulted to T obtained for the other u, d, s hadrons) and the total yield of Nccbar = c + cbar quarks, called Ncbc. These and all other SHM parameters are discussed in the text.

Reasons for new version:
Since the release of SHAREv1 in 2004 [2] and SHAREv2 in 2006 [3], heavy-ion collision experiments underwent major development in both detector technology and collision energy. The forthcoming tracker upgrade of STAR at BNL Relativistic Heavy Ion Collider (RHIC) and the current tracking precision of ALICE at CERN Large Hadron Collider (LHC) require upgrades of the SHARE program described below.
In the anticipation of significant charm abundance at LHC, SHARE with CHARM allows the study of all charm hadron production. Charm hadron decays are particularly important because they are a significant source of multistrange hadrons. The introduction of the charm component of the hadron spectrum into SHM is crucial for correct interpretation of particle production and QGP fireball properties at hadronization in heavy-ion collisions at TeV energy scale. SHARE with CHARM is an easy-to-use program, which offers a common framework for SHM analysis of all contemporary heavy-ion collision experiments for the coming years.

Summary of revisions:
The charm hadron mass spectrum and decays have been fully implemented in the provided program package. We provide a current up-to-date detailed list of charm hadrons and resonances together with their numerous decay channels within the set of fully updated input files that correspond to the present PDG status [1]. Considering the enhanced tracking capabilities of LHC experiments and similar RHIC capability, the default behavior of weak decay feed-down has been updated to not accept any weak feed-down unless specified otherwise by the user. The common framework for all contemporary heavy-ion experiments required an update of the format of the particle list and of the content to correspond to present day PDG. SHARE with CHARM is backward compatible with the previous release, SHAREv2, in terms of calculation capabilities and use of control files. However, the SHARE user may need to update and or add individual input file command lines in order to assure that same tasks are performed, considering that defaults, e.g., characterizing weak decays, have been modified. Furthermore quite a few interface improvements have been implemented and are described in detail further in this manual. They allow considerable simplification of control files.

Running time:
From a few seconds in the case of calculating hadron yields and bulk properties given a prescribed set of model parameters, to ~ 30 hours in the case of fitting all parameters to experimental data and calculation with finite widths. Sample calculation provided in the program package, which demonstrates the program capabilities other than calculation with finite widths, took just under 2 hours on both 2.1 GHz CPU (2MB L2 cache) laptop and 2.5 GHz CPU (6MB L2 cache) cluster computing node. Simple fit of model parameters to a data set (provided as default in the package) takes about 5 minutes.

References:
[1] J. Beringer et al. [Particle Data Group Collaboration], Phys. Rev. D 86, 010001 (2012).
[2] G. Torrieri, S. Steinke, W. Broniowski, W. Florkowski, J. Letessier and J. Rafelski, Comput. Phys. Commun. 167(2005)229 [nucl-th/0404083].
[3] G. Torrieri, S. Jeon, J. Letessier and J. Rafelski, Comput. Phys. Commun. 175(2006)635 [nucl-th/0603026].