An interface between HIJING & Geant4-9.5 Umm Al-Qura University-Saudi Arabia Benha University-Egypt Khaled Abdel-Waged

1 5 What is HIJING code? Check of energy-momentum conservation Changes in the Fortran code 4 HIJING interface 3 2 HIJING ingredients

3  HIJING (Heavy Ion Jet Interaction Generator) is a code which takes into account the physics of hard or semi hard parton production. Physical Rev. D 44, 3501(1991).  HIJING is used in many experiments (e.g., ALICE, STAR ) to study:  multiple jets production.  particles produced in high energy pp, pA and AA collisions. HIJING can also provide initial conditions for parton and hadron cascade models (e.g., Multiphase Transport model (AMPT code): HIJING+ZPC+Quark coalescence+ ART Physical Rev. C72, (2005)).  HIJING uses  PYTHIA 5.3 subroutines to generate kinetic variables for each hard scattering.  JETSET 7.2 for jet fragmentation.

4  The core component of HIJING is the two-component model for beam parton interactions.  Parton production is divided into rare hard (P t >P 0 ) and many (small P t exchanges ) soft interactions.  The inclusive hard (jet) cross section is determined by perturbative QCD, while the inclusive soft (σ soft ) cross section is determined phenomenolgically.  In HIJING (version 1.383), P 0 =2 GeV/c and σ soft =57 mb.  In HIJING (version 2), P 0 and σ soft are energy dependent.

5  Glauber theory: superposition of binary nucleon-nucleon collisions.  The eikonal formalism is used to determine the probability for a collision to occur.  For a given collision, one determines: elastic, inelastic, soft, hard and the number of jets produced in a hard interaction.  Nuclear Shadowing (modified parton distribution) and Jet Quenching (modified fragmentation) are taking into account.  PYTHIA routines are called to describe kinematics of hard interactions.  Soft interactions are treated according to the LUND model.  Secondary interactions are neglected.

6  HIJING code contains 2 files: hijing1.383.f and hipyset1.35.f.  hijing1.383.f contains HIJING subroutines: (27 subroutines and 45 functions).  hipyset1.35.f contains PYTHIA and JETSET subroutines (adjusted for HIJING) (68 subroutines and 13 functions)

7  Initialize HIJING (ONLY ONCE) SUBROUTINE HIJSET(EFRM, FRAME, PROJ, TARG, IAP, IZP, IAT, IZT) EFRM: colliding energy (GeV/A) in the frame specified by FRAME. FRAME: character variables (e.g., “CMS” or “LAB”). PROJ, TARG: character variables (e.g. “P”, “A”) IAP, IAT: mass number of projectile and target. But 1 for hadrons! IZP, IZT: charge number of projectile and target nucleus.  Generate events (MANY TIMES) SUBROUTINE HIJING (FRAME, BMIN, BMAX) BMIN, BMAX: the minimum and maximum impact parameter.

The 11 input variables are inserted as follows 1) The HIPARNT common block: COMMON/HIPARNT/HIPR1(100),IHPR2(50),HINT1(100),IHNT2(50) Projectile: IHNT2(1)=IAP // Nucleus (mass number) or IHNT2(1)=1 //Hadron IHNT2(2)=IZP //charge IHNT2(5)=0 //id Projectile code Target: IHNT2(3)=IAT IHNT2(4)=IZT IHNT2(6)=0 //id Target (Nucleus assumed) Rest Mass: HINT1(8)= //projectile HINT1(9)= //Target 8

2) SUBROUTINE HIJSET(EFRM, FRAME, PROJ, TARG, IAP, IZP, IAT, IZT) is replaced with SUBROUTINE HIJSET(EFRM) !Energy is inserted SUBROUTINE HIJING (FRAME, BMIN, BMAX) is replaced with SUBROUTINE HIJING (BMIN, BMAX) !impact parameter is inserted 3) In HIJSET and HIJING subroutines, the statement Frame=”LAB” !frame is inserted is inserted (because Geant4 hadronic cascade models always works in the LABoratory frame) 9

4) Two random generator functions are called: RAN(NSEED=0)  hijing1.383.f RLU(0)  hipyset1.35.f Notice that RAN(0) is not linked to any function!! So, we replace RAN(NSEED) with RLU(0) in hijing1.383.f

5) When running HIJING code in gfortran, the execution is blocked!!: FUNCTION ROMG(X) C This gives the eikonal function from a table Ccalculated in the first call DIMENSION FR(0:1000) DATA I0/0/ COMMON/EIKONAL/FR !New->Khaled IF(I0.NE.0) GO TO 100 DO 50 I=1,1001 XR=(I-1)*0.01 FR(I-1)=OMG0(XR) 50CONTINUE 100I0=1 IF(X.GE.10.0) THEN ROMG=0.0 RETURN ENDIF IX=INT(X*100) ROMG=(FR(IX)*((IX+1)*0.01-X)+FR(IX+1)*(X-IX*0.01))/0.01 RETURN END

 Instantiation of the G4HIJING_Model process in Geant4.  Generation of proton-nucleus and nucleus- nucleus interaction events.

Instantisation G4HIJING_Model Instantisation G4HIJING_Model ApplyYourself Instantiate G4HIJING_Model Initialise C++ variables & HIJING common block data Instantiate G4HIJING_Model Initialise C++ variables & HIJING common block data HIJING Common blocks accessed through C++ structure declarations HIJING Common blocks accessed through C++ structure declarations Determine Projectile & Target Determine Projectile & Target Initialise HIJIN G Common block data for interaction Initialise HIJIN G Common block data for interaction HIJING Common blocks HIJING Common blocks Get default Input HIJING parameters and Initialise Projectle/Target by Call to HIJSET Get default Input HIJING parameters and Initialise Projectle/Target by Call to HIJSET Simulate interaction by Call t o HIJING Transfer information about secondary products to product vector

G4HIJING_Model.cc G4HIJING_Interface.hh G4HIJING_Model.hh G4HIJING_Interface.hh G4HIJING_Model.hh include make hipyset1.35.f hijing1.383.f HIJINGsrc Src HIJING

 G4HIJING_Model(cons tG4String & name=HIJING"); public constructor which calls Initialise (). This initialises all of the variables as required by HIJING and held in FORTRAN common blocks based on the DEFAULT values.  ~G4HIJING_Model (); Class destructor

 virtual G4HadFinalState *ApplyYourself (const G4HadProjectile &theTrack, G4Nucleus &theTarget); Member function to determine the Final State of the interaction process. The Final state is for the results of (and secondaries from) the projectile, described by theTrack, and the target nucleus, described by theTarget. This member function drives HIJING FORTRAN to enter information about a nuclear-nuclear event, and interprets the results into a product vector as a G4HadFinalState object.  G4HIJING_Interface.hh C++ - FORTRAN interface for common blocks and subroutines

Thank you