[u/mrichter/AliRoot.git] / TAmpt / AMPT / amptsetdef.f

      SUBROUTINE AMPTSETDEF
c
cgsfs added following line to match C++ call
      double precision xmp, xmu, alpha, rscut2, cutof2
      double precision smearp,smearh,dpcoal,drcoal,ecritl
      character*25 amptvn
      COMMON/HMAIN1/EATT,JATT,NATT,NT,NP,N0,N01,N10,N11
      COMMON /HPARNT/HIPR1(100), IHPR2(50), HINT1(100), IHNT2(50)
      COMMON/LUDAT1A/MSTU(200),PARU(200),MSTJ(200),PARJ(200)
      COMMON /ARPRNT/ ARPAR1(100), IAPAR2(50), ARINT1(100), IAINT2(50)
      COMMON /AROUT/ IOUT
      COMMON /AREVT/ IAEVT, IARUN, MISS
      COMMON /smearz/smearp,smearh
      COMMON/RNDF77/NSEED
      common/anim/nevent,isoft,isflag,izpc
c     parton coalescence radii in case of string melting:
      common /coal/dpcoal,drcoal,ecritl
      common/snn/efrm,npart1,npart2
c     initialization value for parton cascade:
      common /para2/ xmp, xmu, alpha, rscut2, cutof2
      common /para7/ ioscar,nsmbbbar,nsmmeson
      common /para8/ idpert,npertd,idxsec
      common /rndm3/ iseedp
c     initialization value for hadron cascade:
      COMMON /RUN/ NUM
      common/input1/ MASSPR,MASSTA,ISEED,IAVOID,DT
      COMMON /INPUT2/ ILAB, MANYB, NTMAX, ICOLL, INSYS, IPOT, MODE, 
     &   IMOMEN, NFREQ, ICFLOW, ICRHO, ICOU, KPOTEN, KMUL
      common/oscar1/iap,izp,iat,izt
      common/oscar2/FRAME,amptvn
      common/resdcy/NSAV,iksdcy,ikstardcy
clin-6/2009:
c      common/phidcy/iphidcy
      common/phidcy/iphidcy,pttrig,ntrig,maxmiss
      common/embed/iembed,pxqembd,pyqembd,xembd,yembd
      common/popcorn/ipop

      EXTERNAL HIDATA, PYDATA, LUDATA, ARDATA, PPBDAT, zpcbdt
      SAVE   
c****************

c     flag to select default AMPT or string melting:
      isoft    = 4		! ISOFT (D=1): select Default AMPT or String Melting(see below)
c     read initialization value for hadron cascade:
      NTMAX    = 150		! NTMAX: number of timesteps (D=150), see below
      DT       = 0.2		! DT: timestep in fm (hadron cascade time= DT*NTMAX) (D=0.2)
c     parj(41) and (42) are a and b parameters in Lund string fragmentation:
      PARJ(41) = 0.5		! PARJ(41): parameter a in Lund symmetric splitting function
      PARJ(42) = 0.9      	! PARJ(42): parameter b in Lund symmetric splitting function
c     IHPR2(11)=3 (or 2) allows the popcorn mechanism in PYTHIA and 
c     increase the net-baryon stopping in rapidity (value HIJING is 1):
      ipop      = 1	      	! (D=1,yes;0,no) flag for popcorn mechanism(netbaryon stopping)
c     PARJ(5) controls the fraction of BMBbar vs BBbar in popcorn:
      PARJ(5)   = 1.0	      	! PARJ(5) to control BMBbar vs BBbar in popcorn (D=1.0)
c     shadowing flag in HIJING:
      IHPR2(6)  = 1		! shadowing flag (Default=1,yes; 0,no)
c     quenching flag in HIJING:
      IHPR2(4)  = 0		! quenching flag (D=0,no; 1,yes)
c     quenching rate when quenching flag is on (=1.0 GeV/fm):
      HIPR1(14) = 2.0		! quenching parameter -dE/dx (GeV/fm) in case quenching flag=1
c     Minimum pt of hard or semihard scatterings in HIJING: D=2.0 GeV. 
      HIPR1(8) = 2.0		! p0 cutoff in HIJING for minijet productions (D=2.0)
c     read initialization value for parton cascade:
      xmu      = 3.2264d0	! parton screening mass in fm^(-1) (D=3.2264d0), see below
      izpc     = 0		! IZPC: (D=0 forward-angle parton scatterings; 100,isotropic)
      alpha    = 0.3333d0	! alpha in parton cascade
c     quark coalescence radii in momentum and space for string melting:
      dpcoal   = 1d6		! dpcoal in GeV
      drcoal   = 1d6		! drcoal in fm
c     flag: read in HIJING random # seed at runtime(1) or from input.ampt(D=0):
      ihjsed   = 11		! ihjsed: take HIJING seed from below (D=0)or at runtime(11)
c     2 seeds for random number generators in HIJING/hadron cascade and ZPC:
      nseed    = 53153511	! random seed for HIJING
      iseedp   = 8		! random seed for parton cascade
      iksdcy   = 0		! flag for Ks0 weak decays (D=0,no; 1,yes)
      ikstardcy   = 0		! flag for K* weak decays (D=0,no; 1,yes)
      iphidcy  = 0		! flag for phi decays at end of hadron cascade (D=1,yes; 0,no)
c     flag for OSCAR output for final partons and hadrons:
      ioscar   = 0		! optional OSCAR output (D=0,no; 1,yes; 2&3,more parton info)
clin-5/2008     flag for perturbative treatment of deuterons:
      idpert   = 0		! flag for perturbative deuteron calculation (D=0,no; 1or2,yes)
      npertd   = 1		! integer factor for perturbative deuterons(>=1 & <=10000)
      idxsec   = 1		! choice of cross section assumptions for deuteron reactions
clin-6/2009 To select events that have at least 1 high-Pt minijet parton:
      pttrig   = -7.		! Pt in GeV: generate events with >=1 minijet above this value
      maxmiss  = 1000		! maxmiss (D=1000): maximum # of tries to repeat a HIJING event
      IHPR2(2) = 3		! flag to turn off initial and final state radiation (D=3)
      IHPR2(5) = 1		! flag to turn off Kt kick (D=1)
clin-6/2009 To embed a back-to-back q/qbar pair into each event:
      iembed   = 0		! flag to turn on quark pair embedding (D=0,no; 1to4:yes)
      pxqembd  = 7.             ! Initial Px and Py values (GeV) of the embedded quark (u or d)
      pyqembd  = 0.
      xembd    = 0.             ! Initial x & y values (fm) of the embedded back-to-back q/qbar
      yembd    = 0.
      nsembd   = 1              ! nsembd(D=0), psembd (in GeV),tmaxembd (in radian).
      psembd   = 5.
      tmaxembd = 0.
clin-7/2009 Allow modification of nuclear shadowing:
      ishadow  = 0 		! Flag to enable users to modify shadowing (D=0,no; 1,yes)
      dshadow  = 1.d0		! Factor used to modify nuclear shadowing
c
      RETURN
      END

c$$$%%%%%%%%%% Further explanations:
c$$$ISOFT:  1 Default, 
c$$$        4 String Melting.
c$$$PARJ(41) & (42): 2.2 & 0.5/GeV^2 used for heavy ion (Au+Au, Pb+Pb) collisions,
c$$$        while the HIJING values (0.5 & 0.9/GeV^2) describe well 
c$$$        Nch in pp collisions and are used for d-Au collisions.
c$$$NTMAX:	number of time-steps for hadron cascade. 
c$$$	Use a large value (e.g. 1000) for HBT studies in heavy ion collisions.
c$$$	Using NTMAX=3 effectively turns off hadronic cascade.
c$$$parton screening mass (in 1/fm): its square is inversely proportional to 
c$$$	the parton cross section. Use D=3.2264d0 for 3mb cross section, 
c$$$	and 2.2814d0 for 6mb. Using 1d4 effectively turns off parton cascade.
c$$$ihjsed: if =11, take HIJING random seed at runtime so that 
c$$$	every run may be automatically different (see file 'exec').
c$$$iksdcy: flag for Ks0 weak decays for comparison with data.
c$$$ikstardcy: flag for K* weak decays for comparison with data.
c$$$iphidcy: flag for phi meson decays at the end of hadron cascade for comparison 
c$$$	with data; default is yes; use 0 to turn off these decays. 
c$$$	Note: phi meson decay during hadron cascade is always enabled.
c$$$ioscar:	0 Dafault,
c$$$	1 Write output in the OSCAR format,
c$$$	2 Write out the complete parton information 
c$$$		(ana/parton-initial-afterPropagation.dat)
c$$$        	right after string melting (before parton cascade),
c$$$	3 Write out several more files on parton information (see readme).
c$$$idpert:	flag for perturbative deuteron and antideuteron calculations 
c$$$	with results in ana/ampt_pert.dat:
c$$$	0 No perturbative calculations,
c$$$	1 Trigger a production of NPERTD perturbative deuterons 
c$$$		in each NN collision,	
c$$$	2 Trigger a production of NPERTD perturbative deuterons only in 
c$$$		an NN collision where a conventional deuteron is produced.
c$$$	Note: conventional deuteron calculations are always performed
c$$$		with results in ana/ampt.dat.
c$$$NPERTD:	number of perturbative deuterons produced in each triggered collision;
c$$$	setting it to 0 turns off perturbative deuteron productions.
c$$$idxsec: choose a cross section model for deuteron inelastic/elastic collisions:
c$$$	1: same |matrix element|**2/s (after averaging over initial spins 
c$$$		and isospins) for B+B -> deuteron+meson at the same sqrt(s);
c$$$	2: same |matrix element|**2/s for B+B -> deuteron+meson 
c$$$		at the same sqrt(s)-threshold;
c$$$	3: same |matrix element|**2/s for deuteron+meson -> B+B 
c$$$		at the same sqrt(s);
c$$$ 	4: same |matrix element|**2/s for deuteron+meson -> B+B 
c$$$		at the same sqrt(s)-threshold;
c$$$	1 or 3 also chooses the same cross section for deuteron+meson or baryon
c$$$		elastic collision at the same sqrt(s);
c$$$	2 or 4 also chooses the same cross section for deuteron+meson or baryon
c$$$		elastic collision at the same sqrt(s)-threshold.
c$$$%%%%%%%%%% For jet studies:
c$$$pttrig:	generate events with at least 1 initial minijet parton above this Pt 
c$$$	value, otherwise repeat HIJING event until reaching maxmiss tries;
c$$$	use a negative value to disable this requirement and get normal events.
c$$$maxmiss: maximum number of tries for the repetition of a HIJING event to obtain
c$$$	a minijet above the Pt value of pttrig;	increase maxmiss if some events
c$$$	fail to generate at least 1 initial minijet parton above pttrig. 
c$$$	it is safer to set a large value for high pttrig and/or large b value
c$$$	and/or smaller colliding nuclei.
c$$$IHPR2(2): flag to turn off initial and final state radiation: 
c$$$	0 both radiation off, 1 only final off, 2 only initial off, 3 both on.
c$$$IHPR2(5): flag to turn off Pt kick due to soft interactions: 0 off, 1 on.
c$$$	Setting both IHPR2(2) and IHPR2(5) to zero makes it more likely to 
c$$$	have two high-Pt minijet partons that are close to back-to-back.
c$$$%%%%%%%%%% To embed a back-to-back light q/qbar jet pair 
c$$$%%%%%%%%%%  and a given number of soft pions along each jet into each event:
c$$$iembed: flag to turn on quark pair embedding: 
c$$$        1: on with fixed position(xembd,pembd) and Pt(pxqembd,pyqembd);
c$$$        2: on with fixed position(xembd,pembd) and random azimuthal angle
c$$$         with Pt-magnitude given by sqrt(pxqembd^2+pyqembd^2); 
c$$$        3: on with random position and fixed Pt(pxqembd,pyqembd);
c$$$        4: on with random position and random random azimuthal angle
c$$$         with Pt-magnitude given by sqrt(pxqembd^2+pyqembd^2); 
c$$$	 for iembed=3 or 4: need a position file "embed-jet-xy.txt";
c$$$	Other integers: off.
c$$$pxqembd, pyqembd: sqrt(pxqembd^2+pyqembd^2) > 70MeV/c is required;
c$$$	the embedded quark and antiquark have pz=0.
c$$$xembd, yembd: the embedded quark and antiquark jets have z=0 initially. Note: 
c$$$	the x-axis is defined as the direction along the impact parameter.
c$$$nsembd:	number of soft pions to be embedded with each high-Pt parton
c$$$	in the embedded jet pair.
c$$$psembd: Momentum of each embedded soft pion in GeV.
c$$$tmaxembd: maximum angle(rad) of embedded soft pions relative to high-Pt parton.
c$$$%%%%%%%%%% User modification of nuclear shadowing:
c$$$ishadow: set to 1 to enable users to adjust nuclear shadowing
c$$$	provided the shadowing flag IHPR2(6) is turned on; default value is 0. 
c$$$dshadow: valid when ishadow=1; this parameter modifies the HIJING shadowing
c$$$	parameterization Ra(x,r)==1+fa(x,r) via Ra(x,r)==1+fa(x,r)*dshadow,  
c$$$	so the value of 0.d0 turns off shadowing 
c$$$	and the value of 1.d0 uses the default HIJING shadowing;  
c$$$	currently limited to 0.d0<=dshadow<=1.d0 to make sure Ra(x,r)>0.
Commit	Line	Data
0119ef9a	1	SUBROUTINE AMPTSETDEF
	2	c
	3	cgsfs added following line to match C++ call
	4	double precision xmp, xmu, alpha, rscut2, cutof2
	5	double precision smearp,smearh,dpcoal,drcoal,ecritl
	6	character*25 amptvn
	7	COMMON/HMAIN1/EATT,JATT,NATT,NT,NP,N0,N01,N10,N11
	8	COMMON /HPARNT/HIPR1(100), IHPR2(50), HINT1(100), IHNT2(50)
	9	COMMON/LUDAT1A/MSTU(200),PARU(200),MSTJ(200),PARJ(200)
	10	COMMON /ARPRNT/ ARPAR1(100), IAPAR2(50), ARINT1(100), IAINT2(50)
	11	COMMON /AROUT/ IOUT
	12	COMMON /AREVT/ IAEVT, IARUN, MISS
	13	COMMON /smearz/smearp,smearh
	14	COMMON/RNDF77/NSEED
	15	common/anim/nevent,isoft,isflag,izpc
	16	c parton coalescence radii in case of string melting:
	17	common /coal/dpcoal,drcoal,ecritl
	18	common/snn/efrm,npart1,npart2
	19	c initialization value for parton cascade:
	20	common /para2/ xmp, xmu, alpha, rscut2, cutof2
	21	common /para7/ ioscar,nsmbbbar,nsmmeson
	22	common /para8/ idpert,npertd,idxsec
	23	common /rndm3/ iseedp
	24	c initialization value for hadron cascade:
	25	COMMON /RUN/ NUM
	26	common/input1/ MASSPR,MASSTA,ISEED,IAVOID,DT
	27	COMMON /INPUT2/ ILAB, MANYB, NTMAX, ICOLL, INSYS, IPOT, MODE,
	28	& IMOMEN, NFREQ, ICFLOW, ICRHO, ICOU, KPOTEN, KMUL
	29	common/oscar1/iap,izp,iat,izt
	30	common/oscar2/FRAME,amptvn
05cdcf94	31	common/resdcy/NSAV,iksdcy,ikstardcy
0119ef9a	32	clin-6/2009:
	33	c common/phidcy/iphidcy
	34	common/phidcy/iphidcy,pttrig,ntrig,maxmiss
	35	common/embed/iembed,pxqembd,pyqembd,xembd,yembd
	36	common/popcorn/ipop
	37
	38	EXTERNAL HIDATA, PYDATA, LUDATA, ARDATA, PPBDAT, zpcbdt
	39	SAVE
	40	c****************
	41
	42	c flag to select default AMPT or string melting:
63929975	43	isoft = 4 ! ISOFT (D=1): select Default AMPT or String Melting(see below)
0119ef9a	44	c read initialization value for hadron cascade:
	45	NTMAX = 150 ! NTMAX: number of timesteps (D=150), see below
	46	DT = 0.2 ! DT: timestep in fm (hadron cascade time= DT*NTMAX) (D=0.2)
	47	c parj(41) and (42) are a and b parameters in Lund string fragmentation:
a004b331	48	PARJ(41) = 0.5 ! PARJ(41): parameter a in Lund symmetric splitting function
a004b331	49	PARJ(42) = 0.9 ! PARJ(42): parameter b in Lund symmetric splitting function
0119ef9a	50	c IHPR2(11)=3 (or 2) allows the popcorn mechanism in PYTHIA and
	51	c increase the net-baryon stopping in rapidity (value HIJING is 1):
	52	ipop = 1 ! (D=1,yes;0,no) flag for popcorn mechanism(netbaryon stopping)
	53	c PARJ(5) controls the fraction of BMBbar vs BBbar in popcorn:
	54	PARJ(5) = 1.0 ! PARJ(5) to control BMBbar vs BBbar in popcorn (D=1.0)
	55	c shadowing flag in HIJING:
	56	IHPR2(6) = 1 ! shadowing flag (Default=1,yes; 0,no)
	57	c quenching flag in HIJING:
	58	IHPR2(4) = 0 ! quenching flag (D=0,no; 1,yes)
	59	c quenching rate when quenching flag is on (=1.0 GeV/fm):
	60	HIPR1(14) = 2.0 ! quenching parameter -dE/dx (GeV/fm) in case quenching flag=1
	61	c Minimum pt of hard or semihard scatterings in HIJING: D=2.0 GeV.
	62	HIPR1(8) = 2.0 ! p0 cutoff in HIJING for minijet productions (D=2.0)
	63	c read initialization value for parton cascade:
	64	xmu = 3.2264d0 ! parton screening mass in fm^(-1) (D=3.2264d0), see below
	65	izpc = 0 ! IZPC: (D=0 forward-angle parton scatterings; 100,isotropic)
a004b331	66	alpha = 0.3333d0 ! alpha in parton cascade
0119ef9a	67	c quark coalescence radii in momentum and space for string melting:
	68	dpcoal = 1d6 ! dpcoal in GeV
	69	drcoal = 1d6 ! drcoal in fm
	70	c flag: read in HIJING random # seed at runtime(1) or from input.ampt(D=0):
48beeea0	71	ihjsed = 11 ! ihjsed: take HIJING seed from below (D=0)or at runtime(11)
0119ef9a	72	c 2 seeds for random number generators in HIJING/hadron cascade and ZPC:
	73	nseed = 53153511 ! random seed for HIJING
	74	iseedp = 8 ! random seed for parton cascade
	75	iksdcy = 0 ! flag for Ks0 weak decays (D=0,no; 1,yes)
05cdcf94	76	ikstardcy = 0 ! flag for K* weak decays (D=0,no; 1,yes)
63929975	77	iphidcy = 0 ! flag for phi decays at end of hadron cascade (D=1,yes; 0,no)
0119ef9a	78	c flag for OSCAR output for final partons and hadrons:
	79	ioscar = 0 ! optional OSCAR output (D=0,no; 1,yes; 2&3,more parton info)
	80	clin-5/2008 flag for perturbative treatment of deuterons:
	81	idpert = 0 ! flag for perturbative deuteron calculation (D=0,no; 1or2,yes)
	82	npertd = 1 ! integer factor for perturbative deuterons(>=1 & <=10000)
	83	idxsec = 1 ! choice of cross section assumptions for deuteron reactions
	84	clin-6/2009 To select events that have at least 1 high-Pt minijet parton:
	85	pttrig = -7. ! Pt in GeV: generate events with >=1 minijet above this value
	86	maxmiss = 1000 ! maxmiss (D=1000): maximum # of tries to repeat a HIJING event
	87	IHPR2(2) = 3 ! flag to turn off initial and final state radiation (D=3)
	88	IHPR2(5) = 1 ! flag to turn off Kt kick (D=1)
	89	clin-6/2009 To embed a back-to-back q/qbar pair into each event:
	90	iembed = 0 ! flag to turn on quark pair embedding (D=0,no; 1to4:yes)
	91	pxqembd = 7. ! Initial Px and Py values (GeV) of the embedded quark (u or d)
	92	pyqembd = 0.
	93	xembd = 0. ! Initial x & y values (fm) of the embedded back-to-back q/qbar
	94	yembd = 0.
	95	nsembd = 1 ! nsembd(D=0), psembd (in GeV),tmaxembd (in radian).
	96	psembd = 5.
	97	tmaxembd = 0.
	98	clin-7/2009 Allow modification of nuclear shadowing:
	99	ishadow = 0 ! Flag to enable users to modify shadowing (D=0,no; 1,yes)
	100	dshadow = 1.d0 ! Factor used to modify nuclear shadowing
	101	c
	102	RETURN
	103	END
	104
	105	c$$$%%%%%%%%%% Further explanations:
	106	c$$$ISOFT: 1 Default,
	107	c$$$ 4 String Melting.
	108	c$$$PARJ(41) & (42): 2.2 & 0.5/GeV^2 used for heavy ion (Au+Au, Pb+Pb) collisions,
	109	c$$$ while the HIJING values (0.5 & 0.9/GeV^2) describe well
	110	c$$$ Nch in pp collisions and are used for d-Au collisions.
	111	c$$$NTMAX: number of time-steps for hadron cascade.
	112	c$$$ Use a large value (e.g. 1000) for HBT studies in heavy ion collisions.
	113	c$$$ Using NTMAX=3 effectively turns off hadronic cascade.
	114	c$$$parton screening mass (in 1/fm): its square is inversely proportional to
	115	c$$$ the parton cross section. Use D=3.2264d0 for 3mb cross section,
	116	c$$$ and 2.2814d0 for 6mb. Using 1d4 effectively turns off parton cascade.
	117	c$$$ihjsed: if =11, take HIJING random seed at runtime so that
	118	c$$$ every run may be automatically different (see file 'exec').
	119	c$$$iksdcy: flag for Ks0 weak decays for comparison with data.
05cdcf94	120	c$$$ikstardcy: flag for K* weak decays for comparison with data.
0119ef9a	121	c$$$iphidcy: flag for phi meson decays at the end of hadron cascade for comparison
	122	c$$$ with data; default is yes; use 0 to turn off these decays.
	123	c$$$ Note: phi meson decay during hadron cascade is always enabled.
	124	c$$$ioscar: 0 Dafault,
	125	c$$$ 1 Write output in the OSCAR format,
	126	c$$$ 2 Write out the complete parton information
	127	c$$$ (ana/parton-initial-afterPropagation.dat)
	128	c$$$ right after string melting (before parton cascade),
	129	c$$$ 3 Write out several more files on parton information (see readme).
	130	c$$$idpert: flag for perturbative deuteron and antideuteron calculations
	131	c$$$ with results in ana/ampt_pert.dat:
	132	c$$$ 0 No perturbative calculations,
	133	c$$$ 1 Trigger a production of NPERTD perturbative deuterons
	134	c$$$ in each NN collision,
	135	c$$$ 2 Trigger a production of NPERTD perturbative deuterons only in
	136	c$$$ an NN collision where a conventional deuteron is produced.
	137	c$$$ Note: conventional deuteron calculations are always performed
	138	c$$$ with results in ana/ampt.dat.
	139	c$$$NPERTD: number of perturbative deuterons produced in each triggered collision;
	140	c$$$ setting it to 0 turns off perturbative deuteron productions.
	141	c$$$idxsec: choose a cross section model for deuteron inelastic/elastic collisions:
	142	c$$$ 1: same \|matrix element\|**2/s (after averaging over initial spins
	143	c$$$ and isospins) for B+B -> deuteron+meson at the same sqrt(s);
	144	c$$$ 2: same \|matrix element\|**2/s for B+B -> deuteron+meson
	145	c$$$ at the same sqrt(s)-threshold;
	146	c$$$ 3: same \|matrix element\|**2/s for deuteron+meson -> B+B
	147	c$$$ at the same sqrt(s);
	148	c$$$ 4: same \|matrix element\|**2/s for deuteron+meson -> B+B
	149	c$$$ at the same sqrt(s)-threshold;
	150	c$$$ 1 or 3 also chooses the same cross section for deuteron+meson or baryon
	151	c$$$ elastic collision at the same sqrt(s);
	152	c$$$ 2 or 4 also chooses the same cross section for deuteron+meson or baryon
	153	c$$$ elastic collision at the same sqrt(s)-threshold.
	154	c$$$%%%%%%%%%% For jet studies:
	155	c$$$pttrig: generate events with at least 1 initial minijet parton above this Pt
	156	c$$$ value, otherwise repeat HIJING event until reaching maxmiss tries;
	157	c$$$ use a negative value to disable this requirement and get normal events.
	158	c$$$maxmiss: maximum number of tries for the repetition of a HIJING event to obtain
	159	c$$$ a minijet above the Pt value of pttrig; increase maxmiss if some events
	160	c$$$ fail to generate at least 1 initial minijet parton above pttrig.
	161	c$$$ it is safer to set a large value for high pttrig and/or large b value
	162	c$$$ and/or smaller colliding nuclei.
	163	c$$$IHPR2(2): flag to turn off initial and final state radiation:
	164	c$$$ 0 both radiation off, 1 only final off, 2 only initial off, 3 both on.
	165	c$$$IHPR2(5): flag to turn off Pt kick due to soft interactions: 0 off, 1 on.
	166	c$$$ Setting both IHPR2(2) and IHPR2(5) to zero makes it more likely to
	167	c$$$ have two high-Pt minijet partons that are close to back-to-back.
	168	c$$$%%%%%%%%%% To embed a back-to-back light q/qbar jet pair
	169	c$$$%%%%%%%%%% and a given number of soft pions along each jet into each event:
	170	c$$$iembed: flag to turn on quark pair embedding:
	171	c$$$ 1: on with fixed position(xembd,pembd) and Pt(pxqembd,pyqembd);
	172	c$$$ 2: on with fixed position(xembd,pembd) and random azimuthal angle
	173	c$$$ with Pt-magnitude given by sqrt(pxqembd^2+pyqembd^2);
	174	c$$$ 3: on with random position and fixed Pt(pxqembd,pyqembd);
	175	c$$$ 4: on with random position and random random azimuthal angle
	176	c$$$ with Pt-magnitude given by sqrt(pxqembd^2+pyqembd^2);
	177	c$$$ for iembed=3 or 4: need a position file "embed-jet-xy.txt";
	178	c$$$ Other integers: off.
	179	c$$$pxqembd, pyqembd: sqrt(pxqembd^2+pyqembd^2) > 70MeV/c is required;
	180	c$$$ the embedded quark and antiquark have pz=0.
	181	c$$$xembd, yembd: the embedded quark and antiquark jets have z=0 initially. Note:
	182	c$$$ the x-axis is defined as the direction along the impact parameter.
	183	c$$$nsembd: number of soft pions to be embedded with each high-Pt parton
	184	c$$$ in the embedded jet pair.
185	c$$$psembd: Momentum of each embedded soft pion in GeV.
186	c$$$tmaxembd: maximum angle(rad) of embedded soft pions relative to high-Pt parton.
187	c$$$%%%%%%%%%% User modification of nuclear shadowing:
188	c$$$ishadow: set to 1 to enable users to adjust nuclear shadowing
189	c$$$ provided the shadowing flag IHPR2(6) is turned on; default value is 0.
190	c$$$dshadow: valid when ishadow=1; this parameter modifies the HIJING shadowing
191	c$$$ parameterization Ra(x,r)==1+fa(x,r) via Ra(x,r)==1+fa(x,r)*dshadow,
192	c$$$ so the value of 0.d0 turns off shadowing
193	c$$$ and the value of 1.d0 uses the default HIJING shadowing;
194	c$$$ currently limited to 0.d0<=dshadow<=1.d0 to make sure Ra(x,r)>0.