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[u/mrichter/AliRoot.git] / HIJING / hipyset1_35 / ludecy_hijing.F
CommitLineData
e74335a4 1* $Id$
2
3C*********************************************************************
4
5 SUBROUTINE LUDECY_HIJING(IP)
6
7C...Purpose: to handle the decay of unstable particles.
8#include "lujets_hijing.inc"
9#include "ludat1_hijing.inc"
10#include "ludat2_hijing.inc"
11#include "ludat3_hijing.inc"
12 DIMENSION VDCY(4),KFLO(4),KFL1(4),PV(10,5),RORD(10),UE(3),BE(3),
13 &WTCOR(10)
14 DATA WTCOR/2.,5.,15.,60.,250.,1500.,1.2E4,1.2E5,150.,16./
15
16C...Functions: momentum in two-particle decays, four-product and
17C...matrix element times phase space in weak decays.
18 PAWT(A,B,C)=SQRT((A**2-(B+C)**2)*(A**2-(B-C)**2))/(2.*A)
19 FOUR(I,J)=P(I,4)*P(J,4)-P(I,1)*P(J,1)-P(I,2)*P(J,2)-P(I,3)*P(J,3)
20 HMEPS(HA)=((1.-HRQ-HA)**2+3.*HA*(1.+HRQ-HA))*
21 &SQRT((1.-HRQ-HA)**2-4.*HRQ*HA)
22
23C...Initial values.
24 NTRY=0
25 NSAV=N
26 KFA=IABS(K(IP,2))
27 KFS=ISIGN(1,K(IP,2))
28 KC=LUCOMP_HIJING(KFA)
29 MSTJ(92)=0
30
31C...Choose lifetime and determine decay vertex.
32 IF(K(IP,1).EQ.5) THEN
33 V(IP,5)=0.
34 ELSEIF(K(IP,1).NE.4) THEN
35 V(IP,5)=-PMAS(KC,4)*LOG(RLU_HIJING(0))
36 ENDIF
37 DO 100 J=1,4
38 100 VDCY(J)=V(IP,J)+V(IP,5)*P(IP,J)/P(IP,5)
39
40C...Determine whether decay allowed or not.
41 MOUT=0
42 IF(MSTJ(22).EQ.2) THEN
43 IF(PMAS(KC,4).GT.PARJ(71)) MOUT=1
44 ELSEIF(MSTJ(22).EQ.3) THEN
45 IF(VDCY(1)**2+VDCY(2)**2+VDCY(3)**2.GT.PARJ(72)**2) MOUT=1
46 ELSEIF(MSTJ(22).EQ.4) THEN
47 IF(VDCY(1)**2+VDCY(2)**2.GT.PARJ(73)**2) MOUT=1
48 IF(ABS(VDCY(3)).GT.PARJ(74)) MOUT=1
49 ENDIF
50 IF(MOUT.EQ.1.AND.K(IP,1).NE.5) THEN
51 K(IP,1)=4
52 RETURN
53 ENDIF
54
55C...Check existence of decay channels. Particle/antiparticle rules.
56 KCA=KC
57 IF(MDCY(KC,2).GT.0) THEN
58 MDMDCY=MDME(MDCY(KC,2),2)
59 IF(MDMDCY.GT.80.AND.MDMDCY.LE.90) KCA=MDMDCY
60 ENDIF
61 IF(MDCY(KCA,2).LE.0.OR.MDCY(KCA,3).LE.0) THEN
62 CALL LUERRM_HIJING(9
63 $ ,'(LUDECY_HIJING:) no decay channel defined')
64 RETURN
65 ENDIF
66 IF(MOD(KFA/1000,10).EQ.0.AND.(KCA.EQ.85.OR.KCA.EQ.87)) KFS=-KFS
67 IF(KCHG(KC,3).EQ.0) THEN
68 KFSP=1
69 KFSN=0
70 IF(RLU_HIJING(0).GT.0.5) KFS=-KFS
71 ELSEIF(KFS.GT.0) THEN
72 KFSP=1
73 KFSN=0
74 ELSE
75 KFSP=0
76 KFSN=1
77 ENDIF
78
79C...Sum branching ratios of allowed decay channels.
80 110 NOPE=0
81 BRSU=0.
82 DO 120 IDL=MDCY(KCA,2),MDCY(KCA,2)+MDCY(KCA,3)-1
83 IF(MDME(IDL,1).NE.1.AND.KFSP*MDME(IDL,1).NE.2.AND.
84 &KFSN*MDME(IDL,1).NE.3) GOTO 120
85 IF(MDME(IDL,2).GT.100) GOTO 120
86 NOPE=NOPE+1
87 BRSU=BRSU+BRAT(IDL)
88 120 CONTINUE
89 IF(NOPE.EQ.0) THEN
90 CALL LUERRM_HIJING(2
91 $ ,'(LUDECY_HIJING:) all decay channels closed by user')
92 RETURN
93 ENDIF
94
95C...Select decay channel among allowed ones.
96 130 RBR=BRSU*RLU_HIJING(0)
97 IDL=MDCY(KCA,2)-1
98 140 IDL=IDL+1
99 IF(MDME(IDL,1).NE.1.AND.KFSP*MDME(IDL,1).NE.2.AND.
100 &KFSN*MDME(IDL,1).NE.3) THEN
101 IF(IDL.LT.MDCY(KCA,2)+MDCY(KCA,3)-1) GOTO 140
102 ELSEIF(MDME(IDL,2).GT.100) THEN
103 IF(IDL.LT.MDCY(KCA,2)+MDCY(KCA,3)-1) GOTO 140
104 ELSE
105 IDC=IDL
106 RBR=RBR-BRAT(IDL)
107 IF(IDL.LT.MDCY(KCA,2)+MDCY(KCA,3)-1.AND.RBR.GT.0.) GOTO 140
108 ENDIF
109
110C...Start readout of decay channel: matrix element, reset counters.
111 MMAT=MDME(IDC,2)
112 150 NTRY=NTRY+1
113 IF(NTRY.GT.1000) THEN
114 CALL LUERRM_HIJING(14
115 $ ,'(LUDECY_HIJING:) caught in infinite loop')
116 IF(MSTU(21).GE.1) RETURN
117 ENDIF
118 I=N
119 NP=0
120 NQ=0
121 MBST=0
122 IF(MMAT.GE.11.AND.MMAT.NE.46.AND.P(IP,4).GT.20.*P(IP,5)) MBST=1
123 DO 160 J=1,4
124 PV(1,J)=0.
125 160 IF(MBST.EQ.0) PV(1,J)=P(IP,J)
126 IF(MBST.EQ.1) PV(1,4)=P(IP,5)
127 PV(1,5)=P(IP,5)
128 PS=0.
129 PSQ=0.
130 MREM=0
131
132C...Read out decay products. Convert to standard flavour code.
133 JTMAX=5
134 IF(MDME(IDC+1,2).EQ.101) JTMAX=10
135 DO 170 JT=1,JTMAX
136 IF(JT.LE.5) KP=KFDP(IDC,JT)
137 IF(JT.GE.6) KP=KFDP(IDC+1,JT-5)
138 IF(KP.EQ.0) GOTO 170
139 KPA=IABS(KP)
140 KCP=LUCOMP_HIJING(KPA)
141 IF(KCHG(KCP,3).EQ.0.AND.KPA.NE.81.AND.KPA.NE.82) THEN
142 KFP=KP
143 ELSEIF(KPA.NE.81.AND.KPA.NE.82) THEN
144 KFP=KFS*KP
145 ELSEIF(KPA.EQ.81.AND.MOD(KFA/1000,10).EQ.0) THEN
146 KFP=-KFS*MOD(KFA/10,10)
147 ELSEIF(KPA.EQ.81.AND.MOD(KFA/100,10).GE.MOD(KFA/10,10)) THEN
148 KFP=KFS*(100*MOD(KFA/10,100)+3)
149 ELSEIF(KPA.EQ.81) THEN
150 KFP=KFS*(1000*MOD(KFA/10,10)+100*MOD(KFA/100,10)+1)
151 ELSEIF(KP.EQ.82) THEN
152 CALL LUKFDI_HIJING(-KFS*INT(1.+(2.+PARJ(2))*RLU_HIJING(0)),0
153 $ ,KFP,KDUMP)
154 IF(KFP.EQ.0) GOTO 150
155 MSTJ(93)=1
156 IF(PV(1,5).LT.PARJ(32)+2.*ULMASS_HIJING(KFP)) GOTO 150
157 ELSEIF(KP.EQ.-82) THEN
158 KFP=-KFP
159 IF(IABS(KFP).GT.10) KFP=KFP+ISIGN(10000,KFP)
160 ENDIF
161 IF(KPA.EQ.81.OR.KPA.EQ.82) KCP=LUCOMP_HIJING(KFP)
162
163C...Add decay product to event record or to quark flavour list.
164 KFPA=IABS(KFP)
165 KQP=KCHG(KCP,2)
166 IF(MMAT.GE.11.AND.MMAT.LE.30.AND.KQP.NE.0) THEN
167 NQ=NQ+1
168 KFLO(NQ)=KFP
169 MSTJ(93)=2
170 PSQ=PSQ+ULMASS_HIJING(KFLO(NQ))
171 ELSEIF(MMAT.GE.42.AND.MMAT.LE.43.AND.NP.EQ.3.AND.MOD(NQ,2).EQ.1)
172 &THEN
173 NQ=NQ-1
174 PS=PS-P(I,5)
175 K(I,1)=1
176 KFI=K(I,2)
177 CALL LUKFDI_HIJING(KFP,KFI,KFLDMP,K(I,2))
178 IF(K(I,2).EQ.0) GOTO 150
179 MSTJ(93)=1
180 P(I,5)=ULMASS_HIJING(K(I,2))
181 PS=PS+P(I,5)
182 ELSE
183 I=I+1
184 NP=NP+1
185 IF(MMAT.NE.33.AND.KQP.NE.0) NQ=NQ+1
186 IF(MMAT.EQ.33.AND.KQP.NE.0.AND.KQP.NE.2) NQ=NQ+1
187 K(I,1)=1+MOD(NQ,2)
188 IF(MMAT.EQ.4.AND.JT.LE.2.AND.KFP.EQ.21) K(I,1)=2
189 IF(MMAT.EQ.4.AND.JT.EQ.3) K(I,1)=1
190 K(I,2)=KFP
191 K(I,3)=IP
192 K(I,4)=0
193 K(I,5)=0
194 P(I,5)=ULMASS_HIJING(KFP)
195 IF(MMAT.EQ.45.AND.KFPA.EQ.89) P(I,5)=PARJ(32)
196 PS=PS+P(I,5)
197 ENDIF
198 170 CONTINUE
199
200C...Choose decay multiplicity in phase space model.
201 180 IF(MMAT.GE.11.AND.MMAT.LE.30) THEN
202 PSP=PS
203 CNDE=PARJ(61)*LOG(MAX((PV(1,5)-PS-PSQ)/PARJ(62),1.1))
204 IF(MMAT.EQ.12) CNDE=CNDE+PARJ(63)
205 190 NTRY=NTRY+1
206 IF(NTRY.GT.1000) THEN
207 CALL LUERRM_HIJING(14
208 $ ,'(LUDECY_HIJING:) caught in infinite loop')
209 IF(MSTU(21).GE.1) RETURN
210 ENDIF
211 IF(MMAT.LE.20) THEN
212 GAUSS=SQRT(-2.*CNDE*LOG(MAX(1E-10,RLU_HIJING(0))))*
213 & SIN(PARU(2)*RLU_HIJING(0))
214 ND=0.5+0.5*NP+0.25*NQ+CNDE+GAUSS
215 IF(ND.LT.NP+NQ/2.OR.ND.LT.2.OR.ND.GT.10) GOTO 190
216 IF(MMAT.EQ.13.AND.ND.EQ.2) GOTO 190
217 IF(MMAT.EQ.14.AND.ND.LE.3) GOTO 190
218 IF(MMAT.EQ.15.AND.ND.LE.4) GOTO 190
219 ELSE
220 ND=MMAT-20
221 ENDIF
222
223C...Form hadrons from flavour content.
224 DO 200 JT=1,4
225 200 KFL1(JT)=KFLO(JT)
226 IF(ND.EQ.NP+NQ/2) GOTO 220
227 DO 210 I=N+NP+1,N+ND-NQ/2
228 JT=1+INT((NQ-1)*RLU_HIJING(0))
229 CALL LUKFDI_HIJING(KFL1(JT),0,KFL2,K(I,2))
230 IF(K(I,2).EQ.0) GOTO 190
231 210 KFL1(JT)=-KFL2
232 220 JT=2
233 JT2=3
234 JT3=4
235 IF(NQ.EQ.4.AND.RLU_HIJING(0).LT.PARJ(66)) JT=4
236 IF(JT.EQ.4.AND.ISIGN(1,KFL1(1)*(10-IABS(KFL1(1))))*
237 & ISIGN(1,KFL1(JT)*(10-IABS(KFL1(JT)))).GT.0) JT=3
238 IF(JT.EQ.3) JT2=2
239 IF(JT.EQ.4) JT3=2
240 CALL LUKFDI_HIJING(KFL1(1),KFL1(JT),KFLDMP,K(N+ND-NQ/2+1,2))
241 IF(K(N+ND-NQ/2+1,2).EQ.0) GOTO 190
242 IF(NQ.EQ.4) CALL LUKFDI_HIJING(KFL1(JT2),KFL1(JT3),KFLDMP,K(N+ND
243 $ ,2))
244 IF(NQ.EQ.4.AND.K(N+ND,2).EQ.0) GOTO 190
245
246C...Check that sum of decay product masses not too large.
247 PS=PSP
248 DO 230 I=N+NP+1,N+ND
249 K(I,1)=1
250 K(I,3)=IP
251 K(I,4)=0
252 K(I,5)=0
253 P(I,5)=ULMASS_HIJING(K(I,2))
254 230 PS=PS+P(I,5)
255 IF(PS+PARJ(64).GT.PV(1,5)) GOTO 190
256
257C...Rescale energy to subtract off spectator quark mass.
258 ELSEIF((MMAT.EQ.31.OR.MMAT.EQ.33.OR.MMAT.EQ.44.OR.MMAT.EQ.45).
259 &AND.NP.GE.3) THEN
260 PS=PS-P(N+NP,5)
261 PQT=(P(N+NP,5)+PARJ(65))/PV(1,5)
262 DO 240 J=1,5
263 P(N+NP,J)=PQT*PV(1,J)
264 240 PV(1,J)=(1.-PQT)*PV(1,J)
265 IF(PS+PARJ(64).GT.PV(1,5)) GOTO 150
266 ND=NP-1
267 MREM=1
268
269C...Phase space factors imposed in W decay.
270 ELSEIF(MMAT.EQ.46) THEN
271 MSTJ(93)=1
272 PSMC=ULMASS_HIJING(K(N+1,2))
273 MSTJ(93)=1
274 PSMC=PSMC+ULMASS_HIJING(K(N+2,2))
275 IF(MAX(PS,PSMC)+PARJ(32).GT.PV(1,5)) GOTO 130
276 HR1=(P(N+1,5)/PV(1,5))**2
277 HR2=(P(N+2,5)/PV(1,5))**2
278 IF((1.-HR1-HR2)*(2.+HR1+HR2)*SQRT((1.-HR1-HR2)**2-4.*HR1*HR2).
279 & LT.2.*RLU_HIJING(0)) GOTO 130
280 ND=NP
281
282C...Fully specified final state: check mass broadening effects.
283 ELSE
284 IF(NP.GE.2.AND.PS+PARJ(64).GT.PV(1,5)) GOTO 150
285 ND=NP
286 ENDIF
287
288C...Select W mass in decay Q -> W + q, without W propagator.
289 IF(MMAT.EQ.45.AND.MSTJ(25).LE.0) THEN
290 HLQ=(PARJ(32)/PV(1,5))**2
291 HUQ=(1.-(P(N+2,5)+PARJ(64))/PV(1,5))**2
292 HRQ=(P(N+2,5)/PV(1,5))**2
293 250 HW=HLQ+RLU_HIJING(0)*(HUQ-HLQ)
294 IF(HMEPS(HW).LT.RLU_HIJING(0)) GOTO 250
295 P(N+1,5)=PV(1,5)*SQRT(HW)
296
297C...Ditto, including W propagator. Divide mass range into three regions.
298 ELSEIF(MMAT.EQ.45) THEN
299 HQW=(PV(1,5)/PMAS(24,1))**2
300 HLW=(PARJ(32)/PMAS(24,1))**2
301 HUW=((PV(1,5)-P(N+2,5)-PARJ(64))/PMAS(24,1))**2
302 HRQ=(P(N+2,5)/PV(1,5))**2
303 HG=PMAS(24,2)/PMAS(24,1)
304 HATL=ATAN((HLW-1.)/HG)
305 HM=MIN(1.,HUW-0.001)
306 HMV1=HMEPS(HM/HQW)/((HM-1.)**2+HG**2)
307 260 HM=HM-HG
308 HMV2=HMEPS(HM/HQW)/((HM-1.)**2+HG**2)
309 HSAV1=HMEPS(HM/HQW)
310 HSAV2=1./((HM-1.)**2+HG**2)
311 IF(HMV2.GT.HMV1.AND.HM-HG.GT.HLW) THEN
312 HMV1=HMV2
313 GOTO 260
314 ENDIF
315 HMV=MIN(2.*HMV1,HMEPS(HM/HQW)/HG**2)
316 HM1=1.-SQRT(1./HMV-HG**2)
317 IF(HM1.GT.HLW.AND.HM1.LT.HM) THEN
318 HM=HM1
319 ELSEIF(HMV2.LE.HMV1) THEN
320 HM=MAX(HLW,HM-MIN(0.1,1.-HM))
321 ENDIF
322 HATM=ATAN((HM-1.)/HG)
323 HWT1=(HATM-HATL)/HG
324 HWT2=HMV*(MIN(1.,HUW)-HM)
325 HWT3=0.
326 IF(HUW.GT.1.) THEN
327 HATU=ATAN((HUW-1.)/HG)
328 HMP1=HMEPS(1./HQW)
329 HWT3=HMP1*HATU/HG
330 ENDIF
331
332C...Select mass region and W mass there. Accept according to weight.
333 270 HREG=RLU_HIJING(0)*(HWT1+HWT2+HWT3)
334 IF(HREG.LE.HWT1) THEN
335 HW=1.+HG*TAN(HATL+RLU_HIJING(0)*(HATM-HATL))
336 HACC=HMEPS(HW/HQW)
337 ELSEIF(HREG.LE.HWT1+HWT2) THEN
338 HW=HM+RLU_HIJING(0)*(MIN(1.,HUW)-HM)
339 HACC=HMEPS(HW/HQW)/((HW-1.)**2+HG**2)/HMV
340 ELSE
341 HW=1.+HG*TAN(RLU_HIJING(0)*HATU)
342 HACC=HMEPS(HW/HQW)/HMP1
343 ENDIF
344 IF(HACC.LT.RLU_HIJING(0)) GOTO 270
345 P(N+1,5)=PMAS(24,1)*SQRT(HW)
346 ENDIF
347
348C...Determine position of grandmother, number of sisters, Q -> W sign.
349 NM=0
350 MSGN=0
351 IF(MMAT.EQ.3.OR.MMAT.EQ.46) THEN
352 IM=K(IP,3)
353 IF(IM.LT.0.OR.IM.GE.IP) IM=0
354 IF(IM.NE.0) KFAM=IABS(K(IM,2))
355 IF(IM.NE.0.AND.MMAT.EQ.3) THEN
356 DO 280 IL=MAX(IP-2,IM+1),MIN(IP+2,N)
357 280 IF(K(IL,3).EQ.IM) NM=NM+1
358 IF(NM.NE.2.OR.KFAM.LE.100.OR.MOD(KFAM,10).NE.1.OR.
359 & MOD(KFAM/1000,10).NE.0) NM=0
360 ELSEIF(IM.NE.0.AND.MMAT.EQ.46) THEN
361 MSGN=ISIGN(1,K(IM,2)*K(IP,2))
362 IF(KFAM.GT.100.AND.MOD(KFAM/1000,10).EQ.0) MSGN=
363 & MSGN*(-1)**MOD(KFAM/100,10)
364 ENDIF
365 ENDIF
366
367C...Kinematics of one-particle decays.
368 IF(ND.EQ.1) THEN
369 DO 290 J=1,4
370 290 P(N+1,J)=P(IP,J)
371 GOTO 510
372 ENDIF
373
374C...Calculate maximum weight ND-particle decay.
375 PV(ND,5)=P(N+ND,5)
376 IF(ND.GE.3) THEN
377 WTMAX=1./WTCOR(ND-2)
378 PMAX=PV(1,5)-PS+P(N+ND,5)
379 PMIN=0.
380 DO 300 IL=ND-1,1,-1
381 PMAX=PMAX+P(N+IL,5)
382 PMIN=PMIN+P(N+IL+1,5)
383 300 WTMAX=WTMAX*PAWT(PMAX,PMIN,P(N+IL,5))
384 ENDIF
385
386C...Find virtual gamma mass in Dalitz decay.
387 310 IF(ND.EQ.2) THEN
388 ELSEIF(MMAT.EQ.2) THEN
389 PMES=4.*PMAS(11,1)**2
390 PMRHO2=PMAS(131,1)**2
391 PGRHO2=PMAS(131,2)**2
392 320 PMST=PMES*(P(IP,5)**2/PMES)**RLU_HIJING(0)
393 WT=(1+0.5*PMES/PMST)*SQRT(MAX(0.,1.-PMES/PMST))*
394 & (1.-PMST/P(IP,5)**2)**3*(1.+PGRHO2/PMRHO2)/
395 & ((1.-PMST/PMRHO2)**2+PGRHO2/PMRHO2)
396 IF(WT.LT.RLU_HIJING(0)) GOTO 320
397 PV(2,5)=MAX(2.00001*PMAS(11,1),SQRT(PMST))
398
399C...M-generator gives weight. If rejected, try again.
400 ELSE
401 330 RORD(1)=1.
402 DO 350 IL1=2,ND-1
403 RSAV=RLU_HIJING(0)
404 DO 340 IL2=IL1-1,1,-1
405 IF(RSAV.LE.RORD(IL2)) GOTO 350
406 340 RORD(IL2+1)=RORD(IL2)
407 350 RORD(IL2+1)=RSAV
408 RORD(ND)=0.
409 WT=1.
410 DO 360 IL=ND-1,1,-1
411 PV(IL,5)=PV(IL+1,5)+P(N+IL,5)+(RORD(IL)-RORD(IL+1))*(PV(1,5)-PS)
412 360 WT=WT*PAWT(PV(IL,5),PV(IL+1,5),P(N+IL,5))
413 IF(WT.LT.RLU_HIJING(0)*WTMAX) GOTO 330
414 ENDIF
415
416C...Perform two-particle decays in respective CM frame.
417 370 DO 390 IL=1,ND-1
418 PA=PAWT(PV(IL,5),PV(IL+1,5),P(N+IL,5))
419 UE(3)=2.*RLU_HIJING(0)-1.
420 PHI=PARU(2)*RLU_HIJING(0)
421 UE(1)=SQRT(1.-UE(3)**2)*COS(PHI)
422 UE(2)=SQRT(1.-UE(3)**2)*SIN(PHI)
423 DO 380 J=1,3
424 P(N+IL,J)=PA*UE(J)
425 380 PV(IL+1,J)=-PA*UE(J)
426 P(N+IL,4)=SQRT(PA**2+P(N+IL,5)**2)
427 390 PV(IL+1,4)=SQRT(PA**2+PV(IL+1,5)**2)
428
429C...Lorentz transform decay products to lab frame.
430 DO 400 J=1,4
431 400 P(N+ND,J)=PV(ND,J)
432 DO 430 IL=ND-1,1,-1
433 DO 410 J=1,3
434 410 BE(J)=PV(IL,J)/PV(IL,4)
435 GA=PV(IL,4)/PV(IL,5)
436 DO 430 I=N+IL,N+ND
437 BEP=BE(1)*P(I,1)+BE(2)*P(I,2)+BE(3)*P(I,3)
438 DO 420 J=1,3
439 420 P(I,J)=P(I,J)+GA*(GA*BEP/(1.+GA)+P(I,4))*BE(J)
440 430 P(I,4)=GA*(P(I,4)+BEP)
441
442C...Matrix elements for omega and phi decays.
443 IF(MMAT.EQ.1) THEN
444 WT=(P(N+1,5)*P(N+2,5)*P(N+3,5))**2-(P(N+1,5)*FOUR(N+2,N+3))**2
445 & -(P(N+2,5)*FOUR(N+1,N+3))**2-(P(N+3,5)*FOUR(N+1,N+2))**2
446 & +2.*FOUR(N+1,N+2)*FOUR(N+1,N+3)*FOUR(N+2,N+3)
447 IF(MAX(WT*WTCOR(9)/P(IP,5)**6,0.001).LT.RLU_HIJING(0)) GOTO 310
448
449C...Matrix elements for pi0 or eta Dalitz decay to gamma e+ e-.
450 ELSEIF(MMAT.EQ.2) THEN
451 FOUR12=FOUR(N+1,N+2)
452 FOUR13=FOUR(N+1,N+3)
453 FOUR23=0.5*PMST-0.25*PMES
454 WT=(PMST-0.5*PMES)*(FOUR12**2+FOUR13**2)+
455 & PMES*(FOUR12*FOUR13+FOUR12**2+FOUR13**2)
456 IF(WT.LT.RLU_HIJING(0)*0.25*PMST*(P(IP,5)**2-PMST)**2) GOTO 370
457
458C...Matrix element for S0 -> S1 + V1 -> S1 + S2 + S3 (S scalar,
459C...V vector), of form cos**2(theta02) in V1 rest frame.
460 ELSEIF(MMAT.EQ.3.AND.NM.EQ.2) THEN
461 IF((P(IP,5)**2*FOUR(IM,N+1)-FOUR(IP,IM)*FOUR(IP,N+1))**2.LE.
462 & RLU_HIJING(0)*(FOUR(IP,IM)**2-(P(IP,5)*P(IM,5))**2)
463 $ *(FOUR(IP,N+1)**2-(P(IP,5)*P(N+1,5))**2)) GOTO 370
464
465C...Matrix element for "onium" -> g + g + g or gamma + g + g.
466 ELSEIF(MMAT.EQ.4) THEN
467 HX1=2.*FOUR(IP,N+1)/P(IP,5)**2
468 HX2=2.*FOUR(IP,N+2)/P(IP,5)**2
469 HX3=2.*FOUR(IP,N+3)/P(IP,5)**2
470 WT=((1.-HX1)/(HX2*HX3))**2+((1.-HX2)/(HX1*HX3))**2+
471 & ((1.-HX3)/(HX1*HX2))**2
472 IF(WT.LT.2.*RLU_HIJING(0)) GOTO 310
473 IF(K(IP+1,2).EQ.22.AND.(1.-HX1)*P(IP,5)**2.LT.4.*PARJ(32)**2)
474 & GOTO 310
475
476C...Effective matrix element for nu spectrum in tau -> nu + hadrons.
477 ELSEIF(MMAT.EQ.41) THEN
478 HX1=2.*FOUR(IP,N+1)/P(IP,5)**2
479 IF(8.*HX1*(3.-2.*HX1)/9..LT.RLU_HIJING(0)) GOTO 310
480
481C...Matrix elements for weak decays (only semileptonic for c and b)
482 ELSEIF(MMAT.GE.42.AND.MMAT.LE.44.AND.ND.EQ.3) THEN
483 IF(MBST.EQ.0) WT=FOUR(IP,N+1)*FOUR(N+2,N+3)
484 IF(MBST.EQ.1) WT=P(IP,5)*P(N+1,4)*FOUR(N+2,N+3)
485 IF(WT.LT.RLU_HIJING(0)*P(IP,5)*PV(1,5)**3/WTCOR(10)) GOTO 310
486 ELSEIF(MMAT.GE.42.AND.MMAT.LE.44) THEN
487 DO 440 J=1,4
488 P(N+NP+1,J)=0.
489 DO 440 IS=N+3,N+NP
490 440 P(N+NP+1,J)=P(N+NP+1,J)+P(IS,J)
491 IF(MBST.EQ.0) WT=FOUR(IP,N+1)*FOUR(N+2,N+NP+1)
492 IF(MBST.EQ.1) WT=P(IP,5)*P(N+1,4)*FOUR(N+2,N+NP+1)
493 IF(WT.LT.RLU_HIJING(0)*P(IP,5)*PV(1,5)**3/WTCOR(10)) GOTO 310
494
495C...Angular distribution in W decay.
496 ELSEIF(MMAT.EQ.46.AND.MSGN.NE.0) THEN
497 IF(MSGN.GT.0) WT=FOUR(IM,N+1)*FOUR(N+2,IP+1)
498 IF(MSGN.LT.0) WT=FOUR(IM,N+2)*FOUR(N+1,IP+1)
499 IF(WT.LT.RLU_HIJING(0)*P(IM,5)**4/WTCOR(10)) GOTO 370
500 ENDIF
501
502C...Scale back energy and reattach spectator.
503 IF(MREM.EQ.1) THEN
504 DO 450 J=1,5
505 450 PV(1,J)=PV(1,J)/(1.-PQT)
506 ND=ND+1
507 MREM=0
508 ENDIF
509
510C...Low invariant mass for system with spectator quark gives particle,
511C...not two jets. Readjust momenta accordingly.
512 IF((MMAT.EQ.31.OR.MMAT.EQ.45).AND.ND.EQ.3) THEN
513 MSTJ(93)=1
514 PM2=ULMASS_HIJING(K(N+2,2))
515 MSTJ(93)=1
516 PM3=ULMASS_HIJING(K(N+3,2))
517 IF(P(N+2,5)**2+P(N+3,5)**2+2.*FOUR(N+2,N+3).GE.
518 & (PARJ(32)+PM2+PM3)**2) GOTO 510
519 K(N+2,1)=1
520 KFTEMP=K(N+2,2)
521 CALL LUKFDI_HIJING(KFTEMP,K(N+3,2),KFLDMP,K(N+2,2))
522 IF(K(N+2,2).EQ.0) GOTO 150
523 P(N+2,5)=ULMASS_HIJING(K(N+2,2))
524 PS=P(N+1,5)+P(N+2,5)
525 PV(2,5)=P(N+2,5)
526 MMAT=0
527 ND=2
528 GOTO 370
529 ELSEIF(MMAT.EQ.44) THEN
530 MSTJ(93)=1
531 PM3=ULMASS_HIJING(K(N+3,2))
532 MSTJ(93)=1
533 PM4=ULMASS_HIJING(K(N+4,2))
534 IF(P(N+3,5)**2+P(N+4,5)**2+2.*FOUR(N+3,N+4).GE.
535 & (PARJ(32)+PM3+PM4)**2) GOTO 480
536 K(N+3,1)=1
537 KFTEMP=K(N+3,2)
538 CALL LUKFDI_HIJING(KFTEMP,K(N+4,2),KFLDMP,K(N+3,2))
539 IF(K(N+3,2).EQ.0) GOTO 150
540 P(N+3,5)=ULMASS_HIJING(K(N+3,2))
541 DO 460 J=1,3
542 460 P(N+3,J)=P(N+3,J)+P(N+4,J)
543 P(N+3,4)=SQRT(P(N+3,1)**2+P(N+3,2)**2+P(N+3,3)**2+P(N+3,5)**2)
544 HA=P(N+1,4)**2-P(N+2,4)**2
545 HB=HA-(P(N+1,5)**2-P(N+2,5)**2)
546 HC=(P(N+1,1)-P(N+2,1))**2+(P(N+1,2)-P(N+2,2))**2+
547 & (P(N+1,3)-P(N+2,3))**2
548 HD=(PV(1,4)-P(N+3,4))**2
549 HE=HA**2-2.*HD*(P(N+1,4)**2+P(N+2,4)**2)+HD**2
550 HF=HD*HC-HB**2
551 HG=HD*HC-HA*HB
552 HH=(SQRT(HG**2+HE*HF)-HG)/(2.*HF)
553 DO 470 J=1,3
554 PCOR=HH*(P(N+1,J)-P(N+2,J))
555 P(N+1,J)=P(N+1,J)+PCOR
556 470 P(N+2,J)=P(N+2,J)-PCOR
557 P(N+1,4)=SQRT(P(N+1,1)**2+P(N+1,2)**2+P(N+1,3)**2+P(N+1,5)**2)
558 P(N+2,4)=SQRT(P(N+2,1)**2+P(N+2,2)**2+P(N+2,3)**2+P(N+2,5)**2)
559 ND=ND-1
560 ENDIF
561
562C...Check invariant mass of W jets. May give one particle or start over.
563 480 IF(MMAT.GE.42.AND.MMAT.LE.44.AND.IABS(K(N+1,2)).LT.10) THEN
564 PMR=SQRT(MAX(0.,P(N+1,5)**2+P(N+2,5)**2+2.*FOUR(N+1,N+2)))
565 MSTJ(93)=1
566 PM1=ULMASS_HIJING(K(N+1,2))
567 MSTJ(93)=1
568 PM2=ULMASS_HIJING(K(N+2,2))
569 IF(PMR.GT.PARJ(32)+PM1+PM2) GOTO 490
570 KFLDUM=INT(1.5+RLU_HIJING(0))
571 CALL LUKFDI_HIJING(K(N+1,2),-ISIGN(KFLDUM,K(N+1,2)),KFLDMP,KF1)
572 CALL LUKFDI_HIJING(K(N+2,2),-ISIGN(KFLDUM,K(N+2,2)),KFLDMP,KF2)
573 IF(KF1.EQ.0.OR.KF2.EQ.0) GOTO 150
574 PSM=ULMASS_HIJING(KF1)+ULMASS_HIJING(KF2)
575 IF(MMAT.EQ.42.AND.PMR.GT.PARJ(64)+PSM) GOTO 490
576 IF(MMAT.GE.43.AND.PMR.GT.0.2*PARJ(32)+PSM) GOTO 490
577 IF(ND.EQ.4.OR.KFA.EQ.15) GOTO 150
578 K(N+1,1)=1
579 KFTEMP=K(N+1,2)
580 CALL LUKFDI_HIJING(KFTEMP,K(N+2,2),KFLDMP,K(N+1,2))
581 IF(K(N+1,2).EQ.0) GOTO 150
582 P(N+1,5)=ULMASS_HIJING(K(N+1,2))
583 K(N+2,2)=K(N+3,2)
584 P(N+2,5)=P(N+3,5)
585 PS=P(N+1,5)+P(N+2,5)
586 PV(2,5)=P(N+3,5)
587 MMAT=0
588 ND=2
589 GOTO 370
590 ENDIF
591
592C...Phase space decay of partons from W decay.
593 490 IF(MMAT.EQ.42.AND.IABS(K(N+1,2)).LT.10) THEN
594 KFLO(1)=K(N+1,2)
595 KFLO(2)=K(N+2,2)
596 K(N+1,1)=K(N+3,1)
597 K(N+1,2)=K(N+3,2)
598 DO 500 J=1,5
599 PV(1,J)=P(N+1,J)+P(N+2,J)
600 500 P(N+1,J)=P(N+3,J)
601 PV(1,5)=PMR
602 N=N+1
603 NP=0
604 NQ=2
605 PS=0.
606 MSTJ(93)=2
607 PSQ=ULMASS_HIJING(KFLO(1))
608 MSTJ(93)=2
609 PSQ=PSQ+ULMASS_HIJING(KFLO(2))
610 MMAT=11
611 GOTO 180
612 ENDIF
613
614C...Boost back for rapidly moving particle.
615 510 N=N+ND
616 IF(MBST.EQ.1) THEN
617 DO 520 J=1,3
618 520 BE(J)=P(IP,J)/P(IP,4)
619 GA=P(IP,4)/P(IP,5)
620 DO 540 I=NSAV+1,N
621 BEP=BE(1)*P(I,1)+BE(2)*P(I,2)+BE(3)*P(I,3)
622 DO 530 J=1,3
623 530 P(I,J)=P(I,J)+GA*(GA*BEP/(1.+GA)+P(I,4))*BE(J)
624 540 P(I,4)=GA*(P(I,4)+BEP)
625 ENDIF
626
627C...Fill in position of decay vertex.
628 DO 560 I=NSAV+1,N
629 DO 550 J=1,4
630 550 V(I,J)=VDCY(J)
631 560 V(I,5)=0.
632
633C...Set up for parton shower evolution from jets.
634 IF(MSTJ(23).GE.1.AND.MMAT.EQ.4.AND.K(NSAV+1,2).EQ.21) THEN
635 K(NSAV+1,1)=3
636 K(NSAV+2,1)=3
637 K(NSAV+3,1)=3
638 K(NSAV+1,4)=MSTU(5)*(NSAV+2)
639 K(NSAV+1,5)=MSTU(5)*(NSAV+3)
640 K(NSAV+2,4)=MSTU(5)*(NSAV+3)
641 K(NSAV+2,5)=MSTU(5)*(NSAV+1)
642 K(NSAV+3,4)=MSTU(5)*(NSAV+1)
643 K(NSAV+3,5)=MSTU(5)*(NSAV+2)
644 MSTJ(92)=-(NSAV+1)
645 ELSEIF(MSTJ(23).GE.1.AND.MMAT.EQ.4) THEN
646 K(NSAV+2,1)=3
647 K(NSAV+3,1)=3
648 K(NSAV+2,4)=MSTU(5)*(NSAV+3)
649 K(NSAV+2,5)=MSTU(5)*(NSAV+3)
650 K(NSAV+3,4)=MSTU(5)*(NSAV+2)
651 K(NSAV+3,5)=MSTU(5)*(NSAV+2)
652 MSTJ(92)=NSAV+2
653 ELSEIF(MSTJ(23).GE.1.AND.(MMAT.EQ.32.OR.MMAT.EQ.44.OR.MMAT.EQ.46).
654 &AND.IABS(K(NSAV+1,2)).LE.10.AND.IABS(K(NSAV+2,2)).LE.10) THEN
655 K(NSAV+1,1)=3
656 K(NSAV+2,1)=3
657 K(NSAV+1,4)=MSTU(5)*(NSAV+2)
658 K(NSAV+1,5)=MSTU(5)*(NSAV+2)
659 K(NSAV+2,4)=MSTU(5)*(NSAV+1)
660 K(NSAV+2,5)=MSTU(5)*(NSAV+1)
661 MSTJ(92)=NSAV+1
662 ELSEIF(MSTJ(23).GE.1.AND.MMAT.EQ.33.AND.IABS(K(NSAV+2,2)).EQ.21)
663 &THEN
664 K(NSAV+1,1)=3
665 K(NSAV+2,1)=3
666 K(NSAV+3,1)=3
667 KCP=LUCOMP_HIJING(K(NSAV+1,2))
668 KQP=KCHG(KCP,2)*ISIGN(1,K(NSAV+1,2))
669 JCON=4
670 IF(KQP.LT.0) JCON=5
671 K(NSAV+1,JCON)=MSTU(5)*(NSAV+2)
672 K(NSAV+2,9-JCON)=MSTU(5)*(NSAV+1)
673 K(NSAV+2,JCON)=MSTU(5)*(NSAV+3)
674 K(NSAV+3,9-JCON)=MSTU(5)*(NSAV+2)
675 MSTJ(92)=NSAV+1
676 ELSEIF(MSTJ(23).GE.1.AND.MMAT.EQ.33) THEN
677 K(NSAV+1,1)=3
678 K(NSAV+3,1)=3
679 K(NSAV+1,4)=MSTU(5)*(NSAV+3)
680 K(NSAV+1,5)=MSTU(5)*(NSAV+3)
681 K(NSAV+3,4)=MSTU(5)*(NSAV+1)
682 K(NSAV+3,5)=MSTU(5)*(NSAV+1)
683 MSTJ(92)=NSAV+1
684 ENDIF
685
686C...Mark decayed particle.
687 IF(K(IP,1).EQ.5) K(IP,1)=15
688 IF(K(IP,1).LE.10) K(IP,1)=11
689 K(IP,4)=NSAV+1
690 K(IP,5)=N
691
692 RETURN
693 END