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Syntax problems on HP-UX corrected
[u/mrichter/AliRoot.git] / PHOS / shaker / lustrf.f
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fe4da5cc 1*CMZ : 17/07/98 15.44.31 by Federico Carminati
2*-- Author :
3C*********************************************************************
4
5 SUBROUTINE LUSTRF(IP)
6C...Purpose: to handle the fragmentation of an arbitrary colour singlet
7C...jet system according to the Lund string fragmentation model.
8 IMPLICIT DOUBLE PRECISION(D)
9*KEEP,LUJETS.
10 COMMON /LUJETS/ N,K(200000,5),P(200000,5),V(200000,5)
11 SAVE /LUJETS/
12*KEEP,LUDAT1.
13 COMMON /LUDAT1/ MSTU(200),PARU(200),MSTJ(200),PARJ(200)
14 SAVE /LUDAT1/
15*KEEP,LUDAT2.
16 COMMON /LUDAT2/ KCHG(500,3),PMAS(500,4),PARF(2000),VCKM(4,4)
17 SAVE /LUDAT2/
18*KEND.
19 DIMENSION DPS(5),KFL(3),PMQ(3),PX(3),PY(3),GAM(3),IE(2),PR(2),
20 &IN(9),DHM(4),DHG(4),DP(5,5),IRANK(2),MJU(4),IJU(3),PJU(5,5),
21 &TJU(5),KFJH(2),NJS(2),KFJS(2),PJS(4,5)
22
23C...Function: four-product of two vectors.
24 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)
25 DFOUR(I,J)=DP(I,4)*DP(J,4)-DP(I,1)*DP(J,1)-DP(I,2)*DP(J,2)-
26 &DP(I,3)*DP(J,3)
27
28C...Reset counters. Identify parton system.
29 MSTJ(91)=0
30 NSAV=N
31 NP=0
32 KQSUM=0
33 DO 100 J=1,5
34 100 DPS(J)=0.
35 MJU(1)=0
36 MJU(2)=0
37 I=IP-1
38 110 I=I+1
39 IF(I.GT.MIN(N,MSTU(4)-MSTU(32))) THEN
40 CALL LUERRM(12,'(LUSTRF:) failed to reconstruct jet system')
41 IF(MSTU(21).GE.1) RETURN
42 ENDIF
43 IF(K(I,1).NE.1.AND.K(I,1).NE.2.AND.K(I,1).NE.41) GOTO 110
44 KC=LUCOMP(K(I,2))
45 IF(KC.EQ.0) GOTO 110
46 KQ=KCHG(KC,2)*ISIGN(1,K(I,2))
47 IF(KQ.EQ.0) GOTO 110
48 IF(N+5*NP+11.GT.MSTU(4)-MSTU(32)-5) THEN
49 CALL LUERRM(11,'(LUSTRF:) no more memory left in LUJETS')
50 IF(MSTU(21).GE.1) RETURN
51 ENDIF
52
53C...Take copy of partons to be considered. Check flavour sum.
54 NP=NP+1
55 DO 120 J=1,5
56 K(N+NP,J)=K(I,J)
57 P(N+NP,J)=P(I,J)
58 120 DPS(J)=DPS(J)+P(I,J)
59 K(N+NP,3)=I
60 IF(P(N+NP,4)**2.LT.P(N+NP,1)**2+P(N+NP,2)**2+P(N+NP,3)**2) THEN
61 P(N+NP,4)=SQRT(P(N+NP,1)**2+P(N+NP,2)**2+P(N+NP,3)**2+
62 & P(N+NP,5)**2)
63 DPS(4)=DPS(4)+MAX(0.,P(N+NP,4)-P(I,4))
64 ENDIF
65 IF(KQ.NE.2) KQSUM=KQSUM+KQ
66 IF(K(I,1).EQ.41) THEN
67 KQSUM=KQSUM+2*KQ
68 IF(KQSUM.EQ.KQ) MJU(1)=N+NP
69 IF(KQSUM.NE.KQ) MJU(2)=N+NP
70 ENDIF
71 IF(K(I,1).EQ.2.OR.K(I,1).EQ.41) GOTO 110
72 IF(KQSUM.NE.0) THEN
73 CALL LUERRM(12,'(LUSTRF:) unphysical flavour combination')
74 IF(MSTU(21).GE.1) RETURN
75 ENDIF
76
77C...Boost copied system to CM frame (for better numerical precision).
78 MSTU(33)=1
79 CALL LUDBRB(N+1,N+NP,0.,0.,-DPS(1)/DPS(4),-DPS(2)/DPS(4),
80 &-DPS(3)/DPS(4))
81
82C...Search for very nearby partons that may be recombined.
83 NTRYR=0
84 PARU12=PARU(12)
85 PARU13=PARU(13)
86 MJU(3)=MJU(1)
87 MJU(4)=MJU(2)
88 NR=NP
89 130 IF(NR.GE.3) THEN
90 PDRMIN=2.*PARU12
91 DO 140 I=N+1,N+NR
92 IF(I.EQ.N+NR.AND.IABS(K(N+1,2)).NE.21) GOTO 140
93 I1=I+1
94 IF(I.EQ.N+NR) I1=N+1
95 IF(K(I,1).EQ.41.OR.K(I1,1).EQ.41) GOTO 140
96 IF(MJU(1).NE.0.AND.I1.LT.MJU(1).AND.IABS(K(I1,2)).NE.21)
97 & GOTO 140
98 IF(MJU(2).NE.0.AND.I.GT.MJU(2).AND.IABS(K(I,2)).NE.21) GOTO 140
99 PAP=SQRT((P(I,1)**2+P(I,2)**2+P(I,3)**2)*(P(I1,1)**2+
100 & P(I1,2)**2+P(I1,3)**2))
101 PVP=P(I,1)*P(I1,1)+P(I,2)*P(I1,2)+P(I,3)*P(I1,3)
102 PDR=4.*(PAP-PVP)**2/(PARU13**2*PAP+2.*(PAP-PVP))
103 IF(PDR.LT.PDRMIN) THEN
104 IR=I
105 PDRMIN=PDR
106 ENDIF
107 140 CONTINUE
108
109C...Recombine very nearby partons to avoid machine precision problems.
110 IF(PDRMIN.LT.PARU12.AND.IR.EQ.N+NR) THEN
111 DO 150 J=1,4
112 150 P(N+1,J)=P(N+1,J)+P(N+NR,J)
113 P(N+1,5)=SQRT(MAX(0.,P(N+1,4)**2-P(N+1,1)**2-P(N+1,2)**2-
114 & P(N+1,3)**2))
115 NR=NR-1
116 GOTO 130
117 ELSEIF(PDRMIN.LT.PARU12) THEN
118 DO 160 J=1,4
119 160 P(IR,J)=P(IR,J)+P(IR+1,J)
120 P(IR,5)=SQRT(MAX(0.,P(IR,4)**2-P(IR,1)**2-P(IR,2)**2-
121 & P(IR,3)**2))
122 DO 170 I=IR+1,N+NR-1
123 K(I,2)=K(I+1,2)
124 DO 170 J=1,5
125 170 P(I,J)=P(I+1,J)
126 IF(IR.EQ.N+NR-1) K(IR,2)=K(N+NR,2)
127 NR=NR-1
128 IF(MJU(1).GT.IR) MJU(1)=MJU(1)-1
129 IF(MJU(2).GT.IR) MJU(2)=MJU(2)-1
130 GOTO 130
131 ENDIF
132 ENDIF
133 NTRYR=NTRYR+1
134
135C...Reset particle counter. Skip ahead if no junctions are present;
136C...this is usually the case!
137 NRS=MAX(5*NR+11,NP)
138 NTRY=0
139 180 NTRY=NTRY+1
140 IF(NTRY.GT.100.AND.NTRYR.LE.4) THEN
141 PARU12=4.*PARU12
142 PARU13=2.*PARU13
143 GOTO 130
144 ELSEIF(NTRY.GT.100) THEN
145 CALL LUERRM(14,'(LUSTRF:) caught in infinite loop')
146 IF(MSTU(21).GE.1) RETURN
147 ENDIF
148 I=N+NRS
149 IF(MJU(1).EQ.0.AND.MJU(2).EQ.0) GOTO 500
150 DO 490 JT=1,2
151 NJS(JT)=0
152 IF(MJU(JT).EQ.0) GOTO 490
153 JS=3-2*JT
154
155C...Find and sum up momentum on three sides of junction. Check flavours.
156 DO 190 IU=1,3
157 IJU(IU)=0
158 DO 190 J=1,5
159 190 PJU(IU,J)=0.
160 IU=0
161 DO 200 I1=N+1+(JT-1)*(NR-1),N+NR+(JT-1)*(1-NR),JS
162 IF(K(I1,2).NE.21.AND.IU.LE.2) THEN
163 IU=IU+1
164 IJU(IU)=I1
165 ENDIF
166 DO 200 J=1,4
167 200 PJU(IU,J)=PJU(IU,J)+P(I1,J)
168 DO 210 IU=1,3
169 210 PJU(IU,5)=SQRT(PJU(IU,1)**2+PJU(IU,2)**2+PJU(IU,3)**2)
170 IF(K(IJU(3),2)/100.NE.10*K(IJU(1),2)+K(IJU(2),2).AND.
171 &K(IJU(3),2)/100.NE.10*K(IJU(2),2)+K(IJU(1),2)) THEN
172 CALL LUERRM(12,'(LUSTRF:) unphysical flavour combination')
173 IF(MSTU(21).GE.1) RETURN
174 ENDIF
175
176C...Calculate (approximate) boost to rest frame of junction.
177 T12=(PJU(1,1)*PJU(2,1)+PJU(1,2)*PJU(2,2)+PJU(1,3)*PJU(2,3))/
178 &(PJU(1,5)*PJU(2,5))
179 T13=(PJU(1,1)*PJU(3,1)+PJU(1,2)*PJU(3,2)+PJU(1,3)*PJU(3,3))/
180 &(PJU(1,5)*PJU(3,5))
181 T23=(PJU(2,1)*PJU(3,1)+PJU(2,2)*PJU(3,2)+PJU(2,3)*PJU(3,3))/
182 &(PJU(2,5)*PJU(3,5))
183 T11=SQRT((2./3.)*(1.-T12)*(1.-T13)/(1.-T23))
184 T22=SQRT((2./3.)*(1.-T12)*(1.-T23)/(1.-T13))
185 TSQ=SQRT((2.*T11*T22+T12-1.)*(1.+T12))
186 T1F=(TSQ-T22*(1.+T12))/(1.-T12**2)
187 T2F=(TSQ-T11*(1.+T12))/(1.-T12**2)
188 DO 220 J=1,3
189 220 TJU(J)=-(T1F*PJU(1,J)/PJU(1,5)+T2F*PJU(2,J)/PJU(2,5))
190 TJU(4)=SQRT(1.+TJU(1)**2+TJU(2)**2+TJU(3)**2)
191 DO 230 IU=1,3
192 230 PJU(IU,5)=TJU(4)*PJU(IU,4)-TJU(1)*PJU(IU,1)-TJU(2)*PJU(IU,2)-
193 &TJU(3)*PJU(IU,3)
194
195C...Put junction at rest if motion could give inconsistencies.
196 IF(PJU(1,5)+PJU(2,5).GT.PJU(1,4)+PJU(2,4)) THEN
197 DO 240 J=1,3
198 240 TJU(J)=0.
199 TJU(4)=1.
200 PJU(1,5)=PJU(1,4)
201 PJU(2,5)=PJU(2,4)
202 PJU(3,5)=PJU(3,4)
203 ENDIF
204
205C...Start preparing for fragmentation of two strings from junction.
206 ISTA=I
207 DO 470 IU=1,2
208 NS=IJU(IU+1)-IJU(IU)
209
210C...Junction strings: find longitudinal string directions.
211 DO 260 IS=1,NS
212 IS1=IJU(IU)+IS-1
213 IS2=IJU(IU)+IS
214 DO 250 J=1,5
215 DP(1,J)=0.5*P(IS1,J)
216 IF(IS.EQ.1) DP(1,J)=P(IS1,J)
217 DP(2,J)=0.5*P(IS2,J)
218 250 IF(IS.EQ.NS) DP(2,J)=-PJU(IU,J)
219 IF(IS.EQ.NS) DP(2,4)=SQRT(PJU(IU,1)**2+PJU(IU,2)**2+PJU(IU,3)**2)
220 IF(IS.EQ.NS) DP(2,5)=0.
221 DP(3,5)=DFOUR(1,1)
222 DP(4,5)=DFOUR(2,2)
223 DHKC=DFOUR(1,2)
224 IF(DP(3,5)+2.*DHKC+DP(4,5).LE.0.) THEN
225 DP(1,4)=SQRT(DP(1,1)**2+DP(1,2)**2+DP(1,3)**2)
226 DP(2,4)=SQRT(DP(2,1)**2+DP(2,2)**2+DP(2,3)**2)
227 DP(3,5)=0D0
228 DP(4,5)=0D0
229 DHKC=DFOUR(1,2)
230 ENDIF
231 DHKS=SQRT(DHKC**2-DP(3,5)*DP(4,5))
232 DHK1=0.5*((DP(4,5)+DHKC)/DHKS-1.)
233 DHK2=0.5*((DP(3,5)+DHKC)/DHKS-1.)
234 IN1=N+NR+4*IS-3
235 P(IN1,5)=SQRT(DP(3,5)+2.*DHKC+DP(4,5))
236 DO 260 J=1,4
237 P(IN1,J)=(1.+DHK1)*DP(1,J)-DHK2*DP(2,J)
238 260 P(IN1+1,J)=(1.+DHK2)*DP(2,J)-DHK1*DP(1,J)
239
240C...Junction strings: initialize flavour, momentum and starting pos.
241 ISAV=I
242 270 NTRY=NTRY+1
243 IF(NTRY.GT.100.AND.NTRYR.LE.4) THEN
244 PARU12=4.*PARU12
245 PARU13=2.*PARU13
246 GOTO 130
247 ELSEIF(NTRY.GT.100) THEN
248 CALL LUERRM(14,'(LUSTRF:) caught in infinite loop')
249 IF(MSTU(21).GE.1) RETURN
250 ENDIF
251 I=ISAV
252 IRANKJ=0
253 IE(1)=K(N+1+(JT/2)*(NP-1),3)
254 IN(4)=N+NR+1
255 IN(5)=IN(4)+1
256 IN(6)=N+NR+4*NS+1
257 DO 280 JQ=1,2
258 DO 280 IN1=N+NR+2+JQ,N+NR+4*NS-2+JQ,4
259 P(IN1,1)=2-JQ
260 P(IN1,2)=JQ-1
261 280 P(IN1,3)=1.
262 KFL(1)=K(IJU(IU),2)
263 PX(1)=0.
264 PY(1)=0.
265 GAM(1)=0.
266 DO 290 J=1,5
267 290 PJU(IU+3,J)=0.
268
269C...Junction strings: find initial transverse directions.
270 DO 300 J=1,4
271 DP(1,J)=P(IN(4),J)
272 DP(2,J)=P(IN(4)+1,J)
273 DP(3,J)=0.
274 300 DP(4,J)=0.
275 DP(1,4)=SQRT(DP(1,1)**2+DP(1,2)**2+DP(1,3)**2)
276 DP(2,4)=SQRT(DP(2,1)**2+DP(2,2)**2+DP(2,3)**2)
277 DP(5,1)=DP(1,1)/DP(1,4)-DP(2,1)/DP(2,4)
278 DP(5,2)=DP(1,2)/DP(1,4)-DP(2,2)/DP(2,4)
279 DP(5,3)=DP(1,3)/DP(1,4)-DP(2,3)/DP(2,4)
280 IF(DP(5,1)**2.LE.DP(5,2)**2+DP(5,3)**2) DP(3,1)=1.
281 IF(DP(5,1)**2.GT.DP(5,2)**2+DP(5,3)**2) DP(3,3)=1.
282 IF(DP(5,2)**2.LE.DP(5,1)**2+DP(5,3)**2) DP(4,2)=1.
283 IF(DP(5,2)**2.GT.DP(5,1)**2+DP(5,3)**2) DP(4,3)=1.
284 DHC12=DFOUR(1,2)
285 DHCX1=DFOUR(3,1)/DHC12
286 DHCX2=DFOUR(3,2)/DHC12
287 DHCXX=1D0/SQRT(1D0+2D0*DHCX1*DHCX2*DHC12)
288 DHCY1=DFOUR(4,1)/DHC12
289 DHCY2=DFOUR(4,2)/DHC12
290 DHCYX=DHCXX*(DHCX1*DHCY2+DHCX2*DHCY1)*DHC12
291 DHCYY=1D0/SQRT(1D0+2D0*DHCY1*DHCY2*DHC12-DHCYX**2)
292 DO 310 J=1,4
293 DP(3,J)=DHCXX*(DP(3,J)-DHCX2*DP(1,J)-DHCX1*DP(2,J))
294 P(IN(6),J)=DP(3,J)
295 310 P(IN(6)+1,J)=DHCYY*(DP(4,J)-DHCY2*DP(1,J)-DHCY1*DP(2,J)-
296 &DHCYX*DP(3,J))
297
298C...Junction strings: produce new particle, origin.
299 320 I=I+1
300 IF(2*I-NSAV.GE.MSTU(4)-MSTU(32)-5) THEN
301 CALL LUERRM(11,'(LUSTRF:) no more memory left in LUJETS')
302 IF(MSTU(21).GE.1) RETURN
303 ENDIF
304 IRANKJ=IRANKJ+1
305 K(I,1)=1
306 K(I,3)=IE(1)
307 K(I,4)=0
308 K(I,5)=0
309
310C...Junction strings: generate flavour, hadron, pT, z and Gamma.
311 330 CALL LUKFDI(KFL(1),0,KFL(3),K(I,2))
312 IF(K(I,2).EQ.0) GOTO 270
313 IF(MSTJ(12).GE.3.AND.IRANKJ.EQ.1.AND.IABS(KFL(1)).LE.10.AND.
314 &IABS(KFL(3)).GT.10) THEN
315 IF(RLU(0).GT.PARJ(19)) GOTO 330
316 ENDIF
317 P(I,5)=ULMASS(K(I,2))
318 CALL LUPTDI(KFL(1),PX(3),PY(3))
319 PR(1)=P(I,5)**2+(PX(1)+PX(3))**2+(PY(1)+PY(3))**2
320 CALL LUZDIS(KFL(1),KFL(3),PR(1),Z)
321 GAM(3)=(1.-Z)*(GAM(1)+PR(1)/Z)
322 DO 340 J=1,3
323 340 IN(J)=IN(3+J)
324
325C...Junction strings: stepping within or from 'low' string region easy.
326 IF(IN(1)+1.EQ.IN(2).AND.Z*P(IN(1)+2,3)*P(IN(2)+2,3)*
327 &P(IN(1),5)**2.GE.PR(1)) THEN
328 P(IN(1)+2,4)=Z*P(IN(1)+2,3)
329 P(IN(2)+2,4)=PR(1)/(P(IN(1)+2,4)*P(IN(1),5)**2)
330 DO 350 J=1,4
331 350 P(I,J)=(PX(1)+PX(3))*P(IN(3),J)+(PY(1)+PY(3))*P(IN(3)+1,J)
332 GOTO 420
333 ELSEIF(IN(1)+1.EQ.IN(2)) THEN
334 P(IN(2)+2,4)=P(IN(2)+2,3)
335 P(IN(2)+2,1)=1.
336 IN(2)=IN(2)+4
337 IF(IN(2).GT.N+NR+4*NS) GOTO 270
338 IF(FOUR(IN(1),IN(2)).LE.1E-2) THEN
339 P(IN(1)+2,4)=P(IN(1)+2,3)
340 P(IN(1)+2,1)=0.
341 IN(1)=IN(1)+4
342 ENDIF
343 ENDIF
344
345C...Junction strings: find new transverse directions.
346 360 IF(IN(1).GT.N+NR+4*NS.OR.IN(2).GT.N+NR+4*NS.OR.
347 &IN(1).GT.IN(2)) GOTO 270
348 IF(IN(1).NE.IN(4).OR.IN(2).NE.IN(5)) THEN
349 DO 370 J=1,4
350 DP(1,J)=P(IN(1),J)
351 DP(2,J)=P(IN(2),J)
352 DP(3,J)=0.
353 370 DP(4,J)=0.
354 DP(1,4)=SQRT(DP(1,1)**2+DP(1,2)**2+DP(1,3)**2)
355 DP(2,4)=SQRT(DP(2,1)**2+DP(2,2)**2+DP(2,3)**2)
356 DHC12=DFOUR(1,2)
357 IF(DHC12.LE.1E-2) THEN
358 P(IN(1)+2,4)=P(IN(1)+2,3)
359 P(IN(1)+2,1)=0.
360 IN(1)=IN(1)+4
361 GOTO 360
362 ENDIF
363 IN(3)=N+NR+4*NS+5
364 DP(5,1)=DP(1,1)/DP(1,4)-DP(2,1)/DP(2,4)
365 DP(5,2)=DP(1,2)/DP(1,4)-DP(2,2)/DP(2,4)
366 DP(5,3)=DP(1,3)/DP(1,4)-DP(2,3)/DP(2,4)
367 IF(DP(5,1)**2.LE.DP(5,2)**2+DP(5,3)**2) DP(3,1)=1.
368 IF(DP(5,1)**2.GT.DP(5,2)**2+DP(5,3)**2) DP(3,3)=1.
369 IF(DP(5,2)**2.LE.DP(5,1)**2+DP(5,3)**2) DP(4,2)=1.
370 IF(DP(5,2)**2.GT.DP(5,1)**2+DP(5,3)**2) DP(4,3)=1.
371 DHCX1=DFOUR(3,1)/DHC12
372 DHCX2=DFOUR(3,2)/DHC12
373 DHCXX=1D0/SQRT(1D0+2D0*DHCX1*DHCX2*DHC12)
374 DHCY1=DFOUR(4,1)/DHC12
375 DHCY2=DFOUR(4,2)/DHC12
376 DHCYX=DHCXX*(DHCX1*DHCY2+DHCX2*DHCY1)*DHC12
377 DHCYY=1D0/SQRT(1D0+2D0*DHCY1*DHCY2*DHC12-DHCYX**2)
378 DO 380 J=1,4
379 DP(3,J)=DHCXX*(DP(3,J)-DHCX2*DP(1,J)-DHCX1*DP(2,J))
380 P(IN(3),J)=DP(3,J)
381 380 P(IN(3)+1,J)=DHCYY*(DP(4,J)-DHCY2*DP(1,J)-DHCY1*DP(2,J)-
382 & DHCYX*DP(3,J))
383C...Express pT with respect to new axes, if sensible.
384 PXP=-(PX(3)*FOUR(IN(6),IN(3))+PY(3)*FOUR(IN(6)+1,IN(3)))
385 PYP=-(PX(3)*FOUR(IN(6),IN(3)+1)+PY(3)*FOUR(IN(6)+1,IN(3)+1))
386 IF(ABS(PXP**2+PYP**2-PX(3)**2-PY(3)**2).LT.0.01) THEN
387 PX(3)=PXP
388 PY(3)=PYP
389 ENDIF
390 ENDIF
391
392C...Junction strings: sum up known four-momentum, coefficients for m2.
393 DO 400 J=1,4
394 DHG(J)=0.
395 P(I,J)=PX(1)*P(IN(6),J)+PY(1)*P(IN(6)+1,J)+PX(3)*P(IN(3),J)+
396 &PY(3)*P(IN(3)+1,J)
397 DO 390 IN1=IN(4),IN(1)-4,4
398 390 P(I,J)=P(I,J)+P(IN1+2,3)*P(IN1,J)
399 DO 400 IN2=IN(5),IN(2)-4,4
400 400 P(I,J)=P(I,J)+P(IN2+2,3)*P(IN2,J)
401 DHM(1)=FOUR(I,I)
402 DHM(2)=2.*FOUR(I,IN(1))
403 DHM(3)=2.*FOUR(I,IN(2))
404 DHM(4)=2.*FOUR(IN(1),IN(2))
405
406C...Junction strings: find coefficients for Gamma expression.
407 DO 410 IN2=IN(1)+1,IN(2),4
408 DO 410 IN1=IN(1),IN2-1,4
409 DHC=2.*FOUR(IN1,IN2)
410 DHG(1)=DHG(1)+P(IN1+2,1)*P(IN2+2,1)*DHC
411 IF(IN1.EQ.IN(1)) DHG(2)=DHG(2)-P(IN2+2,1)*DHC
412 IF(IN2.EQ.IN(2)) DHG(3)=DHG(3)+P(IN1+2,1)*DHC
413 410 IF(IN1.EQ.IN(1).AND.IN2.EQ.IN(2)) DHG(4)=DHG(4)-DHC
414
415C...Junction strings: solve (m2, Gamma) equation system for energies.
416 DHS1=DHM(3)*DHG(4)-DHM(4)*DHG(3)
417 IF(ABS(DHS1).LT.1E-4) GOTO 270
418 DHS2=DHM(4)*(GAM(3)-DHG(1))-DHM(2)*DHG(3)-DHG(4)*
419 &(P(I,5)**2-DHM(1))+DHG(2)*DHM(3)
420 DHS3=DHM(2)*(GAM(3)-DHG(1))-DHG(2)*(P(I,5)**2-DHM(1))
421 P(IN(2)+2,4)=0.5*(SQRT(MAX(0D0,DHS2**2-4.*DHS1*DHS3))/ABS(DHS1)-
422 &DHS2/DHS1)
423 IF(DHM(2)+DHM(4)*P(IN(2)+2,4).LE.0.) GOTO 270
424 P(IN(1)+2,4)=(P(I,5)**2-DHM(1)-DHM(3)*P(IN(2)+2,4))/
425 &(DHM(2)+DHM(4)*P(IN(2)+2,4))
426
427C...Junction strings: step to new region if necessary.
428 IF(P(IN(2)+2,4).GT.P(IN(2)+2,3)) THEN
429 P(IN(2)+2,4)=P(IN(2)+2,3)
430 P(IN(2)+2,1)=1.
431 IN(2)=IN(2)+4
432 IF(IN(2).GT.N+NR+4*NS) GOTO 270
433 IF(FOUR(IN(1),IN(2)).LE.1E-2) THEN
434 P(IN(1)+2,4)=P(IN(1)+2,3)
435 P(IN(1)+2,1)=0.
436 IN(1)=IN(1)+4
437 ENDIF
438 GOTO 360
439 ELSEIF(P(IN(1)+2,4).GT.P(IN(1)+2,3)) THEN
440 P(IN(1)+2,4)=P(IN(1)+2,3)
441 P(IN(1)+2,1)=0.
442 IN(1)=IN(1)+JS
443 GOTO 710
444 ENDIF
445
446C...Junction strings: particle four-momentum, remainder, loop back.
447 420 DO 430 J=1,4
448 P(I,J)=P(I,J)+P(IN(1)+2,4)*P(IN(1),J)+P(IN(2)+2,4)*P(IN(2),J)
449 430 PJU(IU+3,J)=PJU(IU+3,J)+P(I,J)
450 IF(P(I,4).LE.0.) GOTO 270
451 PJU(IU+3,5)=TJU(4)*PJU(IU+3,4)-TJU(1)*PJU(IU+3,1)-
452 &TJU(2)*PJU(IU+3,2)-TJU(3)*PJU(IU+3,3)
453 IF(PJU(IU+3,5).LT.PJU(IU,5)) THEN
454 KFL(1)=-KFL(3)
455 PX(1)=-PX(3)
456 PY(1)=-PY(3)
457 GAM(1)=GAM(3)
458 IF(IN(3).NE.IN(6)) THEN
459 DO 440 J=1,4
460 P(IN(6),J)=P(IN(3),J)
461 440 P(IN(6)+1,J)=P(IN(3)+1,J)
462 ENDIF
463 DO 450 JQ=1,2
464 IN(3+JQ)=IN(JQ)
465 P(IN(JQ)+2,3)=P(IN(JQ)+2,3)-P(IN(JQ)+2,4)
466 450 P(IN(JQ)+2,1)=P(IN(JQ)+2,1)-(3-2*JQ)*P(IN(JQ)+2,4)
467 GOTO 320
468 ENDIF
469
470C...Junction strings: save quantities left after each string.
471 IF(IABS(KFL(1)).GT.10) GOTO 270
472 I=I-1
473 KFJH(IU)=KFL(1)
474 DO 460 J=1,4
475 460 PJU(IU+3,J)=PJU(IU+3,J)-P(I+1,J)
476 470 CONTINUE
477
478C...Junction strings: put together to new effective string endpoint.
479 NJS(JT)=I-ISTA
480 KFJS(JT)=K(K(MJU(JT+2),3),2)
481 KFLS=2*INT(RLU(0)+3.*PARJ(4)/(1.+3.*PARJ(4)))+1
482 IF(KFJH(1).EQ.KFJH(2)) KFLS=3
483 IF(ISTA.NE.I) KFJS(JT)=ISIGN(1000*MAX(IABS(KFJH(1)),
484 &IABS(KFJH(2)))+100*MIN(IABS(KFJH(1)),IABS(KFJH(2)))+
485 &KFLS,KFJH(1))
486 DO 480 J=1,4
487 PJS(JT,J)=PJU(1,J)+PJU(2,J)+P(MJU(JT),J)
488 480 PJS(JT+2,J)=PJU(4,J)+PJU(5,J)
489 PJS(JT,5)=SQRT(MAX(0.,PJS(JT,4)**2-PJS(JT,1)**2-PJS(JT,2)**2-
490 &PJS(JT,3)**2))
491 490 CONTINUE
492
493C...Open versus closed strings. Choose breakup region for latter.
494 500 IF(MJU(1).NE.0.AND.MJU(2).NE.0) THEN
495 NS=MJU(2)-MJU(1)
496 NB=MJU(1)-N
497 ELSEIF(MJU(1).NE.0) THEN
498 NS=N+NR-MJU(1)
499 NB=MJU(1)-N
500 ELSEIF(MJU(2).NE.0) THEN
501 NS=MJU(2)-N
502 NB=1
503 ELSEIF(IABS(K(N+1,2)).NE.21) THEN
504 NS=NR-1
505 NB=1
506 ELSE
507 NS=NR+1
508 W2SUM=0.
509 DO 510 IS=1,NR
510 P(N+NR+IS,1)=0.5*FOUR(N+IS,N+IS+1-NR*(IS/NR))
511 510 W2SUM=W2SUM+P(N+NR+IS,1)
512 W2RAN=RLU(0)*W2SUM
513 NB=0
514 520 NB=NB+1
515 W2SUM=W2SUM-P(N+NR+NB,1)
516 IF(W2SUM.GT.W2RAN.AND.NB.LT.NR) GOTO 520
517 ENDIF
518
519C...Find longitudinal string directions (i.e. lightlike four-vectors).
520 DO 540 IS=1,NS
521 IS1=N+IS+NB-1-NR*((IS+NB-2)/NR)
522 IS2=N+IS+NB-NR*((IS+NB-1)/NR)
523 DO 530 J=1,5
524 DP(1,J)=P(IS1,J)
525 IF(IABS(K(IS1,2)).EQ.21) DP(1,J)=0.5*DP(1,J)
526 IF(IS1.EQ.MJU(1)) DP(1,J)=PJS(1,J)-PJS(3,J)
527 DP(2,J)=P(IS2,J)
528 IF(IABS(K(IS2,2)).EQ.21) DP(2,J)=0.5*DP(2,J)
529 530 IF(IS2.EQ.MJU(2)) DP(2,J)=PJS(2,J)-PJS(4,J)
530 DP(3,5)=DFOUR(1,1)
531 DP(4,5)=DFOUR(2,2)
532 DHKC=DFOUR(1,2)
533 IF(DP(3,5)+2.*DHKC+DP(4,5).LE.0.) THEN
534 DP(3,5)=DP(1,5)**2
535 DP(4,5)=DP(2,5)**2
536 DP(1,4)=SQRT(DP(1,1)**2+DP(1,2)**2+DP(1,3)**2+DP(1,5)**2)
537 DP(2,4)=SQRT(DP(2,1)**2+DP(2,2)**2+DP(2,3)**2+DP(2,5)**2)
538 DHKC=DFOUR(1,2)
539 ENDIF
540 DHKS=SQRT(DHKC**2-DP(3,5)*DP(4,5))
541 DHK1=0.5*((DP(4,5)+DHKC)/DHKS-1.)
542 DHK2=0.5*((DP(3,5)+DHKC)/DHKS-1.)
543 IN1=N+NR+4*IS-3
544 P(IN1,5)=SQRT(DP(3,5)+2.*DHKC+DP(4,5))
545 DO 540 J=1,4
546 P(IN1,J)=(1.+DHK1)*DP(1,J)-DHK2*DP(2,J)
547 540 P(IN1+1,J)=(1.+DHK2)*DP(2,J)-DHK1*DP(1,J)
548
549C...Begin initialization: sum up energy, set starting position.
550 ISAV=I
551 550 NTRY=NTRY+1
552 IF(NTRY.GT.100.AND.NTRYR.LE.4) THEN
553 PARU12=4.*PARU12
554 PARU13=2.*PARU13
555 GOTO 130
556 ELSEIF(NTRY.GT.100) THEN
557 CALL LUERRM(14,'(LUSTRF:) caught in infinite loop')
558 IF(MSTU(21).GE.1) RETURN
559 ENDIF
560 I=ISAV
561 DO 560 J=1,4
562 P(N+NRS,J)=0.
563 DO 560 IS=1,NR
564 560 P(N+NRS,J)=P(N+NRS,J)+P(N+IS,J)
565 DO 570 JT=1,2
566 IRANK(JT)=0
567 IF(MJU(JT).NE.0) IRANK(JT)=NJS(JT)
568 IF(NS.GT.NR) IRANK(JT)=1
569 IE(JT)=K(N+1+(JT/2)*(NP-1),3)
570 IN(3*JT+1)=N+NR+1+4*(JT/2)*(NS-1)
571 IN(3*JT+2)=IN(3*JT+1)+1
572 IN(3*JT+3)=N+NR+4*NS+2*JT-1
573 DO 570 IN1=N+NR+2+JT,N+NR+4*NS-2+JT,4
574 P(IN1,1)=2-JT
575 P(IN1,2)=JT-1
576 570 P(IN1,3)=1.
577
578C...Initialize flavour and pT variables for open string.
579 IF(NS.LT.NR) THEN
580 PX(1)=0.
581 PY(1)=0.
582 IF(NS.EQ.1.AND.MJU(1)+MJU(2).EQ.0) CALL LUPTDI(0,PX(1),PY(1))
583 PX(2)=-PX(1)
584 PY(2)=-PY(1)
585 DO 580 JT=1,2
586 KFL(JT)=K(IE(JT),2)
587 IF(MJU(JT).NE.0) KFL(JT)=KFJS(JT)
588 MSTJ(93)=1
589 PMQ(JT)=ULMASS(KFL(JT))
590 580 GAM(JT)=0.
591
592C...Closed string: random initial breakup flavour, pT and vertex.
593 ELSE
594 KFL(3)=INT(1.+(2.+PARJ(2))*RLU(0))*(-1)**INT(RLU(0)+0.5)
595 CALL LUKFDI(KFL(3),0,KFL(1),KDUMP)
596 KFL(2)=-KFL(1)
597 IF(IABS(KFL(1)).GT.10.AND.RLU(0).GT.0.5) THEN
598 KFL(2)=-(KFL(1)+ISIGN(10000,KFL(1)))
599 ELSEIF(IABS(KFL(1)).GT.10) THEN
600 KFL(1)=-(KFL(2)+ISIGN(10000,KFL(2)))
601 ENDIF
602 CALL LUPTDI(KFL(1),PX(1),PY(1))
603 PX(2)=-PX(1)
604 PY(2)=-PY(1)
605 PR3=MIN(25.,0.1*P(N+NR+1,5)**2)
606 590 CALL LUZDIS(KFL(1),KFL(2),PR3,Z)
607 ZR=PR3/(Z*P(N+NR+1,5)**2)
608 IF(ZR.GE.1.) GOTO 590
609 DO 600 JT=1,2
610 MSTJ(93)=1
611 PMQ(JT)=ULMASS(KFL(JT))
612 GAM(JT)=PR3*(1.-Z)/Z
613 IN1=N+NR+3+4*(JT/2)*(NS-1)
614 P(IN1,JT)=1.-Z
615 P(IN1,3-JT)=JT-1
616 P(IN1,3)=(2-JT)*(1.-Z)+(JT-1)*Z
617 P(IN1+1,JT)=ZR
618 P(IN1+1,3-JT)=2-JT
619 600 P(IN1+1,3)=(2-JT)*(1.-ZR)+(JT-1)*ZR
620 ENDIF
621
622C...Find initial transverse directions (i.e. spacelike four-vectors).
623 DO 640 JT=1,2
624 IF(JT.EQ.1.OR.NS.EQ.NR-1) THEN
625 IN1=IN(3*JT+1)
626 IN3=IN(3*JT+3)
627 DO 610 J=1,4
628 DP(1,J)=P(IN1,J)
629 DP(2,J)=P(IN1+1,J)
630 DP(3,J)=0.
631 610 DP(4,J)=0.
632 DP(1,4)=SQRT(DP(1,1)**2+DP(1,2)**2+DP(1,3)**2)
633 DP(2,4)=SQRT(DP(2,1)**2+DP(2,2)**2+DP(2,3)**2)
634 DP(5,1)=DP(1,1)/DP(1,4)-DP(2,1)/DP(2,4)
635 DP(5,2)=DP(1,2)/DP(1,4)-DP(2,2)/DP(2,4)
636 DP(5,3)=DP(1,3)/DP(1,4)-DP(2,3)/DP(2,4)
637 IF(DP(5,1)**2.LE.DP(5,2)**2+DP(5,3)**2) DP(3,1)=1.
638 IF(DP(5,1)**2.GT.DP(5,2)**2+DP(5,3)**2) DP(3,3)=1.
639 IF(DP(5,2)**2.LE.DP(5,1)**2+DP(5,3)**2) DP(4,2)=1.
640 IF(DP(5,2)**2.GT.DP(5,1)**2+DP(5,3)**2) DP(4,3)=1.
641 DHC12=DFOUR(1,2)
642 DHCX1=DFOUR(3,1)/DHC12
643 DHCX2=DFOUR(3,2)/DHC12
644 DHCXX=1D0/SQRT(1D0+2D0*DHCX1*DHCX2*DHC12)
645 DHCY1=DFOUR(4,1)/DHC12
646 DHCY2=DFOUR(4,2)/DHC12
647 DHCYX=DHCXX*(DHCX1*DHCY2+DHCX2*DHCY1)*DHC12
648 DHCYY=1D0/SQRT(1D0+2D0*DHCY1*DHCY2*DHC12-DHCYX**2)
649 DO 620 J=1,4
650 DP(3,J)=DHCXX*(DP(3,J)-DHCX2*DP(1,J)-DHCX1*DP(2,J))
651 P(IN3,J)=DP(3,J)
652 620 P(IN3+1,J)=DHCYY*(DP(4,J)-DHCY2*DP(1,J)-DHCY1*DP(2,J)-
653 & DHCYX*DP(3,J))
654 ELSE
655 DO 630 J=1,4
656 P(IN3+2,J)=P(IN3,J)
657 630 P(IN3+3,J)=P(IN3+1,J)
658 ENDIF
659 640 CONTINUE
660
661C...Remove energy used up in junction string fragmentation.
662 IF(MJU(1)+MJU(2).GT.0) THEN
663 DO 660 JT=1,2
664 IF(NJS(JT).EQ.0) GOTO 660
665 DO 650 J=1,4
666 650 P(N+NRS,J)=P(N+NRS,J)-PJS(JT+2,J)
667 660 CONTINUE
668 ENDIF
669
670C...Produce new particle: side, origin.
671 670 I=I+1
672 IF(2*I-NSAV.GE.MSTU(4)-MSTU(32)-5) THEN
673 CALL LUERRM(11,'(LUSTRF:) no more memory left in LUJETS')
674 IF(MSTU(21).GE.1) RETURN
675 ENDIF
676 JT=1.5+RLU(0)
677 IF(IABS(KFL(3-JT)).GT.10) JT=3-JT
678 JR=3-JT
679 JS=3-2*JT
680 IRANK(JT)=IRANK(JT)+1
681 K(I,1)=1
682 K(I,3)=IE(JT)
683 K(I,4)=0
684 K(I,5)=0
685
686C...Generate flavour, hadron and pT.
687 680 CALL LUKFDI(KFL(JT),0,KFL(3),K(I,2))
688 IF(K(I,2).EQ.0) GOTO 550
689 IF(MSTJ(12).GE.3.AND.IRANK(JT).EQ.1.AND.IABS(KFL(JT)).LE.10.AND.
690 &IABS(KFL(3)).GT.10) THEN
691 IF(RLU(0).GT.PARJ(19)) GOTO 680
692 ENDIF
693 P(I,5)=ULMASS(K(I,2))
694 CALL LUPTDI(KFL(JT),PX(3),PY(3))
695 PR(JT)=P(I,5)**2+(PX(JT)+PX(3))**2+(PY(JT)+PY(3))**2
696
697C...Final hadrons for small invariant mass.
698 MSTJ(93)=1
699 PMQ(3)=ULMASS(KFL(3))
700 PARJST=PARJ(33)
701 IF(MSTJ(11).EQ.2) PARJST=PARJ(34)
702 WMIN=PARJST+PMQ(1)+PMQ(2)+PARJ(36)*PMQ(3)
703 IF(IABS(KFL(JT)).GT.10.AND.IABS(KFL(3)).GT.10) WMIN=
704 &WMIN-0.5*PARJ(36)*PMQ(3)
705 WREM2=FOUR(N+NRS,N+NRS)
706 IF(WREM2.LT.0.10) GOTO 550
707 IF(WREM2.LT.MAX(WMIN*(1.+(2.*RLU(0)-1.)*PARJ(37)),
708 &PARJ(32)+PMQ(1)+PMQ(2))**2) GOTO 810
709
710C...Choose z, which gives Gamma. Shift z for heavy flavours.
711 CALL LUZDIS(KFL(JT),KFL(3),PR(JT),Z)
712 KFL1A=IABS(KFL(1))
713 KFL2A=IABS(KFL(2))
714 IF(MAX(MOD(KFL1A,10),MOD(KFL1A/1000,10),MOD(KFL2A,10),
715 &MOD(KFL2A/1000,10)).GE.4) THEN
716 PR(JR)=(PMQ(JR)+PMQ(3))**2+(PX(JR)-PX(3))**2+(PY(JR)-PY(3))**2
717 PW12=SQRT(MAX(0.,(WREM2-PR(1)-PR(2))**2-4.*PR(1)*PR(2)))
718 Z=(WREM2+PR(JT)-PR(JR)+PW12*(2.*Z-1.))/(2.*WREM2)
719 PR(JR)=(PMQ(JR)+PARJST)**2+(PX(JR)-PX(3))**2+(PY(JR)-PY(3))**2
720 IF((1.-Z)*(WREM2-PR(JT)/Z).LT.PR(JR)) GOTO 810
721 ENDIF
722 GAM(3)=(1.-Z)*(GAM(JT)+PR(JT)/Z)
723 DO 690 J=1,3
724 690 IN(J)=IN(3*JT+J)
725
726C...Stepping within or from 'low' string region easy.
727 IF(IN(1)+1.EQ.IN(2).AND.Z*P(IN(1)+2,3)*P(IN(2)+2,3)*
728 &P(IN(1),5)**2.GE.PR(JT)) THEN
729 P(IN(JT)+2,4)=Z*P(IN(JT)+2,3)
730 P(IN(JR)+2,4)=PR(JT)/(P(IN(JT)+2,4)*P(IN(1),5)**2)
731 DO 700 J=1,4
732 700 P(I,J)=(PX(JT)+PX(3))*P(IN(3),J)+(PY(JT)+PY(3))*P(IN(3)+1,J)
733 GOTO 770
734 ELSEIF(IN(1)+1.EQ.IN(2)) THEN
735 P(IN(JR)+2,4)=P(IN(JR)+2,3)
736 P(IN(JR)+2,JT)=1.
737 IN(JR)=IN(JR)+4*JS
738 IF(JS*IN(JR).GT.JS*IN(4*JR)) GOTO 550
739 IF(FOUR(IN(1),IN(2)).LE.1E-2) THEN
740 P(IN(JT)+2,4)=P(IN(JT)+2,3)
741 P(IN(JT)+2,JT)=0.
742 IN(JT)=IN(JT)+4*JS
743 ENDIF
744 ENDIF
745
746C...Find new transverse directions (i.e. spacelike string vectors).
747 710 IF(JS*IN(1).GT.JS*IN(3*JR+1).OR.JS*IN(2).GT.JS*IN(3*JR+2).OR.
748 &IN(1).GT.IN(2)) GOTO 550
749 IF(IN(1).NE.IN(3*JT+1).OR.IN(2).NE.IN(3*JT+2)) THEN
750 DO 720 J=1,4
751 DP(1,J)=P(IN(1),J)
752 DP(2,J)=P(IN(2),J)
753 DP(3,J)=0.
754 720 DP(4,J)=0.
755 DP(1,4)=SQRT(DP(1,1)**2+DP(1,2)**2+DP(1,3)**2)
756 DP(2,4)=SQRT(DP(2,1)**2+DP(2,2)**2+DP(2,3)**2)
757 DHC12=DFOUR(1,2)
758 IF(DHC12.LE.1E-2) THEN
759 P(IN(JT)+2,4)=P(IN(JT)+2,3)
760 P(IN(JT)+2,JT)=0.
761 IN(JT)=IN(JT)+4*JS
762 GOTO 710
763 ENDIF
764 IN(3)=N+NR+4*NS+5
765 DP(5,1)=DP(1,1)/DP(1,4)-DP(2,1)/DP(2,4)
766 DP(5,2)=DP(1,2)/DP(1,4)-DP(2,2)/DP(2,4)
767 DP(5,3)=DP(1,3)/DP(1,4)-DP(2,3)/DP(2,4)
768 IF(DP(5,1)**2.LE.DP(5,2)**2+DP(5,3)**2) DP(3,1)=1.
769 IF(DP(5,1)**2.GT.DP(5,2)**2+DP(5,3)**2) DP(3,3)=1.
770 IF(DP(5,2)**2.LE.DP(5,1)**2+DP(5,3)**2) DP(4,2)=1.
771 IF(DP(5,2)**2.GT.DP(5,1)**2+DP(5,3)**2) DP(4,3)=1.
772 DHCX1=DFOUR(3,1)/DHC12
773 DHCX2=DFOUR(3,2)/DHC12
774 DHCXX=1D0/SQRT(1D0+2D0*DHCX1*DHCX2*DHC12)
775 DHCY1=DFOUR(4,1)/DHC12
776 DHCY2=DFOUR(4,2)/DHC12
777 DHCYX=DHCXX*(DHCX1*DHCY2+DHCX2*DHCY1)*DHC12
778 DHCYY=1D0/SQRT(1D0+2D0*DHCY1*DHCY2*DHC12-DHCYX**2)
779 DO 730 J=1,4
780 DP(3,J)=DHCXX*(DP(3,J)-DHCX2*DP(1,J)-DHCX1*DP(2,J))
781 P(IN(3),J)=DP(3,J)
782 730 P(IN(3)+1,J)=DHCYY*(DP(4,J)-DHCY2*DP(1,J)-DHCY1*DP(2,J)-
783 & DHCYX*DP(3,J))
784C...Express pT with respect to new axes, if sensible.
785 PXP=-(PX(3)*FOUR(IN(3*JT+3),IN(3))+PY(3)*
786 & FOUR(IN(3*JT+3)+1,IN(3)))
787 PYP=-(PX(3)*FOUR(IN(3*JT+3),IN(3)+1)+PY(3)*
788 & FOUR(IN(3*JT+3)+1,IN(3)+1))
789 IF(ABS(PXP**2+PYP**2-PX(3)**2-PY(3)**2).LT.0.01) THEN
790 PX(3)=PXP
791 PY(3)=PYP
792 ENDIF
793 ENDIF
794
795C...Sum up known four-momentum. Gives coefficients for m2 expression.
796 DO 750 J=1,4
797 DHG(J)=0.
798 P(I,J)=PX(JT)*P(IN(3*JT+3),J)+PY(JT)*P(IN(3*JT+3)+1,J)+
799 &PX(3)*P(IN(3),J)+PY(3)*P(IN(3)+1,J)
800 DO 740 IN1=IN(3*JT+1),IN(1)-4*JS,4*JS
801 740 P(I,J)=P(I,J)+P(IN1+2,3)*P(IN1,J)
802 DO 750 IN2=IN(3*JT+2),IN(2)-4*JS,4*JS
803 750 P(I,J)=P(I,J)+P(IN2+2,3)*P(IN2,J)
804 DHM(1)=FOUR(I,I)
805 DHM(2)=2.*FOUR(I,IN(1))
806 DHM(3)=2.*FOUR(I,IN(2))
807 DHM(4)=2.*FOUR(IN(1),IN(2))
808
809C...Find coefficients for Gamma expression.
810 DO 760 IN2=IN(1)+1,IN(2),4
811 DO 760 IN1=IN(1),IN2-1,4
812 DHC=2.*FOUR(IN1,IN2)
813 DHG(1)=DHG(1)+P(IN1+2,JT)*P(IN2+2,JT)*DHC
814 IF(IN1.EQ.IN(1)) DHG(2)=DHG(2)-JS*P(IN2+2,JT)*DHC
815 IF(IN2.EQ.IN(2)) DHG(3)=DHG(3)+JS*P(IN1+2,JT)*DHC
816 760 IF(IN1.EQ.IN(1).AND.IN2.EQ.IN(2)) DHG(4)=DHG(4)-DHC
817
818C...Solve (m2, Gamma) equation system for energies taken.
819 DHS1=DHM(JR+1)*DHG(4)-DHM(4)*DHG(JR+1)
820 IF(ABS(DHS1).LT.1E-4) GOTO 550
821 DHS2=DHM(4)*(GAM(3)-DHG(1))-DHM(JT+1)*DHG(JR+1)-DHG(4)*
822 &(P(I,5)**2-DHM(1))+DHG(JT+1)*DHM(JR+1)
823 DHS3=DHM(JT+1)*(GAM(3)-DHG(1))-DHG(JT+1)*(P(I,5)**2-DHM(1))
824 P(IN(JR)+2,4)=0.5*(SQRT(MAX(0D0,DHS2**2-4.*DHS1*DHS3))/ABS(DHS1)-
825 &DHS2/DHS1)
826 IF(DHM(JT+1)+DHM(4)*P(IN(JR)+2,4).LE.0.) GOTO 550
827 P(IN(JT)+2,4)=(P(I,5)**2-DHM(1)-DHM(JR+1)*P(IN(JR)+2,4))/
828 &(DHM(JT+1)+DHM(4)*P(IN(JR)+2,4))
829
830C...Step to new region if necessary.
831 IF(P(IN(JR)+2,4).GT.P(IN(JR)+2,3)) THEN
832 P(IN(JR)+2,4)=P(IN(JR)+2,3)
833 P(IN(JR)+2,JT)=1.
834 IN(JR)=IN(JR)+4*JS
835 IF(JS*IN(JR).GT.JS*IN(4*JR)) GOTO 550
836 IF(FOUR(IN(1),IN(2)).LE.1E-2) THEN
837 P(IN(JT)+2,4)=P(IN(JT)+2,3)
838 P(IN(JT)+2,JT)=0.
839 IN(JT)=IN(JT)+4*JS
840 ENDIF
841 GOTO 710
842 ELSEIF(P(IN(JT)+2,4).GT.P(IN(JT)+2,3)) THEN
843 P(IN(JT)+2,4)=P(IN(JT)+2,3)
844 P(IN(JT)+2,JT)=0.
845 IN(JT)=IN(JT)+4*JS
846 GOTO 710
847 ENDIF
848
849C...Four-momentum of particle. Remaining quantities. Loop back.
850 770 DO 780 J=1,4
851 P(I,J)=P(I,J)+P(IN(1)+2,4)*P(IN(1),J)+P(IN(2)+2,4)*P(IN(2),J)
852 780 P(N+NRS,J)=P(N+NRS,J)-P(I,J)
853 IF(P(I,4).LE.0.) GOTO 550
854 KFL(JT)=-KFL(3)
855 PMQ(JT)=PMQ(3)
856 PX(JT)=-PX(3)
857 PY(JT)=-PY(3)
858 GAM(JT)=GAM(3)
859 IF(IN(3).NE.IN(3*JT+3)) THEN
860 DO 790 J=1,4
861 P(IN(3*JT+3),J)=P(IN(3),J)
862 790 P(IN(3*JT+3)+1,J)=P(IN(3)+1,J)
863 ENDIF
864 DO 800 JQ=1,2
865 IN(3*JT+JQ)=IN(JQ)
866 P(IN(JQ)+2,3)=P(IN(JQ)+2,3)-P(IN(JQ)+2,4)
867 800 P(IN(JQ)+2,JT)=P(IN(JQ)+2,JT)-JS*(3-2*JQ)*P(IN(JQ)+2,4)
868 GOTO 670
869
870C...Final hadron: side, flavour, hadron, mass.
871 810 I=I+1
872 K(I,1)=1
873 K(I,3)=IE(JR)
874 K(I,4)=0
875 K(I,5)=0
876 CALL LUKFDI(KFL(JR),-KFL(3),KFLDMP,K(I,2))
877 IF(K(I,2).EQ.0) GOTO 550
878 P(I,5)=ULMASS(K(I,2))
879 PR(JR)=P(I,5)**2+(PX(JR)-PX(3))**2+(PY(JR)-PY(3))**2
880
881C...Final two hadrons: find common setup of four-vectors.
882 JQ=1
883 IF(P(IN(4)+2,3)*P(IN(5)+2,3)*FOUR(IN(4),IN(5)).LT.P(IN(7),3)*
884 &P(IN(8),3)*FOUR(IN(7),IN(8))) JQ=2
885 DHC12=FOUR(IN(3*JQ+1),IN(3*JQ+2))
886 DHR1=FOUR(N+NRS,IN(3*JQ+2))/DHC12
887 DHR2=FOUR(N+NRS,IN(3*JQ+1))/DHC12
888 IF(IN(4).NE.IN(7).OR.IN(5).NE.IN(8)) THEN
889 PX(3-JQ)=-FOUR(N+NRS,IN(3*JQ+3))-PX(JQ)
890 PY(3-JQ)=-FOUR(N+NRS,IN(3*JQ+3)+1)-PY(JQ)
891 PR(3-JQ)=P(I+(JT+JQ-3)**2-1,5)**2+(PX(3-JQ)+(2*JQ-3)*JS*
892 & PX(3))**2+(PY(3-JQ)+(2*JQ-3)*JS*PY(3))**2
893 ENDIF
894
895C...Solve kinematics for final two hadrons, if possible.
896 WREM2=WREM2+(PX(1)+PX(2))**2+(PY(1)+PY(2))**2
897 FD=(SQRT(PR(1))+SQRT(PR(2)))/SQRT(WREM2)
898 IF(MJU(1)+MJU(2).NE.0.AND.I.EQ.ISAV+2.AND.FD.GE.1.) GOTO 180
899 IF(FD.GE.1.) GOTO 550
900 FA=WREM2+PR(JT)-PR(JR)
901 IF(MSTJ(11).NE.2) PREV=0.5*EXP(MAX(-80.,LOG(FD)*PARJ(38)*
902 &(PR(1)+PR(2))**2))
903 IF(MSTJ(11).EQ.2) PREV=0.5*FD**PARJ(39)
904 FB=SIGN(SQRT(MAX(0.,FA**2-4.*WREM2*PR(JT))),JS*(RLU(0)-PREV))
905 KFL1A=IABS(KFL(1))
906 KFL2A=IABS(KFL(2))
907 IF(MAX(MOD(KFL1A,10),MOD(KFL1A/1000,10),MOD(KFL2A,10),
908 &MOD(KFL2A/1000,10)).GE.6) FB=SIGN(SQRT(MAX(0.,FA**2-
909 &4.*WREM2*PR(JT))),FLOAT(JS))
910 DO 820 J=1,4
911 P(I-1,J)=(PX(JT)+PX(3))*P(IN(3*JQ+3),J)+(PY(JT)+PY(3))*
912 &P(IN(3*JQ+3)+1,J)+0.5*(DHR1*(FA+FB)*P(IN(3*JQ+1),J)+
913 &DHR2*(FA-FB)*P(IN(3*JQ+2),J))/WREM2
914 820 P(I,J)=P(N+NRS,J)-P(I-1,J)
915
916C...Mark jets as fragmented and give daughter pointers.
917 N=I-NRS+1
918 DO 830 I=NSAV+1,NSAV+NP
919 IM=K(I,3)
920 K(IM,1)=K(IM,1)+10
921 IF(MSTU(16).NE.2) THEN
922 K(IM,4)=NSAV+1
923 K(IM,5)=NSAV+1
924 ELSE
925 K(IM,4)=NSAV+2
926 K(IM,5)=N
927 ENDIF
928 830 CONTINUE
929
930C...Document string system. Move up particles.
931 NSAV=NSAV+1
932 K(NSAV,1)=11
933 K(NSAV,2)=92
934 K(NSAV,3)=IP
935 K(NSAV,4)=NSAV+1
936 K(NSAV,5)=N
937 DO 840 J=1,4
938 P(NSAV,J)=DPS(J)
939 840 V(NSAV,J)=V(IP,J)
940 P(NSAV,5)=SQRT(MAX(0D0,DPS(4)**2-DPS(1)**2-DPS(2)**2-DPS(3)**2))
941 V(NSAV,5)=0.
942 DO 850 I=NSAV+1,N
943 DO 850 J=1,5
944 K(I,J)=K(I+NRS-1,J)
945 P(I,J)=P(I+NRS-1,J)
946 850 V(I,J)=0.
947
948C...Order particles in rank along the chain. Update mother pointer.
949 DO 860 I=NSAV+1,N
950 DO 860 J=1,5
951 K(I-NSAV+N,J)=K(I,J)
952 860 P(I-NSAV+N,J)=P(I,J)
953 I1=NSAV
954 DO 880 I=N+1,2*N-NSAV
955 IF(K(I,3).NE.IE(1)) GOTO 880
956 I1=I1+1
957 DO 870 J=1,5
958 K(I1,J)=K(I,J)
959 870 P(I1,J)=P(I,J)
960 IF(MSTU(16).NE.2) K(I1,3)=NSAV
961 880 CONTINUE
962 DO 900 I=2*N-NSAV,N+1,-1
963 IF(K(I,3).EQ.IE(1)) GOTO 900
964 I1=I1+1
965 DO 890 J=1,5
966 K(I1,J)=K(I,J)
967 890 P(I1,J)=P(I,J)
968 IF(MSTU(16).NE.2) K(I1,3)=NSAV
969 900 CONTINUE
970
971C...Boost back particle system. Set production vertices.
972 MSTU(33)=1
973 CALL LUDBRB(NSAV+1,N,0.,0.,DPS(1)/DPS(4),DPS(2)/DPS(4),
974 &DPS(3)/DPS(4))
975 DO 910 I=NSAV+1,N
976 DO 910 J=1,4
977 910 V(I,J)=V(IP,J)
978
979 RETURN
980 END