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lucell.f
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1 
2 C*********************************************************************
3 
4  SUBROUTINE lucell(NJET)
5 
6 C...Purpose: to provide a simple way of jet finding in an eta-phi-ET
7 C...coordinate frame, as used for calorimeters at hadron colliders.
8  common/lujets/n,k(9000,5),p(9000,5),v(9000,5)
9  SAVE /lujets/
10  common/ludat1/mstu(200),paru(200),mstj(200),parj(200)
11  SAVE /ludat1/
12  common/ludat2/kchg(500,3),pmas(500,4),parf(2000),vckm(4,4)
13  SAVE /ludat2/
14 
15 C...Loop over all particles. Find cell that was hit by given particle.
16  nce2=2*mstu(51)*mstu(52)
17  ptlrat=1./sinh(paru(51))**2
18  np=0
19  nc=n
20  DO 110 i=1,n
21  IF(k(i,1).LE.0.OR.k(i,1).GT.10) goto 110
22  IF(p(i,1)**2+p(i,2)**2.LE.ptlrat*p(i,3)**2) goto 110
23  IF(mstu(41).GE.2) THEN
24  kc=lucomp(k(i,2))
25  IF(kc.EQ.0.OR.kc.EQ.12.OR.kc.EQ.14.OR.kc.EQ.16.OR.
26  & kc.EQ.18) goto 110
27  IF(mstu(41).GE.3.AND.kchg(kc,2).EQ.0.AND.luchge(k(i,2)).EQ.0)
28  & goto 110
29  ENDIF
30  np=np+1
31  pt=sqrt(p(i,1)**2+p(i,2)**2)
32  eta=sign(log((sqrt(pt**2+p(i,3)**2)+abs(p(i,3)))/pt),p(i,3))
33  ieta=max(1,min(mstu(51),1+int(mstu(51)*0.5*(eta/paru(51)+1.))))
34  phi=ulangl(p(i,1),p(i,2))
35  iphi=max(1,min(mstu(52),1+int(mstu(52)*0.5*(phi/paru(1)+1.))))
36  ietph=mstu(52)*ieta+iphi
37 
38 C...Add to cell already hit, or book new cell.
39  DO 100 ic=n+1,nc
40  IF(ietph.EQ.k(ic,3)) THEN
41  k(ic,4)=k(ic,4)+1
42  p(ic,5)=p(ic,5)+pt
43  goto 110
44  ENDIF
45  100 CONTINUE
46  IF(nc.GE.mstu(4)-mstu(32)-5) THEN
47  CALL luerrm(11,'(LUCELL:) no more memory left in LUJETS')
48  njet=-2
49  RETURN
50  ENDIF
51  nc=nc+1
52  k(nc,3)=ietph
53  k(nc,4)=1
54  k(nc,5)=2
55  p(nc,1)=(paru(51)/mstu(51))*(2*ieta-1-mstu(51))
56  p(nc,2)=(paru(1)/mstu(52))*(2*iphi-1-mstu(52))
57  p(nc,5)=pt
58  110 CONTINUE
59 
60 C...Smear true bin content by calorimeter resolution.
61  IF(mstu(53).GE.1) THEN
62  DO 130 ic=n+1,nc
63  pei=p(ic,5)
64  IF(mstu(53).EQ.2) pei=p(ic,5)/cosh(p(ic,1))
65  120 pef=pei+paru(55)*sqrt(-2.*log(max(1e-10,rlu(0)))*pei)*
66  & cos(paru(2)*rlu(0))
67  IF(pef.LT.0..OR.pef.GT.paru(56)*pei) goto 120
68  p(ic,5)=pef
69  130 IF(mstu(53).EQ.2) p(ic,5)=pef*cosh(p(ic,1))
70  ENDIF
71 
72 C...Find initiator cell: the one with highest pT of not yet used ones.
73  nj=nc
74  140 etmax=0.
75  DO 150 ic=n+1,nc
76  IF(k(ic,5).NE.2) goto 150
77  IF(p(ic,5).LE.etmax) goto 150
78  icmax=ic
79  eta=p(ic,1)
80  phi=p(ic,2)
81  etmax=p(ic,5)
82  150 CONTINUE
83  IF(etmax.LT.paru(52)) goto 210
84  IF(nj.GE.mstu(4)-mstu(32)-5) THEN
85  CALL luerrm(11,'(LUCELL:) no more memory left in LUJETS')
86  njet=-2
87  RETURN
88  ENDIF
89  k(icmax,5)=1
90  nj=nj+1
91  k(nj,4)=0
92  k(nj,5)=1
93  p(nj,1)=eta
94  p(nj,2)=phi
95  p(nj,3)=0.
96  p(nj,4)=0.
97  p(nj,5)=0.
98 
99 C...Sum up unused cells within required distance of initiator.
100  DO 160 ic=n+1,nc
101  IF(k(ic,5).EQ.0) goto 160
102  IF(abs(p(ic,1)-eta).GT.paru(54)) goto 160
103  dphia=abs(p(ic,2)-phi)
104  IF(dphia.GT.paru(54).AND.dphia.LT.paru(2)-paru(54)) goto 160
105  phic=p(ic,2)
106  IF(dphia.GT.paru(1)) phic=phic+sign(paru(2),phi)
107  IF((p(ic,1)-eta)**2+(phic-phi)**2.GT.paru(54)**2) goto 160
108  k(ic,5)=-k(ic,5)
109  k(nj,4)=k(nj,4)+k(ic,4)
110  p(nj,3)=p(nj,3)+p(ic,5)*p(ic,1)
111  p(nj,4)=p(nj,4)+p(ic,5)*phic
112  p(nj,5)=p(nj,5)+p(ic,5)
113  160 CONTINUE
114 
115 C...Reject cluster below minimum ET, else accept.
116  IF(p(nj,5).LT.paru(53)) THEN
117  nj=nj-1
118  DO 170 ic=n+1,nc
119  170 IF(k(ic,5).LT.0) k(ic,5)=-k(ic,5)
120  ELSEIF(mstu(54).LE.2) THEN
121  p(nj,3)=p(nj,3)/p(nj,5)
122  p(nj,4)=p(nj,4)/p(nj,5)
123  IF(abs(p(nj,4)).GT.paru(1)) p(nj,4)=p(nj,4)-sign(paru(2),
124  & p(nj,4))
125  DO 180 ic=n+1,nc
126  180 IF(k(ic,1).LT.0) k(ic,1)=0
127  ELSE
128  DO 190 j=1,4
129  190 p(nj,j)=0.
130  DO 200 ic=n+1,nc
131  IF(k(ic,5).GE.0) goto 200
132  p(nj,1)=p(nj,1)+p(ic,5)*cos(p(ic,2))
133  p(nj,2)=p(nj,2)+p(ic,5)*sin(p(ic,2))
134  p(nj,3)=p(nj,3)+p(ic,5)*sinh(p(ic,1))
135  p(nj,4)=p(nj,4)+p(ic,5)*cosh(p(ic,1))
136  k(ic,5)=0
137  200 CONTINUE
138  ENDIF
139  goto 140
140 
141 C...Arrange clusters in falling ET sequence.
142  210 DO 230 i=1,nj-nc
143  etmax=0.
144  DO 220 ij=nc+1,nj
145  IF(k(ij,5).EQ.0) goto 220
146  IF(p(ij,5).LT.etmax) goto 220
147  ijmax=ij
148  etmax=p(ij,5)
149  220 CONTINUE
150  k(ijmax,5)=0
151  k(n+i,1)=31
152  k(n+i,2)=98
153  k(n+i,3)=i
154  k(n+i,4)=k(ijmax,4)
155  k(n+i,5)=0
156  DO 230 j=1,5
157  p(n+i,j)=p(ijmax,j)
158  230 v(n+i,j)=0.
159  njet=nj-nc
160 
161 C...Convert to massless or massive four-vectors.
162  IF(mstu(54).EQ.2) THEN
163  DO 240 i=n+1,n+njet
164  eta=p(i,3)
165  p(i,1)=p(i,5)*cos(p(i,4))
166  p(i,2)=p(i,5)*sin(p(i,4))
167  p(i,3)=p(i,5)*sinh(eta)
168  p(i,4)=p(i,5)*cosh(eta)
169  240 p(i,5)=0.
170  ELSEIF(mstu(54).GE.3) THEN
171  DO 250 i=n+1,n+njet
172  250 p(i,5)=sqrt(max(0.,p(i,4)**2-p(i,1)**2-p(i,2)**2-p(i,3)**2))
173  ENDIF
174 
175 C...Information about storage.
176  mstu(61)=n+1
177  mstu(62)=np
178  mstu(63)=nc-n
179  IF(mstu(43).LE.1) mstu(3)=njet
180  IF(mstu(43).GE.2) n=n+njet
181 
182  RETURN
183  END