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grv94lo.F
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1 *72*********************************************************************
2 ** * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
3 * *
4 * G R V - P R O T O N - P A R A M E T R I Z A T I O N S *
5 * *
6 * 1994 UPDATE *
7 * *
8 * FOR A DETAILED EXPLANATION SEE *
9 * M. GLUECK, E.REYA, A.VOGT : *
10 * DO-TH 94/24 = DESY 94-206 *
11 * (TO APPEAR IN Z. PHYS. C) *
12 * *
13 * THE PARAMETRIZATIONS ARE FITTED TO THE EVOLVED PARTONS FOR *
14 * Q**2 / GEV**2 BETWEEN 0.4 AND 1.E6 *
15 * X BETWEEN 1.E-5 AND 1. *
16 * LARGE-X REGIONS, WHERE THE DISTRIBUTION UNDER CONSIDERATION *
17 * IS NEGLIGIBLY SMALL, WERE EXCLUDED FROM THE FIT. *
18 * *
19 * HEAVY QUARK THRESHOLDS Q(H) = M(H) IN THE BETA FUNCTION : *
20 * M(C) = 1.5, M(B) = 4.5 *
21 * CORRESPONDING LAMBDA(F) VALUES IN GEV FOR Q**2 > M(H)**2 : *
22 * LO : LAMBDA(3) = 0.232, LAMBDA(4) = 0.200, *
23 * LAMBDA(5) = 0.153, *
24 * NLO : LAMBDA(3) = 0.248, LAMBDA(4) = 0.200, *
25 * LAMBDA(5) = 0.131. *
26 * THE NUMBER OF ACTIVE QUARK FLAVOURS IS NF = 3 EVERYWHERE *
27 * EXCEPT IN THE BETA FUNCTION, I.E. THE HEAVY QUARKS C,B,... *
28 * ARE NOT PRESENT AS PARTONS IN THE Q2-EVOLUTION. *
29 * IF NEEDED, HEAVY QUARK DENSITIES CAN BE TAKEN FROM THE 1991 *
30 * GRV PARAMETRIZATION. *
31 * *
32 * NLO DISTRIBUTIONS ARE GIVEN IN MS-BAR FACTORIZATION SCHEME *
33 * (SUBROUTINE GRV94HO) AS WELL AS IN THE DIS SCHEME (GRV94DI), *
34 * THE LEADING ORDER PARAMETRIZATION IS PROVIDED BY "GRV94LO". *
35 * *
36 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
37 *
38 *...INPUT PARAMETERS :
39 *
40 * X = MOMENTUM FRACTION
41 * Q2 = SCALE Q**2 IN GEV**2
42 *
43 *...OUTPUT (ALWAYS X TIMES THE DISTRIBUTION) :
44 *
45 * UV = U(VAL) = U - U(BAR)
46 * DV = D(VAL) = D - D(BAR)
47 * DEL = D(BAR) - U(BAR)
48 * UDB = U(BAR) + D(BAR)
49 * SB = S = S(BAR)
50 * GL = GLUON
51 *
52 *...LO PARAMETRIZATION :
53 *
54 *72*********************************************************************
55  SUBROUTINE grv94lo (X, Q2, UV, DV, DEL, UDB, SB, GL)
56  IMPLICIT DOUBLE PRECISION (a - z)
57 *
58 * to avoid variable conflictions, a second keep element is necessary
59 * with the same common block name (see LEPTO2)
60 *
61 
62  COMMON /leptou/ cut(14),lst(40),parl(30),
63  & xlp,ylp,w2lp,q2lp,ulp
64  REAL cut,parl,xlp,ylp,w2lp,q2lp,ulp
65  INTEGER lst
66  SAVE /leptou/
67 
68  INTEGER icount
69  DATA icount/0/
70  mu2 = 0.23
71  lam2 = 0.2322 * 0.2322
72 *HI>>
73  IF(q2.le.mu2) THEN
74  q2=mu2
75  IF(cut(5).lt.q2.and.cut(6).gt.q2.AND.icount.lt.10) THEN
76  icount = icount + 1
77  WRITE(*,*)
78  &'WARNING : GRV94LO predictions are not correct for your setup !'
79  ENDIF
80  s= 0.d0
81  ds=s
82  s2=s
83  s3=s
84  ELSE
85  s = dlog(dlog(q2/lam2) / dlog(mu2/lam2))
86  ds = dsqrt(s)
87  s2 = s * s
88  s3 = s2 * s
89  ENDIF
90 *HI<<
91 *... UV :
92  nu = 2.284 + 0.802 * s + 0.055 * s2
93  aku = 0.590 - 0.024 * s
94  bku = 0.131 + 0.063 * s
95  au = -0.449 - 0.138 * s - 0.076 * s2
96  bu = 0.213 + 2.669 * s - 0.728 * s2
97  cu = 8.854 - 9.135 * s + 1.979 * s2
98  du = 2.997 + 0.753 * s - 0.076 * s2
99  uv = fv(x, nu, aku, bku, au, bu, cu, du)
100 *... DV :
101  nd = 0.371 + 0.083 * s + 0.039 * s2
102  akd = 0.376
103  bkd = 0.486 + 0.062 * s
104  ad = -0.509 + 3.310 * s - 1.248 * s2
105  bd = 12.41 - 10.52 * s + 2.267 * s2
106  cd = 6.373 - 6.208 * s + 1.418 * s2
107  dd = 3.691 + 0.799 * s - 0.071 * s2
108  dv = fv(x, nd, akd, bkd, ad, bd, cd, dd)
109 *... DEL :
110  ne = 0.082 + 0.014 * s + 0.008 * s2
111  ake = 0.409 - 0.005 * s
112  bke = 0.799 + 0.071 * s
113  ae = -38.07 + 36.13 * s - 0.656 * s2
114  be = 90.31 - 74.15 * s + 7.645 * s2
115  ce = 0.0
116  de = 7.486 + 1.217 * s - 0.159 * s2
117  del = fv(x, ne, ake, bke, ae, be, ce, de)
118 *... UDB :
119  alx = 1.451
120  bex = 0.271
121  akx = 0.410 - 0.232 * s
122  bkx = 0.534 - 0.457 * s
123  agx = 0.890 - 0.140 * s
124  bgx = -0.981
125  cx = 0.320 + 0.683 * s
126  dx = 4.752 + 1.164 * s + 0.286 * s2
127  ex = 4.119 + 1.713 * s
128  esx = 0.682 + 2.978 * s
129  udb = fw(x, s, alx, bex, akx, bkx, agx, bgx, cx, dx, ex, esx)
130 *... SB :
131  als = 0.914
132  bes = 0.577
133  aks = 1.798 - 0.596 * s
134  as = -5.548 + 3.669 * ds - 0.616 * s
135  bs = 18.92 - 16.73 * ds + 5.168 * s
136  dst = 6.379 - 0.350 * s + 0.142 * s2
137  est = 3.981 + 1.638 * s
138  ess = 6.402
139  sb = fws(x, s, als, bes, aks, as, bs, dst, est, ess)
140 *... GL :
141  alg = 0.524
142  beg = 1.088
143  akg = 1.742 - 0.930 * s
144  bkg = - 0.399 * s2
145  ag = 7.486 - 2.185 * s
146  bg = 16.69 - 22.74 * s + 5.779 * s2
147  cg = -25.59 + 29.71 * s - 7.296 * s2
148  dg = 2.792 + 2.215 * s + 0.422 * s2 - 0.104 * s3
149  eg = 0.807 + 2.005 * s
150  esg = 3.841 + 0.316 * s
151  gl = fw(x, s, alg, beg, akg, bkg, ag, bg, cg, dg, eg, esg)
152  RETURN
153  END