hijing/src/pyhixtot.f

0001
0002 C*********************************************************************
0003
0004       SUBROUTINE PYHIXTOT
0005
0006 C...Parametrizes total, double diffractive, single diffractive and
0007 C...elastic cross-sections for different energies and beams.
0008       COMMON/LUDAT1/MSTU(200),PARU(200),MSTJ(200),PARJ(200)
0009       SAVE /LUDAT1/
0010       COMMON/PYHIPARS/MSTP(200),PARP(200),MSTI(200),PARI(200)
0011       SAVE /PYHIPARS/
0012       COMMON/PYHIINT1/MINT(400),VINT(400)
0013       SAVE /PYHIINT1/
0014       COMMON/PYHIINT5/NGEN(0:200,3),XSEC(0:200,3)
0015       SAVE /PYHIINT5/
0016       DIMENSION BCS(5,8),BCB(2,5),BCC(3)
0017
0018 C...The following data lines are coefficients needed in the
0019 C...Block, Cahn parametrization of total cross-section and nuclear
0020 C...slope parameter; see below.
0021       DATA ((BCS(I,J),J=1,8),I=1,5)/
0022      1 41.74, 0.66, 0.0000, 337.,  0.0, 0.0, -39.3, 0.48,
0023      2 41.66, 0.60, 0.0000, 306.,  0.0, 0.0, -34.6, 0.51,
0024      3 41.36, 0.63, 0.0000, 299.,  7.3, 0.5, -40.4, 0.47,
0025      4 41.68, 0.63, 0.0083, 330.,  0.0, 0.0, -39.0, 0.48,
0026      5 41.13, 0.59, 0.0074, 278., 10.5, 0.5, -41.2, 0.46/
0027       DATA ((BCB(I,J),J=1,5),I=1,2)/
0028      1 10.79, -0.049, 0.040, 21.5, 1.23,
0029      2  9.92, -0.027, 0.013, 18.9, 1.07/
0030       DATA BCC/2.0164346,-0.5590311,0.0376279/
0031
0032 C...Total cross-section and nuclear slope parameter for pp and p-pbar
0033       NFIT=MIN(5,MAX(1,MSTP(31)))
0034       SIGP=BCS(NFIT,1)+BCS(NFIT,2)*(-0.25*PARU(1)**2*
0035      &(1.-0.25*BCS(NFIT,3)*PARU(1)**2)+(1.+0.5*BCS(NFIT,3)*PARU(1)**2)*
0036      &(LOG(VINT(2)/BCS(NFIT,4)))**2+BCS(NFIT,3)*
0037      &(LOG(VINT(2)/BCS(NFIT,4)))**4)/
0038      &((1.-0.25*BCS(NFIT,3)*PARU(1)**2)**2+2.*BCS(NFIT,3)*
0039      &(1.+0.25*BCS(NFIT,3)*PARU(1)**2)*(LOG(VINT(2)/BCS(NFIT,4)))**2+
0040      &BCS(NFIT,3)**2*(LOG(VINT(2)/BCS(NFIT,4)))**4)+BCS(NFIT,5)*
0041      &VINT(2)**(BCS(NFIT,6)-1.)*SIN(0.5*PARU(1)*BCS(NFIT,6))
0042       SIGM=-BCS(NFIT,7)*VINT(2)**(BCS(NFIT,8)-1.)*
0043      &COS(0.5*PARU(1)*BCS(NFIT,8))
0044       REFP=BCS(NFIT,2)*PARU(1)*LOG(VINT(2)/BCS(NFIT,4))/
0045      &((1.-0.25*BCS(NFIT,3)*PARU(1)**2)**2+2.*BCS(NFIT,3)*
0046      &(1.+0.25*BCS(NFIT,3)*PARU(1)**2)+(LOG(VINT(2)/BCS(NFIT,4)))**2+
0047      &BCS(NFIT,3)**2*(LOG(VINT(2)/BCS(NFIT,4)))**4)-BCS(NFIT,5)*
0048      &VINT(2)**(BCS(NFIT,6)-1.)*COS(0.5*PARU(1)*BCS(NFIT,6))
0049       REFM=-BCS(NFIT,7)*VINT(2)**(BCS(NFIT,8)-1.)*
0050      &SIN(0.5*PARU(1)*BCS(NFIT,8))
0051       SIGMA=SIGP-ISIGN(1,MINT(11)*MINT(12))*SIGM
0052       RHO=(REFP-ISIGN(1,MINT(11)*MINT(12))*REFM)/SIGMA
0053
0054 C...Nuclear slope parameter B, curvature C:
0055       NFIT=1
0056       IF(MSTP(31).GE.4) NFIT=2
0057       BP=BCB(NFIT,1)+BCB(NFIT,2)*LOG(VINT(2))+
0058      &BCB(NFIT,3)*(LOG(VINT(2)))**2
0059       BM=BCB(NFIT,4)+BCB(NFIT,5)*LOG(VINT(2))
0060       B=BP-ISIGN(1,MINT(11)*MINT(12))*SIGM/SIGP*(BM-BP)
0061       VINT(121)=B
0062       C=-0.5*BCC(2)/BCC(3)*(1.-SQRT(MAX(0.,1.+4.*BCC(3)/BCC(2)**2*
0063      &(1.E-03*VINT(1)-BCC(1)))))
0064       VINT(122)=C
0065
0066 C...Elastic scattering cross-section (fixed by sigma-tot, rho and B).
0067       SIGEL=SIGMA**2*(1.+RHO**2)/(16.*PARU(1)*PARU(5)*B)
0068
0069 C...Single diffractive scattering cross-section from Goulianos:
0070       SIGSD=2.*0.68*(1.+36./VINT(2))*LOG(0.6+0.1*VINT(2))
0071
0072 C...Double diffractive scattering cross-section (essentially fixed by
0073 C...sigma-sd and sigma-el).
0074       SIGDD=SIGSD**2/(3.*SIGEL)
0075
0076 C...Total non-elastic, non-diffractive cross-section.
0077       SIGND=SIGMA-SIGDD-SIGSD-SIGEL
0078
0079 C...Rescale for pions.
0080       IF(IABS(MINT(11)).EQ.211.AND.IABS(MINT(12)).EQ.211) THEN
0081         SIGMA=4./9.*SIGMA
0082         SIGDD=4./9.*SIGDD
0083         SIGSD=4./9.*SIGSD
0084         SIGEL=4./9.*SIGEL
0085         SIGND=4./9.*SIGND
0086       ELSEIF(IABS(MINT(11)).EQ.211.OR.IABS(MINT(12)).EQ.211) THEN
0087         SIGMA=2./3.*SIGMA
0088         SIGDD=2./3.*SIGDD
0089         SIGSD=2./3.*SIGSD
0090         SIGEL=2./3.*SIGEL
0091         SIGND=2./3.*SIGND
0092       ENDIF
0093
0094 C...Save cross-sections in common block PYPARA.
0095       VINT(101)=SIGMA
0096       VINT(102)=SIGEL
0097       VINT(103)=SIGSD
0098       VINT(104)=SIGDD
0099       VINT(106)=SIGND
0100       XSEC(95,1)=SIGND
0101
0102       RETURN
0103       END