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	subroutine musc_ext(m2,p,rad_len,x_len,dth,dph,y,x)
C+_____________________________________________________________________
!
! MUSC - Simulate multiple scattering of any particle.
!        Used for extended scatterers.
!
! According to Particle Data Booklet, July 1994
!
C-_____________________________________________________________________

	implicit none

	real*8 Es, epsilon
	parameter (Es = 13.6)		!MeV
	parameter (epsilon = 0.088)

	real*8 rad_len, x_len, dth, dph, x, y
	real*8 beta, g1, g2, theta_sigma
	real*8 m2, p

	real*8 nsig_max
	parameter(nsig_max=99.0d0)      !max #/sigma for gaussian ran #s.

	real*8 gauss1

	if (rad_len.eq.0) return
	if (x_len.le.0 .or. rad_len.lt.0) then
	  write(6,*) 'x_len or rad_len < 0 in musc_ext.f'
	  write(6,*) 'This is bad.  Really bad.  Dont even ask how bad it is.'
	  write(6,*) 'Just fix it now.'
	  stop
	endif
	if (p.lt.10.) write(6,*)
     >    'Momentum passed to musc_ext.f should be in MeV, but p=',p

	beta = p / sqrt(m2+p*p)
	theta_sigma = Es/p/beta * sqrt(rad_len) * (1+epsilon*log10(rad_len))

! Compute new trajectory angles and displacements (units are rad and cm)

	g1 = gauss1(nsig_max)	! gaussian, truncated at 99 sigma
	g2 = gauss1(nsig_max)
	dth = dth + theta_sigma*g1
	x   = x   + theta_sigma*x_len*g2/sqrt(12.) + theta_sigma*x_len*g1/2.

	g1 = gauss1(nsig_max)	! gaussian, truncated at 99 sigma
	g2 = gauss1(nsig_max)
	dph = dph + theta_sigma*g1
	y   = y   + theta_sigma*x_len*g2/sqrt(12.) + theta_sigma*x_len*g1/2.

	return
	end