Hi all (especially Flemming I guess), On Fri, 1 Jun 2001 12:22:20 +0200 (MET DST) Erik Jakobsen <jakobsen@hehi03.nbi.dk> wrote concerning ": GBRAHMS": > Hi BRAT's > > I'm trying to make a GBRAHMS vertex distribution similar to a certain > run. That is, a realistic vertex distribution. This is done to make direct comparisons to real data. > I know the run has a gaussian vertex distribution with a > mean = -0.95 and a sigma of 77.16 for |z| <= 20 cm. Therefore I use the > command: > > u/c/spot 0. 0. 0. 0. -0.95 77.16 There seem to be some problem with the the sign of the mean also, since the vertex distribution that Erik get out has a mean of 0.95. > The problem is that by using this command I get a gaussian vertex > distribution over a large interval of z, ... That is, the full gaussian with 95% events in the interval [-153.37, 155.27]. > ... resulting in a heavy loss in statistics, since I'm only using > events with |z| <= 20 cm. This cut then gives less then 60% of the events. > Does anyone know of a way to get a gaussian distribution for a limited > interval in z? The question is really: Can we implement some way of setting absolute limits on the vertex distribution for all kinds of distributions? For example, we could have user/control/spot <meanx> <varx> <meany> <vary> <meanz> <varz> <absolut maxx> <absolut maxy> <absolut maxz> This would be very usefull. Essentially, as far as I can tell, the relevant code in SUBROUTINE GUKINE (file src/user/guxint.F) should be an algorithm like vertexX = vertexY = vertexZ = some_large_number while (|vertexX| > maxX AND |vertexY| > maxY AND |vertexX| > maxZ) if (use_flat_dist) vertexX = meanX + random_number * varX vertexY = meanY + random_number * varY vertexZ = meanZ + random_number * varZ else if (use_gaus_dist) vertexX = gaus(meanX, varX) vertexY = gaus(meanY, varY) vertexZ = gaus(meanZ, varZ) else ... endif done In that way, we'd be able to use all the input events in that limited range, even thoug the distribution extents beyond that. Yours, Christian ----------------------------------------------------------- Holm Christensen Phone: (+45) 35 35 96 91 Sankt Hansgade 23, 1. th. Office: (+45) 353 25 305 DK-2200 Copenhagen N Web: www.nbi.dk/~cholm Denmark Email: cholm@nbi.dk
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