Hi Steve et al, On Sat, 24 Nov 2001 18:21:46 -0600 "Stephen J. Sanders" <ssanders@ku.edu> wrote concerning "Re: BRAT-2-1-40, dNdEta calculations added": > Hi Christian, > > > > >We should register the two new parameter sets with the database too. > >Please read the DB info avaliable from [1] and in "The Guide". > > > It turns out to be awkward for me to use the database since I still can only > access it by running on the rcas machines--where I have very poor response > using editors and such. Come wednesday, you can use your Mac for DB access. BTW, what do think it's like to work on the rcas over the atlantic? > Once I can access the db on my local machines (all PPC) Well, if you like to spend that extra money - good for you. > I work on getting the parameters located properly. I'll probably need > you help with this. It's fairly simple. I think I wrote you a mail sometime ago on how to doit. > >Why do you add 50 to the ADC gap in the Tiles? Why don't you simply > >add those 50 to the calibration numbers? > > > >Remember, hardcoded constants are BAAAD. Calibration paramters in the > >database is GOOD. > > > >>We were already calculating the number of "primary" particles > >>hitting each detector element based on HIJING simulations that > >>relate these particle multiplicites to the observed energy deposited > >>in each si and tile element. I have now added calibrations that > >>relate the particle multiplicites to a dNdEta value based on the > >>measured vertex position. To obtain the calibrations I position a > >>simulated vertex between -46 cm and +46 cm, in 2 cm steps, and at > >>each position did a "throw" of HIJING 0-2 fm primary events (no > >>CASCADE...). Each particle was checked to see if it hit on the si > >>or tile detectors. I also kept track of the total number of > >>particles within the pseudorapity range covered by each > >>detector. This procedure allows for a simple geometric efficiency > >>calculation. > >> > > > >Why the do we need this extra conversion from single element > >multiplicity to ring multiplicity? Are the conversion functions > >not enough? > > The single element multiplicities only give the number of particle > hitting each element. The new calculation is intended to develop > the dNdeta value taking into account the geometry details. Are you talking about the geometrical acceptance? In that case, I believe you can calculate that from data and pure geometrical principels, as I briefly outlined in the previous mail. The thing is, that we're up to some 4-5 corrections/conversions - of which at least 2 are based on simulations, all parameterised in some high-order polynomials - frankly, I'm having a hard time figuring out what they're all about. > >I'm not sure I understand this "Hijing-weighted mean > >pseudo-rapidity". Could you please explain what that is. And what's > >the difference between that, and the one calculated by > >BrMultRdoModule::CalibrateEta()? It seems that it's (again) some > >parameterisation, but why is that needed? Since you know the z > >position of the ring (r_z), the distance of the ring to the beam (d), > >and the z-position of the primary vertex, I should think that the eta > >would simply be: > > > The particles are not uniformly distributed over each si/tile > element. Therefore, using the geometry of the element we can obtain > the eta value associated with the geometric center, but this is > different from the average eta value for particles hitting the > detector. I'm interested in this latter value. Well, of course the particles are not uniformly distributed, but I see no reason to believe that they should be distributed like Hijing/BRAG says. I think you'd be much better off by calculating a weight factor based on the geometry rather than simulation. Yours, Christian Holm Christensen ------------------------------------------- Address: Sankt Hansgade 23, 1. th. Phone: (+45) 35 35 96 91 DK-2200 Copenhagen N Cell: (+45) 28 82 16 23 Denmark Office: (+45) 353 25 305 Email: cholm@nbi.dk Web: www.nbi.dk/~cholm
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