People, As an undergraduate in the Science and Engineering Research Semester (SERS) at BNL in 1993, I wrote proof of concept code to demonstrate Cherenkov rings could be identified using the original proposed 4x4 array of 10cmx10cm 1cmx1cm segmented Hamamatsu RICH. Plots from my code were included in "In-beam Tests of a Ring Imaging Cerenkov Detector With a Multianode Photomultiplier Readout", R. Debbe, et. al., Nuclear Instruments and Methods in Physics Research A 362 (1995) 253-260. This paper can be found at: http://xxx.lanl.gov/abs/hep-ex/9503006 If someone wants the code, which consists of 1 big Fortran77 routine and a bunch of PAW macros, I can send it to them. It would have to be modified somewhat because the geometry of the RICH has changed, but I think writing new code from the ground up is unnecessary. I would be happy to modify the code myself - reading other people's code can be a tremendous pain in the derriere, and I'm not so arrogant to think that mine would be any better for someone else. > ---------- > From: Michael Murray > Reply To: brahms-l@bnl.gov > Sent: Friday, September 7, 2001 12:05 PM > To: brahms-l@bnl.gov > Subject: Optical Algorithm for RHIC PID > > Dear Claus, > Julia Thompson of Pittsburgh used > the following optical algorithm to find the > center of cerenkov rings. In her day she was > looking for particles of fixed momenta and so > she could use a dispersive lens rather than a > computer. > > All points on a ring are equal distance from the > center. So if you have a track of momentum P you > want to look for rings of radii Rpi(P) or Rk(P) > with centers near the expected intercept with > the detector. So to look for pions take all pixels > within a reasonable area of the intercept and > look for hits. When you find a hit "disperse" the > signal from that hit to all pixels on a circle > of radiu Rpi(P) from that one. (Of course on the > computer you do this with an array that holds > the dispersed signal). Repeat this for all N hits > on the grid. If the particle was a pion then > there will be a pixel where N rings will overlap. > This will show up as a maximium in the array. > However if the particle was a kaon the N rings > will never overlap unless you repeat the search > using the radius Rk(P). > This method has the advantage that it give the > location of the center of the ring independently > of the track. > > Of course you can also use the magnitude of > the signal. > Nphoton ~= K*(1-(Pthreshold/P)^2) > For kaons (Pthreshold/P)^2 = (mK/mpi)^2 = 12.5 > times larger than for pions. > > Yours Michael > > > > Quoting "Claus O. E. Jorgensen" <ekman@nbi.dk>: > > > > > Dear Collaborators, > > > > Thanks to Pawels new Bfs tracking and Djamels calculation > > of reflections on the Rich mirror I've been able to do the > > first rough pid with the Rich. > > > > You can find plots on the web: > > > > http://www.nbi.dk/~ekman/rich/RICH.html > > > > I can think of (at least) 4 things that can improve the RICH pid: > > > > 1) Align the geometry of the detector. For now I just use an > > old geo file. I don't know how to tune the geometry. The > > calculated ring centers (reflection of the track lines) > > seems to hit in the center of the rings, but since I find > > the rings from the center it's difficult to check the > > correlation. > > > > 2) Implement the correct geometry of the image plane. The tube > > positions is given by BrChkvParameters, and they are only > > approximate - there are some offsets missing - who knows the > > exact geometry? > > > > 3) Make gain calibrations. Maybe we can find a single photon > > peak in the raw data (or in events with only one track), > > and calibrate to that. I'll look at that. > > > > 4) Improve the ring-finding method. For know I just make a > > histogram of signals per dR (R=distance from center) and > > normalize to the area of the dR rings - this histogram > > is then fitted with a gaussian, and in most cases a nice > > peak is found. The ring radius is then set to mean of the > > peak. Maybe we can use some more sophisticated recognition > > routines (any ideas?) > > > > Any comments or suggestions are welcome! > > > > Have a nice weekend, > > > > Claus > > > > +-------------------------------------------------------------+ > > | Claus Jørgensen | > > | Cand. Scient. Phone : (+45) 33 32 49 49 | > > | Cell : (+45) 27 28 49 49 | > > | Niels Bohr Institute, Ta-2, Office : (+45) 35 32 53 07 | > > | Blegdamsvej 17, DK-2100, E-mail : ekman@nbi.dk | > > | University of Copenhagen Home : www.nbi.dk/~ekman/ | > > +-------------------------------------------------------------+ > > > > > > Michael Murray, Cyclotron TAMU, 979 845 1411 x 273, Fax 1899 > Have a care, James Norris PS Please note my NEW home address & phone and email address below: ------------------------------------------------------------------------ University of Kansas email: jnorris@ku.edu Dept of Physics & Astronomy Phone: 785-864-4889 Malott Hall Rm#B008 Lawrence KS 66045 FAX: 785-864-5262 Home Address: 810 Ash St Wamego KS 66547 Home Phone: 785-456-7059 ------------------------------------------------------------------------ | WWW Homepage: www.people.ku.edu/~jnorris/ | ------------------------------------------------------------------------ | Perhaps we are the first to talk and think and build and aspire, but | | we may not be the last. Others may follow us in this adventure... | | We owe it to that possible future to let their potential survive. | ---------------------------| David Brin |----------------------------
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