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Beamline determination pp500 GeV W triggered events

Updated on Wed, 2009-07-22 14:45. Originally created by rjreed on 2009-07-22 14:31.

Code is at:

/star/u/rjreed/PPV2009/v3/

 

Issue:  Converges for:

   if (dT2<dmax2)      chi2+=dT2/t->ery2;    else      chi2+=dmax2/t->ery2;
    if (dZ2<dmax2)      chi2+=dZ2/t->erz2;   else      chi2+=dmax2/t->erz2;
 

Does not converge for:

      if ((dT2<dmax2)&&(dZ2<dmax2))          chi2+=(dT2/t->ery2+dZ2/t->erz2);
      else          chi2+=(dmax2/t->ery2+dmax2/t->erz2);
  

But, this statement is supposed to be for pile-up rejection.  One would naively think that a pile-up track is a pile-up track and if it fails either if statement, it should be thrown out.  My tentative hyposthesis is that by connecting the XY plane directly to the Z, the likelihood space becomes just bumpy enough that minimization is difficult.  I have also seen the same problem that Jan did with attempting to fit for all four parameters.  (i.e. it stops in strange places....)  Some MC sets do allow the second fit to work and converge to a sensible answer, but not all.

Beamline parameters where Vx,Vy and Ux,UY were fit seperately.  I used the first (convergent) set of if statements as well.

Errors need to be determined by looking at the various likelihood cross-sections.  This is in progress.

Fill Vx = mx0 Vy = my0 Ux =mdxdz Uy = mdydz
F10383 0.405005 0.000646 0.001701 0.000114
F10398 0.427248 -0.00746 0.001099 0.000145
F10399 0.434087 0.001289 0.001209 0.00008
F10402 0.479919 0.028121 0.001423 0.000464
F10403 0.454957 -0.01918 0.001257 0.000637
F10404 0.451198 -0.01525 0.001459 0.000203
F10407 0.409051 0.001506 0.001193 0.000394
F10412 0.439252 -0.00042 0.001128 0.000119
F10415 0.442824 0.014106 0.001055 0.000197
F10426 0.44813 -0.00453 0.001567 -0.000165
F10434 0.435321 0.004677 0.000962 0.000052
F10439 0.432291 0.007702 0.001233 0.00002
F10448 0.425117 -0.00363 0.001198 0.000193
F10449 0.439622 -0.01586 0.001087 0.000203
F10450 0.438894 0.000237 0.000729 0.000253
F10454 0.446678 0.01145 0.000789 0.000499
F10455 0.462559 -0.00232 0.000876 0.000083
F10463 0.449619 -0.00106 0.001058 0.000255
F10464 0.373674 0.029753 0.00125 0.000524
F10465 0.42788 -0.00266 0.001254 0.000465
F10471 0.429626 0.002497 0.001172 0.000235
F10476 0.435998 0.012893 0.000956 -0.000218
F10478 0.473336 0.024185 0.000278 -0.000369
F10482 0.433083 0.009334 0.001379 -0.000059
F10486 0.456304 0.013027 0.001013 0.000382
F10490 0.438867 0.010093 0.001004 -0.000189
F10494 0.451179 0.012703 0.001149 0.000265
F10505 0.435392 0.010394 0.00113 0.000307
F10507 0.417899 0.000371 0.001226 0.000186
F10508 0.45268 0.017453 0.001445 0.000445
F10517 0.448586 0.031161 0.001269 0.000295
F10525 0.448745 0.017639 0.001356 0.00022
F10526 0.443651 0.002963 0.001442 0.000395
F10527 0.451738 0.002502 0.001163 0.000213
F10528 0.44345 0.008581 0.001137 0.000085
F10531 0.462084 0.021478 0.001564 0.000243
F10532 0.449339 0.018561 0.001528 -0.000007
F10535 0.43659 0.020904 0.001435 0.000388
F10536 0.45284 0.036722 0.000946 0.000228

 

Figure 1:  Vx,Vy at Z = 0 for the beamline both truncated likelihood cases.  Each point represents one fill.  Blue pionts are much closers together and tighter packed.  Minuit converged for every blue point.  It did not converge for any red points.  The average difference between the points found with the two methods is 0.02.

 

In any case, if Minuit doesn't converge the answer is not sensible.  Obviously there must be something else going on with the likelihood space that when we connect the XY plane to the Z, it becomes a problem.  Solution should be to get a working robust potential, which will take care of the outliers without the if statement.  However, given time constraints, perhaps we should use these beam-line parameters while working in parallel.

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