Brick Finding

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Brick Finding Ankara CM 2/4/2009 Dario Autiero
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• A large effort was put in the last months by a
  team of people in order to recover the events
  pending due to reconstruction problems and to
  improve the ED reconstruction
• See presentations by Antoine and Anselmo
• We had the goals
• Solve all the 2008 events before the 2009 run
• Improve the reconstruction and efficiency
• Have a more reliable reconstruction (more
  automatic)
• The events which were suspended, about 300 at the
  end of 2008 had evident reconstruction problems
  bringing predictions many tents of cm away from
  the core activity of the event
• We managed to digest the pending events by
  completing the debugging of the reconstruction
• Once fixed the events behave more or less like
  the standard ones, we did not observe a
  degradation of efficiency for recovered events
  wrt standard one
• Many problems were fixed at the level of the
  spectrometer connection, RPC clustering etc

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Still pending problems Having an independent
(and precise) pattern recognition at the level of
the HPT (the actual onedoes not exploit the
accuracy of HPT and does not well correct for the
magnetic field) Having a correct treatment of
tracking errors (Claudia, Anselmo and Stefano) ?
see next page All these improvements are
necessary also for other aspects in the
experiment, like the muon ID and not only for the
BF. We also started a comparison with a TT
pattern recognition based on the Hough transform,
provided by Dubna. This process was launched at
the September CM. A file in the standard Oprec
root format was finally available two weeks
ago ? Two presentations are foreseen in the PC
session
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Residual Kalman-CS
19 mrad
20 mrad
7 mm
8 mm
Typical tracking errors are of the order of 1mm,
one order of magnitude smaller this is a
long-standing problem
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First and Second bricks Getting data from second
bricks to complete efficiency estimation from
real data. At the moment still poor statistics of
2nd bricks (data from EU only)
Last data First bricks raw eff 467/715 65.3
Second bricks raw eff 29/65 44.6 Removal
of interactions in dead materials 715 - 3.8
688 ? 1st brick corrected eff 467/688 / (1
-6.8) 72.8 (72 MC) Correlation with 2nd
brick Unfound raw after first brick (100 -
65.3) Unfound related to BF inefficiency (100
- 72.8) foundable in 2nd brick ? Second brick
corrected eff 29/65 (100 65.3) / ( 100 -
72.8) 56.9 1st brick BF eff 72.8 -
1.7 2nd brick BF eff 56.9 - 6.1 Total
efficiency 1st 2nd 72.8 (100 -
72.8)56.9 88.3 - 5 (80 MC) Still too
large uncertainty on 2nd bricks
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• Comments and warnings
• Predictions were made time ago for these events.
  Taking the latest version of the reconstruction
  for about 1/3 (9 events) now the brick is
  predicted directly as first brick, reconstruction
  problems fixed
• For 8 events the second brick suffers from the
  underestimation of tracking errors. This has to
  be fixed in order to predict correctly the
  lateral probability
• For 8 events the second brick was in another
  wall with large probability (30-40), this looks
  higher ( a factor 2) than on average prediction
  for second bricks. It is a fluctuation in this
  first sample
• Too few NC
• We need a larger sample to draw some more solid
  conclusions
• We should get a large sample from the last couple
  of weeks of extractions

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Wall 14 (first) 60 Wall 15 40 Important
backscattering
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• We should have a clearer view with the increase
  in statistics of the last weeks (gather all
  possible second brick results, also from Japan)
• Re-evaluation of last version of the
  reconstruction on all events
• A deeper comparison per events categories is
  needed (QE,NC,CC, electromagnetic-like)
• So far the algorithms have been kept untouched,
  the main work has been concerning the debugging
  of the reconstruction. On the basis of these
  results it will be possible to have a second
  version
• BF efficiency was optimized for tau events (the
  efficiency is about 5 larger than for standard
  numu NC or CC events) , in order to check it we
  should look for events which are tau like CC QE
  and with low energy muons, events with dominant
  electromagnetic activity, like tau?e and tau?rho.
• First priority increase the efficiency as much
  as possible, There are ideas about that on the
  side of BF and also on the possibility of
  concentrating the efforts on a tau signal
  enriched sample. We should first advance with the
  analysis of the event sample and understand why
  it goes wrong (reconstruction, 2nd bricks, )

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Re-evaluation campaign (bricks finding CS tagging
part)
Integrate in the simulation the CS tagging absent
in the past acceptance effect with respect to
the total surface behind the bricks (7.4
uncovered area) CS base track
efficiencies measured from real data, implement
also the 3/4) ? Complete efficiency evaluation
from real data (convolution of BF CS) ?
Evaluate CS tagging efficiency from full MC
(including the CS intrinsic efficiency as a
function of the angle measured in real data,
provided by Giovanni for base tracks)
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• ? Better errors evaluation in tracking, important
  for probability maps
• Re-evaluate MC BF efficiency per categories of
  event including the interplay of CS tagging
  efficiency, compare to data per categories of
  events DIS, QE, NC, NC with e.m. component.
• Possible tau enriched sample to maximize the
  efficiency
• ? Estimate possible bias of CS tagging
  inefficiency ( 25) on muon matching are all
  muons found at the vertex even if not followed by
  scan-back ? even a residual inefficiency of 2
  could change a lot the charm background.