Turtle ray interactions with the EMC

1
Turtle ray interactions with the EMC

• Tim West
• University of Manchester

2
Outline

• What are turtle rays?
• About the simulated data
• Low energy ring results
• High energy ring results
• Future plans

3
What are turtle rays?

• Coulomb and Bremsstrahlung related processes
  cause e- and e in the beam to move off axis.
• These turtle rays then interact with material
  around the detector the support structure,
  magnets and beam pipe itself.

• This interaction can produce an EM shower which
  is then picked up in the Calorimeter.
• This shower can then add energy to digis produced
  by collisions.

4
About the simulated data

• Results presented here were produced from Monte
  Carlo data simulated in January of this year.
• The number of entries in plots may include events
  which produce no hits in the EMC.
• LER results are for 2000 events per ntuple HER
  results tend to for slightly less due to batch
  jobs timing out.
• Concentrate on the turtle rays produced in
  Coulomb scatters as these cause the most
  background.

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LER results

• Of 2000 events, only 278 produce the 2049 digi
  hits.
• Small number of hits in the endcap are
  concentrated in the inner rings.
• Forward region of barrel has more hits that
  backward region.
• No large variation over phi.

• Primary PEP hits are concentrated around the skew
  quad and quadrupole-2 magnets at front and rear
  ends.
• Large peak at 556cm has a 0.5mm spread.

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HER results
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HER results (continued)

• Of the 1279 events, 676 produce 7016 digis in the
  EMC.
• A further 201 digis come from 80 events which
  have no pep hit there are another 131 events
  with no pep hit or emc digis.
• Large excess of digi hits in the eastern quadrant
  of the detector.
• Slight excess of digis in the top quadrant for
  pep hits further from the IP.
• Peak in hits in endcap pep hits further from
  the IP produce very few hits in the barrel.

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HER results (continued)

• Moving the pep hit closer to the IP increases
  proportion of hits in the barrel (excess in rear
  portion).
• Digi multiplicity increases rapidly as the pep
  hit moves towards the IP, peaking in the region
  of the septum.

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HER results the septum

• Classify septum pep hits as those between 240cm
  and 285cm upstream of IP.

• Fairly small number of hits on the septum very
  high digi multiplicity though.
• Very few hits in the endcap large excess
  towards the rear portion of the barrel.
• Septum hits produce around 30 of the digis in
  the rear portion of the barrel.

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HER results (continued)

• These results are for zone 2 scattering events
  (26-42m upstream of IP).
• Zones 3 (42-66m) and 4 (66m upwards) do not
  appear to show any hits in the region of the
  septum. We also see
• Much lower digi multiplicity (average 1.5 for
  both).
• Large excess in the endcap.
• Slight excess in the rearmost part of the barrel.
• Have only had a preliminary look at zone 3 and 4
  not looked at zone 1 (4-26m upstream) at all
  these are on my to-do list.

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HER results (continued)

• None of these events cause a trigger to fire.
• Average cluster energy is 37/41/44MeV for zone
  2/3/4 number of clusters decreases as zone
  number increases.
• Very few clusters over 100MeV (16/486 over all
  zones).
• Around a third of the digis are on the default
  digi list.
• Average default digi energy is under 10MeV.

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Future plans

• Look at HER zone 0, 1, 3 and 4 turtle rays more
  closely.
• Look at LER zones 0, 1, 2, 3 and 4 turtle rays -
  results here are for zone 5 (62-2196m upstream).
• Look for similarities with single beam data.

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Zone 1 HER coulomb

• No triggers
• Similar digi/cluster energy distribution.

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Zone 1 HER coulomb
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Zone 2 HER coulomb
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Zone 3 HER coulomb
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Zone 4 HER coulomb
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Zone 1
Zone 2