Turtle ray interactions Turtle ray interactions with the EMCwith the EMC

Tim WestTim West

University of ManchesterUniversity of Manchester

OutlineOutline

What are turtle rays?What are turtle rays? About the simulated dataAbout the simulated data Low energy ring resultsLow energy ring results High energy ring resultsHigh energy ring results Future plansFuture plans

What are turtle rays?What are turtle rays?

• Coulomb and Coulomb and Bremsstrahlung related processes Bremsstrahlung related processes cause cause ee−− and and ee++ in the beam to move off axis. in the beam to move off axis.

• These ‘turtle rays’ then interact with material These ‘turtle rays’ then interact with material around the detector; the support structure, around the detector; the support structure, magnets and beam pipe itself.magnets and beam pipe itself.

• This interaction can This interaction can produce an EM produce an EM shower which is then shower which is then picked up in the picked up in the Calorimeter.Calorimeter.

• This shower can This shower can then add energy to then add energy to digis produced by digis produced by collisions.collisions.

About the simulated dataAbout the simulated data

• Results presented here were produced Results presented here were produced from Monte Carlo data simulated in from Monte Carlo data simulated in January of this year.January of this year.

• The number of entries in plots may include The number of entries in plots may include events which produce no hits in the EMC.events which produce no hits in the EMC.

• LER results are for 2000 events per ntuple; LER results are for 2000 events per ntuple; HER results tend to for slightly less due to HER results tend to for slightly less due to batch jobs timing out.batch jobs timing out.

• Concentrate on the turtle rays produced in Concentrate on the turtle rays produced in Coulomb scatters as these cause the most Coulomb scatters as these cause the most background.background.

LER resultsLER results• Of 2000 events, only Of 2000 events, only

278 produce the 2049 278 produce the 2049 digi hits.digi hits.

• Small number of hits in Small number of hits in the endcap are the endcap are concentrated in the concentrated in the inner rings.inner rings.

• Forward region of barrel Forward region of barrel has more hits that has more hits that backward region.backward region.

• No large variation over No large variation over phi.phi.

• Primary PEP hits are concentrated around the skew Primary PEP hits are concentrated around the skew quad and quadrupole-2 magnets at front and rear quad and quadrupole-2 magnets at front and rear ends.ends.

• Large peak at 556cm – has a 0.5mm spread.Large peak at 556cm – has a 0.5mm spread.

HER resultsHER results

HER results (continued)HER results (continued)

• Of the 1279 events, 676 produce 7016 digis in Of the 1279 events, 676 produce 7016 digis in the EMC.the EMC.

• A further 201 digis come from 80 events which A further 201 digis come from 80 events which have no pep hit; there are another 131 events have no pep hit; there are another 131 events with no pep hit or emc digis.with no pep hit or emc digis.

• Large excess of digi hits in the eastern quadrant Large excess of digi hits in the eastern quadrant of the detector.of the detector.

• Slight excess of digis in the top quadrant for pep Slight excess of digis in the top quadrant for pep hits further from the IP.hits further from the IP.

• Peak in hits in endcap – pep hits further from the Peak in hits in endcap – pep hits further from the IP produce very few hits in the barrel.IP produce very few hits in the barrel.

HER results (continued)HER results (continued)

• Moving the pep hit closer Moving the pep hit closer to the IP increases to the IP increases proportion of hits in the proportion of hits in the barrel (excess in rear barrel (excess in rear portion).portion).

• Digi multiplicity increases Digi multiplicity increases rapidly as the pep hit rapidly as the pep hit moves towards the IP, moves towards the IP, peaking in the region of peaking in the region of the septum.the septum.

PEP region (cm)PEP region (cm) NNEMCEMC NNPEPPEP NNEMC EMC /N/NPEPPEP

z<-470z<-470 517517 256256 2.52.5

-470<z<-350-470<z<-350 14101410 217217 7.17.1

-350<z-350<z 50895089 191191 26.626.6

SeptumSeptum 14281428 3535 40.840.8

HER results – the septumHER results – the septum• Classify septum pep hits as those between 240cm Classify septum pep hits as those between 240cm

and 285cm upstream of IP.and 285cm upstream of IP.

• Fairly small number of Fairly small number of hits on the septum – hits on the septum – very high digi very high digi multiplicity though.multiplicity though.

• Very few hits in the Very few hits in the endcap – large excess endcap – large excess towards the rear towards the rear portion of the barrel.portion of the barrel.

• Septum hits produce Septum hits produce around 30% of the around 30% of the digis in the rear digis in the rear portion of the barrel.portion of the barrel.

HER results (continued)HER results (continued)• These results are for zone 2 scattering events (26-These results are for zone 2 scattering events (26-

42m upstream of IP).42m upstream of IP).

• Zones 3 (42-66m) and 4 (66m upwards) do not Zones 3 (42-66m) and 4 (66m upwards) do not appear to show any hits in the region of the appear to show any hits in the region of the septum. We also see:septum. We also see:

oMuch lower digi multiplicity (average ~1.5 for Much lower digi multiplicity (average ~1.5 for both).both).

oLarge excess in the endcap.Large excess in the endcap.

oSlight excess in the rearmost part of the barrel.Slight excess in the rearmost part of the barrel.

• Have only had a preliminary look at zone 3 and 4; Have only had a preliminary look at zone 3 and 4; not looked at zone 1 (4-26m upstream) at all – not looked at zone 1 (4-26m upstream) at all – these are on my to-do list.these are on my to-do list.

HER results (continued)HER results (continued)• None of these events cause a trigger to fire.None of these events cause a trigger to fire.

• Average cluster energy is 37/41/44MeV for zone 2/3/4; Average cluster energy is 37/41/44MeV for zone 2/3/4; number of clusters decreases as zone number increases.number of clusters decreases as zone number increases.

• Very few clusters over 100MeV (16/486 over all zones).Very few clusters over 100MeV (16/486 over all zones).• Around a third of the digis are on the default digi list.Around a third of the digis are on the default digi list.• Average default digi energy is under 10MeV.Average default digi energy is under 10MeV.

Future plansFuture plans

o Look at HER zone 0, 1, 3 and 4 turtle rays more Look at HER zone 0, 1, 3 and 4 turtle rays more closely.closely.

o Look at LER zones 0, 1, 2, 3 and 4 turtle rays - Look at LER zones 0, 1, 2, 3 and 4 turtle rays - results here are for zone 5 (62-2196m upstream).results here are for zone 5 (62-2196m upstream).

o Look for similarities with single beam data.Look for similarities with single beam data.

Zone 1 HER coulomb Zone 1 HER coulomb Pep hit z/cmPep hit z/cm NNEMCEMC NNPEPPEP NNEMCEMC/N/NPEPPEP

z<-470z<-470 56 (517)56 (517) 20 (256)20 (256) 2.8 (2.5)2.8 (2.5)

-470<z<--470<z<-350350

252 (1410)252 (1410) 35 (217)35 (217) 7.2 (7.1)7.2 (7.1)

-350<z-350<z 19497 19497 (5089)(5089)

693 693 (191)(191)

28.1 28.1 (26.6)(26.6)

SeptumSeptum 1752 (1428)1752 (1428) 48 (35)48 (35) 36.5 36.5 (40.8)(40.8)

• No triggersNo triggers

• Similar Similar digi/cluster digi/cluster energy energy distribution.distribution.

Zone 1 HER coulomb Zone 1 HER coulomb

Zone 2 HER coulomb Zone 2 HER coulomb

Zone 3 HER coulomb Zone 3 HER coulomb

Zone 4 HER coulomb Zone 4 HER coulomb

Zone 1Zone 1 Zone 2Zone 2