Calibration of the CMS Outer Hadron Calorimeter : an update

1
Calibration of the CMS Outer Hadron Calorimeter
an update

• Include J/y ?µµ and ?(1S) ?µµ physics events
  along with W?µn and Z/g ? µµ events
• Cosmic muon events
• Correct for the missing factor of 2p for the
  integration over azimuthal angle
• Use spectrum from L3CGEN (Prof. Hebbekers code,
  presently in CMSSW)
• Take care of the solid angle coverage of double
  layers in Ring-0

2
Expected calibration accuracy vs Statistics
(reminder)
Uncertainty()
Uncertainty()
Uncertainty()
Ring 0 Ring 1
Ring 2
Statistics Statistics
Statistics

• 10 accuracy is possible with only 50 events in
  Ring 0 and Ring 2, whereas it requires about 90
  events for Ring 1
• 500 events are required for 3-4 accuracy for
  all tiles

3
Muon selection criteria (reminder)

• Assuming low luminosity trigger scenario
• Single muon trigger criterion PT gt 19.0 GeV
• Double muon trigger PT1,T2 gt 7.0 GeV
• Momentum threshold for calibration, PT gt 5.0 GeV
• Trigger efficiency, L1, L3 (including isolation)
  69
• Contribution of Z?µµ is only 10 to that of W?µ?
  and number events are negligible when event is
  triggered by only endcap muon

4
Expected muon (from W and Z) events in 100 pb-1
data
?/f 1 2 3 4
5 6 Average 1 548.9 678.7
619.5 636.4 624.2 507.3 602.5 2
531.0 668.2 615.8 616.0 621.6 502.4
592.5 3 524.7 657.7 643.8 646.7
622.5 496.9 598.7 4 259.4 336.1
321.5 327.1 309.5 263.6 302.9 5
470.8 554.8 544.2 529.5 513.7 471.0
514.0 6 513.3 581.4 606.9 608.7
582.4 542.2 572.5 7 483.4 553.6
551.0 566.1 544.7 489.9 531.5 8
450.1 530.1 538.5 530.9 524.9 473.7
508.0 9 425.9 508.4 520.1 501.8
503.8 452.9 485.5 10 483.2 570.1
556.7 563.4 550.1 514.6 539.7 11
483.9 569.3 560.0 549.6 543.8 489.1
532.6 12 572.6 684.0 669.9 662.0
647.0 602.0 639.6 13 581.3 696.5
679.7 662.7 639.9 591.8 642.0 14
590.6 689.5 668.5 657.3 656.9 606.3
644.8 15 288.5 357.2 336.6 321.7
339.7 303.0 324.5
Z?µµ (10) ?? µµ (6)

• Better than 4 accuracy is achievable with this
  luminosity for all tiles except ?15, where it is
  about 6

• Gain is only 20 by bringing down the pT
  threshold to 5 GeV for these physics channels.
  Not worth to have huge background.

5
Muon from physics process ?(1S) ?µµ and J/? ?µµ ?

• Huge cross section ?(1S) ?µµ (s.Br 40 nb) and
  J/? ?µµ (s.Br 1.3 µb) with ckin(3)4. (using
  default PYTHIA6.4)
• But, momentum spectrum is very soft (selected
  events with PTµ gt3 GeV and ?lt2.5)

• qw

6
Expected muon (from ?(1S) and J/?) events in 100
pb-1 data
?/f 1 2 3 4
5 6 Average 1 89.4
114.91 129.77 135.65 129.86 104.26
117.31 2 65.6 118.83 97.66 122.87
116.24 107.63 104.82 3 90.15 103.64
91.56 131.14 103.00 104.51 104.00 4
41.85 71.04 66.47 65.85 40.94
60.46 57.78 5 91.67 103.52 93.42
87.94 105.23 75.96 92.96 6 87.64
108.09 110.95 91.46 92.63 94.84
97.61 7 96.70 95.95 111.57 88.24
83.30 90.74 94.42 8 90.83
98.63 77.25 88.83 86.12 100.42
90.35 9 72.78 79.67 97.22 71.07
65.79 62.83 74.89 10 88.13 114.82
77.14 113.16 92.93 93.58 96.63
11 68.35 87.04 96.78 78.81 71.90
85.73 81.43 12 90.27 113.75 96.24
101.58 103.39 76.32 96.93 13 82.80
125.93 123.78 92.93 104.58 91.31
103.55 14 84.36 136.45 116.10 82.51
118.54 80.57 103.09 15 55.18 53.85
59.77 49.47 40.27 60.68 53.21

• Muon identification efficiency with trigger is
  60 (need simulation for better estimation)
• Contribution from ?cs and ?bs are also
  included
• Increase statistics by about 20 with respect to
  muons from W and Z decay
• Tevatron results 30 J/? from B decays expect
  more at LHC

• Reduction of PT threshold to 5(6) GeV, increase
  statistics by 40 (60)
• But, production cross section and feed down from
  B-hadron has large uncertainty

7
Low energy run in year 2007

• Momentum spectra of muons from W?µn and Z?mm are
  no factors for the trigger criteria, but the main
  problem is the production cross section
• At 900 GeV, W?µn production cross section reduces
  from 65.6 nb to 1.2 nb
• Similar reduction in Z?mm and onium production too

Need huge data to calibrate HO, which may not be
available
8
HO calibration with cosmic muon
Cosmic ray muon spectrum and emperical formula
for PCos? gt100 GeV (PDG)
Muon flux in CMSSW

• dN/dE function of log(E)
• Angular dependency 1 a(P) cos(q), whereas in
  PDG 1/cos(q)
• Flux rate (Pcos(q) gt 59 GeV) 7.40 ?10-5
  /cm2/s/sr (PDG) ? 5.72 ?10-5
  /cm2/s/sr

9
Cosmic muon flux as a function of accepted
inclination angle

• Large dependency on muon acceptance angle
• Flux intensity would be different for different
  sectors (0,30,60,90 degree) due to different
  solid angle coverage of cosmic muon

• Cosmic muon flux rate decreases by factor 2.4
  (16) for the muon acceptance angle 70 (10) degree
  from a horizontal tile to a vertical tile
• Muon flux does not increase much beyond
  inclination angle greater than 70o, flux rate
  decreases rapidly beyond that

10
Muon flux in Ring-0 tiles

• Take a point, P and surface, A on the surface of
  one layer (Layer-1)
• Take a small area, B (1cm x 1cm) on the surface
  of the second layer (Layer-0)
• Calculate solid angle coverage, W of B with
  respect to P as well as the direction, q
• Integrate over energy, the muon flux for that
  angle, F
• Muon flux passed through area A and B F WB
• Now move A to cover whole surface on Layer-1,
  then Layer-0 to obtain total flux

Layer-1
A
P
Layer-0
B
11
Cosmic ray muon in horizontal tiles / day
?/f 1 2 3 4
5 6 Average 1 1950.5
2747.7 2606.7 2545.7 2545.7 1872.0
2378.1 2 1954.5 2760.9 2619.1
2557.4 2557.4 1876.4 2387.6 3
1965.6 2788.3 2644.2 2581.4 2581.4
1887.0 2408.0 4 846.6 1206.1
1143.5 1116.1 1116.1 812.8 1040.2
5 4901.1 5662.0 5475.7 5398.0
5398.0 6283.2 5519.7 6 5662.0
6541.1 6325.8 6236.1 6236.1 7258.7
6376.6 7 5475.7 6325.8 6117.6
6030.9 6030.9 7019.8 6166.8 8
5398.0 6236.1 6030.9 5945.3 5945.3
6920.3 6079.3 9 5398.0 6236.1
6030.9 5945.3 5945.3 6920.3 6079.3
10 6283.2 7258.7 7019.8 6920.3
6920.3 8055.1 7076.2 11 6523.9
7536.8 7288.7 7185.4 7185.4 8363.6
7347.3 12 8465.1 9779.3 9457.5
9323.4 9323.4 10852.2 9533.5 13 9058.3
10464.7 10120.3 9976.7 9976.7 11612.7
10201.6 14 9729.2 11239.7 10869.8 10715.6
10715.6 12472.8 10957.1 15 5179.0 5983.1
5786.2 5704.2 5704.2 6639.6 5832.7
Muon acceptance angle is 70o

• 1-day is sufficient for 2 accuracy of
  calibration constant

12
Cosmic Ray muon in vertical tiles / day
?/f 1 2 3 4
5 6 Average 1 99.9 176.8
161.5 155.1 155.1 93.4
140.3 2 104.2 181.8 166.4
160.0 160.0 97.4 144.9 3
112.5 194.6 178.0 171.0 171.0
105.4 155.4 4 50.2 88.5
80.8 77.6 77.6 46.7
70.2 5 2062.1 2382.3 2303.9 2271.2
2271.2 2643.6 2322.4 6 2382.3 2752.1
2661.6 2623.8 2623.8 3054.1 2682.9 7
2303.9 2661.6 2574.0 2537.5 2537.5
2953.6 2594.6 8 2271.2 2623.8 2537.5
2501.5 2501.5 2911.7 2557.9 9 2271.2
2623.8 2537.5 2501.5 2501.5 2911.7
2557.9 10 2643.6 3054.1 2953.6 2911.7
2911.7 3389.1 2977.3 11 2744.9 3171.1
3066.7 3023.2 3023.2 3519.0 3091.4 12
3561.6 4114.6 3979.2 3922.8 3922.8
4566.0 4011.2 13 3811.2 4403.0 4258.1
4197.7 4197.7 4886.0 4292.3 14 4093.5
4729.1 4573.4 4508.6 4508.6 5247.9
4610.2 15 2179.1 2517.4 2434.5 2400.0
2400.0 2793.6 2454.1
Muon acceptance angle is 70o

• 5 accuracy requires at least four days of cosmic
  data to calibrate Ring-0 h4

13
Conclusion

• 4 accuracy in HO calibration constant is
  achievable with 100 pb-1 data
• Muon from ?(1S) and J/? can reduce uncertainty,
  but these processes have large uncertainty in
  production cross-sections
• One day cosmic muon run gives much better
  accuracy in Ring-1 and Ring-2, whereas for
  Ring-0, ?-4, one need at least 4 days
• HO calibration with cosmic muon demands muon
  trigger with large inclination, large solid angle
  coverage
• In the year 2007, a cosmic muon calibration is
  absolutely necessary, data from pp collisions
  will take longer time to achieve a reasonable
  accuracy, where as later on (2008 onwards), data
  from pp collisions will be sufficient to
  calibrate HO.

Remaining issues

• Recalculate all numbers using CMSSW (full
  detector simulation)