A study of energy deficit observed in E949
  1. We observed a Kp2 energy shift in E949 with the latest RS energy calibration. The results are from single Gaussian fit and the expected Kp2 energy is 108.5 MeV.
    2. Year 2002 1998 UMC Expected
    Peak (MeV) 102.8±0.01 105.1±0.01 105.9±0.02 108.5
  1. By separating the Kp2 energy contributions from the Range Stack and the target+I-counter and comparing to the expected values from UTC , we conclude that this energy deficit observed in E949 is completely from the Range Stack measurement. Benefiting from SWATHCCD, part of pion energy deposit in the kaon fiber has been recovered, giving less energy deficit in the target energy measurement for the 2002 data.
    2. Year E_exp-E_meas for Target+IC (MeV) E_exp-Emeas for Range Stack (MeV)
    2002 1.92±0.02 3.98±0.03
    1998 2.58±0.01  0.80±0.02
    UMC 2.31±0.04 0.40±0.04
    Expected 0.0 0.0
  2. A comparison study is then conducted using the piscat monitors. For a technically reason, we can only compare the 2002 data to the 1997 data. The E(meas)/E(exp), the ratio of E(meas)/E(exp) between the 2002 data and the 1997 data and the resolution of the E(meas)/E(exp) as a function of the Range Stack layer show some interesting results.  a) The energy measured in each layer doesn't include the energy loss in the inactive material, but the expected energy from the range does, resulting in the E(meas)/E(exp) values give somewhat smaller than the expected one. The ratio plot indicates a clearly problematic energy measurement  especially from layer#6 to layer# 11, which agrees on Tetsuro's muon energy study  in the stopping counter.  For the rest layers, the difference is around 1-2% level.  The improved energy measurement in the new inner 5 layers in the 2002 data and the aging effect for the rest layers are consistent with what we expected.
    3. Layer# 2002 1997 1997/2002
    1 0.9136 0.8889 0.9729
    2 0.9520 0.9613 1.0097
    3 0.9476 0.9660 1.0193
    4 0.9452 0.9638 1.0196
    5 0.9424 0.9602 1.0188
    6 0.9327 0.9655 1.0351
    7 0.9371 0.9747 1.0401
    8 0.9375 0.9822 1.0477
    9 0.9397 0.9799 1.0428
    10 0.9342 0.9838 1.0531
    11 0.9504 0.9806 1.0317
    12 0.9456 0.9568 1.0117
    13 0.9422 0.9563 1.0149
    14 0.9301 0.9358 1.0060
    15 0.9517 0.9613 1.0101
    16 0.9424 0.9524 1.0106
    17 0.9154 0.9497 1.0374
    18 1.0112 0.9998 0.9887
  3. A comparison of the mean muon energy deposit in each layer is also performed by using the UMC Km22 samples. In Shaomin's study, the layers involving a crossing sectors are not included.
    4. Layer # Benji's Mean SM's Mean  SM's Fit 98 Mean  98 SM's Mean SM's Mean (98 BM) 
    1 1.420 1.433 1.336 1.397 1.422 1.424
    2 4.346 4.352 4.176 4.182 4.350 4.302
    3 4.400 4.410 4.238 4.253 4.397 4.337
    4 4.456 4.454 4.272 4.304 4.434 4.411
    5 4.503 4.508 4.345 4.347 4.484 4.444
    6 4.581 4.611 4.436 4.416 4.555 4.538
    7 4.650 4.673 4.513 4.498 4.643 4.607
    8 4.748 4.767 4.620 4.589 4.708 4.681
    9 4.836 4.870 4.732 4.651 4.804 4.797
    10 4.925 4.962 4.831 4.746 4.869 4.896
    11 5.188 5.237 5.162 4.847 5.132 5.081
    12 5.323 5.359 5.301 4.854 5.257 5.247
    13 5.527 5.565 5.510 5.038 5.548 5.379
    14 5.691 5.746 5.702 5.077 5.650 5.500
    15 6.257 6.339 6.338 5.470 6.195 5.983
    16 6.637 6.739 6.752 5.647 6.477 6.284
    17 7.147 7.305 7.308 5.911 6.942 6.670
    18 8.224 8.455 8.452 6.333 7.802 7.467
    19 4.694 5.044 4.706 6.756 9.004 4.197
  4. A comparison of energy deposit in each layer is also done for the km22 monitor. To get rid of the beam file effect, we only study the events with |cos3d|<0.1 and |sqrt(tgx^2+tgy^2)-3.5|<0.5 cm. The plots also indicate a somewhat calibration problem, but the amount is pretty small and can not fully account for the kp2 energy deficit.
  5. The RS energy calibration uses km22 monitors. It gets the average muon energy deposit (in the unit of ADC counts) in each layer and compares the values with what the UMC expected, producing a calibration file called rd_cal.******.  With this calibration file, the energy can be computed by converting the measured ADC counts with the factor given in rd_cal.****** to the amount in MeV unit.  Therefore, the energy measurement is proportional to the average muon energy deposit given by the UMC.
  6. Using the piscat monitor sample, we studied the RS energy deficit as a function of the RS range , the expected RS energy, the muon lifetime, the stopping layer, and the T.2 sector. There is no clear evidence of dependence except for the T.2 sector, which is due to the problem of the UTC measurement. From these studies, we almost exclude the possibility of the kp21 energy deficit from the RS energy calibration.