1. T2K muon measurement 2014 Momentum module A.Ariga, C. Pistillo University of Bern S. Aoki Kobe University 1

2. Probe for hadron production model Method: multiple coulomb scattering Momentum measurement Low energy track High energy track Track reconstruction efficiency (MC) Momentum resolution (MC) 25 emulsion film + 24 mm lead (1mm thick) 2

3. Emulsion modules Same module structures as the last experience Emulsion film = OPERA film – Available thanks to Nagoya university – the films were produced in 2004, the film quality (BG accumulation) is expected to be worse than 2009,2010 runs; a tuning of tracking algorithm may be required ~300 films (6cmx5cm) – corresponding to ~75 OPERA films Flux module 8 films Momentum module 25 x (films + 1mm-lead) 3

4. Momentum module Measure momentum with multiple Coulomb scattering. – In ECC, 25 films + 24 lead ECC brick – 6 cm x 5 cm Exposure with 250kA, -250kA (new!), 0kA 4

5. Scanning area Large data volume of 2.5cm x 2.5cm x 25 films is scanned for each exposure Data are well aligned with muon tracks. center +-10mm was used for reconstruction. ROI scanned areas 5

6. Reconstructed tracks in volume Reconstruction successful About 20000/cm2, comfortable for reconstruction 1/10 of tracks are drawn micron 6

7. Tracking efficiencies Uniform quality among modules. High efficiency in roi Although slightly decreased w.r.t. 2010 run. Blue fitted line is implemented in MC BT BT eff Track detection efficiency Plate by Plate Angular dependence Comparison with 2010 run 7

8. Selections Track selection – 1 st segment position with +- 5mm (1cm 2 ) from center – Track starts with in the first 3 plates – 1 st segment angle < 0.3 – Number of segments >= 6 8

9. Reconstructed momentum 3 exposures were processed MC, 11b FLUKA with tuning (no -250kA, yet) – efficiency in MC is tuned for new exposure Rather good agreement with MC. Slightly less at low momentum. 9

10. Reconstructed momentum Same, in log scale 10

11. Data/MC ratio Less at low energy, More at high energy 11

12. Less low energy… Consistent with angular distribution MC has wider distribution in angular distribution  MC has more low energy components. This is confirmed by the momentum measurement. Plot from 2010 flux module At cener, 250kA 12

13. Measurement of components collected by horn Evaluate difference from 0kA absolute scale Area-normalized. Very similar,,, slightly more low-energy component in -250kA 250kA0kA Sum 250kA : 21084 -250kA: 10655 13

14. Difference between 2010 and 2014 Data volume is adjusted to 2010 data (+-7mm) Two measurements gives a good agreement overall, taking the difference of efficiency into account. A small difference at low energy bin (0.5-1 GeV/c). Data MC with different efficiency implementation 14

15. Difference between 2010 and 2014 Back to the raw data, the data set was not complete for 2010 data, especially for 250kA. – BT cut was applied before precision alignment.  distortion of P distribution. For 2014 analysis, BT cut is done after alignment. Data missing due to miss alignment 2010 250kA z-x 2014 250kA z-x black: all data in +-7mm blue: tracks used for momentum plot (+-5mm at upstream) 15

16. Summary Momentum distribution for 3 horn current conditions are measured – neutrino, antineutrino modes and horn off Data looks reasonable – For 250kA, less low energy tracks than the expected. – Neutrino, anti-neutrino modes gives similar momentum distributions. – Reproducibility is checked. MC for antineutrino mode to be compared 16

17. Muon measurement by emulsions Successful result in neutrino mode (2010) Diagnosis of hadron production model in anti-neutrino mode by checking muon flux and momentum distributions Resource for the MC analysis available from Kyoto (to be confirmed) MC error = statistical only Momentum measurement (250kA, 2010) MC 11b (FLUKA with NA61 tuning) with systematic uncertainty of 14% Flux measurement (250kA, 2010) 17

18. Measured profile (preliminary) Scanning of all flux modules has been finished. Profile with efficiency correction and BG subtraction – Cosmic-ray BG is measured to be 50 tracks/cm 2 (0.3% of muons tracks) Good reproducibility (1.8%) w.r.t 2009, 2010 measurement campaigns – Note : many changes in 4 years (Horns, power supply), POT measurement uncertainty (2%) agreement at 2 % level for 250kA 1% for 0kA 18

19. BT position in 250kA in 2014 Volume +-1cm 19

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