Muon absolute flux measurement in anti-neutrino mode A.Ariga 1, C. Pistillo 1, S. Aoki 2 1 University of Bern, 2 Kobe University

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 MC error = statistical only Momentum measurement (250kA, 2010) MC 11b (FLUKA with NA61 tuning) with systematic uncertainty of 14% Flux measurement (250kA, 2010)

Emulsion modules Same module structures as 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)

2 nd emulsion exposure (run31, 18 th Mar 2010) Similar setup will be used Emulsion modules Vertical support (may be not needed) Horizontal aluminum support (Currently used as the support of diamond detector)

Exposure scheme 3 exposures – -250kA anti-neutrino mode – 0kA (cross-check with old result) – 250kA neutrino mode (cross-check) Low intensity protons on target – POT ~ 2-4x10 11 to maintain muon flux ~10 4 /cm 2 in emulsion (reconstruction comfortable up to 10 5 ) – last exposures 250 kA : 2x10 11 POT (~2x10 4 /cm 2 ) 0kA : 4x10 11 POT (~1x10 4 /cm 2 ) Exposure cycle: 1 exposure cycle take ~ 1.5 hours Exposures can be accommodated during MR study 15 min 5min 10min 1 hour Installation Shot Air exchange Safe ty

Film handling, scanning Preparation in Nagoya ~ 2 weeks – BG reduction treatment: 7 days Refreshing 28 degree, 98% RH x 7 days – Film shaping, module assembling: a few days Development in Kobe ~ a few days Scanning in Bern ~ 2-3 weeks – a few days to tune a scanning microscope – weeks to scan 2 cm 2 x 250 films by one microscope

Possible timing Need stable beam condition – difficult to repeat measurement frequently Before summer shutdown? – may be possible but unpredictable Desired in Nov – after a commissioning in June – better availability of people

Backup

Measure position, angle and momentum of muons. Beam dump Emulsion tracker at muon pit 9   Transverse momentum by scattering ~250MeV/c Emulsion tracker Measurement - Position - 3D angle (  =~3mrad) - Momentum ~150X 0 energy loss 5GeV P T =30MeV/c Muon Pit MUMON Decay volume Reconstructed data MUMON Beam Momentum module Flux modules MUMON

Flux measurement 11b flux thanks to Kubo Good agreement with FLUKA with NA61 tuning for 250kA 0kA 250kA MC error = stat only MC 11b (FLUKA with NA61 tuning) with systematic uncertainty of 14% Kubo

Probe for hadron production model Principle: by 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)

Data taking & reconstruction 1.5 x 1.5 cm 2 is scanned for all 50 plates(25 plates x 2 horn current) tracks start in 1cm 2 at center, start within 3 plates, tan  =6 is selected for momentum measurement 12 tracks reconstructed in the volume (1/10 tracks are shown)

Reconstructed momentum distribution Linear Log Clearly FLUKA tuned is favored with respect to GCALOR. The shape more or less agree. but not very good at low energy region. MC error = statistical only