The ORCA Letter of Intent
Oscillation Research with Cosmics in the Abyss
ORCA
Antoine Kouchner University Paris 7 Diderot- AstroParticle and Cosmology
KM3NeT STAC meeting Catania 17/11/2015
The ORCA LoI2
Novelties since last STAC
Vertical spacing studies
Shower/Track ID + Atmospheric muon Rejection merged
Sensitivity studies Additional methods developed Systematics systematics Alternative hypothesis testing Oscillation parameters
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Benchmark Detector [§3.1]
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Simulations are performedfor this new configuration
Apply OM masking forvertical spacing studies
10 kHz/ PMT500 Hz 40K coincidence
115 lines, 20m spaced, 18 OM/line 6m spaced default
Instrumented volume ~3.8 Mt, 2070 OM
Scale factor 1/1.5/2/2.5
Trigger studies [§3.4] Shower trigger with min. 3L1 hits causally connected and
distance between L1s smaller than D
Muon trigger with assumed infinite track and min. 4L1 hits with a maximal roadWidth R ( _I_ to track)
ne + ne
(6m v-spacing)
Trigger studies [§3.4]
Latest Shower reconstruction [§4.2]
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Improvement in event selection plateau @ instrumented volume, earlier turn on
Latest Shower reconstruction [§4.2]
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Additional systematics [§4.2.6]• QE of PMTs, absorption length.
• Optical background [10 kHz conservative, 20 kHz unrealistic]
Muon channel reconstruction [§4.1]New hit selection V-spacing
Topology discrimination [5]• 3 topologies: tracks, cascades, atmospheric muons• Use of a Random Decision Forest with decision trees trained on MC.• Preselection :
• upward going reconstructed tracks or showers• Topological cuts
Few (tunable) % of atm. m contamination with equal prob of being ‘track’ or ‘shower’
Topology discrimination [5]
Sensitivity studies [6]13
Global Fit
Intermediate histograms
GenieNew modulefor sys studiesunder tests
Checkedagainst GLOBES
Detectorstudies
Sensitivity studies [6]14
Global Fit
Sensitivity studies [6]15
Global Fit1. Random set of oscillation parameter values generated (uncorrelated)2. 2 (tracks, cascades) x 2D (Erec, qrec) histograms = 1 PE3. Compute Likelihood given both hypotheses4. Fit mixing parameters assuming both NH and IH (max likelihood)5. Compute DlogL = log( L(NH)/L(IH) )
NHIH
(median significance to exclude the IH)
Sensitivity studies [6]16
Alternate hypothesis
True hypothesis : NH, q23,true
Alternative : : IH, q23,altValue found whenFitting the true hypothesiswith wrong hierachy
For each true hypothesis, find the most likely alternative hypothesis Extrapolate Gaussian Fits of LLR
Sensitivity studies [6]17
Alternate hypothesis
3 year significances
Sensitivity studies [6]CP phase effect
V-spacing studiesA simplified approach:
q12 , q13 , Dm2 fixed to central values all other 8 parameters fitted unconstrainedCP-phase fixed to 0.
Conclusion : ORCA V-SPACING will be ~9m
Determine the prob to refuteThe wrong hierarchy
(method checked to provideconsistent results wrt full LLR )
Oscillation parameters (1s contours)
NH IH
MinosNovaT2K
Same simplified approach.3 test points
ORCA 3 years projections
Summary ORCA LoI ready
Full MC production with conservative 10kHz optical background
Trigger simulations, track and shower reconstructions included
Particle ID and Muon background are merged.
Major systematics investigated
Optimal v-spacing found close to 9 m
Still to be investigated Exploit sensitivity to inelasticity
Explore sub-leading systematics
Thanks for your attention
Atmospheric muon rejection [§4.4]Features in the phase space
The ratio between the resulting effective mass after and before additional cuts
as a function of the neutrino zenith angle and energy. Values greater than one are possible as no requirement on the z position of the reconstructed
vertex is applied here, allowing neutrinos well below the detector instrumented volume.
Possible increase of statistic at high energy
Contamination Fraction of effective volume
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10m
30m
50m
40m
20m
70m
10m 20m
40m
70m50m
30m
Water vs Ice: OM-hit probabilityProbability to have at least one detected photon (KM3NeT OM)
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