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 LoI 2

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 3

Benchmark Detector [§3.1] 4 Simulations are performed for this new configuration Apply OM masking for vertical spacing studies 10 kHz/ PMT 500 Hz 40 K 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) e + e (6m v-spacing)

Trigger studies [§3.4]

Latest Shower reconstruction [§4.2] 7 Improvement in event selection  instrumented volume, earlier turn on

Latest Shower reconstruction [§4.2] 8

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.  contamination with equal prob of being ‘track’ or ‘shower’

Topology discrimination [5]

Sensitivity studies [6] 13 Global Fit Intermediate histograms Genie New module for sys studies under tests Checked against GLOBES Detector studies

Sensitivity studies [6] 14 Global Fit

Sensitivity studies [6] 15 Global Fit 1. Random set of oscillation parameter values generated (uncorrelated) 2. 2 (tracks, cascades) x 2D (E rec,  rec ) histograms = 1 PE 3. Compute Likelihood given both hypotheses 4. Fit mixing parameters assuming both NH and IH (max likelihood) 5. Compute  logL = log( L(NH)/L(IH) ) NH IH (median significance to exclude the IH)

Sensitivity studies [6] 16 Alternate hypothesis True hypothesis : NH,  23,true Alternative : : IH,  23,alt Value found when Fitting the true hypothesis with 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 studies A simplified approach:  12,  13,  m 2 fixed to central values all other 8 parameters fitted unconstrained CP-phase fixed to 0. Conclusion : ORCA V-SPACING will be ~9m Determine the prob to refute The wrong hierarchy (method checked to provide consistent results wrt full LLR )

Oscillation parameters (1  contours) NH IH Minos Nova T2K 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 ContaminationFraction of effective volume

25 10m 30m 50m 40m 20m 70m 10m 20m 40m 70m50m 30m Water vs Ice: OM-hit probability Probability to have at least one detected photon (KM3NeT OM) 25