the orca letter of intent oscillation research with cosmics in the abyss orca antoine kouchner...

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

3

Benchmark Detector [§3.1]

4

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]

7

Improvement in event selection plateau @ 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. 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

25

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)

25