1. CP violation and mass hierarchy at medium baselines in the large 13 era
A large value of 13 is a major opportunity for precision neutrino physics: what changes at medium baselines? Can we access mass hierarchy and CPV much more easily?
Medium baselines at large 13
Superbeams: the case of CERN-to-LNGS and CERN-to-Phyasalmi
Liquid argon detectors and the exploitation of 2° maximum
Performances: CPV coverage, Mass hierachy sensitivity
Conclusions
S. Dusini, A. Longhin M. Mezzetto L. Patrizii, M. Sioli, G. Sirri, F. Terranova

2. The large 13 era
After 10 years of experimental searches we know the value of the 13 angle: it is surprisingly large and, by now, known with excellent precision
D. Dwyer [Daya Bay Neutrino 2012
T. Nakaya [T2K Neutrino 2012
13 = 8.9  0.4
Best fit before Neutrino 2012: Fogli et al., arXiv:

3. A few key questions:
A large 13 ease substantially the discovery of CP violation?
Addressed in this talk (*) for Superbeam with medium and large baselines
A large 13 ease substantially the discovery of mass hierarchy?
Addressed in this talk for Superbeam with medium and large baselines
In the framework of Superbeam, do we still need multi-MW drivers or we can adapt present facilities?
Addressed in this talk
Should we spend our money to increase the power of the driver or the quality/size of the detector?
Addressed in this talk
Can we build an “all-in-one” Superbeam for CPV and MH?
Addressed in this talk
(*) Special emphasis on European/CERN-based facilities

4. nm ne transitions at medium baselines
A nuisance for CP; an opportunity for MH.
In year 2002 [mostly inspired by tri-bimaximal mixing]
In year 2012 [data driven]
a0.03 comparable (or larger) than sin 213
a = 10-1 sin 213
Perturbative expansion appropriate
Perturbative expansion quite rough (*)
O1 and O2 of comparable size
O1 is the dominant contribution
(*) See e.g. Asano, Minakata JHEP 06(2011) 022

5. Beam simulation
Dedicated proton driver (50 GeV)
Primary target interaction:
Focusing system:
Decay tunnel:
Two horns: scan on horn
parameters and distance
90 m long and 2.2 m radius
(optimized values).
Tracing by GEANT4
Graphite 1m long
GEANT4 QGSP package
CERN-SPS (400 GeV)
Primary target interaction:
Focusing system:
Decay tunnel:
Pre-scan with BMPT parameterization (*) Graphite 1m long
GEANT4 QGSP package
Two horns: scan on horn
parameters and distance
1 km long and 1.2 m radius
(CNGS values).
Tracing by GEANT4
Optimization method: the beam paramenters are optimized using the 13 sensitivity as figure of merit. Such sensitivity is evaluated by Globes 3.1 assuming a LAr far detector of 100 kton.
(*) M. Bonesini et al., Eur. Phys. J. C20 (2001) 13

6. 2° oscillation peak Difficult to be exploited at medium baseline
2° oscillation peak Difficult to be exploited at medium baseline. Main strenght of long baseline facilities
Main Region of Interest (ROI)

7. Detector simulation
Updated detector description in the framework of GLOBES
NC background contamination (conservative): 0.1% of nmCC
Error on signal and background normalization: 5%
Energy resolution and efficiency for ne and bar-ne implemented through smearing matrices obtained from GENIE Monte Carlo generator :
Quasi elastic (QE)
80% efficiency
smearing of true-level e-momentum
2-body formula for Erec
yields s(En)/En~ 0.05/√En
DIS+RES
90 % efficiency
s(Ehad)/Ehad = 20%/√Ehad
Migration matrices calculated for ne and anti-ne separately.

8. Far detector location CERN to Gran Sasso (L=730 km)
CERN to Gran Sasso 7 km off -axis
Existing facilities 
Moderate size of the Halls (10 kton of LAr at most) 
Larger masses in a shallow lab 
Flux limitation due to the use of the SPS off-axis 
CERN to Phyasalmi (L=2290 km)
Minimal option: SPS based with 20 kton LAr
Ultimate option: 100 kton with a dedicated 50 GeV driver

9. CPV coverage (on-axis 50 GeV)
5% systematic error on flux normalization n + 5 anti-n years
Normal (known)
Inverted (known)
Normal (unknown)
Inverted (unknown)
Max SPS
Benchmarks (vertical lines):
10 kt Ä 0.77 MW Ä 10 y Þ 0 %
10 kt Ä 1.0 MW Ä 10 y Þ 0 %
10 kt Ä 2.4 MW Ä 10 y Þ %
Domain of sign ambiguity
Max LNGS

10. CPV coverage (off-axis 10 km 400 GeV)
5% systematic error on flux normalization n + 5 nbar years
Normal (known)
Inverted (known)
Normal (unknown)
Inverted (unknown)
Max SPS
Benchmarks (vertical lines)
20 kt Ä 0.77 MW Ä 10 y Þ %
30 kt Ä 0.77 MW Ä 10 y Þ %
100 kt Ä 0.77 MW Ä 10 y Þ %

11. Mass hierarchy coverage
5 % systematic error
on flux normalization
5 n + 5 nbar years
On-axis 50 GeV
10 kt Ä 0.77 MW Ä 10 y Þ %
10 kt Ä 1.0 MW Ä 10 y Þ %
10 kt Ä 2.4 MW Ä 10 y Þ 50 %
Normal
Inverted
The mass hierarchy coverage is better for the on-axis configuration since the on-axis neutrino spectrum includes most of the ROI.
In general, wide-band beam offers more sensitivity to MH and, hence on-axis configurations are better suited than off-axis (very narrow).
It was the opposite for the 13 sensitivity
Off-axis 10 km 400 GeV
20 kt Ä 0.77 MW Ä 10 y Þ 30 %
30 kt Ä 0.77 MW Ä 10 y Þ 35 %
100 kt Ä 0.77 MW Ä 10 y Þ 50 %
For a discussion see e.g. Coloma, Fernandez, Labarga, arXiv:

12. The “bimagic” baseline (e.g. CERN to Phyasalmi at 2290 km)
HOWEVER:
The bimagic baseline is very well suited for MH: MH coverage is nearly CP independent and large even at modest exposures.
Medium baselines outperform but need to know a priori the mass hierarchy
Both medium and long baseline can measure mass hierarchy. Long baselines slightly outperform due to 2nd maximum
20 kton , SPS-based
See A. Neutrino 2012

13. Systematics
ON-AXIS
As a general rule, medium baseline superbeams saturate their CPV overage at about 70%. The reason is due to systematics.
Normal hierachy, known
The CP phase d induce firstly a change in the normalization. Hence, the CP coverage at large exposure is dominated by the systematics on the overall normalization
In fact, 5 % :is widely used but the T2K super-beam nowadays is still above the 10% level
Control of systematics will be crucial for the design of future experiments; in fact, improving the systematic error pays much more than boosting mass/beam power for exposures larger than 2 MW yeff Mton

14. Conclusions (i.e. answers)
A large 13 ease substantially the discovery of CP violation?
It makes CPV accessible to Superbeams but CPV remains a major task due to the dominance of O1
A large 13 ease substantially the discovery of mass hierarchy?
Enormously! Thanks, again, to O1. Medium baselines can achieve full coverage for exposure larger than 1 MW y Mton. Longer baslines much before.
In the framework of Superbeam, do we still need multi-MW drivers or we can adapt present facilities?
We need it for CPV in any realistic configuration
Should we spend our money to increase the power of the driver or the quality/size of the detector?
For exposures larger than 2 MW yeff Mton we are systematic limited.

15. Well.. systematics are not unbeatable. Can you remember this? 
Can we build an “all-in-one” Superbeam for CPV and MH?
Yes if the exposure is larger than 1 MW yeff Mton . But to get coverage > 70% we need new ideas to cope with systematics
Well.. systematics are not unbeatable. Can you remember this? 
Daya Bay 2012
CHOOZ 1997