Super-NOA
a long-baseline neutrino experiment
with two off-axis detectors
Based on
O. Mena, SPR and S. Pascoli
hep-ph/0504015
Sergio Palomares-Ruiz
June 22, 2005
What we know and what we do not
know about neutrinos

We don’t know if there are sterile neutrinos

We don’t know what the absolute mass of neutrinos is

We don’t know what is their nature: Majorana or Dirac

We don’t know what is the mass mechanism

We know that neutrinos do oscillate: have mass

We know that there are only 3 light active neutrinos
Sergio Palomares-Ruiz
June 22, 2005

We know
Solar sector
Reactor sector
Atmospheric sector
 m221 = (7.6 - 8.6) 10-5 eV2
sin2 13 < 0.041
|  m231 | = (1.5 – 3.4) 10-3 eV2
sin2 12 = (0.28 – 0.33)




We
We
We
We
don’t
don’t
don’t
don’t
know
know
know
know
sin2 223 > 0.92
the octant of 23
whether there is CP violation in the lepton sector
the type of mass hierarchy
whether 13 is different from 0
Sergio Palomares-Ruiz
June 22, 2005
O. Mena and S. J. Parke, Phys. Rev. D69:117301, 2004
Degeneracies
H. Minakata and H. Nunokawa, JHEP 0110:001,2001
(23 , /2 - 23)

( , 13)

sign( m231)
%

~ sin
~ cos
%
Sergio Palomares-Ruiz
June 22, 2005
Resolving degeneracies: (23 , /2 - 23)

Atmospheric neutrino experiments



Very long-baseline neutrino experiments


Sub-GeV events (solar term)
Multi-GeV events (matter effect)
Through the solar term contribution
Neutrino factories and  beams

e →  and e → 
Sergio Palomares-Ruiz
June 22, 2005
Resolving degeneracies:

Long-baseline neutrino experiments


( , 13)
Reduce degeneracy under special configurations
Reactor neutrino experiments

Only sensitive to 13

Atmospheric neutrino experiments

Neutrino factories and  beams
Sergio Palomares-Ruiz
June 22, 2005
Resolving degeneracies:
sign( m231)
Need of matter effects → 13  0

Atmospheric neutrino experiments


Long-baseline neutrino experiments


Multi-GeV events
Off-axis experiments
Neutrino Factories and  beams
Sergio Palomares-Ruiz
June 22, 2005
Off-axis concept
Neutrinos produced in two body decays:  →  + 
0.43E
E 
1   2 2
 2
Flux  
2 2
1  
D. Beavis et al., BNL Proposal E-889
June 22, 2005
2
 1

2
 4L
Sergio Palomares-Ruiz
Experimental set-up
NOA






Medium energy beam
50 (30) kton calorimeter
L = 810 km
Off-axis distance = 10 km
→ E = 2.3 GeV
3.7 (6.5) x 1020 pot/yr
Proton Driver =
18.5 (25) x 1020 pot/yr
Super-NOA




NOA + another off-axis detector
with the same L/E (L = 200 km)
We will consider 50 kton Liquid
Argon detectors (high efficiency)
Only neutrinos
5 years
2nd detector = Super-NoA
D. S. Ayres et al. [NOA Collaboration], hep-ph/0503053
June 22, 2005
NoA
Sergio Palomares-Ruiz
Probabilities

Up to second order in 13, 12/13, 12/A and 12L
A. Cervera et al., Nucl. Phys. B579:17, 2000
P( → e) = x2 f2 + 2 x y f g cos( - ) + y2 g2
x ≡ sin 23 sin 213
y ≡ (m221 / m231) cos 23 sin 212
f ≡  sin(-AL/2)/( - AL/2)
g ≡ sin(AL/(2 ))/(AL/(2 ))
 ≡ m231 L / (4 E)
June 22, 2005
Sergio Palomares-Ruiz
Asymmetry
D
P ( L N )  P ( LF )
P ( L N )  P ( LF )
AN L N  AF LF
D1 
2
O. Mena, SPR and S. Pascoli, hep-ph/0504015
June 22, 2005
1 
1
 

  tan  
Sergio Palomares-Ruiz
2 2
2 2
y 
1 2
1 

 1 AN LN  AF LF  1
D2  D1 1 
cos(    )  sin 213  



x sin 
2
4

 2
  tan  
O. Mena, SPR and S. Pascoli, hep-ph/0504015
June 22, 2005
Sergio Palomares-Ruiz
Bi-event plot for NOA
P = A cos cos + B sin sin + C
It collapses to a line if:
P = A cos cos + B sin sin + C
(AB - AB) cos sin  0
B=A
B = -A
cos sin  0
NOA
0.9 <  < 1.3
O. Mena, SPR and S. Pascoli, hep-ph/0504015
June 22, 2005
Sergio Palomares-Ruiz
Bi-event plots for Super-NOA
PF = AF cos cos + BF sin sin + CF
PN = AN cos cos + BN sin sin + CN
It collapses to a line if:
(AFBN – ANBF) cos sin  0
BF = AF
BN = AN
It is always a line
O. Mena, SPR and S. Pascoli, hep-ph/0504015
June 22, 2005
Sergio Palomares-Ruiz
Measurable integrated asymmetry
A 
N / N o N  N / N o F
N / N o N  N / N o F
2 analysis
95% C.L.
PD
99%
95%
90%
O. Mena, SPR and S. Pascoli, hep-ph/0504015
June 22, 2005
Sergio Palomares-Ruiz
Comparison with NOA and T2K
D. S. Ayres et al. [NOA Collaboration], hep-ph/0503053
6 yrs  + 6 yrs 
with NOA
+
3 yrs  + 3 yrs 
with 2nd detector
at second maximum
pot/yr
= 6.5 x 1020
pot/yr (PD) = 25 x 1020
12 km off-axis
3 yrs  + 3 yrs 
With Super-NoA
only 5 yrs to get
there
Sergio Palomares-Ruiz
June 22, 2005
Conclusions




Resolving degeneracies is a crucial task
Super-NOA: 2 off-axis (LAr) detectors with same L/E
using the NuMI beam → determination of sign( m231)
free of degeneracies
Only need of 5 years of neutrino run to resolve the type of
hierarchy down to sin2 213 = 0.02 with Proton Driver (for
all values of )
Better capabilities than NOA + T2K at HK for determining
the type of mass hierarchy
Sergio Palomares-Ruiz
June 22, 2005