Super-NO?A

1
Super-NO?A
a long-baseline neutrino experimentwith two
off-axis detectors

• Based on
• O. Mena, SPR and S. Pascoli
• hep-ph/0504015

2
What we know and what we do not know about
neutrinos

• We dont know if there are sterile neutrinos
• We dont know what the absolute mass of neutrinos
  is
• We dont know what is their nature Majorana or
  Dirac
• We dont know what is the mass mechanism
• We know that neutrinos do oscillate have mass
• We know that there are only 3 light active
  neutrinos

3

• We know

• Solar sector
• ? m221 (7.6 - 8.6) 10-5 eV2
• sin2 ?12 (0.28 0.33)

Reactor sector sin2 ?13 lt 0.041
Atmospheric sector ? m231 (1.5 3.4) 10-3
eV2 sin2 2?23 gt 0.92

• We dont know the octant of ?23
• We dont know whether there is CP violation in
  the lepton sector
• We dont know the type of mass hierarchy
• We dont know whether ?13 is different from 0

O. Mena and S. J. Parke, Phys. Rev. D69117301,
2004
4
Degeneracies
H. Minakata and H. Nunokawa, JHEP 0110001,2001

• (?23 , ?/2 - ?23)
• (? , ?13)
• sign(? m231)

sin?
cos?

5
Resolving degeneracies (?23 , ?/2 - ?23)

• Atmospheric neutrino experiments
• Sub-GeV events (solar term)
• Multi-GeV events (matter effect)
• Very long-baseline neutrino experiments
• Through the solar term contribution
• Neutrino factories and ? beams
• ?e ? ?? and ?e ? ??

6
Resolving degeneracies (? , ?13)

• Long-baseline neutrino experiments
• Reduce degeneracy under special configurations
• Reactor neutrino experiments
• Only sensitive to ?13
• Atmospheric neutrino experiments
• Neutrino factories and ? beams

7
Resolving degeneracies sign(? m231)
Need of matter effects ? ?13 ? 0

• Atmospheric neutrino experiments
• Multi-GeV events
• Long-baseline neutrino experiments
• Off-axis experiments
• Neutrino Factories and ? beams

8
Off-axis concept
Neutrinos produced in two body decays ? ? ? ??
D. Beavis et al., BNL Proposal E-889
9
Experimental set-up

• 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

• 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

2nd detector Super-No?A
No?A
D. S. Ayres et al. NO?A Collaboration,
hep-ph/0503053
10
Probabilities

• Up to second order in ?13, ?12/?13, ?12/A and ?12L

A. Cervera et al., Nucl. Phys. B57917, 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?)
11
Asymmetry
O. Mena, SPR and S. Pascoli, hep-ph/0504015
12
O. Mena, SPR and S. Pascoli, hep-ph/0504015
13
Bi-event plot for NO?A
P A cos? cos? B sin? sin? C P A cos?
cos? B sin? sin? C
It collapses to a line if (AB - AB) cos? sin?
0
B A B -A
cos? sin? 0
NO?A 0.9 lt ? lt 1.3
O. Mena, SPR and S. Pascoli, hep-ph/0504015
14
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
15
Measurable integrated asymmetry
?2 analysis
95 C.L.
PD
99
95
90
O. Mena, SPR and S. Pascoli, hep-ph/0504015
16
Comparison with NO?A and T2K
pot/yr 6.5 x 1020 pot/yr (PD) 25 x
1020 12 km off-axis 3 yrs ? 3 yrs ?
D. S. Ayres et al. NO?A Collaboration,
hep-ph/0503053
With Super-No?A only 5 yrs to get there
6 yrs ? 6 yrs ? with NO?A 3 yrs ? 3 yrs
? with 2nd detector at second maximum
17
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