getting the most in neutrino oscillation experiments hisakazu minakata tokyo metropolitan university
TRANSCRIPT
Getting the most in neutrino oscillation experiments
Hisakazu Minakata
Tokyo Metropolitan University
August 24-30, 2006 Nufact06@UC Irvine
In the last several years we have experienced the most
exciting era in physics
August 24-30, 2006 Nufact06@UC Irvine
oscillation has been seen!
KamLANDKamLAND K2KK2K
SKSK
MINOSMINOS
August 24-30, 2006 Nufact06@UC Irvine
Exploring the unknowns; 1-3 sector and mass hierarchy
<= solar + reactor
<= solar + reactor
Atm + accel =>
Atm + accel =>
=Ui i=Ui i
SK atmSK atm
solar+KamLANDsolar+KamLAND
August 24-30, 2006 Nufact06@UC Irvine
Foreseeing the next 10-
20 years
August 24-30, 2006 Nufact06@UC Irvine
Things changes at sin2213~0.01
• Conventional super beam works
• Known beam technology
• Background highly nontrivial
e beam contamination not negligible but tolerable
• beta beam / neutrino factory required
• Requires long-term R&D efforts
• Low background
• pure e beam () / well understood combination of e and beam (nufact)
Large 13 > 3oLarge 13 > 3o small 13 < 3osmall 13 < 3o
August 24-30, 2006 Nufact06@UC Irvine
Superbeam; Two alternative strategies
• Pinpoint to the 1st oscillation maximum
• Relatively clean background at low energies
• elaborated 0 rejection algorism developed
• Covers multiple oscillation maxima
• The issue of background becomes severer at high energies
• ‘‘Dien Bien Phu’’ of the BNL strategy
Off axis narrow-band beamOff axis narrow-band beam On axis wide-band beamOn axis wide-band beam
multi-MW proton beam requiredmulti-MW proton beam required
August 24-30, 2006 Nufact06@UC Irvine
Beta beam vs. Neutrino factory
• pure e beam
• charged pion background seems tolerable
• e- separation required but no charge ID required
• multi-MW proton beam NOT required
• well understood combination of e and beam with precisely (~10-5) known muon energy
• small background (how small?)
• muon charge ID required
• multi-MW proton beam required
beta beambeta beam neutrino factoryneutrino factory
August 24-30, 2006 Nufact06@UC Irvine
Getting the most in conventional superbeam
• To define the role of beta beam and/or neutrino factory precisely, it may be of help if superbeam reach is clearly marked
• Let me focus in on conventionalsuperbeam
• I will try to explain some basic facts and use two concrete examples;
• T2KK (Tokai-to-Kamioka-Korea) \simeq extended NOVA
• Fermilab/BNL realization of BNL strategy
August 24-30, 2006 Nufact06@UC Irvine
T2KK; Tokai-to-Kamioka-Korea identical two-detector complex
2nd Korean detector WS was held @SNU, Seoul, in July 13-14
Ishitsuka et al. 05, Kajita-HM-Nakayama-Nunokawa, to appear
Ishitsuka et al. 05, Kajita-HM-Nakayama-Nunokawa, to appear
=>Okumura-san’s talk=>Okumura-san’s talk
August 24-30, 2006 Nufact06@UC Irvine
Degeneracy; a notorious obstacle
August 24-30, 2006 Nufact06@UC Irvine
Cause of the degeneracy; easy to understand
• You can draw two ellipses from a point in P-Pbar space
• Intrinsic degeneracy
• Doubled by the unknown sign of m2
• 4-fold degeneracy
August 24-30, 2006 Nufact06@UC Irvine
23 octant degeneracy
Pe= sin2213 x s223
Pe= sin2213 x s223
Solar m2 on
Matter effect on
Solar m2 on
Matter effect on
OY Nufact03OY Nufact03
Altogether, 2 x 2 x 2 = 8-fold degeneracy
Altogether, 2 x 2 x 2 = 8-fold degeneracy
August 24-30, 2006 Nufact06@UC Irvine
What’s good in T2KK?
(what about NOVA?)
August 24-30, 2006 Nufact06@UC Irvine
T2KK vs. NOVA with 2nd detector (LOI)
1st = 0.8
2nd ~1.8
• (aL/)1st = 0.17
• (aL/)2nd = 0.07
1st =
2nd ~3
• (aL/)1st = 0.05
• (aL/)2nd = 0.05
NOVA 2nd phaseNOVA 2nd phase T2KKT2KK
In fact, they are similar; both uses off-axis narrow-band beam with similar values of L/E
= m2 L / 2E
In fact, they are similar; both uses off-axis narrow-band beam with similar values of L/E
= m2 L / 2E
August 24-30, 2006 Nufact06@UC Irvine
T2KK; the basic ideas
• Leptonic CP violation and mass hierarchy resolution highly nontrivial for conventional superbeam
• Try to do a reliable conservative estimate on its maximal (assuming 4MW + total 1 Mton) performance
• Restrict to: known background rejection technology by SK + conservative estimate of the systematic errors (5%) + identical 2 detector setting
• T2KK (Tokai-to-Kamioka-Korea)
August 24-30, 2006 Nufact06@UC Irvine
T2KK; the performance
• Analysis method (next slide); 4yr + 4yr anti-, fiducial0.27 Mton each
• Can resolve intrinsic and sign-m2 degeneracies to determine mass hierarchy and uncover CP violation
• see the next-next slides • Can resolve 23 octant degeneracy• see the next-next-next slides
T2KK in situ solves 8-fold degeneracy !T2KK in situ solves 8-fold degeneracy !
August 24-30, 2006 Nufact06@UC Irvine
2 definitione-like bins -like bins
systematicerror term
detector x beamcombination
f ij : fractional change in the predicted event rate in the i th bin
due to a variation of the parameter j
j : systematic error parameters, which are varied to minimize 2
for each chioce of the oscillation parameters
“ Pull Approach ” G.L.Fogli et al. PRD66 (2002) 053010
Nakayama-san’s slide @2nd Korean detector WSNakayama-san’s slide @2nd Korean detector WS
August 24-30, 2006 Nufact06@UC Irvine
August 24-30, 2006 Nufact06@UC Irvine
T2KK sensitivity; mass hierarchy
thick: 3, thin: 2thick: 3, thin: 2 Insensitive to 23Insensitive to 23
August 24-30, 2006 Nufact06@UC Irvine
T2KK sensitivity; CP
thick: 3, thin: 2thick: 3, thin: 2 Insensitive to 23Insensitive to 23
August 24-30, 2006 Nufact06@UC Irvine
Sensitivity to 23 octant (cont’d)si
n2
2 1
3
sin2 23 sin2 23
can determine 23 octantfor any by
> 32~3
If sin2 23<0.42 or >0.58(sin2 223= 0.974), 23 octantcan be determined by >2even at very small sin2 213 .
August 24-30, 2006 Nufact06@UC Irvine
Sensitivity comparison with T2K+Reactor
T2K-II + phase II reactorT2KK=0 assumed
sin
2 2
13
sin2 23
sin
2 2
13
> 32~3
T2KK 2(rough)
T2KK has better sensitivityat sin2 213 < 0.06~0.07 .
hep-ph/0601258
Hiraide et al 06Hiraide et al 06
August 24-30, 2006 Nufact06@UC Irvine
Why T2KK performance so good ?
August 24-30, 2006 Nufact06@UC Irvine
Spectral information solves intrinsic degeneracy
from 1000 page Ishitsuka file
from 1000 page Ishitsuka file
SK momentum resolution ~30 MeV at 1 GeVSK momentum resolution ~30 MeV at 1 GeV
T2KT2K T2KKT2KK
2 detector method powerful!2 detector method powerful!
August 24-30, 2006 Nufact06@UC Irvine
Sensitive to because energy dependence is far more dynamic in 2nd oscill
ation maximum
August 24-30, 2006 Nufact06@UC Irvine
It is not quite only the matter effect
• With the same input parameter and Korean detector of 0.54 Mt the sign-m2 degeneracy is NOT completely resolved
2 identical detector method powerful !
2 identical detector method powerful !
T2KKT2KK Korea onlyKorea only
August 24-30, 2006 Nufact06@UC Irvine
Solar and atm. terms differ in energy dependences
All different in energy dependences !
All different in energy dependences !
August 24-30, 2006 Nufact06@UC Irvine
In a nutshell, 8 fold degeneracy can be resolved by T2KK because
..• intrinsic degeneracy is resolved by spectru
m information
• sign-m2 degeneracy is solved with matter effect + 2 identical detector comparison
23 octant degeneracy is solved by identifying the solar oscillation effect in T2KK
August 24-30, 2006 Nufact06@UC Irvine
Can we resolve
degeneracy one by one?
August 24-30, 2006 Nufact06@UC Irvine
Decoupling between degeneracies
• Suppose that you succeeded to solve the particular degeneracy, by forgetting about the remaining ones
• It does NOT necessarily mean that the problem is solved
• You have to verify that your treatment of degeneracy A is valid irrespective of the presence of degeneracy B
• One solution: decoupling between the degeneracies
August 24-30, 2006 Nufact06@UC Irvine
23 and sign-m2 degeneracy decouple
• For example, one can show, to first order in matter effect, the followings:
P(octant) = P(1st octant) - P(2nd) is invariant under the interchange of two sign-m2 degenerate pair
P(hierarchy) = P(m2 +) - P(m2 -) is invariant under the interchange of two 23 octant degenerate pair
• in T2K or T2KK setting, the intrinsic degeneracy is resolved by spectrum analysis decouple from the game
August 24-30, 2006 Nufact06@UC Irvine
More aggressiv
e approach
es?
August 24-30, 2006 Nufact06@UC Irvine
BNL strategy; using wide-band beam to explore multiple oscillation maxima
<=background ?
<=background ?
1 1
August 24-30, 2006 Nufact06@UC Irvine
Recent analysis incl. Fermilab version• 1 MW beam from F
ermilab/BNL 5 years + anti- 1
0 years• Yanagisawa’s analy
sis assumed• Aggressive assumpt
ions for systematic errors;
• signal norm. 1% background 10% + no shape error
CP fraction=1CP fraction=1
000.50.5
Barger et al. 06Barger et al. 06
August 24-30, 2006 Nufact06@UC Irvine
BNL method vs. T2KK
thin: 3thin: 3 T2KKT2KK
BNL 1300 km
BNL 1300 km
August 24-30, 2006 Nufact06@UC Irvine
Problem of backgroundFanny Dufour @2nd Korean detector WS
Fanny Dufour @2nd Korean detector WS
=> energy-dependent systematic errors=> energy-dependent systematic errors
August 24-30, 2006 Nufact06@UC Irvine
Conclusion for conventional superbeam
• T2KK (2 detector) & BNL method (multiple OM) are reaching ‘‘optimal sensitivities’’ achievable by conventional superbeam
• These two method can be combined; e.g., Korean detector @ 1 degree OA
• Can resolve 8 fold parameter degeneracy in situ with consistency maintained by “decoupling”
Caution; uncorrelated systematic errors (between 2 detectors) enter
Caution; uncorrelated systematic errors (between 2 detectors) enter
August 24-30, 2006 Nufact06@UC Irvine
Beta beam or neutrino f
actory?
August 24-30, 2006 Nufact06@UC Irvine
BENE Report 06BENE Report 06
August 24-30, 2006 Nufact06@UC Irvine
Beta vs. T2KK
Campagne et al. 06Campagne et al. 06
August 24-30, 2006 Nufact06@UC Irvine
factory as ultimate degeneracy solver
• By combining at 3 detectors at 130, 730, and 2810 km, it was claimed that neutrino factory can resolve all the 8-fold degeneracy if 13 > 1° (Donini, NuFACT03)
Typical ‘‘everything at once’’ method Typical ‘‘everything at once’’ method
Powerful, but expensive! ~1000 Million Euro/degeneracyPowerful, but expensive! ~1000 Million Euro/degeneracy
August 24-30, 2006 Nufact06@UC Irvine
Conclusion • To clearly define the role of nufact/ the better idea
for superbeam reach required• I tried to give it by using two concrete settings; T2K
K (2 detector) & BNL method (multiple OM) • their performance is quite good (compared to
what was thought in 10 years ago!) and the sensitivities to CP & mass hierarchy may go down to sin2213 ~ 0.01
• A strategy of solving 8-fold parameter degeneracy developed by one-by-one manner with ‘‘decoupling’’
August 24-30, 2006 Nufact06@UC Irvine
Conclusion (continued)
• However, a caution needed: BNL analysis needs better understanding of energy dependent background (at low energies)
• Sensitivities of T2KK could be enhanced by near on-axis Korean detector
• If successful, they are competitive to beam
August 24-30, 2006 Nufact06@UC Irvine
Supplementary slides
August 24-30, 2006 Nufact06@UC Irvine
Sensitivity study• Assumption
– 2.5 o off-axis T2K 4MW beam– 4 years beam + 4 years beam– Kamioka : 0.27 Mton fid., L = 295 km, = 2.3 g/cm3
Korea : 0.27 Mton fid., L = 1050 km, = 2.8 g/cm3
m212 = 8.0 x 10-5 (eV2)
|m223| = 2.5 x 10-3 (eV2)
sin2 12 = 0.31
• Oscillation parameter space (unknown parameters)– sin2 23 : 0.35 ~ 0.65 [ 31 bins ]– sin2 213 : 0.0015 ~ 0.15 [ 98 bins on log scale ] CP : 0 ~ 2 [ 100 bins ]– mass hierarchy : normal or inverted [2 bins ]
4 dimensional analysisusing no external information on these parameters
Nakayama-san’s slide @2nd Korean detector WS
Nakayama-san’s slide @2nd Korean detector WS
August 24-30, 2006 Nufact06@UC Irvine
Sensitivity study (cont’d)• Binning
– e-like : 5 energy bins (0.4-0.5, 0.5-0.6, 0.6-0.7, 0.7-0.8, 0.8-1.2 GeV) -like : 20 energy bins (0.2-1.2 GeV)– (Kamioka, Korea) x ( beam, beam)
(5+20) x 4 = 100 bins in total
• Systematic errors– e-like bins
BG normalization 5 % BG spectrum shape 5 % (i-3)/2 (i=1…5 ene bin) signal normalization 5 %
-like bins BG normalization 20 % spectrum shape 5 % E(GeV)-0.8 / 0.8 signal normalization 5 %
– both bins(7) spectrum distortion in Korea shape diff. btw Kam. and Korea 1
August 24-30, 2006 Nufact06@UC Irvine
Effect of the solar termm2
12 = 8.0 x 10-5 (eV2)m2
23 = 2.5 x 10-3 (eV2)sin2 12 = 0.31sin2223 = 0.96 = 3/4 normal mass hierarchy
Kamioka 0.27Mton
( 4MW, 4yr + 4yr )
Korea 0.27Mton
( 4MW, 4yr + 4yr )
sin2 23 = 0.4, sin2 213 = 0.01
sin2 23 = 0.6, sin2 213 = 0.0067
Solar term is negligibly smalldue to shorter baseline in Kamioka.
Num
ber
of
signal events
(BG
not
incl
uded
)
Solar term can be seenin low E region in Korea.