# Residual Symmetries Applied to Neutrino Oscillations at NOνA and T2K

Authors: Andrew D. Hanlon; Wayne W. Repko; Duane A. Dicus
Journal: Advances in High Energy Physics
 (2014)

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## Abstract

The results previously obtained from the model-independent application of a generalized hidden horizontalZ2 symmetry to the neutrino mass matrix are updated using the latest global fits for the neutrino oscillation parameters. The resulting prediction for the Dirac CP phase δD is in agreement with recent results from T2K. The distribution for the Jarlskog invariant Jν has become sharper and appears to be approaching a particular region. The approximate effects of matter on long-baseline neutrino experiments are explored, and it is shown how the weak interactions between the neutrinos and the particles that make up the Earth can help to determine the mass hierarchy. A similar strategy is employed to show how NOνA and T2K could determine the octant of θa(≡θ23). Finally, the exact effects of matter are obtained numerically in order to make comparisons with the
form of the approximate solutions. From this analysis there emerge some interesting features of the effective mass eigenvalues.


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## Body

## 1. Introduction

Although there has been significant progress in neutrino physics from oscillation experiments, there remains much work to be done. The reactor angleθr(≡θ13) has now been measured to greater accuracy than ever before, and the solar angle θs(≡θ12) has been known for some time now. But, the octant of the atmospheric angle (θa>π/2 or θa<π/2) or whether this angle is maximal (θa=π/2) has yet to be answered. Determination of the Dirac CP phase has been improved. Recent results from T2K exclude at 90% C.L. δD∈[34.2∘,144∘] for normal hierarchy (NH) and δD∈[-180∘,-174.6∘]∪[-7.2∘,180∘] for inverted hierarchy (IH) [1]. Finally, the absolute value of the mass squared differences has been carefully measured, but the mass hierarchy is still undetermined (i.e., m3≫m2>m1 or m2>m1≫m3). Each of these questions will be discussed in this work.From the improvements in recent global analyses [2–4] it is possible to make more accurate predictions for the distributions of some of the aforementioned parameters of interest. Specifically, each of the residual symmetries, Z2s and Z¯2s, can be used to derive a model-independent equation for δD (one for each symmetry) [5, 6]. Then using the newly available global fits of the neutrino oscillation parameters in [2], likelihood distributions for δD, the Jarlskog invariant [7], and θa are obtained.Using the PMNS mixing matrix, an expression for the probability of a neutrino originally of flavorα to be detected as a neutrino of flavor β, P(να→νβ) is presented (which is a standard result found in many review papers on neutrino physics [8]). Then, using the approximation from [9] it is shown how the earth’s matter affects the neutrino beam in long-baseline experiments. This is done by replacing the oscillation parameters with effective values that depend on the energy of the neutrinos, the baseline length, and the density of the matter.In this paper, a focus is made on the NOνA and T2K experiments. Both of these experiments measure the appearance of νe’s (ν¯e’s) from a νμ(ν¯μ) beam. The probability for this appearance is plotted as a function of energy using the best fits for the oscillation parameters in [2]. The effects of matter are taken into account using the average matter density along the baseline for the two experiments. This is justified by the fact that there does not appear to be a significant effect due to the variation of the matter density [10]. A comparison is made for this probability with and without CP-violation in an attempt to observe the sensitivity of NOνA and T2K to measurements of δD. We have also plotted P(νμ→νe) versus P(ν¯μ→ν¯e) which shows that it may be possible for these experiments to determine the neutrino mass hierarchy for some values of the CP phase as discussed in [11, 12].The update of the analysis of [13] given in [2] gives closer agreement on θa with the other two major global analyses [3, 4]. This shows that θa is closer to being maximal than originally believed and only excludes the possibility of it being maximal by about 1σ for inverted hierarchy. But, it is clear that the analyses do not agree upon which octant is favored. Fortunately, the plots of P(νμ→νe) versus P(ν¯μ→ν¯e) may also serve to determine the octant of θa [11, 12].This work is concluded with a digression into the effective mixing angles and masses in matter. The solar resonance, first described by the MSW effect [14–16], and the atmospheric resonance are readily observed.


## 2. Distribution ofδD, Jν, and θa

The equations forδD, in terms of the neutrino mixing angles, based on residual symmetries are given by [5, 6] (1a)cos⁡δD=(ss2-cs2sr2)(sa2-ca2)4casacssssr,(1b)cos⁡δD=(ss2sr2-cs2)(sa2-ca2)4casacssssr,for Z2s and Z¯2s respectively, where si≡sinθi and ci≡cos⁡θi. The latest global fits for the neutrino oscillation parameters from [2] are shown in Table 1.Table 1
Global fits for neutrino oscillation parameters from [2]. * represents a local minimum at approximately 0.42σ for χ2.
Parameter
Best fit
1σ range
sin
⁡
2
⁡
θ
s
/
1
0
-
1 (NH or IH)
3.08
2.91–3.25
sin
⁡
2
⁡
θ
r
/
1
0
-
2 (NH)
2.34
2.16–2.56
sin
⁡
2
⁡
θ
r
/
1
0
-
2 (IH)
2.39
2.18–2.60
sin
⁡
2
⁡
θ
a
/
1
0
-
1 (NH)
4.25
3.98–4.54
sin
⁡
2
⁡
θ
a
/
1
0
-
1 (IH)
4.37, 5.82*
4.08–4.96⊕ 5.31–6.10
δ
D
/
π (NH)
1.39
1.12–1.72
δ
D
/
π (IH)
1.35
0.96–1.59
m
21
2
/
1
0
-
5
e
V
2 (NH or IH)
7.54
7.32–7.80
m
31
2
/
1
0
-
3
e
V
2 (NH)
2.48
2.42–2.56
|
m
31
2
|
/
1
0
-
3
e
V
2 (IH)
2.36
2.29–2.43From this we can obtain a distribution forcos⁡δD following the procedure in [5, 6] by using
(2)dP(cos⁡δD)dcos⁡δD=∫‍δDpP(sa2)P(ss2)P(sr2)dsa2dss2dsr2,
where δDp≡δ(cos⁡δD-c¯D), the P’s are proportional to exp⁡(-χ2/2), and c¯D≡ RHS of (1a), (1b). Because it is preferable to get a distribution with respect to δD rather than cos⁡δD we use
(3)dP(δD)dδD=|sD|dP(cD)dcD,
where cD≡cos⁡δD and sD≡sinδD. Since this is a numerical integral, the delta function cannot be used as it is normally defined (unless integrated out of the equation prior to the numerical calculation). The integral was evaluated using a Monte Carlo algorithm and the results are shown in Figure 1(a). The domain of δD in (3) is [-180∘,0∘], but the distributions in Figure 1(a) can be reflected about δD=0∘ to account for the full interval [-180∘,180∘]. Therefore, these distributions have been normalized to 1/2 over the domain shown in the figures. This means that each of the residual symmetries will have two peak predictions for the CP phase (equidistant from 0∘). The IH χ2 curve for θa in [2] is closer to being symmetric about sin2θa=0.5. This is very prevalent in the results shown in Figure 1(a) given that the IH plots are close to being symmetric about δD=-90∘. But, since the NH global fit favors the lower octant for θa by at least 2σ [2] the predicted distributions for NH tend to prefer one side of δD=-90∘. But in both cases the results for Z2s are in agreement with the best fit value of δD=-90∘ from T2K’s latest results [1].Predicted distributions for (a)δD, (b) Jν, and (c) θa (NH) using the global analysis in [2].
(a)
(b)
(c)The same method is applied to the Jarlskog invariantJν≡casacssscr2srsD [7]; that is,
(4)dP(Jν)dJν=∫‍δJνpP(sa2)P(ss2)P(sr2)dsa2dss2dsr2,
with δJνp≡δ(Jν-casacssscr2srsD). This distribution is shown in Figure 1(b). When calculating these distributions, δD is taken to be in the interval [0,180∘] and is even about the vertical axis to extend δD to include [-180∘,0∘]. To account for this, the figures are labeled for the distribution of |Jν|, and they can therefore be normalized to one. As compared with our previous results in [6], Z¯2s is beginning to favor the region that Z2s prefers. Also, the region predicted by Z2s has become slightly narrower and it now excludes |Jν|<0.024.Finally, this method is again applied similarly toθa by first using (1a), (1b) to solve for tan2θa(5a)tan2θa=cs2sr2-ss22cssssrcos⁡δD,(5b)tan2θa=cs2-ss2sr22cssssrcos⁡δD,for Z2s and Z¯2s, respectively. Then we have
(6)dP(tan2θa)dtan2θa=∫‍δθapP(ss2)P(sr2)P(δD)dss2dsr2dδD,
with δθap≡δ(tan2θa-t¯θa), where t¯θa≡ RHS of (5a), (5b). To get a distribution for θa we use
(7)dP(θa)dθa=2sec2(2θa)dP(tan2θa)dtan2θa.
The distribution is shown in Figure 1(c), where plots are made with and without using the prior on δD from [2]. When no prior on δD is used, P(δD) becomes evenly distributed in [0,2π). As previously discussed in [6], θa is symmetric about θa=45∘ when there is no prior on δD. In addition, the distributions using the prior on δD have also become more symmetric, as a result of the χ2 for cos⁡δD also having become more symmetric about zero.


## 3.νμ to νe Oscillation

Now that we have a distribution for all the neutrino oscillation parameters, an attempt can be made to predict the results of an experiment measuring the number ofνμ’s that oscillate into νe’s over some distance. First, the expression for this probability, P(νμ→νe), must be found. Denoting the weak eigenstates of the neutrino by |να〉 and the neutrino mass eigenstates by |νi〉, then
(8)(UPMNS)αj≡〈να∣νj〉
defines the PMNS mixing matrix, UPMNS. The standard parametrization is given by [9]
(9)UPMNS=UP,
where
(10)U=(cscrsscrsre-iδD-ssca-cssasreiδDcsca-sssasreiδDsacrsssa-cscasreiδD-cssa-sscasreiδDcacr),P=diag⁡(1,eiα21/2,eiα31/2).
From [8],
(11)Amp(να⟶νβ)=∑i‍Uαi*e-imi2(L/2E)Uβi,
which leads to
(12)P(vα(-)⟶vβ(-))=δαβ-4∑i>j‍R(Uαi*UβiUαjUβj*)sin2(Δmij2L4E)(-)+2∑i>j‍I(Uαi*UβiUαjUβj*)sin(Δmij2L2E),
where Δmij2≡mi2-mj2, mi is the ith mass eigenvalue, L is the distance propagated by the neutrino, and E is the energy of the neutrino. Notice that this probability does not depend on the Majorana phases, and therefore a discussion on these phases will not be pursued here.Making the following definition [9]:
(13)Δij≡Δmij22EL
and noting that Δ32=Δ31-Δ21, then
(14)P(vμ(-)⟶ve(-))=4ss2cr2(ss2sr2sa2+cs2ca2-2cscasssrsacD)×sin2(Δ212)+4sr2sa2cr2sin2(Δ312)+2sssrcr2sa×(cscacD-sssrsa)×[4sin2(Δ212)sin2(Δ312)+sin⁡(Δ21)sin⁡(Δ31)](-)+4Jν[sin2(Δ212)sin(Δ31)hhhhhhh-sin2(Δ312)sin(Δ21)].
The last term includes the Jarlskog invariant [7] defined above.


### 3.1. Matter Effects

As electron neutrinos propagate through the earth, they can interact with electrons viaW-exchange. In addition, all three neutrino flavors can interact with electrons, protons, or neutrons via Z-exchange. Assuming electrically neutral matter, the Z-exchange between the neutrinos and protons will exactly cancel with the Z-exchange between the neutrinos and electrons [8]. The contribution from Z-exchange can be dropped, because it only adds a multiple of the identity matrix to the Hamiltonian [9]. Then, under the assumption that E≪MW, the effect of W-exchange can be accounted for by modifying the Hamiltonian for neutrinos [17]
(15)H=12EU(0000Δm212000Δm312)U†+12E(a00000000),
where a≡22GFNeE and Ne is the density of electrons. For antineutrinos, the Hamiltonian is simply the complex conjugate of (15) with a→-a.One way to proceed is to diagonalize the Hamiltonian exactly, which has been done analytically [17–19]. However, this does not give much physical insight into the effects of matter on neutrino oscillations. Approximations in which the mixing angles and mass eigenvalues are replaced by effective values do not modify any of the equations, and therefore it becomes clear how matter affects neutrinos. A number of approximation schemes have been developed [20–26]. One of the most commonly used of these are the equations derived in [26]. But, due to the large value of θr measured at Daya Bay [27], the approximation in [26] begins to fail as is shown in [9]. In the approximation that is used here, the form of (14) can be used with the following modifications [9]:
(16)θs⟶θs′,θr⟶θr′,Δm212⟶λ2-λ1,Δm312⟶λ3-λ1,
with (17a)tan(2θs′)=(Δm212/cr2)sin(2θs)(Δm212/cr2)cos⁡(2θs)-a,(17b)tan(2θr′)=(Δm312-Δm212ss2)sin(2θr)(Δm312-Δm212ss2)cos⁡(2θr)-a,(17c)λ±′≡((Δm212+acr2)(Δm212-acr2)2+4acr2ss2Δm212hλ±′hh±(Δm212-acr2)2+4acr2ss2Δm212)(2)-1,(17d)λ±′′≡(λ+(Δm312+asr2)[λ-(Δm312+asr2)]2+4a2scr2sr2hλ±′′hh±[λ-(Δm312+asr2)]2+4a2scr2sr2)(2)-1,where for neutrinos let
(18)λ≡λ+′,s≡ss′2,λ1≈λ-′,λ2≈λ∓′′,λ3≈λ±′′,
and for antineutrinos let
(19)λ≡λ-′,s≡cs′2,a⟶-a,λ1≈λ∓′′,λ2≈λ+′,λ3≈λ±′′,
with the upper sign for normal hierarchy and the lower sign for inverted hierarchy.It is helpful to showa and Δij in conventional units. Following [9] (20a)Δij=2.534(Δmij2[eV2])([GeV]E)(L[km]),(20b)a=(7.63×10-5[eV2])(ρ[g/cm3])(E[GeV]).


### 3.2.  NOνA and T2K

NOνA is a long-baseline neutrino oscillation experiment located in northern Minnesota. It has a baseline length of 810 km, an average matter density of 2.8 g/cm3 along this baseline, and a peak neutrino energy around 2 GeV [11]. T2K is another neutrino oscillation experiment with similar goals to that of NOνA. Its baseline length is 295 km and has an average matter density of 2.6 g/cm3, and the neutrino beam energy peaks around 0.6 GeV [28].With the use of the effective mixing angles derived in the previous section, the probability of the appearance of aνe(ν¯e) from a νμ(ν¯μ) beam can be determined for any matter density. Using the length and matter density for the two experiments in question, plots of these probabilities are shown in Figure 2 as a function of energy.P
(
ν
μ
→
ν
e
) as a function of energy at (a) NOνA and (b) T2K, using the best fits from [2] with normal hierarchy.
(a)
(b)It is not entirely apparent that the approximation [9] is valid for different values of the CP phase or the vacuum mixing angles; therefore, a comparison is made between this approximation and the exact results in the Appendix. In this comparison, the exact results are found by numerically diagonalizing the Hamiltonian. As it turns out, the approximation is very good for the energies and densities considered here.


## 3.1. Matter Effects

As electron neutrinos propagate through the earth, they can interact with electrons viaW-exchange. In addition, all three neutrino flavors can interact with electrons, protons, or neutrons via Z-exchange. Assuming electrically neutral matter, the Z-exchange between the neutrinos and protons will exactly cancel with the Z-exchange between the neutrinos and electrons [8]. The contribution from Z-exchange can be dropped, because it only adds a multiple of the identity matrix to the Hamiltonian [9]. Then, under the assumption that E≪MW, the effect of W-exchange can be accounted for by modifying the Hamiltonian for neutrinos [17]
(15)H=12EU(0000Δm212000Δm312)U†+12E(a00000000),
where a≡22GFNeE and Ne is the density of electrons. For antineutrinos, the Hamiltonian is simply the complex conjugate of (15) with a→-a.One way to proceed is to diagonalize the Hamiltonian exactly, which has been done analytically [17–19]. However, this does not give much physical insight into the effects of matter on neutrino oscillations. Approximations in which the mixing angles and mass eigenvalues are replaced by effective values do not modify any of the equations, and therefore it becomes clear how matter affects neutrinos. A number of approximation schemes have been developed [20–26]. One of the most commonly used of these are the equations derived in [26]. But, due to the large value of θr measured at Daya Bay [27], the approximation in [26] begins to fail as is shown in [9]. In the approximation that is used here, the form of (14) can be used with the following modifications [9]:
(16)θs⟶θs′,θr⟶θr′,Δm212⟶λ2-λ1,Δm312⟶λ3-λ1,
with (17a)tan(2θs′)=(Δm212/cr2)sin(2θs)(Δm212/cr2)cos⁡(2θs)-a,(17b)tan(2θr′)=(Δm312-Δm212ss2)sin(2θr)(Δm312-Δm212ss2)cos⁡(2θr)-a,(17c)λ±′≡((Δm212+acr2)(Δm212-acr2)2+4acr2ss2Δm212hλ±′hh±(Δm212-acr2)2+4acr2ss2Δm212)(2)-1,(17d)λ±′′≡(λ+(Δm312+asr2)[λ-(Δm312+asr2)]2+4a2scr2sr2hλ±′′hh±[λ-(Δm312+asr2)]2+4a2scr2sr2)(2)-1,where for neutrinos let
(18)λ≡λ+′,s≡ss′2,λ1≈λ-′,λ2≈λ∓′′,λ3≈λ±′′,
and for antineutrinos let
(19)λ≡λ-′,s≡cs′2,a⟶-a,λ1≈λ∓′′,λ2≈λ+′,λ3≈λ±′′,
with the upper sign for normal hierarchy and the lower sign for inverted hierarchy.It is helpful to showa and Δij in conventional units. Following [9] (20a)Δij=2.534(Δmij2[eV2])([GeV]E)(L[km]),(20b)a=(7.63×10-5[eV2])(ρ[g/cm3])(E[GeV]).


## 3.2.  NOνA and T2K

NOνA is a long-baseline neutrino oscillation experiment located in northern Minnesota. It has a baseline length of 810 km, an average matter density of 2.8 g/cm3 along this baseline, and a peak neutrino energy around 2 GeV [11]. T2K is another neutrino oscillation experiment with similar goals to that of NOνA. Its baseline length is 295 km and has an average matter density of 2.6 g/cm3, and the neutrino beam energy peaks around 0.6 GeV [28].With the use of the effective mixing angles derived in the previous section, the probability of the appearance of aνe(ν¯e) from a νμ(ν¯μ) beam can be determined for any matter density. Using the length and matter density for the two experiments in question, plots of these probabilities are shown in Figure 2 as a function of energy.P
(
ν
μ
→
ν
e
) as a function of energy at (a) NOνA and (b) T2K, using the best fits from [2] with normal hierarchy.
(a)
(b)It is not entirely apparent that the approximation [9] is valid for different values of the CP phase or the vacuum mixing angles; therefore, a comparison is made between this approximation and the exact results in the Appendix. In this comparison, the exact results are found by numerically diagonalizing the Hamiltonian. As it turns out, the approximation is very good for the energies and densities considered here.


## 4. Determination of the Mass Hierarchy and the Octant ofθa

As has been mentioned previously, a major goal of neutrino oscillation experiments is to determine the mass hierarchy. IfCP was a good symmetry, then there would be no observable difference between P(νμ→νe) and P(ν¯μ→ν¯e) when the neutrinos are propagating through a vacuum. However, interestingly enough, the matter effects discussed previously emulate the effects of CP-violation. Therefore, there is an observable difference between P(νμ→νe) and P(ν¯μ→ν¯e) even if CP is a good symmetry. Without the effects of matter the difference between oscillation probabilities for normal hierarchy versus inverted hierarchy is minimal. Thus it is because of the interactions with matter that allow for a discernible difference between normal and inverted hierarchy.It is possible that actualCP-violation is substantially cancelled by this matter induced CP-violation. This would be very unfortunate, because it would make the determination of the CP phase more difficult than expected. A plot for P(νμ→νe) versus P(ν¯μ→ν¯e) is shown in Figure 3 for NOνA and T2K using the best fits from [2]. It can be seen that there are many values of the CP phase that will allow NOνA to make a serious determination of the true mass hierarchy. This will occur if δD∈[π,2π] with NH being the true hierarchy or δD∈[0,π] with IH being the true hierarchy. And since T2K has excluded most of δD∈[0,π] at 90% C.L. [1], hopefully the true mass hierarchy is normal. From Figure 3(b) it appears that T2K will not be able to determine the mass hierarchy in this manner.Plot ofP(νμ→νe) versus P(ν¯μ→ν¯e) to show the sensitivity of (a) NOνA and (b) T2K to determine the mass hierarchy assuming θa<π/2. The red ellipse (lower right corner) corresponds to NH, and the blue ellipse (upper left corner) corresponds to IH.
(a)
(b)In addition, it may also be possible to determine the octant ofθa from similar plots. These are shown in Figure 4. It appears that every value of the CP phase could at least give some indication of the true octant of θa, but the best values would be δD=0 for the lower octant and δD=π for the higher octant.Plot ofP(νμ→νe) versus P(ν¯μ→ν¯e) to show the sensitivity of (a) NOνA and (b) T2K to determine the octant of θa assuming inverted hierarchy. The red ellipses (lower left corner) correspond to θa<π/4, while the blue ellipses (upper right corner) correspond to θa>π/4. The dashed ellipses correspond to the ±1σ values.
(a)
(b)The ellipses were created by using (14) with the matter effect modifications of (16), for all possible values of δD (i.e., δD∈[0,2π]). The □ and the ▵ symbols correspond to the predicted values for δD, based on Z2s and Z¯2s, respectively. The predicted values are determined by using the best fits from [2] in (1a), (1b).


## 5. Effective Masses and Mixing Angles in Matter

The values of the effective mixing angles are plotted in Figure5 and the mass eigenvalues in Figure 6, as functions of energy using the matter density for the NOνA experiment. The plots for T2K are excluded here, because they do not differ much from the ones for NOνA. Also, these particular plots consider δD=0, because the results depend very little on the CP phase. These have been plotted by numerically diagonalizing the Hamiltonian. It is assumed that the diagonalization matrix will have the same form as the standard parameterization of the PMNS mixing matrix.Plots of the effective mixing angles as a function of energy using data from [2]. For (a) NOνA and neutrinos, (b) NOνA and antineutrinos. Red =θs′, blue =θa′, and green =θr′. The solid lines are for normal hierarchy, and the dashed lines are for inverted hierarchy. In the cases where the dashed line is not visible, it’s because the solid line is on top of it.
(a)
(b)Effective masses for NOνA. The major focus of these plots should be on the solar and atmospheric resonances corresponding to a level repulsion. (a) ν and NH, (b) ν and IH, (c) ν¯ and NH, and (d) ν¯ and IH. Red =λ1, blue =λ2, green =λ3, cyan-dashed =sin2(2θs), and magenta-dashed =sin2(2θr).
(a)
(b)
(c)
(d)The approximation introduced in Section3.1 implies that the CP phase and θa′ do not vary much, if at all, due to interactions with matter (which can be observed in Figure 5). It also implies certain characteristics of the variations of the other two mixing angles. From (17a), θs′ should be independent of the mass hierarchy, and taking the limit a→∞, then θs′→π/2 (0) for ν (ν¯). This behavior is easily observed in Figure 5. From (17b), θr′ should have similar asymptotic behavior as θs′ for normal hierarchy, while it should reverse its behavior for inverted hierarchy. These features are approximately shown in Figure 5, but at the energies shown, θr′ is not able to approach its asymptotic limit. Therefore, these results appear to agree with the approximation in [9].The effective neutrino masses are found from multiplying the eigenvalues of the Hamiltonian by2E. These plots are shown in Figure 6 for NOνA. There are some interesting characteristics of these plots. The first and most obvious are two resonances referred to as the solar resonance and the atmospheric resonance which represent the condition for maximal oscillation probability. This phenomenon was first understood with the introduction of the MSW effect [14, 15]. The first peak of sin2(2θs′) is the solar resonance and corresponds to an approach of |λ1| and |λ2| followed by a repulsion. The first peak of sin2(2θr′) is the atmospheric resonance and corresponds to an approach of |λ2| and |λ3| followed by a repulsion. If the absolute value of the mass eigenvalues crosses, then no resonance can be seen there. If we do not take the absolute value of the mass eigenvalues, then they will never cross each other. This is a wonderful example of level repulsion in quantum mechanics. For more details on these resonances, including a derivation of the resonance condition, see [14–16, 29].


## 6. Conclusions

Predicted distributions forδD, Jν, and θa were updated using the residual symmetries Z2s and Z¯2s. It was found that the greater uncertainty in the octant of θa for IH shown in [2] forced the distributions of δD for IH to have nearly equal contributions on either side of δD=-90∘. This had no significant effect on the distribution for Jν and the prediction for Jν has improved.By including the effects of matter into the oscillation probabilities, it was shown in Section4 how NOνA stands a good chance of determining the mass hierarchy if δD∈[π,2π] and the true hierarchy is normal or if δD∈[0,π] and the true hierarchy is inverted. It was also shown that both NOνA and T2K may be capable of nailing down the octant of θa.The effects of matter were also shown to give rise to two resonances: the solar resonance and the atmospheric resonance. This behavior can be seen to agree with the approximation used throughout this work [9].



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