Future Sensitivity of the T2K ExperimentFor the RCCN Workshop

Megan Friend

KEK

March 15, 2013

Outline

1 The T2K ExperimentPhysics GoalsStatus

2 Recent T2K Results2012 Appearance Results2013 Disappearance Results

3 T2K Future SensitivityAllowed Region Contourssin2 θ23 Octant Discrimination SensitivityT2K + NOνA SensitivityOscillation Parameter Precision vs. POT

0 / 21

The T2K Experiment – Physics GoalsThe physics goals of the first phase of T2K are (from LOI):

1 “... a factor of 20 more sensitive search for νµ → νeappearance: sin2 2θµe ≃ 0.5 sin2 2θ13 > 0.003 ...”

2 “... an order of magnitude better precision in the νµ → ντoscillation measurement:δ(∆m

223) = 10−4 eV2 and δ(sin2 2θ23) = 0.01 ...”

3 “... a confirmation of the νµ → ντ oscillation or discovery ofsterile neutrinos by detecting the neutral current events ...”

• Requested: 750 kW × 5e7 s (115 days × 5 years) at30 GeV = 7.80 × 1021 POT

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The T2K Experiment – Physics GoalsThe physics goals of the first phase of T2K are (from LOI):

1 “... a factor of 20 more sensitive search for νµ → νeappearance: sin2 2θµe ≃ 0.5 sin2 2θ13 > 0.003 ...”

2 “... an order of magnitude better precision in the νµ → ντoscillation measurement:δ(∆m

223) = 10−4 eV2 and δ(sin2 2θ23) = 0.01 ...”

3 “... a confirmation of the νµ → ντ oscillation or discovery ofsterile neutrinos by detecting the neutral current events ...”

• Requested: 750 kW × 5e7 s (115 days × 5 years) at30 GeV = 7.80 × 1021 POT

→ Must update the T2K experimental goals following:

• Indication of νe appearance by T2K

• Discovery of an unexpectedly large θ13

• Precise measurement of sin2 2θ13 by reactor experiments1 / 21

The T2K Collaboration

∼500 members from 56 institutes in 11 countries2 / 21

The T2K Experiment Long Baseline

Neutrino Oscillation Experiment

• Primarily νµ, 2.5◦ off axis neutrino beam produced at J-PARC

• ND280 Near Detector – 280 m from ν source• Constrains systematic errors• Measures ν cross sections and beam backgrounds

• νµ → νe and νµ → νµ events detected at theSuper-Kamiokande (SK) far detector 295 km away

• 22.5 kT fiducial volume water Cherenkov detector• Good performance of νe/νµ particle ID for sub-GeV energy ν’s

3 / 21

The T2K Experiment – Current Status

• Current total integrated POT: ∼ 5.63× 1020

→ Now stably running at 230 kW!→ Currently at ∼7% of T2K full statistics

• Recently released appearance and disappearance results at3.01 × 1020 POT (∼4% of T2K full statistics)

• Expect 7.5-8×1020 POT by August – hoping for a 5σ νeappearance observation

• Plan to update results this summer4 / 21

The T2K Experiment – Recent νµ → νe

Appearance ResultsFirst evidence of νe appearance! – released at ICHEP last year

• Observed 11 νe candidate eventsfor 3.01× 1020 POT in 2012

• Expect 3.28 events if noνµ → νe oscillation – 3.2σ!

• Hope to reach 5σ this summer

13θ22sin0 0.1 0.2 0.3 0.4

CP

δ

-2

0

2

68% C.L.90% C.L.Best fit

(3.010e20 POT)Run1+2+3 data

normal hierarchy

2 eV-310×|=2.4322m∆|

Normal Hierarchy

13θ22sin0 0.1 0.2 0.3 0.4

CP

δ

-2

0

2

68% C.L.90% C.L.Best fit

(3.010e20 POT)Run1+2+3 data

inverted hierarchy

2 eV-310×|=2.4322m∆|

Inverted Hierarchy

5 / 21

The T2K Experiment – Recent νµ → νµ

Disappearance ResultsNew results released this year with 3.01 × 1020 POT

)23θ(22sin0.82 0.84 0.86 0.88 0.9 0.92 0.94 0.96 0.98 1

)4/c2

| (eV

2 32m∆|

0.0018

0.002

0.0022

0.0024

0.0026

0.0028

0.003

0.0032

0.0034

0.0036

0.0038 90% CLνT2K Likelihood ratio 3

90% CLνT2K Max likelihood 3

90% CLνMINOS 2012 2

90% CLνSuperK 2012 L/E 2

90% CLνSuperK 2012 zenith 3

90% CLνT2K Likelihood ratio 3

90% CLνT2K Max likelihood 3

90% CLνMINOS 2012 2

90% CLνSuperK 2012 L/E 2

90% CLνSuperK 2012 zenith 3

90% CLνT2K Likelihood ratio 3

90% CLνT2K Max likelihood 3

90% CLνMINOS 2012 2

90% CLνSuperK 2012 L/E 2

90% CLνSuperK 2012 zenith 3

• World’s most precisemeasurement of sin2 2θ23!

• T2K result consistent withmaximal mixing→ Best fit values:

• sin2 2θ23 = 1.00• |∆m

232| = 2.45× 10−3 eV2

6 / 21

νµ → νe Oscillation Probability

Precise measurement of sin2 2θ13 enhances the T2K sensitivity toδCP and the θ23 octant:

(νµ disappearance measures sin2 2θ23and cannot distinguish the octant alone)

P(νµ → νe) = 4C 213S

213S

223 sin

2 Φ31

(

1 +2a

∆m231

(1− 2S213)

)

→ Leading, matter effect

+ 8C 213S12S13S23(C12C23 cos δ − S12S13S23)cosΦ32 sin Φ31 sin Φ21 → CP conserving

− 8C 213C12C23S12S13S23 sin δ sin Φ32 sin31 sin Φ21 → CP violating

+ 4S212C

213(C

212C

223 + S

212S

223S

213 − 2C12C23S12S23S13 cos δ) sin

2 Φ21 → Solar

− 8C 213S

213S

223(1− 2S2

13)aL

4Ecos Φ32 sin Φ31 → Matter effect

(Cij = cos θij , Sij = sin θij , Φij = ∆m2ijL/4E )

• δCP completely unknown• MH completely unknown• θ12 = 33.6◦ ± 1.0◦

• θ23 = 45◦ ± 6◦ (90% C.L.) – is θ23 maximal?• θ13 = 9.1◦ ± 0.6◦ – from reactor

7 / 21

T2K Future Sensitivity Study

• T2K combined 3 flavor appearance + disappearance fits• Simultaneously fit MC SK reconstructed energy spectra for

νe , νµ, ν̄e , and ν̄µ• Maximum likelihood fit• Uncertainties on sin2 2θ13, δCP , sin

2 θ23, and ∆m232 are

considered in plots shown• Results shown assume sin2 2θ13 = 0.1, δCP = 0, sin2 θ23 = 0.5,

and ∆m232 = 2.4× 10−3eV2 unless otherwise stated

• NH assumed

• Systematic errors shown are current T2K systematic errors• ∼10% for νe , ∼13% for νµ• ν̄ errors estimated as equal to ν errors with an additional 10%

normalization uncertainty

• Fits shown are done with and without a reactor constraintbased on the expected ultimate precision of Daya Bay +RENO + Double Chooz on sin2 2θ13 (= 0.1± 0.005)

• All studies shown are a work in progress

8 / 21

SK Reconstructed Energy Spectra at T2K

Full POT

Reconstructed Energy (GeV)0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2E

vent

s / 5

0 M

eV /

7.8e

21 P

OT

0

5

10

15

20

25 Totaleν → µνSignal

eν → µνSignal

eν + eνBeam

µν + µνBeam

Reconstructed Energy (GeV)0 1 2 3 4 5 6 7 8 9 10E

vent

s / 5

0 M

eV /

7.8e

21 P

OT

0

10

20

30

40

50

60

70 Totalµνµν

eν + eν

νe Appearance νµ Disappearance

ν-Running

Reconstructed Energy (GeV)0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2E

vent

s / 5

0 M

eV /

7.8e

21 P

OT

0

1

2

3

4

5

6

7

8 Totaleν → µνSignal

eν → µνSignal

eν + eνBeam

µν + µνBeam

Reconstructed Energy (GeV)0 1 2 3 4 5 6 7 8 9 10E

vent

s / 5

0 M

eV /

7.8e

21 P

OT

0

5

10

15

20

25

30

Totalµνµν

eν + eν

ν̄-Running

9 / 21

ν vs. ν̄ Running, Ultimate T2K 90%

Allowed Region

ν̄ data can give us additional information (about δCP , etc.)although it comes at the cost of lower statistics→ Must optimize the ν-ν̄ running ratio

100% ν 100% ν̄

No sys. err.

10 / 21

T2K in the Post θ13 Era – Ultimate T2K

90% Allowed Region if δCP = 0Dashed: no sys. err., Solid: with current sys. err.

True MH is NH; contours drawn for two MH assumptions

13θ22sin0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18

CP

δ

-150

-100

-50

0

50

100

150

13θ22sin0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18

CP

δ

-150

-100

-50

0

50

100

150

NHIH

100% ν 50% ν, 50% ν̄

Work in Progress

11 / 21

T2K in the Post θ13 Era – Ultimate T2K

90% Allowed Region if δCP = 0Dashed: no sys. err., Solid: with current sys. err.

True MH is NH; contours drawn for two MH assumptions

13θ22sin0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18

CP

δ

-150

-100

-50

0

50

100

150

13θ22sin0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18

CP

δ

-150

-100

-50

0

50

100

150

NHIH

100% ν 50% ν, 50% ν̄

13θ22sin0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18

CP

δ

-150

-100

-50

0

50

100

150

13θ22sin0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18

CP

δ

-150

-100

-50

0

50

100

150

With Reactor

Work in Progress

11 / 21

T2K in the Post θ13 Era – Ultimate T2K

90% Allowed Region if δCP = −90Dashed: no sys. err., Solid: with current sys. err.

True MH is NH; contours drawn for two MH assumptions

13θ22sin0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18

CP

δ

-150

-100

-50

0

50

100

150

13θ22sin0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18

CP

δ

-150

-100

-50

0

50

100

150

NHIH

100% ν 50% ν, 50% ν̄

Work in Progress

12 / 21

T2K in the Post θ13 Era – Ultimate T2K

90% Allowed Region if δCP = −90Dashed: no sys. err., Solid: with current sys. err.

True MH is NH; contours drawn for two MH assumptions

13θ22sin0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18

CP

δ

-150

-100

-50

0

50

100

150

13θ22sin0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18

CP

δ

-150

-100

-50

0

50

100

150

NHIH

100% ν 50% ν, 50% ν̄

13θ22sin0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18

CP

δ

-150

-100

-50

0

50

100

150

13θ22sin0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18

CP

δ

-150

-100

-50

0

50

100

150

With Reactor

Work in Progress

12 / 21

T2K in the Post θ13 Era – Ultimate T2K

90% Allowed Region if sin2 θ23 = 0.39

Dashed: no sys. err., Solid: with current sys. err.True MH is NH; contours drawn for two MH assumptions

23θ2sin0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7

322 m∆

2.2

2.25

2.3

2.35

2.4

2.45

2.5

2.55

2.6-310×

23θ2sin0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7

322 m∆

2.2

2.25

2.3

2.35

2.4

2.45

2.5

2.55

2.6-310×

NHIH

100% ν 50% ν, 50% ν̄

Work in Progress

13 / 21

T2K in the Post θ13 Era – Ultimate T2K

90% Allowed Region if sin2 θ23 = 0.39

Dashed: no sys. err., Solid: with current sys. err.True MH is NH; contours drawn for two MH assumptions

23θ2sin0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7

322 m∆

2.2

2.25

2.3

2.35

2.4

2.45

2.5

2.55

2.6-310×

23θ2sin0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7

322 m∆

2.2

2.25

2.3

2.35

2.4

2.45

2.5

2.55

2.6-310×

NHIH

100% ν 50% ν, 50% ν̄

23θ2sin0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7

322 m∆

2.2

2.25

2.3

2.35

2.4

2.45

2.5

2.55

2.6-310×

23θ2sin0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7

322 m∆

2.2

2.25

2.3

2.35

2.4

2.45

2.5

2.55

2.6-310×

With Reactor

sin2 θ23 octant determination!

Work in Progress

13 / 21

sin2 θ23 Octant Discrimination vs. POT

Dashed: 90%, Solid: 3σ, no sys. error

POT21 10×0 1 2 3 4 5 6 7 8 9 10

23θ2si

n

0.35

0.4

0.45

0.5

0.55

0.6

0.65

ν:νOctant Resolved, 1:0 ν:νOctant Resolved, 1:0

POT21 10×0 1 2 3 4 5 6 7 8 9 10

23θ2si

n

0.35

0.4

0.45

0.5

0.55

0.6

0.65

ν:νOctant Resolved, 1:1 ν:νOctant Resolved, 1:1

Unknown MH

POT21 10×0 1 2 3 4 5 6 7 8 9 10

23θ2si

n

0.35

0.4

0.45

0.5

0.55

0.6

0.65

ν:νOctant Resolved, 1:0 ν:νOctant Resolved, 1:0

POT21 10×0 1 2 3 4 5 6 7 8 9 10

23θ2si

n

0.35

0.4

0.45

0.5

0.55

0.6

0.65

ν:νOctant Resolved, 1:1 ν:νOctant Resolved, 1:1

Known MH

Stat. error only; constrained by the ultimate reactor sensitivity

Work in Progress

14 / 21

Fits to T2K + NOνA Combined

The NOνA experiment:

• Plans to start taking data this May with a partial detector

• Expected POT is 3.6× 1021 POT in 6 years

• Baseline length: 810 km (295 km for T2K) – more sensitiveto matter effects than T2K

• Different baselines means different sensitivities!

• Detector mass: 15 kT (22.5 kT for T2K)

The combined fit:

• GLoBES (General Long Baseline Experiment Simulator) usedin combined fits

• A constraint based on the ultimate reactor precision is used

• No systematic error used in this comparison/combination

15 / 21

δCP and MH 90% Sensitivity – T2K Only

16 / 21

δCP and MH 90% Sensitivity – NOνA Only

17 / 21

δCP and MH 90% Sensitivity –

T2K + NOνA Combined

18 / 21

T2K sin2 θ23 1σ Precision vs. POTDashed: no sys. err., Solid: with current sys. err.

POT21 10×0 1 2 3 4 5 6 7 8 9 10

wid

thσ

1

23θ2si

n

0.03

0.04

0.05

0.06

0.07

0.08

0.09

= 0CPδ = 90CPδ

POT21 10×0 1 2 3 4 5 6 7 8 9 10

wid

thσ

1

23θ2si

n

0.03

0.04

0.05

0.06

0.07

0.08

0.09

= 0CPδ = 90CPδ

100% ν 50% ν, 50% ν̄

POT21 10×0 1 2 3 4 5 6 7 8 9 10

wid

thσ

1

23θ2si

n

0.03

0.04

0.05

0.06

0.07

0.08

0.09

Known MH

Unknown MH

POT21 10×0 1 2 3 4 5 6 7 8 9 10

wid

thσ

1

23θ2si

n

0.03

0.04

0.05

0.06

0.07

0.08

0.09

Known MH

Unknown MH

Work in Progress

δCP = 0

Constrained by the ultimate reactor sensitivity19 / 21

T2K ∆m232 1σ Precision vs. POT

Dashed: no sys. err., Solid: with current sys. err.

POT21 10×0 1 2 3 4 5 6 7 8 9 10

wid

thσ

1

322m∆

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14-310×

= 0CPδ = 90CPδ

POT21 10×0 1 2 3 4 5 6 7 8 9 10

wid

thσ

1

322m∆

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14-310×

= 0CPδ = 90CPδ

100% ν 50% ν, 50% ν̄

POT21 10×0 1 2 3 4 5 6 7 8 9 10

wid

thσ

1

322m∆

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14-310×

Known MH

Unknown MH

POT21 10×0 1 2 3 4 5 6 7 8 9 10

wid

thσ

1

322m∆

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14-310×

Known MH

Unknown MH

Work in Progress

δCP = 0

Constrained by the ultimate reactor sensitivity20 / 21

Conclusion

T2K recent results and current status:

• 3.2σ evidence of νe appearance!

• World record on precision of sin2 2θ23!• T2K’s most recent results are with 3.01× 1020 POT• Currently have taken ∼ 0.54× 1021 POT (∼ 7% of the total

approved 7.8× 1021 POT)

• Collaboration is beginning to discuss the optimal ratio for ν:ν̄running – may take ν̄ data this year

T2K future sensitivity:

• At the full statistics (2021), T2K has sensitivity for δCP ,non-maximal θ23, and θ23 octant

• Also has sensitivity to MH and other increased sensitivitieswhen combined with the NOνA experiment

21 / 21