T2K Experiment Results & Prospects

T2K ExperimentResults & Prospects

Alfons WeberUniversity of Oxford &

STFC/RAL

For the T2K Collaboration

FLASY2014

Content

• Neutrino Oscillations– Introduction

• The T2K Experiment– Beam – Near Detector– Far Detector

• Results – Disappearance analysis– Appearance search

• Future potential– The hunt for CP-violation

Jun-2014 A.Weber, FLASY2014, Brighton 2

FLASY2014

Neutrino MixingThe PMNS Matrix

• Assume that neutrinos do have mass:– mass eigenstates weak interaction eigenstates– Analogue to CKM-Matrix in quark sector!

1

2

3

e

U

weak“flavour eigenstates”

Mass eigenstatesm1, m2, m3

Unitary mixing matrix:3 mixing angles

& complex phases

Pontecorvo-Maki-Nakagawa-Sakata

2 2ijwith cos( ), sin , mixing angle and mass differenceij ij ij ij ijc s (θ ) θ Δm

2

3

1 2 3 13 13 12 12

1 2 3 23 23 12 12

1 2 3 23 23 13 13

1 0 0 0 0 1 0 0

0 0 1 0 0 0 0

0 0 0 0 1 0 0

ie e e

i

ii

U U U c s e c s

U U U U c s s c e

U U U s c s e c e

3Jun-2014 A.Weber, FLASY2014, Brighton

FLASY2014

Oscillation Signatures

Jun-2014 4A.Weber, FLASY2014, Brighton

, or e 1 2 3, ,

e appearance: determine 13 constrain dCP disappearance: determine 23 and m232

Reconstructed ν Energy (MeV) Reconstructed ν Energy (MeV)Reconstructed ν Energy (MeV)

Eve

nts

Rat

io o

f ob

s/ex

pect

ed

FLASY2014

The T2K Experiment

• A Long-baseline Experiment to study neutrino oscillations– Baseline 295 km– Beam power up to 230 kW– Detectors Near and far


FLASY2014

Producing Neutrinos

6

π→μν118 m

off-axis (2.5°)

(30 GeV from MRsynchrotron)

0º

Jun-2014

2 2

0.431

EE π

νγ θ

A.Weber, FLASY2014, Brighton

Using NA61 data to constrain

hadron production

FLASY2014

Data Taken

• Data Set: 6.57 x 1020 PoT (8% of design goal)• Increase power in future

– More protons / bunch– Higher repetition rate


FLASY2014

ND280 detector

• Off-axis: ND280– 0.2 T magnet (UA1/NOMAD)– Plastic scintillator detectors:

Fine Grained Detector (FGD), π0 detector (P0D), ECals and SMRD, Time projection chambers (TPC)

• On-axis: INGRID

8Jun-2014

νμ

FGD2FGD2

TPC3TPC3TPC2TPC2TPC1TPC1

FGD1FGD1


FLASY2014

Some ND distribution

• Select different event classes in near detector– Negative muon & something/nothing

• Constrains flux and cross section uncertainties


CC 1π+CC 0π CC Other

BEFO

RE F

ITAF

TER

FIT

FLASY2014

Reduced Systematics


FLASY2014

Far Detector


FLASY2014

Far Detector Events


FLASY2014

Electron Neutrino Appearance

• Event Selection– Fully contained, – no π0

– No decay electrons


FLASY2014

Appearance Result


Phys. Rev. L

ett. 112, 061802

(2014)

FLASY2014

Compare with Reactors


• Comparing with reactor measurements• best overlap is for the

normal hierarchy δcp=–π/2.

• Need to increase θ23 to account for high event rate Note: Marginalized

over 23 and m232

Lucky point!

FLASY2014

Disappearance Measurement


Maximal mixing is not the same as maximumdisappearance if θ13 is not zero!

NH: sin2(θ23) = 0.514NH: Δm2

32 = 2.51x10-3 eV2

120 selected events

FLASY2014

The World Scene


Best-fit ± FC 68% CL (Δm2 units 10-3 eV2/c4)

NHsin2θ23 0.514+0.055

-0.056

Δm232 2.51 ± 0.10

IHsin2θ23 0.511 ± 0.055

Δm213 2.48 ± 0.10

FLASY2014

Putting it All Together


FLASY2014

The width of the beam is comparable to the measured Gaussians in the previous runs.

ND280 anti-ν event

The detectors are all working well.

Here is our first identified anti-neutrino event from an anti-neutrino test run!

Measured with INGRID

μ+

Run Status


FLASY2014

Future Sensitivity

No systematics

5% error on signal, 10% on background

T2K best sensitivity: 50% ν/50% anti-ν Anti-nu running: large new physics program.

50% ν/50% anti-ν (true NH)100% ν (true NH)

50% ν/50% anti-ν (true NH)w/ Reactor constraint

100% ν (true NH)w/ Reactor constraint

“Lucky! (+: Sin22θ=0.1, δCP=-90)”

NH

T2K: 50% ν/50% anti-ν


FLASY2014

Future Sensitivity (II)

50% ν/50% anti-ν (true NH)

50% ν/50% anti-ν (true NH)w/ Reactor constraint

100% ν (true NH)w/ Reactor constraint

100% ν (true NH)

“Unlucky! (+: Sin22θ=0.1, δCP=0)”


FLASY2014

T2K and NOvA

T2K: 50% ν/50% anti-ν

NH IH

No systematics

5% error on signal, 10% on background


FLASY2014

Summary and Conclusion

• T2K has taken 8% of its nominal PoT• World leading results

– 7.3σ electron neutrino appearance– Most precise measurement of θ23

• Combination with reactor measurements– Hint that δCP = -π/2

• Improved sensitivity with data to come– Can be lucky to “discover” CP violation

• More results to come– Cross sections, sterile neutrinos, exotics…


Backup

FLASY2014

Who is Who

Jun-2014 25

νμ disappearance

ν–less double beta decay

Solar neutrino oscillation

νe disappearance inνμ beam Or

reactor neutrino experiments


FLASY2014

Ubi es?

26

Normal Hierarchy or Inverted Hierarchy?Open questions:

smaller) little a(or 45

eV104.2

23

23232

m

?0

?232

m

Jun-2014 A.Weber, FLASY2014, Brighton

913

FLASY2014

NA61/SHINE

• hadron(π, K) yield – 30 GeV p + C

• High-acceptance – ToFs and spectrometers

• 2cm thin target (4%λI)• π+ analysis:

– dE/dx only analysis low momenta (Phys.Rev.C84.2011.034604)

– dE/dx+ToF analysishigh momenta(Phys.Rev.C85.2011.035210)

27

~13m

~1

0m


FLASY2014

Predicted Flux

• Primary pions modelled with NA61 data

• νμ flux– Pions dominant at low energy– Kaons important in tail

• νe flux – For low energy from muons

28

νμ

νμνe


FLASY2014

CC Interaction


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T2K Experiment Results & Prospects

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