Review of Accelerator Neutrino Results · Review of Accelerator Neutrino Results CHRIS WALTER, DUKE...

Review of Accelerator Neutrino Results CHRIS WALTER, DUKE UNIVERSITY

GGI Neutrino Conference June 25th 2012

Sidereus Nuncius – Galileo (1610)

06/25/12 2 Chris Walter -‐ GGI Neutrino Conference

June 2012: Where do we stand?

•  The measurement of non-‐zero θ13 has changed the nature of discussions and presentaGons about the current experiments.

•  I’ll concentrate on results from the neutrino conference. •  Emphasis on Long-‐baseline: T2K, MINOS, OPERA, with some

Miniboone and a bit of atmospheric neutrinos also. •  I’ll go over some experimental issues related to the accelerator

experiments.

Neutrino 2010: Athens Neutrino 2012: Kyoto

06/25/12 3 Chris Walter -‐ GGI Neutrino Conference

The θ13 Story Signal ε = 66%

Six events seen 1.5 ± 0.3 expected P-‐value: .007

T2K + Minos + Double Chooz (θ13≠0)

Daya Bay + Reno precision measurement (θ13≠0 at 5σ!)

R = .940 ± .011 ± .044 Clear deficit like osc!

On and Off-Axis Beams

0

50

100

150

200

250

300

350

400

0En (GeV)

at 295 km

2ºAll

1 2 3 4 5

High Energy tail causes Backgrounds

Peak flux is higher and energy band is narrower.

Θ=2.5°

Super-‐Kamiokande Off Axis (2.5°) Neutrino Source

π

120m 0m 280m 295 km

on-axis off-axis

monitor

Proton Beam Neutrino Beam

The kinema^cs of pion decay allow us to make a narrower neutrino beam.

4 06/25/12 Chris Walter -‐ GGI Neutrino Conference

Epion (GeV)

E ν (G

eV)

How do we measure θ13?

For appearance three main types of background: intrinsic νe , misidentified π0, mis-identified charged µ

We need a very high intensity beam and a large target. Make a pure neutrino beam and look for electrons to appear.

Measure the electron appearance probability on top of a background

Schematic figure

P(νµ →νe ) = sin2θ23 sin2 2θ13 sin2 Δm232 L

4Eν+ sub-leading terms


νe appearance is crucial for studying the MH and CPV!

Main νe Appearance backgrounds

Intrinsic νe contamination

Confuse π0→γγ with νe

Confuse νµ with νe


Eν ReconstrucGon (assuming QE)

In Cherenkov detectors not every parGcle is above Cherenkov threshold. Luckily, in a Quasi-‐ElasGc reacGon, even if only the muon is visible we can reconstruct the neutrino energy! [ Case for most events in T2K/MiniBooNE Energies ] If the interacGon is non Quasi-‐ElasGc then the reconstructed energy will be incorrect.

µ νµ θ

E� =mNEµ �m2

µ/2mN � Eµ + pµ cos(�µ)

mN = Neutron MassEµ = Muon Energy

mµ = Muon masspµ = Muon momentum

�µ = Muon angle wrt beam


§  Run 1-3 data set contain 2.56 x 1020 POT (1.8 × previous result)

§  Run 1 (2) instantaneous power reached 50 kW (145 kW)

§  Earthquake March 11. JPARC restarted in Jan. T2K in March

§  Run 3 stable power reached 190 kW

T2K Experiment (Analysis Update)

POT 3.2% of final design goal

RUN 1 6 bunches / pulse spill / 3.64 sec

RUN 2 8 bunches / pulse spill / 3.04 sec


RUN 3 8 bunches / pulse spill / 3.04 sec (18% 200 kA)

earthquake recovery

Super-K water Cherenkov detector as far detector. Uses the JPARC accelerator complex 295 km away

T2K Evidence of νe Appearance

06/25/12 Chris Walter -‐ GGI Neutrino Conference

9

Ten events selected P-‐Value:.08% (3.2σ)

NH:

IH:

sin22θ13 68% CL @ δ=0

SystemaGc errors now of order 10%, 3 analyses

T2K νμ Results

Chris Walter -‐ GGI Neutrino Conference 10 06/25/12

0

50

100

150

200

250

300

350

400

0En (GeV)

at 295 km

2ºAll

1 2 3 4 5

Even with limited staGsGcs, shows the power of the off-‐axis technique.

OLD Result: Phys. Rev. D 85 1311030(R)

06/25/12 10

“Final” MINOS Results

06/25/12 Chris Walter -‐ GGI Neutrino Conference 11

Near 1 kton Far 5.4 kton

735 km

Updated results: 10.71 x 1020 pot neutrino 3.36 x 1020 pot anti-neutrino 37.9 kton-years atmospheric

Use staGsGcal separaGon based on a papern matching library

Appearance:

R.Nichol (UCL)

MINOS anG-‐ν


The anG-‐neutrino / neutrino tension shown and neutrino 2010 has disappeared with data.

NH: 0.053, range 0.02-0.09 IH: 0.094, range 0.05-0.15

MINOS Atmospheric Parameters


Shiq caused by new neutrino beam data

OPERA tau appearance experiment

06/25/12 Chris Walter -‐ GGI Neutrino Conference

M. Nakamura (Nagoya)

Electronic trackers point Back to bricks.

Signal

Uses ECC (Emulsion Cloud Chamber) With automatic scanning + Magnetic spectrometer.

14

(also reported on nue search)

Opera – New Tau Event


Pb

Emulsion layers

1 mm

µ-

νµ C-

_

µ+

Charm background is well modeled Background

Background and efficiency sGll under study

Analyzing now

Super-‐K Evidence for Tau Appearance


New data + perform 2D un-‐binned likelihood fit of signal and background. hpp://arxiv.org/1206.0328 (submiped to PRL)

Log of Visible Energy3 3.5 4 4.5 50

100

200

300

400

500

ID of Maximum Energy Ring-200 -150 -100 -50 0 500

500

1000

1500

Number of Decay Electrons0 2 4 6 80

200400600800

100012001400

Max Distance to Decay-e0 2000 4000 60000

500

1000

1500

2000

Clustered Sphericity0 0.2 0.4 0.6 0.8 10

100

200

300

Ring Candidates0 5 10 15 200

50100150200250300

Fraction Carried in First Ring0 0.2 0.4 0.6 0.80

100

200

300

400

NormTau =1.42± 0.35(stat ) −0.12 (sys)+0.14 P-Value: 6.16 x 10-5 = 3.8 sigma

Corresponds to observed signal: 180.1 +- 44.3 (stat) +17.8 -15.2 è We can reject the no-appearance hypothesis.

)θcos(-1 -0.5 0 0.5 1

Even

ts

100

200

300

Tau Like

NN output0 0.2 0.4 0.6 0.8 1

100

200

300

400

Up-going

)θcos(-1 -0.5 0 0.5 1

Even

ts

0

100

200

300

400

500

Non-tau Like

NN output0 0.2 0.4 0.6 0.8 10

200

400

600

Down-going

MiniBooNE RESULTS


Phys. Rev. Lep. 98, 231801 (2007), arXiv:0704.1500 [hep-‐ex]

475 < Eν < 1250 MeV 380 events Exp: 358±19±35 events 0.55 σ Difference

2 neutrino oscillaGon in the LSND region Excluded at 98%

What’s going on here?

Search for electron appearance in the LSND region (541m baseline)

HISTORY ~2008

LSND Beam excess

C. Polly (FNAL)

MiniBooNE with doubled anG-‐νs


With new staGsGcs ν and anG-‐ν look very similar. REMOVE the energy cut.

Neutrinos: Fit > 200 MeV & Fit > 450 MeV Inconsistent (allowed region vs limit)

Anti-Neutrinos: Fit > 200 MeV & Fit > 450 MeV consistent (both allowed region)

MiniBooNE: New OscillaGon Results


è So, fit together with no cut (3+1). This gives the 3.6σpreference against the null hypothesis.

è Note: no muon disappearance in these fits!

Wait! Isn’t the peak supposed to be at L/E ~ 0.6??!

Excess: - Pizero background? - Pion Absorption? - M-particle correlation? - Oscillation? à MICROBOONE (470m)

L/E

Neutrino Velocity


OPERA anomaly is now resolved (two issues found)

CERN made a special beam structure to facilitate tests.

Now: (v-‐c)/c ≈ 10-‐6

MINOS: δt = -11.4 ± 11.2(stat) ± 29 (sys) ns [new hardware and analysis coming]

P Adamson (FNAL)/S. Bertolucci (CERN)/M. Dracos (Strasbourg)

Conclusion

sin22θ13 is now known to be non-‐zero! Accelerator experiments have measured an appearance signal. Values will get even more precise.

Now we can check the full consistency of our models using accelerators, atmospheric neutrinos and reactors. Some hints of inconsistency remain, so: let’s resolve those, keep working hard, and and try to measure CPV!


Review of Accelerator Neutrino Results · Review of Accelerator Neutrino Results CHRIS WALTER, DUKE...

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