Aspen 2002

J. Goodman - Aspen - Feb 2002

Aspen 2002

Recent Results from Super-K (and K2K)

Neutrino Oscillations &

Mechanical Chain Reactions

Jordan GoodmanUniversity of Maryland


Super-Kamiokande


Detecting neutrinos

Electron or

muon track

Electron or

muon track

Cherenkov ring on the

wall

Cherenkov ring on the

wall

The pattern tells us the energy and type of particle

We can easily tell muons from electrons

The pattern tells us the energy and type of particle

We can easily tell muons from electrons


A muon going through the detector


Stopping Muon


Stopping Muon – Decay Electron


Neutrino Production

Ratio predicted to ~ 5%

Absolute Flux Predicted to ~20% :

2

ee


Atmospheric Oscillations

about 13,000 km

about 15

km

Neutrinos produced in

the atmosphere

Neutrinos produced in

the atmosphere

We look for transformations

by looking at s with different distances from production

SK


Atmospheric Neutrino Interactions

n p

W+

Reaction Thresholds

Electron: ~1.5 MeV

Muon: ~110 MeV

Tau: ~3500 MeV

Charged Current Neutral Current

e e

n p

W +


Telling particles apart

MuonElectronMuonElectron


Muon - Electron Identification

PID Likelihood

sub-GeV, Multi-GeV, 1-ring

Monte Carlo (no oscillations)

We expect

about twice as

many as e


Super-K Atmospheric Data Set

• 1289.4 days of data (22.5 kilotons fiducial volume)• Data Set is divided into:

– Single and Multi Ring events– Electron-like and Muon-like– Energy Intervals

• 1.4 GeV< Evis >1.4 GeV• Also Evis< 400MeV (little or no pointing)

– Fully or partially contained muons (PC)– Upward going muons - stopping or through going

• Data is compared to Atmospheric Monte Carlo– Angle (path length through earth)– Visible energy of the Lepton


Low Energy Sample

No Oscillations

Oscillations (1.0, 2.4x10-3eV2)


Moderate Energy Sample


Multi-GeV Sample

Oscillations (1.0, 2.4x10-3eV2)

No Oscillations

UP going Down UP Down


Multi-Ring Events


Upward Going Muons


Summary of Atmospheric Results

Best Fit for to

Sin22 =1.0,

M2=2.4 x 10-3eV2

2min=132.4/137 d.o.f.

No Oscillations

2min=316/135 d.o.f.

99% C.L.

90% C.L.

68% C.L.

Best Fit

Compelling evidence for to atmospheric neutrino oscillations


Tau vs Sterile Neutrino Analysis


Tau Appearance?

• Tau’s require greater than 3 GeV in neutrino energy– This eliminates most events

• Three correlated methods were used– All look for enhanced upward going multi-ring events

• All show slight evidence for Tau appearance• None are statistically significant


The 0 sample

• For to s the rate of NC events is reduced as

compared to to which is the same as no

oscillations.• The SK NC enriched sample is only about 1/3

from NC interactions.

• The 0 sample is the cleanest NC signal

• Until now the error in (0) (~1-2 Gev) has been as large as the effect!


Original SK Systematic Errors

• Systematic Error in r0=(0/Q.E.)

– Cross section – 20%

– Reconstruction – 7%

– Nuclear Interaction – 7%

– Flux – 3%

– Total Systematic – 23%


Original Results from 0s


K2K Near Detector

K2K beam is:

~1.3 GeV

98.2%

1.3% e

0.5%


0 Peaks


Monte Carlo of 0 Production


Use K2K to measure the Cross Section

• A normalized 0 rate is defined as r0=(0/fc)

• Form double ratio of R0= r0(data)/r0(MC) to

minimize flux uncertainties and nuclear effects• Simulate both K2K and SK flux and efficiencies

• K2K finds R0 = 1.04 ± 0.02 ± 0.02 ± 0.09

Stat (data MC) Sys

• Old SK R0 = 1.05 ± 0.05 ± 0.01 ± 0.23

• Use K2K measurement to improve SK result


New Systematic Errors in SK

• Using K2K Result

– Reconstruction – 7%

– Flux – 3%

– Spectral Diff between SK and K2K – 5%

– Cross section/Nuclear effects – 12%

(flux averaged)

– Total Systematic – 14%


New Results


Combined


Super-K Disaster - Nov 12, 2001

• Chain reaction destroyed 7000 OD and 1000 ID Tubes

• The cause is not completely understood, but it started with a lower pmt collapse.

• The energy release comes from a 4 T column of water falling

• There are plans to rebuild…


Disaster (Continued)

Aspen 2002

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