s k atmospheric neutrino oscillations in sk-i an updated analysis alec habig, univ. of minnesota...

S K

Atmospheric Neutrino Oscillations in SK-I

An Updated Analysis

Alec Habig, Univ. of Minnesota Duluthfor the Super-Kamiokande Collaboration

With much help from Masaki Ishitsuka & Mark Messier

28th ICRC, 2 Aug. 2003 , Tsukuba

Alec Habig

S KUpdated Analysis

• All “SK-I” data (April 1996-July 2001) reanalyzed (1489 live-days)– Ring selection, Particle ID, multi-ring fits improved– Up- reduction automated and fitting improved (1646

live-days)

• Monte Carlo predictions improved– New 2001 Honda 3D flux (was Honda 1995)– Fermi Momentum, Axial Mass changed to better match

K2K near detector interaction data • (pF now flat, MA for QE, single from 1.01.1)

– New calibs. improve Outer Detector, H2O parameters in detector simulation (GEANT 3 based)


Alec Habig

S KFlux Changes

• Honda 1995 1D to Honda 2001 3D– Absolute

normalization lower– “3D” enhancement

• At low energies • Near the horizon

• But at low E, following angle is large– Smears out the peak

near horizon– So 3D-ness changes

little for Super-K (see next slide…)


Alec Habig Page 6

S K

Sub-GeV Data

Key: Data MC (no osc.) MC (best fit)

e-like -like

Sub-GeV

(<1.33 GeV)

3353 (Data)

3013.9 (MC)

3227 (Data)

4466.9 (MC)

MC

data

e) /(e) /(

0.0510.0160.649

Sub-GeV(stat.) (syst.)

(note no “3D” horizon peak)No cos() shape informationat the lowest energies, only flavor ratio is useful

At higher energies, directionalitybetter preserved plusshorter L no longer oscillate:cos() shape information very useful


Alec Habig Page 7

S KMulti-GeV data

MC

data

e) /(e) /(

083.00.699 0.0320.030

Multi GeV+PC(stat.) (syst.)

e-like -like

Multi-GeV

+ PC

746 (Data)

700.4 (MC)

1562 (Data)

2098.0 (MC)

At even higher energies, flux up/down symmetric and low-L do not have time to disappear.


baseline L: 12800 6200 700 40 15 km

Compare to Ae-like= -0.0200.0430.005 MC A-like= -0.0030.0050.009

Observed A-like 9.5 from no-oscillation prediction!

0.0040.0280.289NN

N-NA

likeμdownup

downup

(stat.) (syst.)


Alec Habig Page 8

S KMore Data


Data C

Sub-GeV

Multi-ring 208 346.4

Multi-GeV Multi-ring 439 739.4

Up through going

Up stopping

11213 srscm100.351.57

11213 srscm100.020.020.41

11213 srscm100.140.61

Measured flux:

Theoretical calc:

Measured flux:

Theoretical calc:

11213 srscm100.040.021.70 (stat.) (syst.)

(stat.) (syst.)

(theo.)

(theo.)

E ~10 GeV

E~100 GeV

• More , different E and systematics

+Nn

+Nn

SK

SK


Alec Habig Page 9

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New Oscillation Results

• For oscillation:

• Best fit: sin2(2)=1.0, m2=2.0x10-3 eV2

– 2 = 170.8/170 dof

• 90% c.l. region:– sin2(2)>0.9– 1.3 < m2 < 3.0x10-3

eV2

Contours representoscillation hypotheseswhich fit the observed dataless well with a 2 corresponding to:


Alec Habig Page 11

S K

Preliminary

Difference from Previous Results

• Small improvements + the same data: – but the end result

has changed by more than you might expect

• What happened?– (Note this figure

is highly zoomed)

New result@2x10-3

Old [email protected]

90% CLregions


Alec Habig Page 12

S K

Effects of Improvements on Fit

• Changes each of which caused m2 region to move slightly down:– flux change (Honda 19952001)

– interaction model (pF flat, MA 1.01.1)

– Improved detector simulation (OD, H2O calib.)

– Improved event reconstruction (Particle ID, ring selection, up- fitting)

• Net effect on 2 surface of several small changes in same direction is larger


Alec Habig Page 14

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Sub-Sample Consistency

Note open-ended“swoosh” shape of a one-parameterflavor ratio fit to two osc. parameters(lowest E eventsub-sample)

• Check oscillation fits using different classes of data independently – allowed regions all overlap best fit

• The low energy sub-sample’s only handle on oscillations is the /e flavor ratio– Used to be high (alone!), is now consistent with other sub-samples


Alec Habig Page 15

S KUnusual Models

• Ways to make disappear without , flavor oscillations include:– Lorentz inv. violation– decay, decoherence

• Fits using all available SK data strongly constrain many such models– Hard for model to get

good fit over 5 orders of mag. in E and 4 in L

– Long decay and decoherence disfavored but not eliminated

Mode Best Fit 2 P(2) 2

-

sin22sin2(1.27m2L/E)

sin22=1.00

m2=1.9x10-3 eV2

189 50% 0.0 0

-e

~sin22sin2(1.27m2L/E)

sin22=0.98

m2=4.2x10-3 eV2

304 0% 111 10.5

-s

~sin22sin2(1.27m2L/E)

sin22=0.93

m2=2.5x10-3 eV2

231 2% 42.2 6.5

LxE (L.I. violation)

sin22sin2(LxE)

sin22=0.89

=5.1x10-4 GeV/km

329 0% 103 10.1

decay (short )

sin4+cos4(1-e-L/E)

cos2=0.49

=3.2x10-3 GeV/km

287 0% 98.1 9.9

decay (long )

(sin2+cos2 e-L/2E)2

cos2=0.33

=9.8x10-3 GeV/km

207 19% 18 4.2

decoherence

0.5sin22(1-e-L/E)

sin22=0.98

=6.6x10-3 GeV/km

198 33% 9.4 3.1

Null Hypothesis 469 0% 280 16.7

(FC+PC (cut into 2 samples @Evis = 5 GeV)+NC+multiring+up-, 195 bins, 190 d.o.f.)

Data Used:(diff. from std.)


Alec Habig Page 16

S K to sterile?

• High energy experience matter effects which suppress oscillations to sterile – Matter effects not seen in

up- or high-energy PC data– Reduction in neutral current

interactions also not seen

– constrains s component of disappearance oscillations

• Pure s disfavored

– s fraction < 20% at 90% c.l.


Alec Habig Page 17

S KCPT Violation

• Do oscillate differently than ?

• SK cannot tell the difference between and event-by-event– But we see the sum of the two– One behaving very differently

would show up in the total


Alec Habig Page 20

S KSummary

• oscillations fit the data better than other means of making disappear – Best fit value is (m2 = 2.0x10-3 eV2, sin2(2) = 1.0)– 1.3 < m2 < 3.0x10-3 eV2, sin2(2) > 0.9 @ 90% c.l.

• Analysis improvements to– interaction & flux models– Detector simulation– Event reconstruction

• No one improvement drove the changes to the final fit– Each contributed a little in the same direction– All data sub-samples now individually consistent with the

overall fitThe presenter gratefully acknowledges support for this presentation from the National Science Foundation via its RUI grant #0098579, and from The Research Corporation’s Cottrell College Science Award

s k atmospheric neutrino oscillations in sk-i an updated analysis alec habig, univ. of minnesota...

Documents

slide slide

tsukuba alec habig page

data slide

updated analysis alec

flux changes honda

d flux

flux change honda

left slide