Atmospheric Results fromSuper-Kamiokande

Roger Wendell, ICRR
For the Super-Kamiokande Collaboration
2014.06.04
NEUTRINO2014, Boston

Introduction
 Some Introductory Material Atmospheric neutrinos as signal◾ Search for  AppearanceStandard MNS Oscillation Analysis
2◾ Search for m ~ eV scale sterile neutrinoss◾

◾

Search for Lorentz invariance violation

 Atmospheric neutrinos as background◾
Search for WIMP-induced neutrinos from the galactic center◾
Search for WIMP-induced neutrinos from the sun Summary23Atmospheric Neutrinos As Signal4Atmospheric Neutrino Generation
 Cosmic rays strike air nuclei and the decay of theout-going hadrons gives neutrinos

P + A → N + π+ + xµ+ + νµ → e+ + νe + νµPrimary cosmic rays Isotropic about Earth●s travel 10 – 10,000 km before detection● Both neutrinos and antineutrinos in theflux● ~ 30% of final analysis samples areantineutrinos●●Flux spans many decades in energy ~100
MeV – 100TeV+

Excellent tool for broad studies ofneutrino oscillations● Access to sub-leading effects with highstatisticsR.Wendell (ICRR)
4●

5Atmospheric Neutrino Generation
 Cosmic rays strike air nuclei and the decay of theout-going hadrons gives neutrinos

Super-KPreliminary

P + A → N + π+ + xµ+ + νµ → e+ + νe + νµPrimary cosmic rays Isotropic about Earth● s travel 10 – 10,000 km before detection● Both neutrinos and antineutrinos in theflux● ~ 30% of final analysis samples areantineutrinos●●Flux spans many decades in energy ~100
MeV – 100TeV+Excellent tool for broad studies ofneutrino oscillations● Access to sub-leading effects with highAtmospheric neutrino Flux measurement
statistics
By Super-K
R.Wendell (ICRR)
5●Poster #249, K.Okumura

Super-Kamiokande: Introduction

6 22.5 kton fiducial volume
 Optically separated into
◾ Inner Detector 11,146 20” PMTs◾
Outer Detector 1885 8” PMTs
 No net electric or magnetic fields
 Excellent PID between showering (e-like)and non-showering (m-like)◾ < 1% MIS ID at 1 GeV
 Today: 4581 days of atmospheric
neutrino data◾ 40,000 Events◾ Statistics limitedFour Run Periods:
SK-I (1996-2001) SK-II (2003-2005)
SK-III (2005-2008) SK-IV (2008-Present)
Dinucleon Decay Search
Poster#157 J. Gustafson
Trilepton Decay Search
Poster #216, V.Takhistov

 Multipurpose machine◾ Solar and Supernova Neutrinos◾ Atmospheric Neutrinos (this talk)◾ Nucleon Decay◾ Far detector for T2K

Neutron Tagging

PreliminaryCompare:204.8 sGeant3

Phys Rev. C
15 (1977) 1636

t0 =  interaction time Upgraded detector electronics in SK-IV store all PMT hits in a500 sec window after a physics trigger◾
Search for the 2.2 MeV gamma from p(n,)d Search is performed using a neural network built from 16variables◾
Data and MC show good agreement on atmospheric
neutrino sample
 Future: Implement neutron tagging to help distinguish /interactions and to reduce proton decay backgrounds

2.2 MeV  Selection
Efficiency

20.5%

Background / Event0.018

7Super-K Atmospheric  Event Topologies
Fully Contained (FC)Partially Contained (PC)

Upward-going Muons (Up-) Average energies◾
FC: ~1 GeV , PC: ~10 GeV, UpMu:~ 100 GeV

8Super-K Atmospheric  Analysis Samples
Fully Contained (FC)Partially Contained (PC)

Upward-going Muons (Up-) In total 19 analysis samples: multi-GeV e-like samples are
divided into -like and -like subsamples
 Dominated by -> oscillations
 Interested in subdominant contributions to this picture◾ Ie three-flavor effects, Sterile Neutrinos, LIV, etc.

9

Evidence for  Appearance at Super-K

10

 Search for events consistent with hadronic
decays of  leptons◾ Multi-ring e-like events, mostly DIS interactions
 Negligible primary  flux so  must beoscillation-induced : upward-going Event selection performed by neural network◾ Total efficiency of 60%

= 0 : no 

SK-I+II+III : 2806 days
Phys. Rev. Lett. 110, 181802 (2013)

Fitted ExcessAtm ν BKG MCResult
SK-I+II+III

Background0.94 ± 0.02

SignalDIS ()1.10 ± 0.05 1.42 ± 0.35

This corresponds to180.1 44.3 (stat) +17.8-15.2 (sys) events, a
3.8 σ excess (Expected 2.7  significance )Searching for Three-Flavor Effects: Oscillation probabilities~100 kmP(νµ→νµ )~10,000 km

 Key Points◾ No    Appearance above ~20 GeV,
eP(νµ→νe)“Sub-GeV”“Multi-GeV”

Resonant oscillations between 2-10 GeV (for  or  depending upon MH)◾ No oscillations above 200 GeV◾
No oscillations from downward-going neutrinos above ~5 GeV◾ Expect effects in most analysis samples, largest in upward-going e◾

11

12Oscillation Effects on Analysis Subsamples~100 km cp = 3/2P(νµ→νµ )sin2223 = 0.6
sin223 = 0.5
sin 23 = 0.4~10,000 km

 cp = /2“Sub-GeV”“Multi-GeV”

Ratio to two-flavor
oscillations
Appearance effects
are halved in the IH

sin  = 0.6
sin  = 0.5
sin  = 0.4
22 23
2 2323sin2223 = 0.6
sin223 = 0.5
sin 23 = 0.4

Expected Sensitivity
 As a result, the sensitivity to themass hierarchy is a rather strong
function of the other oscillation
parameters As a function of the true value ofsin223 this plot shows the ability
to reject the inverted mass
hierarchy hypothesis assuming
the normal hierarchy

13Hierarchy Sensitivity NH True

14

Changes and Updates to Oscillation Analyses

Prediction  Osc.
New Sample

/ Separated Samples

 Addition of a new analysis sample
 Multi-Ring e-like Inclusive (Fully Contained)◾
Events that fail the multi-ring e-like selection
 Improved systematic error treatments◾
Updates to cross-section, FSI, detector
systematics, 2p-2h (MEC) uncertainties
 1775 days of SK-IV data: 4581.4 days total◾
(282.2 kton yrs)

Multi-Ring e-like Sample Purities
PurityCC eCCCCNC

-like

72.2%

8.3%

3.2%

16.1%

-likeother75.0%

6.5%

2.8%

15.6%

30.9% 33.4%

5.1%

30.5%

13 Fixed Analysis (NH+IH) SK OnlyPreliminary

15SK Inverted Hierarchy
SK Normal Hierarchy

Fit (517 dof)

2

θ13

cp

23

m23 (x10-3)

SK (NH)

559.8

0.025

3.84

0.57

2.6

SK (IH)

560.7

0.025

3.84

0.57

2.5

 13 fixed to PDG average, but its uncertainty is included as a systematic error Offset in these curves shows the difference in the hierarchies

About These Results Normal hierarchy favored at:22◾ –= -0.9IHNHPreliminary
SK Inverted
SK Normal

Not a significant preference◾ Previous results (2013 Summer) favored
inverted hierarchy by 2 ~ 1.5◾

 Driven by excess of upward-going e-likeevents consistent with the effects of 13
Primarily in SK-IV data◾
New multi-ring e-like sample also pulls thefit towards the NH● Fit for  now weakly favors 01313◾

 Rejection of cp ~ 60º driven by excess inSubGeV electron events◾ Constraint is consistent with sensitivity

InvertedNormal

16PDG2013

Comparison with Official Results from T2K and MINOS

17

PreliminarySuper-K Atm. T2K  Run1-4
MINOS Beam+ Atm 3f

Normal Hierarchy

Inverted Hierarchy Though consistent with long-baseline measurements, atmosphericneutrinos allow more of the mixing parameter space SK's sensitivity can be improved by incorporating constraints from thesemeasurements

Introduction of External Constraint Restricting the allowed values of m2 andsin223 available to the atmospheric neutrino

18

Hierarchy Sensitivity NH Truefit can help improve sensitivity to the masshierarchy◾
Include these constraints as external datasets in the SK fit

SK + T2K ,  eSK Alone Fit the T2K  and e data sets with SK◾
Same detector, generator and reconstruction:systematic error correlations incorporatedeasily◾
Fit is based on publicly available T2K
information and results◾
Simulate T2K using SK tools◾
(not a joint result of the T2K and SKcollaborations )T2K
External Constraint MINOS constraint is similarly important but
harder to model accurately (so far...)

Theta13 Fixed SK + T2K e (External Constraint) NH19Preliminary

SK Atm
SK+T2K ,e Constraint
T2K ,e Constraint

Fit (543 dof)

2θ13cp23m23 (x10-3)

SK + T2K (NH)

578.2

0.025

4.190.55

2.5

SK + T2K (IH)

579.4

0.025

4.19

0.55

2.5

 2IH – 2NH = -1.2 (-0.9 SK only ) CP Conservation (sincp = 0 ) allowed at (at least) 90% C.L. for both hierarchies

Sterile Neutrino Oscillations in Atmospheric Neutrinos
MNS20Sterile

 Sterile Neutrino searches at SK are
independent of the sterile m2 and thenumber sterile neutrinos◾
3+1 and 3+N models have the same
signatures in atmospheric neutrinos
22◾ For m ~ 1 eV oscillations appear fast:s< sin2 m2 L/E > ~ 0.5

 | U4 |2◾ Induces a decrease in event rate of like data of all energies and zenith
angles | U4 |2◾

Shape distortion of angular distributionof higher energy -like data|U4|2 at 5 sensitivity|U4|2 at 5 sensitivity

21

Hydrogen Earth Approximation
Preliminary Turning off sterile matter effects
while preserving standard threeflavor oscillations provides a puremeasurement of | U4 |2CCFR
PRL. 52,1384 (1984)

 Using SK-I+II+III+IV data ( 4438 days)| U4 |2 < 0.022 at 90% C.L.

MINOSPreliminary Limit is valid for m41 > 0.01 eV2◾
For smaller values, the assumptionof fast oscillations is invalid"Searches for Exotic Oscillationsin Atmospheric Neutrinos."
Poster #212, A. Himmel

Search for MeV Sterile Poster #181, E. RichardSK

MiniBooNE +SciBooNE
PRD86,052009 (2012)

22Tests of Lorentz Invariance(aeT)P(νµ→νµ ) Lorentz invariance violating effects can be probed
using atmopsheric neutrinos◾ Focus here on isotropic effects◾ (sensitive to sidereal effects as well...) Analysis using the Standard Model Extension (SME)◾ Not a perturbative calculation◾ Effects computed using full solutions of theHamiltonian Effects of LIV controlled by two sets of complex
parametersT◾ adim = 3 induces oscillation effects ~ L◾

cTT dim = 4 induces oscillation effects ~ L E

(aT) = 10-22
(C TT) = 10-22

Constraints on Lorentz Invariance Violating Oscillations: 90% C.L.

23

Preliminary SK-I+II+III+IV : 4438 days of data Perform separate fits on both hierarchy assumptions for each coefficient and eachsector : e , e,  No indication of Lorentz invariance violation◾
Limits placed on the real and imaginary parts of 6 parameters  O(10-23)

24

Lorentz Invariance Violating Oscillation Limits : 90% C.L.
Preliminary

 Established new limits in the  sector for both aTand cTT coefficents
 Improvements on existing limits between 3 and 7 orders of magnitude!

25Atmospheric Neutrinos As BackgroundSearch for WIMP Annihilations in the Galactic Center and Sun
 Search for a signal of WIMP
annihilation from the Galactic Halo orsolar interior assuming several
branching modes◾
, bb, tt, W+W Signal would appear atop the ATM 
background, peaked towards either
the galactic center or towards the sun(Or Sun)

 Simulate signal and detector response for all flavors
 Same analysis samples as oscillation analyses,
but binned in angle to the galactic center◾ Use all samples◾ Previous analyses used only Up  sample◾ Allows probe of both low O(GeV) and highO(TeV) WIMP masses

Signal Norm Arbitrary
ATM BG MC26

Search for WIMP Annihilations : Signal Demonstration
O(100) MeV

 bbM( = 105 GeV / c2
WIMP Signal, Best Fit  15
ATM  Background + WIMP Analysis uses all available
data◾
Previous analyses used only
the upward-going muons
 100% branching fraction
assumed for each tested
annihilation channel

O(10)–O(100+) GeV

cos ( GC)

 Equal fluxes at detection◾ (  ) = (  ) = (  )e27

Search for WIMP Annihilations : Signal Demonstration
O(100) MeV

 bb
M( = 100 GeV / c2
WIMP Signal, Best Fit  15
ATM  Background + WIMP Analysis uses all availabledata◾
Previous analyses used only
the upward-going muons
 100% branching fraction
assumed for each tested
annihilation channel

O(10)–O(100+) GeVcos ( GC)

 Equal fluxes at detection◾ (  ) = (  ) = (  )e

28Search for WIMP Annihilations in the Galactic Center: ResultsPreliminaryIcecubebb
 + bb + -W+ W-


W+ W-


Natural Scale – DM as a thermal relic No evidence for event excess on top of the atmospheric neutrino background◾
N.B. ~300 events allowed at 5 GeV test point are distributed over several
analysis bins
 Stringent limits placed on the velocity-averaged annihilation cross section
down to WIMP masses of 1 GeV ( )

29

30

Search for WIMP Annihilations in the Sun
XENON10CoGENT*Solar composition, VDF,
Nuclear form factor

Preliminary*DAMA/LIBRA

DAMA/LIBRAICECUBE bb

PICASSO

CDMSlite

BAKSAN bb

SIMPLECRESSTIIBAKSAN + -ICECUBE
W+W-BAKSAN
W+W-CDMS II Si

LUXXENON100

 Similar analysis can be performed when looking
towards the center of the Sun
 No indication of an event excess in the data Spin-dependent cross section limits well below theallowed regions for DAMA/LIBRA
 Spin-independent limits in tension with some allowedregions, but not as constraining as LUX or XENON100

SuperCDMS

M = 10 GeVBest fit signal x 10
ATM BG MC

31Summary  appearance seen at 3.8 significance Three-Flavor Analysis◾ Using 4538 days of data, there is a ~1  preference for the NH, andsecond octant
 No indication of oscillations into sterile states
2◾ For 3+N models | U|
< 0.022 at 90% C.L.
4
 No indication of Lorentz invariance violation◾ Limits set or improved by 3 to 7 orders of magnitude
 So far no indication of indirect dark matter annihilation into
neutrinos from either the sun or galactic center Several posters for these and other SK analyses in the poster session
Thank you32

Supplements

33

Three-Flavor

Theta13 Fixed SK + T2K e (External, Inverted Hierarchy)

Preliminary

SK Atm
SK+T2K ,e Model
T2K ,e Model

Fit (543 dof)

2

θ13cp23m23 (x10-3)

SK + T2K (NH)

578.2

0.025

4.190.55

2.5

SK + T2K (IH)

579.4

0.025

4.190.55

2.5

 2IH – 2NH = -1.2 (-0.9 SK only ) CP Conservation (sincp = 0 ) allowed at at least 90% C.L. for both hierarchies3413 Free Analysis (NH+IH) SK Only

Preliminary35

SK Inverted Hierarchy
SK Normal Hierarchy

Fit (517 dof)

2θ13cp

23

m23 (x10-3)

SK (NH)

559.2

0.010

3.84

0.57

2.6

SK (IH)

560.4

0.015

3.84

0.57

2.5

 Offset in these curves shows the difference in the hierarchies13 Free Analysis (NH+IH) SK Only

Preliminary

36

SK Inverted Hierarchy
SK Normal Hierarchy

Fit (517 dof)

2

θ13

cp

23

m23 (x10-3)

SK (NH)

559.2

0.010

3.84

0.57

2.6

SK (IH)

560.4

0.015

3.84

0.57

2.5

 Offset in these curves shows the difference in the hierarchies