Takaaki kajita icrr univ of tokyo
Download
1 / 41

Takaaki Kajita, ICRR, Univ. of Tokyo - PowerPoint PPT Presentation


  • 159 Views
  • Uploaded on

NuFact04, Osaka, July 2004. Atmospheric Neutrinos; - Present and future -. Takaaki Kajita, ICRR, Univ. of Tokyo. Outline. Atmospheric neutrino beam Atmospheric neutrinos: Present L/E analysis Atmospheric neutrinos: Future sub-dominant oscillations ?

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' Takaaki Kajita, ICRR, Univ. of Tokyo' - fran


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Takaaki kajita icrr univ of tokyo

NuFact04, Osaka, July 2004

Atmospheric Neutrinos;

- Present and future -

Takaaki Kajita, ICRR, Univ. of Tokyo


Outline
Outline 2004

  • Atmospheric neutrino beam

  • Atmospheric neutrinos: Present

    L/E analysis

  • Atmospheric neutrinos: Future

    sub-dominant oscillations ?

  • Summary

Only 2 and 3 flavor neutrino oscillations


Atmospheric neutrinos

Cosmic Ray 2004

Atmospheric neutrinos

p, K

Atmosphere

μ

e

nm

nm

ne

nm

ne

Neutrinos from the other side of the Earth.


Atmospheric neutrino beam

Total 2004nm+nm flux

Flux × En2

En(GeV)

Atmospheric neutrino beam

Measured cosmic ray proton flux

Zenith angle:

nm

ne


Event classification
Event classification 2004

Fully Contained (FC) (E ~1GeV)

Partially Contained (PC) (E ~10GeV)

Stopping  (E~10GeV)

Through-going (E~100GeV)


Atmospheric neutrinos: Present 2004

Soudan-2 (1kton tracking detector)

9.3m

76m

Super-Kamiokande (50,000ton water Ch. Detector)

MACRO (large muon detector)

12m


Super k atmospheric neutrino data
Super-K atmospheric neutrino data 2004

CC ne

CC nm

1489day FC+PC data + 1646day upward going muon data


Soudan2
Soudan2 2004

  • 5.9 kton・yr exposure

  • Partially contained events included.

  • L/E analysis with the “high resolution” sample

Reconstructed Lν/ Eν dist.

Zenith angle

Phys.Rev. D68 (2003) 113004

e

e

μ

μ

Up-going

Down-going

No osc.

nm ntosc.


Macro

Multiple scattering 2004

Em

En

or

MACRO

PLB 566 (2003) 35

Oscillation

Δm2 =2.5×10-3

L /E

Upward

horizontal


Neutrino oscillation parameters
Neutrino oscillation parameters 2004

nm nt

90%CL

Soudan-2

Super-K

MACRO


m 2004-like multi-GeV + PC

SK collab. hep-ex/0404034

L/E analysis

New !

oscillation

decoherence

decay

Should observe this dip!

  • Further evidence for oscillations

  • Strong constraint on oscillation

    parameters, especially Dm2


Selection criteria

FC single-ring 2004m-like

Full oscillation

1/2 oscillation

D(L/E)=70%

Selection criteria

Select events with high L/E resolution

(D(L/E) < 70%)

Following events are not used:

★horizontally going events

★low energy events

2121 FC m-like and

605 PC

Similar cut for: FC multi-ring m-like,

OD stopping PC, and

OD through-going PC


L e distribution

1489 days FC+PC (Super-K) 2004

L/E distribution

Mostly up-going

MC (no osc.)

Decoh.

Decay

Osc.

Mostly down-going

  • Evidence for oscillatory signature

Decay and decoherence disfavored at 3.4 and 3.8s level, respectively.


Allowed neutrino oscillation parameters
Allowed neutrino oscillation parameters 2004

90% CL

1.9x10-3 < Dm232 < 3.0x10-3 eV2

0.90 < sin22q23(90% C.L.)

SK L/E analysis

Kam.

c2min=37.9/40 d.o.f

@ Dm2=2.4x10-3,sin22q=1.00

(sin22q=1.02, c2min=37.8/40 d.o.f)

Soudan2

K2K

MACRO

SK Zenith angle analysis

 Stronger constraint on Dm2

 Consistent with that of the standard zenith angle analysis


Search for non zero q 13

Matter effect 2004

cosQ

En(GeV)

Search for non-zero q13

(Dm122=0 assumed)

MC, SK 20yrs

1+multi-ring, e-like, 2.5 - 5 GeV

Electron appearance

s213=0.05

s213=0.00

null oscillation

cosQ

Electron appearance in the 5 – 10GeV upward going events.


Super k e like data
Super-K e-like data 2004

Multi-GeV, single-ring e-like

Multi-GeV, multi-ring e-like

(special)

No evidence for excess of upward-going e-like events


3 flavor analysis from super k

prelim. 2004

n2

n3

n1

n2

n3

n1

3 flavor analysis from Super-K

Normal

Inverted


Atmospheric neutrinos: Future 2004

Present: Study of dominant oscillation channel (nm nt)

Future: Study of sub-dominant oscillations

★q13?

★Mass hierarchy?

★Solar oscillation effects?

nenmnt

Normal mass hierarchy is assumed.

n3

ν mass

n2

n1


Possible future atmospheric n detectors
Possible future atmospheric 2004n detectors

Very large water Cherenkov detector

UNO

Hyper-K (1Mton)

Mton class detector at Frejus

Magnetized large tracking detector

MONOLITH,

INO (India-based Neutrino Observatory, …


Sensitivity to non zero q 13

Importance of s 20042q23>0.5; S.Pascoli et al., hep-ph/0305152

TK noon2004

Sensitivity to non-zero q13

Multi-GeV electron appearance

SK 20yr MC

Water Cherenkov detector 450 kton・yr (SK 20 years)

3s

3s

3s

~ Present bound on sin2q13

(Dc2 ∝~ exposure)


How can we discriminate positive and negative d m 2

P( 2004nmne)

n2

n3

n1

n2

n3

n1

cosQ

En(GeV)

Sign of Dm23(13)2 ?

How can we discriminate positive and negative Dm2 ?

Real Dm232 =positive assumed

Real Dm232 = negative assumed

P(nmne)

cosQ

En(GeV)

(No resonance for anti-neutrinos)

(No resonance for neutrinos)


Measurement of sign of d m 2 in large magnetized detectors
Measurement of sign of 2004Dm2 in large magnetized detectors

Δm2=2.5×10-3 sin2θ =0.02

13

Determination of sign of Δm2 at 90%CL.

NPB (proc suppl) 91 (2001) 147, hep-ex/0106252


Measurement of sign of d m 2 in water cherenkov detectors

TK NOON2004 2004

Measurement of sign of Dm2in water Cherenkov detectors ?

Use differences in s and ds/dy

Dm2: fixed, q23: free, q13: free, positive Dm2

Exposure: 1.8Mtonyr (SK 80yr or HK ~3.3 yr)

3s

3s

3s


Solar oscillation effects
Solar oscillation effects 2004

Solar neutrino oscillation: LMA (Dm122 = 7×10-5eV2)

Expected number of sub-GeV e-like events in SK.

Peres, Smirnov NPB 680 (2004) 479

10

1

The number of e-like events changes as a function of sin2q23 (NOT sin22q23).

 Discrimination of >45 and <45 q23 might be possible. (However, the effect is very small for s22q23=1.00.)

P.Lipari NOON2004


Summary 2004

  • Atmospheric neutrinos have been playing major role in the neutrino oscillation studies.

  • The present data are nicely explained by nm nt oscillations with;

    Dm2=1.9 – 3.0 × 10-3 eV2

    sin22q > 0.90 (SK L/E analysis)

  • Recent L/E analysis has shown evidence for “oscillatory” signature.

  • Future atmospheric neutrino experiments is likely to continue to contribute to the neutrino oscillation physics (q13, sign of Dm232 ….)

    (If (a) much larger detector, (b) relatively large q13.)


End 2004


Specials in l e analysis
Specials in L/E analysis 2004

1.5m from top & bottom

FC single-ring, multi-ring m-like

22.5kt

→26.4kt

Expand fiducial volume

1m from barrel

More statistics for high energy muons

observed charge / expectation from through-going

PC

OD through-going

OD stopping

Classify PC events using OD charge

OD through-going MC

  • OD stopping

  • OD through going

Different L/E resolution

OD stopping MC



L e cuts

m 2004

m

L/E cuts

Full osc.

Half osc.


Sensitivity to other models determination of l e resolution cut
Sensitivity to other models (determination of L/E resolution cut)

70%

80%

n decoherence

n decay

n decay

n decay

70%

80%

n decoherence

n decoherence

L/E resolution cut at 70%


Event summary of l e analysis
Event summary of L/E analysis resolution cut)

Fractions of FC and PC samples in L/E distribution

FC

Data MC CC nm

single-ring

multi-ring

stopping

through-going

1619 2105.8 (98.3%)

502 813.0 (94.2%)

114 137.0 (95.4%)

491 670.4 (99.1%)

PC


Check of the observed dip in l e distribution 1
Check of the observed dip in L/E distribution (1) resolution cut)

Other L/E resolution cuts


Check of the observed dip in l e distribution 2
Check of the observed dip in L/E distribution (2) resolution cut)

FC e-like

(Flat L/E distribution is expected.)


Check of the observed dip in l e distribution 3
Check of the observed dip in L/E distribution (3) resolution cut)

zenith angle :cosq  -cosq

(Zenith angle of each event is inverted. Because of the wrong assignment of L, no dip is expected.)


Sensitivities to alternative models and the data
Sensitivities to alternative models and the data resolution cut)

n decoherence

obtained Dc2

n decay

L/E resolution cut at 70%


Neutrino decay and decoherence models
Neutrino decay and decoherence models ? resolution cut)

c2min=37.9/40 d.o.f

c2min=49.1/40 d.o.f  Dc2 =11.3

c2min=52.4/40 d.o.f  Dc2 =14.5

Oscillation

Decay

Decoherence

ndecay disfavored at3.4s

ndecoherence at3.8s

First dip observed in the data cannot be explained by alternative hypotheses

 Evidence for oscillatory signature


C 2 as a function of sin 2 q 13
c resolution cut)2 as a function of sin2q13

Inverted

Normal


How can we discriminate neutrino and anti neutrino interactions

CC resolution cut)ne

CC ne

How can we discriminate neutrino and anti-neutrino interactions ?

Simple answer: No. It is not possible to discriminate event by event in water Cherenkov experiments.

However, s(total) and ds/dy are different.

Single-ring e-like

Multi-ring e-like

Others

Others

CC ne

CC ne

 Try to discriminate positive and negative Dm2 using these events.


Electron appearance for positive and negative d m 2 in a water chrenkov detector
Electron appearance for positive and negative resolution cut)Dm2 in a water Chrenkov detector

Dm2=0.002eV2

s2q23 = 0.5

s2q13 = 0.05

(SK 20yrs)

Single-ring e-like

Multi-ring e-like

Relatively high anti-ne fraction

Lower anti-ne fraction

Positive Dm2

Negative Dm2

null oscillation

cosQ

cosQ


C 2 difference inverted normal
c resolution cut)2 difference (inverted-normal)

True= normal mass hierarchy assumed.

Dm2: fixed, q23: free, q13: free

Exposure: 1.8Mtonyr (SK 80yr or HK ~3.3 yr)

3s

3s

3s


C 2 difference normal inverted
c resolution cut)2 difference (normal – inverted)

True= inverted mass hierarchy assumed.

Dm2: fixed, q23: free, q13: free

Exposure: 1.8Mtonyr (SK 80yr or HK ~3.3 yr)

3s

3s

3s


ad