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Search for exotic contributions to Atmospheric Neutrino Oscillations. G. Giacomelli, V. Popa, M. Sioli University of Bologna and INFN Venezia, 22-25/2/2005, “ Neutrino Telescopes ”. - Introduction - Monte Carlos - Final oscillation analyses - Search for LIV contributions

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Search for exotic contributions to Atmospheric Neutrino Oscillations

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Search for exotic contributions to atmospheric neutrino oscillations

Search for exotic contributions to AtmosphericNeutrino Oscillations

G. Giacomelli, V. Popa, M. Sioli

University of Bologna and INFN

Venezia, 22-25/2/2005, “NeutrinoTelescopes”

- Introduction

- Monte Carlos

- Final oscillation analyses

- Search for LIV contributions

- Conclusions


Search for exotic contributions to atmospheric neutrino oscillations

Upthroughgoing

In up

Absorber

Streamer

Scintillator

In down

Upstop

1)

4)

3)

2)

MACRO

DATA SAMPLES(measured)

(Bartol96 expected)

__________________________

Upthrough(1) 857

1169

In up(2) 157

285In down(3)+

Up stop(4) 262

375


Search for exotic contributions to atmospheric neutrino oscillations

Atmospheric n flux. Monte Carlos

- Until 2001 Bartol96 (Honda96)

- After 2001FLUKA2001-3 (Honda2001-3)

Both 3-dimensional

improved interaction models

new cosmic ray fit, .....

They agree to ~5%

But: Predictions of new Honda and FLUKA MCs

H.E. 25% low ; L.E. 12% low

- Angular distributions of Bartol96, new Honda and FLUKA MCs agree to ~<6%

New L3cosmic data favor Bartol96, …

astro-ph0502380


Search for exotic contributions to atmospheric neutrino oscillations

MACRO data

MonteCarlos

Upthroughgoing

n1


Search for exotic contributions to atmospheric neutrino oscillations

En = 13 GeV

En = 36 GeV

MC predictions for

nm nt oscillations

with the MACRO

parameters

En = 88 GeV

En =146 GeV

nm energy estimate through Multiple Coulomb Scattering of upthroughgoing muons in rock in lower MACRO(Phys. Lett. B566 (2003) 35)

300 events with

θ<60 degrees

No oscillation Bartol96


L e n distribution

MC predictions for nm nt

oscillations with the best

MACRO parameters

L/En distribution

From the muon zenith distribution

From the measurement

of the muon energy using

Multiple Coulomb

Scattering

Upthr. m data

IU m data

12% point-to-point syst. error


Final oscillation analyses

Best fit parameters for nm nt

Dm2 = 2.3 10-3 eV2 ; sin2 2q =1

Eur. Phys. J. C36(2004)357

Final oscillation analyses

Use ratios with uncertainties of ~5%, independent of MCs

{

Zenithdistribution

R1= N(cos Q < -0.7) /N(cosQ > -0.4)

H.E.

R2= N(low En) / N(high En)

En estimate

IU, ID and UGS m

R3= N(ID+UGS) / N(IU)

L.E.

No oscillation hypothesis

ruled out by ~ 5 s

Absolute values referred to Bartol96 MC :

R4=(Data/MC)H.E. ; R5=(Data/MC)L.E.

With these informations, the no oscillation hypothesis is ruled out by ~ 6 s


Search for exotic contributions to atmospheric neutrino oscillations

MACRO

D

q


Search for exotic contributions to atmospheric neutrino oscillations

Mass induced oscillations

2 n flavor interpretation:

induced by the mixing

of 2 mass eigenstates

,

and 2 weak eigenstates

,

:

The survival probability is


Search for exotic contributions to atmospheric neutrino oscillations

Exotic oscillations

Lorentz invariance violation (LIV)

For LIV oscillations: there is mixing between 2 flavor eigenstates and 2 velocity eigenstates: (asymptotic vn different from c)

The survival probability is: ( v=v3-v2 )

Notice the dependence LEn  LIV is not dominant

Violation of the equivalence principle

Similar results as for LIV, but with parameter fD

(fD= difference of coupling constants of n to gravitational pot f)


Search for exotic contributions to atmospheric neutrino oscillations

Mixed oscillations

If both mass-induced and LIV-induced transitions are considered simultaneously:

where

and


Search for exotic contributions to atmospheric neutrino oscillations

P(nmnt)

Mixed

oscillations


Search for exotic contributions to atmospheric neutrino oscillations

2 analysis

We computed upper limits of LIV parameters v , sin2 2θv -using the formalism of

Coleman-Glashow PL B405(1997)249; hep-ph/0407087 ,

-taking the Nlow, Nhigh samples of low and high energy muon

upthroughgoing data with cuts

- as for MACRO mass oscillation analysis

- optimized for LIV search

-fixing Dm2=0.0023 eV2 and maximal mixing (MACRO values)

-minimize with respect to Dv, θv the function

90% C.L. limits on v and θv computed with Feldman–Cousins prescription


Search for exotic contributions to atmospheric neutrino oscillations

(30,130) GeV

(28,142) GeV


Maximum likelihood analysis in intermediate e n region

Maximum Likelihood analysis in intermediate En region

Event-by-event analysis best use of existing information

106 events with

Minimization of the negative log-likelihood function:

Method tested on “mass-induced” oscillations 

MACRO parameters well reproduced

Average v < 10-25, slowly varying with m2


Conclusions

Conclusions

  • The inclusion of LIV effects does not improve the fits to the muon energy data

  • The limits for LVI parameters at 90% CL are

    at sin22θv = 0 : Dv/2 < 3 10-24

    at sin22θv = 1 : Dv/2 < 1.4 10-26


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