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Search for exotic contributions to Atmospheric Neutrino Oscillations

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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

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

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

MACRO data

MonteCarlos

Upthroughgoing

n1

En = 13 GeV

En = 36 GeV

MC predictions for

nm nt oscillations

with the MACRO

parameters

En = 88 GeV

En =146 GeV

300 events with

θ<60 degrees

No oscillation Bartol96

MC predictions for nm nt

oscillations with the best

MACRO parameters

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

Best fit parameters for nm nt

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

Eur. Phys. J. C36(2004)357

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

MACRO

D

q

Mass induced oscillations

2 n flavor interpretation:

induced by the mixing

of 2 mass eigenstates

,

and 2 weak eigenstates

,

:

The survival probability is

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)

Mixed oscillations

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

where

and

P(nmnt)

Mixed

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

(30,130) GeV

(28,142) GeV

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

- 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