Final results on atmospheric oscillations with MACRO at Gran Sasso

Bari, Bologna, Boston, Caltech, Drexel, Frascati, Gran Sasso, Indiana, L’Aquila, Lecce, Michigan, Napoli, Pisa, Roma1, Texas,

Torino, Oujda

• Gran Sasso Lab. – MACRO

• oscillations. Atmospheric neutrinos

• Upthroughoing muons (E 50 GeV )– Zenith distribution– Absolute value– L/E distribution: E from M.C.S.

• Monte Carlos

• Semicontained muons Upstopping muons

• Combining all information

• Conclusions

E 4 GeV

G. GiacomelliUniversity of BolognaEPS, Aachen

RatioAbsolute value

- Oscillations

Weak flavour eigenstates e, ,

Mass eigenstates 1, 2, 3

Decays, Interactions + + , n -p

Propagation 1(t) = 1(0) e-E t

Mixing 1 = 3m = 1 Ulm m

2-Flavour = 2 cos23 + 3 sin 23

Mixing = -2 cos23 + 3 sin 23

Oscillations in Vacuum (over a distance L)

Disappearance P( ) = 1 – sin2 223 sin2 (1.27 m2

23 L/E)

Appareance P( ) = 1 – P( )

m223 = m2

3 – m22

Simple formulae -Additional flavour oscillations

Modified by -Matter effects

In case of -Neutrinos have masses m ≠ 0

Oscillations -Le, L, L, L violation

-neutrino decays

E : 0.1 GeV 100 GeV

L : 20 km 13000 km

L/ E : 1 km/GeV 105 km/GeV

Downgoing : “near” neutrino source

Upgoing : “far” neutrino source

Atmospheric neutrinos

The MACRO detector

3 types of Scintillators ( 600 t)Subdetectors Streamer tubes

Nuclear track detectors

Acceptance in : 10-4 1S 10,000 m2 sr for isotropic flux

12 m horizontalDimensions: 76.6 m in length

9.3 m height

Subdivided in 6 supermodules, with a lower

and an upper part

NIM A324(1993)337NIM A486(2002)663

MACRO cross section (schematic)

Upthroughgoing muons

MC SIMULATION (17% scale error):Bartol Group flux Phys. Rev. D53 (1996) 1314 inter. Cross sections: Z. Phys. C67 (1995) 433 Transport in the rock CERN-EP / 85-03 (1985)Detector simulation: GEANT3

Shape of zenith distribution + L/E distributionm2 = 2.5 10-3 eV2, sin2 2 = 1 Significance ~ 4.7

PL B357(1995)481PL b434(1998)451hep-ex/0206027

Monte Carlos

• New FLUKA and HKKM: complete three dimensional MCs with improved hadronic model

• Predictions of FLUKA and HKKM agree perfectly

• Shapes of zenith distributions with and without oscillations are the same in old Bartol flux, new FLUKA and new HKKM

• Using the latest primary Cosmic Ray fits:

Absolute values are ~ 20-30% lower than MACRO and SUPER K data

• Using previous Cosmic Ray fits:

Absolute values are 5-10% lower than MACRO, SUPER K

Need to improve these fits

L/E Distribution

● Black points : upthroughgoing data

○ Open point : Internal Up (IU) data

Green and red lines: MC predictions for

oscillations with the mentioned parameters

point-to-point syst. error (12%)Shaded region:

NIM A492(2002)376 hep-ex/0304037

Zenith distributions for IU and (ID+UGS)

Shaded regions: no oscillation MC (21% scale error)Black lines: MC predictions for oscillationswith m2 = 2.5 10-3 eV2 and sin2 2 = 1

Data are in agreement with MCOSC with the quoted parameters

262 events

164 events

< E > 4 GeV

PL B478(2000)5hep-ex/0206027

Combination of indipendent data

Zenith distrib.

Energy measur.

).(cos).(cos4070

1

NN

NN

Rhoriz

vert

highE

lowE

NN

R 2

H.E.50 GeV

L.E.4 GeV )(

)(ainedupsemicontN

ntaineddownsemicoupstoppingNR

3

Absolute H.E. Scale error 17%

Values L.E. Scale error 21%

MACRO data are consistent with

oscillations, with Maximal mixing m2 = 0.0023 eV2

( 5 significance)

Conclusions