Lorenzo Perrone

(University & INFN of Lecce)

for the MACRO Collaboration

Neutrino astronomy with MACRO

TAUP 2001 Topics in Astroparticle and underground physics

Laboratori Nazionali del Gran Sasso, Italy

September 8-12, 2001

Neutrino Astronomy: motivation

from the models to detection……

MACRO as a neutrino telescope

MACRO vs. current data and theory

Data analysis

search for a diffuse neutrino flux from unresolved sources

• Frame

• Hypotheses

Summary of contents

• Requirements

• Background

search for a neutrino signal from point-like sources

Why neutrino astronomy?

High energy neutrinos in a range from few GeV up to 107 GeV are expected from a wide class of galactic (binary systems and SNRs) and extragalactic (AGNs and GRBs) sources.

Protonsdeflected (E 1 EeV) and absorbed (50 Mpc at E 50 EeV)

undeflected butabsorbed (50 Mpc at E 1 TeV)

Photons

undeflected but short lifetime ( ~10 kpc at E ~ 1 EeV)

Neutrons

Neutrinos undeflected and not absorbed on cosmological distances

GRBs

Neutrinos originate in hadronic interactions of accelerated protons p with matter and/or radiation surrounding the source

AGNs

T

H

E

O

R

Y

Neutrino Astronomy: detection technique

B A S I C R E Q U I R E M E N T S

* large geometrical area (0.1-1 km2)

* well shielded site (underground, underwater/ice)

* high sensitivity at high energy

* good capability to discriminate the background

* precise particle tracking for pointing purposes

Background:• atmospheric • atmospheric

CHARGE CURRENT INTERACTION

• Large acceptance (~10000 m2sr for an isotropic flux)

• Low rate of cosmic ray muons (~10 –6 the surface rate)

• ~ 600 ton. liquid scintillator planes for time

measurement (~ 0.5 ns)

• ~ 20000 m 2 streamer tubes for tracking (intrinsic angular resolution ~ 0.5O)

MACRO as a neutrino detector

Pointing capability checked with Moon shadow: < 1O

Simulation of the signal from AGNs: selection of a sample of high energy events

13500 events -Teq=2988 yr - have been simulated on the surface of a box containing MACRO according to the analytical distributions of energy and zenith angle (Stecker & al.)

cut01: at least 1 counter with Erel > 500 MeV

cut02: at least 2 adiacent counters each one with Erel > 500 MeV

cutE: cut01 and cut02 plus a further “box” with Erel > 500 MeV

Distribution of the total energy released in the scintillator counters: the effect of the energy cuts

To

tal

ener

gy

rele

ased

Initial energy

whole sample of events arriving at the detector

the simulation of very high energy muon propagation has been properly treated (Bottai et al. NIM A, 459, 319, 2001)

DATA analysis: results

L

tc

1

Rate of survived events in 5.8 yr

ATMO 1.1±0.5stat

AGN 0.54±0.03stat

DATI 2

cutQ: quality condition on scintillator timing

cutS: significant evidence of an upward-going event

Scintillator track:

any association between different scintillator layers

by time of flight

geometrical length

Data collected by MACRO in the period

4/94 - 12/2000 have been analyzed

No significant signal has been found with respect to the statistical fluctuations of the atmospheric neutrino background

Distribution of 1/ for the scintillator tracks of one high energy survived candidate after imposing cutS. The effect of cutQ are shown as the shaded area

1/ downward 1/ upward

A

D

D

E

DChecked and improved the response of the scintillators to large deposit of energy

Display of a candidate high energy neutrino event

Display of a candidate high energy neutrino event

Upper limit on the diffuse flux from unresolved sources

livetimearea efficiency

c.l.) (90%limit Upperc.l.) (90% Φ

~ 1.7 10-14 cm -2 s -1 sr -1

~ 4.5 10-6 Gev cm -2 s -1 sr -1

live-time

5.8 yr

Upper limit on muon flux

Upper limit on neutrino flux (power law index=2)

flux limit (90% CL)

E2

(Gev cm-2 s -1 sr –1)

Energy range (GeV)

Reference

EAS – TOP 2.0 10-3 105<E<106 Phys Lett. B 333 , 555 (1994)

SPS-DUMAND 6.0 10-4 105<E<106 Proc XXV ICRC, Durban (1997)

BAIKAL 1.4 10-5 104<E<107 Astropart. Phys 14, 61 (2000)

BAIKAL (e) 1.3 ÷ 1.9 10-5 104<E<107 Prepint astro-ph/0105269

Frejus 5.0 10-6 E ~2.6 103 Astropart. Phys 4, 217 (1996)

MACRO (this analysis) 4.5 10-6 104 <E<106 This analysis

AMANDA 1.0 10-6 E<106 Nucl.Phys.Proc.S 91, 423 (2000)

A look to theory and other experiments

PRESENT STATUS: current experiments (MACRO, AMANDA, BAIKAL) are not enough sensitive (at the moment) to confirm or completely exclude the theoretical predictions

FUTURE: neutrino telescopes of next generation (ANTARES, NEMO, NESTOR) are expected to reach this goal in few years of data taking

Goal: to investigate the possibility that the sample of 1356 upward-going muons detected by MACRO since 1989 shows evidence of neutrino point-like sources (see MACRO Coll., Ap.J., 546, 1038, 2001 for details)

Search for point-like neutrino sources

by pointing to known sources (several catalogues have been considered)

by looking around the direction of any upward going detected event:

Distribution of the number of events falling in cones of half width 1.5o, 3o, 5o (from top to bottom)

around the direction of any upward-going event

MACRO 90% c.l. upper limit for 42 selected sources (full red dots). Upper limits from other experiments are also shown

Space-time correlation with the GRBs detected by BATSE (catalogue 3B, 252 from 1991 to 1999) and by BeppoSax has been checked (see MACRO Coll., AP.J., 546, 1038, 2001 for details)

Space-Time correlation with -ray bursts

No significant excess has been found with respect to the background

CONCLUSIONS

The MACRO capability of detecting high energy neutrinos from astrophysical sources has been investigated

Checked and made reliable the simulation of high energy muon propagation

Checked and improved the response of the MACRO scintillators to large deposit of energy

a search for a diffuse neutrino flux from unresolved sources has been performed by energy information

No significant signal has been found with respect to atmospheric neutrino background

Data have been used to set a muon and a neutrino flux upper limits

a search for point-like neutrino sources as been performed by direction information •

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