Lorenzo Perrone (University & INFN of Lecce) for the MACRO Collaboration

1. TAUP 2001 Topics in Astroparticle and underground physics Laboratori Nazionali del Gran Sasso, Italy September 8-12, 2001 Neutrino astronomy with MACRO Lorenzo Perrone (University & INFN of Lecce) for the MACRO Collaboration

2. Summary of contents • Frame • Hypotheses Neutrino Astronomy: motivation • Requirements • Background from the models to detection…… MACRO as a neutrino telescope Data analysis search for a diffuse neutrino flux from unresolved sources search for a neutrino signal from point-like sources MACRO vs. current data and theory

3. Why neutrino astronomy? deflected (E  1 EeV) and absorbed (l 50 Mpc at E  50 EeV) Protons undeflected but absorbed (l 50 Mpc at E  1 TeV) Photons undeflected but short lifetime ( l ~10 kpc at E ~ 1 EeV) Neutrons undeflected and not absorbed on cosmological distances Neutrinos T H E O R Y 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. GRBs AGNs Neutrinosnoriginate in hadronic interactions of accelerated protonspwith matter and/or radiationsurrounding the source

4. Neutrino Astronomy: detection technique • Background: • atmosphericm • atmosphericn CHARGE CURRENT INTERACTION 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

5. MACRO as a neutrino detector • 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 (s ~ 0.5 ns) • ~ 20000 m 2 streamer tubes for tracking (intrinsic angular resolution ~ 0.5O) Pointing capability checked with Moon shadow: < 1O

6. 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.) the simulation of very high energy muon propagation has been properly treated (Bottai et al. NIM A, 459, 319, 2001) Distribution of the total energy released in the scintillator counters: the effect of the energy cuts whole sample of events arriving at the detector Total energy released 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 Initial energy

7. DATA analysis: results Data collected by MACRO in the period 4/94 - 12/2000 have been analyzed A D D E D cutS: significant evidence of an upward-going event cutQ: quality condition on scintillator timing Checked and improved the response of the scintillators to large deposit of energy No significant signal has been found with respect to the statistical fluctuations of the atmospheric neutrino background Scintillator track: any association between different scintillator layers by time of flight geometrical length 1/b = +1 downward 1/b = -1 upward Distribution of 1/b for the scintillator tracks of one high energy survived candidate after imposing cutS. The effect of cutQ are shown as the shaded area

8. Display of a candidate high energy neutrino event

9. Display of a candidate high energy neutrino event

10. Upper limit on the diffuse flux from unresolved sources live-time 5.8 yr Upper limit on muon flux Fm ~ 1.710-14 cm -2 s -1 sr -1 Upper limit on neutrino flux (power law index g =2) E2 Fn ~ 4.5 10-6 Gev cm -2 s -1 sr -1

11. 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

12. Search for point-like neutrino sources 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) 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 by pointing to known sources (several catalogues have been considered) MACRO 90% c.l. upper limit for 42 selected sources (full red dots). Upper limits from other experiments are also shown

13. Space-Time correlation with g-ray bursts 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) No significant excess has been found with respect to the background

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