The MACRO experiment and its legacy: more than three decades of astroparticle and neutrino physics

27 Jun 2025, 08:00 → 28 Jun 2025, 19:30 Europe/Rome

LNGS and GSSI

It has been over 35 years since the MACRO experiment (Monopole, Astrophysics, and Cosmic Ray Observatory) began collecting data in Hall B of the Gran Sasso Underground Laboratory. As one of the first large international Astroparticle physics collaborations, MACRO set the stage for an impressive array of scientific and technical achievements to follow and launched the careers of many of today’s scientific and technical leaders. This conference will review different topics of this remarkable scientific legacy in nowadays Astroparticle physics and related fields.

 

Friday, 27 June ¶

08:00 → 08:30 Bus from L'Aquila to LNGS¶

08:30 → 09:00 Registration

09:00 → 09:20 Welcome from institutional representatives (INFN, LNGS, GSSI)¶

09:20 → 09:45 The birth of MACRO: the US point of view¶

Speaker: Barry Barish (Caltech)

09:45 → 10:10 The birth of MACRO: the Italian point of view¶

Speaker: Enzo Iarocci (Sapienza University and INFN Rome)

10:10 → 10:20 Commerative Plaque Ceremony

10:20 → 11:00 MACRO Science, then and now: Magnetic Monopoles¶

Conveners: Erik Katsavounidis (MIT), Laura Patrizii (INFN Bologna)

10:20 Back to the pre-MACRO days: Theory and Experiment¶

I will review the theoretical and experimental landscape from 1974 to 1989 regarding the Grand Unified Theory magnetic monopole questions that have since been addressed by MACRO. The most important of these is the broad velocity range over which flux limits have been set. The presentation will include anecdotes, recollections of colorful characters, and the joys of living in Italy.

Speaker: Steven Ahlen (Boston University)

10:40 Magnetic Monopole searches at the time of MACRO and beyond¶

The experimental searches for GUT magnetic monopoles will be briefly reviewd starting with MACRO times and then extending to running expoeriments.

Speaker: Ivan De Mitri (Gran Sasso Science Institute (GSSI) and INFN)

11:00 → 11:10 Group Photo

11:10 → 11:40 Coffee Break

11:40 → 12:20 MACRO Science, then and now: Cosmic Rays¶

Conveners: Ivan De Mitri (Gran Sasso Science Institute (GSSI) and INFN), Daniele Martello (Università del Salento and INFN)

11:40 Cosmic ray physics at LNGS: a historical journey¶

Two unexpected experimental outcomes challenged existing theories and strongly impacted the design of initial experiments at LNGS. The main outcomes in the field of Cosmic Ray Physics will be reviewed.

Speaker: Sergio Petrera (GSSI, L'Aquila)

12:00 Cosmic rays from deep underground to space¶

Measurements of cosmic rays are made using their atmospheric secondary products from deep underground or over an extended area at the ground surface, but also with instruments flown by balloons and rockets to catch the primary particles directly. The present generation of direct measurements now overlap in energy those made with secondary detection, providing a fertile cross calibration and new insights on the nature and origin of these particles. We present a brief overview of the present state of direct cosmic ray measurements of nuclei (composition, primary, secondary, isotopes, ultraheavy), building on the legacy of the pioneering MACRO studies.

Speaker: Stephane Coutu (Penn State University)

12:20 → 13:15 Recollections: At play amidst the Strangeness and Charm¶

Conveners: Erik Katsavounidis (MIT), Marco Monteno (INFN Torino)

12:20 At play amidst the Strangeness and Charm¶

Speaker: Several Speakers

13:15 → 14:30 Lunch

14:30 → 16:15 Session: Visit to the underground Lab - Group 1¶

14:30 → 15:45 Splinter discussions

15:45 → 16:45 Coffee Break

16:15 → 18:00 Session: Visit to the underground Lab - Group 2¶

16:45 → 18:00 Splinter discussions

18:00 → 18:30 Bus from LNGS to L'Aquila¶

20:00 → 23:00 Social Dinner

Ristorante "Magione Papale", via Porta Napoli, 67/I , L’Aquila

Saturday, 28 June ¶

09:00 → 09:40 Recollections: Experiments and Experiences¶

Convener: Francesco Cafagna (INFN, Sezione di Bari)

09:00 Postcards from MACRO¶

A personal overflight on the experience and activities in MACRO experiment.

Speaker: Antonio Surdo (INFN - Lecce)

09:20 The history of MACRO streamer tubes¶

Following the scheme of a MACRO note, written in the autumn of 1994, 10 years after the MACRO proposal, I would like to summarize the scientific and technological path which led to the design and construction of the streamer tube system of the MACRO experiment. It is also a chance to acknowledge the contribution of all the people and groups which participated to the effort.

Speaker: Giuseppe Battistoni (INFN)

09:40 → 10:40 MACRO Science, then and now: Neutrinos Astronomies¶

Convener: Gregory Tarle (University of Michigan)

09:40 The birth of Neutrino Astronomy¶

Cosmological hypotheses and oracular dreams of grand-unification foretold that neutrinos might weigh a little bit, that those elusive particles could blow up stars, and that active galactic nuclei could power hyper-energetic neutrinos. Testing those theories demanded new technologies, optimized to search for rare interactions. Those theories led to the invention of MACRO and other gigantic undergrounf detectors. Let's recall the early days of that technologies.

Speaker: Lawrence Sulak (Physics Dept, Boston University)

10:00 MACRO and the early days of the supernova warning systems¶

I will reminisce about PHRASE and ERP and SkyTel beepers and the pre-SNEWS days of gravitational collapse early warnings, and discuss the evolution to the current day.

Speaker: Kate Scholberg (Duke University)

10:20 The relevance of MACRO results for hih energy neutrino telescopes¶

The MACRO detector was one of the largest experiments pioneering high energy astrophysics with neutrinos.

The successive generation of detectors in the Mediterranean Sea (ANTARES and KM3NeT) inherited not only the experimental techniques and part of the simulation codes for the neutrino signal, but also the information needed to describe and characterize the background of atmospheric muons.

I’ll describe how MACRO contributed to different aspect of neutrino astrophysics up to the observation of a 200 PeV neutrino event in KM3NeT.

Speaker: Maurizio Spurio (University of Bologna and INFN)

10:40 → 11:10 Coffee Break

11:10 → 11:50 MACRO Science, then and now: Neutrino Oscillations¶

Conveners: Ed Kearns (Boston University), Maurizio Spurio (University of Bologna and INFN)

11:10 MACRO and neutrino oscillations¶

Speaker: Paolo Bernardini

11:35 The early evidences for atmospheric neutrino oscillations¶

When you have eliminated the impossible, whatever remains, however improbable, must be the truth. – Sherlock Holmes
The earliest data collected by MACRO was analyzed for upward going muons, indicative of neutrino interactions in the ground a few meters below the detector. The sources of these neutrinos were expected to be from pion decay due to cosmic ray interactions, and, at much lower intensities, galactic (e.g., X-ray binaries) or extra-galactic (e.g., Active Galactic Nuclei) sources. When data from the first super-module’s inaugural run was analyzed, a lower number of upward going muons was observed than expected, albeit not up to the standard of statistical significance required, and was dismissed as a statistical anomaly. Other aspects of the analysis however, lent credence to the veracity of the finding. This analytical approach is described in detail.

Speaker: Neil Pignatano (RTX (ret.), ex-Caltech)

11:50 → 13:10 MACRO Legacies¶

Convener: Paolo Lipari (INFN Rome)

11:50 Flattening the Universe - a scientific journey from Monopoles to Dark Energy¶

Back in 1983, when I got involved in the hunt for Grand Unified (GUT)
Magnetic Monopoles, it was possible that there were enough of them to flatten (close)
the Universe. MACRO searched for GUT monopoles at levels below the closure and
Parker Bound(s) and didn’t find any. A belief in the Inflationary Universe led scientists
like me to search for Dark Matter but there was not enough to flatten the Universe.
Then the accelerating Universe was discovered, and it was thought that a mysterious
form of Dark Energy provided the missing energy needed to flatten the Universe. My
involvement with the Dark Energy Survey (DES) and the Dark Energy Spectroscopic
Instrument (DESI) arose from my original motivating question that got me involved with
MACRO – “what flattens (closes) the Universe?” Just this year DESI released the
results of 3 years of its planned 5-year survey and to everyone’s surprise, discovered
that Dark Energy is dynamic. I will briefly describe this remarkable scientific journey
that has led me and my colleagues from Monopoles to Dark Energy and into the
interiors of Black Holes.

Speaker: Gregory Tarle (University of Michigan)

12:10 From the unlikely to the impossible: how magnetic monopoles paved the way to the first direct detection of gravitational waves¶

The morning (in Eastern US) of September 14, 2015 was marked by a watershed moment in physics and astronomy, the first direct detection of gravitational waves. A magnetic monopole detection would had been an equally landmark event, alas, nature was not as generous. In this brief presentation, I will connect the path to the gravitational wave detection with the journey of MACRO's and the broader scientific community's to detect magnetic monopoles of astrophysical/cosmological origin.

Speaker: Erik Katsavounidis (MIT)

12:30 Multimuon events from cosmic rays with the ALICE detector¶

ALICE experiment at CERN Large Hadron Collider, located 52 meters underground, carried out a cosmic data-taking campaign in the period 2025-2018 corresponding to 62.5 days of live time. In this work the analysis of these data is limited to multimuon events defined as events with more than four detected muons. In particular the muon multiplicity distribution (MMD) is studied in the low-intermediate multiplicity (4 < Nμ < 50), corresponding on average primary energy from 4 PeV up to 60 PeV. For the higher multiplicities, dominated by large fluctuations, is measured the rate of the high muon multiplicity (HMM) events (Nμ>100). The results are compared with Monte Carlo simulations using three of the main hadronic interaction models describing the air shower development in the atmosphere: QGSJET-II-04, EPOS-LHC, and SIBYLL 2.3d. Two extreme compositions of primary cosmic rays were simulated: pure proton and pure iron representing respectively the lightest and the heavier composition. Although the models have difficulty in describing precisely the composition trend of cosmic rays, QGSJET-II-04 is the only model that reproduces reasonably well the MMD and the rate of HMM events assuming a heavy composition for the entire energy range studied.

Speaker: Mario Sitta (Università del Piemonte Orientale)

12:50 Muon tomography after MACRO¶

In the 1950s, E. P. George measured the penetrating muon rates to gauge the overburden densities over a tunnel in Australia. Later in 1969, Luis Alvarez pioneered muon tomographic imaging by staging a spark chamber in the second pyramid of Chephren in Giza, Egypt. A quarter century after Alvarez, the MACRO collaboration measured the subterranean muon angular distribution that characterized the Apennine mountains over the Gran Sasso Laboratory. In the intervening period up to the present, muon tomography has benefited from improvements in detector technology, including scintillator materials, photodetection, and data processing. Muon tomography is maturing to a point where it might be used reliably for subsurface imaging of geological or mechanical structures. This presentation reports on a new pilot project organized at Tel Aviv University for radiographic imaging in a biblical-era archaeological site adjacent to the southern flank of the Old City of Jerusalem, Israel. A 40 x 40 x 40 cm³ detector, consisting of four layers of interleaved extruded plastic scintillators produced at FNAL and read out by a Hamamatsu silicon photomultiplier array, has been staged in a cave near the Gihon Spring. The objective is to search for muon flux anomalies that may indicate the presence of subterranean water conduits from antiquity.

Speaker: Daniel Levin (University of Michigan, Physics)

13:10 → 14:30 Lunch

14:30 → 15:30 MACRO Legacies¶

14:30 Cosmic Rays: signal or background ?¶

From the study of underground multimuon events to their effects in surface neutrino experiments

Speaker: Ornella Palamara (Fermilab)

14:50 Monopole, Astrophysics and Cosmic Ray observations with long baseline experiments¶

The MINOS and NOvA long baseline neutrino experiments have near detectors 100m underground at Fermilab and far detectors in Minnesota 700m underground (MINOS) and on the surface with minimal overburden (NOvA). They are large highly segmented scintillator detectors like MACRO for good cosmic ray tracking and timing, and have followed up on MACRO measurements of the cosmic ray seasonal variations and moon and sun shadows. Addtionally, the NOvA far detector would be sensitive to supernova neutrinos and magnetic monopoles amongst all those cosmics, continuing all the letters in MACRO.

Speaker: Alec Habig (University of Minnesota Duluth)

15:10 From neutrinos underground to water, ice and space¶

I will describe the starting steps in MACRO to selected results of IceCube, ANTARES/KM3NeT and then to future from space

Speaker: Teresa Montaruli (University of Geneva - Departement de physique nucleaire et corpusculaire)

15:30 → 16:30 The future of MACRO Science¶

16:30 → 16:45 Summary and Farewell¶

16:45 → 17:15 Goodbye Coffee