F Ronga Frascati
Astroparticelle
(neutrini, raggi cosmici, onde gravitazionali, fisica generale)
Commissione Scientifica II
Sommario
• Cosa si intende per astroparticle e road map ApPEC
• Flash sui programmi e sulla situazione attuale del gruppo II
• Proposte in fase di discussione piu’ o meno avanzate
• Nuove idee
Piano triennale 2005 Frascati
F Ronga
1.2 Questions of astroparticle physics versione 0.1
Astroparticle Physics has evolved as a new interdisciplinary field at the intersection of particle physics, astronomy and cosmology. It combines the
experimental techniques and theoretical methods from both astronomy and physics. Particle physics is devoted to the intimate structure of matter and the
laws that govern it. Astronomy and astrophysics address the structure of the Universe and its evolution from the Big Bang. Modern cosmology links the
theory of particle physics with that of the very early Universe. Most discoveries in particle physics have immediate consequences on the understanding of the
Universe and, vice versa, discoveries in cosmology have fundamental impact on theories of the infinitely small.
Astroparticle physics addresses some of the most fundamental questions of contemporary physics. An answer to most of these questions would mark a major
break-through in understanding the Universe and would open an entirely new field of research by its own. Note that the list compiled here is to a large part,
but not entirely, identical to the “Eleven Science Question for the New Century” which have been compiled in 2002 by the
National Research Council of the US National Academies [1] and which extend beyond the field of astroparticle physics.
1) What is the nature of dark matter ?
Only 4% of the Universe is made of ordinary matter. Following latest measurements and cosmological models, 73% of the cosmic inventory seem to
consist of “dark energy” and 23% of dark matter. So, dark matter turns out to be the majority component of cosmic matter. It holds the Universe
together by the gravitational force but neither emits nor absorbs light. Dark matter (including a small admixture of massive neutrinos) has likely
played a central role in the formation of large scale structures in the Universe. Its nature is a mystery and can only be guessed. The discovery of
particles constituting dark matter would confirm a key element of the Universe as we understand it today. Astroparticle physicists have developed a
variety of tools for direct and indirect searches for dark matter candidates.
2) Do protons have a finite lifetime ?
Grand Unified Theories (GUTs) of particle physics predict that the proton has a finite lifetime. Actually, proton decay is one of the generic and best
testable implications of GUTs. The physics of proton decay is closely linked to the physics of the Big Bang and the matter-antimatter symmetry in the
Universe. The discovery of proton decay would be one of the most fundamental discoveries for physics and cosmology. It requires detectors of
Megaton size located deep underground.
3) What are the masses of the neutrinos? What is their role in cosmic evolution ?
Neutrinos have provided the first reliable evidence of phenomena beyond the Standard Model of particle physics. In the Standard Model, neutrinos
have no mass. A major breakthrough of the past decade is the discovery that neutrinos, in contrary, are massive. This evidence has been obtained from
the observation that neutrinos can change their identity and oscillate between different states. From the oscillation pattern, the mass differences
between different neutrino states but not the absolute values of the masses can be inferred. Dedicated experiments are sensitive to the absolute value
of the mass. Moreover, some of them may tell us whether the neutrinos are their own antiparticles – a discovery going much beyond the precision
measurement of their absolute mass. Massive neutrinos have likely played a role in the genesis of the matter-antimatter symmetry of the Universe and
in the formation of large scale cosmic structures.
Nearly a century ago, the Austrian physicist Victor Hess discovered cosmic rays, charged particles which hit our atmosphere like a steady rain. Later,
it turned out that some of these particles have energies a hundred million times above that of terrestrial accelerators. The observation of particles with
such breathtaking energies raises several questions: How can cosmic accelerators boost particles to these energies? What is the nature of the
particles? How do they propagate through the Universe? Does the comic ray spectrum extend beyond the maximum energy a proton can maintain
when travelling over large cosmic distances but eventually colliding with the omnipresent microwave background? A large flux above this energy
limit must likely be attributed to entirely new cosmic phenomena. The mystery of cosmic rays is going to be solved by an interplay of detectors for
high energy gamma rays, neutrinos and charged cosmic rays.
5) Can we detect gravitational waves? What will they tell us about violent cosmic
processes ?
Nature is governed by four fundamental forces: the electromagnetic force, the weak, force the strong (colour) force and the gravitational force. The
carriers of the first three have been studied in detail, starting with the discovery of electromagnetic waves in 1888. Gravitational waves are the only
missing of the carriers of basic forces. The emission of gravitational waves from accelerated masses is one of the central predictions of the Theory of
General Relativity. The confirmation of this conjecture would be fundamental by its own. On top of that, gravitational waves would provide us with
information on sudden cataclysmic processes in the Universe which are non accessible by other methods. With the new tools for gravitational wave
detection, the discovery of gravitational waves may be just around the corner.
6) What is the precise spectrum of low energy neutrinos emitted by the Sun? Can we
turn the Sun into a laboratory for precision particle physics and astrophysics ?
In 2002, Ray Davis and Masatoshi Koshiba were awarded the Nobel Prize in Physics for opening the neutrino window to the Universe, specifically
for the detection of neutrinos from the Sun and a Supernova. The observation that solar neutrinos change their identity on their way to Earth
(“neutrino oscillations”) has provided first indications of massive neutrinos, i.e. of physics beyond the standard model of particle physics. However,
so far only the high energy tail of solar neutrinos, a small fraction of the total, has been studied in detail. Precise measurements of the low-energy
neutrino spectrum would test our understanding of neutrino oscillations, would allow fine-tuning of picture of nuclear fusion deep inside the Sun and
would give hints on long-term variations of the Sun.
7) How do Supernovae explode? How were elements from iron to uranium made?
The diversity of nearly all elements heavier than helium is generated in stars and forms the basis of our own existence. We are made from the ashes of
Supernovae. Supernova explosions are governed by complicated hydrodynamic processes. Whereas the production of elements up to iron in stars and
supernovae is rather well understood, the origin of heavier elements is not yet resolved.
• Discussioni in corso per includere altri campi: dark energy (supernovae..), radiazione del big
bang, Double Chooz, neutrini con fasci non inclusi ma rientrano come Megaton detectors....
ecc
• Censimento Europeo ~ 80 schede di esperimento a livello di ApPEC ~4000 ricercatori ma
contati spesso due volte
• Ruolo del CERN strategic group..... evitare road map in direzioni diverse
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Competenza anche ApPEC
2006
Costi di operazione ~ 15 Meuro/anno quasi costante nei prossimi 4-5 anni
Proposte e lettere intento avanzate alla commissione
Mezzetto
proposta+referees
Mezzetto
proposta+referees
Proposte e lettere intento avanzate alla commissione
Lipari
Magic 2 proposta+referees
approvato scientificamente
Nemo Km3Net Km3
Ma altri gruppi della collaborazione premono per Auger Nord
Proposte e lettere intento avanzate alla commissione
Braccini
proposta+referees
Proposte e lettere intento avanzate alla commissione
proposta+referees
fase di R/D
indagini su lanciatore
proposta+referees
Nuove idee presentate nella riunione
del 3 novembre 2005
formati gruppi di studio sulle varie linee scientifiche