The community vigorously moves towards new experimental infrastructures to resolve outstanding key questions in neutrino astro- and particle physics, notably the neutrino mass hierarchy, the octant of Θ23, leptonic CP-violation, neutrino-less double beta decay and sterile neutrinos. Large new underground detectors and neutrino-telescope extensions would not only allow to study those intrinsic neutrino particle properties, but also to observe neutrinos from galactic super novae, from the sun and the Earth. Continua a leggere Neutrinos in Astro- and Particle Physics
Un gruppo di astrofisici dell’University of California a San Diego hanno misurato le minuscole distorsioni gravitazionali nella radiazione polarizzata che risale all’Universo delle origini. Lo studio di queste microonde primordiali potrà fornire un importante test cosmologico per verificare alcune concetti fondamentali della relatività generale, permettendo non solo di stimare la massa dei neutrini ma anche di capire come sono distribuite nello spazio sia la materia scura che l’energia scura.
arXiv: A Measurement of the Cosmic Microwave Background B-Mode Polarization Power Spectrum at Sub-Degree Scales with POLARBEAR
We announce the XV Vulcano Workshop, which will be held from May 18th to May 24th, 2014 in the Vulcano Island (Sicily, Italy). As in the past editions, the workshop will aim to gather people from High Energy Astrophysics and Particle Physics to discuss the most recent highlights in these fields.
The workshop will cover the following topics:
- Dark Matter
- Particle Physics
- Cosmic Rays
- Gamma/Neutrino Astronomy
- Future Prospects
Gli scienziati avrebbero risolto uno dei problemi aperti dell’attuale modello cosmologico standard combinando i dati del satellite Planck e quelli ottenuti grazie al fenomeno della lente gravitazionale allo scopo di determinare la massa dei neutrini.
The team, from the universities of Nottingham and Manchester, used observations of the Big Bang and the curvature of spacetime to accurately measure the mass of these elementary particles for the first time. The recent Planck spacecraft observations of the Cosmic Microwave Background (CMB), the fading glow of the Big Bang, highlighted a discrepancy between these cosmological results and the predictions from other types of observations. The CMB is the oldest light in the Universe, and its study has allowed scientists to accurately measure cosmological parameters, such as the amount of matter in the Universe and its age. But an inconsistency arises when large-scale structures of the Universe, such as the distribution of galaxies, are observed. Dr Adam Moss, from The University of Nottingham’s School of Physics and Astronomy said: “We observe fewer galaxy clusters than we would expect from the Planck results and there is a weaker signal from gravitational lensing of galaxies than the CMB would suggest. A possible way of resolving this discrepancy is for neutrinos to have mass. The effect of these massive neutrinos would be to suppress the growth of dense structures that lead to the formation of clusters of galaxies.” Neutrinos interact very weakly with matter and so are extremely hard to study. They were originally thought to be massless but particle physics experiments have shown that neutrinos do indeed have mass and that there are several types, known as flavours by particle physicists. The sum of the masses of these different types has previously been suggested to lie above 0.06 eV (much less than a billionth of the mass of a proton). Dr Moss and Professor Richard Battye from The University of Manchester have combined the data from Planck with gravitational lensing observations in which images of galaxies are warped by the curvature of spacetime.
They conclude that the current discrepancies can be resolved if massive neutrinos are included in the standard cosmological model.
They estimate that the sum of masses of neutrinos is 0.320 +/- 0.081 eV (assuming active neutrinos with three flavours). Professor Battye added: “If this result is borne out by further analysis, it not only adds significantly to our understanding of the sub-atomic world studied by particle physicists, but it would also be an important extension to the standard model of cosmology which has been developed over the last decade”.
Nottingham University: Massive neutrinos solve a cosmological conundrum arXiv: Evidence for massive neutrinos from CMB and lensing observations
The workshop will last 5 weeks in total, including two one-week conferences on SNe and GRBs respectively. More than 100 people are expected to participate in each conference (capacity of the conference hall at YITP is 120 people maximally). The remaining 3 weeks are spent for workshops where participants can hear seminars in the morning and enjoy free discussions in the afternoon. The capacity of the visitor facilities at YITP during the 3-week workshop is 50 maximally. The main scopes of the 3-week workshop are Nuclear Physics in CC-SNe and GRBs (Oct. 14-18), CC-SNe (Oct. 21-25), and GRBs (Nov. 4-8). Participants can choose their favorite dates to stay in Kyoto during the workshop. We can offer some financial support, although the budget is limited. We will also arrange a textbox on the financial support in the registration form (registration form will open in April 2013).
- Explosion Mechanism of Core-Collapse Supernovae
- Equation of State for High-Density Matter
- Structure of Neutron Stars as Remnants of CC-SNe
- Collapsars and Magnetars as Central Engine of Long Gamma-Ray Bursts
- Merging Compact Binaries as Central Engine of Short Gamma-Ray Bursts
- Neutrinos and Gravitational Waves as Signals of Death of Massive Stars
- Progenitors of CC-SNe and GRBs
- Multi-Wavelength Observations of SNe, GRBs, and their Remnants
- Plasma Physics, Particle Acceleration, and Radiation Process in Shocks of SNe, GRBs, and their Remnants
- UHECRs and VHE-Neutrinos & Gamma-Rays from GRBs
- Explosive Nucleosynthesis in SNe and GRBs
TeV Particle Astrophysics (TeVPA) is an annual international meeting in particle astrophysics. The UC Irvine particle physics and astrophysics groups will host TeVPA in 2013 at Irvine, California.
This meeting will focus on topical issues in:
- sources and propagation of cosmic rays,
- high-energy gamma rays,
- multi-wavelength probes of high-energy astrophysics,
- high-energy neutrino physics
- searches for dark matter.
Grazie ad uno studio recente guidato da un gruppo di fisici inglesi e giapponesi è stato possibile confermare che le particelle subatomiche, denominate neutrini, possiedono una nuova identità. Questi risultati, che danno inoltre credito agli esperimenti realizzati in Giappone presso il rivelatore T2K che ha lo scopo di studiare l’oscillazione dei neutrini, potrebbero un giorno aiutare gli scienziati a capire come mai l’Universo contiene in gran parte materia e solo ‘poche tracce’ di antimateria (vedasi Enigmi Astrofisici).
Alfons Weber, a professor of Physics at STFC and the University of Oxford is one of many scientists in the UK working on T2K. He explains: “The UK particle physics community was one of the driving forces behind this experiment. We not only provided part of the detector that characterises the beam, but also designed the target that produces the neutrinos in the first place. The long years of hard work have now come to fruition. Our findings now open the possibility to study this process for neutrinos and their antimatter partners, the anti-neutrinos. A difference in the rate of electron or anti-electron neutrino being produced may lead us to understand why there is so much more matter than antimatter in the Universe. The neutrino may be the very reason we are here“.
In 2011, the T2K collaboration announced the first indication of this process. Now with 3.5 times more data and a significance of 7.5 sigma, this behaviour is firmly established and can now be called a discovery.
There are three types, or ‘flavours,’ of neutrinos, one paired with the electron (called the electron neutrino), and two more paired with the electron’s heavier cousins, the muon and tau leptons. These different flavours of neutrinos can spontaneously change into each other, a phenomenon called neutrino oscillations. Observations have previously been made of a number of different types of oscillations, however the T2K results are the first discovery of the appearance of electron neutrinos in a beam of muon neutrinos, and it is this kind of oscillation which is the key to making measurements to distinguish the oscillations of neutrinos and anti-neutrinos. To explore the neutrinos’ oscillations, the T2K experiment fired a beam of neutrinos from the J-PARC laboratory at Tokai Village on the eastern coast of Japan, and detected them at the Super-Kamiokande neutrino detector, 295 km away in the mountains of the north-western part of the country. Here, the scientists looked to see if the neutrinos at the end of the beam matched those emitted at the start.
They found 22.5 neutrinos appearing in the beam of muon neutrinos, where if there were no oscillations they only expected to see an average of 6.4. This indicates the discovery of the new type of oscillation.
Now the team must make more accurate measurements of this new oscillation, and then run their experiment with an anti-neutrino beam to see if the results change. Professor Dave Wark of the Science and Technology Facilities Council (STFC) and Oxford University, leads the UK’s involvement in the international experiment. He said: “It’s a joy to see T2K deliver the science we designed it for. I have been working on this for more than a decade, and what these results tell us is that we have more than another decade of work ahead of us. We have seen a new way for neutrinos to change, and now we have to find out if neutrinos and anti-neutrinos do it the same way. If they don’t, it may be a clue to help solve the mystery of where the matter in the Universe came from in the first place. Surely answering that is worth a couple of decades of work!“.
Ogni secondo, trilioni di particelle chiamate neutrini attraversano il nostro corpo. Queste particelle elusive hanno una massa così piccola che non è stata ancora misurata. Inoltre, esse interagiscono debolmente con la materia che è quasi impossibile rivelarle e ciò rende molto complicato studiare le loro proprietà.
Since arriving at MIT in 2005, Joseph Formaggio, an associate professor of physics, has sought new ways to measure the mass of neutrinos. Nailing down that value, and answering questions such as whether neutrinos are identical to antineutrinos, could help scientists refine the Standard Model of particle physics, which outlines the 16 types of subatomic particles (including the three neutrinos) that physicists have identified. Those discoveries could also shed light on why there is more matter than antimatter in the Universe, even though they were formed in equal amounts during the Big Bang. “There are big questions that we still haven’t answered, all centered around this little particle. It’s not just measuring some numbers; it’s really about understanding the nature of the equation that explains particle physics. That’s really exciting”, Formaggio says. Formaggio, the only child of Italian immigrants, was the first in his family to attend college. Born in New York City, he spent part of his childhood in Sicily, his parents’ homeland, before returning to New York. From an early age, he was interested in science, especially physics and math. At Yale University, he studied physics but was also interested in creative writing. The summer after his freshman year, in search of a summer job, he “called every publishing house in New York City, all of which resoundingly rejected me”, he says. However, his call to the Yale physics department yielded an immediate offer to work with a group that was doing research at the Collider Detector at Fermilab. That led to a senior thesis characterizing the excited states of the upsilon particle, which had recently been discovered. As a student, Formaggio was drawn to both particle physics and astrophysics. At Columbia University, where he earned his PhD, he started working in an astrophysics group that was studying dark matter. Neutrinos were then thought to be a prime candidate for dark matter, and the mysterious particles intrigued Formaggio. He eventually joined a neutrino research group at Columbia, which included Janet Conrad, a professor who is now at MIT. While a postdoc at the University of Washington, Formaggio participated in experiments at the Sudbury Neutrino Observatory (SNO), located in a Canadian nickel mine some 6,800 feet underground. Those were the first experiments to show definitively that neutrinos have mass, albeit a very tiny mass. Until then, “there were definitely hints that neutrinos undergo this process called oscillation where they transmute from one type to another, which is a signature for mass, but all the evidence was sort of murky and not quite definitive”, Formaggio says. The SNO experiments revealed that there are three “flavors” of neutrino that can morph from one to the other. Those experiments “basically put the nail in the coffin and said that neutrinos change flavors, so they must have mass”, Formaggio says. “It was a big paradigm shift in thinking about neutrinos, because the Standard Model of particle physics wants neutrinos to be massless, and the fact that they’re not means we don’t understand it at some very deep level”. Another possible discovery that could throw a wrench into the Standard Model is the existence of a fourth type of neutrino (post). There have been hints of such a particle but no definitive observation yet. “If you put in four neutrinos, the Standard Model is done”, Formaggio says, “but we’re not there yet”.
In his current work, Formaggio is focused on trying to measure the mass of neutrinos.
In one approach, he is working with an international team on a detector called KATRIN, located in a small town in southwest Germany. This detector, about the size of a large hangar, is filled with tritium, an unstable radioactive isotope. When tritium decays, it produces neutrinos and electrons. By measuring the energy of the electron released during the decay, physicists hope to be able to calculate the mass of the neutrino, an approach based on Einstein’s E=mc2 equation. “Because energy is conserved, if you know how much you started out with and how much the electron took away, you can figure out how much the neutrino weighs”, Formaggio says. “It’s a very hard measurement but I like it because the experiment is a giant electromagnetic problem”. The KATRIN detector is under construction and scheduled to begin taking data within the next two years. Formaggio is also developing another tritium detector, known as Project 8, which uses the radio frequency of electrons to measure their energies. Formaggio hopes that one day, tritium-based detectors could be used to find neutrinos still lingering from the Big Bang, which would require even larger quantities of tritium. “There are many holy grails in physics, and finding those neutrinos is definitely one of them. People look at the light from the Big Bang, but that’s actually closer to 300,000 years old, or thereabouts. Neutrinos from the Big Bang have been around since the first second of the Universe”, Formaggio says.
- Sterile-neutrino hunt gathers pace at Gran Sasso (physicsworld.com)
- Particle Pals: Neutrino Experiment Shows Protons and Neutrons Pairing Up (scientificamerican.com)
- Lab plans meetings for neutrino experiment (rapidcityjournal.com)
- What are neutrinos, and how do they come from beyond our solar system? (io9.com)
The 33rd International Cosmic Ray Conference (ICRC2013) will be held from 2-9 July, 2013, in Rio de Janeiro, Brazil. The Conference is organized under the auspices of the International Union of Pure and Applied Physics (IUPAP) and is hosted by the Centro Brasileiro de Pesquisas Físicas (CBPF). The ICRC is the major conference in the area of Astroparticle and Solar Physics, and aims to cover all areas of research under this heading.
Specifically these are: 1. Solar and Heliospheric Physics; 2. Cosmic Ray Physics; 3. Gamma Ray Astronomy; 4. Neutrino Astronomy; 5. Dark Matter Physics.
Those that attend regularly this conference will notice that there are new features:
– the inclusion of Dark Matter research as a main branch of the program;
– a Scientific Program Committee of leading experts on the areas mentioned above, will help in setting an attractive topical scientific program.