The universe is almost 14 billion years old. An inconceivable length of time by human standards – yet compared to some physical processes, it is but a moment. There are radioactive nuclei that decay on much longer time scales. With the XENON1T detector at the INFN Gran Sasso National Laboratory, scientists were able to observe the decay of Xenon-124 atomic nuclei for the first time.
The half-life of a process is the time after which half of the radioactive nuclei present in a sample have decayed away. The half-life measured for Xenon-124 is about one trillion times longer than the age of the universe. This makes the observed radioactive decay, the so-called double electron capture of Xenon-124, the rarest process ever seen happening in a detector. “The fact that we managed to observe this process directly demonstrates how powerful our detection method actually is – also for signals which are not from dark matter,” says Prof. Christian Weinheimer from the University of Münster (Germany) whose group leads the study. In addition, the new result provides information for further investigations on neutrinos, the lightest of all elementary particles whose nature is still not fully understood.
XENON1T is a joint experimental project of about 160 scientists from Europe, the US and the Middle East. The results were published in the science journal “Nature” (preprint on the arxiv).
The full press release is available from their website: http://www.xenon1t.org/ and further information is also available here.
Needle-like structures on positively charged lightning leaders
Lightning above LOFAR (montage). Credit: University of Groningen, Olaf Scholten
In contrast to popular belief, lightning often does strike twice, but the reason why a lightning channel is ‘reused’ has remained a mystery. Now, an international research team led by the University of Groningen has used the LOFAR radio telescope to study the development of lightning flashes in unprecedented detail. Their work reveals that the negative charges inside a thundercloud are not discharged all in a single flash, but are in part stored alongside the leader channel at interruptions. This occurs inside structures which the researchers have called needles. Through these needles, a negative charge may cause a repeated discharge to the ground. The results were published on April 18 in the science journal Nature.
“This finding is in sharp contrast to the present picture, in which the charge flows along plasma channels directly from one part of the cloud to another, or to the ground”, explains Olaf Scholten, Professor of Physics at the KVI-CART institute of the University of Groningen. The reason why the needles have never been seen before lies in the ‘supreme capabilities’ of LOFAR, adds his colleague Dr Brian Hare, first author of the paper: “These needles can have a length of 100 metres and a diameter of less than five metres, and are too small and too short-lived for other lightning detections systems.”
Low Frequency Array (LOFAR) is a Dutch radio telescope consisting of thousands of rather simple antennas spread out over Northern Europe. These antennas are connected with a central computer through fibre-optic cables, which means that they can operate as a single entity. LOFAR is developed primarily for radio astronomy observations, but the frequency range of the antennas also makes it suitable for lightning research, as discharges produce bursts in the VHF (very high frequency) radio band.
Reference:
Needle-like structures discovered on positively charged lightning branches; Brian Hare, Olaf Scholten et al.; „Nature“, 2019; DOI: 10.1038/s41586-019-1086-6
On April 10th 2019, the Event Horizon Telescope (EHT) Collaboration presented its first results – an image of the supermassive black hole in galaxy M87 – in multiple simultaneous press conferences around the world. The official EHT press release is available from their website.
For the first time scientists have succeeded in taking a direct image of a black hole. The EHT is a large telescope array consisting of a global network of radio telescopes. By combining data from several very-long-baseline interferometry (VLBI) stations around Earth and using several independent methods the first image of a black hole was produced.
This breakthrough was announced in a series of six papers published in a special issue of The Astrophysical Journal Letters. The image reveals the black hole at the center of Messier 87, a massive galaxy in the nearby Virgo galaxy cluster. This black hole resides 55 million light-years from Earth and has a mass 6.5 billion times that of the Sun.
From 2nd to 10th October 2019 ECAP organises the 16th edition of the international School for Astroparticle Physics for PhD students in Obertrubach Bärnfels, close to Erlangen, Germany. The school will be held in english and is open for international participation.
The program covers topics from astrophysics to particle physics and cosmology. Lectures are given by key scientists in the field, as for example, Karl-Heinz Kampert (cosmic rays), Imre Bartos (astrophysics with gravitational wave observations), Jacco Vink (particle acceleration and magnetic fields in cosmic shocks) and Bela Mojorovits (light dark matter). The school combines education, discussion and contributions by the participants. The participation fee of 280 Euro covers accommodation and meals (breakfast, lunch, dinner, coffee breaks).
On the slopes of the Mt. Elbrus, the 16th International Baksan School on Astroparticle Physics was held, organized jointly by the Institute for Nuclear Research (INR) of RAS and the Joint Institute for Nuclear Research (JINR) with the participation of the Astroparticle Physics European Consortium (APPEC) and the Russian Foundation for basicResearch (RFBR). After a 15-year break, the world-famous series of schools held near the Baksan Neutrino Observatory of the INR RAS was revived.
Among the participants of the School, there were 58 postgraduates, senior students, and young scientists from 9 countries of three parts of the world. Participation of European students became possible thanks to APPEC support; many Russian listeners were supported by JINR and the INR RAS, and the RFBR grant gave an opportunity to cover the business trip expenses of invited lecturers. “At the School, I saw a well-balanced composition of the deepened theoretical basis, the modern state of science and the view on future astrophysical experiments, and all this was presented by great lecturers. A large number of fairly good questions asked by participants, and their vivid interaction confirms the great success of the School that should definitely be held again in the same format,” as quoted by Thomas Berghöfer (DESY, Germany), who also delivered the lecture “Ultimate Low Light-Level Sensor Development”.
A more comprehensive report can be found in their press release and on the webpage which also provides additional material.
The Dawn V meeting to assess and develop world-wide coordination for the next generation of ground-based gravitational-wave observatories will be held at the Virgo/EGO Observatory from 26-27 May 2019 in Cascina, Italy. It follows the GWADW meeting in Elba, Italy, and the PAX VI meeting (starting immediately after Dawn, in Cascina)
With the observation of the first gravitational-wave event from a binary neutron star, GW170817, during Advanced LIGO and Virgo’s second observation run, multimessenger astronomy with gravitational waves has started. The current generation of gravitational-wave detectors now serves a wide community including fundamental physics, astrophysics, astronomy, cosmology and nuclear physics. The observations to date and their widespread impact on science make the argument for future facilities quite compelling.
The one and one-half day program of this meeting will have a focus on the recently completed Gravitational-Wave International Committee study of third generation detectors (3G), and seeking the next significant steps for the community to realize the future network. Of particular interest is the proper coordination between the European effort proposing to build an observatory detailed by the ‘Einstein Telescope’ design study, and the U.S. proposal of a similar class observatory, named ‘Cosmic Explorer’.
We are happy to announce the SENSE Detector School at the Ringberg Castle in Kreuth am Tegernsee in Bavaria, Germany, from 19 – 22 June 2019. The 2.5 days mini-school for PhD and master students aims to inform about the forefront developments on low light-level detectors.
The speciality of the school is the small group of students with a continuous possibility to discuss with the teachers.
The participation of 25 students is sponsored by SENSE. You can apply for the school until 3 May 2019 with a letter of motivation. The nomination of participants will be announced on 10 May 2019. We aim to achieve a balanced mix of working topics as well as gender and nationalities.If required, childcare can also be organised.
As soon as the timetable has been finalised, a decision will be made on a possible contribution from the students.
The 36th ICRC will be held in beautiful Madison, Wisconsin, USA from July 24th – August 1st.
The International Cosmic Ray Conference, or ICRC, is a physics conference organized biennially by the Commission C4 (Astroparticle Physics) of the International Union of Pure and Applied Sciences (IUPAP) since 1947, where physicists from the world present the results of their research in Astroparticle Physics. The meeting covers cosmic-ray physics, neutrino physics, gamma-ray astonomy, dark matter, particle astrophysics, and detector techniques in these fields.
Rear-side view of a suspended mirror. Image credit: EGO/Virgo Collaboration/Perciballi.
The Virgo and LIGO detectors are ready to start the new Observing run called O3, lasting a whole year. The hunt for gravitational waves is set to start on April 1st when the European Virgo detector, based in Italy at the European Gravitational Observatory (EGO), and the LIGO twin detectors, located in the state of Washington and Louisiana (USA), will start to take data becoming together the most sensitive gravitational wave observatory to date.
During a one-year period the LIGO and Virgo Collaborations will register science data continuously, and the three detectors will operate as a global observatory. Since August 2017, the end of the second observation run O2, the two collaborations have intensively worked on their interferometers to improve the sensitivity and reliability. Scientists have also improved their offline and online data analysis and developed further the procedures for releasing Open Public Alerts: these will within minutes notify the physics and astronomy community when a potential gravitational-wave event is observed.
The scientific output of observation run O3 is expected to be tremendous and it will potentially reveal new exciting signals coming from new sources.
The Helmholtz Association is funding an international graduate school for multi-messenger astronomy, which is organised by DESY, the Humboldt University Berlin, the University of Potsdam and the Israeli Weizmann Institute of Science.
Multimessenger astronomy, the exploration of the Universe using a multitude of cosmic messengers, has led to several groundbreaking discoveries during the last few years, many of which built on significant contributions from the partner institutions.
With a new generation of instruments, advanced methods of exploiting their data, as well as extensive theoretical modeling, members of this research school have unique research opportunities in this emerging field.
The partner institutions are involved in several leading observatories, e.g. the Cherenkov Telescope Array, the IceCube neutrino observatory or the Zwicky Transient Facility, to which the students will have access.
From 2nd to 10th October 2019 ECAP organises the 16th edition of the international 
On the slopes of the Mt. Elbrus, the 16th International Baksan School on Astroparticle Physics was held, organized jointly by the Institute for Nuclear Research (INR) of RAS and the Joint Institute for Nuclear Research (JINR) with the participation of the Astroparticle Physics European Consortium (APPEC) and the Russian Foundation for basicResearch (RFBR). After a 15-year break, the world-famous series of schools held near the Baksan Neutrino Observatory of the INR RAS was revived.
