In preparation of the next generation of gravitational wave telescopes, a 20-meter prototype, called the ETpathfinder, will be built in Maastricht. Now the first researchers around Prof. Stefan Hild have moved into the hosting building. At the beginning of next year, construction of the prototype for the Einstein Telescope will begin.
Model of the ETpathfinder. (Credits: Marco Kraan, Nikhef)
The location of the actual Einstein telescope will not be finally decided until 2021, but the Meuse–Rhine Euroregion around the city-corridor of Aachen–Maastricht–Liège, is under consideration. The Einstein telescope, Europe’s next-generation ground-based interferometer, which is more than a billion of euros, will be able to measure gravitational waves with unprecedented precision and range and to gain an insight into the early days of the universe.
To reach this goal new technologies need to be developed and shall be investigated at the ETpathfinder. “It needs to be at least 10 times more sensitive than the current generation of detectors. So we first have to develop the right low-noise technologies. Think of the glass used in the mirrors. To be able to ‘listen’ to gravitational waves, which are actually ripples in space and time, the material has to be cooled to the extreme. That’s not possible with glass, so we’re developing mirrors made of silicon”, Hild explains in an interview with M. van der Linde.
Artist view of the Einstein Telescope. (Credits: Marco Kraan, Nikhef)
The Prototype ETpathfinder is a true-to-scale model of the Einstein telescope, which will be used to test and optimize new techniques. For this purpose, a former transport hall is converted into a clean room with a low-vibration floor in which two approx. 20-metre-long arms of the interferometer are to be accommodated. The prototype is focused on cryogenic payloads to reach the following science goals:
Build a low phase noise interferometry with cryogenic silicon mirrors of up to ~100kg
Provide a flexible testbed to explore various combinations of cryogenic temperatures and laser wavelength
Investigate the interplay of thermal noise, quantum noise and control noises in the sub 10Hz region
Perform various tests of cryogenic issues (liquids vs cryo-coolers; stable control of mirror temperature; contamination handling of mirror surfaces; low power actuators …)
Commission of a testbed for new control techniques and sensors
The prototype is partly financed by an Interreg Euregio Meuse-Rhine Project and partly by different funds from the involved Institutes and Institutions. You can find a list of these partners below.
With the construction of the Pathfinder, they hope not only to gain new physical knowledge and experience in technology, but also to better position the Euregio in the decision on the final location of the Einstein telescope and to strengthen cooperation and gravitational wave knowledge in this region.
As mentioned in the roadmap, APPEC strongly supports further actions strengthening the collaboration between gravitational-wave laboratories. It also strongly supports Europe’s next-generation ground-based interferometer, the Einstein Telescope (ET) project, in developing the required technology and acquiring ESFRI status.
List of involved Institutes/Institutions
with funding from the Interreg Programm Meuse-Rhin:
The PLI (precision laser inclinometer), newly developed by CERN and JINR in Dubna, Russia (APPEC observer and member, respectively), is a new kind of seismometer that is relatively cheap and can be very sensitive, especially at low frequencies. A network of such devices has the potential of composing an efficient early warning seismic system for the High-Luminosity Large Hadron Collider (HL-LHC). During discussions at the ATF, it became soon clear that Advanced Virgo could also profit from such a system, increasing sensitivity in gravitational-wave detection at lower frequencies. For this reason, with the help of the Italian INFN, a PLI has been already tested at EGO (European Gravitational Observatory), where the upgraded version of Virgo is installed.
Interview with Christian Weinheimer on the recent publication of the first KATRIN results
The long awaited science run at KATRIN took place in spring this year. On Monday, 16th of September the analysis results were finally presented during a Colloquium at KIT: An upper limit for the neutrino mass of 1.1 eV was found and, maybe more important, it was shown that this complex experiment is working properly. In the following interview Christian Weinheimer is sharing his view on the impact of these results.
KATRIN has just released results in a presentation and a paper now in the archive. This is extremely important since you could derive a model independent limit to the absolute mass scale of neutrinos which are at least a factor of 2 better than previous results.
Can you explain to the non-experts the meaning of your result and the impact on cosmology and particle physics itself?
Let me stress that the most important outcome of this first 4 weeks science run of KATRIN is that the experiment is working, it has started neutrino mass measurements and we understand the data. Much more is going to come in the near future.
Concerning the importance for particle physics and cosmology: In contrast to analyses of cosmology data from CMB and LSS et al. or the searches for neutrinoless double beta decay, the KATRIN result is a model-independent result from the lab. It constrains neutrino masses and the contribution of neutrinos to (hot) dark matter (and the corresponding consequences for structure formation in the universe) by a factor two more stringently than before. Of course we know that the limit from cosmological analyses are much stronger than the present 1.1 eV limit from KATRIN, but they are not free from model assumption. There is still the not entirely satisfactory situation, that in these cosmological analyses the major part of matter is parametrized as cold dark matter, but we have not discovered the nature of dark matter yet. And, there are still some frictions in cosmology data, e.g. the exact value of the Hubble constant H0.
This result sets a milestone after only 4 weeks of measurements for leading in about 1000 days to a possible limit of 0.2 eV (90%CL).
From having reached the present result after 4 weeks only, one might expect to reach the 0.2 eV sensitivity even early. Unfortunately it will not go fast. We are sensitive to the observable m2(ν). To go from 1 eV to 0.2 eV requires a factor 25 improvement of the experiment. Therefore we expect to reach the KATRIN design sensitivity after 1000 days of measurements. We will soon, i.e. still in September, start data taking with a factor 5-10 better signal-to-background ratio.
Overview of the KATRIN setup (Credits: Steffen Lichter, KIT)
What are the main experimental challenges in this measurement which you foresee?
The main experimental challenges of KATRIN is to operate the whole experiment very stable over long periods of time: It requires to run the windowless gaseous tritium source stable at the per milllevel w.r.t. temperature, gas inlet pressure and tritium concentration. The KATRIN pre and main spectrometer have to be operated at extremely good vacuum (1E-11 mbar) and at a ultrastable high voltage at the ppm (1E-6) level. The many superconducting magnets have to run smoothly and stable as well as our electron detector. In principle we have demonstrated that we meet all these requirements, but now all the complicated components have to work continuously for years in such a stable manner. I should emphasize that fulfilling the mentioned requirements was not easy at all. To make this all happen, in many cases the KATRIN Collaboration had to advance technology that now benefits the whole community.
The remaining challenges are to lower the background further and to control the plasma properties sufficienctly well. Here we are on a good way: We will take the next science data at lower background rate already and we demonstrated avoiding any radial dependence of the effective endpoint of the experimental beta spectrum by coupling the plasma potential to the rear wall of our windowless gaseous tritium source by adjusting the rear wall potential.
In your view, is there any scientific program which could lead to a measurement of the mass in the next 10 years?
Neglecting the limits from cosmological analyses, the neutrino mass to be seen in tritium beta decay can be any value below the present upper limit by KATRIN of 1.1 eV and 50 meV in the inverted neutrino mass ordering scenario, and 10 meV in the normal mass ordering scenario. Within KATRIN we have some R&D projects to improve KATRIN’s sensitivity further below the 200 meV, but the 10 meV with a guaranteed discovery potential seems to be out of reach. There is Project 8, still in the R&D phase, which aims on a sensivity of 40 meV using an atomic tritium source and determining the beta electron energy by cyclotron resonance electron spectroscopy. There is some hope to reach this 40 meV sensitivity within a decade, but it will be very challenging. And there are the projects to determine the neutrino mass with cryogenic bolometer arrays investigating the electron capture process of Ho-163. The current limit of the ECHo experiment amounts to 150 eV and will be improved towards about 10 eV soon with the potential to reach the sub-eV regime with larger detector array in the future.Therefore we have to be lucky to detect the neutrino mass with these direct methods within the next 10 years, but our community will certainly find a way to finally measure the neutrino mass in the laboratory.
Of course, most people expect neutrinos to be Majorana particles. The next generation of neutrinoless double beta decay experiments can cover a significant part of the above mentioned inverted mass ordering scenario within the next 10 years.
Christian Weinheimer (Credits: Beatrix von Puttkamer, KIT)
Prof. Christian Weinheimer is group leader at the Institute for Nuclear Physics at the University of Münster. Since 2001 he is involved in KATRIN and is, together with Guido Drexlin, spokesperson of the experiment. He is an expert in neutrino physics and already for his PhD he dealt with the neutrino mass. Besides he is involved in the search for dark matter and is member in the XENON100 and XENON1/nT as well as the DARWIN experiment.
Overview of the KATRIN setup. (Credits: Steffen Lichter, KIT)
Neutrinos and their small non-zero masses play a key role in cosmology and particle physics. The allowed range of the mass scale has now been narrowed down by the initial results of the international Karlsruhe Tritium Neutrino Experiment (KATRIN).
The observation of neutrino oscillations two decades ago proved that neutrinos possess a small non-zero mass, contrary to earlier expectations. Accordingly, they play a prominent role in the evolution of large-scale structures in the cosmos as well as in the world of elementary particles, where their small mass scale points to new physics beyond known theories. Over the coming years, the most precise scale of the world, the international KATRIN experiment located at the Karlsruhe Institute of Technology (KIT), is set to measure the mass of the fascinating neutrinos with unprecedented precision.
Members of the international collaboration convene in the KATRIN control room at the Karlsruhe Tritium Laboratory during the spring 2019 neutrino mass measurement campaign. (Credits: Joachim Wolf, KIT)
In the past years, the KATRIN collaboration, formed by 20 institutions from 7 countries, successfully mastered many technological challenges in the commissioning of the 70 m long experimental setup. In spring this year, the big moment finally arrived: the 150-strong team was able to “put neutrinos on the ultra-precise scale of KATRIN” for the first time. The analysis of a first four-week measurement run in spring 2019 limits neutrino masses to less than approximately 1 eV, which is smaller by a factor of 2 compared to previous laboratory results based on multi-year campaigns. This demonstrates the huge potential of KATRIN in elucidating novel properties of neutrinos over the coming years.
This result was first released at the TAUP conference and was later officially presented during a colloquium on September 16, 2019, at the North Campus of the KIT. With lectures by Christian Weinheimer, Guido Drexlin, Kathrin Valerius, Susanne Mertens and Thierry Lasserre and a press conference, the impressive result was presented.
This first edition focuses on Multi-Messenger Astrophysics. These past two years were marked by huge advancements in this field, with countless invaluable results such as the detection of first gravitational waves, also in correspondence with photons, as well as the simultaneous observation of photons with a 300 TeV neutrino from an active galaxy. The foundation of high energy astroparticle physics are shaken and new theoretical buildings are raised. This calls for additional focused experimental efforts, with careful planning of multi-wavelenght and multi-experiments coordinated observation, specially when pointing telescopes with limited field of view are involved.
This school aims to recall the cosmology and particle physics background needed to seriously frame the discussion about multi-messenger signatures. The school will be organized with key lectures, plus a series of topical lectures and seminars. Exercises will be organized throughout the school on all topics. Hands-on will be organized on a selection of codes. The school will be closed with a final exam for self-evaluation.
The school will be international and it will be held in the beautiful curtains of the Asiago plateau, where the DFA astronomical observatory is located. The observatory is currently hosting two 1m-class telescopes hosting several instruments.
Participants will be limited to 36 and selected on the basis of their CV and a reference letter.
Deadline for support request and for Visa request: November, 8 2019.
Deadline for registration: December 8, 2019.
With the development of CMB Stage-IV in North America and the selection of LiteBIRD in Japan, the European CMB community needs to put medium- and long-term CMB planning in place in order to consolidate, exploit and extend the CMB expertise it has acquired in the last decade.
The meeting “Towards the Coordination of the European CMB program”, held September 12-13, 2019 at the AstroParticle/Cosmology (APC) Labs in Paris, France, assembled experiment builders, observers and agency representatives in a continuing effort to chart the next steps towards European coordination on CMB experiments, including collaboration in technology development, and seeking synergy with similar efforts in other parts of the world.
In addition to presentations on recent CMB results and the scientific questions of the next decade, this meeting was unique in that it specifically targeted longer-term plans for different collaborations and countries. While the LiteBIRD satellite will help define the CMB “landscape” in the coming decade, national space agencies and ESA are working with European scientists now to define European involvement. For large, ground-based efforts such as the US DOE- and NSF-proposed CMB-S4, a unified European framework is proving more difficult to assemble.
This meeting is an effort to address this. There were presentation not only from the CMB-S4 spokespeople, but also from European groups proposing to work with American CMB-S4 precursor experiments as well as from current European CMB experiment.
This workshop was the 5th in the “Florence Process” meeting series, previous meetings being held in Florence, though scheduling conflicts made it easier to hold this meeting in Paris. The agendas of these previous meeting can be found here for 2018, here for 2017, here for 2016, and here for 2015. The workshop coordinators were Carlo Baccigalupi, François Bouchet, Michael Brown, Anthony Challinor, Ken Ganga, Eiichiro Komatsu, Aniello Mennella, Enrique Martínez-Gonzalez, Joe Mohr and José-Alberto Rubiño-Martín.
On the 18th and 19th of June the APPEC Scientific Advisory Committee came together at CERN. The purpose of the meeting was to bring everyone up to date and to discuss and distribute future tasks. This includes the activities of the neutrinoless double beta decay committee, who is currently planning an APPEC community meeting on October 31. Furthermore, the establishment of a Dark Matter direct detection committee is ongoing and a draft mandate document is sent to the APPEC General Assembly for approval. In the field of CMB, a common European strategy is still under discussion, therefore a meeting is planned for September. (https://indico.in2p3.fr/event/19414/)
The proposal of regular APPEC Town meetings was discussed with great interest and approved. It was agreed to aim for a meeting in Fall 2020 and the Scientific Advisory Committee will give input on the topics to discuss.
Gian Francesco Giudice, Teresa Montaruli, Eckhard Elsen and Job de Kleuver signing the official agreement for EuCAPT. Credits: CERN
On the 10th of July the European Center for Astro Particle Theory, EuCAPT was officially launched at CERN, which is also the first central hub for the next 5 years.
The first director is Gianfranco Bertone who is chairing a steering committee of 12 partners. The aim of EuCAPT is to coordinate and favour the already existing activities in several European centers and institutions active in astroparticle theory. The main activities organised by EuCAPT will include:
a. An annual general meeting of the European theoretical astroparticle physics community at the central hub;
b. Thematic workshops to be organised by other participating institutions;
c. The central hub will host dedicated meetings for small groups of scientists to consolidate/finalize collaborative projects and common proposals;
d. Coordination of existing/planned activities of the participating institutions to prevent overlaps and enrich the overall portfolio. Activities that are part of the coordinated portfolio will be labelled as EuCAPT activities;
e. Contacts/coordination with ApP theorists from all over the world favouring collaboration/visits and bolstering common actions also with institutions not belonging to the EuCAPT;
f. Advice, referee support, training concerning funding proposals;
g. Create and operate an EuCAPT website, including an activity calendar.
Along with the official launch the first meeting of the steering committee took place. We are looking forward to a fruitful cooperation which will further advance the progress in the field of theoretical Astroparticle Physics.
Francesca Moglia, Antoine Kouchner, Antonio Masiero, Gian Francesco Giudice, Teresa Montaruli, Gianfranco Bertone, Eckhard Elsen, Job de Kleuver, Tony Riotto and Silvia Pascoli. Credits: CERN
Interview with Silvia Pascoli about the upcoming meeting and the roadmap on neutrinoless double beta decay
One of the recommendations on the neutrinos in the APPEC Roadmap sounds:
‘APPEC strongly supports the present range of direct neutrino-mass measurements and searches for neutrinoless double-beta decay. Guided by the results of experiments currently in operation and in consultation with its global partners, APPEC intends to converge on a roadmap for the next generation of experiments into neutrino mass and nature by 2020.’
Currently, APPEC aims to implement this recommendation. The adopted strategy for the future of neutrinoless double beta decay is the nomination of a panel, following the proposition by the SAC of a mandate document highlighting the panel duties, which was approved by the General Assembly in Granada on May 16, 2019.
The panel, is chaired by Prof. Silvia Pascoli (Durham U., UK) and it is composed by Andrea Giuliani (CNRS/IN2P3, France), J.J. Gomez Cadenas (DIPC, Spain), Ezio Previtali (Milano-Bicocca, Italy),Ruben Saakyan (UCL, UK), Karoline Schaner (GSSI, Italy) and Stefan Schönert (TUM, Germany). It is in charge of writing a document with a critical analysis on the technologies that Europe could pursue for establishing the new generation of neutrinoless double beta decay.
This document will be discussed and endorsed by the APPEC SAC until the APPEC Community Meeting on Neutrinoless Double Beta Decay in London, on October 31. There the inputs from the scientific community will be collected. Once the community comments are received and the document is updated, it will be discussed and approved by the APPEC SAC and General Assembly. The document will then be used in international fora to represent the Community view.
We briefly examine with Silvia the aim of the document and the meeting in London:
Silvia, you have provided an excellent service work to the community together with the panel by writing the 0νββ specific roadmap document and organising the APPEC Community meeting.
What scientific goal you see in the reach for the next 10 years?
Neutrinoless double beta decay plays a key role in the field as it is the most sensitive way we have to search for the violation of lepton number. This information is essential to hunt for the origin of neutrino masses. The next generation of neutrinoless double beta decay experiments will reach the decay rates relevant if the ordering of neutrino masses is inverted, covering a crucial area in the parameter space. I also do not discard the possibility of surprises as neutrinoless double beta decay is very sensitive to more exotic lepton number violating physics.
Which are according to you the major challenges that the 0νββ will have to face in this decade?
Neutrinoless double beta decay is an exceedingly rare process. The main challenges we face are the reduction of backgrounds to unprecedented levels and at the same time increasing the masses to the ton-scale. The community has devised new experimental ways to address this challenges and it is now the time to put them at work.
What theoretical and R&D efforts should we concentrate on to prepare for the successive decade?
From the knowledge of neutrino masses we have, we know that the predictions for the decay rates could be longer than the reach of the next generation of experiments, in particular if neutrino have a normal ordering of masses. This means that 10-ton scale experiments are needed with even further reduced backgrounds, ideally background-free, and excellent energy resolution. There are some preliminary ideas on how this could be achieved but substantial R&D is needed to turn these ideas into real experiments. On the theoretical side, an important aspect we need to make significant progress on is the computation on the nuclear matrix elements. New techniques are becoming available and we may be on the verge of a breakthrough. The collaboration with the nuclear theory community is essential for this purpose.
What do you hope for this community meeting?
Following a long tradition, Europe is playing a leading role in neutrinoless double beta decay with experiments such as GERDA, CUORE and NEXT. It is essential that this leadership continues in the future. It is an opportunity that we should not miss. To this aim, strong support is needed for this field, focusing on the most sensitive and most promising experiments. At the community meeting we plan to discuss the options for the next generation and to consolidate the wishes of the community for a strong European programme.
Silvia Pascoli is professor at Durham University. After getting her ‘laurea” in theoretical physics at the University of Trieste under the supervision of Antonio Masiero, she obtained her PhD at SISSA (Trieste, Italy) studying the properties of neutrinos with Serguey Petcov. She then moved to UCLA for her postdoc and then at CERN. Since 2005 she is at Durham University where she continues to work on neutrino physics, in all relevant areas, Theory, Phenomenology, Astroparticle Physics and more recently Cosmology. In 2016 she was awarded a Wolfson Research Merit Award by the Royal Society.
This first edition focuses on Multi-Messenger Astrophysics. These past two years were marked by huge advancements in this field, with countless invaluable results such as the detection of first gravitational waves, also in correspondence with photons, as well as the simultaneous observation of photons with a 300 TeV neutrino from an active galaxy. The foundation of high energy astroparticle physics are shaken and new theoretical buildings are raised. This calls for additional focused experimental efforts, with careful planning of multi-wavelenght and multi-experiments coordinated observation, specially when pointing telescopes with limited field of view are involved.
With the development of 
