- Published on 22 July 2016
New theoretical models that better describe the interaction between dark matter and ordinary particles advance the quest for dark matter
In the quest for dark matter, physicists rely on particle colliders such as the LHC in CERN, located near Geneva, Switzerland. The trouble is: physicists still don't exactly know what dark matter is. Indeed, they can only see its effect in the form of gravity. Until now, theoretical physicists have used models based on a simple, abstract description of the interaction between dark matter and ordinary particles, such as the Effective Field Theories (EFTs). However, until we observe dark matter, it is impossible to know whether or not these models neglect some key signals. Now, the high energy physics community has come together to develop a set of simplified models, which retain the elegance of EFT-style models yet provide a better description of the signals of dark matter, at the LHC. These developments are described in a review published in EPJ C by Andrea De Simone and Thomas Jacques from the International School for Advanced Studies SISSA, in Trieste, Italy.
- Published on 12 July 2016
Theory to explain collective effects of neutrinos inside supernovae strengthened
Neutrinos are elementary particles known for displaying weak interactions. As a result, neutrinos passing each other in the same place hardly notice one another. Yet, neutrinos inside a supernova collectively behave differently because of their extremely high density. A new study reveals that neutrinos produced in the core of a supernova are highly localised compared to neutrinos from all other known sources. This result stems from a fresh estimate for an entity characterising these neutrinos, known as wave packets, which provide information on both their position and their momentum. These findings have just been published in EPJ C by Jörn Kersten from the University of Bergen, Norway, and his colleague Alexei Yu. Smirnov from the Max Planck Institute for Nuclear Physics in Heidelberg, Germany. The study suggests that the wave packet size is irrelevant in simpler cases. This means that the standard theory for explaining neutrino behaviour, which does not rely on wavepackets, now enjoys a more sound theoretical foundation.
- Published on 22 March 2016
The publishers of The European Physical Journal C – Particles and Fields are pleased to announce the appointment of Professor Laura Baudis as new Editor-in-Chief. This follows the splitting of the experimental section into Experimental Physics I: Accelerator Based High-Energy Physics, now led by Jos Engelen, and Experimental Physics II: Astroparticle Physics, now led by Laura Baudis.
Laura Baudis is a Professor at the University of Zurich. Her research interests are in astroparticle physics and cosmology, in particular in the fields of direct dark matter detection and neutrino physics.
- Published on 27 January 2016
Highest sensitivity detector ever used for very light dark matter elementary particles
The origin of matter in the universe has puzzled physicists for generations. Today, we know that matter only accounts for 5% of our universe; another 25% is constituted of dark matter. And the remaining 70% is made up of dark energy. Dark matter itself represents an unsolved riddle.
Physicists believe that such dark matter is composed of (as yet undefined) elementary particles that stick together thanks to gravitational force. In a study recently published in EPJ C, scientists from the CRESST-II research project use the so-called phonon-light technique to detect dark matter. They are the first to use a detection probe that operates with such a low trigger threshold, which yields suitable sensitivity levels to uncover the as-yet elusive particles responsible for dark matter.
- Published on 13 January 2015
Study shows significant progress in determining what dark matter is not made of, thanks to much more sensitive detectors capable of identifying the presence of elusive particles, called WIMPs
According to astronomical observations, dark matter constitutes a five times greater proportion of the universe than ordinary matter, which only makes up 5% of the matter in the universe. The remaining 70% of the universe is known as dark energy. However, we still do not know what dark matter is made of. Indeed, none of the known elementary particles fulfil the criteria to explain dark matter. One theory suggests that it consists of as yet unknown elementary particles that interact only very weakly with ordinary matter, fittingly called WIMPs (Weakly Interacting Massive Particles). Now, members of the CRESST (Cryogenic Rare Event Search with Superconducting Thermometers) collaboration have analysed recent data showing what dark matter is not made of, from a new kind of detector for such particles. This work has recently been published in EPJ C.
- Published on 01 January 2014
As of January 2014, The European Physical Journal C – Particles and Fields will be published as full open access journal funded by SCOAP3. One of the leading journals in the field, EPJ C was selected to participate in this initiative - lead by CERN with the support of partners in 24 countries - which will make a vast fraction of scientific articles in the field of High-Energy Physics open access at no cost for any author. Moreover authors will retain copyright and creative commons licenses will enable wide re-use of the published material.
- Published on 23 July 2013
Understanding complexity in the early universe may require combining simpler models to interpret cosmological observations
Complicated statistical behaviour observed in complex systems such as early universe can often be understood if it is broken down into simpler ones. Two physicists, Petr Jizba (currently affiliated with the Czech Technical University in Prague), and Fabio Scardigli (now working at Kyoto University in Japan), have just published results in EPJ C pertaining to theoretical predictions of such cosmological systems’ dynamics.
EPJ C Highlight - Curvature Oscillations in Modified Gravity Theories as Possible Source of Ultra-High-Energy Cosmic Rays
- Published on 07 December 2012
The origin of ultra-high-energy cosmic rays, with energies around the GZK cutoff, remains an unsolved mystery. In the present letter a novel and intriguing explanation is suggested that links far-reaching fundamental aspects of F(R) modified theories to an efficient production of highly energetic cosmic rays during the recent history of the Universe.
At the core of this work lies the proof that in cosmological and astrophysical systems with rising energy densities, the F(R) modified theories of gravity exhibit powerful oscillations of the curvature scalar R, with an amplitude much larger than the standard value of curvature predicted by the General Relativity. These oscillations are strongly anharmonic, with frequencies that can be as large as billions of GeV. This striking and rather unexpected oscillatory behavior of R lends support to the idea that ultra-high energy cosmic rays can be generated by such curvature oscillations at the appropriate cosmological redshifts.
Curvature oscillations in modified gravity and high energy cosmic rays. E.V. Arbuzova, A.D. Dolgov, L. Reverberi (2012), European Physical Journal C 72:2247, DOI 10.1140/epjc/s10052-012-2247-z
- Published on 10 August 2012
An anomaly in the behaviour of ordinary particles may point to the existence of mirror particles that could be candidates for dark matter responsible for the missing mass of the universe. In a paper recently published in EPJC, researchers hypothesised the existence of mirror particles to explain the anomalous loss of neutrons observed experimentally. The existence of such mirror matter had been suggested in various scientific contexts some time ago, including the search for suitable dark matter candidates.
- Published on 10 August 2012
Physicists have developed the first conclusive test to better understand high-energy particles correlations.
Researchers have devised a proposal for the first conclusive experimental test of a phenomenon known as "Bell’s nonlocality". This test is designed to reveal correlations that are stronger than any classical correlations, and do so between high-energy particles that do not consist of ordinary matter and light. These results are relevant to the so-called "CP violation" principle, which is used to explain the dominance of matter over antimatter. These findings by Beatrix Hiesmayr, a theoretical physicist at the University of Vienna, and her colleagues, a team of quantum information theory specialists, particle physicists and nuclear physicists, have been published in EPJC.