As we turn the page to a new year

As we close the book on 2015 we can again look back at a year of exciting science and great accomplishments by members of the Oskar Klein Centre for Cosmoparticle Physics.

As in previous years, OKCers feature very prominently in the list of the most cited astrophysics and cosmology papers led by Swedish scientists published during the year. The list was compiled by Robert Cumming in populärastronomi and appears in today’s issue.

In fact, half of top-10 2015 publications originate in our centre, starting with a Fermi collaboration search for gamma-rays from dwarf galaxies, led by Brandon Anderson. Together with a similar study led by Christian Farnier based on observations from the H.E.S.S. array (place #4), gamma-rays are used as tracers for annihilation of dark matter particles. Unfortunately, the detection of dark matter particles remain elusive but the hunt goes on, now also directly using the Xenon 1T detector.
Addressing the challenges posed by the dark sector, including both dark matter and dark energy, has become a very active area of theoretical and phenomenological research at OKC. The cosmological implications of the bimetric Hassan-Rosen theory of gravity, an alternative to Einstein’s theory of gravity including a massive graviton, has been scrutinized in a paper led by Jonas Enander. This paper came in second in citations for 2015. The other OKC contributions to the top-10 list involve two studies of SN2014J, the nearest Type Ia supernova in many decades, and an essential laboratory for our understanding of the precision reach of the use of SNe Ia as distance indicators in cosmology in our quest to understand the nature of dark energy. In one of the studies that I led together with Markus Kromer, we explored the onset of the explosion with aunique data set allowing us to probe what powers the very first moments of the optical lightcurve. In another paper, led by Peter Lundqvist and Anders Nyholm, evidence showing that both SN2014J and SN2011fe are likely the result of a merger of two white dwarfs is presented. In a short time, there has been a paradigm shift in what we think is the most common channel triggering these powerful explosions used in cosmology. These are exciting times in the field!

Just before the end of 2015, we were also intrigued by the recent developments in particle physics. The two major LHC experiments, ATLAS (with OKC participation) and CMS, presented the results from the second run of 13 TeV proton-proton collisions. Although no signal reached the magical threshold of 5 standard deviations required to claim discovery, there is an intriguing accumulation of photon-pairs of what could be hinting at a decay of a 750 GeV scalar boson. If confirmed, this would be the sign of long awaited new physics!

Looking forward to a Great New Year at the Oskar Klein Centre!

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