Friday, 18 September 2015

Friday wrap-up: diboson update, XMASS...

Wherein I list some (mostly) recent happenings, ramble a bit, and provide links, in an order roughly determined by importance and relevance to particle physics. Views are my own. Content very definitely skewed by my own leanings and by papers getting coverage, and it may not even be correct. It is a blog after all...

  • It's the season for conferences! This week we have...
    • 8th International Workshop on Top Quark Physics (TOP2015: indicotwitter). One of the interesting new results includes evidence for (>3σ) single top quark production in the s-channel with the 8 TeV dataset. There's an entertaining review of the first two days here from James Howarth.
    • Particle Astrophysics and Cosmology Including Fundamental InteraCtions (PACIFIC 2015: agenda).
    • Corfu Summer Institute: 15th Hellenic School and Workshops on Elementary Particle Physics and Gravity (programme).
  • The second is an ATLAS diboson resonance search which combines the results from the large-R dijet channel with the leptonic channels. The results are well summed up by the first Figure in the Appendix:


    In short, when interpreted as a $W'$ resonance decaying to $WZ$, they see a 3.4σ local excess in the boosted jet topology and absolutely nothing in the leptonic channels. As well, these leptonic channels were sensitive to the $W'$ interpretation of the dijet excess, so that the local significance when combined falls to 2.5σ. Taken at face value then, if the dijet excess is really new physics, it is unlikely to be as simple as $W'\to WZ$. [As an aside: I do wonder how the community's reaction would have differed if this were that paper that was published first?]. To mimic such a signal without the leptons you would need a heavy resonance decaying to two exotic particles with mass $\sim m_Z$, which then decay mostly to quarks... would be difficult to hide these low mass exotics. Or else it is something more complex that happens to pass the selection criteria for the fat jet analysis but produces very few isolated leptons. Anyway, there have been >30 extra citations to the original ATLAS paper since I made a quick literature survey seven weeks ago, and more every week. For me it seems sensible to just wait and see what the new data says (probably some time next year), happy to watch the ambulance in the distance, starting to speed up...
  • The TAUP2015 parallel session slides are now up. Indeed, as speculated last week, XMASS has a best fit modulation that is opposite in phase to that seen by DAMA/LIBRA (see Slide 10 [pdf]). It is enough evidence to exclude much of the region where the DAMA signal can be interpreted as a standard WIMP with spin-independent nucleon scattering cross-section (though this is nothing new). Interesting to see what their results will be in the fiducial volume (analysis ongoing).


  • 32 Australian institutions have signed up to the Science in Australia Gender Equity (SAGE) pilot: "Commencing in September 2015, the pilot requires participants to collect, analyse and present data on gender equity policies and practices in STEM departments, as well as identify gaps and opportunities for improvement."
  • Links without thinks:
    • Institute for Advanced Study: "Beyond the Higgs: From the LHC to China."
    • Richard Dawid wrote a guest blog on the reference frame: "What confirms a physical theory?" This should be taken in the context of that Ellis/Silk nature comment article and the ensuing debate on post-empirical science.
    • New Scientist: "Black holes may be brick walls that bounce information back out." On 't Hooft's new contribution to the black hole information paradox...
    • ... and Sabine Hossenfelder's reaction at Starts With a Bang: "Black holes and academic walls."
    • Also at Starts With a Bang: "Will The LHC Be The End Of Experimental Particle Physics?"
  • Lastly, in images from space, it is hard to top these new images of Pluto!


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