Scientific Highlights
Making sense of the muon’s misdemeanours
An exotic atom called muonium could explain why muons won’t stick to the rules, believe researchers using the Swiss Muon Source at Paul Scherrer Institute PSI.
Upgraded pixel detector back in action at CERN
Built at Paul Scherrer Institute, the detector forms the heart of the CMS experiment. It is producing data again following an upgrade during the LHC shutdown.
The Running Bottom Quark Mass and the Higgs Boson
We present a new measurement of the bottom quark mass in the MS scheme at the renormalization scale of the Higgs boson mass from measurements of Higgs boson decay rates at the LHC: mb (mH) = 2.6 +0.36-0.31 GeV. The measurement has a negligible theory uncertainty and excellent prospects to improve at the HL-LHC and a future Higgs factory.
Higgs-boson pair production at LHC: reliable theoretical uncertainties
Researchers at PSI have refined the theoretical prediction for the pair production of Higgs bosons at the LHC and re-analized the related uncertainties resulting in sizable contributions neglected before. This process will be highly relevant at the high-luminosity run of the LHC to measure the Higgs potential directly.
Size of helium nucleus measured more precisely than ever before
In experiments at the Paul Scherrer Institute PSI, an international research collaboration has measured the radius of the atomic nucleus of helium five times more precisely than ever before. The researchers are publishing their results today in the journal Nature.
Demonstration of Muon-Beam Transverse Phase-Space Compression
We demonstrate efficient transverse compression of a 12.5 MeV=c muon beam stopped in a helium gas target featuring a vertical density gradient and crossed electric and magnetic fields. The muon stop distribution extending vertically over 14 mm was reduced to a 0.25 mm size (rms) within 3.5 μs. The simulation including cross sections ...
Global Fit to Modified Neutrino Couplings and the Cabibbo-Angle Anomaly
Recently, discrepancies of up to 4σ between the different determinations of the Cabibbo angle were observed. In this context, we point out that this “Cabibbo-angle anomaly” can be explained by lepton flavor universality violating new physics in the neutrino sector. However, modified neutrino couplings to standard model gauge bosons also affect many other observables sensitive to lepton flavor universality violation, which have to be taken into account in order to assess the viability of this explanation.
Measurement of properties of Bs0 → μ+μ− decays and search for B0 → μ+μ− with the CMS experiment
Results are reported for the B0s → μ+μ− branching fraction and effective lifetime and from a search for the decay B0 → μ+μ−. The analysis uses a data sample of proton-proton collisions accumulated by the CMS experiment in 2011, 2012, and 2016, with center-of-mass energies (integrated luminosities) of 7TeV (5fb−1), 8TeV (20fb−1),and 13TeV (36fb−1).
Detailed polarization measurements of the prompt emission of five gamma-ray bursts
Gamma-ray bursts (GRBs) are the strongest explosions in the Universe since the Big Bang. They are believed to be produced either in the formation of black holes at the end of massive star evolution or the merging of compact objects.