sciencehabit quotes a report from Science Magazine: For decades, particle physicists have yearned for physics beyond their tried-and-true standard model. Now, they are finding signs of something unexpected at the Large Hadron Collider (LHC), the world’s biggest atom smasher at CERN, the European particle physics laboratory near Geneva, Switzerland. The hints come not from the LHC’s two large detectors, which have yielded no new particles since they bagged the last missing piece of the standard model, the Higgs boson, in 2012, but from a smaller detector, called LHCb, that precisely measures the decays of familiar particles. The latest signal involves deviations in the decays of particles called B mesons — weak evidence on its own. But together with other hints, it could point to new particles lying on the high-energy horizon. “This has never happened before, to observe a set of coherent deviations that could be explained in a very economical way with one single new physics contribution,” says Joaquim Matias, a theorist at the Autonomous University of Barcelona in Spain. B mesons are made of fundamental particles called quarks. Familiar protons and neutrons are made of two flavors of quarks, up and down, bound in trios. Heavier quark flavors — charm, strange, top, and bottom — can be created, along with their antimatter counterparts, in high-energy particle collisions; they pair with antiquarks to form mesons. In their latest result, reported today in a talk at CERN, LHCb physicists find that when one type of B meson decays into a K meson, its byproducts are skewed: The decay produces a muon (a cousin of the electron) and an antimuon less often than it makes an electron and a positron. In the standard model, those rates should be equal, says Guy Wilkinson, a physicist at the University of Oxford in the United Kingdom and spokesperson for the 770-member LHCb team. The new data suggest the bottom quark might morph directly into a strange quark — a change the standard model forbids — by spitting out a new particle called a Z9 boson. That hypothetical cousin of the Z boson would be the first particle beyond the standard model and would add a new force to theory. The extra decay process would lower production of muons, explaining the anomaly.
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