3 ms·

Why did this particle mysteriously disintegrate?

35 points by prostoalex 7y ago

sebastianconcpt 7y ago
“If confirmed, this requires physics beyond the standard model to enhance the signal. We examine various new physics interpretations of the result including these: (1) heavy new physics boosting the standard model signal, (2) [...] a new light long-lived particle, or (3) reinterpretation of the whole signal as the production of a new light long-lived particle at the fixed target,” the scientists explain in the paper. In other words, the high number of “fluke” measurements was itself a sign that something unusual was going on, and now scientists want to understand and explain why it happened. Yes, the results could be “noise,” or just interference or measurement errors. Our instruments for measuring subatomic particles are often using secondary information, like the shadow an object casts or the way it reflects light instead of the object itself. Because of the extreme tininess at play, these secondary data can be inconclusive. That’s why the next step for this research team is to try to definitively rule out noise. Researcher Kohsaku Tobioka says even this level of noise (if it’s so) would be wild. “In this case, expectation of noise is very low, so even one event or observation is very striking,” Tobioka says. “And in this case, there were four."
magicalhippo 7y ago
One response from a particle phycisist to this story can be found over at the PhysicsForums[1]. A couple of the main objections: First, I consider having theorists publishing based on preliminary experimental data bad practice and borderline unethical. The experiments say "we're not sure and we're checking this", and the theorists go full speed ahead, often putting words in the experimenters' mouths. Now, let's look at what happened. The experiment ran in 2015 and saw no events. Then the accelerator and detector made some configuration changes (hoping that they would be improvements) and got 1.5x as much data. They see 4 events, one of which they say is certainly background. They also say that the known backgrounds sum to 0,05. So just looking at background, they see 20x as much as they expect. Clearly the backgrounds are not yet under control. Declaring an observation of signal when the backgrounds are not under control would be scientifically irresponsible, which is why KOTO did not do that. [1]: https://www.physicsforums.com/threads/rare-kaon-decay-may-shed-light-on-new-physics-maybe.985147/post-6306682 https://www.physicsforums.com/threads/rare-kaon-decay-may-sh...
- empath75 7y ago
  I don’t feel like it’s unethical to write a paper along the lines of “If this is not noise, then such and such theory could explain it.” Then people could make judgements about further consequences of that theory and whether it makes more sense for the theory to be correct or for it to be noise.
dilippkumar 7y ago
The popular mechanics article was completely incomprehensible. Here's what I understood after a bunch of Wikipedia and reading the article's abstract: A pair of a quark and an antiquark combine to form an entity called a meson. If one of the pair is a strange quark (or a strange antiquark), that type of meson is called a Kaon. The standard model of physics makes predictions on how often a specific Kaon (K_L) will decay as: K_L→π0νν¯ KOTO is trying to measure this decay rate to see if it's in line with what the standard model predicts. They observed 4 such decays. 1 of them was identified as background noise. The other 3 decays are still an unexpectedly high number of decays. If there's a physicist in the room, please help verify my understanding.

35 points by prostoalex 7y ago

“If confirmed, this requires physics beyond the standard model to enhance the signal. We examine various new physics interpretations of the result including these: (1) heavy new physics boosting the standard model signal, (2) [...] a new light long-lived particle, or (3) reinterpretation of the whole signal as the production of a new light long-lived particle at the fixed target,” the scientists explain in the paper. In other words, the high number of “fluke” measurements was itself a sign that something unusual was going on, and now scientists want to understand and explain why it happened. Yes, the results could be “noise,” or just interference or measurement errors. Our instruments for measuring subatomic particles are often using secondary information, like the shadow an object casts or the way it reflects light instead of the object itself. Because of the extreme tininess at play, these secondary data can be inconclusive. That’s why the next step for this research team is to try to definitively rule out noise. Researcher Kohsaku Tobioka says even this level of noise (if it’s so) would be wild. “In this case, expectation of noise is very low, so even one event or observation is very striking,” Tobioka says. “And in this case, there were four."

magicalhippo 7y ago

One response from a particle phycisist to this story can be found over at the PhysicsForums[1]. A couple of the main objections: First, I consider having theorists publishing based on preliminary experimental data bad practice and borderline unethical. The experiments say "we're not sure and we're checking this", and the theorists go full speed ahead, often putting words in the experimenters' mouths. Now, let's look at what happened. The experiment ran in 2015 and saw no events. Then the accelerator and detector made some configuration changes (hoping that they would be improvements) and got 1.5x as much data. They see 4 events, one of which they say is certainly background. They also say that the known backgrounds sum to 0,05. So just looking at background, they see 20x as much as they expect. Clearly the backgrounds are not yet under control. Declaring an observation of signal when the backgrounds are not under control would be scientifically irresponsible, which is why KOTO did not do that. [1]: https://www.physicsforums.com/threads/rare-kaon-decay-may-shed-light-on-new-physics-maybe.985147/post-6306682 https://www.physicsforums.com/threads/rare-kaon-decay-may-sh...

empath75 7y ago
I don’t feel like it’s unethical to write a paper along the lines of “If this is not noise, then such and such theory could explain it.” Then people could make judgements about further consequences of that theory and whether it makes more sense for the theory to be correct or for it to be noise.

dilippkumar 7y ago

The popular mechanics article was completely incomprehensible. Here's what I understood after a bunch of Wikipedia and reading the article's abstract: A pair of a quark and an antiquark combine to form an entity called a meson. If one of the pair is a strange quark (or a strange antiquark), that type of meson is called a Kaon. The standard model of physics makes predictions on how often a specific Kaon (K_L) will decay as: K_L→π0νν¯ KOTO is trying to measure this decay rate to see if it's in line with what the standard model predicts. They observed 4 such decays. 1 of them was identified as background noise. The other 3 decays are still an unexpectedly high number of decays. If there's a physicist in the room, please help verify my understanding.