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Mounting evidence for a 95 GeV Higgs boson

88 points by kloch 5y ago

ncmncm 5y ago
Does this mean Higgs particles might be more complicated than we thought? Or, there is more than one?
- gus_massa 5y ago
  Only one Higgs Boson is the simplest model, and we have not measured a second one yet. There are a lot of alternatives that involve more Higgs Bosons https://en.wikipedia.org/wiki/Higgs_boson#Alternative_models https://en.wikipedia.org/wiki/Higgs_boson#Alternative_models and the models have some internal parameters to adjust, but it's very difficult to guess which one is the correct (or if the correct one is the simplest one) until more Higgs bosons are discovered (or someone has an extraordinary brilliant idea).
gus_massa 5y ago
This is theoretical preprint that reinterpret some previous experimental results. The fine technical details are well over my head, but I hope this is accurate enough. There is a very strong experimental support for the "old" Higgs Boson discovered in 2012 that has a mass of 125Gev, and there is some recent weak experimental support for another "new" Higgs Boson with a mass of 95GeV. (For comparison, the mass of a proton is ~0.9GeV.) In this preprint, they propose that there is a family of tree Higgs Bosons. The "old" one, the "new" one and a third one yet to be detected. The structure of the family forces some of the properties of the bosons and how they interact with the other particles. The hard part is tweaking the properties of the family of Higgs Bosons so they predict the results of the experiments where the 125GeV and 95GeV are seen, but they don't cause weird results in all the other thousands of experiments where the Higgs Bosons have a negligible effect.
- progrus 5y ago
  > The hard part is tweaking the properties of the family of Higgs Bosons so they predict the results of the experiments where the 125GeV and 95GeV are seen, but they don't cause weird results in all the other thousands of experiments where the Higgs Bosons have a negligible effect. These don’t sound like “risky predictions” at all! We already know everything that the model should output? Popper is spinning in his grave. And a real theoretical physicist would have been able to tell you “95GeV” before seeing it.
  - gus_massa 5y ago
    I agree that "predictions" is not the right word. It's easy to explain the problem looking at the Figure 7 of the preprint. The fist graph shows how many times an experiment produced a pair of photons. The x axis is the energy of the photons, and the y axis is the number of events (I'm not sure about the scale here). The dashed line is the theoretical result without the second boson IIUC. The green zone is the range of a difference of ±σ. The yellow zone is the range of a difference of ±2σ. The continuous line is the experimental data. As expected, the experimental data is close to the theoretical result, but it is not exactly equal. It moves most of the time in the green zone of ±σ. Sometimes it moves in the yellow zone of green zone is the range of a difference of ±2σ. The interesting part is that in some parts it goes outside the yellow some. For those energies the theoretical model is too different of the experimental data. Back to your objection, the idea in the paper is to make a model with a few parameters, and then optimize the parameters until the curve of the new model fits the experimental data as much as possible. It's not enough to say 95GeV, the model has more parameters and also they must verify that the new model modifies the range of energies where the difference is big, but does not modify too much the other ranges.
    - progrus 5y ago
      Well also, in my partly-serious physics trolling I left out that maybe the model could then predict a value for the next in the Higgs family (if such a thing exists), which according to my limited understanding doesn’t seem impossible.
- sideshowb 5y ago
  Thanks for the summary! I wonder if you could eli5: I thought the Higgs was what gave other particles mass? How can it be heavier than the particles it gives mass to?
  - harshreality 5y ago
    It's the Higgs field that gives particles mass. https://www.britannica.com/video/185531/explanation-field-Higgs-particles-mass https://www.britannica.com/video/185531/explanation-field-Hi...
    - felipellrocha 5y ago
      Oh, sure, sure. What is the field?
      - ajkjk 5y ago
        It is just one of the fields. The one whose interactions give particles mass. Modern physics has been working on finding and naming all of them.
        ericbarrett 5y ago
        It gives some particles some mass. I had to look it up, because I'm no physicist, but e.g. most of a proton's mass comes from the strong force binding energy of its quarks.
        ajkjk 5y ago
        That's true. I should have specified, fundamental particles. Although we're not sure about neutrinos.
  - gus_massa 5y ago
    > I thought the Higgs was what gave other particles mass? Sorta yes, but it's more complicated. > How can it be heavier than the particles it gives mass to? There are a few bad explanations about the Higgs boson floating around. I hate all of them. I wish I can write a good one, but it's very difficult task. One of the explanations is the "prime minister" analogy, that says that the usual particles are like a prime minister, and the Higgs bosons are like the press reporters that follow the prime minister around. So even if the prime minister has no mass, the big bundle of the prime minister and the journalist has mass. In this explanation it's difficult to imagine why the mass of the bundle is smaller than the mass of each journalist. [Did I already said that I hate this explanation?] Oversimplifying toooo much: The idea is that the usual particles have something that look like mass because they bounce against the Higgs boson. They don't absorb the Higgs boson. They are not surrounded by Higgs bosons. They just bounce against a Higgs boson from time to time, and that somehow cause that they look like particles with mass. It's weird, very weird. The analogy does not give an intuitive explanation, but this can be formalized and the equations model the experiment accurately. But actually, the usual particles are not bouncing against Higgs boson, they are bouncing against the non-zero vacuum expectation value Higgs field. What is the Higgs field? What is the vacuum expectation value? Why it is not zero like in most fields? Those are hard questions! I watched the video in Encyclopædia Britannica linked in the sibling comment, and it's quite good. I hope it makes thing more clear than my explanation.
frob 5y ago
Everything here is at or below 3-sigma confidence, and it's not even clear if that's a local search confidence (i.e. when you know the mass to within a small %) or a global search (where you don't know the mass and are just looking all over the place for an excess which inherently makes it more likely you find SOMETHING which makes your confidence lower). The world of particle physics is littered with the graves of 3-sigma excesses. At this point, there is basically nothing to see here. You will do yourself a favor by just moving along.
- jessriedel 5y ago
  Multiple 3-sigma excesses explained by the same model are potentially much more significant from a Bayesian perspective than several unrelated 3-sigma excesses.
  - exmadscientist 5y ago
    That's very true, but the candidate LEP signal is pretty weak, given that they were explicitly on the hunt for this exact sort of thing. I agree with the parent poster: move along (unless you're directly working on this!), and then get happy news later if something interesting does emerge. Just don't wait up for it.
    - jessriedel 5y ago
      > the candidate LEP signal is pretty weak, given that they were explicitly on the hunt for this exact sort of thing. Isn't the fact that they were explicitly hunting for it a reason to take it more seriously? In contrast, if this signal was discovered after trawling the huge dataset for a hundred possible hypotheses, that would be a reason to discount it, Bayes-wise.
aortega 5y ago
I never understood how such an energetic particle (The Higgs Boson has 50 times more energy than an ultrafast neutron) can naturally regulate a field that permeates all the universe without destroying everything.
- jessriedel 5y ago
  In some sense that's the cosmological constant problem and it applies to all particles, not just the Higgs. If a field with zero excitations were to weigh something (more specifically, have a positive energy density) on the scale of its single-excitation mass, it would be larger than the observed energy density of the universe by dozens of orders of magnitude, even if you're just talking about the extremely light neutrinos. But in fact, zero excitations looks to weigh zero...or 10^-60 - 10^-120 https://en.wikipedia.org/wiki/Cosmological_constant_problem https://en.wikipedia.org/wiki/Cosmological_constant_problem
- ajkjk 5y ago
  The particle is just what a quantization of the field looks like. Any particular interaction involves many minute probabilities of it existing. It's a lot like: two atoms can always exchange a low-energy photon, say, and move an electron between orbitals... but they could also exchange a _super high energy photon_ instead. It's just very highly unlikely. Nevertheless the fact that they can do that contributes to the physics, at least a little bit. But that virtual high energy photon (which shows up in the Feynman diagrams) isn't destroying anything either, for the same reason the Higgs isn't.
Thorentis 5y ago
The more I read about quantum mechanics, the more I'm convinced that we have no idea what we're talking about.
higgshunter 5y ago
The main point of the paper is that now the third experimental excess in data appeared at more or less the same mass, 95 GeV. Obviously one 3 sigma excess should not excite you too much. But three excesses (two at ~3 sigma, one at ~2 sigma) looks more interesting.

88 points by kloch 5y ago

ncmncm 5y ago

Does this mean Higgs particles might be more complicated than we thought? Or, there is more than one?

gus_massa 5y ago
Only one Higgs Boson is the simplest model, and we have not measured a second one yet. There are a lot of alternatives that involve more Higgs Bosons https://en.wikipedia.org/wiki/Higgs_boson#Alternative_models https://en.wikipedia.org/wiki/Higgs_boson#Alternative_models and the models have some internal parameters to adjust, but it's very difficult to guess which one is the correct (or if the correct one is the simplest one) until more Higgs bosons are discovered (or someone has an extraordinary brilliant idea).

gus_massa 5y ago

This is theoretical preprint that reinterpret some previous experimental results. The fine technical details are well over my head, but I hope this is accurate enough. There is a very strong experimental support for the "old" Higgs Boson discovered in 2012 that has a mass of 125Gev, and there is some recent weak experimental support for another "new" Higgs Boson with a mass of 95GeV. (For comparison, the mass of a proton is ~0.9GeV.) In this preprint, they propose that there is a family of tree Higgs Bosons. The "old" one, the "new" one and a third one yet to be detected. The structure of the family forces some of the properties of the bosons and how they interact with the other particles. The hard part is tweaking the properties of the family of Higgs Bosons so they predict the results of the experiments where the 125GeV and 95GeV are seen, but they don't cause weird results in all the other thousands of experiments where the Higgs Bosons have a negligible effect.

progrus 5y ago
> The hard part is tweaking the properties of the family of Higgs Bosons so they predict the results of the experiments where the 125GeV and 95GeV are seen, but they don't cause weird results in all the other thousands of experiments where the Higgs Bosons have a negligible effect. These don’t sound like “risky predictions” at all! We already know everything that the model should output? Popper is spinning in his grave. And a real theoretical physicist would have been able to tell you “95GeV” before seeing it.
- gus_massa 5y ago
  I agree that "predictions" is not the right word. It's easy to explain the problem looking at the Figure 7 of the preprint. The fist graph shows how many times an experiment produced a pair of photons. The x axis is the energy of the photons, and the y axis is the number of events (I'm not sure about the scale here). The dashed line is the theoretical result without the second boson IIUC. The green zone is the range of a difference of ±σ. The yellow zone is the range of a difference of ±2σ. The continuous line is the experimental data. As expected, the experimental data is close to the theoretical result, but it is not exactly equal. It moves most of the time in the green zone of ±σ. Sometimes it moves in the yellow zone of green zone is the range of a difference of ±2σ. The interesting part is that in some parts it goes outside the yellow some. For those energies the theoretical model is too different of the experimental data. Back to your objection, the idea in the paper is to make a model with a few parameters, and then optimize the parameters until the curve of the new model fits the experimental data as much as possible. It's not enough to say 95GeV, the model has more parameters and also they must verify that the new model modifies the range of energies where the difference is big, but does not modify too much the other ranges.
  - progrus 5y ago
    Well also, in my partly-serious physics trolling I left out that maybe the model could then predict a value for the next in the Higgs family (if such a thing exists), which according to my limited understanding doesn’t seem impossible.
sideshowb 5y ago
Thanks for the summary! I wonder if you could eli5: I thought the Higgs was what gave other particles mass? How can it be heavier than the particles it gives mass to?
- harshreality 5y ago
  It's the Higgs field that gives particles mass. https://www.britannica.com/video/185531/explanation-field-Higgs-particles-mass https://www.britannica.com/video/185531/explanation-field-Hi...
  - felipellrocha 5y ago
    Oh, sure, sure. What is the field?
    - ajkjk 5y ago
      It is just one of the fields. The one whose interactions give particles mass. Modern physics has been working on finding and naming all of them.
      - ericbarrett 5y ago
        It gives some particles some mass. I had to look it up, because I'm no physicist, but e.g. most of a proton's mass comes from the strong force binding energy of its quarks.
        ajkjk 5y ago
        That's true. I should have specified, fundamental particles. Although we're not sure about neutrinos.
- gus_massa 5y ago
  > I thought the Higgs was what gave other particles mass? Sorta yes, but it's more complicated. > How can it be heavier than the particles it gives mass to? There are a few bad explanations about the Higgs boson floating around. I hate all of them. I wish I can write a good one, but it's very difficult task. One of the explanations is the "prime minister" analogy, that says that the usual particles are like a prime minister, and the Higgs bosons are like the press reporters that follow the prime minister around. So even if the prime minister has no mass, the big bundle of the prime minister and the journalist has mass. In this explanation it's difficult to imagine why the mass of the bundle is smaller than the mass of each journalist. [Did I already said that I hate this explanation?] Oversimplifying toooo much: The idea is that the usual particles have something that look like mass because they bounce against the Higgs boson. They don't absorb the Higgs boson. They are not surrounded by Higgs bosons. They just bounce against a Higgs boson from time to time, and that somehow cause that they look like particles with mass. It's weird, very weird. The analogy does not give an intuitive explanation, but this can be formalized and the equations model the experiment accurately. But actually, the usual particles are not bouncing against Higgs boson, they are bouncing against the non-zero vacuum expectation value Higgs field. What is the Higgs field? What is the vacuum expectation value? Why it is not zero like in most fields? Those are hard questions! I watched the video in Encyclopædia Britannica linked in the sibling comment, and it's quite good. I hope it makes thing more clear than my explanation.

frob 5y ago

Everything here is at or below 3-sigma confidence, and it's not even clear if that's a local search confidence (i.e. when you know the mass to within a small %) or a global search (where you don't know the mass and are just looking all over the place for an excess which inherently makes it more likely you find SOMETHING which makes your confidence lower). The world of particle physics is littered with the graves of 3-sigma excesses. At this point, there is basically nothing to see here. You will do yourself a favor by just moving along.

jessriedel 5y ago
Multiple 3-sigma excesses explained by the same model are potentially much more significant from a Bayesian perspective than several unrelated 3-sigma excesses.
- exmadscientist 5y ago
  That's very true, but the candidate LEP signal is pretty weak, given that they were explicitly on the hunt for this exact sort of thing. I agree with the parent poster: move along (unless you're directly working on this!), and then get happy news later if something interesting does emerge. Just don't wait up for it.
  - jessriedel 5y ago
    > the candidate LEP signal is pretty weak, given that they were explicitly on the hunt for this exact sort of thing. Isn't the fact that they were explicitly hunting for it a reason to take it more seriously? In contrast, if this signal was discovered after trawling the huge dataset for a hundred possible hypotheses, that would be a reason to discount it, Bayes-wise.

aortega 5y ago

I never understood how such an energetic particle (The Higgs Boson has 50 times more energy than an ultrafast neutron) can naturally regulate a field that permeates all the universe without destroying everything.

jessriedel 5y ago
In some sense that's the cosmological constant problem and it applies to all particles, not just the Higgs. If a field with zero excitations were to weigh something (more specifically, have a positive energy density) on the scale of its single-excitation mass, it would be larger than the observed energy density of the universe by dozens of orders of magnitude, even if you're just talking about the extremely light neutrinos. But in fact, zero excitations looks to weigh zero...or 10^-60 - 10^-120 https://en.wikipedia.org/wiki/Cosmological_constant_problem https://en.wikipedia.org/wiki/Cosmological_constant_problem
ajkjk 5y ago
The particle is just what a quantization of the field looks like. Any particular interaction involves many minute probabilities of it existing. It's a lot like: two atoms can always exchange a low-energy photon, say, and move an electron between orbitals... but they could also exchange a _super high energy photon_ instead. It's just very highly unlikely. Nevertheless the fact that they can do that contributes to the physics, at least a little bit. But that virtual high energy photon (which shows up in the Feynman diagrams) isn't destroying anything either, for the same reason the Higgs isn't.

Thorentis 5y ago

The more I read about quantum mechanics, the more I'm convinced that we have no idea what we're talking about.

higgshunter 5y ago

The main point of the paper is that now the third experimental excess in data appeared at more or less the same mass, 95 GeV. Obviously one 3 sigma excess should not excite you too much. But three excesses (two at ~3 sigma, one at ~2 sigma) looks more interesting.