A New Particle (Fifth Force) Found ?

[Rade]

OK, who wants to take a stab to explain these recent findings, just this week posted on arxix.org ? It has been suggested that the results of this experiment, if confirmed, will not only mean the Higgs Boson does not exist, but also the Standard Model of particle physics would be experimentally falsified as a valid theory. From what I can gather, the results of this experiment suggest a new fifth force of nature is at work within the nucleus of atoms.

 

http://arxiv.org/abs/1104.0699

 

See also less formal stories:

 

http://www.technewsworld.com/story/Tevatron-Experiment-Could-Send-Particle-Physicists-Back-to-the-Drawing-Board-72231.html?wlc=1302364109

 

http://www.livescience.com/13631-subatomic-particle-physics.html

 

http://www.chron.com/disp/story.mpl/chronicle/7512164.html

[CraigD]

These results are as yet unreplicated, and involve some very complicated devices and analysis, so I agree with their authors and many commentators that it’s premature to begin serious work on a theoretical explanation. Even if replicated by other detectors (eg: the current Tevetron’s D0 detector, and the LHC’s), a lot of data is going to be needed on which to base such work.

 

As some commentators have noted, highly significant off-prediction results have been found in the past, and upon attempted replication and reanalysis, found to be instrument, analysis, or statistical relics, so guarded caution is wise. To my inexpert eye, that 2 points on the graphs in addition to the 150 GeV on page five of Invariant Mass Distribution... one prompting the excitement at 150 GeV, at around 90 and 100 GeV, are significantly off prediction, furthers my impression that these data and results are still a rough.

 

Due caution stated, these are some exciting results! and it’s not too early for we of the science enthusiast peanut gallery to begin throwing around ideas and observations.

 

My first is a question of someone who better understands this physics than me: why is the apparent 150 MeV particle not being considered as a possible massive Higgs boson? Everything about it seems to my inexpert reading to be within the ranges predicted for the Higgs.

 

It has been suggested that the results of this experiment, if confirmed, will not only mean the Higgs Boson does not exist ...

I didn’t get that from reading the previous links. Even if there’s a particle unpredicted by the SM, there are still the usual well-confirmed predicted particles, and no reason I can see to discard the various predictions for the massive Higgs. The Higgs mechanism is still a tremendously attractive theory.

 

Can you point me to where you're getting this from, Rade, or explain your original thinking in more detail?

 

... but also the Standard Model of particle physics would be experimentally falsified as a valid theory.

I think confirmation of a new particle wouldn’t invalidate the SM, only show it to be incomplete. As it’s already glaringly incomplete in failing to prediction a particle for the gravitational force (or, to the best of my knowledge, a theory in which gravity is carried by the Higgs particles, an idea I suspect may be right), this wouldn’t be a first blemish in the SM.

 

I think that many non-specialists (I know I did) fail to appreciate how empirical the SM is, and thus how incomplete and flexible it is. Compared to hard classical theories like relativity, which predicts only a few kinds of phenomena (non of them requiring quantum physics to be physically real), and really would be falsified by a significant, replicated observed failure of its predictions on a macroscopic scale, the SM seems to me something midway between theory and mere law – and like physical laws unexplained (or unsatisfactorily explained) by theory (eg: gravity), how resilient and long-lasting its likely to be.

[Erasmus00]

Consider- a 3[imath]\sigma[/imath] event has about an order of 1/100 probability of being a fluctuation of background events. How many analyses do you think they run at the Tevatron? Odds are that with more data, this goes away, sadly. Even if found, standard model extensions that have been discussed since the 70s seem to fit the data just fine.

 

My first is a question of someone who better understands this physics than me: why is the apparent 150 MeV particle not being considered as a possible massive Higgs boson? Everything about it seems to my inexpert reading to be within the ranges predicted for the Higgs.

 

Mostly, its that the cross-section of a standard higgs is something like 12 femto-barns, while the observed cross-section is something like 4 pico-barns. It also didn't show up strongly in studies of bottom jets, to which a standard model higgs would couple preferentially.

 

The Higgs mechanism is still a tremendously attractive theory.

 

The Higgs mechanism is attractive in its generality- every theory in some limit has something that resembles a Higgs boson, with small details.

 

As it’s already glaringly incomplete in failing to prediction a particle for the gravitational force (or, to the best of my knowledge, a theory in which gravity is carried by the Higgs particles, an idea I suspect may be right), this wouldn’t be a first blemish in the SM.

 

Its important to remember that gravity has an effect on all energy- even particles with no rest-mass can be bent by gravity (think photons and a black hole). The Higgs, by its nature, only knows about particles that have rest-mass, and so if it were responsible for gravity, photons wouldn't bend in gravitational wells.

 

Also, for technical reasons, gravitons would have to be spin 2 particles.

 

I think that many non-specialists (I know I did) fail to appreciate how empirical the SM is, and thus how incomplete and flexible it is. Compared to hard classical theories like relativity, which predicts only a few kinds of phenomena (non of them requiring quantum physics to be physically real), and really would be falsified by a significant, replicated observed failure of its predictions on a macroscopic scale, the SM seems to me something midway between theory and mere law – and like physical laws unexplained (or unsatisfactorily explained) by theory (eg: gravity), how resilient and long-lasting its likely to be.

 

The standard model is a catalogue of particles and symmetry groups (which can loosely be thought of as forces). Its an empirical theory, there is no way to predict apriori whether or not another generation of particles exist, or something similar. Think of classical mechanics- its not-predictive until you specify the masses you are working with and the force laws between them. Newtonian gravity has an empirical force law, and the masses of the planets are determined empirically. Even using general relativity to do cosmology involves going out and measuring the matter content of the universe (with telescopes).

 

The framework of the standard model is quantum field theory. This specifies the "rules of the game" in the same way classical mechanics specifies the rules for classical systems. The standard model itself is the collection of particles and symmetries, which are analogous to the force laws and particle content in classical mechanics.

 

The bump in question would be adding something new to the particle catalogue. It would not indicate a problem with the underlying framework. Not finding any Higgs at all WOULD indicate a problem with the underlying framework.

[Rade]

I didn’t get that from reading the previous links. Even if there’s a particle unpredicted by the SM, there are still the usual well-confirmed predicted particles, and no reason I can see to discard the various predictions for the massive Higgs. The Higgs mechanism is still a tremendously attractive theory. Can you point me to where you're getting this from, Rade, or explain your original thinking in more detail?

I have read many other secondary internet posts, I most likely spoke incorrectly. You are correct, we need to wait for more experiments (to reach the 5-sigma level of statistical confidence).

 

But, it is good for this forum to discuss the different possibilities for "future events". Also, I think it good to brainstorm the possibility that the new particle is confirmed (it meets the 5-sigma criterion), what then ? What would be the form of the new physics that must result within framework of quantum field theory ? What would a possible new fifth force within protons and antiprotons mean, how would it be explained by quantum field theory ?

 

Concerning the Higgs, Here are the various logical possibilities, the first two of which lead to a new physics:

 

1. The "new particle" is confirmed, and the Higgs Boson is confirmed at CERN (here the Standard Model is modified )

 

2. The "new particle" is confirmed, and CERN cannot find Higgs (here I think the Standard Model is replaced over time ?)

 

3. The "new particle" is not confirmed, and CERN confirms Higgs (Standard Model complete)

 

4. The "new particle" is not confirmed, and Higgs is not confirmed at CERN (where we exist today, incomplete Standard Model)

 

Please see this "blog" about why the "new particle" cannot be the Higgs Boson. The blogger appears to have understanding of nuclear physics (ps--I see the answer also provided by Erasmus00):

http://blogs.uslhc.us/a-hint-of-something-new-in-wdijets-at-cdf?utm_source=twitterfeed&utm_medium=twitter