Neutrino trident production may offer powerful probe of new physics

September 15, 2014 by Lisa Zyga feature
Parameter space for the Z’ gauge boson. The light gray area is excluded at 95% C.L. by the CCFR measurement of the neutrino trident cross section. The dark gray region with the dotted contour is excluded by measurements of the SM Z boson decay to four leptons at the LHC. The purple region is the area favored by the muon g-2 discrepancy that has not yet been ruled out, but future high-energy neutrino experiments are expected to be highly sensitive to this low-mass region. Credit: Altmannshofer, et al. ©2014 American Physical Society

(Phys.org) —The standard model (SM) of particle physics has four types of force carrier particles: photons, W and Z bosons, and gluons. But recently there has been renewed interest in the question of whether there might exist a new force, which, if confirmed, would result in an extension of the SM. Theoretically, the new force would be carried by a new gauge boson called Z' or the "dark photon" because this "dark force" would be difficult to detect, as it would affect only neutrinos and unstable leptons.

"Much of the complexity and beauty of our physical world depends on only four forces," Wolfgang Altmannshofer, a researcher at the Perimeter Institute for Theoretical Physics in Waterloo, Ontario, told Phys.org. "It stands to reason that any additional new discovered will bring with it interesting and unexpected phenomena, although it might take some time to fully appreciate and understand its implications."

Now in a new study published in Physical Review Letters, Altmannshofer and his coauthors from the Perimeter Institute have shown that the parameter space where a new dark force would exist is significantly restricted by a rare process called neutrino trident production, which has only been experimentally observed twice.

In neutrino trident production, a pair of muons is produced from the scattering of a muon neutrino off a heavy atomic nucleus. If the new Z' boson exists, it would increase the rate of neutrino trident production by inducing additional particle interactions that would constructively interfere with the expected SM contribution.

The new force could also solve a long-standing discrepancy in the muon g-2 experiment compared to the SM prediction. By coupling to muons, the new force might solve this problem.

However, the two existing experimental results of neutrino trident production (performed by the CHARM-II collaboration and the CCFR collaboration) are both in good agreement with SM predictions, which places strong constraints on any possible contributions from a new force.

In the new paper, the physicists have analyzed the two experimental results and extended the support for ruling out a dark force, at least over a large portion of the parameter space relevant to solving the muon g-2 discrepancy (when the mass of the Z' boson is greater than about 400 MeV). The results not only constrain the dark force, but more generally any new force that couples to both muons and muon neutrinos.

"We showed that neutrino trident production is the most sensitive probe of a certain type of new force," Altmannshofer said. "Particle physics is driven by the desire to discover new building blocks of nature, and ultimately the principles that organize these building blocks. Our findings establish a new direction where new forces can be searched for, and highlight the planned neutrino facility at Fermilab (the Long-Baseline Neutrino Experiment [LBNE]) as a potentially powerful experiment where such forces can be searched for in the future."

Overall, the current results suggest that LBNE would have very favorable prospects for searching for the Z' boson in the relevant, though restricted, regions of parameter space.

Explore further: New results confirm standard neutrino theory

More information: Wolfgang Altmannshofer, et al. "Neutrino Trident Production: A Powerful Probe of New Physics with Neutrino Beams." PRL 113, 091801 (2014). DOI: 10.1103/PhysRevLett.113.091801

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15 comments

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markinsanfran
2.3 / 5 (3) Sep 15, 2014
The standard model (SM) of particle physics has four types of force carrier particles: photons, W and Z bosons, and gluons. This is incorrect. It is actually photons, W/Z bosons, gluons, and Higgs particles. Just so you know...
Aligo
Sep 15, 2014
This comment has been removed by a moderator.
Aligo
Sep 15, 2014
This comment has been removed by a moderator.
Aligo
Sep 15, 2014
This comment has been removed by a moderator.
Aligo
Sep 15, 2014
This comment has been removed by a moderator.
arom
1 / 5 (8) Sep 15, 2014
—The standard model (SM) of particle physics has four types of force carrier particles: photons, W and Z bosons, and gluons. But recently there has been renewed interest in the question of whether there might exist a new force, which, if confirmed, would result in an extension of the SM. Theoretically, the new force would be carried by a new gauge boson called Z' or the "dark photon" because this "dark force" would be difficult to detect, as it would affect only neutrinos and unstable leptons.

"Much of the complexity and beauty of our physical world depends on only four forces," Wolfgang Altmannshofer, a researcher at the Perimeter Institute for Theoretical Physics in Waterloo, Ontario, told Phys.org. "It stands to reason that any additional new force discovered will bring with it interesting and unexpected phenomena, although it might take some time to fully appreciate and understand its implications."


Unfortunately according to the standard model (in which the main theme is mathematic supporting by experiment), it is quite difficult for general people to visualize how our physical world was built; not even to grasp what the four types of force (including the new dark force )look like. Maybe this simple idea could help ….
http://www.vacuum...=9〈=en
shavera
3 / 5 (4) Sep 16, 2014
The standard model (SM) of particle physics has four types of force carrier particles: photons, W and Z bosons, and gluons. This is incorrect. It is actually photons, W/Z bosons, gluons, and Higgs particles. Just so you know...


Actually, while the Higgs Boson is a... boson, it's not a "force carrier" in the traditional sense of the term. It's just a Bosonic particle within our standard model.
Da Schneib
2.3 / 5 (3) Sep 16, 2014
The standard model (SM) of particle physics has four types of force carrier particles: photons, W and Z bosons, and gluons.
Be very, very careful, because this could be confused with the four forces of nature, gravity, weak, electromagnetic, and strong/color. The graviton, however, is not part of the SM, because GRT cannot be reconciled (so far) with the SM. It is therefore (so far) impossible to make a GUT. So while technically accurate, this has the potential to be misleading.
Da Schneib
1 / 5 (2) Sep 16, 2014
The standard model (SM) of particle physics has four types of force carrier particles: photons, W and Z bosons, and gluons.
This is incorrect. It is actually photons, W/Z bosons, gluons, and Higgs particles. Just so you know...
What is the force carried by the Higgs?
Aligo
Sep 16, 2014
This comment has been removed by a moderator.
Da Schneib
1 / 5 (1) Sep 16, 2014
Got a source for that, please? I don't know what "shielding force" means. Also, where does the "extra mass" for hadrons come from, and what is it? And why is it "extra?"
Da Schneib
1 / 5 (1) Sep 16, 2014
For example, here is an article on the proton, and at the end it discusses mass and says:

the up quark's mass is about 2.4 MeV (mega-electron volts; particle physicists measure mass in MeV/c2), and the down's about 4.8 MeV. Gluons, like photons, are massless, so the proton should have a mass of about 9.6 MeV (= 2 x 2.4 + 4.8), right? But it is, in fact, 938 MeV! QCD accounts for this enormous difference by the energy of the QCD vacuum inside the proton; basically, the self-energy of ceaseless interactions of quarks and gluons.
So you see, the mass of the lightest baryon, the proton, is all accounted for, and in fact so are the masses of the heavier baryons, and all of the mesons, by Quantum Chromodynamics (QCD).
Osiris1
1 / 5 (2) Sep 21, 2014
We are gonna find more than one 'new' fundamental force! Chances are that there are up to eleven, the number of dimensions postulated in that so called 'standard model'. Not only that, we are gonna find that the 'standard model' is actually three dimensional! We will also find that time is also three dimensional as well. That is why the 'kill yer ancestor paradox' is really a red herring covering a huge hoax. We might even find fundamental forces associated with time dimensions. The only rule in time travel is that we cannot backtrack on our own dtx,dty,dtz time vector skew line in temporal space. In truth there are an infinity of time vectors of the form T(x),T(y),T(z) Like Einstein said, the universe is not only stranger than we think, but also stranger than we can imagine!
Da Schneib
1 / 5 (1) Sep 21, 2014
Actually, we already have four forces that use ten dimensions. Another one would presumably use another five dimensions, giving sixteen (including the extra one that connects the string theories together into M-theory). So, no, I doubt it.

For the record, EM uses one, weak uses two, and that's three, strong uses three and that's six, and gravity uses four and that's ten, plus one to connect the theories together is eleven. Since we already have forces that use one, two, three, and four dimensions, any new force would presumably use five.
Da Schneib
not rated yet Sep 21, 2014
Like Einstein said, the universe is not only stranger than we think, but also stranger than we can imagine!
That was J. B. S. Haldane.

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