Data from 'old' experiment appears to constrain the idea of dark photons as part of dark matter theory

October 27, 2014 by Bob Yirka report
Layout of the E137 experiment. Credit: Phys. Rev. Lett. 113, 171802

(Phys.org) —A trio of physicists is suggesting in a paper they've published in Physical Review Letters, that results from an experiment run in the early 1980's places constraints on the idea of a dark photon in theories that attempt to explain the nature of dark matter. Brian Batell, Rouven Essig and Ze'ev Surujon note that a proposal already exists to construct a relatively inexpensive experiment that could be used to test the basic idea to either offer support or dispel the notion altogether.

Dark matter is, of course, the mysterious stuff that believe possesses gravity that holds the universe together—without it, everything would fly apart. Unfortunately, no one has really been able to find observable evidence of its existence. Current theories suggest that dark matter is made of weakly interacting massive particles (WIMPs) which are only able to interact via the . Physicists have set up facilities around the world with the aim of observing a WIMP pinging off atomic nuclei, but have thus far failed in their efforts.

Meanwhile, other ideas have begun to be tossed around by physicists, such as the concept of a particle called χ—if it exists, it would interact with others like it, the thinking goes, via a force akin to electromagnetism—that force, they believe could be conveyed by a photon analog, the dark photon. If such dark photons do exist, the theory continues, they would also likely interact with other "normal" matter, which should be observable. That's where data from an old experiment comes in.

From 1980 to 1982, researchers at SLAC National Accelerator Laboratory in Menlo Park were conducting "beam dump" experiments—ramming high energy electrons into an aluminum target and watching to see what could come through both the target and a sand-hill behind it. Batell, et al believe that high energy χs should have come through as well interacting (via dark photons) with at least some of the electrons. But the researchers conducting the beam dumps reported no recoiling electrons, which suggests that if there were dark photons present, there should be some limits regarding its properties.

The old experiments don't disprove the whole idea of χs or dark photons, but instead suggest that the theory that surrounds them needs to be more deeply thought out to better describe what their actual properties might be. To that end, other physicists have already proposed putting together a new, relatively inexpensive, beam dump experiment called BDX that would allow for 100 times as many events as the ones conducted in the 80's, hopefully offering a glimpse of observable proof of the existence of χs, dark photons and perhaps itself.

Explore further: China's PandaX WIMP detector set to begin operations soon

More information: Strong Constraints on Sub-GeV Dark Sectors from SLAC Beam Dump E137, Phys. Rev. Lett. 113, 171802 – Published 21 October 2014. dx.doi.org/10.1103/PhysRevLett.113.171802 . On Arxiv: arxiv.org/abs/1406.2698

ABSTRACT
We present new constraints on sub-GeV dark matter and dark photons from the electron beam-dump experiment E137 conducted at SLAC in 1980–1982. Dark matter interacting with electrons (e.g., via a dark photon) could have been produced in the electron-target collisions and scattered off electrons in the E137 detector, producing the striking, zero-background signature of a high-energy electromagnetic shower that points back to the beam dump. E137 probes new and significant ranges of parameter space and constrains the well-motivated possibility that dark photons that decay to light dark-sector particles can explain the ∼3.6σ discrepancy between the measured and standard model value of the muon anomalous magnetic moment. It also restricts the parameter space in which the relic density of dark matter in these models is obtained from thermal freeze-out. E137 also convincingly demonstrates that (cosmic) backgrounds can be controlled and thus serves as a powerful proof of principle for future beam-dump searches for sub-GeV dark-sector particles scattering off electrons in the detector.

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12 comments

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indio007
1.7 / 5 (6) Oct 27, 2014
We are now officially in Bizarro world. Seriously now, dark photons?
altizar
1.6 / 5 (10) Oct 27, 2014
Seriously, Dark Matter is nothing more than the collapse of the space-time continuum in the absence of matter. This collapse resembles a gravity well, thus the reason it seems to be a gravity effect. And the reason we can't observe it is that when matter is present the collapse won't occur. . .
mbee1
1.4 / 5 (8) Oct 27, 2014
If it does not work the first or 100th time invent a new particle to stay in business. The simplest explanation for the observed rotation rate of galaxies is electromagnetic fields in the plasma which is in those galaxies holding them together. The rotation rate seems to exceed the amount which gravity by itself would hold the galaxies together hence when one does not know the actual amount of matter you invent dark matter as plasma physics is not currently PC. If you wanted to see if these guys and gals were serious have them come up with their own money to prove or disprove the theories otherwise they are simply people with their hand out wanting a welfare check.
tritace
Oct 27, 2014
This comment has been removed by a moderator.
tritace
Oct 27, 2014
This comment has been removed by a moderator.
Captain Stumpy
3.8 / 5 (10) Oct 27, 2014
The AWT faces this conceptual problem
@ZEPHIR/tritace
the aw/daw (not a theory, simply a debunked pseudoscience) faces this problem with a fallacious premiss which has been proven wrong by science and the following publications:
http://exphy.uni-...2009.pdf
and
http://arxiv.org/...1284.pdf

please note that the paper published in the Physical Review Letters pushes this knowledge to the 10^-17 level, which is orders of magnitude above the proof you have given for aw/daw

which is none, by the way

your continual insistence in aw/daw is a faith supported by no evidence
whereas science directly proves it all wrong with the above links

you are trolling and baiting with spam and known pseudoscience
tritace
Oct 27, 2014
This comment has been removed by a moderator.
axemaster
4.2 / 5 (10) Oct 27, 2014
Funny to watch all the commenters derping along. The reality? There's no reason that particles like this shouldn't exist, so it's very much worthwhile to search for them.

Even when we get a GUT (grand unified theory), it'll likely just be a description of a class of possible universes, of which our own is just a subunit. So even with a proven GUT, experiments like this will still have value, to help us narrow the set of universes that ours could belong to.
tritace
Oct 27, 2014
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mikecandance
1.7 / 5 (6) Oct 27, 2014
When I read the comment sections on matters like this, it's all too obvious that most people do not really follow physics closely and over a long period of time.

If I had to make an off the wall guess, I would say that during the Big Bang, either a fourth spatial dimension was created, or fragmented pockets were. During that scenario, matter was trapped and today we see that as Dark Matter.

What the truth is will depend on actually finding and confirming the existence of a particular class of particles. Since physics is not complete, it may be that there is a field that does not spread out over all of space, but collects in gravitational areas and interacts in a manner that creates an external gravitational area that supports larger masses.

Up next: did they bring any cheese back from the moon?
Benni
1 / 5 (5) Oct 27, 2014
Reverse engineering in modern science is funny.

.....better tagged as "funny farm science", alias "perpetual motion" and other such closely related gimmickry.
liquidspacetime
1 / 5 (2) Oct 29, 2014
Aether has mass. Aether physically occupies three dimensional space. Aether is physically displaced by the particles of matter which exist in it and move through it.

The Milky Way's halo is not a clump of stuff anchored to the Milky Way. The Milky Way is moving through and displacing the aether.

The Milky Way's halo is the state of displacement of the aether.

The Milky Way's halo is the deformation of spacetime.

A moving particle has an associated aether displacement wave. In a double slit experiment the particle travels through a single slit and the associated wave in the aether passes through both.

What ripples when galaxy clusters collide is what waves in a double slit experiment; the aether.

Einstein's gravitational wave is de Broglie's wave of wave-particle duality; both are waves in the aether.

Aether displaced by matter relates general relativity and quantum mechanics.

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