Wimp Download

[Jenifer Griffard]

Novideo or audio file from Windows that I know of uses the extension ".wimp". Not even Microsoft's Windows Media Player uses that extension; everything will be either ".WMV" or ".WMA". If you can tell us from where you got this file so we can take a look at it, we might be able to help you play it. Otherwise, you'll probably need to get more information on the format from whoever created and/or provided the file.

Or do you mean that it's a .WLMP file? If so, that's probably a Windows Live Movie Maker project, and if so can't be played on a Mac. The provider needs to save the movie as .WMV or another standard format (preferably MPEG-4 or H.264).

Actually, this is a file that frequently accompanies video files. (.wimp) merely stands for 'Microsoft Windows Icon Palette'. How they got .wimp out of that, I don't know. But you can't do anything with that file, it is just a style that comes with the email. If there is no video file attached (and this happens a lot) then there was a failure on the sender's side. Email them back and ask for a different format, .mp4 is the best, .wmv will work, and if you are desperate .avi is also an option.

By the time we make our way around two or three fields of scrambling kids, and whistle-blowing adults, our coach has already started talking to the other 5-year-olds and their parents seated on the grass in front of him.

After a few more minutes of talking about parents having to make a team banner, provide refreshments, use lots of positive reinforcement and show up at every game, Coach has all the kids count off into two groups.

Coach lines the kids up again, this time with Sam in the middle of a front line, and blows his whistle. Sam kicks the ball once, halfheartedly, and then stands there as the pack moves off across the field again.

I never did. I never knew where to stand in the expanse of an athletic field. What was I supposed to do with my hands? I did spend two, or really more like one and a half, years on the rowing crew in college--which counts as a team sport, but since my feet were strapped in and I had to hold onto the oar, there was never any question of where to stand or what to do with my hands.

After years of self-conscious reflection, I have concluded that my lack of understanding of sports is based not on some un-American wimp factor that lifting weights could correct, but on a missing gene. And this is one genetic flaw that I am not going to pass along to my son.

I try not to watch the pregame warm-up drills. I manage not to shout across the field to Sam to quit chewing on the collar of his uniform and try to keep his gaze in at least the general direction of the ball.

Sam, and his team, scored the first goal of the season. And I have to admit that I have told a few other guys about it. What I have not talked much about is that it may not be too late for me to get team sports--from listening to my son.

According to many, it would be better to have called it invisible matter, rather than dark matter. It not only doesn't emit or absorb light, but it doesn't interact with any of the known, directly detectable particles through the electromagnetic, strong, or weak nuclear forces. The most sought after dark matter candidate is the WIMP: the Weakly Interacting Massive Particle. The big hope was for a WIMP miracle, a great prediction of supersymmetry.

The Universe, from an astrophysical perspective, has to be made of more than just the normal matter we know of. Normal matter, in this instance, qualifies as any of the known particles in the Standard Model. It includes anything made from quarks, leptons, or the known bosons, and includes exotic objects like neutron stars, black holes, and antimatter. All the normal matter in the Universe has been quantified through a variety of methods, and it only totals up to about a sixth of what must be present, overall, to explain the gravitational interactions we see on cosmic scales.

The big problem, of course, is that all of our evidence for dark matter is indirect. We can observe its effects in the astrophysical laboratory of space, but we've never detected it directly, in a laboratory here on Earth. That isn't, mind you, for a lack of trying.

If you want to directly detect dark matter, it isn't as simple as detecting the known particles of the Standard Model. For anything made out of quarks, leptons, or the known bosons, we can quantify what forces they interact through and with what magnitude. We can use what we know about physics, and in particular about the known forces and interactions between the known particles, to predict quantities like cross-sections, decay rates and products, scattering amplitudes, and other properties we're capable of measuring in experimental particle physics.

As of 2019, we've met with tremendous success on those fronts that have confirmed the Standard Model in ways that both theorists and experimentalists could have only dreamed of half a century ago. Detectors at colliders and isolated, underground facilities have led the way forward.

We understand how the Standard Model particles behave. We have solid predictions for how they should interact through all of the fundamental forces, and experimental confirmation of those theories. We also have extraordinary constraints on how they're permitted to interact in a beyond-the-Standard-Model fashion. Because of our constraints from accelerators, cosmic rays, decay experiments, nuclear reactors and more, we've been able to rule out many possible ideas that have been theorized.

When it comes to what might make up the dark matter, however, all we have are the astrophysical observations and our theoretical work, in tandem, to guide us. The possible theories that we've come up with include a huge number of dark matter candidates, but none that have garnered any experimental support.

This is where the idea of WIMP dark matter came from. These new particles couldn't have interacted through the strong or electromagnetic interaction; those interactions have too high of a cross-section and would have already shown up. But the weak nuclear interaction is a possibility. Originally, the "W" in WIMP stood for the weak interaction, because of a spectacular coincidence (appearing in supersymmetry) known as the WIMP miracle.

Of course, if any new particles interact through the electroweak force, they'd couple to the Standard Model particles, too. If a new particle couples to, for example, the W or Z boson (which carry the weak force), then there's a finite, non-zero likelihood that these particles will collide with any particle that a W or Z boson couples to, like a quark within a proton or neutron.

This means we can construct dark matter experiments looking for a nuclear recoil of known, normal matter particles. Recoils beyond those caused by normal matter would be evidence for the existence of dark matter. Sure, there are background events: neutrons, neutrinos, radioactively decaying nuclei in the surrounding matter, etc. But if you know the energy and momentum combinations of the signal you're looking for, and you design your experiment cleverly, you can quantify your background and extract any potential dark matter signal that may be there.

These experiments have now been ongoing for decades, and have seen no dark matter. The most stringent modern constraints come from LUX (above) and XENON 1T (below). Those results inform us that the interaction cross-section for protons and neutrons is extraordinarily tiny, and are different for both spin-dependent and spin-independent scenarios.

This is a different measurement than having dark matter particles self-annihilate, but that measurement tells us something incredibly valuable. The models of supersymmetry or extra dimensions that give the right dark matter abundances through the weak interactions are ruled out by these experiments. If there is WIMP dark matter, it must be weaker than the weak interaction permits to comprise 100% of the dark matter. Additionally, the LHC should not detectably produce it.

Theorists can always tweak their models, and have done so many times, pushing the anticipated cross-section down and down as null result after null result rolls in. That's the worst kind of science you can do, however: simply shifting the goalposts for no physical reason other than your experimental constraints have become more severe. There is no longer any motivation, other than preferring a conclusion that the data rules out, in doing so.

But performing these direct detection experiments is still incredibly valuable. There are other ways to produce dark matter that go beyond the most conventional scenario. Furthermore, these constraints don't necessitate a non-WIMPy source of dark matter. Many other interesting scenarios do not need a WIMP miracle.

For many decades, the "W" has been recognized to stand not for the weak interaction, but to stand for an interaction no stronger than is allowed by the weak force. If we have new, beyond-the-Standard-Model particles, we're allowed to have new forces and interactions as well. Experiments like XENON and LUX are our only way to probe those.

Additionally, dark matter candidates that are produced by a different mechanism at lower mass ranges, like axions or sterile neutrinos, or through the gravitational interaction alone at higher masses, such as WIMPzillas, are very much in play.

Our hunt for dark matter in the lab, through direct detection efforts, continues to place important constraints on what physics may be present beyond the Standard Model. For those wedded to miracles, though, any positive results now appear increasingly unlikely. That search is now reminiscent of the drunk looking for his lost keys beneath the lamppost. He knows they're not there, but it's the only place where the light enabling him to look shines.

The WIMP miracle may be dead and gone, as particles interacting through the weak force at the electroweak scale have been disfavored by both colliders and direct detection. The idea of WIMP dark matter, however, lives on. We just have to remember, when you hear WIMP, we include dark matter that's weaker and wimpier than even the weak interactions will allow. There is undoubtedly something new out there in the Universe, waiting to be discovered.

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