A new search for putative dark matter particles, known as wimps, aims to succeed where others have failed/Clara Moskowitz
The article was published with the approval of Scientific American Israel and the Ort Israel network
Now or never”: this is the state of the physicists' preferred theory to explain dark matter, the invisible substance that, according to the hypothesis, fills the universe. Many physicists believe that the particles that make up dark matter are "particles with mass that interact using the weak nuclear force", known as "WIMPs" for short (literally: "Weakly Interacting Massive Particles"). The largest and most sensitive experiment to date for finding wimps, XENON1T, was launched in March 2016 at Italy's National Laboratory in Gran Sasso.
This project operates the latest detector in a series of detectors that started operating back in the 80s, but so far none of them have been able to find dark matter. If the elusive particles are not found in the coming years in the XENON1T experiment, physicists may be forced to abandon the leading theory and look for more exotic explanations. "Confirmation of our good models is within reach of XENON1T," says Raphael Lang, a physicist at Purdue University who is working on this experiment. "If we don't get it, it means our ideas are completely wrong, and we really have to go back to the drawing board."
The hypothesis of the existence of wimps stems from a prediction of superstring theory. This extension of the standard model of particle physics raises the possibility that each of the elementary particles of matter known to us has a partner, a corresponding particle. Wimps are probably the couple with the lowest mass, and physicists actually support them as candidates for dark matter particles because the theory automatically predicts that they are present in exactly the amount corresponding to the amount of dark matter that experts know exists based on its gravitational pull. (Dark matter represents, according to estimates, about 84% of all matter in the universe.) Many versions of wimps have already been ruled out after previous searches for them turned up clay. But the researchers still hope that one of the remaining options will show up in the experiment.
The XENON1T facility is buried in a cave at a depth of 1,400 meters in the thick of the earth: a large cylindrical tank, containing 3,500 kilograms of liquid xenon. This material naturally emits light when its atoms are moved. The scientists hope to be able to capture the rare event in which a dark matter particle will collide with a xenon nucleus, a collision that should leave a unique energy signal. Although dark matter is said to be ubiquitous, about 100,000 dark particles are said to pass through every square centimeter of space every second, it almost never interacts with normal matter and usually only reveals itself through gravity (due to its accumulated mass). . After XENON1T's planned two-year search, the detection of just 10 particles that appear to match the predicted properties of dark matter will be enough for the experimenters to declare a discovery.
The project, which costs 15 million dollars, is financed by the cooperation of 10 different countries, and was preceded by another run of the experiment, 25 times smaller. Allow it to cross the sensitivity threshold of the previous experiment within two days of its activation. It should also overtake within a few weeks the leading dark matter experiment today, the large underground xenon experiment (LUX), which contains 370 kilograms of xenon and is carried out in South Dakota. "I wouldn't be surprised at all if XENON1T manages to discover something that has only slightly eluded the previous generation of experiments," says Tim Tate, a theorist at the University of California, Irvine, who is not participating in these experiments.
Meanwhile, wimps may appear every day at the Large Hadron Collider (LHC) near Geneva, where protons collide with each other at close to the speed of light, creating new particles in the process. The accelerator began its second run in 2015, at almost twice the energy it was operated in 2009, and should now have the power to create more or less the same range of wobbles that XENON1T should be able to detect.
And if in the coming years none of these experiments show a hint of particles, it may be time for theorists to look for another explanation for dark matter. "On the one hand, we know it exists, but on the other hand we know very little about it, so it's very easy to come up with all kinds of theories," says Tait. "And if we don't see it, it will become clear to us that dark matter is even more strange and wonderful than we previously guessed."
22 תגובות
Hello everyone
I want to understand what it means: "last call to the dark matter"?? What is this, begging him??
Maybe we'll try new methods??, what do you think about: "NASA asks the dark matter to show itself"?
Maybe we'll show some nerves?: "Deer Black, the dark matter, show yourself!, it's not funny anymore, you've been playing hide and seek with us for 80 years, enough, either you show yourself or... we'll stop talking about favors!!".
Maybe we'll try the positive method?, "Dear dark matter, we gave you germanium, we built you the big accelerator in Zern, and now, feeding you xenon, we threw you into the depths of the mines, and you still don't want to show yours?, why??? Lmmmmmmmmmmmmmmm!!!???”
Maybe we will send you those who are sure of your existence?, Albanzo for example???, what do you say?, won't help???"
Say, you, enjoy being sent to a parallel universe? , do you know what you are doing to dark energy??, you are just destroying it with half the physics of the XNUMXth century!!
Wait, I don't understand, aren't you afraid that we will all agree with Sabdarmish's opinion that you don't exist??
So have a good week everyone and happy to be back on the dark battlefield.
good week!
Yehuda
Life
Everyone knows that if other universes had the ability to influence our universe then this is the most convincing proof that they are in the same universe.
Who can explain to me (without speculations and suppositions) why the dark matter is dispersed in space, even though for it the gravitational force that pulls to a "great collapse" is not opposed to the electromagnetic forces that create dispersive pressure? Even on a local scale, without repulsion between similar electric charges any dark matter cloud should collapse into a black hole? Is this a result of dark energy alone, or is the explanation in the Pauli principle? And if so, why is the distribution of the dark matter different from that of the luminous matter?
Try the article in its free version:
https://arxiv.org/pdf/astro-ph/0606216v1.pdf
"Can MOND take a bullet? Analytical comparisons of three G.W. Angus; B. Famaey & H. Zhao (September 2006). "Can MOND take a bullet? Analytical comparisons of three versions of MOND beyond spherical symmetry". Mon.Not.Roy.Astron.Soc. ". If I dropped a rock on us, access the conclusions chapter at the end of the article only. I am not knowledgeable enough to judge this issue. Basically, from browsing the net, probably Albenzo is right and MOND or the Newtonian force update alone (!) does not explain the bullet cluster. It seems to me that an examination of alternative theories for dark matter is required, and I do not think that this will overthrow string theory.
Joseph,
How do they deal with observations like the "Bullet cluster" that Alvancho mentioned earlier?
In my opinion, MOND may deserve a fresh look. On the website of Professor Motty Milgrom, there are research papers on the subject, and he has articles in popular newspapers such as Scientific American and other newspapers that resonate.
Thanks
elbentzo
That's why I asked and more out of caution. We will go in the direction of a thought exercise. If dark matter does exist in one or more parallel universes and if it is pure, it might be worth at least trying to build models. It is also possible that the rules of physics there are different than here. Building so many models, maybe you should get a little wild. The resulting research was reviewed. Worth the effort. Sometimes in this way you can reach new insights. How about doing another thesis, if you have some free time.
Haim,
Not sure I understood. If dark matter is not here but in a parallel universe, then why would we feel its effect here? Although dark matter has never been detected microscopically, but as I mentioned in response to the opponent, there are observations of systems in which there is a difference between the center of mass and the visible matter - that is, there is something that cannot be seen but it changes the center of mass of the system. If dark matter resides in another universe, how does it do so? I'm not sure I understood, but from what I understood, it doesn't seem likely to me.
rival,
MOND is indeed an alternative to general relativity and it does not contain dark matter. But its support among physicists is quite negligible (and a large part of it is concentrated in Israel, so a false image can be created as if it is more popular than it really is). There are of course many reasons for this, but the most important of them is that it simply fails the experiment. Although there are observational data that she is able to explain without dark matter, there are also some that she simply cannot. The most famous example is the bullet cluster, which has been studied in depth and photographed in more or less every possible spectrum, and it can be seen in the clearest and sharpest way that its center of mass is very far from the visible center of mass, also according to the MOND model. That is, even if MOND was correct, the conclusion it draws about this cluster is that it contains "invisible" matter - dark matter. Of course this is not the only example, but this is considered the example that finally killed MOND in the eyes of many physicists from the field. Beyond that, there are of course theoretical problems mainly in the field of cosmology.
Rival, as far as I know very few physicists would agree with you about MOND, especially about elegance. In any case, as far as I can judge simplicity is not a significant criterion in contemporary physics. So far, anyone who has tried to be simple has sinned in simplicity...
elbentzo
I have a question for you about the dark mass. And I ask in the most careful way since my knowledge in the field is extremely limited. Maybe you're looking for the dark mass in the wrong place? If indeed there are parallel universes, then they too must have mass. Maybe the missing mass is in these places?
Thanks.
By the way, I came across an interesting theory called "revised Newtonian dynamics" which proposes to change the accepted physical formulas in order to get an adjustment to the observations without the need for dark matter:
"Currently, DNM is able to predict the velocities measured in the observations more accurately than the dark matter theory. Despite this, today only a small minority among the scientists currently supports the DYNAM, but if this situation changes there is no doubt that this will bring about a real scientific revolution, and perhaps even undermine the conventions for other laws in the world of physics nowadays... since they started measuring the magnitude of the speed and the curvature of the rotation of the galaxies in order to compare the different theories, the Dynam theory is the one that explains the observations in the most elegant and simple way. Compared to the other theories, DYNAM has one parameter that must be completed for each galaxy separately, and it is the starlight-to-mass conversion factor. On the other hand, the dark matter theory needs two parameters in order to prove this fact - the amount of dark matter and its mass.
https://he.wikipedia.org/wiki/דינמיקה_ניוטונית_מתוקנת
A bit of order: String theory really has nothing to do with it. The WIMP is a result of supersymmetry, which can also exist independently of string theory. That is, it is possible that supersymmetry is correct and strings are not, it is possible that both are correct (what is called in the article "superstrings"). It is unlikely that string theory is correct and supersymmetry is not (in fact, usually when they say "string theory" they mean superstring because strings without supersymmetry have no point - it is not able to describe many things in our world).
Not finding WIMPs will not disprove supersymmetry because it does not predict exactly the field in which they can be found. It is possible to "play" with the parameters of the theory and produce an identical theory only in which the WIMPS are more massive and harder to detect. Refutation should only come from an experiment that shows positively that some predicate does not hold, and not from not being able to find this or that particle. But even though it won't disprove it, theories in physics have a shelf life and if something doesn't produce results for long enough, people start looking for another explanation. I'm not sure exactly when this will happen to supersymmetry, because it is necessary for string theory (as we said, without it string theory doesn't really work) and string theory - although it has no observational evidence - is very, very strong theoretically and is the field in which most physicists today pin their hopes for the future It has amazing achievements (only theoretical, unfortunately) that no other theory comes close to and without supersymmetry it more or less goes to waste. Therefore indirectly, its strength as a theory that solves lots and lots of theoretical problems also goes to supersymmetry.
rival,
Yes, an electron has 2000 times less mass than a proton. In terms of rest mass, 99.98% of the matter in the room is protons.
elbentzo,
You're right, that's how you have to read quickly while working.
Regarding the example, in practical terms the mass of the electron is much smaller than the mass of the proton as far as I remember, it's not really half the mass right?
"The hypothesis of the existence of wimps stems from a prediction of superstring theory"
If the particles are not discovered in the experiment, will this disprove the superstring theory? And what about string theory?
right
to NET
Based on your response below, let me guess that:
Your profession/education is in the field of engineering. engineer or engineer.
Am I right or wrong?
Energy is not matter. Dark matter is about 84% of all matter in the universe, but it is only about a quarter of its energy content. A silly example - if I have a room with an electron, a proton and a photon that all have the same energy, then the electron makes up half of the matter in the room but only a third of the energy.
Agree with an opponent. Can someone please tell me the official percentages of matter and dark energy in the universe?
"Dark matter represents, according to estimates, about 84% of all matter in the universe"
Strange, I thought the number was closer to 25% (and dark energy around 70%).