Whilst it is evidenced by many cosmological and astrophysical observations, dark matter still evades detection on Earth. As a consequence, the current particle and astroparticle literature is quite rich in proposals trying to satisfy cosmology with dark matter, and explaining its non-finding.
[image credits: 36Janusz (Pixabay)]
Whilst I promised @agmoore2 to write about some non-dark topic this week, I changed my mind… I could not resist after having read an interesting scientific article discussing mirror worlds and mirror dark matter.
In the world as we know it, elementary particles and the way they interact are governed by the Standard Model of particle physics. This yields a quite accurate description of nature.
However, the Standard Model does not contain any particle that could be dark matter.
Towards a hidden mirror world
Many theories featuring dark matter rely on the existence of a hidden world.
This hidden world is made of new elementary particles that do not feel three of the four fundamental interactions: electromagnetism, weak and strong interactions. Instead, they are sensitive to new interactions specific to the hidden world.
[image credits: Alexas_Fotos (Pixabay)]
In the mirror-world construction, we push this idea further.
We associated to the elementary particles of the Standard Model (quarks, electrons, positrons, the Higgs boson, etc.) mirror counterparts (mirror quarks, mirror electrons, mirror positrons, a mirror Higgs boson, etc.).
As a second step, we take the three fundamental interactions of the Standard Model (electromagnetism, the weak interactions and the strong interactions) and define a similar dynamics in the mirror world (mirror electromagnetism, mirror weak interactions and mirror strong interactions).
In a few words, we make an entire, secluded, mirror copy of the Standard Model. Whilst the visible world is sensitive to the usual fundamental interactions, the mirror world is solely governed by the mirror interactions.
On different lines, the mirror elementary particles could combine to form mirror neutrons, mirror protons and even mirror atomic nuclei (similarly to what happens in the visible sector). In the mirror-world framework, this mirror matter is dark matter.
Crossing the mirror
Particle physics models are based on principles of symmetries, which implies that at the level of the theoretical modelling, anything allowed by the symmetries has to be included. Going back to the mirror-world framework, all underlying symmetries permit the existence of connections between the visible and mirror worlds.
Experimental constraints however indicate that these connections have to be extremely fainted. Consequently, mirror particles can interact with normal matter, but only very occasionally.
In other words, mirror dark matter passing through Earth can interact with matter once in a while, which could potentially be recorded.
In the discussed scientific article, the authors predict the hints that mirror dark matter should leave in a dark matter detection experiment named LUX. The LUX detector contains 370kg of liquid Xenon surrounded by state-of-the-art electronics, and is extremely sensitive to the tracks left by a dark matter particle hitting one of the Xenon nuclei of the detector.
The results are given in the figure below.
[image credits: arxiv]
The two axes represent quantities that can be measured by LUX, and the dots consist in data.
Whilst LUX is shielded to prevent visible particles from interacting in the detector, this sometimes happens. The corresponding background expectation consists in the cloud of points shown on the figure. There is indeed no dark signal!
In contrast, hints for the existence of a mirror world would manifest as an extra concentration of points within the contours bounded by the solid lines. The results do not feature this signal.
Take-home message
In this post, I described a particle physics construction in which the Standard Model (or the visible world) comes accompanied with a secluded mirror copy to which it is feebly linked. This mirror world consists in dark matter.
This weak connection between the visible and mirror worlds allows for the detection of the mirror world in standard dark matter experiments. I have detailed a recent article in which the absence of any mirror world signal has been highlighted.
If a mirror world exist, its connection to our world has to be even weaker than expected!
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Thank you for breaking your promise. This article captured my imagination as no other article on dark matter has so far. I mean, this is an irresistible notion...a mirror world, where the weak footprint of dark matter might be detected.
I love the notion of symmetries.
My imagination is quite vivid, and you have given me much to contemplate. There is a universe of speculative fiction I could write, based on the mirror world and the dark matter it may harbor. I know that is not the purpose of your essay, but you have to see the beauty in this--I know you do, because the subject excites you. That excitement is contagious.
I hope my foray into imaginative speculation does not overly offend the scientist in you :))
I really liked this one @lemouth!
You are then very welcome ;)
Strictly speaking, it is just a single universe divided in two sectors that barely speak with each other. The 'barely' means that there are some (fainted) talkings, which opens the door to probing the hidden sector.
This is exactly the reason why I write about all of this. Trying to unveil some excitation into the reader towards science (and particule physics in particular), and share mine ^^
Hi @lemouth,
I think I do get it about both occupying the same "world". As I read, in the back of my mind was the thought of the notion of the doppleganger--I know that's not physics, but in a way it's a visceral understanding of the particle physics concept of mirror worlds. Dopplegangers occupy the same universe but are mirror images of each other.
Particle physicists operate in a sphere most of us do not understand very well, and yet you deal with the physical reality in which we all exist. So, what you do may seem remote, but it's not--no more than the planets and sun were for Galileo and his contemporaries.
I go on like this (forgive me) because I do find your work exciting. Einstein's Theory of Relativity affected the way we view ourselves in the universe. It changed not just science, but literature, philosophy, history. What you do now...if dark matter and mirror world's exist...how will that change the way in which we view our place in the universe? Our view of 'reality'?
You see you have captured my imagination--the hazard of dealing with someone who is used to thinking in symbols.
Thanks for sharing a fascinating perspective on the reality we all share.
We can actually see this as a dopplegagner. In fact, you just confirmed the topic of my next post (unless my image is delivered): mirror stars! But you probably will have to wait until next week... For now, I only know what I will talk about and I still need to start filling the empty file in :D
I hope this will push your imagination further :)
I just can't resist.
Startrek parallel universe. Here are the Doppelgänger! :D
Argh! :D
😂
Ok I have my imagination running wild now. I am thinking of a sci fi story with mirror galaxies, solar systems, planets, and maybe even mirror people and mirror me. Hmm, who is that guy in the mirror, my dark side? Lol
Anyhow, my imaginations apart, I think this is a really cool hypothesis. And I was also able to understand most of it. One question came in mind regarding detection though. Say if electromagnetism has exactly same properties as mirror electromagnetism and strong force and mirror strong force, what does it mean for the detector. Say one in a billion event is caused by a mirror electron in LUX would we be able to tell it apart? Why or why not?
I am sure you will love one of the comment I made above, to @agmoore2: my next post will probably be on the same topic, addressing mirror stars. Can you get even wilder? We will know next week :)
To answer your question, the detection depends on mirror particles being able to interact with 'normal' particles. This comes from the connections between the two worlds. One of these connection relies on electromagnetism and dark electromagnetism mixing a little bit with each other. Whilst there is no way out theoretically, this mixing is extremely suppressed to keep standard electromagnetism almost untouched (because we didn't see anything so far). However, when billions of particles happen, a standard interaction may just be dark. The key is that we really need the billions here because we are dealing with super rare phenomena.
The other connection are related to the Higgs bosons (even harder to detect than the mixing of the two electromagnetisms) and gravity (impossible to see at the level of fundamental particles).
Does it clarify?
That I understood. I think my question was from much more naive thinking. I think I should read a bit more on how particle detectors work. What I was wondering is about what if we are seeing them because we mistake them for normal particles. Like on the two axes in the above figure, there are two properties that can be measured by LUX, right. I am assuming these properties may depend upon how particle interacts with say EM field in the detector, it's trajectory, charge, mass and those things. Now if we assume mirror electron had same charge and mass as normal electron but only difference being that it interact just with mirror EM force. So is there a chance that if we do see a mirror electron once in a while we may mistake it as normal electron. But again my thinking is based on zero knowledge about the particle detection and I am just thinking in wrong direction. 😁
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This is part of the background, indeed. I recall that the background expectation is the observed distribution (there is no signal).
In the case of a signal, we should observe a global difference in the distribution of the datapoint. We should get the background (the data points, I recall) plus what we can get from the solid contours. In other words, we have enough discriminating power.
I think that now I answer the question (otherwise, please come back again to me :D )
Here I am again with my crazy comments! 😆
How fascinating to learn about a possible secluded mirror world which is faintly connected to ours. My imagination has gone pretty wild after reading this!
As for the following statement:
@lemouth, wasn't more or less like this that the Higgs boson was first detected? Through its rare interactions with matter?
I am sure @agmoore2 will not be disappointed! :)
You know me too well, dear Abigail. I absolutely love this! I was tired when I read this (1:17 AM here) and thought I'd have trouble concentrating. But got into it right away. A mirror world!
It's very exciting. Can't wait for the next installment :)
I am happy to read it was easy enough for a "soon-to-bed" reading.
For the next post on neutrinos, I am actually waiting for a dedicated image. As soon as I will get it, I will post it. In the meantime, I may write about other topics. Whilst there are actually other cool things about mirror worlds, maybe I will focus on something quite different. I will see by the end of the week :)
I like to read your crazy comments! Always! As you know, I am looking forward to read those comments ^^
In fact, I am not really sure that I want to know the wild part... ;)
At this level, the Higgs boson can be seen as interacting a lot with matter. We are talking about a huge difference in orders of magnitude. Give or take, we could easily have millions of Higgs boson's interaction for one single dark matter interaction.
On the fun side, the Higgs boson is today a background to many searches for new phenomena... The signal of the day is the background of tomorrow. This has always be the case in particle physics.
I hope not ^^
Hello @lemouth,
Je me permets de commenter en fr. Un de mes articles préférés et en plus d'être intéressant il m'a fait bcp rire. Je ne peux pas le comprendre sans passer par deepl et peut être que la traduction du titre n'est pas correcte mais je me suis dit @lemouth nous parle d'un monde parallèle ? la physique "croit" en l’existence d'une monde parallèle ?!?
Bref je me suis régalée.
A+
Christel
Pas de soucis pour un commentaire en francais. Je ne ferai aussi un plaisir de repondre dans la langue de Moliere. Je n'ecris en fait plus en francais car je n'avais plus aucun commentaire du tout. Cela a tue ma motivation.
En fait, ici on n'a pas un monde parallele mais plutot un unique univers ou tu as deux types de particules: celles du monde 'visible' (cad le Modele Standard de la physique des particules) et celles du monde 'sombre (les particules de type miroir). Au final, les deux secteurs se parlent peu, mis a part quelques interactions de tres faible intensite.
Ce n'est donc pas du multivers que je parle ici, mais de quelque chose d'entierement different. Est-ce plus clair?
Very interesting idea! :)
Sadly it's probably wrong, but we can never know.
Even tho I've met with dozens of various detectors I couldn't remember LUX or didn't hear about it at all.
Anyways, just went into the literature about LUX... and I'm amazed with the usage of a tank of purified xenon to detect DM! Sad to hear it is decommissioned. DM is giving all of us lots of troubles understanding it. :)
Very nice read, thanks for simplifying the article and sharing it with us. :)
LUX is over, but continues at the same time, under the form of the LZ project. Xenon has still a lot to teach us on dark matter :)
Concerning the mirror Standard Model, I am quite skeptical as well. Whilst I am entirely fine with hidden sectors, I do not see why the interactions and the particle content should be copies of the visible ones. However, we do not know and it is important to be pragmatic and test all options.
Could a "mirror world" also just be our own universe rotated slightly in an alternative spacial dimension (like flatland dimension, not the sci-fi "dimension" concept usually confused with multiple universes), with our only interaction being gravitational?
Mmmmh the title may not be that appropriate relatively to the message I wanted to convey. Here, I am not addressing mirror worlds in the sense of a multiverse thing. I am considering a single universe (i.e. ours) that contains two secluded sectors of particles, that I have abusively called worlds.
One of these is made of matter and its interactions, the second one is made of dark particles and their own interactions. Thanks to very weak mediations, a given sector is allowed to speak with the other one (which provides a way to the visible side to probe the dark side, and vice versa).
So after this intermezzo, to go back to your question:
Yes, it could somehow, except than instead of talking about 'dimensions', we could speak about 'ways to interact'.
Gravity is always there of course, but too weak to play any role at the particle level. The funny thing is that the Higgs boson and its dark counterpart are by definition making a connection. Similarly, dark electromagnetism and electromagnetism are connected automatically. Therefore, if one takes a mirror of the Standard Model, there are two connections beyond gravity by construction. Those connections are way stronger than gravity (even if they are weak, gravity is way weaker), and they are those that can be constrained experimentally.
I hope this answers at least a little your question. Don't hesitate to come back to me if needed :)
I indeed do not talk bout extra dimensions (which is en entirely other topic). In this post, I consider our good old four-dimensional space-time. There are just two classes of particles in there, and interactions between classes are extremely feeble.
The signal to observe would here be only this feeble interaction happening in a detector.
Does it clarify?
Great post as always. I wonder how black holes may link the standard model world and the dark matter mirror world
Mmmmh this is a good question. Black holes are governed by gravity. As gravity is the same in both the visible and mirror sectors, black holes do not really care about particles being 'normal' or 'mirror' particles. So in short, black holes provide a link. But this link is one of the three possible ones (see also my answer to the comment of inertia in this post).
I hope this clarifies. Otherwise please let me know.
I remember "mirror matter" was mentioned in one of the episodes of the season movie "Flash". I didn't understand it that time but I think I now have. It's great reading about this here. Nice piece sir.
PS: have you seen any episode of Flash?
I have actually seen all episodes of Flash... believe it or not... But I don't remember exactly which episode this was mention. However, please note that what is called dark matter (or possible anything related to physics) in Flash is sometimes quite far from what it is in reality. It is a series after all ^^
PS: there is a gorilla staring at me, and I am Harrison Wells ;)
Lol. You're Harrison Wells? Then I'm Cisco Ramon :)
It's cool that you now watch movies. I can recommend other cool sci-fi movies if you need them.
According to your hair cut, I am sure you are not Cisco. Good try! ^^
I rarely watch movies, but series are fine in the sense one episode is 30-45 minutes. That is a break I can sometimes take in the evenings (especially on Fridays).
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Good post bro.
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