Antihelium Discovered By STAR

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Antihelium Discovered By STAR

Posted by Soulskill on Monday April 25, 2011 @05:54AM from the makes-your-voice-really-low-then-vaporizes-your-lungs dept.

Medevilae writes with this excerpt from ScienceBlog: "Eighteen examples of the heaviest antiparticle ever found, the nucleus of antihelium-4, have been made in the STAR experiment at RHIC, the Relativistic Heavy Ion Collider at the US Department of Energy's Brookhaven National Laboratory. ... Ordinary nuclei of helium atoms consist of two protons and two neutrons. Called alpha particles when emitted in radioactive decays, they were found in this form by Ernest Rutherford well over a century ago. The nucleus of antihelium-4 (the anti-alpha) contains two antiprotons bound with two antineutrons. ... 'It’s likely that antihelium will be the heaviest antiparticle seen in an accelerator for some time to come,' says STAR Collaboration member Xiangming Sun of Berkeley Lab’s NSD. 'After antihelium the next stable antimatter nucleus would be antilithium, and the production rate for antilithium in an accelerator is expected to be well over two million times less than for antihelium.'"

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Here comes the alchemy by tibbetts · 2011-04-25 06:04 · Score: 4, Funny

We're that much closer to mastering alchemy, because someday we'll be able to produce anti-antimony, i.e. mon(e)y.

--
:wq
1. Re:Here comes the alchemy by Dr.+Spork · 2011-04-25 06:09 · Score: 1
  
  Hillarious!
2. Re:Here comes the alchemy by I'm+not+really+here · 2011-04-25 06:53 · Score: 3, Informative
  
  http://en.wikipedia.org/wiki/Synthesis_of_noble_metals#Gold_synthesis_from_Mercury
  We already have made gold....
  
  --
  Before commenting on the Bible, please read it first
3. Re:Here comes the alchemy by ae1294 · 2011-04-25 07:01 · Score: 2
  
  http://en.wikipedia.org/wiki/Synthesis_of_noble_metals#Gold_synthesis_from_Mercury
  We already have made gold....
  Doesn't that mean we have become GODS? I think it does... lets just agree that it does...
4. Re:Here comes the alchemy by Belial6 · 2011-04-25 08:19 · Score: 3, Interesting
  
  No, we became GODS when we gained the ability to make the blind see, the lame walk, and raise the dead. We have been GODS for quite some time. We are just becoming more powerful GODS.
5. Re:Here comes the alchemy by newcastlejon · 2011-04-25 09:11 · Score: 2
  
  Doesn't that mean we have become GODS? I think it does... lets just agree that it does...
  Not quite...
  
  --
  If God forks the Universe every time you roll a die, he'd better have a damned good memory.
Stuff that anti-matters? by erroneus · 2011-04-25 06:08 · Score: 3, Funny

I guess Slashdot is expanding its scope to include stuff that anti-matters as well! And now it seem they are trying to up their anti- by trying to produce larger and more complex stable anti-atoms?
1. Re:Stuff that anti-matters? by jgagnon · 2011-04-25 06:39 · Score: 1
  
  As opposed to its current production of antipathy?
  
  --
  Remember to maintain your supply of /facepalm oil to prevent chafing.
2. Re:Stuff that anti-matters? by mikaelwbergene · 2011-04-25 06:47 · Score: 2
  
  I was anticipating someone was going to post something like this. Oh slashdot, you and your anticlimactic antics of antique natures.
3. Re:Stuff that anti-matters? by Blue+Stone · 2011-04-25 07:00 · Score: 1
  
  >I guess Slashdot is expanding its scope to include stuff that anti-matters as well!
  I thought that was Idle.
  
  --
  Corporation, n. An ingenious device for obtaining individual profit without individual responsibility. - Ambrose Bierce
4. Re:Stuff that anti-matters? by Anti_Climax · 2011-04-25 09:41 · Score: 1
  
  I knew this username was bound to pay off some day.
  
  --
  Even people that believe in pre-destiny look both ways before crossing the street.
5. Re:Stuff that anti-matters? by Em+Adespoton · 2011-04-25 10:41 · Score: 1
  
  I guess Slashdot is expanding its scope to include stuff that anti-matters as well! And now it seem they are trying to up their anti- by trying to produce larger and more complex stable anti-atoms?
  Pshaw, we've had RSS on here for years already!
No Positrons, No Anti-matter by Covalent · 2011-04-25 06:11 · Score: 4, Interesting

Without positrons (anti-electrons) orbiting the nucleus, these are just high energy anti-particles. Technically anti-matter, but not really available for interesting study. What would be much more interesting would be molecular anti-hydrogen, complete with positron bonding. Then you could test many properties of anti-matter. But cooling and storing is still a major problem. This is an interesting discovery, but we're no closer to really understanding anti-matter because of it (or, for that matter, having warp drive.)

--
Great warrior...hrmph! Wars not make one great.
1. Re:No Positrons, No Anti-matter by doconnor · 2011-04-25 06:23 · Score: 3, Interesting
  
  Quirks and Quarks had a story a few months ago about the quest to make anti-hydrogen.
2. Re:No Positrons, No Anti-matter by ae1294 · 2011-04-25 06:29 · Score: 1
  
  Without positrons (anti-electrons) orbiting the nucleus, these are just high energy anti-particles. Technically anti-matter, but not really available for interesting study.
  What would be much more interesting would be molecular anti-hydrogen, complete with positron bonding. Then you could test many properties of anti-matter.
  But cooling and storing is still a major problem. This is an interesting discovery, but we're no closer to really understanding anti-matter because of it (or, for that matter, having warp drive.)
  Whhhaaat? Positron bonding is the easy part.... big hunks of negative particles love positive particles...
3. Re:No Positrons, No Anti-matter by gr8_phk · 2011-04-25 07:39 · Score: 2
  
  Without positrons (anti-electrons) orbiting the nucleus, these are just high energy anti-particles. Technically anti-matter, but not really available for interesting study. What would be much more interesting would be molecular anti-hydrogen, complete with positron bonding.
  
  But at least the nuclei stand a chance of magnetic confinement. Neutral atoms not so much.
4. Re:No Positrons, No Anti-matter by AdmiralXyz · 2011-04-25 07:42 · Score: 1
  
  It may not be an atom, but they did produce two antiprotons and two antineutrons bound by the strong force. AFAIK that's never been observed before, and it does count for something. Also, the heavier these things are, the easier they are to cool, so it may not be long before someone can produce "real" antihelium.
  
  --
  Dislike the Electoral College? Lobby your state to join the National Popular Vote Interstate Compact.
5. Re:No Positrons, No Anti-matter by mhotchin · 2011-04-25 08:21 · Score: 1
  
  The charge is used to isolate the particle. Once it is positron bound, it is overall neutral. How do you isolate it?
6. Re:No Positrons, No Anti-matter by Belial6 · 2011-04-25 08:23 · Score: 1
  
  My question though is, what is an anti-neutron? If it is in the nucleus, and it has a neutral charge, what is the difference?
7. Re:No Positrons, No Anti-matter by Taibhsear · 2011-04-25 08:29 · Score: 1
  
  Without positrons (anti-electrons) orbiting the nucleus, these are just high energy anti-particles. Technically anti-matter, but not really available for interesting study. What would be much more interesting would be molecular anti-hydrogen, complete with positron bonding. Then you could test many properties of anti-matter. But cooling and storing is still a major problem. This is an interesting discovery, but we're no closer to really understanding anti-matter because of it (or, for that matter, having warp drive.)
  Not really sure why this got modded up... There's no such thing as "technically" antimatter vs "really" antimatter. Helium is still helium even without the electrons (elements are designated by their number of protons or anti-protons and has nothing to do with their electrons). It just has an ionic charge (ie. plasma, alpha particle). Anti-helium is not an exception. It IS really available for interesting study or you wouldn't be reading the article. And making it a "whole" atom by adding positrons would REMOVE it from being available for interesting study on the many properties of anti-matter as it would then move (as it would no longer have a charge and thus would not be contained by the magnetic fields) and interact with normal matter and be destroyed. We ARE closer to really understanding antimatter because we now have verifiable evidence that it exists at the rates of generation that we thought it would.
8. Re:No Positrons, No Anti-matter by jo_ham · 2011-04-25 08:38 · Score: 2
  
  It has the opposite magnetic moment, and various other properties that are reversed compared to a normal neutron.
9. Re:No Positrons, No Anti-matter by ae1294 · 2011-04-25 09:55 · Score: 1
  
  Opposing plates that vibrate causing gravitational eddies to form holding the anti-matter between the quantum level gravitational waves?
10. Re:No Positrons, No Anti-matter by The+End+Of+Days · 2011-04-25 14:03 · Score: 1
  
  But that'll reverse the tachyon flow through the pulse coils.
Does it make your voice really low by bareman · 2011-04-25 06:14 · Score: 3, Funny

when you inhale it?
1. Re:Does it make your voice really low by ae1294 · 2011-04-25 06:30 · Score: 1
  
  when you inhale it?
  No... it would make it high... it's lighter than air.. I won't recommend it though... Wait.. no... I would recommend it.. make sure you film it for us...
2. Re:Does it make your voice really low by ae1294 · 2011-04-25 06:51 · Score: 1
  
  No. It wouldn't make it high. It would annihilate (literally) the parts of you that it touches and in the process create enough gamma radiation to kill everything around you. (If memory serves me right.)
  I also doubt, a camera would survive that.
  QUITE YOU! Where doing this for Pseudo-science!
3. Re:Does it make your voice really low by thedonger · 2011-04-25 07:14 · Score: 1
  
  No, it just explodes your throat.
  Giggiddy.
  
  --
  Help fight poverty: Punch a poor person.
4. Re:Does it make your voice really low by ae1294 · 2011-04-25 07:23 · Score: 1
  
  No. It wouldn't make it high. It would annihilate (literally) the parts of you that it touches and in the process create enough gamma radiation to kill everything around you. (If memory serves me right.)
  I also doubt, a camera would survive that.
  QUITE YOU! Where doing this for Pseudo-science!
  Nazi Update: Where = We're, honestly I think it sounds better with where.... but yes I know... shut up....
5. Re:Does it make your voice really low by DavidD_CA · 2011-04-25 07:46 · Score: 1
  
  Yes, but side-effects also include pulling your entire body towards the earth's core as if you were being yanked by a tow truck right through the upper crust.
  
  --
  -David
6. Re:Does it make your voice really low by Tolkien · 2011-04-25 07:59 · Score: 1
  
  You missed "Quiet".
  
  --
  how is babby formed?
7. Re:Does it make your voice really low by ae1294 · 2011-04-25 10:04 · Score: 1
  
  You missed "Quiet".
  O... yeah... ok damn... I guess you're going to be sending me to the camps now right?
8. Re:Does it make your voice really low by CrimsonAvenger · 2011-04-25 15:42 · Score: 1
  
  It would annihilate (literally) the parts of you that it touches and in the process create enough gamma radiation to kill everything around you.
  One atom of anti-helium? It would annihilate two protons and two neutrons, and produce enough gamma radiation to do essentially nothing at all - 10^-9 joules or so...
  
  --
  
  "I do not agree with what you say, but I will defend to the death your right to say it"
9. Re:Does it make your voice really low by Coren22 · 2011-04-26 07:09 · Score: 1
  
  You damn grammer Jew...
  (mods, this is a joke, not serious...)
  
  --
  APK likes to ask for responses to the same things over and over. Maybe he just likes the responses?
Karaoke by aztrailerpunk · 2011-04-25 06:16 · Score: 1

I already prepping my Barry White impersonation.

--
Foot placed squarely in mouth since 1983.
i gave my kid an anti-helium balloon by circletimessquare · 2011-04-25 06:20 · Score: 1

he cried as he dragged the heavy weight behind him

--
intellectual property law is philosophically incoherent. it is your moral duty to ignore it or sabotage it
1. Re:i gave my kid an anti-helium balloon by circletimessquare · 2011-04-25 06:35 · Score: 1
  
  no, no, no...
  buDUMP *ching*
  
  --
  intellectual property law is philosophically incoherent. it is your moral duty to ignore it or sabotage it
2. Re:i gave my kid an anti-helium balloon by I'm+not+really+here · 2011-04-25 06:55 · Score: 1
  
  I believe you were looking for http://instantrimshot.com./
  
  --
  Before commenting on the Bible, please read it first
3. Re:i gave my kid an anti-helium balloon by Em+Adespoton · 2011-04-25 10:46 · Score: 1
  
  he cried as he dragged the heavy weight behind him
  Wouldn't the balloon be more likely to deflate into negative space, pulling him along for the ride?
Re:Warp core fuel crisis by ae1294 · 2011-04-25 06:25 · Score: 1, Troll

I know I shouldn't laugh...
Why not, racism is funny... Just because someone makes a nigger joke doesn't make him a white plantation owner with SLAVES... Now if you make a cracker joke that does pretty much make you a black guy that mugs people.
Heaviest Antiparticle Claim is Ridiculous by LegoEvan · 2011-04-25 06:28 · Score: 1

Anti-helium has a mass exactly equal (well, if CPT is a good symmetry) to helium. The mass of helium is roughly 4 amu, which is ~4 GeV. The mass of the top quark is *significantly* more than that. The mass of the top (and antitop) is 172 GeV.
1. Re:Heaviest Antiparticle Claim is Ridiculous by OverlordQ · 2011-04-25 07:07 · Score: 1
  
  Try RTFS and/or RTFA:
  
  It’s likely that antihelium will be the heaviest antiparticle seen in an accelerator for some time to come..
  
  --
  Your hair look like poop, Bob! - Wanker.
No antilithium? by liquidhokie · 2011-04-25 06:36 · Score: 1

How anticlimactic.
Antihumor by chaynlynk · 2011-04-25 06:37 · Score: 1

'After antihelium the next stable antimatter nucleus would be antilithium'

Then we can have deep voices and even worse mood swings.
Okay, I get some of this . . . by mmell · 2011-04-25 06:38 · Score: 1

A proton's antiparticle is a negatron, which is just like a proton except for having a negative charge. Check.
An electron's antiparticle is a positron, which is just like an electron except for having a positive charge. Check.
Anti-hydrogen is an atom composed of a negatron orbited by a positron, and is antimatter. Check.
What the frell is an anti-neutron? A neutron with a lack of a lack of charge? (Okay, I get it - it's a neutron composed of antiquarks instead of quarks . . . but why would anti-helium require a nucleus composed of two negatrons and two anti-neutrons? Wouldn't it be two negatrons and two neutrons?) I'm confussed.
1. Re:Okay, I get some of this . . . by pclminion · 2011-04-25 06:42 · Score: 4, Informative
  
  An anti-neutron is like a neutron, but instead of being composed of an up quark and two down quarks, it is composed of an anti-up quark and two anti-down quarks. Each of the quarks has an electrical charge -- they add in such a way that the sum is zero. For an anti-neutron, the quarks have the opposite charges as before, but they still all add to zero.
2. Re:Okay, I get some of this . . . by Ironchew · 2011-04-25 06:46 · Score: 3, Informative
  
  "Ordinary" neutrons would annihilate anti-protons if they got sufficiently close, i.e., to form a nucleus. On a semi-related note, I remember reading that charge-reversal isn't the only property of antimatter; it can also be thought of like quantum spin-reversal or time-reversal (ordinary matter going backwards in time). Weird stuff.
3. Re:Okay, I get some of this . . . by pclminion · 2011-04-25 06:57 · Score: 3, Informative
  
  On a semi-related note, I remember reading that charge-reversal isn't the only property of antimatter; it can also be thought of like quantum spin-reversal or time-reversal (ordinary matter going backwards in time).
  That's really the most correct way to think about it. Take the electron, for instance. It always repels other electrons, period. If you get an electron going backward in time, it still repels other electrons, but because time is flipped around it looks like an attraction. It is not just charge but ALL the properties of the particle which are reversed.
  In the case of a neutron, imagine it not as a neutral particle but as an electric dipole (tripole really, but for simplicity imagine it's a dipole). When you get sufficiently far away from it, the net electric field is pretty much zero. It's not until you look at it very closely that you see the two opposite charges. Now, you can reverse those charges and still, at big distances it looks like there's no field. But you did in fact reverse the charges.
4. Re:Okay, I get some of this . . . by mmell · 2011-04-25 07:55 · Score: 1
  
  Hmmm . . . does this mean (as I've long suspected) that matter in our universe obeys not only the law of cause and effect, but the law of effect and cause - i.e., the law of causality is symmetrical?
5. Re:Okay, I get some of this . . . by pclminion · 2011-04-25 08:07 · Score: 1
  
  If you draw a Feynman diagram showing the annihilation of an electron with a positron, it looks like an electron which momentarily goes backward in time, and some photons shooting out. If you do the calculations, you get the right answer (the "answer" is the probability of it happening). That's really all you can say about it.
  It's not really like an electron goes forward in time for a while, then decides to mix it up a little and turns around and goes backward in time. It's just that there's no way to distinguish a positron going forward in time and an electron going backward in time. Whether it "really happens" isn't a useful question to ask because it doesn't predict anything.
6. Re:Okay, I get some of this . . . by Em+Adespoton · 2011-04-25 10:48 · Score: 1
  
  The magnetic moment is also reversed.
7. Re:Okay, I get some of this . . . by 3Cats · 2011-04-25 19:13 · Score: 2
  
  based on reading the above, my addled brain immediately thinks that all the antimatter went back in time to before the big bang,( to negative infinity and beyond,) while normal matter went forward in time. There. Solved THAT mystery.
Re:Warp core fuel crisis by NEDHead · 2011-04-25 06:39 · Score: 1

It may sound awesome, but when it runs Windows and crashes, it really is THE BLUE SCREEN OF DEATH!!
Discovered by STAR? by jd2112 · 2011-04-25 06:40 · Score: 1

That is the first time I've heard of a virus making a scientific discovery. I just hope the Iranians don't find a way to weaponize it.

--
Any insufficiently advanced magic is indistinguishable from technology.
1. Re:Discovered by STAR? by ae1294 · 2011-04-25 07:08 · Score: 1
  
  I just hope the Iranians don't find a way to weaponize it.
  All they need is a bag of party balloons and we are all screwed!
  You and I in a little toy shop
  Buy a bag of balloons with the money we've got
  Set them free at the break of dawn
  Til one by one, they were gone
  Back at base bugs in the software
  Flash the message, something's out there
  Floating in the summer sky
  99 red balloons go by
  99 red balloons
  Floating in the summer sky
  Panic bells it's red alert
  There's something here from somewhere else
  The war machine springs to life
  Opens up one eager eye
  Focusing it on the sky as 99 red balloons go by
  99 Decision street
  99 ministers meet
  To worry, worry, super flurry
  Call the troops out in a hurry
  This is what we've waited for
  This is it boys, this is war
  The president is on the line
  As 99 red balloons go by
  99 knights of the air
  Ride super high tech jet fighters
  Everyone's a super hero
  Everyone's a Captain Kirk
  With orders to identify
  To clarify, and classify
  Scramble in the summer sky
  99 red balloons go by
  99 dreams I have had
  In every one a red balloon
  It's all over and I'm standing pretty
  In this dust that was a city
  If I could find a souvenir
  Just to prove the world was here
  And here is a red balloon
  I think of you, and let it go
Re:Mis-quote? by dietdew7 · 2011-04-25 08:15 · Score: 1

Apparently, the periodic table has changed quite a bit since I took high school chemistry.
Anti-helium aka... by dvh.tosomja · 2011-04-25 08:42 · Score: 1

I thought anti-helium was sulphur hexafluoride
1. Re:Anti-helium aka... by sadness203 · 2011-04-25 13:35 · Score: 1
  
  Kinda like people think they can fight diabetes with salt to remove the sugar.
Re:Mis-quote? by Algae_94 · 2011-04-25 08:48 · Score: 1

no. after antihydrogen the next stable antimatter nucleus is antihelium which TFA is about. After antihelium the next stable antimatter nucleus would be antilithium.
Good news for future airships... by osu-neko · 2011-04-25 09:11 · Score: 1

When we run out of helium, we can manufacture anti-helium to replace it! ;)

--
"Convictions are more dangerous enemies of truth than lies."
1. Re:Good news for future airships... by goodmanj · 2011-04-25 14:33 · Score: 1
  
  Oh, the humanity!
Re:Warp core fuel crisis by ae1294 · 2011-04-25 12:19 · Score: 1

I know I shouldn't laugh...
Why not, racism is funny... Just because someone makes a nigger joke doesn't make him a white plantation owner with SLAVES... Now if you make a cracker joke that does pretty much make you a black guy that mugs people.
You see what the mod's don't know is that I'm a African American and by down-moding me they are repressing my right to take back a word that was used for hundreds of years to belittle my people. Everyone that moded the above down should be ashamed that they are censoring a African American's voice. I was attempting to inject humour into a bad situation but you have just reinforced everything that is wrong in America today.
Great job Crackers.
ae1294
Re:Warp core fuel crisis by layer3switch · 2011-04-25 12:37 · Score: 1

> my right to take back a word that was used for hundreds of years to belittle my people.
so you can now belittle your own... that ain't right.
> should be ashamed that they are censoring a African American's voice.
I agree... if that is the case.
> you have just reinforced everything that is wrong in America today.
everything like indiscriminate voting? which judge not by the color of the posters skin but the content of their post?

--
"Don't let fools fool you. They are the clever ones."
Captain Obvious by TangoMargarine · 2011-04-25 17:06 · Score: 1

The next, higher one than helium is going to be lithium? I'm gonna go out on a limb here and predict the next one after that will be beryllium.

--
Unity? Screw that: XFCE. Slashdot Beta? Screw that: SoylentNews. Australis? Screw that: Pale Moon. UX developers DIAF
From the beginning, what are the ten radical isoto by Garst · 2011-04-25 21:37 · Score: 1

From the beginning, the 10 radical isotopes are: Tucharium, -5; Dongor, -17; Lu, -31; Kartex, -79; Sharbar, -101; Ulanium, -127; Hyduron, -173; Simonsium, -211; Metite, -239; Krasnov, -307; These are the ten radical isotopes, from the beginning.
So if you inhale it by Maritz · 2011-04-25 23:35 · Score: 1

Does it make you sound like Paul Robeson/James Earl Jones?

--
I do not want your cheap brainburning drugs. They are useless for work. And I am a working man today.
Antimatter Experiment by Script+Cat · 2011-04-26 05:37 · Score: 1

Does anyone know if there is any possibility if antimatter might repel regular matter gravitationally? That is an experiment I would like to see. It's an assumption that the stars we see are ordinary matter. There really is no way of knowing from a distance. We don't get hit by antimatter meteors so we can tell matter and antimatter don't occur in close proximity to each other. So I total which of the following are true:
-Antimatter is extremely rare in the universe maybe none exists today.
-Antimatter is repelled by reacting with ordinary matter imparting momentum from the explosion segregating it from ordinary matter in the universe. Probably this happened in the earliest times.
-Antimatter is repelled by gravity with ordinary matter segregating it from ordinary matter in the universe. Maybe it accounts for dark energy observation.
1. Re:Antimatter Experiment by Muad'Dave · 2011-04-26 06:28 · Score: 1
  
  I think your 2nd and 3rd assertions are false, however the first one has an interesting side note. Ever heard of a PET scan? That's antimatter - Positron Emission Tomography. That nasty radioactive Potassium in bananas, 40K? It emits positrons (B+ decay) approximately 11% of the time. From this article: "In a human body of 70 kg mass, about 4,400 nuclei of 40K decay per second." That's 484 positrons/sec being annihilated within your body!
  Antimatter is all around us.
  
  --
  Tiller's Rule: Never use a word in written form that you've only heard and never read. You will end up looking foolish.
2. Re:Antimatter Experiment by Script+Cat · 2011-04-26 06:59 · Score: 1
  
  Cool++
3. Re:Antimatter Experiment by RockDoctor · 2011-04-29 01:02 · Score: 1
  
  Does anyone know if there is any possibility if antimatter might repel regular matter gravitationally?
  The idea does sound intuitively attractive, but I'm pretty sure that it doesn't work in practice. I can't recall enough physics to say why, but I don't think it's the case.
  
  It's an assumption that the stars we see are ordinary matter. There really is no way of knowing from a distance.
  The assumed symmetry of matter vs antimatter would preclude being able to tell the difference by spectroscopy (checking this in the lab is one of the main justifications behind trying to make significant quantities of antihydrogen, antihelium etc.). However, since we know (from accelerator experiments) that matter and antimatter do annihilate vigorously on contact, and we do not see this sort of energy release in the sky, then we can safely deduce that everything that we see is matter, not antimatter. Space is not a perfect vacuum ; the interstellar medium would make a strong glow where a region of matter met a region of antimatter. In this case, absence of evidence actually is positive evidence of absence.
  IIRC, one of the early theories to explain gamma-ray bursts was that they were evidence of antimatter object interacting with the Kuiper Belt/ Oort cloud. That theory went out of the window when their distances were measured.
  
  We don't get hit by antimatter meteors so we can tell matter and antimatter don't occur in close proximity to each other.
  We do get hit by antimatter meteorites, but they're very small. The first detection of the antielectron was for example, in cosmic ray studies on a balloon. There's a whole-sky telescope in Argentina (IIRC) designed to study precisely these high-energy cosmic ray events, because they're still of higher energy than can be produced in CERN, Fermilab, etc. Link
  
  So I total which of the following are true:
  -Antimatter is extremely rare in the universe maybe none exists today.
  See above ; rare, but not absent.
  
  -Antimatter is repelled by reacting with ordinary matter imparting momentum from the explosion segregating it from ordinary matter in the universe. Probably this happened in the earliest times.
  There is no mechanism the I know of which can do this. You can easily segregate on charge, but some antiparticles are positive (antielectrons) while some are negative (antiprotons) and others are neutral (antineutrons), so that's not going to segregate matter from antimatter without a prior processing stage.
  
  -Antimatter is repelled by gravity with ordinary matter segregating it from ordinary matter in the universe. Maybe it accounts for dark energy observation.
  I don't think gravity works like that - it's concerned with mass, not whether or not particles are matter or antimatter. Descriptions of "dark energy" emphasise that it behaves LIKE an antigravity, not that it is an antigravity.
  
  --
  Birds are not dinosaur descendants;birds are dinosaurs, for all useful meanings of "birds", "are" and "dinosaurs"