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Schedule

Posted: Fri Nov 27, 2009 2:37 pm
by foofighter
Hello!
Do you think LHC Schedule has changed at all over the past week or will it run to near the dates that you posted on the "LHC Schedule" thread?

Also what are the main differences between proton - proton and proton - anti proton collisions?

Re: Schedule

Posted: Fri Nov 27, 2009 3:13 pm
by Xymox
2 seperate questions..

1. I think they kinda thew the schedule out the window some time back..
Also they really don't work on a fixed schedule. It all works around how things progress.

My _guesses_ are

Collisions again around December 4th
Beam at 2 TeV soon after that and collisions like 10 days later
Collisions at 7 TeV early next year.

BUT again... This is just guess work and they could move ahead rapidly as they just did.

2. Im not a physicist and someone more qualified should answer that one.

Re: Schedule

Posted: Fri Nov 27, 2009 3:20 pm
by Danny252
Basically, one is like smashing rocks really fast, and the other more like sending 2 bits of lit TNT at eachother really fast. Of course, both have their uses!

Proton-Proton is like smashing 2 rocks together REALLY hard - and then when they break apart from the impact, we can see what they contain (such as quarks). Nothing too special happens apart from seeing what they fall apart into (and then what these things do).

Proton-Antiproton is more fun - matter-antimatter annihilation! As an antiproton is the antiparticle of a proton, they "annihilate" eachother when they meet - as will any particle meeting it's antiparticle. The particles don't just break up, they literally destroy eachother completely.

However, due to the fact that certain things must be conserved, such as energy, annihilation does have byproducts. Normally, they are turned into a high energy photon when they hit eachother - but when you try REALLY hard (insert LHC here), you can make them turn into all sorts of exotic particles upon annihilation.

Of note, this process is reversible, and a gamma ray can turn back into a particle and an antiparticle, depending on if it has enough energy to create them!

Re: Schedule

Posted: Fri Nov 27, 2009 5:27 pm
by Danny252
Friday Schedule (From LHCb Logbook):

Program for today, 27.11.2009:

Evening:
- Recover, re-establish circulating beams; if time left
revisit key beam parameters beam sizes, measure & correct
tunes, chromaticity, coupling

Night:
- kick response

Notes:
- "quiet" beam periods, with increasing protection, are
being considered (Sat and Sun nights ?, half hour periods),
depending on the progress with beams.

regards
Massi

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Page 1 claims beams should be starting in ~30 minutes (1900 CERN Time)

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EDIT: Moved back to 2030 (~1h15 from now)

Re: Schedule

Posted: Sat Nov 28, 2009 11:13 pm
by LHC_Insider
Danny252 wrote:Proton-Proton ... Nothing too special happens apart from seeing what they fall apart into (and then what these things do).

Proton-Antiproton is more fun - matter-antimatter annihilation!
I'm afraid you are incorrect here... An (anti)proton isn't just made up of the three quarks one gets told about at school. Think about this question: The proton has a net charge of +1, which means the three quarks must overall be of average positive charge. Like charges repel, so why doesn't the proton fly apart? It's not gravity; that is too weak. The answer is in the strong nuclear force. This is mediated by gluons, meaning that the three (anti)quarks (we call them valence quarks) in the (anti)proton are continually exchanging gluons. These gluons can split to give a quark and an antiquark, which then recombine to give the original gluon again; while it is on its travels.

So, you have these three valence quarks, and a sea of gluons, quarks and anti-quarks (yes, we call them the sea quarks). That means, when we collide (anti)protons together, there will always be interactions between quarks + antiquarks, quarks + gluons, and antiquarks + gluons. Note that interactions between quarks + quarks and antiquarks + antiquarks do not occur, but they do between gluons + gluons.

Re: Schedule

Posted: Sun Nov 29, 2009 12:16 am
by Danny252
LHC_Insider wrote:These gluons can split to give a quark and an antiquark, which then recombine to give the original gluon again; while it is on its travels.
Similar to Photons and Pair Production? Well, there's something I learnt today (along with the rest of your post, really!).

Though surely you get some antiquark-something interactions in proton-proton collisions, since their gluons would be producing quark-antiquark pairs as well?

Also, are those gluon-something interactions due to them splitting (e.g. when interacting with a quark, the antiquark from the pair created by a gluon does the interaction), or a seperate form of interaction?

Re: Schedule

Posted: Sun Nov 29, 2009 1:38 am
by Xymox
Wow....

That was interesting. Plus I learned a new term, Sea Quarks ! I would say the man knows his stuff.

Man, thats interesting and I learned a lot in just a paragraph of explanation. This forum could be really fun, I am glad I added it.

I cant wait till we get to the science phase. When discoveries are announced we can discuss them in the forum.

LHC_Insider, great name.. If you want a title under your name verifying you are a CERN member PM me. OR you can stay anonymous of course as well. To get the CERN title you need to send me a email from your NICE email address to verify you are with CERN.

Re: Schedule

Posted: Sun Nov 29, 2009 9:35 am
by LHC_Insider
Danny252 wrote:Similar to Photons and Pair Production?
Yes, it's exactly the same thing happening - a force carrier (more lingo: Gauge Boson) decays to two available states with the same net charge. However, the interactions describing quarks and gluons (QCD) are much more complicated than those describing photons and electrons (QED).
Danny252 wrote: Though surely you get some antiquark-something interactions in proton-proton collisions, since their gluons would be producing quark-antiquark pairs as well?
Sorry, I must have not been clear. When I said that there will always be interactions between quarks + antiquarks, quarks + gluons, and antiquarks + gluons, this applies equally to proton + proton and anti-proton + anti-proton collisions. That was my point.
Danny252 wrote: Also, are those gluon-something interactions due to them splitting (e.g. when interacting with a quark, the antiquark from the pair created by a gluon does the interaction), or a seperate form of interaction?
It's a separate form of interaction. Imagine a picture with one gluon coming in, and at a vertex two quarks emerge. Like this guy, with time running from R to L:

Image

Now imagine grabbing the free ('outgoing') end of one of the quarks, and moving it such that it is incoming, just like the gluon. You still have a three-point vertex, with two incoming particles (gluon+(anti)quark), and one outgoing particle ((anti)quark).