First Collisions for the LHC

by Nancy Atkinson on November 23, 2009

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Screens showing two beams in the LHC.  Credit: CERN

Screens showing two beams in the LHC. Credit: CERN

Two beams circulated simultaneously inside the Large Hadron Collider for the first time today, allowing for the first proton-proton collisions to take place. “It’s a great achievement to have come this far in so short a time,” said CERN Director General Rolf Heuer. “But we need to keep a sense of perspective – there’s still much to do before we can start the LHC physics program.”

The beams crossed at points where various detectors are stationed. The beams were made to cross at point 1, where the ATLAS all purpose detector is located, then at point five at the CMS (Compact Muon Solenoid) detector. Later, beams crossed at points 2 and 8, where the ALICE (heavy ion detector) and the LHCb (looking for heavy particles containing a bottom quark) are positioned.

The first collisions are allowing operators to test the synchronization of the beams.

“This is great news, the start of a fantastic era of physics and hopefully discoveries after 20 years’ work by the international community to build a machine and detectors of unprecedented complexity and performance,” said ATLAS spokesperson, Fabiola Gianotti at a press conference today.

“The events so far mark the start of the second half of this incredible voyage of discovery of the secrets of nature,” said CMS spokesperson Tejinder Virdee.

“It was standing room only in the ALICE control room and cheers erupted with the first collisions” said ALICE spokesperson Jurgen Schukraft. “This is simply tremendous.”

“The tracks we’re seeing are beautiful,” said LHCb spokesperson Andrei Golutvin, “we’re all ready for serious data taking in a few days time.”

The first collisions come just three days after the LHC restart. Since the start-up this weekend, the operators have been circulating beams around the ring alternately in one direction and then the other at the injection energy of 450 GeV (gigaelectron volts). The beam lifetime has gradually been increased to 10 hours, and today beams have been circulating simultaneously in both directions, still at the injection energy.

Next on the schedule is an intense commissioning phase aimed at increasing the beam intensity and accelerating the beams. If everything goes as planned, everyone at CERN hopes to obtain good quantities of collision data for all the experiments’ calibrations by Christmas, when the LHC should reach 1.2 TeV (terraelectron volts) per beam.

Source: CERN

About 

Nancy Atkinson is Universe Today's Senior Editor. She also is the host of the NASA Lunar Science Institute podcast and works with Astronomy Cast. Nancy is also a NASA/JPL Solar System Ambassador.

DrFlimmer November 23, 2009 at 2:34 PM

You cannot hide forever, Higgs.

Kevin November 23, 2009 at 2:39 PM

We gonna getcha, Higgsy!

van_falen November 23, 2009 at 3:46 PM

“when the LHC should reach 1.2 TeV (terraelectron volts) per beam”

you mean teraelectron volts.

Astrofiend November 23, 2009 at 4:09 PM

Sweet baby Hehsoos! Great to see that everything is running along smoothly for the moment. Just hurry up and ramp up the collision energy! I wanna see multi-TeV collisions damn it! I am literally frothing to see what physics comes out of this thing…

Lawrence B. Crowell November 23, 2009 at 6:15 PM

It might be a little while before we get to frontiers of physics energy. A bit of calibration is needed and the beam luminosity will doubtless be worked on to get that up to maximum.

LC

Astrofiend November 23, 2009 at 10:10 PM

I suppose I can wait. *sulks*

Mr. Crowell, if you were a betting man, and I’m betting that you are a betting man, what would your money be on to see come out of this thing in the next 5 (or so) years? The Higgs most probably, but what about in terms of extensions to the minimal Standard Model? Multiple Higgs’? Supersymmetric particles? Any thoughts?

What do you hope it will shed light on?

damian November 24, 2009 at 3:29 AM

In the Salivating hype surrounding the LHC. (wipes drool) I Cant help but be reminded of Douglas Adam’s Supercomputer; Deep Thought.

“It takes Deep Thought 7½ million years to compute and check the answer to the ultimate question. ”

Sadly it needed a bigger computer to actually find the right question. :)

Somewhere in the back of my mind sits a uncomfortable question; how much can we really find out by smashing thing up? (particle smashing in general) We are observing the detritus of an atomic catastrophe in the hope that what remains will reveal the workings of gravity.

Seems to me that gravity is an energy that binds and brings order, and here we are trying to work it out by annihilating the particular arrangement that it forms.

However I am as eager to learn as others. High hopes for a renaissance of thought and ideas to flow from the discoveries. :)

Damian

Lawrence B. Crowell November 24, 2009 at 6:21 AM

If I were to bet on what the LHC were to find, or base a higher probability on certain physics, I would say that certainly the Higgs field or particle is at the top of the list. The HIggs field is really just a Landau-Ginsburg potential for a process which changes its properties. It is generic to a wide range of processes from Curie point on ferromagnetic behavior, superconductivity, superfluidity, Landau electron phases and so forth. The Higgs field is simply the application of this physics to particle physics. In effect it almost has to be there!

The next would be some signatures of supersymmetry, or N = 1 supersymmetry. Signatures of higher N =2, 4 or even 8 would be fantastic, in particular up to N = 4. In the N = 1 SUSY some form of low energy Fayet-Iliopoulos spontaneous broken SUSY.

This at least covers the particle physics first worked up in the 1960-70s time frame. If we can detect N = 4 SUSY (quaternionic or 16 supersymmetries in the Clifford algebra CL_{16}), most likely in a broken symmetry phase, we would be in great shape! I think the chances here are somewhat around 1/3rd odds. Now combine that with the prospect we would measure small amplitudes for black holes. If this happens we would be potentially measuring signatures of a crucial aspect of quantum gravity in superstring/M-theory. This would mean that at high enough energy, say above the mass scale of the Higgs field, quantum fields assume more conformal structure (though probably in a broken form) that has a duality to anti-de Sitter spacetime symmetries and quantum gravity.

This latter stuff I really hope we find, and there are some indicators of this from data recorded at the Brookhaven RHIC. Of course at this point we are getting a bit out on a limb, and data for this may be very sparse. Given the 10^{11} p and p-bars per beam ramp or pulse and about 10^6 channel productions at lower energy per even this amounts to a pentabyte per second of data. It is astounding that this sort of massive computer capability exists, along with the massive particle tracking programs triggered to the various detectors. The four detectors are Alice, Atlas, CMS and LHCb, which are set to look for specific physics, and these record a vast amount of data per p on p-bar beam. Finding evidence of quantum gravity will be hard, but not impossible.

Of course there are other questions to be answered. In particular does quantum chromodynamics (QCD) have a higher family structure, say a fourth quark multiplet? There are some technicolor QCD theories about higher family structure. This might also mean there is a higher mass multiplet of leptons as well, though those should have been detected if they exist. Of course there is also the unexpected, or something which crops up which unanticipated.

LC

Lawrence B. Crowell November 24, 2009 at 9:46 AM

The CMS (compact muon solonoid) detector people had a bit of a party time yesterday.

http://cmsdoc.cern.ch/cms/performance/FirstBeam/cms-e-commentary09.htm

LC

chrismannn November 24, 2009 at 12:07 PM

Dearest Mr Crowell,
the main word that comes out of your post is ‘hope’… as I simply do not have a hope in hell of understanding a word of your superbly eloquent expressions.. but please, carry on.. im a big fan!

Aqua November 24, 2009 at 12:55 PM

Expect a miracle…

Lawrence B. Crowell November 24, 2009 at 1:46 PM

I made a bit of an error above . I meant to write CL(8) not Cl(16).

One of the thing that the LHC might find with respect to supersymmetry are some predictions of the minimal superymmetric standard model of electroweak interactions. The production of Z neutral gauge fields by a flavor changing process, say a strange quark from a down quark d–> s by the exchange of a “bino” and a superpair s-down and down will be a confirmation of a minimal supersymmetric gauge interaction.

LC

Olaf November 24, 2009 at 3:17 PM

Lawrence B, I do not understand everything you explain, but keep on posting since it forces me to learn it too :-) And it is very interesting.

Astrofiend November 24, 2009 at 5:30 PM

Excellent. It’s going to be a thoroughly exciting time to be sure, and good to hear a few thoughts from someone who is getting down and dirty at the coalface, so to speak.

Lawrence B. Crowell November 25, 2009 at 6:26 AM

The Higgs field is a strange field in a way. The potential for the field, H is U = aH^2 – bH^4 (a, b = constants), which has H = 0 and H = sqrt{a/b} are solutions to U = 0. This double valuedness is what is involved with conferring a mass to particles. A gauge field has a vector potential, A, which rotates according to a certain algebraic symmetry. It also makes momentum operator p –> p + iA. The kinetic energy term for the Higgs field is T ~ p^2, which due to the action of the Higgs field creates a quadratic term in A which is in a broken phase at the minimum H = sqrt{a/b}.

This leads to an interesting conundrum. which lead to supersymmetric standard model. The Higgs field has a quadratic divergence which is unfortunate. The field propagator of a fermion is G(x,x’) = 1/(x – x’ – ie), and if we integrate this you get a logarmithmic term, which gives the mass-energy of the fermion. Hence this is logarithmically divergent, which is easily renormalizable. So a Higgs field that couples to the fermion field f and its conjugate f-bar according to an interaction term in the Lagrangian ~ (f-bar)Hf, will carry the Higgs divergence as well. The existence of the superpartner to the Higgs and the fermion field at about the same mass scale results in the cancellation of these divergences.

So as the machine is calibrated and beam luminiosity increased over the next year we should start to get some new particle physics by 2011. We should certainly get the Higgs field, and I think with nearly the same confidence we should get signatures of Fayet-Illiopoulos broken phase of supersymmetry — at least at the N = 1 level of supersymmetry.

LC

Lawrence B. Crowell November 25, 2009 at 1:40 PM

I just read a little report which indicates the LHC will exceed tevatron energy before the year is out. It looks like we may get some new physics fairly soon. I expect a trumpet sound over signs of the Higgs field by the end of 2010.

LC

Torbjorn Larsson OM November 25, 2009 at 2:56 PM

a higher family structure, say a fourth quark multiplet?

AFAIU there are indirect evidence that no more than 3 generations exist. IIRC a 4th generation must have an inconsistently grossly huge neutrino mass, lower masses have been ruled out somehow. (From ~ eV to ~ GeV or something like that.)

So if we are discussing ways to bet, I’m out of that one. :-D

Lawrence B. Crowell November 25, 2009 at 3:10 PM

I too doubt there is a 4th quark generation, but getting the data will firm that up some. The problem is that if there do exist 4th familiy of quarks the effective heat capacity of the universe in the inflationary period and immediately after would be larger. This would suppress the D production in the early universe from what we observe.

LC

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