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By Tommaso Dorigo | April 30th 2009 01:36 PM | 18 comments | Print | E-mail | Track Comments
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About Tommaso Dorigo

I am an experimental particle physicist working with the CMS experiment at CERN and the CDF experiment at Fermilab. In my spare time I play chess, abuse the piano, and aim my dobson telescope at... Full Bio

2008 was a horrible year for the Large Hadron Collider. Just nine days after an extremely successful, highly publicized start-up on September 10th, when hundreds of reporters gathered at CERN to follow the protons as they ventured sector by sector to manage a full turn of the 27 km ring, a stupidly crafted electrical connection failed in sector 3-4 of the machine. This brought above criticality a superconducting solenoid, vaporized six tons of liquid helium, and damaged 53 expensive magnets in the sector with a powerful blast.

From a public-relation point of view, amassing a huge firing squad of reporters who knew next to nothing about the LHC project until then, coalescing like a giant focusing lens the eyes of the media around the world on the uneventful walk of proton beams around the ring, was a huge success for just one week, but it then clearly became a failure of gigantic proportions. The event would have stayed a huge success if things had ran smoothly for a while, but "LHC" still meant something to the billion of people who had been exposed to the startup event, when news about the blast made it around the world.

The damage has resulted in a delay of exactly one year in the schedule of the LHC and the four experiments waiting to take data along the ring. One year might not look like a tragedy for a project whose first technical design was laid out twenty years ago. However, if you are one of the physicists who worked full time at the construction of those monstrous detectors, hoping year after year that soon you would finally get a chance of analyzing the amazing collisions that the accelerator produced, and seeing the start of data taking being moved further without end, the setback is really awful. And if you are one of the Ph.D. students who counted on producing a thesis worth something with real data in their graphs, this may configure as a catastrophic event for your career.

Worse still: the CDF and DZERO experiments at the Fermilab Tevatron, the glorious 2-TeV proton-antiproton collider in operation since 1987, are collecting data at a steady pace, and are producing one groundbreaking result after another. Those who have been investing most of their career in building detectors that could discover the Higgs boson at the LHC have now reason to fear that the trophy will be collected there, while they will be watching powerless from the gallery.

But things seem to finally be back on track. Rolf Heuer, Director General of CERN, issued today a statement which I wish to paste here, because it seems to finally spell good news for the LHC, for high-energy physicists worldwide, and in general for all of us who love science regardless of what language is spoken by the next Nobel prize winner.

Here are a few excerpts of Heuer's message:

The 53rd and final replacement magnet for CERN's Large Hadron Collider (LHC) was lowered into the accelerator's tunnel today, marking the end of repair work above ground following the incident in September last year that brought LHC operations to a halt. Underground, the magnets are being interconnected, and new systems installed to prevent similar incidents happening again. The LHC is scheduled to restart in the autumn, and to run continuously until sufficient data have been accumulated for the LHC experiments to announce their first results.

[...] With all the magnets now underground, work in the tunnel will focus on connecting the magnets together and installing new safety systems, while on the surface, teams will shift their attention to replenishing the LHC's supply of spare magnets.

In total 53 magnets were removed from Sector 3-4. Sixteen that sustained minimal damage were refurbished and put back into the tunnel. The remaining 37 were replaced by spares and will themselves be refurbished to provide spares for the future.

[...]systems are being installed to monitor the LHC closely and ensure that similar incidents to that of last September cannot happen again. This work will continue into the summer. Finally, extra pressure relief valves are being installed to release helium in a safe and controlled manner should there be leaks inside the LHC's cryostat at any time in the machine's projected 15-20 year operational lifetime.

CERN is publishing regular updates on the LHC in its internal Bulletin, available at http://www.cern.ch/bulletin, as well as via twitter and YouTube at http://www.twitter.com/cern and http://www.youtube.com/cern.

It only remains for me to say that despite my sound strategy of betting on both horses until now, I am now really starting to root for the LHC to start delivering what it has promised us. You have to know that I belong both to the CDF collaboration at Fermilab and to the CMS collaboration at CERN, and although most of my research time has been devoted to CMS during the last few years, my heart has been beating for CDF for so long that I cannot really help wishing that glorious experiment all the successes it deserves. But enough is enough: LHC has been a huge investment, and it is time to see whether we have made the right choice!

Comments

Rick Ryals's picture
YAY!... but I'm having a little trouble with your technical terminology; a stupidly crafted electrical connection... ;)

The delay has been a pity, and the PR was poorly handled - especially the secrecy originally surrounding the investigation of the accident - but ultimately I wonder if it will make all that much difference. The recent tighter CDF limits indicate that the Higgs, if it exists, is not in one of the optimum energy ranges for discovery by the LHC, so it looks as though we were always in for a long slog.

Now that the Obama administration has opened the funding tap for HEP in the US, it looks like Fermilab will have a life after 2010. Nothing could be more healthy and productive for HEP than to have Fermilab and Cern racing to be first to uncover the Higgs.

Competition has always been the lifeblood of HEP research. And I have to admire your foresight in having a foot in each camp!

dorigo's picture
Hi DB,

sure, there is again hope in a future of US HEP. The Tevatron will be likely to run in 2011 too, which will mean results coming out steady until 2013 at least, and then trickling down for a few more years out of the dismissing CDF and DZERO collaborations. In earnest, it makes no sense for the Tevatron to run once LHC starts working fine; but this might be still a few years ahead in the future...

Staying in CDF was a no brainer when I joined CMS. CDF is such a wonderful experiment! I am proud to be part of it, and I never get tired of stressing that it is the longest lasting physics experiment ever. Even if my last CDF data analysis is more than one year old, I am still active there. For one thing, I am a member of the Spokespersons Publication Review Group, a committee which reads every draft of every paper that CDF is about to publish, and gives a green light to them after careful dissection. Secondly, I am also in charge of specific analysis reviews -the last one is due to come out in a month, and it will be a very nice surprise.

Cheers,
T.

Hank's picture
Statistically, there is a chance in the next 2 years (better than coin flips though not great) our missing SM friend can be found in IL.   The US did not much want anything to do with the LHC - SSC being too recent and painful a fiasco - but world leadership in finding that pesky boson would mean a 100% chance of the US building the ILC that will be needed to interpret whatever is found.

Hi Tommaso,

pay close attention to this announcement:

http://resonaances.blogspot.com/2009/05/all-eyes-on-denver.html

"Tomorrow (Saturday) morning, the FERMI/GLAST collaboration is going to announce their first results at the APS meeting in Denver. FERMI/GLAST is a satellite cosmic gamma-ray observatory, but it also has capabilities to measure the electron+positron spectrum."

Please, do not forget to comment on the results!

Cheers,

Daniel.

One more thing. Can you ask anyone why no one talks about color charge for black holes?

Hfarmer's picture
The classical answer is that Black holes are purely gravitational phenomena.  The strong force plays no role.  That's not to say that the surface of a black hole cannot be charged. 

Look in any standard text book on the subject and you will find a theorem in black hole physics called the "no hair" theorem.  This theorem basically says that black holes have only three externally observable characteristics, mass M , surface charge Q, and angular momentum L. 

So if a Black hole can have an electromagnetic surface charge why not a chromodynamic surface charge?  This is so because, as far as anyone knows, individual quarks do not exist.  They exist in combinations that will have no chromodynamic color.  Either a quark and antiquark, or a triad of quarks.  These particles will fall into the black holes in these colorless forms, so the black hole can't gain any net chromodynamic charge.

It should also be noted that any real black hole the hole itself is likely to be neutral (Q=0) as it is constanly pulling in new particles of all kinds of EM charges. 

dorigo's picture
Thank you for answering for me Hontas. It only remains for me to say that the only case I can think of when the question is relevant is when one produces black holes at a hadron collider, say the LHC. This is possible if the scale of quantum gravity is smaller than the total CM energy of the machine, and if certain other conditions apply. In that case, the initial BH is indeed color-charged, and it undergoes a phase called "balding". There is a talk by Steven Giddings on the matter, which I listened to in London a couple of years ago, and which you can read about at http://dorigo.wordpress.com/2007/07/07/steve-giddings-on-black-hole-prod...

And thank for the reminder about Glast. They will pinpoint the pulsars responsible for the Pamela excess ;-)

Cheers,
T.

Hfarmer's picture
It is quite correct to say that a black hole created at the LHC or in some hypothetical much stronger collider, which engorged just a quark or two out of a hadron, could have a net color charge.

The production of such a black hole if it is possible could be a path to producing free quarks.  For the hole to have a net color charge, that means that somewhere there would have to be a hadron stripped of one or two quarks.  The energy released in breaking that bond could blow the hadron apart.  Or would it?

I restricted my answer to classical and generally accepted theories.  If we are going to talk quantum gravity and quantum black holes.  Without going to far into any particular theory of (non string/Mtheory based, which I understand the talk you attended was) quantum gravity.  The question is not so much the center of mass energy, it is the center of mass density.  There is also a well accepted reason to think that there will be no such occurence at any earthly facility in the foreseeable future.  Consider the following.

E=hc/l  h is Planck's constant, c is the speed of light and l is the wavelenth of the light.

Rs=2GM/c2  That is the Schwarschild radius formula.  For simplicity h and c will be set equal to one.  E=1/l  Rs=2GM 

Now set the wavelength of the light equal to the Planck length.  Which in these units is just lp=√G .  Then E=1/√G .   We learned from Einstein that E=M.   The Schwarzchild radius is Rs=2G1/√G=2√G  twice the Planck length.   What this shows is that the critical density for creating a black hole is roughly equal to one planck energy per planck volume.  That is 1.22x1019 GeV in a volume of (1.616x10-35 m)3 .  The enegery density of an average collision at the LHC according to this paper, is only 200GeV/fm.  Which is no where near enough.




Thank you, but what about when a black hole just eats one of the quarks and the anti quark escapes? This is not possible in normal conditions because when you try to break apart them, you will give enough potential energy for another pair of quark/anti quark to appear and glue to the old pair and so you the net color charge will be 0.  But, when one of quarks crosses the horizon,  energy won't be added to the pair, the black hole won't have a zero net energy.

But, if I follow an analogy with the EM field, a glue string will remain tying the black h0le with the quark or anti quark.  So, because of the virtual particle/anti particle constantly produced, may I say that a black hole is virtualy haired? On average, the color charge will be zero, but at a precise instant and looking very closely to the horizon, it won't.

dorigo's picture
Hi Hontas, you are wasting a lot of electrons to try and convince me of something I am already quite convinced. I do not buy the fact that the quantum gravity scale is at 1 TeV. That is why I do not believe we will see any of the signatures Giddings (and Randall here) discussed recently.

Cheers,
T.

Rick Ryals's picture
Tommaso, Db said that tighter CDF limits indicate that the Higgs is
not in one of the optimum energy ranges for discovery by the LHC.

Can you elaborate on this, because I was really hoping for a quick return on my bet!... ;)

How much more difficult, (What is the process now?), and how long do you think is a reasonable amount of time, or is this even something that you can say?

And have you heard anymore about GLAST?

dorigo's picture
Rick, all electroweak fits, together with the direct bounds by LEP II and now the Tevatron, indicate that the SM Higgs boson has a mass between 115 and 135-140 GeV. The upper one is not a strict bound, however.

In that mass range the Higgs decays preferentially to pairs of b-quarks, which are almost unobservable at the LHC and only observable with a lot of trouble (and data) at the Tevatron. In that mass range the LHC has to resort to the h->tau tau decays, which are less frequent but a bit easier to find (not much though). More clean is the h->gamma gamma decay, which however is only happening once or twice every thousand decays.

Atlas and CMS have recently produced discovery reach plots for the Higgs, by performing pseudo-analyses and combining many channels into a single result. Those indicate that the region 115-135 GeV will take time and data. You will have to wait.

Cheers,
T.

PS Yes, I have seen the new Glast data...

Rick Ryals's picture
Thank you Tommaso.  Have there been previous searches in this range?

dorigo's picture
Sure, the Higgs has been sought in all possible final states in all meaningful ranges. When you look at a combined limit, it is a combination of dozens of different searches. Please refer to the stuff in the old blog you can access via the tag cloud under "Higgs boson"...

Cheers,
T.

HI TOMMASO!!!

THE PAPER ON FERMI 20-1000GEV SEARCH WAS RELEASED!!!!  :D

http://arxiv.org/abs/0905.0025


dorigo's picture
Yes, I saw it this morning, and I also saw the HESS paper, on the same spectrum.

Cheers,
T.

- and btw, I see nobody around here that could answer your question. I have a person in mind but have not had a chance to meet him yet.

T.

We shouldn't start LHC anyway, until security analysis of main potential risks will be completed - or we are just tickling the dragon's tail.
http://aetherwavetheory.blogspot.com/2009/01/awt-and-lhc-risk.html

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