The LEP Collider Will Be Closed Down

mukund writes "The Large Electron-Positron (LEP) collider will be dismantled soon, as this article on BBC News reports. The LEP is the world's largest particle collider and is built inside a 27km long tunnel. The collider has been used to confirm the existence of the Higgs particle unsuccessfully. A new project to build another larger collider is on the way. The article says, "According to commentators, whoever finds the Higgs first will probably win a Nobel Prize.""

Comments

Fermi's Tevatron, Higgs particle, sci note, data

[arete]

I'm working at Fermi in production of the RunII CDF detector (as an engineer, not a physicist) and from what I hear, taking LEP down means we are nearly assured of the Higgs before LHC comes up - unless it is truely impossible at Tevatron's size, which seems unlikely, currently. Things here seem to be going quite well, imo.

To give a (very) rough explanation of the Higgs: when you smash things together with very high energies, you get a huge explosion (huge, considering it was started by one proton and one antiproton) and all sorts of fragments are produced.

However, we have to measure these fragments using very odd means, because it is mostly impossible to directly measure most of these things... you can only measure the effects they have on the relatively normal stuff we can build a detector out of. (if you build it out of these things, the detector would vanish in much less than a second...) So the more "normal" fragments are relatively easier to measure, because they interact more with the more normal detector.

In recent high energy physics history there has been a string of these things, Higgs is the next.

Someone said they first saw sci notation in 93, and I'm amazed. I'd heard in Junior High earlier than that... or did you mean something else.

Btw, Fermi has a significant linux community. Also, (from a bad memory and this isn't my department but) they have to filter the incoming data in realtime, keeping only the most interesting 1/millionth of it - and that data alone is a couple CDs/second worth of data. Lots o' bandwidth there...

The Scoop from inside LEP

[tbo]

Here's an email that's been circulating through the physics department at my university. It does a pretty good job of explaining what's up with LEP, and why it would be nice to keep it going for just a little while longer. The short of it is that they think they've found Higgs, but need a bit more data to be sure.

Anyway, here's the email:
-------------------

Hi,

Since we've been getting a lot of enquiries about the reports of a Higgs
Boson 'discovered' at LEP, I thought I'd give you more info.

There are 4 experimental groups taking data at the LEP electron-positron
collider. On Friday Nov.3, the each of the 4 experimental groups
presented our analyses to the LEPC (LEP Experimental Committee) i.e. the
Research Board, at CERN. And one analysis combining the results of all 4
expts was also presented.

The LEP experiments were all scheduled to stop data taking on Nov.1, after
over 11 years of experimental data taking -- probing & testing of the
Standard Model to unprecedented precision. Stopping and dismantling LEP is
necessary before the installation of the LHC accelerator and detectors may
begin, as LHC uses the LEP tunnels. (LHC is the Large Hadron proton-proton
Collider, which has discovering the Higgs Boson as a centerpiece of its
physics program)

LEP reached the highest energies ever this year, with 208.2 GeV as the
highest energy reach possible, (limited by the number of RF cavities) but
the accelerator is so unstable at this energy that less than 4% of this
year's data was taken up there. The bulk of this year's data was in the
205-207 GeV range.

Every experiment sees "Higgs candidates". These are events which look like
e+ e- --> Higgs ZBoson, with each the Higgs and ZBoson subsequently
decaying. For 3 of the 4 of the expts, the "candidates" seen are
absolutely and entirely consistent with what's expected from known
Standard Model processes i.e. background. ( 2 Z's, 2 W's, and other
processes which can look very similar to ZH)

3 of the 4 LEP groups have completed analyses which result in upper limits
on Standard Model Higgs masses. 1 (ALEPH) reports a 115 GeV Higgs with a
significance equivalent to a 3.4 sigma excess over background
expectations. When all 4 expts combine our data, this diminishes to a 2.9
sigma effect for a 115 GeV SM Higgs boson.

Our UBC group is a part of the OPAL experiment, one of the four expts.
OPAL rules out a Standard Model Higgs boson at masses under 208GeV at 95%
confidence level. Our OPAL bottom line can be seen in a talk by Arnulf
Quadt of OPAL, at the LEPC presentations:
http://www.physics.ubc.ca/~janis/arnulf.ps If we are to interpret our
results in terms of a Higgs Boson at 115 GeV, we have a 1.3 sigma excess
over background processes at this mass. We have a 2.6 sigma effect at 107
GeV. You give us a mass, we can tell you if we see an excess above, or
depletion below the background expectations. (the 2.6sigma at 207 GeV is
the largest deviation from expected background at high energies)

The combined 4 experiments talk at LEPC by Peter Igo-Kemenes, incidently
also an OPAL collaborator, (emailed to you by Douglas) may be seen at
http://lephiggs.web.cern.ch/LEPHIGGS/talks/pik_l epc_nov3_2000.ps

You can see the ALEPH LEPC talk at:
http://alephwww.cern.ch/ALPUB/seminar/lepc_nov00 .pdf

Judge it for yourself. I'd say we are in an interesting situation and it
woudl be shame to stop the LEP program now with these interesting hints
from ALEPH. With another year of data taking at LEP (and hence a year
delay in the LHC) we would be able to confirm or refute the existence of a
115 GeV Higgs at a honking 5 sigma level... what we usually refere to as
the "discovery level" It would be very exciting if we could indisputably
discover the Higgs Boson. But I would say we do not have a Higgs Boson at
this time.

CERN has not issued any press releases on this matter (as of Saturday
evening). Only the LA Times has. Even NY Times has not.