thank you so much for your appreciation. It is that kind of feedback that keeps me going, because I am not immune to flattery.

Cheers,
T.

Euclid, before we get a precision on the Higgs mass to the second decimal point in GeV, we will all be retired.

Cheers,
T.

thanks alot for the explanation. that must really have been a tough decision.

and in general thanks for this nice blog. the only quality hep blog around it you ask me.

chris

as an ignorant experimentalist, I think I have some answer for you. The limit set by LEP II was indeed slightly – but we are talking about tenths of a GeV – worse than what on average the experiments would have been expected to set (I will fetch the exact number later if I have time).
If the H is at 116 GeV, indeed LEP II with no energy increase would only see the “lower tail” of th resonance. But that would still mean observing an increased rate, which – with enough luminosity – is bound to be an observation in its own right. Maybe the mass would have not been determined with high precision, but the signal would have been established by running three times longer at the highest energy. The excess was a 1.7-sigma effect.

I think there is a sizable chance that indeed, the higgs is at 115 GeV.
But it is really just a toss-up.

Cheers,
T.

when the lep search for the higgs was abandoned, there were some candidate events – especially from aleph. if memory serves me well, the strict lower limit set by LEPII was therefore slightly lower than expected.

assuming that this was not a fluctuation but the onset of a resonance, would have increasing the luminosity been enough to establish the existence of a higgs? let’s say it hides really close to the limit – at 116GeV or so. and also assuming that the beam energy was maxed out already. wouldn’t it have been enough to reach the increasing side of the resonance and sample there with enough luminosity without ever going over the peak?

also, since i am at it, i really can’t resist asking an experimentalist who has some insight what their gut feeling is. was LEP close to discovery or was it just another (2 sigma?) fluctuation?

thanks alot in advance.

well, I do not think I would disrespect the CERN or LEP managements if I wrote in a blog what many still think (and beware, I am not among them), i.e., that closing LEP on the verge of a giant discovery was a giant blunder. I did not put it that way though, and I do not think along those lines. But you act as if I wrote something of that kind…. Blogs tend to mix correct information with sarcasm, fallacies, and random opinions, and as a blogger I am not a white fly. I still do not believe I went too far above.

I actually think that the CERN management did the right thing when they shut LEP down. Is that more clear ?

In any case, you write down things in your comment above as if CERN management was a good father of five, trying to make ends meet, and I was the neighbor criticizing the lease of a new car. It is not exactly a correct picture. CERN receives its money by the nations supporting it, and Italy – the country of which I am citizen and where I work – contributes with loads of funding. INFN, the institute for which I work, and which has built critical parts of the Atlas and CMS detectors (the 100 square meters of silicon sensors of the CMS detector, to give an example), in the face of it has kept hundreds of winners of positions on hold for the last three years. So when you write
“even though their own funding agencies have spent the last decade doing their best to contribute as little as possible to LHC construction”
you are close to being unfair to INFN… But I am not interested in criticizing you for that. As seen from different points on this planet, the drawbacks of a giant project appear different.

I myself do not have a permanent position yet, only because of the budget choices made by INFN and the italian government in their funding of science in Italy in the last few years.

So, yes, building the LHC is a giant effort. Yes, CERN did the best they could with the money we supplied it with. I do not think it is a matter of respect. Scientific decisions were made, and I subscribe to them.

Cheers,
T.

“while I think the points you both raise are sensible, I cannot help smiling… Being an internationalist, I have no idea why one should prefer an advancement of science if it is achieved in this rather than that set of geographical coordinates.”

Umm…. actually if you look back at my original post, its point was to make a request:

“So please treat the work of other laboratories and communities with respect; Europe has put 15 years of financial investment into making this a possibility (with limited financial help from outside, though HEP experimentalists from the entire world are lining up to join LHC experiments… about 6,000 in total when I last looked). CERN management has been planning for this since their first LHC studies 25 years ago, and many experimentalists have been working on these experiments for 15 years already to make them a reality. On the whole I think that they have handled this in a professional, considered, manner that I wish we could emulate on this side of the Atlantic.”

Rather than advocating that we “should prefer an advancement of science if it is achieved in this rather than that set of geographical coordinates” my point was exactly the opposite; I felt that the original article had been unfairly critical of CERN management, and the scientific leadership of the LEP experiments, and I was writing to ask that their contributions be shown the respect that they deserve. CERN has suffered severely under the burden of trying to build the LHC within its budget and without much international help [I visit the theory division there semi-regularly, and the deteriorating physical plant, staff cuts, overworked secretariat, reduced number of fellows, etc. are all prices they have had to pay to help bring the LHC to completion]. They’ve cut everything they reasonably could, and forward borrowed on their budget through 2010, in order to construct this facility that will be used by scientists worldwide. So it’s hard to let pass comments criticizing the necessary decisions that had to be taken to complete the LHC on a feasible schedule, especially since physicists from all over the world are now lining up to work there, even though their own funding agencies have spent the last decade doing their best to contribute as little as possible to LHC construction.

P.S. I remain of the view that the global health of HEP physics depends on having “a viable program on more than one continent.” European taxpayers can’t be expected to subsidize the field worldwide indefinitely. It’s clear from the LHC that it represents the limit of what is financially possible for one continent [and technically, LHC construction saturated the capacity for high-tech fabrication in some sectors of european industry]. The LHC and its luminosity upgrade will saturate the CERN budget for two decades [1995 - 2015]. To have the possibility of results from other than the LHC as well, on a timescale that will provide opportunities to young scientists entering the field now, it’s important that concrete plans for complementary facilities be undertaken in Asia and North America. Asia is taking the lead on this, with JPARC coming on line soon after the LHC, and plans for Super-BELLE in progress. I think that it’s time for North America to get its act together.

P.P.S. Just to be unambiguous, when I use the personal pronoun “we” in my posts above, “we” means the international community of particle physicists.

while I think the points you both raise are sensible, I cannot help smiling… Being an internationalist, I have no idea why one should prefer an advancement of science if it is achieved in this rather than that set of geographical coordinates.

Let’s just work in order to ensure that money keeps flowing and sensible political decisions are made in the future with respect to “how” (rather than the less interesting “where”) to continue pushing further our investigations in basic science.

Cheers,
T.

Just to be unambiguous, My comment was not a criticism of “the professionalism of FNAL”; indeed, given their restricted financial circumstances I am really impressed with the physics results now flowing from D0 and CDF. I just wish that the financial resources to develop the accelerator complex, and upgrade the detectors to
produce these results, had been provided to them a decade earlier.
For fifteen (15) years we have had the highest energy collider in the
world, in the Tevatron, and we are only really getting to explore its physics potential now, just when we are on the verge of LHC era.

At the time of the cancellation of the SSC project over a billion dollars a year (a Giga$) was being spent on its construction. If after its cancellation only 10% of that amount (a hundred million $ a year) had been retained and committed to developing the Tevatron collider program, both the facility and its detectors would have been much better much earlier, and it would have fulfilled its physics potential, much better much earlier. The experiments and the lab did the best with the resources which they were provided; one only wonders what they might have accomplished had that support been more generous and more timely.

What my comment did allude to was a national failure at the level of science funding and management in the north american program. We have never recovered from the SSC fiasco. We are now in the situation where our workhorse experiments will be shut on mass by the end of 2010 (at best). CLEO, BABAR, DO and CDF will all be memories in the next decade. The AGS particle program is already a memory, and funding for RHIC running is so restricted that a private donation from the mathematician and philanthropist James Simons [of Chern-Simons fame] was what funded a significant chunk of RHIC running last year. While working at CERN on the LHC is a fantastic opportunity for many of our young people, surely we owe it to them [and to the global health of HEP physics] to have a viable program on more than one continent.

Cheers,
T.

I agree with most of what you say, however let me make a few points.

1) I spend 80% of my research time in CMS, and I know that the LHC experiments are supposed to cover the whole low mass region in a couple of years of running. However, I also have worked for 15 years at the Tevatron, and I happen to know that one thing are MC predictions and another is the maelstrom of a hadronic collision environment and the extraction of results from it. So I am careful about the H->gamma gamma and H->tau tau channels providing a definitive result with “2-years worth of luminosity”. Also, lots of things can go wrong…
2) Although in my post I use 120 GeV as a reference value, I only said LEP II would have been able to see a Higgs with more running time (and maybe inventing some way to squeeze a couple more RF cavities here or there in the tunnel, although I heard swearing that the beams could not be kicked a mev higher) at 115 or 116 GeV, which is a few GeV above the 114 GeV limit set by the LEP II experiments. You of course know that quite a few of our colleagues who where in the LEP experiments believe they have been stripped of the chance of a discovery by the decommissioning.

Cheers,
T.

You wrote:
“The ATLAS and CMS experiments, I wish to remind you, will be in great embarassment if the Higgs mass happens to be just a few GeV higher than what LEP II excluded. And that not because they would be taking data next year only by virtue of having shut down the LEP II experiment only months short of discovering the Higgs boson:…”

I think that this statement is inaccurate, and unfair to the management of CERN, and the scientific leadership of the LEP experiments. You should remember that unlike hadron collider exeriments, which are essentially broad band beams of quarks and gluons, LEP annihilated electrons and positrons, and in each event essentially dumped the entire centre of mass energy into the produced final state. This means that while at the Tevatron your limits on the Higgs are at a small fraction of your nominal centre of mass energy, and can be improved by running with larger statistics, the LEP II limit was essentially at the end of their kinematic range [remember that it was an H + Z final state, so that you run out of energy at the sum of those masses]. To produce a 120 GeV Higgs, the threshold for production would be at 211 Gev, and you need to get somewhat over the root s threshold turn-on to have any rate. If I recall correctly they ran up to about 208 GeV [by putting as much power into the RF as possible]. Given this limitation of their root s, I think that the LEP limit of 115 GeV is an outstanding accomplishment. It is also completely clear that given their limitation on root s, there is no possible way they could have discovered a 120 GeV Higgs regardless of how long they ran.

This is one of the reasons why CERN management chose to terminate the LEP program when it did. And by so accelerating the timetable for the LHC it brings us closer to the day when we’ll be sure to have data in hand that will be able to convincingly decide the issue. [For reference, if LHC produces its expected (reduced!) luminosity during the first two years of running, that will be enough to enable 5 sigma discovery of a Standard Model Higgs over the entire mass range where the Standard Model makes sense. And yes, that is one of the reasons that both ATLAS and CMS have such high performance electromagnetic calorimetry, but if you look at the search channels in the 120 GeV mass range I believe that channels with Higgs -> tau + tau are also statistically important. So important work will have to go into understanding the detectors and the data set in those first two year of running, but barring unforseen disasters we can resonable look forward to the prospect of a 5 sigma discovery by the time of ICHEP 2010].

So please treat the work of other laboratories and communities with respect; Europe has put 15 years of financial investment into making this a possibility (with limited financial help from outside, though HEP experimentalists from the entire world are lining up to join LHC experiments… about 6,000 in total when I last looked). CERN management has been planning for this since their first LHC studies 25 years ago, and many experimentalists have been working on these experiments for 15 years already to make them a reality. On the whole I think that they have handled this in a professional, considered, manner that I wish we could emulate on this side of the Atlantic.