Giorgio Chiarelli is a particle physicist. His research activity has been based largely at the Fermi laboratory near Chicago, US, at the CDF experiment. In 1994-96 he actively participated in the discovery of the top quark and in the first measurements of that particle's properties. Later, after directing the construction of a part of the new CDF detector, he moved its research interests toward the search for the Higgs boson. Currently he is a INFN research director in Pisa, where he leads the CDF-Pisa group. In the most recent years he dealt with problems connected with the communication of science. Giorgio gladly accepted an invitation from Peppe Liberti and myself to recount the story of the first Tevatron collisions, which happened exactly 25 years ago. You can find an Italian version of this guest post in Peppe's blog.

Where were you on October 13, 1985?

Possibly you were not even born! Likely, if nothing special happened to you, you do not remember... Some of you might only remember that the crisis between Italy and US, due to the hijacking of the "Achille Lauro" and the confrontation of the US Delta Force with Italian Carabinieri had just reached its climax.

Not me. I do remember.

I was in the CDF Control Room, and as a young physicist of the Collider Detector at Fermilab, that night I was anxiously watching the display of our detector hoping to see the first proton-antiproton collisions at the Tevatron Collider. We had spent the Summer bringing the detector (still incomplete, yet functional) to life and day after day, shift after shift (that is: 8 hours in the control room watching screens and checking numbers on displays that now looks like prehistoric!) waiting to see protons collide with antiprotons. CERN was ahead of us and the
 collider was operational, but their energy (630 GeV in the center of mass) was lower than ours (aming to 2 TeV for summer-fall 1985 we settled for 1.6).

However hour after hour, shift after shift, day after day we had all being frustrated. Roy Schwitters (our leader) was unhappy, and so all of us down to the youngest like me. We were frustrated and yet we kept our faith and keep working.

My last shift ended at midnight. I was supposed to go home...and then there were only a few hours of attempts left. By 8 AM the whole 1985 run was to come to an end. The machine had to be shutdown to start the improvements on magnets and of the whole system...I was tired, still something drag me on. One of my co-shifters was Sergio Bertolucci. Now you all know he is the CERN Research Director, he has always been inspirational. Sergio suggested me to stay...we all were going to sleep for good in a few hours anyway.

I stayed.

And then, we had our last chance. Last shot for collisions. There were no journalists, no NYT, no televisions, there was no media. But suddenly we saw the first events showing up in our displays! After weeks of beam-gas collisions (that is collisions of protons-more unlikely antiprotons- with residual gas in the otherwise empty beam pipe) it was clear that those splashes of particles were something else.

The excitement was tremendous. Everybody was looking at screens and printing events. Bob Kephart was also trying to measure (let's say the number of tracks per unit rapidity -a measure of the angle with respect to the beamline) seen by the detector he built (the VTPC, Vertex Time Projection Chamber). The phone started to ring. Suddenly the whole tireness was gone. Everybody came by. Leo Lederman (back then Fermilab Director and not yet Nobel Laureate), Alvin Tollestrup (together with Roy our inspirational leader). Cathy Newman-Holmes came from home with her daughter (I think she was less than two years old) as well as many others who had been working hard for months and years and were willing to share the joy. When the beam (last shot!) was gone, the bubbling came in (it was not forbidden back then).

Somebody took a shot of Channel 13 (in jargon: the channel where the beam situation was on display on standard TV set) using a Polaroid and pasted it on the CDF logbook (a REAL book, not yet e). Then we all signed that page. You can see it on the right.

That night, with no google and no media, the Tevatron Collider Physics Programme started and a page in history of physics was written. It is still alive and well, after twentyfive years, and

I still have several prints of the event display, and a picture of the CDF logbook hanging in my office.