Closing Comments

Nigel Glover, IPPP

LHC Startup, Coseners House,

13 April 2007

Lesson from History?

• From the Tevatron to the LHC there is a large increase in phase space and a big increase in cross sections – by a factor of 100-1000

• The Tevatron has saturated the search boundary at a level well below the LHC initial reach

Start-up Physics 20080.1-1 fb-1

Channels Events to tape for 100 pb-1

(per experiment)

Total statistics from previous colliders

W -> μν ~106 ~104 LEP ~106 Tevatron

Z -> μμ ~105 ~106 LEP, ~105 Tevatron

tt -> Wb Wb -> μν+X

~104 ~104 Tevatron

QCD jets ET > 1 TeV

> 103 -

Gluino pairs m = 1 TeV

~50 -

Year 1 data will most likely be an improvement!

Even if it takes a while to do the sophisticated analyses,

some studies will be done very quickly

Lesson from History?

• Jump in available energy similar to that from ISR (63 GeV) to SppS (540 GeV)

• Technically innovative accelerator – antiprotons

• Startup of LHC might be more

like SppS than tevatron

• Its reasonable to expect to discover lots of new phenomena!!

Startup of SppS• Summer 1981

First collisions between protons and antiprotons

• November 1981First data taking at low luminosity (best luminosity 5.2 x 1027 cm-2 s-1)UA1 and UA2 able to look at jets

• Beginning 1982, accidental damage to the UA1 detector (dirty compressed air supply contaminated the delicate components of the inner detector)

• First physics run starts October 1982 until December 1982 when the accelerator was switched off for two months.

Startup of SppS• October 1982

First physics run for UA1 and UA2, peak luminosity 5x1028 cm-2 s-1 integrated L ~ 20 nb-1

It took only a few weeks to be convinced that they had found the signature of a W particle decaying into an energetic electron and a neutrino, carrying energy but invisible.The discovery of the W events was announced on January 25 1983

• Fermilab Director Leon Lederman was impressed by “the speed at which data was analysed and physics achieved out of detectors of unprecedented sophistication, viewing collisions of novel complexity”.

• 12 April 1983 second physics run, peak luminosity 1.6x1029 cm-2 s-1 to provide 100 nb-1 by June

• On 1 June 1983, the formal announcement of the discovery of the Z particle was made at CERN

W discovery

Z discovery

Missing energy!

Startup of SppS cont.Jets had already been seen at PETRA and were easily identified

• 23 December 1982“We measure the inclusive jet cross section with transverse energy up to 60 GeV and the two jet mass up to 120 GeV/c2”UA1 collaboration, PLB 123B, 115 (1983)

• 17 August 1983A more detailed study

– out to ET~100 GeV UA1 collaboration, PLB 132B, 214 (1983)

jet “discovery”

More excitement!• Electron plus missing energy

plus jet events interpreted as top quark by theorists 15 February 1983

“The MT(eν) distribution of electron events with jets recently observed in the UA1 experiment at CERN may be interpreted as being due to a

t-quark with mass 25 to 40 GeV”

Barger, Martin and Phillips, PLB 125B, 342 (1983)

“top” discovery

UA1

Theorists not talking to experimenters!

and more excitement!• Experimental evidence for

Monojet events“We report the observation of five events in which a missing transverse energy larger than 40 GeV is associated with a narrow hadronic jet. We cannot find an explanation for such events in terms of backgrounds or within the expectations of the Standard Model”UA1 collaboration, PLB 139B, 115 (1984)

“susy” discovery

Monojets!

Experimentalists not talking to theorists!

Tevatron startup in 1987• SppS provided a big jump in kinematical phase space, clear

signatures and a new experimental tool – missing energy

• At the Tevatron, the increase in beam energy – and hence cross section - was too small to have an immediate impact

• The top quark cross section was more than 10 times bigger, but UA1/UA2 had already used high luminosity to explore much of accessible energy range – it took more than two years for CDF to improve the SppS top mass limit

• Eventual top discovery was anticlimax!

– Although we did learn the importance of b tagging

Outlook• The LHC is entering a significantly new energy regime

– exciting times are ahead (hopefully in 2008)

• Lot of work still to be done – and many impressive achievements, but should still expect setbacks

• Based on previous experience with the SppS and Tevatron,

- results may come out of Year 1 data sooner or later than expected!- jets/leptons/ETmiss may or may not come first…or not

• Analyses with complicated final states (e.g. top quarks) may take time to understand, and the Higgs search requires luminosity

Perhaps one of the first papers…

1 August 2008

De Roeck

And Maybe…

De Roeck

we can still dream of new physics – most likely in the strongly interacting sector