VLHC Experiments: Overview of the Very Large Hadron Collider

1. VLHC Experiments: Overview Very Large Hadron Collider Dmitri Denisov Fermilab SLHC/VLHC Workshop Fermilab, October 2003 Outline: Energy frontier Properties of interactions at 100TeV What we would like to measure? Accelerator/detector interface Detectors for 100TeV R&D plans

2. Energy Frontier • Tevatron is progressing with delivering world highest energy collisions of 2TeV to CDF and D0 experiments • “Top factory” • In a few years LHC will come on-line with 14TeV center of mass energy • “Higgs factory” • Progress in high energy physics has always been correlated with increase in energy of accelerators/colliders • Higher mass objects could be created • Smaller distances could be studied • Next “natural” step is ~100 TeV center of mass energy • How can we reach such energy? • Can we build detectors for such a machine?

3. Available Literature • There are plenty of documented studies available • Eloisatron studies book • Snowmass 1996 and 2001 reports • VLHC 2001 Design Study report • http://www.vlhc.org • LHC detectors design reports • SSC detectors design reports • x2 in energy only… • Experience with running Tevatron and LHC detectors

4. Properties of (soft) pp Interactions • Most results are for 100TeV center of mass energy • Increase in total and inelastic cross sections is small • Less then x2 in comparison with Tevatron • Less then ~30% in comparison with LHC • Values at 100TeV • Total s ~ 150mb • Inelastic s ~100mb

5. Charged Particles Multiplicities • Number of charged particles produced in 100TeV collision is similar to Tevatron/LHC energies • Average number is ~102 particles per interaction • Most particles are concentrated in the central rapidity “platou” region • Important to remember • Distribution of number of particles per interaction is non-Gausian • there is long tail into high multiplicity region

6. Particles Pt Distribution • Most of the particles produced at 100TeV are soft • Average Pt of the particle is ~0.6GeV • This feature might be useful to reduce occupancies in the central region where most high mass objects will decay to • Clean soft charged tracks in the forward region using solenoidal field • We assume that soft processes simulation is valid from 2TeV to 100TeV jump • Cosmic rays cross section measurements confirm this assumption Pythia

7. Radiation Doses in Central Tracker • Radiation doses at high energy/high luminosity colliders are high enough to affect properties of the materials used for detectors construction • Mostly affected areas are • Central tracker • Calorimetry in shower maximum • Close to beam pipe elements- see N. Mokhov talk on Saturday • As expected from total cross section and Pt spectrum radiation doses in the central region are practically independent of center of mass energy and linear function of luminosity • For central tracker typical dose at 10cm radius at 1034cm-2sec-1 luminosity is ~5-10Mrad per year

8. Radiation Doses in Calorimetry • Doses in the shower maximum are reasonable (~ 0.1Mrad/year) in the central region, but raise sharply in the forward region • All energy is going in the forward direction • Good eta coverage needed for many studies (missing Et determination) sets hard requirements on the forward calorimetry • ~Grad/year

9. What We Would Like to Measure? • Because there is no specific physics process to be studied general purpose detector(s) is a must for an energy frontier machine • Two general detectors sounds like reasonable minimal approach • Verification of the results obtained in very complex experimental and analysis conditions • Competition • In order to optimize detector design usually set of benchmark processes are used • Top detection • W mass resolution • Higgs/SUSY discovery • Others which depends upon “hot topics” at the design stage • Final design is a compromise between different requirements • Larger tracking volume has advantages for tracking and B physics, but adds material between calorimeter and makes calorimeter less hermetic and more expensive

10. What We Would Like to Measure - Continue • In order to discover top quark both CDF and D0 had to detect: • Leptons (e/m) • Jets • Tag b-quarks (associated lepton, displaced vertex) • Neutrinos (missing Et) • We need • tracker (e/m, vertex) • calorimeter (jets, missing Et) • muon system • Basically we are measuring all stable (lifetime more ~ size of the detector) known particles

11. Major Accelerator/Detector Interface Parameters - 1 • Interaction region sizes • Transverse plane • A few microns in diameter • As a point for precision tracking • For short lived particles detection • Longitudinal axis • Longer • Easier to separate multiple interactions • Lower local occupancies and radiation doses • Shorter • smaller (cheaper) detectors • better missing Et resolution • From Snowmass and other studies number of s ~ 10cm came as baseline number • Reasonable from the accelerator stand point

12. Major Accelerator/Detector Interface Parameters - 2 • Bunch spacing time • Shorter bunch spacing reduce number of interactions per crossing • Events pileup reduction • Complicates detectors and electronics • Natural limit • (detector size)/c • ~20ns (LHC’s choice) • DC beam? • Very important • Beam halo • Other accelerator induced “backgrounds” • Beam aborts • He from the tunnel “Simulation” of large multiplicity crossing…

13. SMT SMT SMT General Purpose Detector • General purpose colliding detector design has been pretty stable over last 10-15 years • Tracking in the central solenoid field with precision vertexing • Hermetic electro-magnetic and hadron calorimetry with fine space segmentation and good rapidity coverage • Large acceptance muon system with good triggering and tracking capabilities

14. Central Tracker • In order to preserve tracker momentum resolution • sp/p  ~ Increase detector lever arm (L) - cost Increase magnetic field (B) – at the limit Improve coordinate accuracy of detectors sdet to a few micron level  • Major problem for a VLHC tracker is to keep momentum resolution at reasonable level for high pt tracks • Give up momentum measurement a’la Run I Tevatron D0 detector?

15. Calorimetry - 1 • Shower depth is ~lnE • Minor size increase in comparison with LHC  • Energy resolution: • Electro-magnetic: ~15%/E, 0.5% at 1TeV  • Hadron ~50%/E, 2% at 1TeV  • Calorimetry gets very precise at high energy! • Issue • Events pile up • ~50GeV/jet cone at L=1034 cm-2sec-1 • Background energy fluctuates and luminosity dependent 

16. Calorimetry - 2 • Main specifications for VLHC calorimetry • Radiation hard: ~5Mrad in the central region and ~10Grad in the forward region  • Small constant term, stable, easy to calibrate • Thick – missing Et, energy resolution • Fast – signal collection time below bunch spacing • Multiple options available • Scintillation based calorimetry • LAr • Crystals • High density gas calorimetry Calorimetry looks OK for luminosity of 1034 cm-2 sec–1, but not many choices for 1035 cm-2 sec–1

17. Detection of Muons - 1 • High energy muons are important for search of heavy objects andlow energy muons for t, b quarks tagging  • Muon detectors are BIG! • Radiation damage is less of a problem for muon detectors • but doses especially from accelerator and neutrons have to be carefully estimated • High energy muons start to irradiate  (em showers) and loose more energy due to radiation losses then due to ionization at a few hundred GeV • Creates backgrounds in muon tracking detectors and requires corrections for momentum measurements 

18. Detection of Muons - 2 • Momentum resolution is limited by factors similar to the central tracker sp/p ~ • Design SDC (SSC) muon system resolution is ~ 10% at pt ~ 1TeV/c • Precision measurement of very high energy muons is a challenging task

19. Issues for Studies – VLHC Detectors • Radiation hard detectors • Central tracking and calorimetry • Very high precision tracking to measure muon momentum in the range 1TeV to 10TeV with a few % resolution • Field? Size? Accuracy? • Effect of events overlap on final states recognition • Handling 5TeV per trigger tower from min_bias overlaps? • The only way to reduce number of events per crossing is smaller bunch spacing. Can we build detectors/electronics which will resolve collisions a few ns apart • Begining of one shower is in the em calorimeter while hadron calorimeter still sees remnants of the shower from previous collision? • Reduction in cost of the detectors, trigger and DAQ systems • Can design detectors with slightly worse parameters, but cheaper with less construction time? • For many years we did not see new principles of particle detection. • Need reasonable level of R&D for the new methods of particles detection, however strange they look from the first glance

20. VLHC Detectors Summary • VLHC general purpose detector design will need • Tracking in magnetic field, hermetic calorimetry, and muon system • Radiation doses in the central rapidity region increase slowly with collider energy and linearly with luminosity • Detectors similar to SSC/LHC could be used to study 100TeV collisions at luminosity ~1034cm-2sec-1 • Measuring momentum of high pt tracks is a challenge • Luminosities well above 1034cm-2sec-1 create serious experimental problems • Radiation load • Events pileup • Hadron collider is the only currently viable road to the energy frontier, 100 TeV VLHC will provide opportunity • To create new particles in the 10 TeV mass range • To “look” at distances of ~10-20cm