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LHC Startup Luminosity Planning PowerPoint Presentation
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LHC Startup Luminosity Planning

LHC Startup Luminosity Planning

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LHC Startup Luminosity Planning

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  1. LHC Startup Luminosity Planning July 29, 2005

  2. References • Background on LHC http://ab-div.web.cern.ch/ab-div/Publications/LHC-DesignReport.html • Relatively recent workshop (Chamonix in January 2005) http://indicodev.cern.ch/conferenceDisplay.py?confId=044 • Other http://dpnc.unige.ch/seminaire/talks/bruning.pdf http://www.agsrhichome.bnl.gov/LARP/050406_danfords/ http://www.agsrhichome.bnl.gov/LARP/050406_danfords/pres/Bailey01.pdf Have stolen liberally from last reference above • Some references on early physics (not necessarily so early…) • Some previous talks at these Friday meetings(Ian, Andreas….) • hep-ph/05044221 • Talk by Polisello at recent LHCC meeting http://agenda.cern.ch/askArchive.php?base=agenda&categ=a053001&id=a053001s1t2%2Ftransparencies%2FgplhccJun2005.ppt

  3. Introduction and Disclaimer • The talk has a narrow scope • Not pedagogical regarding LHC • LHC startup is obviously very complex but I will ignore all of the complexity and focus on stated luminosity goals • Luminosity will likely vary by orders of magnitude in first year or more of operation, so plenty of room to be wrong in predictions! • Purpose is to (hopefully) initiate thinking locally (and maybe some work) on very, very early physics eg. from pilot run • Warning: I’m a pessimist about luminosity…..

  4. Design Goals

  5. Early Conditions • Compared to design conditions……………. • Beam energy very likely below 7 TeV. • 6 TeV? • 6.5 TeV? • Fewer protons per bunch • Many fewer bunches • Head-on collisions • Much larger *(less “squeeze”) • On-time for physics much less (same for detector no doubt) • Primary goal of first (pilot) run – achieve and sustain collisions, start understanding of machine.

  6. How To Get Started(I) • Avoid quenches (and damage) • Reduce total current to reduce stored beam energy • Lower ib • Fewer bunches • Higher * to avoid problems in the (later part of) the squeeze • Reduce energy to get more margin • Against transient beam losses • Against magnet operating close to training limit • Both machine and experiments will have to learn how to stand running at nominal intensities • An early aim is to find a balance between robust operation and satisfying the experiments • Maximize integrated luminosity • Minimize event pile-up

  7. How To Get Started(II) • Electron cloud ( LHC simulations and SPS experience ) • ib < 35% nominal for 25ns spacing • ib ~ nominal for > 50ns • With lower currents in mind, two machine systems will be staged • Only 8 of 20 beam dump dilution kickers initially installed • Total beam intensity < 50% nominal • Install the rest when needed • Collimators ( robustness, impedance and other issues ) • Phased approach • Run at the impedance limit during phase I • Lower currents • Higher *

  8. Planning • Phase I collimators and partial beam dump • Pilot physics run with few bunches • No parasitic bunch crossings • Machine de-bugging no crossing angle • 43 bunches, unsqueezed, low intensity • Push performance (156 bunches, partial squeeze, higher intensity) • 75ns operation • Establish multi-bunch operation • Relaxed machine parameters (squeeze and crossing angle) • Push squeeze and crossing angle • 25ns operation with Phase I collimators + partial beam dump • Needs scrubbing for higher intensities ( ib > 3 1010 ) • Phase II collimators and full beam dump • 25ns operation • Push towards nominal performance

  9. Stage 1 – Pilot Run Luminosities • No squeeze to start • 43 bunches per beam (some displaced in one beam for LHCb) • Around 1010 per bunch • Push one or all of • 156 bunches per beam (some displaced in one beam for LHCb) • Partial optics squeeze • Increase bunch intensity

  10. Partial squeeze and smaller crossing angle to start Luminosity tuning, limited by event pileup Establish routine operation in this mode Move to nominal squeeze and crossing angle Increase bunch intensity ? Tune IP2 and IP8 to meet experimental needs Stage 2 – 75ns Luminosities

  11. Production physics running Start with bunch intensities below electron cloud threshold Scrubbing run (1-2 weeks) Increase bunch intensities to beam dump & collimator limit Install beam dump kickers Install phase II collimators Increase bunch intensities towards nominal Tune IP2 and IP8 to meet experimental needs Stage 3 – 25ns Luminosities Long shutdown (6months) After shutdown

  12. Typical Year

  13. The First Years? 2008 2009 2010 2011 2007 ~ 7 1032 ~ 5 1033 1034 ~ 3 1028 ~ 2 1031 ~ 1 1032 ~ 2 1033 ~ 2 1033 ~ 5 1033 ~ 4 1032 If one takes the luminosities from previous…..

  14. Pilot Run Integrated Luminosity? • Very hard to estimate. • Efficiency factor(colliding beam time of machine and ATLAS working together) 10%? 20%...who knows • Optimistic??? Pessimistic??? guess would be about 1030 for about 30 days or very roughly 1 pb-1 • In my opinion, useful to understand what physics can be done with 0.1, 1, 10 pb-1 soon. Limited scope of study.

  15. Some Rates for 1 pb-1 Taken from table in hep-ph/0504221

  16. Follow On • Some studies have been done (see Rome meeting) that could be used as as starting point for “≤1-10pb-1 physics” investigations • Minimum bias dN/d and so forth • W and Z production • Jets • I think would be good idea to systematically go through these in the next few months…

  17. Extra Stuff From Polesello’s Talk to LHCC in June

  18. “Minimum Bias” dNch/d robust measurement: do not need full ID reconstruction 1000 events dNch/d Comparison of generated charged particles with reconstructed tracks • Only a fraction of tracks reconstructed, because: • limited rapidity coverage • can only reconstruct track pT with good efficiency down to ~500MeV h Black = Generated (Pythia6.2) Blue = TrkTrack: iPatRec Red = TrkTrack: xKalman dNch/dpT Reconstruct tracks with: 1) pT>500MeV 2) |d0| < 1mm 3) # B-layer hits >= 1 4) # precision hits >= 8 • Previous dNch/d measurements published for pT > 0, so need to apply correction factor. Biggest systematic uncertainty? • Explore special runs with reduced solenoidal magnetic field? pT (MeV)

  19. Studies on W production • Large statistics • Basic benchmark process to check our ability to perform measurements • Aim at constraining proton PDFs • Emphasis on understanding systematic detector effects • Rome Production W+/- -> e+/- Sample • HERWIG + CTEQ5L, U.E. with Jimmy • ~67K fully simulated events (5 pb-1). • Analysis performed with new ATLAS analysis tools • Concentrate on rapidity variables sensitive to PDF parametrisations and uncertainties • W->e Rapidity distributions at GEN and DET Level • W->e Asymmetry and Ratio at GEN and DET Level • Preliminary evaluation of charge misassignment systematics

  20. Top for about 300 pb-1 Selection cuts: ETmiss > 20 GeV, 1 lep Pt > 20 GeV, 4 jetsPt > 20 GeV No trigger selection efficiency taken into account yet Require Mw within 10 GeV of nominal W mass m(t) S/B = 1.77 Top mass (GeV) Top peak clearly visible after 1 week of LHC data(NOT AT 1030!!!) Measured top mass 160.0 ± 1.0 GeV , stat error on xs: 8.3% Work in progress on systematics Slide from Polesello at LHCC