M. Gilchriese LHC Startup Luminosity Planning July 29, 2005

M. Gilchriese 2 References Background on LHC Relatively recent workshop (Chamonix in January 2005) Other 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/ –Talk by Polisello at recent LHCC meeting

M. Gilchriese 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…..

M. Gilchriese 4 Design Goals Nominal Parameters Beam energy (TeV)7.0 Number of particles per bunch Number of bunches per beam2808 Time between crossings(ns)25 Crossing angle (  rad) 285 Nomalised transverse emittance (  m rad) 3.75 Beta function at IP 1, 2, 5, 8 (m)0.55,10,0.55,10 Luminosity in IP 1 & 5 (cm -2 s -1 )10 34 Luminosity in IP 2 & 8 (cm -2 s -1 )~ Transverse beam size at IP 1 & 5 (  m) 16.7 Transverse beam size at IP 1 & 5 (  m) 70.9 Stored energy per beam (MJ)362

M. Gilchriese 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.

M. Gilchriese 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

M. Gilchriese 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  *

M. Gilchriese 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 > ) Phase II collimators and full beam dump –25ns operation Push towards nominal performance

M. Gilchriese 9 Stage 1 – Pilot Run Luminosities No squeeze to start 43 bunches per beam (some displaced in one beam for LHCb) Around per bunch Push one or all of –156 bunches per beam (some displaced in one beam for LHCb) –Partial optics squeeze –Increase bunch intensity Beam energy (TeV) 6.0, 6.5 or 7.0 Number of bunches per beam * in IP 1, 2, 5, 8 (m) 18,10,18,102,10,2,10 Crossing Angle (rad) 000 Transverse emittance ( m rad ) 3.75 Bunch spacing (s) Bunch Intensity Luminosity IP 1 & 5 (cm -2 s -1 ) ~ ~ ~ Luminosity IP 2 (cm -2 s -1 ) ~ ~ ~

M. Gilchriese 10 Stage 2 – 75ns Luminosities 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 Beam energy (TeV) 6.0, 6.5 or 7.0 Number of bunches per beam 936 * in IP 1, 2, 5, 8 (m) 2,10,2,100.55,10,0.55,10 Crossing Angle (rad) Transverse emittance ( m rad ) 3.75 Bunch Intensity Luminosity IP 1 & 5 (cm -2 s -1 ) ~ ~ ~ Luminosity IP 2 & 8 (cm -2 s -1 ) ~ ~

M. Gilchriese 11 Stage 3 – 25ns Luminosities 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 Beam energy (TeV) 6.0, 6.5 or Number of bunches per beam 2808 * in IP 1, 2, 5, 8 (m) 0.55,10,0.55,10 Crossing Angle (rad) 285 Transverse emittance ( m rad ) 3.75 Bunch Intensity Luminosity IP 1 & 5 (cm -2 s -1 ) ~ ~ Luminosity IP 2 & 8 (cm -2 s -1 ) ~ ~ ~ Long shutdown (6months) After shutdown

M. Gilchriese 12 Typical Year

M. Gilchriese 13 The First Years? ~ ~ ~ ~ ~ ~ ~ ~ If one takes the luminosities from previous…..

M. Gilchriese 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 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.

M. Gilchriese 15 Some Rates for 1 pb -1 Channel# of Events W -> µ 7000 Z -> µµ1100 t tbar -> µ + X80 QCD jets PT>150 GeV1000(for 10% of trigger bandwith) Minimum biasTrigger limited gluino-gluino, M~ 1TeV1-10 Taken from table in hep-ph/

M. Gilchriese 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…

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

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

M. Gilchriese 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

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