up: super-bunches Machine-detector versus normal bunches Stefan Tapprogge CARE-HHH Workshop CERN, November 8-11, 2004 Page 1

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1 Machine-detector interface and event pile-up up: super-bunches versus normal bunches Stefan Tapprogge CARE-HHH Workshop CERN, November 8-11, 2004 Page 1

2 Overview Introduction ATLAS and CMS at design luminosity (10 34 ) Challenges, relevant parameters Layout of the experimental cavern at IR1/5 Details on the transition experiment - machine Physics motivation for upgrade (re-cap only) Required detector performance Classes of upgrade scenarios Relevant parameters/issues from experiments view Examples for impact on detector sub-systems Summary and Outlook CARE-HHH Workshop, CERN, Geneva Nov. 8 th -11 th, 2004 Stefan Tapprogge, Mainz page 2

3 Introduction Based on the studies done earlier e.g. hep-ph/ ATLAS and CMS are preparing for R&D effort in order to upgrade relevant sub-detectors To be able to make use of a possible LHC upgrade towards luminosities of cm -2 s -1 Close interaction with machine R&D effort is obviously mandatory Identify realistic scenarios Workable/usable for both sides Reduce the number of scenarios considerably R&D effort not always independent of scenario Address different approaches and their impact Short vs. long bunches CARE-HHH Workshop, CERN, Geneva Nov. 8 th -11 th, 2004 Stefan Tapprogge, Mainz page 3

4 ATLAS/CMS at luminosity Some parameters for the detector performance Due to inelastic pp cross-section expect ~ inelastic pp events per collision occupancy (tracking), energy flow (calorimeter), radiation levels, Each bunch crossing: ~ 750 charged particles in η <2.5 (<p T > ~ 450 MeV) Tracking detectors Granularity designed to have reasonable occupancy for good pattern recognition e.g. ATLAS pixel 10-4 (real particles) Compare to noise level of 10-6 (per pixel, per crossing) Calorimeter Degradation of energy resolution due to pile-up events Muon system Counting rate, occupancy degradation due to additional hits Radiation damage Collision related flux of primary and secondary particles Trigger and readout systems matched to bunch crossing frequency In addition identification of correct bunch crossing CARE-HHH Workshop, CERN, Geneva Nov. 8 th -11 th, 2004 Stefan Tapprogge, Mainz page 4

5 Status of construction ATLAS installation in the cavern has started Half-cylinder of the barrel Tile calorimeter CARE-HHH Workshop, CERN, Geneva Nov. 8 th -11 th, 2004 Stefan Tapprogge, Mainz page 5

6 Status of construction ATLAS installation in the cavern has started Half-cylinder of the barrel Tile calorimeter 1st coil of the barrel toroid magnet system CARE-HHH Workshop, CERN, Geneva Nov. 8 th -11 th, 2004 Stefan Tapprogge, Mainz page 6

7 Status of construction ATLAS installation in the cavern has started Half-cylinder of the barrel Tile calorimeter 1st coil of the barrel toroid magnet system Barrel LAr calorimeter cryostat (contains solenoid) CARE-HHH Workshop, CERN, Geneva Nov. 8 th -11 th, 2004 Stefan Tapprogge, Mainz page 7

8 CMS Installation Experimental cavern not yet finished (Jan 2005) CARE-HHH Workshop, CERN, Geneva Nov. 8 th -11 th, 2004 Stefan Tapprogge, Mainz page 8

9 CMS Installation Experimental cavern not yet finished (Jan 2005) Assembly mostly on surface CARE-HHH Workshop, CERN, Geneva Nov. 8 th -11 th, 2004 Stefan Tapprogge, Mainz page 9

10 CMS Installation Experimental cavern not yet finished (Jan 2005) Assembly mostly on surface (wheels) CARE-HHH Workshop, CERN, Geneva Nov. 8 th -11 th, 2004 Stefan Tapprogge, Mainz page 10

11 Layout of the cavern in IR1 ATLAS Detectors Shielding CARE-HHH Workshop, CERN, Geneva Nov. 8 th -11 th, 2004 Stefan Tapprogge, Mainz page 11

12 Layout of the cavern in IR5 Side-view of CMS CARE-HHH Workshop, CERN, Geneva Nov. 8 th -11 th, 2004 Stefan Tapprogge, Mainz page 12

13 Layout of the cavern in IR5 Details on the shielding CARE-HHH Workshop, CERN, Geneva Nov. 8 th -11 th, 2004 Stefan Tapprogge, Mainz page 13

14 Physics motivation for upgrade For more details, see D. Denegri s talk (plenary Monday 8th Nov.) Extend LHC physics reach for Discoveries increase mass reach by % access to rare decays (Higgs, FCNC top, ) 5σ contours 6 6 tanβ=10 Z-like Z with Γ (Z ) / m(z ) ~ 3% CARE-HHH Workshop, CERN, Geneva Nov. 8 th -11 th, 2004 Stefan Tapprogge, Mainz page 14

15 Physics motivation (cont d) Extend LHC physics reach also via Precision measurements Higgs-to-fermion/boson couplings, Higgs self-coupling (?), Triple and quadratic gauge boson couplings (TGC, QGC), strong V L -V L scattering (needs forward jet tagging) SUSY mass measurements (for rate limited processes) 14 TeV 100 fb TeV 100 fb TeV 1000 fb TeV 1000 fb -1 qqh qqww l g Dk Z tth ttγγ qqh qqττ tth ttbb H γγ H ZZ H WW H ZZ WH γγ + X H γγ WH WWW H WW l Z l Z Closed: 600 fb -1, Open: 6000 fb -1 CARE-HHH Workshop, CERN, Geneva Nov. 8 th -11 th, 2004 Stefan Tapprogge, Mainz page 15

16 Physics motivation (cont d) To fully profit from increased luminosity similar detector performance as now needed discoveries at higher masses Could be done with calorimetry and muon system only However: precision measurements and understanding of new phenomena need Identification and precise reconstruction of high p T objects such as electrons, photons, tau-hadrons, b-jets, Forward jet tagging Requires good tracking capabilities, e.g. Electron and tau identification and background rejection b-jet tagging Determination of secondary vertices, CARE-HHH Workshop, CERN, Geneva Nov. 8 th -11 th, 2004 Stefan Tapprogge, Mainz page 16

17 LHC machine upgrade scenarios Phase 0: stretch machine to its limits Increase luminosity by factor 2.3 beyond design value Comes for free (might need to upgrade injectors however) Phase 1: upgrade of the interaction regions Increase luminosity by up to one order of magnitude Phase 2: upgrade of the arcs as well Increase luminosity (as before) and s by a factor of 2 SPS upgrade with superconducting magnets to inject at 1 TeV New dipoles with 15 T field In the following concentrate on phase 1 Increase in s easily handled (for same luminosity) As will be shown later Shorter bunch spacing 12.5 ns would ease experiments life Reduce occupancy per collision especially for tracking detectors CARE-HHH Workshop, CERN, Geneva Nov. 8 th -11 th, 2004 Stefan Tapprogge, Mainz page 17

18 LHC Upgrade Phase 1 ATLAS score table Only indicative, scenarios keep evolving scenario luminosity (10^34) bunch spacing (ns) bunch length (cm) interactions/bunch crossing nominal 1,0 25 7,55 23 ultimate 2,3 25 7,55 53 Piwinski-1 3, ,20 83 Piwinksi-2 3, , IR-upgrade 4,6 25 3, Piwinski-IR upgrade 6, , superbunch 9,0 ~ ,00 ~ Address impact on necessary upgrade for each of the scenarios above Quite some variety in the number of interactions in one bunch crossing CARE-HHH Workshop, CERN, Geneva Nov. 8 th -11 th, 2004 Stefan Tapprogge, Mainz page 18

19 Conditions for super-bunches For a length of 300 m (σ z = 75 m), two superbunches will provide pp interactions during 1 µs Out of the 88 µs time for one turn At a luminosity of cm -2 s -1 Interaction rate: Hz Interactions per super-bunch crossing: 10 6 Interactions per time: 10 3 per ns This implies that within 25 ns there will be on average inelastic events occuring Compared to the 25 of today s design luminosity or the 125 for the upgrade with 12.5 ns spacing Last number assumes new electronics to match 12.5 ns CARE-HHH Workshop, CERN, Geneva Nov. 8 th -11 th, 2004 Stefan Tapprogge, Mainz page 19

20 Tracking issues Largest impact due to increase in particle fluxes Occupancy increase by factor 10 naively For same bunch spacing and detector geometry Present systems designed for minimal inefficiencies (goal: maximum of 1%) Requires worst-case dead-time for one pixel before next hit can arrive of 2.5 µs (expect innermost) 0.5 µs (innermost ATLAS example) Implemented in readout architecture for an average occupancy of 10-4 (value for cm -2 s -1 ) Higher particle fluxes for same deadtime Higher inefficiencies impact on pattern recognition Particles from next event (in time) enter tracking detector when earlier particles have not yet left! 1 ns corresponds to 0.3 m typical diameter is 2 m CARE-HHH Workshop, CERN, Geneva Nov. 8 th -11 th, 2004 Stefan Tapprogge, Mainz page 20

21 Pile-Up contribution H ZZ µµee (M H = 300 GeV) cm -2 s cm -2 s cm -2 s cm -2 s -1 CARE-HHH Workshop, CERN, Geneva Nov. 8 th -11 th, 2004 Stefan Tapprogge, Mainz page 21

22 Example: LAr calorimeter signal in ATLAS Shaped signal is sampled at 25 ns intervals Extract signal amplitude and time via optimal filtering For 12.5 ns bunch spacing Identification of bunch crossing (BCID) might be problematic Calorimetry: Pile-up noise for 25 ns sampling s i sampled every beam crossing Optimal filtering Amplitude : A = Σ a i s i Time : A t = Σ b i s i where a i and b i are the filtering coefficients CARE-HHH Workshop, CERN, Geneva Nov. 8 th -11 th, 2004 Stefan Tapprogge, Mainz page 22

23 Calorimetry: Pile-up noise Electronic noise Increases with decreasing shaping time Pile-up noise Increases with increasing shaping time Degradation of energy resolution due to pile-up noise (scales with L) Optimize shaping time ~ Depends as L 1/4 For cm -2 s -1 optimal value of 28 ns CARE-HHH Workshop, CERN, Geneva Nov. 8 th -11 th, 2004 Stefan Tapprogge, Mainz page 23

24 Calorimetry: : space-charge charge effects Most important in the forward region Small angles relative to beam pipe Relevant parameter is α J: charge injection rate µ: ion mobility α = d2 V J εµ Critical and Energy Density 1,0E+08 1,0E+07 1,0E+06 1,0E+05 Critical Energy Nominal Ultimate Piwinski-1 Piwinski-2 IR-upgrade Piwinski-IR upgrade SuperBunch Baseline 1,0E ,5 1 1,5 2 2,5 3 3,5 CARE-HHH Workshop, CERN, Geneva Nov. 8 th -11 th, 2004 Stefan Tapprogge, Mainz page 24

25 Muon system Not a very critical item Might have to reduce the acceptance to values of η <2 Increase of shielding non-trivial Effect of increased occupancy on pattern recognition e.g. trigger resolution and rates Stability of operation under high rates Bunch crossing identification For shorter 12.5 ns spacing CARE-HHH Workshop, CERN, Geneva Nov. 8 th -11 th, 2004 Stefan Tapprogge, Mainz page 25

26 Radiation background Neutron flux at cm -2 s -1 CARE-HHH Workshop, CERN, Geneva Nov. 8 th -11 th, 2004 Stefan Tapprogge, Mainz page 26

27 Trigger and DAQ issues Strong dependence on bunch spacing For 12.5 ns preferable to re-build system capable of running at 80 MHz Although present system might be still usable For super-bunch have to take different approach As faced with continuous beam for 1 µs Using a free running clock 100 MHz) would give a readout rate of 100 khz during the spill Much more precise timing needed than for short bunches Other issues like thresholds and performance in rate reduction might be not too different Isolation criteria e.g. for electrons could be degraded more significantly for super-bunch (use of tracks) and on the details of the upgraded detectors CARE-HHH Workshop, CERN, Geneva Nov. 8 th -11 th, 2004 Stefan Tapprogge, Mainz page 27

28 General issues Services and integration very important aspects from the very beginning Radiation background / levels Cannot afford to replace detector parts every year the above are not driven by the details of the bunch structure in an upgrade Influenced by luminosity value and others Movement of machine elements closer to the IP ATLAS: installation and access scenarios most likely will not allow a movement by more than (n )10 cm n will be a small number! CMS might have a bit more flexibility If the forward calorimeter were not to be needed CARE-HHH Workshop, CERN, Geneva Nov. 8 th -11 th, 2004 Stefan Tapprogge, Mainz page 28

29 Statement on super-bunches 'Based on the physics motivation for an upgrade of the LHC luminosity by an order of magnitude, it is not seen how in case of the super- bunch scenario, this increase in luminosity could be exploited by an upgraded ATLAS or CMS detector.' This assumes that detector upgrading does not imply building a completely new detector Even this would be highly non-trivial Also for purely extending the discovery reach to 20-30% higher masses, the super-bunch scenario will be problematic Increased pile-up in calorimeter: degrades jet measurement and electron identification significantly CARE-HHH Workshop, CERN, Geneva Nov. 8 th -11 th, 2004 Stefan Tapprogge, Mainz page 29

30 Summary Physics motivation for upgrade implies Similar detector capabilities and performance as assumed today is needed Super-bunch scenario presents a too huge a challenge Integrated luminosity in stable running mode is what counts most Optimize not only for large peak luminosities!? Question: Could there be severe sources of machine (single beam) related backgrounds? For design luminosity, assume that single beam related background is negligible Preference from the experiments Shorter but finite bunch spacing, e.g ns to reduce the effect of the minimum bias events Eases especially the pattern recognition for tracking CARE-HHH Workshop, CERN, Geneva Nov. 8 th -11 th, 2004 Stefan Tapprogge, Mainz page 30