ILC Machine-Detector Interface Challenges Philip Bambade LAL-Orsay Workshop on the Future Linear Collider Gandia, Spain, December 1, 2005

Evolution of e  e  colliders adapted from K. Yokoya and J.-E. Augustin ILC  DAFNE  VEPP2M VEPP2ACO CEA BYPASS   DCI SPEAR AdA SLC

Why shift to linear collider ? storage ring tunnel, magnets,…   synchrotron radiation losses (RF)  E 4 /  optimum : equate both costs  total cost & size  E 2 unacceptable scaling !

Linear collider concept RF technology ( gradient, efficient power transfer ) beam phase-space control and stability  synchrotron radiation still drives design… focus idea : cost and size  E from N. Walker

LC machine : basic concepts example : TESLA  linac rep. rate f ≪ ring frequency  focus beam to small IP size   very strong (achromatic) lenses  ultimate limit (K. Oide) :  energy from synchrotron radiation in lenses  copious synchrotron radiation from colliding bunch space-charge (beamstrahlung), pinch, pairs, … DAMPING RING DETECTORS LINAC POSITRON SOURCE FINAL FOCUS POLARISED ELECTRONS D = disruption (pinch)

Beam-beam mutual focusing simulate collision with initial  y offset detectable post-IP deflection main tool at SLC ( and LEP ) SLAC-PUB-6790

Main ILC specifications from ILCSC (September 2003)  E c.m.s = TeV, upgradeable to ~ 1 TeV, capable of efficiently changing the energy (  scanning)  L > 500 fb -1 in 4 years after initial year of commissioning  Stability and precision of beam energy <  Electron polarization > 80 %  2 interaction regions for 2 detectors, with similar E c.m.s and L capabilities, among which one should have a crossing-angle to allow a future upgrade to  collisions  Optional upgrades: , e  e , e , GigaZ, polarized e 

Successful SLC (warm / 3 GHz) experience

at optical focus :   “depth of focus” want small  y need  z   y  SET  z   y hour-glass effect

ILC beam parameter optimization(s) SET  z   y  ~  2   n  nominally L/L nom ~ 2.8

ILC beam parameter optimization Nominal Luminosity [cm -2 s -1 ] ~ 2   L/L nom ~ 2.8  BS  backgrounds Design machine and detector for this set: E CM resolution Forward hermeticity Beam-beam systematics PRECISION PHYSICS

physics  detector  machine  LC design & operation : new challenges !  HEP community strongly involved  Special needs for some physics topics : Luminosity + energy + polarization – correlations – forward region – background detector damping ring compression injection backgrounds masks collimation final focus diagnostics controls linac extraction (diagnostics)  SLAC model LC is open system  “the experiment starts at the gun” LC performance  “beam-beam interaction dominated” crossing-angle choice

Examples of direct impact on precision physics program ( more work on quantitative assessments needed ) Include detector & physics performance in global ILC parameter optimization

1. Cécile Rimbault

Strongly biases luminosity measurements if not well corrected precision goal = Cécile Rimbault

2. Cécile Rimbault

Comparison with LDC occupancy tolerance LDCteslanominallowQlargeYlowPhighLum N incVD /bx N hits /cm 2 / bx Tolerance : 3 hits/cm 2 /bx (TDR) Using : Nb hits/particle = 3 rough estimate Surface L1 = 1.5cm* 10cm*2  = 94 cm 2 high Lum & lowP are beyond the occupancy tolerance (C. Rimbault)

(Geant4-based)

(S. Hillert & C. Damerell) Precision of secondary vertex charge determination as function of beam pipe radius Luminosity factor study also NEEDED to probe occupancy tolerance pipe ddd Dddd d

m top, m sleptons 2  m W 5  error  reconstruction top quark threshold S.Boogert 3.

Beamstrahlung spread dependence with IP beam offset Expect variations larger by factors 2-4 with “Low Power” for similar IP offset feedback criteria M. Alabau NominalLow Power

4.

very forward region  crossing-angle choice head-on or 2mrad 20 or 14 mrad IP geometry forward region calorimetry at low angle 1. luminosity 2. veto ~ 25 TeV from e  e  pairs ( ~ 3 GeV ) ~ 43 TeV

20 (14) mrad 2 (0) mrad spent beam extraction (& diagnostics) easier harder (highest energy & luminosity  ) local solenoid compensation needed not needed crab-crossing essential not essential Special IR magnet designs yes slightly harder Masking, collimation & backgrounds ? ….under study…. ? Beam diagnostics from pairs slightly worse a bit better Very forward hermeticity slightly worse a bit better Present ILC base-line Crossing-angle pros and cons  BS

V. Drugakov

Ring 1 Ring 3 Electron veto efficiencies in BeamCal  need to be introduced into stau analysis V. Drugakov

QUESTION TO EXPERIMENTAL COMMUNITY: Trade-off between: 1. Luminosity (factor 2-3, up/down) 2. Stronger beam-beam effects: luminosity spectrum, forward hermeticity, backgrounds, systematics,…

Indirect consequences through impact on configuration choices and physics options 2 IR  complementarity, balanced risks and flexibility with 1 large & 1 small crossing-angle 1 IR (+ 2 nd later)  crossing-angle choice affects articulation of physics program Only 1 IR  priority to ILC operability at highest energies & luminosities probably implies large crossing-angle choice

Options if ILC must start with single IR: Best choice to eventually achieve highest energy and luminosity beyond nominal goals -2 nd IR optional (later?), dedicated to precision studies in specific channels, if physics requires it - Best conditions for physics at nominal energies and luminosity - 2 nd IR optional (later?), to enable the  option and highest energy and luminosity beyond nominal goals, if physics requires and after accumulating learning experience N.B. These arguments are subject to debate in the ILC-WG4

Increasing awareness to MDI challenges in HEP ILC community Participation of Spanish groups in this work ( along side detector and physics activities )  important and very welcome: