Machine-Detector Interface for the CEPC

Transcription

1 Machine-Detector Interface for the CEPC Hongbo ZHU (IHEP) Joint effort of the Detector and Accelerator Groups

2 Machine-Detector Interface Machine Detector Interface (MDI) covers all aspects that are common to both accelerator and detector, and represents one of the most challenging areas of the CEPC project. Topics covered in this talk: Interaction Region (IR) layout Beam-induced backgrounds Luminosity instrumentation e+ IP1 e- LTB BTC e+ e- Linac (240m) BTC Booster(50Km) CEPC Collider Ring(50Km) IP2 2

3 Interaction Region Layout Final focusing magnets inside the detector constraints on the detector layout Shielding IR: beampipe, surrounding silicon detectors, luminosity calorimeter, final focus quadrupoles (QD0 and QF1),etc. Short focal length of L*=1.5 m realisation of the design luminosity without exploding the chromaticity corrections 3

4 Beam-induced Backgrounds Background originating from beambeam interactions Beamstrahlung Electron-positron pair production Hadronic background Additional background sources Synchrotron radiation Beam-gas interaction Radiative Bhabha scattering Beam halo muons Beam dumps Beam-beam interaction and the so-called Pinch Effect To be minimised with careful machine design 4

5 Beam-beam Interaction Simulation Generator of Unwanted Interactions for Numerical Experiment Analysis Program Interfaced to GEANT GUINEA-PIG Input machine parameters for CEPC (and compared to ILC250) Machine(Parameters CEPC ILC250 E cm $[GeV] Par1cles$per$bunch Beam$size$σ x /σ y $[nm] 73700/ /7.7 Beam$size$σ z $[μm] Norm.$EmiJance$ε x /ε y$ [mm mrad] 1595/4.8 10/0.035 Results being cross-checked with CAIN 5

6 Beamstrahlung Pinch Effect bent particle trajectories beamstrahlung Beamstrahlung photons collimated in a small cone along the beam axis and of low transverse momentum Concerns for the collider design(e.g. power deposition); direct hitting on detector components must be avoided Guinea-Pig simulation result with the ILC250 configurations 6

7 Electron-Positron Pair Production Coherent and incoherent electron-positron pair production one of the most important backgrounds for the CEPC detector Guinea-Pig simulation result with the ILC250 configurations Detector components (including the beampipe) need to be placed away from the kinematic edge) 7

8 Radiation Levels Hit density of 0.2 hits/cm 2 /BX at r=1.6 cm (the first VTX layer) Radiation tolerance requirements (safe factor ~ 5): Non-ionising Energy Loss (NIEL) ~ MeV neq/cm 2 per year Total Ionisation Dose (TID) ~ 100 krad per year Mild requirements Extra feasibility on detector design (technologies, layout ) 8

9 Detector Layout Optimisation Low hit density (0.2 hits/cm 2 /BX) and mild radiation-tolerance requirement allow further optimisation of the detector layout, in particular the vertex detector beam pipe smaller r : 1 st detector layer closer to the Interaction Point to improve the IP resolution larger z : to compensate for the performance loss due to less strip detector layers in the forward region current smaller r larger z Other constraints to be taken into account B = 3.5 T pair-edge 9

10 Hadronic Background The! q q process gives rise to the hadronic background mini-jet : large polar angle + transverse momentum Rarely produced cross-section artificially inflated by 10 5 times in simulation But requires full detector simulation to understand the impact on the calorimeter performance 10

11 Luminosity Instrumentation Small uncertainty on luminosity measurement required by precision Higgs/Z measurements: ΔL/L ~10-3 Calorimeter with silicon-tungsten sandwich structure to measure small angle radiative Bhabha scattering events z [115,128 cm] (right before the final focusing magnet) and θ [60,90 mrad] requiring angular precision θ/θmin < Other sources of uncertainties: theoretical calculation of crosssection, polar angle bias, physics background subtraction, etc. Nontrivial to achieve the target luminosity uncertainty Online luminosity monitor allowing fast tuning of beam param. Radiation-hard sensors (e.g. CVD diamond) to measure radiative Bhabha events at zero photon scattering angle 11

12 Summary Machine Detector Interface (MDI) complicated and challenging Preliminary layout of the interaction region (short L*) Backgrounds from beam-beam interactions Next Step: detailed studies on all aspects Thanks for your attention! 12