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How to optimize the ILC energy for measuring ZH

Presented at the ECFA meeting in Valencia. How to optimize the ILC energy for measuring ZH. Philip Bambade, François Richard LAL/Orsay. Introduction. TESLA scenario for ZH(120): 500 fb-1 at √s= 350 GeV (the top threshold) Here we suggest that running at √s~MH+110

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How to optimize the ILC energy for measuring ZH

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  1. Presented at the ECFA meeting in Valencia How to optimize the ILC energy for measuring ZH Philip Bambade, François Richard LAL/Orsay F. Richard ILC Beijing Feb. 2007

  2. Introduction • TESLA scenario for ZH(120): 500 fb-1 at √s=350 GeV (the top threshold) • Here we suggest that running at √s~MH+110 is more adequate since one has: - s(HZ) twice larger if MH=120 GeV - the recoil mass resolution for Hµµ is 4 times better • Also, while it seems much more useful to operate at √s=500 GeV for ttH, ZHH and new physics, this energy seems inadequate for measuring Higgs mass and branching ratios F. Richard ILC Beijing Feb. 2007

  3. Running at 350 GeV • TESLA TDR at 350 GeV: sMh=1.5 GeV in Hµµ • sMh ~ p(2ECMp-Mz²) p=momentum of the muon • At 230 GeV ~4 times better • Similar gains are observed in the hadronic mode F. Richard ILC Beijing Feb. 2007

  4. Running at 230 GeV • Fast rising of sHZ Objections: • Undulator requires beam energy>150 GeV ? To be checked • How does L vary with s ? • Beamstrahlung F. Richard ILC Beijing Feb. 2007

  5. Beamstrahlung • Formula where x=E/E0 at the beam level • There is a ‘hard-core’ with a0 ~0.5 at 500 GeV a0 increases at lower energy • -> With a better momentum resolution there is always improvement F. Richard ILC Beijing Feb. 2007

  6. How does L vary with E? • L can be maintained ~constant between 350 and 230 GeV provided d is taken constant: • If N is constant (particles/bunch) Pelectrical goes like Ecm • d constant means more focusing in x and/or shorter bunches • Seems possible, but is it optimum for recoil mass? • The answer is yes optimizing on L(a0)² F. Richard ILC Beijing Feb. 2007

  7. The ‘needle’ plot Rec. Mass 350 GeV in Hµµ 230 GeV • LDC d(1/p)<510-5 GeV-1 • BS, ISR, FSR included • Same BS for both Ecm • NB: Eb stability <1-210-4 needed 350(230) GeV F. Richard ILC Beijing Feb. 2007

  8. Invisible decays • Present in many BSM scenarios: SUSY, Higher dimensions etc… • Very large discovery potential for ILC • Best sensitivity using recoil to Zhad • DEjet=AEjet A=0.3 assumed (not yet realistic since Emax=150 GeV at √s=350 GeV due to asymmetric decays) F. Richard ILC Beijing Feb. 2007

  9. LHC/ILC • LHC covers a much more restricted domain and cannot measure the mass if the Higgs decays invisibly F. Richard ILC Beijing Feb. 2007

  10. Conclusions If Mh=120 GeV, there are many good reasons to run at ~230 GeV: • Maximum cross section • Best possible precision on Mh (the ‘needle’ plot), Gh and BRinv • We should therefore see what are the limitations on the Machine side • Detector performances are essential F. Richard ILC Beijing Feb. 2007

  11. Main Inputs • Ref below gives the details of this analysis http://esgard.lal.in2p3.fr/Project/Activities/Current/ Networking/N2/ELAN/Documents/2007/ • Use of Chen/Yokoya parametrization checked against Guinea Pig • Use of an BS spectrum at 230 GeV with twice more focusing in x and 1.5 shorter bunches • Use an LDC momentum resolution and take into account asymmetric decays • Use a realistic ZZg background F. Richard ILC Beijing Feb. 2007

  12. Checks on BS Pisin Chen/ Yokoya checked against Guinea Pig F. Richard ILC Beijing Feb. 2007

  13. Control of systematics for Hµµ • Beam Energy /E<10-3 stability <210-4 • Twice tighter at 350 GeV • Momentum calibration at Z pole • BS through acollinear e+e- F. Richard ILC Beijing Feb. 2007

  14. Study of the processe+e- Zh l+l- X using full detector simulation and event reconstruction M. Ohlerich, A. Raspiareza, W. Lohmann F. Richard ILC Beijing Feb. 2007

  15. L = 500 fb-1 mrecoil = 120.245±0.0162 GeV F. Richard ILC Beijing Feb. 2007

  16. F. Richard ILC Beijing Feb. 2007

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