How to optimize the ilc energy for measuring zh
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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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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


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


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


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


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


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


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


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


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


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


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


Checks on BS

Pisin Chen/ Yokoya

checked against

Guinea Pig

F. Richard ILC Beijing Feb. 2007


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


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


L = 500 fb-1

mrecoil = 120.245±0.0162 GeV

F. Richard ILC Beijing Feb. 2007


F. Richard ILC Beijing Feb. 2007


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