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# How to optimize the ILC energy for measuring ZH - PowerPoint PPT Presentation

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

LAL/Orsay

F. Richard ILC Beijing Feb. 2007

• 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

• 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

F. Richard ILC Beijing Feb. 2007

• 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

• 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

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

• 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 covers a much more restricted domain and cannot measure the mass if the Higgs decays invisibly

F. Richard ILC Beijing Feb. 2007

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

• 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

Pisin Chen/ Yokoya

checked against

Guinea Pig

F. Richard ILC Beijing Feb. 2007

• 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

mrecoil = 120.245±0.0162 GeV

F. Richard ILC Beijing Feb. 2007