how to optimize the ilc energy for measuring zh
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F. Richard ILC Beijing Feb. 2007 1
How to optimize the ILC energy for measuring ZH
Philip Bambade, François Richard
LAL/Orsay
Presented at the ECFA meeting in Valencia
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: - (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:Mh=1.5 GeV in Hµµ Mh ~ 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 HZ
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
2 30 1( ) (1 ) (1 )a af x a x a x x
F. Richard ILC Beijing Feb. 2007 6
How does L vary with E? L can be maintained ~constant between 350 and
230 GeV provided is taken constant:
If N is constant (particles/bunch) Pelectrical goes like Ecm
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
2²= CM
z x
NE
F. Richard ILC Beijing Feb. 2007 7
The ‘needle’ plot LDC (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
Rec. Mass 350 GeVin Hµµ 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 Ejet=AEjet 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), h 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
Ref below gives the details of this analysishttp://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 ZZ background
Main Inputs
F. Richard ILC Beijing Feb. 2007 12
Checks on BS
Pisin Chen/ Yokoya
checked againstGuinea 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
mrecoil = 120.245±0.0162 GeV
L = 500 fb-1
%1.2
F. Richard ILC Beijing Feb. 2007 16
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