higgs pair production at photon collider
DESCRIPTION
Higgs pair production at photon collider. ILC Physics WG general meeting 21. November 2009 Hiroshima University Nozomi Maeda. Introduction. Photon Linear Collider (PLC) is gamma-gamma collision option in ILC. - PowerPoint PPT PresentationTRANSCRIPT
Higgs pair production at photon collider
ILC Physics WG general meeting21.November 2009
Hiroshima UniversityNozomi Maeda
Introduction
Photon Linear Collider (PLC) is gamma-gamma collision option in ILC.
We study feasibility of measurement of Higgs self-coupling constant =SM(1+) by ->HH
This process occurs at low energy(than e+e-). contribution to cross section is different.
Energy optimization
BB
SM
obs
SM
LL
NNN
ysensitivit
L:Luminosity(assume 1000fb-1) :detection efficiency :cross section B:background suppression
Higgs mass=120GeV
SMLysensitivit
=-1
=+1
Background
large background : ->WW ( ~ 90pb) cf.) Signal: = 0.044fb0.044fb/90pb = 4.9×10-7
10-7 background suppression is necessary.
(+,+), (-,-)
Luminosity spectrum
total luminosity of photon collision = 1.26×1035cm-2s-1
effective Xsec(Signal) = 0.013fb → 16event/yeareffective Xsec(BG) = 11,600fb → 1.467×107event/yearB<10-6 is required.
Simulation by CAIN.
Analysis ->HH H -> bb or WW* or gg …
H->bb mode has the largest Branching Ratio (when Higgs mass = 120GeV, B.R.=67.8%).
Signal:HH->4bBackground:WW->4quark
reconstruct particles from jet pairs that has the smallest 2.
22
22
22
212
jj
MMMM
M1, M2 = reconstructed particle mass M = MH or MW 2j = 2jets mass resolution
->WW rejuction
• pre-Selection :
use Neural Net(JetNet) to separate ->HH from ->WW.
input = 9, hidden = 18, output = 1# of loose b-tagged jets > 2 & # of tight b-tagged jets > 1 (loose : nsig=3.0, noffv=1 tight : nsig=3.0,
noffv=2)- >HH - >WWNo Cut 5.00E+04 7.50E+07pre- Selection 3.04E+04 8.62E+04
Signal = 5.00×104 BG = 7.50×107
• # of generated events :
• # of nodes :
NN output• input parameters :
2H, 2
W, # of tracks, momentum(transverse, longtidunal), Visible Energy, ycut, # of b-tagged jets(loose, tight) (loose : nsig=3.5, noffv=1 tight : nsig=3.5,
noffv=2)black:BG blue:Signal
87 1033.5
105.74
BG
156.0100.5
78054
Sig
NNout > 0.98
If PLC runs for 5years... Signal : 16×5×Sig ≒ 12.5 Background : 1.467×107×5×BG ≒ 3.9 significance =
3.1
0102030405060708090
100
0.15 0.2 0.25 0.3 0.35 0.4sqrt(s_AA)
Xsec
->ZZ background
->ZZ Xsec ≒ 50fb@300GeVphoton helicity = (+1, +1)
Integrate over 8deg<<172deg
(generated by Gounaris’s gamgamZZ code: hep-ph/0610085. offered by Tsumura-san.)
02468
101214
0.2 0.25 0.3 0.35 0.4 0.45
->ZZ background
->ZZ effective Xsec ≒ 9.6fb→1.2×104events/yearIntegrate over
8deg<<172deg (generated by Gounaris’s gamgamZZ code: hep-ph/0610085. offered by Tsumura-san.)
x=3.76
->ZZ->4f event generatorZZ decay modes are ... q = light
quark
→ develop ->ZZ->4f event generator
bbbb……be background source .
bbqq (12.9%), ccqq (10.3%), qqqq (18.3%), bbbb (2.28%), bbcc (3.62%), cccc (1.44%)
Z
Z
f
ff
fgamgamZZ code HELAS
use gamgamZZ code and HELAS for calculating helicity amplitude.
→ simulate ->ZZ event, and study how to reject ->ZZ.
->ZZ event generator
Z
ZXsec distribution
(not includes Z decay mode and Luminosity)
total Xsec = 49.8fb (consistent with gamgamZZ code)
Summary We study feasibility of measurement of Higgs
self-coupling constant at PLC. ->WW background is 106 times larger than
->HH signal. Neural Net with b-tagging and kinematics can
reject almost all ->WW background. ->ZZ event generator developing in progress. Next plan is including Z decay mode and
Luminosity spectrum to ->ZZ event generator.
->4b background
+ and other diagrams
Xsec(not convolute luminosity) = 2.81fb@optimum energy
b-tagging cannot reject ->4b too.