Download - Higgs pair production in a Photon Collider
Higgs pair production
in a Photon ColliderTohru Takahashi
Hiroshima Universityfor S.Kawada, N.Maeda, K.Ikematsu, K.Fujii,Y.Kurihara ,,,
1LCWS12 Arlington, TX
Higgs selfcoupling• A Higgs like particle found at LHC!• Higgs?, SM Higgs or ….
– coupling to fermions, gauge bosons• mass generation
– selfcoupling• symmetry breaking
T.Takahashi Hiroshima
How can the PLC do ?
even tough with the e+e-
2 4( )V
17th General Meeting @ KEK 3
This study
)1( SM
Self-coupling constant in the SM
Parameter of deviation from the SM
Final goal: Study of Higgs self-coupling
See feasibility of the measurement of Higgs pair creation in PLC.
how may events expected?
possible to suppress background?
S.Kawada.. et.al, Phys. Rev. D 85, 113009 (2012)
Sensitivity vs energy
T.Takahashi Hiroshima
BB
SM
obs
SM
L
L
N
NNysensitivit
GeVmH 120
η=η’=1,ηB=0
)(GeVs
11000 fbLdt
120hm GeV
Beam parameters (based on TESLA optimistic)
T.Takahashi Hiroshima
x3.7 x4.8Ee[GeV] 210 195n(1010) 2 2sz(mm) 0.35 0.35gex/y[m rad] 2.5/0.03 2.5/0.03bx/y[mm]@IP 1.5/0.3 1.5/0.3sx/y[nm] 96/4.7 99/5.5lL[nm] 1054 770x 3.76 4.8Pulse Energy[J] 10 10Lgeo(e-e-) [1034cm-2s-
1]8.7 8.1
Lpeak(gg) [1034cm-2s-
1]1.2 0.7
Ltot(gg)[1034cm-2s-1] 12.6 5.88
( ) ~ 270s peak GeV
Luminosity Distribution(CAIN)x=3.76
dLN s ds dtds
][106.12 1234 scmLdt
][102.1
)260(1234
scm
GeVLpeak
10
1
10-1
10-2
10-3
[ ]pb100
[ ]s GeV
Signal backgrounds
7
270GeV
gg->ZZ
tt
gg->WW
10-4 ( )HH bbbb
Signal & Backgrounds
• gg->WW 1.462*107events/year)
• gg->ZZ 1.187*104events/year
Signal
gg->HH( -> bbbb) 16.4events/year
Backgrounds
• gg->bbbb 1.187*104events/year
Assumption for the study integrated luminosity of 5 years of PLC run
106
dLs ds dtds
9
Event generation and Detector simulation
• detector simulation
• MC events• HH• WW• zz• bbbb
7.2 dead
45 1077.5 10
61 1061 10
!
10
Analysis• Signal
–gg->HH->bbbb• Kinematics and flavor information
– Jet clustering• forced 4 Jets
– Jet pairing– b tagging
• Event selection– pre-selection to reduced number of events– optimization with Neural Net
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jet paring
22
22
22
212
j
H
j
HH
MMMM
The jet of the least χ2 was chosen to be the most probable combination.
M1, M2 : reconstructed mass
MH : Higgs mass
2W
2Z
2bb are defined the same way
(Mbb=10GeV)
12
Analysis ~ b tagging~
• impact parameter <- simple !
Nsig: Number of displaced tracks in a jet
nsigL
L
L
13
Selection (1)
99.0cos,05.0 # Jet w/ more 0 off-vertex(>3s) tracks > 3
# Jet w/ more than 1 off-vertex(>3s) tracks > 2 b-tagging
β : Lorentz factor of a particle
θ : Angle between a particle and the beam
HH WW ZZ bbbb
Total 80 7.3×107 59400 260000
Pre-selecttion 47.7 81300 51270 80000
pre-selection: cut tacks to forward/backward region loose b- tagging
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Selection (2) --- Neural Network (NN)• parameters :
– χH2 , χZ
2, χbb2
– transverse (longitudinal) momentum,– # of jets with displaced vertex jets, – visible energy, – Ycut value of jet clustering, – # of tracks
• Maximize statistical significance *
* *Sig Sig
stat
Sig Sig BG BG
NS
N N
N: # of events occurring in 5 years
η: selection efficiency
Sig: signal
BG: background
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Example parameters For WW
2H (( 2))Njets Noff
WWHH
WWHH
Example of parameters for 4b
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max[cos ]jet# tracks
bbbbHH
bbbbHH
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example parameters for ZZ
2H
2Z
ZZHH
ZZHH
17th General Meeting @ KEK 18
Cut statictics
0.92SigJADE
total
NS
N
HH WW ZZ bbbbTotal 80 7.3×107 59400 260000
Pre-selecttion 47.7 81300 51270 80000
WW filter 12.3 24 234 380
ZZ filter 5.90 2 59 13
bbbb filter 3.77±0.08 0+1.8 5.4±0.6 7±1
jet clustering
17th General Meeting @ KEK 19
Ideal clusteringideal clustering usingcolor singlet information
for HH, WW,ZZ
not for bbbb as color singlet is nottrivial ( )jjm GeV
HHZZ
( )jjm GeV
H or zb
b
17th General Meeting @ KEK 20
Cut statictics
HH WW ZZ bbbb
Total 80 7.3×107 59400 260000Pre-selecttion 47.7 55800 4170 77800WW filter 40 8 46 1826ZZ filter 36 8 19 8
bbbb filter 34.7±0.2 5±2 5.2±0.6 6±1
4.9SigIdeal
total
NS
N
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Summary• We tried to see gg -> HH in a photon collider
based on TESLA optimistic parameters.• gg CM energy of 270GeV is optimum for mh
=120GeV• It is possible to suppress backgrounds with
improved jet clustering technique.– statistical significance of 4.9 with integrated luminosity
corresonds to 5 years of PLC run
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Backup slide
17th General Meeting @ KEK 23
Ideal clustering
4.9SigIdeal
total
NS
N