aa->hh study aa->4b analysis & (preliminary) summary
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AA->HH Study AA->4b analysis & (preliminary) Summary. Shin- ichi Kawada ( AdSM , Hiroshima University). Outline. Introduction Previous results Today’s topic AA->4b BG analysis analysis of BG suppression (AA->WW, ZZ, 4b) Summary & Next plan. Introduction. - PowerPoint PPT PresentationTRANSCRIPT
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AA->HH StudyAA->4b analysis & (preliminary) Summary
Shin-ichi Kawada(AdSM, Hiroshima University)
22nd General Meeting @ KEK (2011/9/3) 1
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Outline• Introduction• Previous results• Today’s topic– AA->4b BG analysis– analysis of BG suppression (AA->WW, ZZ, 4b)
• Summary & Next plan
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Introduction• Photon Linear Collider (PLC) has been
proposed as one of the options of ILC.• It is expected that we can observe the Higgs
self-coupling in PLC.• Feasibility study of Higgs pair creation in PLC is
needed.
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About PLC
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Electrons
Backward Compton scattering
ILC : e+ e- collision PLC : gamma-gamma collision
gamma-gamma collision
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Reaction in gamma-gamma collision
• Signal : AA->HH->4b• Many backgrounds– AA->WW, ZZ, 4b, etc…
• Analysis of background reduction is necessary.– We assumed that Higgs mass equals to 120GeV in
this study.
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4b = b b-bar b b-bar
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Previous result (1)• Main backgrounds– AA->WW (~11.6pb, 1.5*107 events/year)– AA->ZZ (~9.42fb, 1.2*104 events/year)
• Analysis with Neural Network– We can observe Higgs pair creation if we can
develop good b-tagging method and jet clustering.
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BG usual cheatAA->WW 2.69 5.85AA->ZZ 1.61 5.85
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Previous result (2)• Other background --- AA->4b– cross-section = 46.6fb (with luminosity & (2-jet
invariant mass) < 15 GeV were cut)– ~ 6*104 events/year– need the detector simulation & analysis
22nd General Meeting @ KEK (2011/9/3) 7
γ b
b-bar
optimistic eventγ
γ
b
bb-bar
b-bar
pessimistic event
: color stringγ b
b-bar
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Topic (1) : AA->4b BG analysis
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at the 21st General Meeting4b(opt) : 1.81σ4b(pes) : 1.47σ
not bad, but not enough
need more effective cuts/NN analysis
• use other useful other parameterscosθ of jet (cosθ of 2-jet)event shape (thrust, sphericity, Y-value, etc...)
• jet pairingjet pair of least χH
2 -> χH2 , cosθ of 2-jet
jet pair of least χA2 -> χA
2 , cosθ of 2-jet
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Analysis procedure (1)• MC samples– remained events after W filter & Z filter
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realclustering
signal 4b(opt) 4b(pes)
generate 50000 1000000 1000000
pre-selection 29958 241318 287776
W filter 7713 1083 1936
Z filter 6042 624 1240
cheatclustering
signal(cheat)
4b(opt) 4b(pes)
generate 50000 1000000 1000000
pre-selection 29152 241318 287776
W filter(cheat)
24115 4535 7422
Z filter(cheat)
22987 3077 5743
input these events to NN
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Analysis procedure (2)• 17 Input parameters to NN– no relation to χ2 (11 parameters)• visible energy, # of tracks, ycut value of jet clustering,
thrust, sphericity, Y-value, cosθ of jet (4), max|cosθ of jet|
– jet pairing of least χH2 (3 parameters)
• χH2 , cosθ of 2-jet (2)
– jet pairing of least χA2 (3 parameters)
• χA2 , cosθ of 2-jet (2)
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Result
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real clustering signal 4b(opt)remained events 4025 16
significance(evaluated signal & 4b BG only)
1.92σ
real clustering signal 4b(pes)
remained events 3128 24 1.43σ
cheat clustering signal(cheat)
4b(opt)
remained events 22173 165.59σ
cheat clustering signal(cheat)
4b(pes)
remained events 21587 175.49σ
Goodsuppression!!
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Discussion• Significance (signal v.s. single BG) with cheat
jet clustering is good!– signal (cheat) v.s. WW (cheat) : 5.85σ– signal (cheat) v.s. ZZ (cheat) : 5.85σ– signal (cheat) v.s. 4b (optimistic) : 5.59σ– signal (cheat) v.s. 4b (pessimistic) : 5.49σ
• try to apply the NN analyses to all events!
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Topic (2) : Analysis of BG suppression
• Analysis procedure1. pre-selection2. W filter (1st NN selection)3. 4b filter (2nd NN selection)4. Z filter (3rd NN selection)
• Cross-section : WW > 4b > ZZ
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pre-selection• Lorentz factor β2j > 0.05• |cosθ of 2-jet| < 0.99• nbj >= 3– # of b-flavor jets with nsig=3.0 & noffv=1 analysis
• nbtj >= 2– # of b-flavor jets with nsig=3.0 & noffv=2 analysis
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to suppress huge WW BG
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Input parameters to NN• 1st NN selection --- 9 parameters– χH
2 , χZ2 , # of b-flavor jet, etc...
• 2nd NN selection --- 17 parameters– same as page10
• 3rd NN selection --- 10 parameters– χH
2 , χW2 , χZ
2 , etc...
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Details are shown in page24.
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Cut Summaryreal clustering & 4b (optimistic)
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HH WW ZZ 4b(opt)expected events(# of MC events)
80(50000)
73100000(75000000)
59350(1000000)
293600(1000000)
pre-selection 47.93(29958)
81655(83777)
5167(87057)
70851(241318)
W filter 12.34(7713)
8.772(9)
193.4(3259)
318.0(1083)
4b (opt) filter 7.262(4539)
1.949(2)
73.89(1245)
7.340(25)
Z filter 4.823(3018)
0.9747(1)
9.377(158)
3.817(13)
significance=4.823
√4.823+0.9747+9.377+3.817=1.11𝜎PRELIMINARY
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Cut Summaryreal clustering & 4b (pessimistic)
22nd General Meeting @ KEK (2011/9/3) 17
HH WW ZZ 4b(pes)expected events(# of MC events)
80(50000)
73100000(75000000)
59350(1000000)
293600(1000000)
pre-selection 47.93(29958)
81655(83777)
5167(87057)
84491(287776)
W filter 12.34(7713)
8.772(9)
193.4(3259)
568.4(1936)
4b (pes) filter 8.238(5149)
0(0)
84.40(1422)
13.21(45)
Z filter 4.994(3121)
0(0)
7.359(124)
5.872(20)
significance=4.994
√4.994+0+7.359+5.872=1.17𝜎PRELIMINARY
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Cut Summarycheat clustering & 4b (optimistic)
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HH (cheat) WW (cheat) ZZ (cheat) 4b(opt)expected events(# of MC events)
80(50000)
73100000(75000000)
59350(1000000)
293600(1000000)
pre-selection 46.64(29152)
55836(57287)
4172(70292)
70851(241318)
W (cheat) filter 38.58(24115)
4.873(5)
98.94(1667)
1331(4535)
4b (opt) filter 35.56(22223)
3.899(4)
41.78(704)
3.817(13)
Z (cheat) filter 33.26(20787)
1.949(2)
5.045(85)
3.817(13)
significance=33.26
√33.26+1.949+5.045+3.817=5.01𝜎PRELIMINARY
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Cut Summarycheat clustering & 4b (pessimistic)
22nd General Meeting @ KEK (2011/9/3) 19
HH (cheat) WW (cheat) ZZ (cheat) 4b(pes)expected events(# of MC events)
80(50000)
73100000(75000000)
59350(1000000)
293600(1000000)
pre-selection 46.64(29152)
55836(57287)
4172(70292)
84491(287776)
W (cheat) filter 38.58(24115)
4.873(5)
98.94(1667)
2179(7422)
4b (pes) filter 34.50(21562)
2.924(3)
27.66(466)
2.642(9)
Z (cheat) filter 33.06(20662)
2.924(3)
5.935(100)
2.642(9)
significance=33.06
√33.06+2.924+5.935+2.642=4.95𝜎PRELIMINARY
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(Preliminary) Summary• We can observe the Higgs self-coupling with
~5σ if we use cheat jet clustering.• It is possible to measure the Higgs self-
coupling in PLC if we can develop good jet clustering algorithm.
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Next Plan• Check the statistical fluctuation• Check/Evaluate the NN systematic error– Now : (training file) = (test file)
• Write a paper
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Backup slides
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sphericity, Y-value
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normalized momentum tensor Mab
𝑀𝑎𝑏=∑𝑖
𝑝𝑖𝑎𝑝𝑖𝑏/∑𝑖
𝑝𝑖2
pi : momentum of particle i
3*3 matrix
eigenvalue𝑄1 ,𝑄2 ,𝑄3(𝑄¿¿1≤𝑄2≤𝑄3)¿
sphericity=32
(𝑄1+𝑄2 )
Y −value=√32
(𝑄2−𝑄1 )
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Input parameters to NN (details)
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1st --- 9 parametersχH
2 , χZ2 , visible energy, # of tracks, ycut value of jet clustering,
longitudinal momentum, transverse momentum,# of b-flavor jets with nsig = 3.5 & noffv = 1 analysis,# of b-flavor jets with nsig = 3.5 & noffv = 2 analysis
2nd --- 17 parameters
3rd --- 10 parameters
same as page10
χH2 , χW
2 , χZ2 , energy of 2-jet (2), visible energy,
# of tracks, longitudinal momentum# of b-flavor jets with nsig = 3.5 & noffv = 1 analysis,# of b-flavor jets with nsig = 3.5 & noffv = 2 analysis