AA->HH Study AA->4b analysis & (preliminary) Summary Shin-ichi Kawada (AdSM, Hiroshima University)...
-
Upload
carol-barber -
Category
Documents
-
view
221 -
download
0
description
Transcript of AA->HH Study AA->4b analysis & (preliminary) Summary Shin-ichi Kawada (AdSM, Hiroshima University)...
AA->HH StudyAA->4b analysis & (preliminary) Summary
Shin-ichi Kawada(AdSM, Hiroshima University)
22nd General Meeting @ KEK (2011/9/3) 1
Outline• Introduction• Previous results• Today’s topic– AA->4b BG analysis– analysis of BG suppression (AA->WW, ZZ, 4b)
• Summary & Next plan
22nd General Meeting @ KEK (2011/9/3) 2
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.
22nd General Meeting @ KEK (2011/9/3) 3
About PLC
22nd General Meeting @ KEK (2011/9/3) 4
Electrons
Backward Compton scattering
ILC : e+ e- collision PLC : gamma-gamma collision
gamma-gamma collision
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.
22nd General Meeting @ KEK (2011/9/3) 5
4b = b b-bar b b-bar
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.
22nd General Meeting @ KEK (2011/9/3) 6
BG usual cheatAA->WW 2.69 5.85AA->ZZ 1.61 5.85
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
Topic (1) : AA->4b BG analysis
22nd General Meeting @ KEK (2011/9/3) 8
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
Analysis procedure (1)• MC samples– remained events after W filter & Z filter
22nd General Meeting @ KEK (2011/9/3) 9
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
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)
22nd General Meeting @ KEK (2011/9/3) 10
Result
22nd General Meeting @ KEK (2011/9/3) 11
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!!
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!
22nd General Meeting @ KEK (2011/9/3) 12
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
22nd General Meeting @ KEK (2011/9/3) 13
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
22nd General Meeting @ KEK (2011/9/3) 14
to suppress huge WW BG
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...
22nd General Meeting @ KEK (2011/9/3) 15
Details are shown in page24.
Cut Summaryreal clustering & 4b (optimistic)
22nd General Meeting @ KEK (2011/9/3) 16
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
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
Cut Summarycheat clustering & 4b (optimistic)
22nd General Meeting @ KEK (2011/9/3) 18
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
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
(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.
22nd General Meeting @ KEK (2011/9/3) 20
Next Plan• Check the statistical fluctuation• Check/Evaluate the NN systematic error– Now : (training file) = (test file)
• Write a paper
22nd General Meeting @ KEK (2011/9/3) 21
Backup slides
22nd General Meeting @ KEK (2011/9/3) 22
sphericity, Y-value
22nd General Meeting @ KEK (2011/9/3) 23
normalized momentum tensor Mab
𝑀 𝑎𝑏=∑𝑖𝑝𝑖𝑎𝑝𝑖𝑏/∑
𝑖𝑝𝑖2
pi : momentum of particle i
3*3 matrix
eigenvalue𝑄1 ,𝑄2 ,𝑄3(𝑄¿¿1≤𝑄2≤𝑄3)¿
sphericity=32 (𝑄1+𝑄2 )
Y −value=√32 (𝑄2−𝑄1 )
Input parameters to NN (details)
22nd General Meeting @ KEK (2011/9/3) 24
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