Download - Higgs Branching Ratio H→bb, cc, gg
![Page 1: Higgs Branching Ratio H→bb, cc, gg](https://reader030.vdocuments.site/reader030/viewer/2022012811/61c2466e7db7de5414371b11/html5/thumbnails/1.jpg)
Higgs Branching RatioH→bb, cc, gg
for new detector models at ILDMasakazu Kurata, Ryo Yonamine, Hiroaki Ono
ILD meeting
02/27/2019
![Page 2: Higgs Branching Ratio H→bb, cc, gg](https://reader030.vdocuments.site/reader030/viewer/2022012811/61c2466e7db7de5414371b11/html5/thumbnails/2.jpg)
Introduction • Start to re-optimize new detector models using physics
benchmarks
• Higgs analyses are one of the most important benchmark processes for detector optimization at ILD
• H→bb, cc, gg measurement:• Flavor tagging is indispensable for jet flavor separation
• Try@500GeV, focus on ννH process
• Based on Hiroaki’s 1TeV analysis in DBD era
• So far, do not consider separation of ZH and VBF• But, considering it for future plan
2
![Page 3: Higgs Branching Ratio H→bb, cc, gg](https://reader030.vdocuments.site/reader030/viewer/2022012811/61c2466e7db7de5414371b11/html5/thumbnails/3.jpg)
LCFIPlus summary: Comparison among any situation• Ryo made great efforts to resolve internal problems in
LCFIPlus for new verson of iLCsoft
• Use 6f flavor tag samples: bbbbbb, cccccc, qqqqqq
• Tune MVA training torecover performance tothose of DBD era
• Almost same performanceas DBD era
3
![Page 4: Higgs Branching Ratio H→bb, cc, gg](https://reader030.vdocuments.site/reader030/viewer/2022012811/61c2466e7db7de5414371b11/html5/thumbnails/4.jpg)
Comparison between large and small• MVAoutput between large and small
• Very similar…
4
![Page 5: Higgs Branching Ratio H→bb, cc, gg](https://reader030.vdocuments.site/reader030/viewer/2022012811/61c2466e7db7de5414371b11/html5/thumbnails/5.jpg)
but
5
Small has excess hereAll the jet flavors have excess
![Page 6: Higgs Branching Ratio H→bb, cc, gg](https://reader030.vdocuments.site/reader030/viewer/2022012811/61c2466e7db7de5414371b11/html5/thumbnails/6.jpg)
After selectionLargesmall
Check samples• Check nnH→nncc sample
• Compare MVAoutput between Large and Small
• Same tendency can be seen• This excess directly reflects on measurement precision
• No bias on c-jet likeliness from:• Event selection
• Beam background rejection
6
![Page 7: Higgs Branching Ratio H→bb, cc, gg](https://reader030.vdocuments.site/reader030/viewer/2022012811/61c2466e7db7de5414371b11/html5/thumbnails/7.jpg)
Status of analysis
Iso
late
d L
epto
n ID Look for
electron and muon
Jet
Clu
ster
ing Durham with beam background rejection
2 jet clustering
Even
t se
lect
ion Reject
backgrounds
Preselection
MVA
Polarization (e-, e+)=(-,+) (+,-) (-,-) (+,+)
Luminosity(fb-1) 1600 1600 400 400
• ECM=500GeV• Luminosity: 4ab-1
• Analysis flow
• Signal and backgrounds• Signal: use nnH→nnbb, nncc, nngg• Backgrounds: 2f, 4f, 5f, 6f, aa, ZH, nnh→nn(no bb,cc,gg) 7
![Page 8: Higgs Branching Ratio H→bb, cc, gg](https://reader030.vdocuments.site/reader030/viewer/2022012811/61c2466e7db7de5414371b11/html5/thumbnails/8.jpg)
Beam background rejection
• 𝑦𝑖𝑗 =2min(𝐸𝑖
2, 𝐸𝑗2)(1−cos 𝜃)
𝐸𝑣𝑖𝑠2 , 𝑦𝑏𝑒𝑎𝑚 =
2𝐸𝑖2α2(1−cos 𝜃)
𝐸𝑣𝑖𝑠2
α: beam rejection parameter
smaller→ beam rejection becomes stronger• Particle i with yij>ybeam is discarded
8
ννZ@500GeV(DBD) • 2 jet clustering• Parameters are tuned
for better result
w/o beam b.g. rejectionKtDurhamValencia
![Page 9: Higgs Branching Ratio H→bb, cc, gg](https://reader030.vdocuments.site/reader030/viewer/2022012811/61c2466e7db7de5414371b11/html5/thumbnails/9.jpg)
Apply to nnH events• Apply Durham beam b.g. rejection to nnH→nnbb
events
• Parameter scan to make Higgs mass distribution better• 5.5 seems best for both detector models
large small
9
![Page 10: Higgs Branching Ratio H→bb, cc, gg](https://reader030.vdocuments.site/reader030/viewer/2022012811/61c2466e7db7de5414371b11/html5/thumbnails/10.jpg)
Preselection
10
• Just reject backgrounds which are trivial ones• Signal tail part of each variable is rejected
• No Isolated lepton
• Njets=2
• Npfo≧5
• Evis≦300
• 40≦m2jets≦200
![Page 11: Higgs Branching Ratio H→bb, cc, gg](https://reader030.vdocuments.site/reader030/viewer/2022012811/61c2466e7db7de5414371b11/html5/thumbnails/11.jpg)
Multivariate Analysis
• Expect better background rejection efficiency than cut based
• Need to reject other Higgs processes as much as SM backgrounds
• Important to separate both SM backgrounds and other Higgs processes for backgrounds
• Use Binary Classification• Due to the phase space difference of each background
component
• Signal vs.: other Higgs, 2f&4f, 5f&6f&aa
• 3kinds of classifier trained
11
![Page 12: Higgs Branching Ratio H→bb, cc, gg](https://reader030.vdocuments.site/reader030/viewer/2022012811/61c2466e7db7de5414371b11/html5/thumbnails/12.jpg)
Input variables• Need to suppress bias between H→bb,cc and H→gg
• Reduce difference by combining variables• m2jets, cosθH, cosθjj, Ej1, cosθj1, Ej2, cosθj2, mmiss, Pt,
Principal Thrust, Major Thrust, Log(y23)*npfo, Log(y34)*npfo
• Example: signal vs. 2f&4f
12
![Page 13: Higgs Branching Ratio H→bb, cc, gg](https://reader030.vdocuments.site/reader030/viewer/2022012811/61c2466e7db7de5414371b11/html5/thumbnails/13.jpg)
Stacked
13
vs. other Higgs vs. 2f&4f
vs. 5f&6f&aa
• Determine operation point:MVA_1>x.xx && MVA_2>y.yy && MVA_3>z.zz
![Page 14: Higgs Branching Ratio H→bb, cc, gg](https://reader030.vdocuments.site/reader030/viewer/2022012811/61c2466e7db7de5414371b11/html5/thumbnails/14.jpg)
Cut table• Large, (e-, e+)=(-,+) polarization,
L=1600fb-1
Signal efficiency: typically ~60% for all the polarization & detector models
Significance: 275.3
14
![Page 15: Higgs Branching Ratio H→bb, cc, gg](https://reader030.vdocuments.site/reader030/viewer/2022012811/61c2466e7db7de5414371b11/html5/thumbnails/15.jpg)
Template fit• Toy MC to extract the measurement precision of H→bb,
cc, gg• From LCFIPlus output, calculate x-likeliness in each event:
x1, x2: LCFIPlus output(b, c, bc=c/(b+c))
• Create 3-D template with those b, c, bc likeliness
• Fitting is performed according to Poisson statistics• 3 scale factors of signal events are parameters, other fixed:
• Do Toy MC• 10000 pseudo-experiments performed
15
![Page 16: Higgs Branching Ratio H→bb, cc, gg](https://reader030.vdocuments.site/reader030/viewer/2022012811/61c2466e7db7de5414371b11/html5/thumbnails/16.jpg)
Template examples• Templates are 3-D, so project into 2-D space
16
![Page 17: Higgs Branching Ratio H→bb, cc, gg](https://reader030.vdocuments.site/reader030/viewer/2022012811/61c2466e7db7de5414371b11/html5/thumbnails/17.jpg)
Results• Large detector, all the polarization
• Small detector, all the polarization
• Comparison with DBD for check• (-0.8, +0.3) 500fb-1
17
Process(-,+) H→bb H→cc H→gg
Precision(%) 0.69 6.79 2.89
Process(-,+) H→bb H→cc H→gg
Precision(%) 0.66 6.2 4.1
IDR-L DBD(125GeV scaled)
![Page 18: Higgs Branching Ratio H→bb, cc, gg](https://reader030.vdocuments.site/reader030/viewer/2022012811/61c2466e7db7de5414371b11/html5/thumbnails/18.jpg)
Plot• Results of branching ratio measurement
18
![Page 19: Higgs Branching Ratio H→bb, cc, gg](https://reader030.vdocuments.site/reader030/viewer/2022012811/61c2466e7db7de5414371b11/html5/thumbnails/19.jpg)
Plot• Combined only
19
![Page 20: Higgs Branching Ratio H→bb, cc, gg](https://reader030.vdocuments.site/reader030/viewer/2022012811/61c2466e7db7de5414371b11/html5/thumbnails/20.jpg)
• We construct pseudo jet flavor taggers for comparison
• We do the pseudo experiments with those (artificially) perfect & pessimistic case
• Artificial fraction• Perfect Pessimistic
• According to those fraction, jet flavor is determined• All the samples are processed, and measurement precision is
estimated
Impact of flavor tagging on precision measurement
20
![Page 21: Higgs Branching Ratio H→bb, cc, gg](https://reader030.vdocuments.site/reader030/viewer/2022012811/61c2466e7db7de5414371b11/html5/thumbnails/21.jpg)
• (-,+) polarization, L=1600fb-1
• Better flavor tagging is very important for better precision• b-tagging is excellent• Better c-tagging is important
Comparison between pseudo experiments
21
![Page 22: Higgs Branching Ratio H→bb, cc, gg](https://reader030.vdocuments.site/reader030/viewer/2022012811/61c2466e7db7de5414371b11/html5/thumbnails/22.jpg)
Plot• Impact of flavor tagging performance on measurement
22
![Page 23: Higgs Branching Ratio H→bb, cc, gg](https://reader030.vdocuments.site/reader030/viewer/2022012811/61c2466e7db7de5414371b11/html5/thumbnails/23.jpg)
Summary & Prospects• We can get the results of both detectors & all the
polarizations• B-tagging is very excellent already
• Small detector has better performance than large in H→cc measurement
• Coming from c-tag output distribution
• Thanks to stronger B-field(4.0T>3.5T)?
• We will investigate that point
• Template fitting is being checked now• We cannot see huge bias on binning so far(backup)
• Checking and discussing fitting stability with reviewers now
• Note & Going to IDR input23
![Page 24: Higgs Branching Ratio H→bb, cc, gg](https://reader030.vdocuments.site/reader030/viewer/2022012811/61c2466e7db7de5414371b11/html5/thumbnails/24.jpg)
Backups
24
![Page 25: Higgs Branching Ratio H→bb, cc, gg](https://reader030.vdocuments.site/reader030/viewer/2022012811/61c2466e7db7de5414371b11/html5/thumbnails/25.jpg)
MVA output
25
vs. other Higgs vs. 2f&4f
vs. 5f&6f&aa
![Page 26: Higgs Branching Ratio H→bb, cc, gg](https://reader030.vdocuments.site/reader030/viewer/2022012811/61c2466e7db7de5414371b11/html5/thumbnails/26.jpg)
• large
26
![Page 27: Higgs Branching Ratio H→bb, cc, gg](https://reader030.vdocuments.site/reader030/viewer/2022012811/61c2466e7db7de5414371b11/html5/thumbnails/27.jpg)
• small
27
![Page 28: Higgs Branching Ratio H→bb, cc, gg](https://reader030.vdocuments.site/reader030/viewer/2022012811/61c2466e7db7de5414371b11/html5/thumbnails/28.jpg)
Check template fit• Need to check
• Num. of empty bins: must be as small as possible
• Bins with small statistics: need to avoid
Should be checked
• Num. of binning is important• To include the shape effect
• This is the advantage of template fit
• The tendency of template binning:• b-likeliness is very robust: num. of bin is 2 enough
• H→gg is relatively robust: don’t need much care about (b, c, bc)=(0.0,0.0,0.0) value
• Shape of c & bc-likeliness is very important
⇒H→cc precision varies very much 28
![Page 29: Higgs Branching Ratio H→bb, cc, gg](https://reader030.vdocuments.site/reader030/viewer/2022012811/61c2466e7db7de5414371b11/html5/thumbnails/29.jpg)
One case• Num. of bins: (b-, c-, bc-)=(2,3,3) (LCWS: (10,10,10))
• Variable bin size is used(LCWS: 0.1 interval from 0 to 1)
• Check the bin stat. (all the events accumulated)
29
b-likeliness<0.4Num. of empty bins: 2Smallest stat: 1072
b-likeliness>0.4Num. of empty bins: 7Smallest stat: 904.8
![Page 30: Higgs Branching Ratio H→bb, cc, gg](https://reader030.vdocuments.site/reader030/viewer/2022012811/61c2466e7db7de5414371b11/html5/thumbnails/30.jpg)
More aggressive case• Num. of bins: (b-, c-, bc-)=(2,5,5) to include shape info more
• Variable bin size is used
• Check the bin stat. (all the events accumulated)• Typically, num. of events in a bin is >~100
30
b-likeliness<0.4Num. of empty bins: 10Smallest stat: 98.1
b-likeliness>0.4Num. of empty bins: 19Smallest stat: 11.0
![Page 31: Higgs Branching Ratio H→bb, cc, gg](https://reader030.vdocuments.site/reader030/viewer/2022012811/61c2466e7db7de5414371b11/html5/thumbnails/31.jpg)
Check different binning effect• (e-,e+)=(-,+),L=1600fb-1
• Large:
• Small:
• Small is better for c-tagging• Results does not change so drastically, but H→cc varies if shape info includes more(have to be
careful of statistics)• Zero bins do not affect well• We use (2,5,5) binning for result
31
Large(10,10,10) H→bb H→cc H→gg
Precision(%) 0.43 3.80 1.68
Large(2,3,3) H→bb H→cc H→gg
Precision(%) 0.43±0.01 3.98±0.02 1.76±0.01
Small(2,3,3) H→bb H→cc H→gg
Precision(%) 0.43±0.01 3.69±0.02 1.81±0.01
Small(10,10,10) H→bb H→cc H→gg
Precision(%) 0.42 3.55 1.73
Large(2,5,5) H→bb H→cc H→gg
Precision(%) 0.43±0.01 3.88±0.02 1.70±0.01
Small(2,5,5) H→bb H→cc H→gg
Precision(%) 0.44±0.01 3.56±0.02 1.77±0.01
![Page 32: Higgs Branching Ratio H→bb, cc, gg](https://reader030.vdocuments.site/reader030/viewer/2022012811/61c2466e7db7de5414371b11/html5/thumbnails/32.jpg)
Optimization with 2 detector models
• Re-optimize ILD detector• Revisit optimization of cost and detector performance
Detector models ILD-L ILD-S
B-field 3.5T 4T
VTX inner radius 1.6cm 1.6cm
TPC inner radius 33cm 33cm
TPC outer radius 180cm 146cm
TPC length (z/2) 235cm 235cm
Inner ECAL radius 184cm 150cm
Outer ECAL radius 202.5cm 168.5cm
Inner HCAL radius 206cm 172cm
Outer HCAL radius 335cm 301cm
Coil inner radius 344cm 310cm
ILD-L ILD-S
32
![Page 33: Higgs Branching Ratio H→bb, cc, gg](https://reader030.vdocuments.site/reader030/viewer/2022012811/61c2466e7db7de5414371b11/html5/thumbnails/33.jpg)
Check samples• Beam background rejection?
• No bias from beam background rejection
33
Before beam b.g. rejectionLargeSmall