XAIENCE 2019 - Seoul National University · 2019-11-09 · BDTB : Bagging BDTD : decorrelation +...
Transcript of XAIENCE 2019 - Seoul National University · 2019-11-09 · BDTB : Bagging BDTD : decorrelation +...
Probing Trilinear Higgs Self–coupling at the HL-LHC
with Machine Learning
Collaborators : Prof. Kingman Cheung, Prof. Jae Sik Lee, Dr. Chih-Ting Lu, Dr. Jung Chang
XAIENCE 2019
Jubin ParkIUEP and Chonnam National University
2019. 11. 8. 서울대, 자연대 25-1
Standard Model(표준모형)
https://www.mpoweruk.com/standard_model.htm
http://factmyth.com/the-standard-model-of-particle-physics-explained/
Higgs boson
• Particle physics1. Validation of the Standard Model2. Symmetry breaking of the electroweak interaction3. Particle mass acquisition4. Scalar fields and extension of the Standard Model
• Cosmology1. Inflaton2. Nature of the universe, and its possible fates3. Vacuum energy and the cosmological constant
https://en.wikipedia.org/wiki/Higgs_boson
LHC (Large Hadron Collider)https://youtu.be/pQhbhpU9Wrg
Simulated Large Hadron Collider CMS particle detector data depicting a Higgs boson produced by colliding protons decaying into hadron jets and electron
https://en.wikipedia.org/wiki/Large_Hadron_Collider
The boson's existence was confirmed in 2012 by the ATLAS and CMS collaborations based on
collisions in the LHC at CERN.
1. Higgs couplings to fermions and gauge bosonshave been compatible with SM so far.
2. What happens for the Higgs self-couplings ?
?
Higgs In the SM
• Higgs field (ℎ) : responsible for ① the spontaneous EW symmetry breaking② the generation of masses of all the SM particle
• The potential is characterized by only two parameters :① vacuum expectation value 𝑣② the Higgs mass 𝑚𝐻
𝑣 =1
2 𝐺𝐹
≈ 246 GeV
Trilinear and Quartic Higgs boson couplingin the SM
New Physics can affect the Higgs potential form
Sizeable departures from the SM form
λ3 = λ3𝑆𝑀 + 𝛿λ3
𝑆𝑀 , λ4 = λ4𝑆𝑀 + 𝛿λ4
𝑆𝑀
Trilinear Higgs boson coupling𝝀𝟑 = λ3
𝑆𝑀 + 𝛿λ3𝑆𝑀
Therefore, it is really important to check (or directly measure) this trilinear Higgs coupling to verify that SM is correct.
What do we actually do ?
Outline of Simulations
2015 MadGraph school on Collider Phenomenology November 23-27 @ Shanghai
Parton Showering and Hadronization
Hard Scattering
Detector Simulation b-jet efficiency
c-jet efficiency
ATL-PHYS-PUB-2016-026
Outline of Simulations
2015 MadGraph school on Collider Phenomenology November 23-27 @ Shanghai
Parton Showering and Hadronization
Hard Scattering
Detector Simulation b-jet efficiency
c-jet efficiency
ATL-PHYS-PUB-2016-026
After Detector Simulation (DELPHES)
Analysis
Event selection criteria applied in the analysis
• Cut Based Analysis
• Machine Learning
Multi-Variate Analysis : BDT (Boosted Decision Tree)
(work in progress)
TMVA (Toolkit for Multivariate Data Analysis with ROOT)
Analysis Methods
A. Hoecker, P. Speckmayer, J. Stelzer, J. Therhaag, E. von Toerne, and H. Voss,
TMVA - Toolkit for Multivariate Data Analysis,
PoS ACAT 040 (2007), arXiv:physics/0703039
TMVA Inputs : 8 (kinematic) variables
𝑷𝑻_𝜸𝜸 , 𝑷𝑻_𝒃𝒃 ,𝑴𝜸𝜸 ,𝑴𝒃𝒃 ,𝑴𝜸𝜸𝒃𝒃 , ∆𝑹𝜸𝜸 , ∆𝑹𝒃𝒃 , ∆𝑹𝜸𝒃
BDT : Adaptive BoostBDTG : Gradient BoostBDTB : BaggingBDTD : decorrelation + Adaptive BoostBDTF : allow usage of fisher
discriminant for node splitting
Various ML methods in TMVAIdeal line of ROC curve
AUC = 1
A better direction
BDT-related methods give the best results
BDT machine optimized with
Signal
BDT (response)
cut
Results : Improved
Expected Yieldsand
Significance(Z)
significance Z = 1.05
∴ BDT-improved Z = 1.55
# of signal = 9.63
# of bg = 80.26
# of signal = 6.19
# of bg = 14.04
48% enhancement on Z
Significance of the signal over the background versus λ3𝐻 at the HL-LHC
+0.2 +7.1
95% CL
Conclusion
HL-LHC : constraint the
1. Cut-Based Analysis : -1.1 < λ3𝐻< 7.0 at 95% CL,
Z = 1.05 (λ3𝐻=1)
2. BDT Analysis + NLO_dist : 0.5 < λ3𝐻< 6.8 at 95% CL,
Z = 1.55 (λ3𝐻=1)48%
enhancement on Z
With 3000 fb−1
3. We find a bulk region of 0.5 ≤ λ3𝐻 ≤ 4.5, where it is hard to pin down the trilinear coupling.
• Combined analysis : 𝑏 ത𝑏𝑏ത𝑏 + 𝑏ത𝑏𝛾𝛾 + 𝑏 ത𝑏𝜏𝜏 → Z (≥ 3𝜎 )
• Advanced technology in the future …Increased luminosity, improved tagging efficiency, improved resolution and so on….
• More precise simulation, higher order QCD correction ..Improved MC Event generators (at the NLO, NNLO QCD order),QCD NLO, NNLO, NNNLO corrections …….
Last, but not least
ATL-PHYS-PUB-2018-053
Thank you for your attention !