search for mcp in atlashome.ustc.edu.cn/~windbniw/data/presentation_0.4.pdf · •atlas detectors...
TRANSCRIPT
Search for MCP in ATLAS
ATLAS Collaboration
Reporter: Chuanshun Wei
What’s Particle Physics
2019/5/17 University of Science and Technology of China 2
SUSY Model Super-Kamiokande
What’s Particle Physics
2019/5/17 University of Science and Technology of China 2
• Answering fundamental questions• The structure of matter (Standard Model?)
4th - 5th
centuryBC
End of
19th
century
Beginning of
20th
century
1960s
What’s Particle Physics
2019/5/17 University of Science and Technology of China 2
• Answering fundamental questions• The structure of matter (Standard Model?)
• The origin of Universe (Big Bang?)
4th - 5th
centuryBC
End of
19th
century
Beginning of
20th
century
1960s
What’s Particle Physics
2019/5/17 University of Science and Technology of China 2
• Answering fundamental questions• The structure of matter (Standard Model?)
• The origin of Universe (Big Bang?)
• What is the Universe made of?
(Dark Matter?)
• …
4th - 5th
centuryBC
End of
19th
century
Beginning of
20th
century
1960s
2019/5/17 University of Science and Technology of China 3
• CERN: The largest particle physics lab in the world
Map of the LHC and SPS CERN's main site
CERN and ATLAS
2019/5/17 University of Science and Technology of China 3
• CERN: The largest particle physics lab in the world
• ATLAS: One of the seven particle detector experiments constructed at the Large Hadron Collider (LHC)
Map of the LHC and SPS CERN's main site
CERN and ATLAS
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• ATLAS Detectors get essential information of final-state particle• Track system
• Calorimeters
• Muon Spectrometer
• Magnet system
• Re-build particle tracks• Measure mid-term particle
• Search new particle
Particle Measurement
2019/5/17 University of Science and Technology of China 5
• “Strange” particles:• Fractional-charge particle
• Multi-charged particle
• Particles with large mass
• ……
• Multi-Charged Particle(MCP) is the particles that carry more than 1 charge
• It’s beyond Standard Model, and predicted in several Dark Matter Theory
• Measurement of MCP will provide evidence for different theories and exclude some existing models
Multi-charged Particle
2019/5/17 University of Science and Technology of China 5
• “Strange” particles:• Fractional-charge particle
• Multi-charged particle
• Particles with large mass
• ……
• Multi-Charged Particle(MCP) is the particles that carry more than 1 charge
• It’s beyond Standard Model, and predicted in several Dark Matter Theory
• Measurement of MCP will provide evidence for different theories and exclude some existing models
Multi-charged Particle
2019/5/17 University of Science and Technology of China 5
• “Strange” particles:• Fractional-charge particle
• Multi-charged particle
• Particles with large mass
• ……
• Multi-Charged Particle(MCP) is the particles that carry more than 1 charge
• It’s beyond Standard Model, and predicted in several Dark Matter Theory
• Measurement of MCP will provide evidence for different theories and exclude some existing models
Multi-charged Particle
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• Models• Standard Model : NO MCP
• Almost-commutative Model : 2n e MCP
• Walking Technicolor Model : 2n e MCP
• Left-Right Symmetric Model : doubly charged Higgs boson
• ...
• Signal feature
• highly ionizing: leave an abnormally large ionization signal
• purely electromagnetic coupling: produced in pairs via the Drell–Yan (DY) process
Candidate of MCPs
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• Generate samples for a mass M and with charges ze• Charges: z=2, 3, 4, 5, 6
• Mass: 50 ~ 1000 GeV
• Pair production
• Background• ABCD method:
• Trigger efficiency uncertainty
Search Region and Noise
Overall Uncertainty for several candidates
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• Condition: center-of-mass energy: 13TeV
an integrated luminosity of 36.1𝑓𝑏−1.
• No candidate events with MCPs (2~7 e) were found in allowed error range
Results
2019/5/17 University of Science and Technology of China 8
• Condition: center-of-mass energy: 13TeV
an integrated luminosity of 36.1𝑓𝑏−1.
• No candidate events with MCPs (2~7 e) were found in allowed error range
Results
2019/5/17 University of Science and Technology of China 8
• Condition: center-of-mass energy: 13TeV
an integrated luminosity of 36.1𝑓𝑏−1.
• No candidate events with MCPs (2~7 e) were found in allowed error range
Results
Cross-section upper limits and theoretical cross-sections(95% c.l.)
• Upper limits are derived on cross-sections (95% c.l.) (using a Drell–Yan production model).
• Exclude lepton-like MCPs withmasses lower than 1220 GeV.
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• High energy scale: LHC Upgrade
• Other exotic particles: FCP, heavy particle, dark photon…
• Astronomical observations
• …
Further research
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• Exclude lepton-like multi-charged particles with masses lower than 1220 GeV
• Theories that predict MCP are not applicable to low-enemy situation (<13TeV)
Conclusion
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• Provide experiment data • Possible MCP production check
• Dark-matter theory check
• Standard Model works well
• Search for dark matter can try other methods
Conclusion
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Backup
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• “Long-lived” refers to a particle that does not decay within the ATLAS detector and penetrates its full depth.
• Wherever a charge is quoted for the exotic particles, the charge conjugate state is also implied.
• Simulation software:• MadGraph5
• CETQ6L1
• PYTHIA 8.170
• GEANT4
• RooStats framework
• Barring any new light particles, beyond the Standard Model effects can be studied in Drell-Yan production using an effective field theory
• The results are consistent with the expectation of 0.15±0.05, ±0.10 and 2.9 ± 0.4, ± 2:2×10^-2 background events
Backup
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Backup
Fractions of signal events (in %) with at least one MCP
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BackupEvent Selection Requirements