Particle Physics at

the LHC Era

Tianjun Li

ITP, CAS

ICTS, USTC, March 22, 2013

Outline

• Introduction to the Standard Model (SM)

• Theoretical Overiew for New Physics (NP)

• LHC Higgs Searches

• LHC Supersymmetry Searches

• Implications for Supersymmetric SMs

• Summary

2

I. Introduction to the SM

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Physicists

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Higgs Mechanism

3 Goldstone bosons are eaten by gauge bosons

what left is a Higgs boson.

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Gauge Hierarchy Problem

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II. Theoretical Overview for NP

• New Particles

• New Gauge Symmetries

• Global Symmetry Breaking

• Supersymmetry

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New Particles

• Vector-Like Fermions

• Singlet Boson or Higgs Fields

• Doublet Boson or Higgs Fields

• Triplet Higgs Fields

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New Gauge Symmetries

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(1) U(1)’ Models:

(2) SU(2)’ Models:

(3) Top Color Models

(4) Top SU(5) Models

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B or L Symmetry Breaking

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Supersymmetry

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Particle Spectrum

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Gauge Coupling Unification

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III. LHC Higgs Searches

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8cm length & 16*10-4 cm radius

Event rate:

N = L x (pp) 109 interactions/s

Mostly soft (low pT) events

Interesting hard (high-pT) events are rare

very powerful detectors needed

41

ATLAS in Brief

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NJU

SDU

IHEP, USTC

CMS similarities

General purpose CMS designed with equivalent performance

as ATLAS while independent cross check is essential 43

Higgs Production

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Higgs Decays

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Higgs Decays to Diphoton

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IV. LHC Supersymmetry Searches

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Squarks and Gluino Productions

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Squarks and Gluino Productions

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Electroweak Particle Productions

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Production Cross Sections

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Tau+Jets+MET(ATLAS-CONF-2013-026) (20.7/fb)

2SSL+Jets+MET(ATLAS-CONF-2013-007)(20.7/fb)

V. Implications for Supersymmetric

SMs

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VI. Summary

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