LHC’s Second Run Hyunseok Lee 1

2 ■ Discovery of the Higgs particle

"for the theoretical discovery of a mechanism that contributes to our understanding of the origin of mass of subatomic particles, and which recently was confirmed through the discovery of the predicted fundamental particle, by the ATLAS and CMS experiments at CERN's Large Hadron Collider." 3 ■ Who made the discovery possible

Oct 2008 LHC Official Inauguration Mar 2010 Proton collision at 7TeV Jul 2012 Discovery of the Higgs particle Feb 2013 Shutdown Apr 2015 Proton collision on 13TeV 4 ■ Now is the Time! We’re here!

LHC 2 nd Run ■ Overview Backgrounds Particle Accelerator The Standard Model Upgrades Beam Magnet & Software New Physics Check of SM Beyond SM Dark Matter Backgrounds Particle Accelerator The Standard Model LHC upgrades Beam Magnet, Software New Physics Check for SM Beyond SM Dark Matter

LHC 2 nd Run 6 ■ Why Particle Accelerator? Backgrounds Particle Accelerator The Standard Model Upgrades Beam Magnet & Software New Physics Check of SM Beyond SM Dark Matter p p p

LHC 2 nd Run 7 ■ Particle is not Walnut Backgrounds Particle Accelerator The Standard Model Upgrades Beam Magnet & Software New Physics Check of SM Beyond SM Dark Matter

LHC 2 nd Run 8 ■ Large Hadron Collider Backgrounds Particle Accelerator The Standard Model Upgrades Beam Magnet & Software New Physics Check of SM Beyond SM Dark Matter Lake Geneva Large Hadron Collider 27 km circumference Large Hadron Collider 27 km circumference CMS ATLAS LHCb ALICE

Accelerates in stages then enters the beam ring LHC 2 nd Run 9 ■ LHC Structure - Accelerator Backgrounds Particle Accelerator The Standard Model Upgrades Beam Magnet & Software New Physics Check of SM Beyond SM Dark Matter ※ Energy of proton mass ~ 1GeV

Proton beams orbit along the beam ring guided by magnets (Lorentz force) Collide at some fixed points LHC 2 nd Run 10 ■ LHC Structure – Beam Ring Backgrounds Particle Accelerator The Standard Model Upgrades Beam Magnet & Software New Physics Check of SM Beyond SM Dark Matter

Detectors track down particles’ trajectory, momentum, energy, … to study the collisions by reconstruction of ‘events’ LHC 2 nd Run 11 ■ LHC Structure - Detector Backgrounds Particle Accelerator The Standard Model Upgrades Beam Magnet & Software New Physics Check of SM Beyond SM Dark Matter

LHC 2 nd Run 12 ■ LHC Structure – Data Flow Backgrounds Particle Accelerator The Standard Model Upgrades Beam Magnet & Software New Physics Check of SM Beyond SM Dark Matter Data Type Position Momentum Energy Etc.

LHC 2 nd Run 13 ■ How does analysis work? Backgrounds Particle Accelerator The Standard Model Upgrades Beam Magnet & Software New Physics Check of SM Beyond SM Dark Matter Particle Accelerator + Detector Simulate the collision based on theory MC sampleData Selection Cut Selected Event Analysis Verification: Compare with theory and preceding analysis Apply Selection code to select events and get distribution of variables p p p p

LHC 2 nd Run 14 ■ Need Theory! Backgrounds Particle Accelerator The Standard Model Upgrades Beam Magnet & Software New Physics Check of SM Beyond SM Dark Matter Particle Accelerator + Detector Simulate the collision based on theory MC sampleData Selection Cut Selected Event Analysis Verification: Compare with theory and preceding analysis Apply Selection code to select events and get distribution of variables So, What is the Theory? p p p p

LHC 2 nd Run 15 ■ The Standard Model (SM) Backgrounds Particle Accelerator The Standard Model Upgrades Beam Magnet & Software New Physics Check of SM Beyond SM Dark Matter

LHC 2 nd Run 16 ■ The Standard Model (SM) Backgrounds Particle Accelerator The Standard Model Upgrades Beam Magnet & Software New Physics Check of SM Beyond SM Dark Matter

LHC 2 nd Run 17 ■ The Standard Model (SM) Backgrounds Particle Accelerator The Standard Model Upgrades Beam Magnet & Software New Physics Check of SM Beyond SM Dark Matter

LHC 2 nd Run 18 ■ The Standard Model (SM) Backgrounds Particle Accelerator The Standard Model Upgrades Beam Magnet & Software New Physics Check of SM Beyond SM Dark Matter

LHC 2 nd Run 19 ■ SM limitation - Gravity Backgrounds Particle Accelerator The Standard Model Upgrades Beam Magnet & Software New Physics Check of SM Beyond SM Dark Matter Black holes, Dark matter, …

Fine-tuning Matching between big and small numbers Does not necessarily mean that the theory is wrong, but some information must be missing. Why it has to be that way? Beyond the Standard Model (BSM) Theories LHC 2 nd Run 20 ■ SM limitation - Naturalness Backgrounds Particle Accelerator The Standard Model Upgrades Beam Magnet & Software New Physics Check of SM Beyond SM Dark Matter

In LHC, protons are accelerated to high energy and collide to provide data for particle physics Based on the successful theory of elementary particles, ‘the Standard Model,’ physicists analyze the data from LHC The Standard Model has limitations, and we’ll see how LHC can help breaking through the limitations. LHC 2 nd Run 21 ■ Summary - Backgrounds Backgrounds Particle Accelerator The Standard Model Upgrades Beam Magnet & Software New Physics Check of SM Beyond SM Dark Matter

Upgraded during 2 years of shutdown Hardware maintenance and repair is done Using the acquired data of the first run, optimized and strengthened experiments. More stable and efficient data acquisition Most importantly, the proton collision energy increased from 8 TeV to 13 TeV LHC 2 nd Run 22 ■ Upgrades Backgrounds Particle Accelerator The Standard Model Upgrades Beam Magnet & Software New Physics Check of SM Beyond SM Dark Matter

Not just like crushing walnut harder! LHC 2 nd Run 23 ■ Higher energy beam Backgrounds Particle Accelerator The Standard Model Upgrades Beam Magnet & Software New Physics Check of SM Beyond SM Dark Matter

Totally new physics might be observed Caveat: the particle’s mass is not necessarily the limit for collision energy LHC 2 nd Run 24 ■ Higher energy beam Backgrounds Particle Accelerator The Standard Model Upgrades Beam Magnet & Software New Physics Check of SM Beyond SM Dark Matter TeV Higgs boson Top quark TeV New particle? New phenomena? … The first run The second run

Much more collision data! LHC 2 nd Run 25 ■ Narrower, Closer Backgrounds Particle Accelerator The Standard Model Upgrades Beam Magnet & Software New Physics Check of SM Beyond SM Dark Matter

Superconducting magnets are essential for guiding the proton beams Repaired magnets Connection that provides alternative path for current Quench-protection system Superior cryogenics LHC 2 nd Run 26 ■ Resilient Magnet Backgrounds Particle Accelerator The Standard Model Upgrades Beam Magnet & Software New Physics Check of SM Beyond SM Dark Matter

1 billion collision/s Most of the collisions are uninteresting, leaving perhaps few hundred collision/s Needs fast filtering algorithm (‘trigger’) to make search efficient and cope with real limitations of data storage LHC 2 nd Run 27 ■ Improved Algorithm Backgrounds Particle Accelerator The Standard Model Upgrades Beam Magnet & Software New Physics Check of SM Beyond SM Dark Matter

LHC 2 nd Run 28 ■ Summary - Upgrades Backgrounds Particle Accelerator The Standard Model Upgrades Beam Magnet & Software New Physics Check of SM Beyond SM Dark Matter Beam Higher energy(8 TeV -> 14 TeV) Narrower beam Closer proton packets Magnet, Software Resilient magnet Improved algorithm Search for new physics with stable and fast data acquisition!

Now, we have numerous BSM theories In the end, a theory should describe the nature that we live in. Experiments can tell what the nature is, and thereby narrow down the BSM candidates that we would focus on further. LHC 2 nd Run 29 ■ New Physics Backgrounds Particle Accelerator The Standard Model Upgrades Beam Magnet & Software New Physics Check of SM Beyond SM Dark Matter

Higgs boson has been discovered, but with limited statistics Still unknown: Multiple Higgs particles, rare decay channel, accurate properties,… Faster data acquisition, increased chance of creating Higgs bosons in collisions Detect small, subtle differences between the Higgs boson in experiment and the prediction of the Standard Model LHC 2 nd Run 30 ■ Check of SM: Higgs boson Backgrounds Particle Accelerator The Standard Model Upgrades Beam Magnet & Software New Physics Check of SM Beyond SM Dark Matter

Each SM particle gets a superpartner Provides natural mechanism to resolve fine-tuning problem Might be able to detect superpartner particle with higher energy beams Study of the properties of new particle will narrow down the supersymmetry models. LHC 2 nd Run 31 ■ Beyond SM: Supersymmetry Backgrounds Particle Accelerator The Standard Model Upgrades Beam Magnet & Software New Physics Check of SM Beyond SM Dark Matter

Constitutes most of the mass of universe Weakly interact with other SM matter Inferred from gravity (motion of galaxy) LHC cannot see it directly, but indirect detection might be possible from missing energy and momentum LHC 2 nd Run 32 ■ Dark Matter Backgrounds Particle Accelerator The Standard Model Upgrades Beam Magnet & Software New Physics Check of SM Beyond SM Dark Matter

LHC’s second run will give us new opportunity to compare our existing theories with the nature Improved data acquisition will help precise study of the Standard Model Higher collision energy might show new particle predicted by some BSM theories Search for the dark matter would benefit the field of cosmology too LHC 2 nd Run 33 ■ Summary – New Physics Backgrounds Particle Accelerator The Standard Model Upgrades Beam Magnet & Software New Physics Check of SM Beyond SM Dark Matter

LHC collides proton pairs to study elementary particles described by Standard Model and to probe into the deeper nature Upgrades enable the search for new physics in a stable and fast manner Physicists expect the new run to guide toward new physics by precise study of SM, providing evidence for BSM, and searching for the dark matter Now in calibration – stay tuned! LHC 2 nd Run 34 ■ Conclusion Backgrounds Particle Accelerator The Standard Model Upgrades Beam Magnet & Software New Physics Check of SM Beyond SM Dark Matter

LHC 2 nd Run 35 ■ Well, since I have more time… Backgrounds Particle Accelerator The Standard Model Upgrades Beam Magnet & Software New Physics Check of SM Beyond SM Dark Matter Backup Slides An Example of Analysis: Higgs Discovery

LHC 2 nd Run 36 ■ Starting Point Backgrounds Particle Accelerator The Standard Model Upgrades Beam Magnet & Software New Physics Check of SM Beyond SM Dark Matter

LHC 2 nd Run 37 ■ The Idea Backgrounds Particle Accelerator The Standard Model Upgrades Beam Magnet & Software New Physics Check of SM Beyond SM Dark Matter Thus, we can try to reconstruct the Higgs boson from final particle candidates, while the reconstructed mass is allowed within the limits. Problem: We cannot say that the Higgs boson exists just because the final particles could make it – they could be from other process! Answer: Gather statistics, and compare rates of the Higgs events vs the other events!

LHC 2 nd Run 38 ■ Procedure Backgrounds Particle Accelerator The Standard Model Upgrades Beam Magnet & Software New Physics Check of SM Beyond SM Dark Matter Particle Accelerator + Detector Simulate the collision based on theory MC sampleData Selection Cut Selected Event Analysis Verification: Compare with theory and preceding analysis Apply Selection code to select events and get distribution of variables p p p p

LHC 2 nd Run 39 ■ What do we analyze? Backgrounds Particle Accelerator The Standard Model Upgrades Beam Magnet & Software New Physics Check of SM Beyond SM Dark Matter The rate of MC sample events with or without Higgs boson, and compare them with the real data “Observation of a new particle in the search for the Standard Model Higgs boson with the ATLAS detector at the LHC”, ATLAS Collaboration, Phys.Lett.B.(2012)