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The Higgs Boson: What is it? Have we found it
- 1. The Higgs Boson: What is it? Have we found it? Michael Tuts Columbia University Cambridge/MIT Alumni December 4, 2012
- 2. A Journey to the Domain of Par=cle Physics 10-‐12 meter 1 m m eter 10-‐14eter -‐2 -‐6 -‐1 -‐16 10 -‐9 -‐15 meter -‐5 -‐3 -‐4 -‐7 -‐8 -‐13 meter -‐11 -‐10 3 Carbon A Skinurface loud Skin White uarks lectrons Within Skin tructure roton cCarbon mersonn ell olored onhucleusdetail pAtomic trandsp c DNA uter e i C A q elood Cell mpore DNA ucleus ore ipn and nner n Proton’s sucleus DNA sicro-‐organism slectron the Bolecules
- 3. Nucleus 0.000000000000001 meters or 10-‐15 m “Colored” Quarks (not to scale!) <0.0000000000000000001 meters or <10-‐19 m
- 4. The “Standard Model” of Par=cle Physics Ordinary maTer (planets, us!) is made of this first generaYon of quarks and leptons
- 6. Very heavy! Very light! Massless! Very heavy! Higgs “mechanism” provides a way they should all But our simplest theory would s ay to explain why the massless! par=cles have different weights be elementary (masses)… How?
- 7. An analogy…
- 9. How can we answer this ques=on – does the Higgs Boson exist and can we prove it? The Tools for explora=on 1. Create a Higgs in the debris of par=cle collisions – use the Large Hadron Collider 2. Search for the Higgs in that debris – use the ATLAS detector as a microscope to explore the subatomic world
- 11. Proton-‐proton collisions at 7TeV per beam At the CERN lab in Geneva Switzerland 17mile long tunnel, 300 feet underground, 1,200 magnets
- 15. The ATLAS Detector is big, very big • 80 c tall, 147 c long, 7,000 tons, 100 Million channels of electronics
- 16. How big is ATLAS? … very • 100 million channels of electronics • 80 c tall • 140 c long • 7,000 tons • 3,000 physicists (incl. ~1,000 graduate students) • 38 countries • 175 ins=tu=ons
- 18. Think of the ATLAS detector as a 100 megapixel digital camera • 100 million channels of electronics • We take electronic “pictures” (called events) • We take 40 million “pictures” per second • We analyze these “pictures” using a worldwide network of 50,000 computers • We have wrigen already ~40 PB of data (40,000,000 Gigabytes!) LHC #6 by Jonathan Feldschuh (2008) The problem • A total 1 billion collisions per second • Most are “uninteres=ng”, so need to decide and discard quickly, can only afford to save 200 per second • For example, Z boson – 15 per second • For example, Higgs boson – one every 5 LHC #26 by Jonathan Feldschuh seconds
- 19. How do you classify “pictures” as interes=ng or less interes=ng? Can you tell the difference between these two?
- 20. An ATLAS “Picture” … maybe a Higgs? ZZ→e+e-‐µ+µ-‐ This could be a Higgs event … or more mundane… need more data to tell for sure
- 21. Another possible Higgs candidate events the Higgs decaying into two photons H→ γγ
- 22. How do we find the Higgs? Is one enough?
- 23. So what do we see in the actual data? Combine the 2 photons according to Einstein’s equa=ons to tell us the weight (mass) of the parent par=cle For mH=126.5 ± 2 GeV: observed: 3693 events expected from B: 3635 expected from SM Higgs: 100 Signal/Background ~ 3% 1015 (=1,000,000,000,000,000)“pictures” taken Around the “bump” about 3,700 “pictures” of which about 100 correspond to the new par=cle
- 25. If it is Higgs – do we see it produced at the rate we expect from theory?
- 26. Are we done – is this the end? No! It is a new beginning! This is not “just” a new par=cle – a Higgs would be unlike any we have ever seen before Is it a Higgs Boson? Not completely sure yet… Is it produced as ocen as we expect? Does it decay as we expect? Are its other proper=es, like “spin”, as predicted? So far looks like it … but we will be accumula=ng even more data
- 27. It’s not just Higgs! The stuff we are made of – the Standard Model I described -‐ makes up a mere 4% of the universe There are many open ques=ons we may be able to tackle… What is dark Mager? Are there new symmetries and par=cles? What is the nature of space-‐=me itself? Something we never thought of? Exploring this new energy fron=er is like Columbus sesng sail across the Atlan=c – will we find America, India or a new con=nent?
- 28. People Columbia U• niversity group on ATLAS June 2012 – 38 countries – 176 insYtuYons (including Cavendish, Cambridge U) – 3,054 authors • In the U.S. – 43 insYtutes: Albany, ANL, Arizona, UT Arlington, Berkeley LBL and UC, Boston, Brandeis, BNL, Chicago, Columbia, UT Dallas, Duke, Fresno State, Hampton, Harvard, Indiana, U Iowa, Iowa State, UC Irvine, Louisiana Tech, MassachuseTs, MIT, Michigan, MSU, New Mexico, NIU, NYU, Ohio State, Oklahoma, Oklahoma State, Oregon, Pennsylvania, PiTsburgh, UC Santa Cruz, SLAC, SMU, South Carolina, SUNY Stony Brook, Tuhs, Illinois Urbana, Washington, Wisconsin, Yale – 592 authors
- 29. The Large Hadron Rap – abridged (6M hits on You Tube)
- 30. Come join us on this journey! • If you are in kindergarten or beyond we will need you…become a parYcle physicist and join ATLAS! • In Geneva? Come visit us at CERN (hTp://outreach.web.cern.ch/outreach/visits/) • Follow us on TwiTer (twiTer.com/ATLASexperiment), Facebook ( facebook.com/group.php?v=wall&gid=23271817589), You Tube ( www.youtube.com/theATLASExperiment) – even a LHC rap video ( youtube.com/watch?v=j50ZssEojtM), Blogs (uslhc.us and atlas.ch/blog/) • Watch events live as they are collected (atlanYs.cern.ch/live/) • Want to learn more? Keep your ATLAS pop-‐up book handy ( hTp://www.facebook.com/pages/Pop-‐up-‐Voyage-‐to-‐the-‐Heart-‐of-‐MaTer/153102255147 ) as you navigate the ATLAS website www.atlas.ch • Oh…and we even have a line of ATLAS clothing and cool toys – caps, fleeces, Yes, 3D-‐viewers, puzzles, cards,… (atlas.ch/store.html)
- 32. … but the Higgs mechanism leaves us another puzzle -‐ why is the Higgs so light? (“Hierarchy problem”) The Fix: -‐ either very finely tuned cancella=on (just luck!) OR -‐ introduce a new idea like SUPERSYMMETRY (SUSY) The Price: -‐ double the number of elementary par=cles, none of which have been seen!
- 33. The Bonus: -‐ Besides “fixing” problems with SM -‐ It might be that the lightest SUSY par=cle is dark mager! -‐ String theories require them! We won’t We might have discove much r this at to say the LHC about this This is us (the standard model)
- 34. But what about the force of gravity? … It wasn’t in our Standard Model The Problem – We know how it behaves at large distances – Einstein’s Theory of General Rela=vity tells us how – At small distances quantum theory is important and we have no tested theory of quantum gravity (for all they other forces we do have a quantum theory) – Why is it so weak? (is it weak? You can do the demo at home!) The Solu=on…perhaps – Maybe, just maybe, String Theory or string theory inspired ideas are the answer Our experimental problem – Do we have any hope of tes=ng it?
- 35. An analogy… on why we don’t feel those other dimensions
- 37. • High-‐energy proton collisions • Can release enough energy • To create new, heavy par=cles 'Children learn about the world much as scienYsts do-‐-‐smashing things to smithereens, staring in wonder at the results and then breaking out in giggles’