LHC/LEP

1. CMS SPS LHC/LEP ATLAS THE PHYSICS OF LHC Manfred Jeitler LHCb ALICE

2. БАК (Большой Адронный Коллайдер)

3. THE PHYSICS CASE

4. aims of accelerators • energy frontier • find new particles • learn about basics of interactions • “unification” at higher energies: electroweak interactions, grand unification • cosmology: what the universe looked like soon after the Big Bang • intensity frontier • high-precision experiments

5. VomUrknallbiszum ...?

6. t ne nm nt interactions u c strong g strong g electromagnetic u u d d u d d s b m t e weak W, Z ? gravitation weak force carriers = bosons (spin 1) the Standard Model fermions (spin ½) leptons quarks charge 0 +2/3 -1 -1/3 +1 0 proton neutron baryons

7. completing the Standard Model:the W± and Z0 bosons (1983) CERN SPS

8. completing the Standard Model:the top quark (1995) Tevatron (Fermilab, Chicago)

9. t ne nm nt interactions u c strong g strong g electromagnetic d s b m t e weak W, Z ? gravitation weak the Standard Model fermions (spin ½) leptons quarks charge 0 +2/3 -1 -1/3 Astro Accelerator

10. The Higgs boson For the Standard Model to be consistent, there has to exist one more particle: the Higgs boson. It has not been found yet. However, many other high-precision measurement have confirmed the Standard Model in an impressive way.

11. Peter Higgs in front of LHC-experiment ATLAS

13. the Higgs boson • the Standard Model works only with particles which are originally massless! • mass is created through interaction with a (hypothetical) Higgs field • due to spontaneous symmetry breaking this field is present everywhere in the universe • “oscillations” in the Higgs field manifest themselves as Higgs particles, which should be observed at LHC / CERN over the next few years spontaneous symmetry breaking hot universe (soon after big bang) energy particles are massless cold universe (condensates in an asymmetric state with Higgs field) particles acquire mass 0 Higgs field v

14. The Higgs boson • cannot be lighter than 114.4 GeV/c2 • excluded by direct searches (LEP, “Large Electron-Positron collider, CERN) • some people thought they caught a glimpse of it at LEP (but then LEP was turned off) • should not be too heavy • else problems arise with the physics it’s supposed to explain • maybe “just around the corner” ? • not so good for LHC (“Large Hadron Collider”, CERN): hard to disentangle from background • have to study lots of possible decay channels ! • Fermilab (“Tevatron” collider, Chicago) has been trying hard to find it

15. Supersymmetry (“SUSY”) • another 2 open problems in Standard Model: • “running coupling constants” of electromagnetic, weak and strong interactions meet almost but not completely at the same point • to avoid quadratic divergences in Higgs mass, “fine-tuning” is needed • both problems can be solved by introducing a symmetry between bosons and fermions

16. Supersymmetry SUSY bosons fermions for each known elementary particle there should exist a supersymmetric partner SUSY particles. green: known particles of the Standard Model red: hypothetical new particles

17. dark matter:MACHOS vs WIMPS • massive astrophysical cosmic halo objects? • weakly interacting massive particles? • questions of cosmology to particle physics: • Why is there more matter than anti-matter in the universe? • What is the universe made of? What is dark matter? • What is dark energy? • answers to these questions concerning the largest scales might come from the physics of the smallest scales - elementary particle physics

18. experimental observation of SUSY particles ? SUSY particles may show very clear signatures due to cascade decays Looking for these new supersymmetric particles was/is one of the most important tasks of the major experiments at the Tevatron in Chicago, USA, at the LHC at CERN (Geneva, Switzerland) and at the planned e+ e- linear collider.

19. important questions of today’s particle physics (ongoing experiments) • • Where do particles get their mass from? • (by interaction with the Higgs particle?) • Why are these masses so different? • • Is there an overall (hidden) symmetry such as supersymmetry (SUSY)  “mirror world” of all known particles?. • What is the nature of “dark matter” and “dark energy” in the universe? • • Why is there more matter than anti-matter? • • Why have neutrinos such small mass? • • Is there a Grand Unification which combines all interactions, including gravitation? • • Are there extra dimensions, D > 4 ? ( string theory, …)

20. ACCELERATORS

21. Cockroft-Walton accelerator at CERN

22. inside of an Alvarez-type accelerating structure

23. Synchrotron elements of a synchrotron quadrupole magnet: focussing dipole magnet: to keep particles on track high-frequency accelerating cavity

24. SPS Tunnel Super-Proton-Synchrotron (Geneva)

26. Professor Baikalix Professor Cernix Summer student in Bolshie Koty Astroparticles with 1019 eV !! Collisions at 7 TeV !!

27. quadrupole dipole resonator reaction products interaction zone layout of a circularcollider

28. first electron-electron collider: Novosibirsk / Russia VEP-1 130+130 MeV

29. superconducting RF cavity from LEP

30. +30 MinBias electronsvs.protons

31. elementary particle or not? • electrons (or other leptons): elementary • no substructure • few tracks • sharp energy • protons (hadrons): compounds made up of quarks • what collides is one quark or gluon with another quark or gluon • lots of other “spectators” • mess up the picture • never know collision energy of interacting constituents • only maximum

32. synchrotron radiation • scales with 4th power of Lorentz factor • energy loss per turn: • or

33. velocity

34. synchrotron radiation • to lose less energy you may • make particles heavier (4th power!) • make accelerator bigger (only linear) • electron synchrotron with same losses as LHC : • LHC circumference: 27 km • 27 * 20004 ~ 4 * 1014 km ~ 40 lightyears

36. Collisions at the TeV scale

37. Example: simulated Higgs event LHC ILC e– e+Z H Ze– e+, H b b … –

38. what do you spend your money on(electricity bill)? • electron colliders: accelerating RF-cavities to make up for synchrotron losses • proton colliders: dipole magnets to keep protons on a circular track • conventional (“warm”) magnets: ohmic losses • superconducting magnets: cryogenics • LHC cryogenics: ~30 MW out of total of 180 MW for all of CERN • “there is no such thing as a free lunch”

39. “discovery” vs. “precision” machine • proton colliders are “discovery” machines • proton-antiproton or proton-proton • SPS: W, Z bosons • Super Proton Synchrotron, CERN • Tevatron: top quark • Fermilab, Chicago • LHC, CERN: ??? • Large Hadron Collider • electron-positron colliders allow for precision measurements • LEP: precision measurments of Z mass • Large Electron-Positron Collider, CERN

40. question (homework) • a text in a Cern exhibition states: “the force of the LHC beam is comparable to that of a herd of running elephants” • is this correct? help: • what could be meant by “force”? • momentum? • kinetic energy? • remember the energy and number of particles in LHC • 3.5 TeV, 1011 protons per bunch, ~3000 bunches • how heavy and fast is an elephant? • which kind? Indian / African / Siberian?

41. another question (more homework) • another text says: “the energy of a particle in LHC is the same as that of a flying mosquito” • is this correct? • is there a contradiction to the statement about elephants? help: • how heavy and fast is a mosquito? • Siberian mosquito compared to Indian elephant

42. yet another question (still more homework) • the frequency of the LHC clock at “flat top” (3.5 TeV) is roughly 40 MHz • does the clock frequency at injection (450 GeV) have to be different? • why? • if yes, what is the change of clock frequency during the “ramp” ? • acceleration period, when particle energy and magnetic field rise • could this be a problem?