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Physics at Future High Energy Colliders

Physics at Future High Energy Colliders. Albert De Roeck/CERN Strasbourg 7-8/07/06. Lecture Plan. L E C T U R E 1. Brief introduction: The Era of the New Machines Physics at the Large Hadron Collider LHC Experimental challenges The hunt for the Higgs particle

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Physics at Future High Energy Colliders

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  1. Physics at Future High Energy Colliders Albert De Roeck/CERN Strasbourg 7-8/07/06

  2. Lecture Plan L E C T U R E 1 • Brief introduction: The Era of the New Machines • Physics at the Large Hadron Collider LHC • Experimental challenges • The hunt for the Higgs particle • Signals of new physics at the TeV scale • Options for future colliders • The LHC upgrade • An e+e- linear collider (LC) • A Very Large Hadron Collider (VLHC) • A Muon Collider L E C T U R E 2

  3. SM SUSY Physics case for new High Energy Machines Understand the mechanism Electroweak Symmetry Breaking Discover physics beyond the Standard Model Reminder: The Standard Model - tells us how but not why 3 flavour families? Mass spectra? Hierarchy? - needs fine tuning of parameters to level of 10-30 ! - has no connection with gravity - no unification of the forces at high energy If a Higgs field exists: - Supersymmetry - Extra space dimensions If there is no Higgs below ~ 700 GeV - Strong electroweak symmetry breaking around 1 TeV … Most popular extensions these days

  4. Beyond the Standard Model New physics expected around the TeV scale  Stabelize Higgs mass, Hierarchy problem, Unification of gauge couplings, CDM,… Supersymmetry Extra dimensions +… + a lot of other ideas… Split SUSY, Little Higgs models, new gauge bosons, technicolor, compositness,..

  5. BSM Physics at the LHC: pp @ 14 TeV New Gauge Bosons? ZZ/WW resonances? Technicolor? Supersymmetry? Little Higgs? Split Susy? Extra Dimensions? Black Holes??? Impressive variety of proposals for physics that can be expected @ LHC !!!

  6. Example of new physics Plot the di-lepton invariant mass A peak!! A new particle!! A discovery!! May be seen very early: E.g. first weeks of operation of the machine

  7. f H - f Fermion and boson loops cancel, provided m  TeV. Supersymmetry Supersymmetry (SUSY)  assumes a new hidden symmetry between the bosons (particles with integer spin) and fermions (particles with half integer spin). Stabelize the Higgs mass up to the Planck scale

  8. Supersymmetry • Lots of new particles (squarks, sleptons,…) predicted with masses in the range from 10’s of GeV’s up to several TeV range • Supersymmetry is broken • We don’t see the superpartners • E.g. Minimal Supersymmetric Model •  O(100) new parameters! masses, mixing angles… • SUSY breaking mechanisms: reduces # of param. • Minimal SUSY Gravity (mSUGRA) • Gauge mediated SUSY breaking • Anomaly mediated SUSY breaking • Gravitino mediated SUSY breaking… etc. More than 7000 papers since 1990 Lightest SUSY particle stable: dark matter candidate ?

  9. Supersymmetry A VERY popular benchmark… "One day, all of these will be supersymmetric phenomenology papers." More than 7000 papers since 1990

  10. Why weak-scale SUSY ? • stabilises the EW scale: |mF – mB | < O(1 TeV) • predicts a light Higgs mh< 130 GeV • predicts gauge unification • accomodates heavy top quark • dark matter candidate: neutralino, sneutrino, gravitino, ... • consistent with EW data Discovering SUSY – A revolution in particle physics!! • the outcome of LHC is far more important than any other in the past • all future projects: ILC, superB, super..., depend on LHC discoveries • huge responsibility to provide quick and reliable answers

  11. SUSY program for the experimentalist • Understand the detector and the Standard Model Backgrounds • Establish an excess  Discover a signal compatible with supersymmetry • Measure sparticle masses • Measure sparticle production cross sections, branching ratios, couplings • Look for more difficult sparticle signatures hidden in the data • Is it really SUSY? Try to check eg. the spin of the new particles • Turn the pole mass measurements into MSSM Lagrangian parameters of the model • Map the measurements to the SUSY space to select possible underlying theory at the high scale and SUSY breaking mechanism (Eg. “LHC Olympics”, Nature May06, theorists try to guess what the theory is from pseudo-data) http://wwwth.cern.ch/lhcOlympics/lhcolympicsII.html

  12. Supersymmetry SUSY could be at the rendez-vous very early on! 10fb-1 Therefore: SUSY one of the priorities of the “search” program Main signal: lots of activity (jets, leptons, taus, missing ET) Needs however good understanding of the detector & SM processes!!

  13. q as as g q q q 02 Z 01 Supersymmetric particles Squarks and gluinos are produced via strong processes: !Large cross sections! Will be easy (in most cases) to detect: many jets and missing energy from the lightest stable SUSY particle (LPS) E.G. 900 GeV squarks Etmiss > 300 GeV + 4 jets LSP Etmiss = missing transverse energy

  14. But: Missing Transverse Energy Clean up cuts needed: cosmics, beam halo, dead channels, QCD

  15. Use the data to estimate backgrounds Low mass SUSY • Eg. an important background is • Z+ jets production where the • Z decays into neutrinos (missing ET!) • Trick: measure Z+jets with Z • Ignore the muons and calculate • missing ET spectrum • Allows to predict the Z ETmiss background

  16. A0=0, tanb=35, m>0 Reach versus integrated luminosity • If low energy Supersymmetry exists, LHC will almost certainly observe it • Squarks and Gluinos detectable up to 2.5-3 TeV mass with 300 fb-1 • Masses up to 1 TeV already detectable with 1 fb-1 Usually minimal Supergravity (mSUGRA) taken for studies 5 parameters m1/2: universal gaugino mass at GUT scale m0: universal scalar mass at GUT scale tan: vev ratio for 2 Higgs doublets sign(): sign of Higgs mixing parameter A0: trilinear coupling

  17. SUSY Signatures Important: different topologies/decay modes, i.e. on different signatures CMS PTDR Studies: Selection of 13 benchmark Points Low mass LM1LM9 High mass HM1HM4 * LM8 21h * LM9 21Z

  18. Inclusive SUSY searches Search strategy based on different signatures Low mass SUSY(mgluino~500 GeV) shows excess in many channels for O(100) pb-1 Time for discovery determined by:  Time to understand the detector performance, Etmiss tails, jet scale,lepton id  Time collect SM control samples such as W+jets, Z+jets, top..

  19. Reconstructing SUSY Sparticles LHC: complicated by decay chains for squarks and gluons Examples worked out for SPS1a (point B) in ATLAS/CMS LHC will see all squarks, H,A and may see most gauginos

  20. p b b p Sparticle Reconstruction Example Problem c10 measurement! It escapes detection like a neutrino! Use kinematic formulae... SUSY • Strategy: • Study many decay modes & fit “kinematic end points”

  21. m (j)min spectrum end-point : 552 GeV exp. precision ~1 % m () spectrum end-point : 109 GeV exp. precision ~0.3%  q 02  m (j)max spectrum threshold : 272 GeV exp. precision ~2 %  01 m (j) spectrum end-point : 479 GeV exp. precision ~1 % ATLAS 100 fb-1 Idea: study as many kinematic endpoints as possible. Relatively model indep. Needs sufficient statistics & many different/long decay chains

  22. Dilepton edges Mass reconstruction: examples LM2 dileptons (taus) More difficult but doable LM1 dileptons (e,) 1 fb-1 Stau mass precision to ~ 30 GeV (LM2/40 fb-1)

  23. p p Sparticle Detection & Reconstruction Mass precision for a favorable benchmark point at the LHC LCC1~ SPS1a~ point B’ m0=100 GeV m1/2= 250 GeV A0=-100 tan = 10 sign()=+ hep-ph/0508198 Lightest neutralino  Dark Matter? Fit SUSY model parameters to the measured SUSY particle masses to extract h2  O(10%) for LCC1 GeV

  24. SUSY decays to discover the Higgs Could be a discovery channel for the Higgs M(bb)

  25. Recent concerns: Special signatures In some models/phase space the gravitino is the LSP Then the NLSP (neutralino, Stau lepton) can live ‘long’ Eg. + gravitino or heavy stau slepton Signatures  Displaced vertices  Non-pointing showers  Long lived ‘heavy muons’ Challenge to the experiments!

  26. Long lived sparticles Some of these heavy long lived heavy sparticles will be stopped in the detector or walls around of the cavern. They will decay after some time: hours-days-weeks-months… • Some benchmark points with • Lifetime of 104-106 sec are • being studied: • M Nijori at al (to appear) • ADR, J. Ellis, et al. • Ideas: Use the cavern wall or addition of slepton stoppers in the cavern (multi-kton object) Object of a few 100 GeV

  27. Split Supersymmetry Arkani-Hamed et al., Giudice et al. • Landscape (string theory) inspired! • Assumes nature is fine tuned and SUSY is broken at some high scale • Motivated by cosmological constant problem and multitude of vacua in string theory • The only light particles are the Higgs and the gauginos (several 100 GeV to several TeV). Squarks ~ 1010 GeV • Interesting gluino phenomenology. - Gluino can live long: sec, min, years! - R-hadron formation: slow, heavy particles containing a heavy gluino – - special interactions with matter… GeV cos2=1 cos2=0 Higgs mass vs Log10(MS) Gluino lifetime Can we detect these gluinos at LHC??…

  28. How do these R-hadrons interact with matter? R-Hadrons (e.g. A Kraan hep-ph/0404001)  Gluino interactions suppressed as 1/M2  u,d quarks interact but with a kinetic energy of order 1 GeV  Hence energy loss reduced while passing through e.g the ATLAS calorimeter only about 10-15% is deposited. This will be a remarkable signature Also: charge flip while passing through matter

  29. Theories with Extra-dimensions > 800 theoretical papers over last 4 years …. Basic idea : solve hierarchy problem MEW/MPlanck ~ 10-17 by lowering gravity scale from MPlanck ~ 1019 GeV to MD ~ 1 TeV EW scale  gravity scale Possible if gravity propagates in 4 + n dimensions.

  30. Large Extra Dimensions Assume that gravity can propagate in extra dimensions of size R Newton’s law changes from F ~ 1/R2 1/Rn+2 Gravity gets stronger Effective Planck Scale: MSn+2~ Mpl2/(R)n Curled up…  MS could be of O(1) TeV Many different models…

  31. Large Extra Dimensions Large Extra dimensions (ADD) Gravity in bulk / flat space Missing energy/interference/black holes Warped Extra Dimensions (RS) Gravity in bulk / curved space Spin 2 resonances > TeV range k = warp factor TeV Scale Extra Dimensions Gauge bosons/Higgs in the bulk Spin 1 resonances > TeV range Interference with Drell-Yan Special case: Universal Extra Dimensions UED Everybody in the bulk! Fake SUSY spectrum of KK states + many combinations/variations

  32. ADD Extra Dimension signals at the LHC Graviton production! Graviton escapes detection Signal: single jet + large missing ET Test MD to 7-9 TeV for 100 fb-1

  33. Curved Space: RS Extra Dimensions phenomenology Study the channel ppGraviton e+e- signal+ Drell-Yan backgr. sensitivity

  34. New Gauge Bosons: same signature R. Cousins et al. Z’ production  Low lumi 0.1 fb-1 : discovery of 1-1.6 TeV possible, beyond Tevatron run-II  High lumi 100 fb-1: extend range to 3.4-4.3 TeV

  35. Can we distinguish? We observe a peak in di-lepton spectrum Is it a new gauge boson or a RS KK excitation?  Study the spin of the object: spin 1 versus spin 2

  36. Black Holes Black Holes are a direct prediction of Einstein’s general theory on relativity (though never quite accepted by Einstein) Schwarzschild Radius: within which nothing escapes gravitational force If the radius of an object is less than Rs a black hole is formed with G= 1/(MPlanck)2 Smallest scale: Planck Length (10-35 m) Need to squeeze 1019 GeV in such small area!! No chance to produce a black hole in the lab if gravity remains weak!! However: in Extra Dimension models the Planck scale is NOT at 1019 GeV 

  37. 4-dim., Mgravity= MPlanck : 4 + n-dim., Mgravity= MD ~ TeV : RS Black Holes production? • Schwarzschild radius (i.e. within which nothing escapes gravitational force): … only speculative for the time being … Since MD is low, tiny black holes of MBH ~ TeV can be produced if partons ij with sij = MBH pass at a distance smaller than RS • Large partonic cross-section : (ij  BH)~  RS2 • e.g. For MD ~3 TeV and n=4, (pp  BH)~ 100 fb  1000 events in 1 year at low L • Black holes decay immediately by Hawking radiation (democratic evaporation) : • -- large multiplicity • -- small missing E • -- jets/leptons ~ 5 expected signature (quite spectacular …)

  38. Black Hole production If the Planck scale in ~TeV region: can expect Black Hole production MD ~ 1 TeV n=6 Simulation of a black hole event with MBH ~ 8 TeV in ATLAS ~ Spherical events Many high energy jets leptons, photons etc. Hawking Radiation!! Ecological comment: BH’s will decay within 10-27 secs or so Detectors, electronics (and rest of the world) are safe!!

  39. Black Holes …and in CMS Revolutionary: Will allow to study Quantum Gravity in the laboratory!!

  40. Scientific American (May 05)

  41. Other New Physics ideas… • Plenty! • Models with strong dynamics, eg. Little Higgs models • Technicolor • Leptoquarks • Compositness • SUSY+ Extra dimensions • Heavy Majorana Neutrinos • WW,WZ resonances • … Have to keep our eyes open for all possibilities: Food for many PhD theses!!

  42. What can we expect in the first few years at the LHC?

  43. Re-discovery of the TOP Z’ into muons Susy - Susy Higgs ??? The First Physics Run (2008) Efficiency = 30% 1.9 fb-1

  44. What can we expect in 2010/ with 10 fb-1?

  45. Future Machines • Future Hadron Machines • SLHC/DLHC: LHC upgrades • VLHC • Future Lepton Machines • TeV e+e- LC Hot topic these days! • Multi-TeV e+e+ LC • Muon collider

  46. The LHC Upgrade Making the most of the LHC…

  47. Upgrades of the LHC J. Strait 2003: Not an “official” LHC plot hypotethical lumi scenario If startup is as optimistic as assumed here (1034 cm-2s-1 in 2011 already) After ~3 years the simple continuation becomes less exciting Time for an upgrade?

  48. The LHC upgrade: SLHC/DLHC Already time to think of upgrading the machine if wanted in ~10 years Two options presently discussed/studied • Higher luminosity ~1035cm-2 s-1 (SLHC) • Needs changes in machine and and particularly in the detectors •  Start change to SLHC mode some time 2013-2016 •  Collect ~3000 fb-1/experiment in 3-4 years data taking. • Higher energy? (DLHC) • LHC can reach s = 15 TeV with present magnets (9T field) • s of 28 (25) TeV needs ~17 (15) T magnets  R&D needed! • Even some ideas on increasing the energy by factor 3 (P. McIntyre)

  49. Channel mH S/B LHC S/B SLHC (600 fb-1) (6000 fb-1) H  Z   ~ 140 GeV ~ 3.5 ~ 11 H   130 GeV ~ 3.5 (gg+VBF) ~ 9.5 (gg) Rare Higgs Decays Modes BR ~ 10-4 for these channels! Cross section ~ few fb Channels studied:  H  Z    H   3000 fb-1 Additional coupling measurements : e.g. /W to ~ 20% Note: also a challenge at a ILC: e.g. gH ~ 16 % for 1 ab-1 at 800 GeV

  50. ~ v mH2 = 2  v2 Higgs Self Coupling Measurements Once the Higgs particle is found, try to reconstruct the Higgs potential Djouadi et al. Dawson et al. Too much backgr. /2 << 3/2 Difficult/impossible at the LHC

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