Presentation on theme: "Beyond the Standard Model LHC Startup Forum Coseners House, April 12th, 2007 John Ellis, TH Division, PH Department, CERN Commissioning update Status of."— Presentation transcript:
Beyond the Standard Model LHC Startup Forum Coseners House, April 12th, 2007 John Ellis, TH Division, PH Department, CERN Commissioning update Status of the Standard Model Search for the Higgs boson Look for supersymmetry/extra dimensions, … Find something the theorists did not expect
LHC Installation ~ Complete
LHC Cryogenic Operating Conditions SC 1.9 K, 1.3 bar Superfluid He II below point Low viscosity: permeates magnets High thermal conductivity, large specific heat: stability
Cooldown of Sector 78
Magnet Temperatures in Sector 78
Failure of heat exchanger at 9 bar Thin copper accordion weakened by brazing Engineering solution found Remove and replace in situ Inner-Triplet Saga: I
Failure of cold-mass support at 20 bar Broke apart + damage to feed box? Due to asymmetric force on quadrupole Damaged assembly must be replaced Others may be reinforced in situ Insert tie rods in cryostat Cock-up dixit UK ambassador Inner-Triplet Saga: II
Last magnet deliveredOctober 2006 Last magnet testedDecember 2006 Last magnet installedMarch 2007 Machine closedAugust 2007 First collisionsNovember 2007 ? Remaining LHC Milestones
Status of the Standard Model Perfect agreement with all confirmed accelerator data Consistency with precision electroweak data (LEP et al) only if there is a Higgs boson Agreement seems to require a relatively light Higgs boson weighing < ~ 150 GeV Raises many unanswered questions: mass? flavour? unification?
Indications on the Higgs Mass Sample observable: W LEP & Tevatron Combined information on Higgs mass March 2007 m W, m t both reduced by ~ ½ σ
The LHC Physics Haystack(s) Interesting cross sections Higgs Susy Cross sections for heavy particles ~ 1 /(1 TeV) 2 Most have small couplings ~ α 2 Compare with total cross section ~ 1/(100 MeV) 2 Fraction ~ 1/1,000,000,000,000 Need ~ 1,000 events for signal Compare needle ~ 1/100,000,000 m 3 Haystack ~ 100 m 3 Must look in ~ 100,000 haystacks
Event rates in ATLAS or CMS at L = cm -2 s -1 Huge Statistics thanks to High Energy and Luminosity LHC is a factory for anything: top, W/Z, Higgs, SUSY, etc…. mass reach for discovery of new particles up to m ~ 5 TeV Process Events/s Events per year Total statistics collected at previous machines by 2007 W e LEP / 10 7 Tevatron Z ee LEP Tevatron – Belle/BaBar ? H m=130 GeV ? m= 1 TeV Black holes m > 3 TeV (M D =3 TeV, n=4)
Start-up Physics Measure and understand minimum bias Measure jets, start energy calibration Measure W/Z, calibrate lepton energies Measure top, calibrate jet energies & missing E T First searches for Higgs: –Combine many signatures –need to understand detector very well First searches for SUSY, etc.
Looking for New LHC Need to understand SM first: –calibration, alignment, systematics Searches for specific scenarios, e.g., SUSY, vs signature-based searches, e.g., monojets? False dichotomy! How to discriminate between models? –different Z models? –missing energy: SUSY vs UED? higher excitations, spin correlations, spectra, …
ττ γγ ZZ* -> 4 leptons A la recherche du Higgs perdu … Some Sample Higgs Signals
Potential of Initial LHC running A Standard Model Higgs boson could be discovered with 5-σ significance with 5fb -1, 1fb -1 would be sufficient to exclude a Standard Model Higgs boson at the 95% confidence level Signal would include ττ, γγ, bb, WW and ZZ Will need to understand detectors very well
Will be possible to determine spin of Higgs decaying to γγ or ZZ Can measure invisible Higgs decays at 15-30% level Will be possible to determine many Higgs- particle couplings at the 10-20% level Subsequent LHC Running
The Big Open Questions The origin of particle masses? Higgs boson? + extra physics? solution at energy < 1 TeV (1000 GeV) Why so many types of particles? and the small matter-antimatter difference? Unification of the fundamental forces? at very high energy? explore indirectly via particle masses, couplings Quantum theory of gravity? string theory: extra dimension? LHC
What is Supersymmetry (Susy)? The last undiscovered symmetry? Could unify matter and force particles Links fermions and bosons Relates particles of different spins 0 - ½ /2 - 2 Higgs - Electron - Photon - Gravitino - Graviton Helps fix masses, unify fundamental forces
Loop Corrections to Higgs Mass 2 Consider generic fermion and boson loops: Each is quadratically divergent: Λ d 4 k/k 2 Leading divergence cancelled if Supersymmetry! 2 2
Other Reasons to like Susy It enables the gauge couplings to unify It predicts m H < 150 GeV JE, Nanopoulos, Olive + Santoso: hep-ph/ As suggested by EW data Erler: 2007
Astronomers say that most of the matter in the Universe is invisible Dark Matter Supersymmetric particles ? We shall look for them with the LHC
Lightest Supersymmetric Particle Stable in many models because of conservation of R parity: R = (-1) 2S –L + 3B where S = spin, L = lepton #, B = baryon # Particles have R = +1, sparticles R = -1: Sparticles produced in pairs Heavier sparticles lighter sparticles Lightest supersymmetric particle (LSP) stable Fayet
Possible Nature of LSP No strong or electromagnetic interactions Otherwise would bind to matter Detectable as anomalous heavy nucleus Possible weakly-interacting scandidates Sneutrino (Excluded by LEP, direct searches) Lightest neutralino χ Gravitino (nightmare for astrophysical detection)
Constraints on Supersymmetry Absence of sparticles at LEP, Tevatron selectron, chargino > 100 GeV squarks, gluino > 250 GeV Indirect constraints Higgs > 114 GeV, b s γ Density of dark matter lightest sparticle χ: WMAP: < Ω χ h 2 < σ effect in g μ – 2?
Current Constraints on CMSSM WMAP constraint on relic density Excluded because stau LSP Excluded by b s gamma Excluded (?) by latest g - 2 Assuming the lightest sparticle is a neutralino JE + Olive + Santoso + Spanos
Classic Supersymmetric Signature Missing transverse energy carried away by dark matter particles
Search for Supersymmetry Light low luminosity Heavy sparticles
Initial LHC Reach for Supersymmetry How soon will we know?
Implications of LHC Search for ILC In CMSSM LHC already sees beyond ILC at turn-on LHC gluino mass reach Corresponding sparticle ILC Blaising et al: 2006
Precision Observables in Susy mWmW sin 2 θ W Present & possible future errors Sensitivity to m 1/2 in CMSSM along WMAP lines for different A Can one estimate the scale of supersymmetry? tan β = 50 tan β = 10 JE + Heinemeyer + Olive + Weber + Weiglein: 2007
More Observables b sγ tan β = 10tan β = 50 g μ - 2 JE + Heinemeyer + Olive + Weber + Weiglein: 2007
Likelihood for m 1/2 Global Fit to all Observables tan β = 10tan β = 50 JE + Heinemeyer + Olive + Weber + Weiglein: 2007 Likelihood for M h
Search for Squark W Hadron Decays Use k T algorithm to define jets Cut on W mass W and QCD jets have different subjet splitting scales Corresponding to y cut Butterworth + JE + Raklev: 2007
Background- subtracted qW mass combinations in benchmark scenarios Constrain sparticle mass spectra Search for Hadronic W, Z Decays Butterworth + JE + Raklev: 2007
Possible Nature of SUSY Dark Matter No strong or electromagnetic interactions Otherwise would bind to matter Detectable as anomalous heavy nucleus Possible weakly-interacting scandidates Sneutrino (Excluded by LEP, direct searches) Lightest neutralino χ Gravitino (nightmare for astrophysical detection) GDM: a bonanza for the LHC!
Possible Nature of NLSP if GDM NLSP = next-to-lightest sparticle Very long lifetime due to gravitational decay, e.g.: Could be hours, days, weeks, months or years! Generic possibilities: lightest neutralino χ lightest slepton, probably lighter stau Constrained by astrophysics/cosmology
Triggering on GDM Events Will be selected by many separate triggers via combinations of μ, E energy, jets, τ JE, Raklev, Øye: 2007
Efficiency for Detecting Metastable Staus Good efficiency for reconstructing stau tracks JE + Raklev + Oye
ATLAS Momentum resolution Good momentum resolution JE + Raklev + Oye
Stau Momentum Spectra βγ typically peaked ~ 2 Staus with βγ < 1 leave central tracker after next beam crossing Staus with βγ < ¼ trapped inside calorimeter Staus with βγ < ½ stopped within 10m Can they be dug out of cavern wall? De Roeck, JE, Gianotti, Moortgat, Olive + Pape: hep-ph/
Extract Cores from Surrounding Rock? Use muon system to locate impact point on cavern wall with uncertainty < 1cm Fix impact angle with accuracy Bore into cavern wall and remove core of size 1cm × 1cm × 10m = m 3 ~ 100 times/year Can this be done before staus decay? Caveat radioactivity induced by collisions! 2-day technical stop ~ 1/month Not possible if lifetime ~10 4 s, possible if ~10 6 s? Very little room for water tank in LHC caverns, only in forward directions where few staus De Roeck, JE, Gianotti, Moortgat, Olive + Pape: hep-ph/
String Theory Candidate for reconciling gravity with quantum mechanics Point-like particles extended objects Simplest possibility: lengths of string Quantum consistency fixes # dimensions: Bosonic string: 26, superstring: 10 Must compactify extra dimensions, scale ~ 1/m P ? Or larger?
How large could extra Dimensions be? 1/TeV? could break supersymmetry, electroweak micron? can rewrite hierarchy problem Infinite? warped compactifications Look for black holes, Kaluza-Klein colliders?
Spin Effects in Decay Chains Chain DCBA: Scalar/Fermion/Vector Shape of dilepton spectrum Shape of q-lepton spectrum Angular asymmetry in q-lepton spectrum Distinguish supersymmetry from extra-D scenarios Athanasiou+Lester+Smillie+Webber
And if gravity becomes strong at the TeV scale … Black Hole Production at LHC? Multiple jets, leptons from Hawking radiation
Black Hole LHC Cambridge: al et Webber
Black Hole Decay Spectrum Cambridge: al et Webber
Summary The origin of mass is the most pressing in particle physics Needs a solution at energy < 1 TeV Higgs? Supersymmetry? LHC will tell! Lots of speculative ideas for other physics beyond the Standard Model Grand unification, strings, extra dimensions? … LHC may also probe these speculations We do not know what the LHC will find: its discoveries will set agenda for future projects