Presentation on theme: "Beyond the Standard Model"— Presentation transcript:
1Beyond the Standard Model Commissioning updateStatus of the Standard ModelSearch for ‘the’ Higgs bosonLook for supersymmetry/extra dimensions, …Find something the theorists did not expectLHC Startup ForumCosener’s House, April 12th, 2007John Ellis, TH Division, PH Department, CERN
6Inner-Triplet Saga: I Failure of heat exchanger at 9 bar Thin copper ‘accordion’ weakened by brazingEngineering solution foundRemove and replace in situ
7Inner-Triplet Saga: II Failure of cold-mass support at 20 barBroke apart + damage to feed box?Due to asymmetric force on quadrupoleDamaged assembly must be replacedOthers may be reinforced in situInsert tie rods in cryostat‘Cock-up’dixit UKambassador
9Status of the Standard Model Perfect agreement with all confirmed accelerator dataConsistency with precision electroweak data (LEP et al) only if there is a Higgs bosonAgreement seems to require a relatively light Higgs boson weighing < ~ 150 GeVRaises many unanswered questions:mass? flavour? unification?
10Indications on the Higgs Mass March 2007Indications on the Higgs MassSample observable:W LEP & TevatronCombined informationon Higgs massmW, mt both reduced by ~ ½ σ
11The LHC Physics Haystack(s) Interesting cross sectionsCross sections for heavy particles~ 1 /(1 TeV)2Most have small couplings ~ α2Compare with total cross section~ 1/(100 MeV)2Fraction ~ 1/1,000,000,000,000Need ~ 1,000 events for signalCompare needle~ 1/100,000,000 m3Haystack ~ 100 m3Must look in ~ 100,000 haystacksSusyHiggs
12Huge Statistics thanks to High Energy and Luminosity Event rates in ATLAS or CMS at L = 1033 cm-2 s-1Process Events/s Events per year Total statistics collectedat previous machines by 2007W e LEP / 107 TevatronZ ee LEPTevatron– Belle/BaBar ?H m=130 GeV ?m= 1 TeVBlack holesm > 3 TeV(MD=3 TeV, n=4)LHC is a factory for anything: top, W/Z, Higgs, SUSY, etc….mass reach for discovery of new particles up to m ~ 5 TeV
13Start-up Physics Measure and understand minimum bias Measure jets, start energy calibrationMeasure W/Z, calibrate lepton energiesMeasure top, calibrate jet energies & missing ETFirst searches for Higgs:Combine many signaturesneed to understand detector very wellFirst searches for SUSY, etc.
14Looking for New Physics @ LHC Need to understand SM first:calibration, alignment, systematicsSearches 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, …
15Some Sample Higgs Signals A la recherche duHiggs perdu …Some Sample Higgs SignalsγγγγZZ* -> 4 leptonsττ
16Potential 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 levelSignal would include ττ, γγ, bb, WW and ZZWill need to understand detectors very well
17Subsequent LHC Running Will be possible to determine spin of Higgs decaying to γγ or ZZCan measure invisible Higgs decays at 15-30% levelWill be possible to determine many Higgs-particle couplings at the 10-20% level
18The Big Open Questions LHC LHC LHC LHC 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, couplingsQuantum theory of gravity?string theory: extra dimension?LHCLHCLHCLHC
19What is Supersymmetry (Susy)? The last undiscovered symmetry?Could unify matter and force particlesLinks fermions and bosonsRelates particles of different spins½ /Higgs - Electron - Photon - Gravitino - GravitonHelps fix masses, unify fundamental forces
20Loop Corrections to Higgs Mass2 Consider generic fermion and boson loops:Each is quadratically divergent: ∫Λd4k/k2Leading divergence cancelled ifSupersymmetry!2∙2
21Other Reasons to like Susy It enables the gauge couplings to unifyIt predicts mH < 150 GeVAs suggestedby EW dataErler: 2007JE, Nanopoulos, Olive + Santoso: hep-ph/
22Astronomers saythat most of thematter in theUniverse isinvisibleDark Matter‘Supersymmetric’ particles ?We shall look forthem with theLHC
23Lightest Supersymmetric Particle Stable in many models because of conservation of R parity:R = (-1) 2S –L + 3Bwhere S = spin, L = lepton #, B = baryon #Particles have R = +1, sparticles R = -1:Sparticles produced in pairsHeavier sparticles lighter sparticlesLightest supersymmetric particle (LSP) stableFayet
24Possible Nature of LSP No strong or electromagnetic interactions Otherwise would bind to matterDetectable as anomalous heavy nucleusPossible weakly-interacting scandidatesSneutrino(Excluded by LEP, direct searches)Lightest neutralino χGravitino(nightmare for astrophysical detection)
25Constraints on Supersymmetry Absence of sparticles at LEP, Tevatronselectron, chargino > 100 GeVsquarks, gluino > 250 GeVIndirect constraintsHiggs > 114 GeV, b → s γDensity of dark matterlightest sparticle χ:WMAP: < Ωχh2 < 0.1243.3 σeffect ingμ – 2?
26Current Constraints on CMSSM Assuming thelightest sparticleis a neutralinoExcluded because stau LSPExcluded by b s gammaWMAP constraint on relic densityExcluded (?) by latest g - 2JE + Olive + Santoso + Spanos
27Classic Supersymmetric Signature Missing transverse energycarried away by dark matter particles
28Search for Supersymmetry Light sparticles@ low luminosityHeavy sparticles
29Initial LHC Reach for Supersymmetry How soon will we know?Initial LHC Reach for Supersymmetry
30Implications of LHC Search for ILC In CMSSMLHC gluinomass reachCorresponding sparticleILCLHC already seesbeyond ILC ‘at turn-on’103210331 10331 1034Blaising et al: 2006
31Precision Observables in Susy Can one estimate the scale of supersymmetry?Precision Observables in SusySensitivity to m1/2in CMSSMalong WMAP linesfor different AmWtan β = 10tan β = 50sin2θWPresent & possiblefuture errorsJE + Heinemeyer + Olive + Weber + Weiglein: 2007
32More Observables b → sγ gμ - 2 tan β = 10 tan β = 50 JE + Heinemeyer + Olive + Weber + Weiglein: 2007
33Global Fit to all Observables tan β = 10tan β = 50Likelihoodfor m1/2Likelihoodfor MhJE + Heinemeyer + Olive + Weber + Weiglein: 2007
35Search for Squark W Hadron Decays Use kT algorithm to define jetsCut on W massW and QCD jets have different subjet splitting scalesCorresponding to y cutButterworth + JE + Raklev: 2007
36Search for Hadronic W, Z Decays Background-subtracted qW mass combinations in benchmark scenariosConstrain sparticle mass spectraButterworth + JE + Raklev: 2007
37Possible Nature of SUSY Dark Matter No strong or electromagnetic interactionsOtherwise would bind to matterDetectable as anomalous heavy nucleusPossible weakly-interacting scandidatesSneutrino(Excluded by LEP, direct searches)Lightest neutralino χGravitino(nightmare for astrophysical detection)GDM: a bonanza for the LHC!
38Possible Nature of NLSP if GDM NLSP = next-to-lightest sparticleVery long lifetime due to gravitational decay, e.g.:Could be hours, days, weeks, months or years!Generic possibilities:lightest neutralino χlightest slepton, probably lighter stauConstrained by astrophysics/cosmology
39Triggering on GDM Events Will be selected by many separate triggersvia combinations of μ, E energy, jets, τJE, Raklev, Øye: 2007
40Efficiency for Detecting Metastable Staus Good efficiency for reconstructing stau tracksJE + Raklev + Oye
41ATLAS Momentum resolution Good momentum resolutionJE + Raklev + Oye
43Stau Momentum Spectra βγ typically peaked ~ 2 Staus with βγ < 1 leave central trackerafter next beam crossingStaus with βγ < ¼ trapped inside calorimeterStaus with βγ < ½ stopped within 10mCan they be dug out of cavern wall?De Roeck, JE, Gianotti, Moortgat, Olive + Pape: hep-ph/
44Extract Cores from Surrounding Rock? Very little room for water tank in LHC caverns,only in forward directions where few stausExtract Cores from Surrounding Rock?Use muon system to locate impact point on cavern wall with uncertainty < 1cmFix impact angle with accuracy 10-3Bore into cavern wall and remove core of size 1cm × 1cm × 10m = 10-3m3 ~ 100 times/yearCan this be done before staus decay?Caveat radioactivity induced by collisions!2-day technical stop ~ 1/monthNot possible if lifetime ~104s, possible if ~106s?De Roeck, JE, Gianotti, Moortgat, Olive + Pape: hep-ph/
45String Theory Candidate for reconciling gravity with quantum mechanics Point-like particles → extended objectsSimplest possibility: lengths of stringQuantum consistency fixes # dimensions:Bosonic string: 26, superstring: 10Must compactify extra dimensions, scale ~ 1/mP?Or larger?
46How large could extra Dimensions be? 1/TeV?could break supersymmetry, electroweakmicron?can rewrite hierarchy problemInfinite?warped compactificationsLook for black holes, Kaluza-Klein colliders?
47Spin Effects in Decay Chains Shape of dilepton spectrumChain DCBA:Scalar/Fermion/VectorDistinguish supersymmetryfrom extra-D scenariosAngular asymmetryin q-lepton spectrumShape of q-lepton spectrumAthanasiou+Lester+Smillie+Webber
48Black Hole Production at LHC? And if gravity becomes strong at the TeV scale …Black Hole Production at LHC?Multiple jets,leptons fromHawkingradiation
49Black Hole Production @ LHC Cambridge: al et Webber
50Black Hole Decay Spectrum Cambridge: al et Webber
51Summary We do not know what the LHC will find: The origin of mass is the most pressing in particle physicsNeeds a solution at energy < 1 TeVHiggs? Supersymmetry?LHC will tell!Lots of speculative ideas for other physics beyond the Standard ModelGrand unification, strings, extra dimensions? …LHC may also probe these speculationsWe do not know what the LHC will find:its discoveries will set agenda for future projects