* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Anticipating New Physics at the LHC
Symmetry in quantum mechanics wikipedia , lookup
Introduction to quantum mechanics wikipedia , lookup
Old quantum theory wikipedia , lookup
Gauge fixing wikipedia , lookup
Quantum gravity wikipedia , lookup
Canonical quantum gravity wikipedia , lookup
Peter Kalmus wikipedia , lookup
Nuclear structure wikipedia , lookup
Renormalization wikipedia , lookup
Quantum chromodynamics wikipedia , lookup
Event symmetry wikipedia , lookup
History of quantum field theory wikipedia , lookup
An Exceptionally Simple Theory of Everything wikipedia , lookup
Theory of everything wikipedia , lookup
ALICE experiment wikipedia , lookup
Introduction to gauge theory wikipedia , lookup
Scalar field theory wikipedia , lookup
Renormalization group wikipedia , lookup
Weakly-interacting massive particles wikipedia , lookup
Compact Muon Solenoid wikipedia , lookup
Elementary particle wikipedia , lookup
Higgs boson wikipedia , lookup
ATLAS experiment wikipedia , lookup
Mathematical formulation of the Standard Model wikipedia , lookup
Supersymmetry wikipedia , lookup
Grand Unified Theory wikipedia , lookup
Technicolor (physics) wikipedia , lookup
Search for the Higgs boson wikipedia , lookup
Large Hadron Collider wikipedia , lookup
Higgs mechanism wikipedia , lookup
Standard Model wikipedia , lookup
Anticipating New Physics @ the LHC • Why the Terascale? • Scenarios for Electroweak Symmetry Breaking and the Gauge Hierarchy – LHC Signatures – Connection to Dark Matter • Summary: Discoveries are only months away! APS April Meeting, 2007 J. Hewett, Stanford Linear Accelerator Center Why the Terascale? • Electroweak Symmetry breaks at energies ~ 1 TeV (Higgs or ???) • Gauge Hierarchy: Nature is fine-tuned or Higgs mass must be stabilized by New Physics ~ 1 TeV • Dark Matter: Weakly Interacting Massive Particle must have mass ~ 1 TeV to reproduce observed DM density The LHC is turning on! The anticipation has fueled many ideas! A Cellar of New Ideas ’67 The Standard Model ’77 Vin de Technicolor ’70’s Supersymmetry: MSSM ’90’s-now SUSY Beyond MSSM a classic! aged to perfection better drink now mature, balanced, well developed - the Wino’s choice svinters blend CP Violating Higgs all upfront, no finish lacks symmetry ’98 Extra Dimensions bold, peppery, spicy uncertain terrior ’02 Little Higgs ’90’s ’03 ’03 ’04 ’05 Fat Higgs Higgsless Split Supersymmetry Twin Higgs complex structure young, still tannic needs to develop sleeper of the vintage what a surprise! finely-tuned double the taste J. Hewett Discoveries at the LHC will find the vintage nature has bottled. The Standard Model of Particle Physics Building Blocks of Matter: Symmetry: SU(3)C x SU(2)L x U(1)Y QCD Electroweak Spontaneously Broken to QED This structure is experimentally confirmed! The Standard Model Higgs Boson Economy: 1 scalar doublet Higgs Potential: V() = 22/2 + 4/4 Spontaneous Symmetry Breaking Chooses a vacuum v = 0||0 and shifts the field = - v V() = m22/2 + v3 + 4/4 gives 1 physical Higgs scalar with m = 2 v Masses of electroweak gauge bosons proportional to v We need to discover the Higgs and experimentally test this potential and the Higgs properties! Higgs Mass Upper Bound: Gauge Boson Scattering Higgs Higgs Bad violation of unitarity ~ E2 Restores unitarity Expand cross section into partial waves Unitarity bound (Optical theorem!) |Re a0| < ½ Gives mH < 1 TeV LHC is designed to explore this entire region! Present Limits: Direct Searches at LEP: mH > 114.4 GeV Indirect Searches at LEP/SLC: mH < 150-200 GeV @ 95% CL Higgs Z Z Z Higgs @ the LHC: Production mechanisms & rates Signal determined by final state versus background Higgs Search Strategies Low: MH < 140 GeV Medium: 130<MH<500 GeV High: MH > ~500 GeV The Hierarchy Problem Energy (GeV) Planck GUT 10 Weak Quantum Corrections: Virtual Effects drag Weak Scale to MPl desert 1019 1016 Future Collider Energies 3 mH2 ~ All of known physics 10-18 Solar System Gravity ~ MPl2 The Hierarchy Problem: Supersymmetry Energy (GeV) Planck GUT Quantum Corrections: Virtual Effects drag Weak Scale to MPl desert 1019 1016 Future Collider Energies boson 10 3 Weak fermion mH2 ~ All of known physics 10-18 ~ MPl2 mH2 ~ Solar System Gravity ~ - MPl2 Large virtual effects cancel order by order in perturbation theory Supersymmetry: •Symmetry between fermions and bosons •Predicts that every particle has a superpartner of equal mass ( SUSY is broken: many competing models!) •Suppresses quantum effects •Can make quantum mechanics consistent with gravity (with other ingredients) Supersymmetry at the LHC SUSY discovery generally ‘easy’ at LHC Cut: ETmiss > 300 GeV LHC Supersymmetry Discovery Reach Model where gravity mediates SUSY breaking – 5 free parameters at high energies Squark and Gluino mass reach is 2.5-3.0 TeV @ 300 fb-1 MSSM only viable for mh < 135 GeV Carena, Haber hep-ph/0208209 MSSM: tension with fine-tuning Competing factors: – Mass of lightest higgs mh < MZ at tree-level large quantum corrections from top sector < (130 GeV)2 If stop mass ~ 1 TeV – Stability of Higgs mass stops cut-off top contribution to quadratic divergence stops can’t be too heavy – Z mass relationship Resolve Fine-Tuning: Extend the MSSM • NMSSM (Next-to Minimal SSM) Dermisek, Gunion, … – Add a Higgs Singlet - Evade LEP bounds – minimize fine-tuning! - Regions where Higgs discovery is difficult @ LHC • MNMSSM (Minimally Non-minimal MSSM) – Lightest higgs < 145 GeV – Observable @ LHC • Gauge Extensions of MSSM – Mh < 250 (350) GeV • Split Supersymmetry Panagiotakopoulos, Pilaftis Batra, Delgado, Kaplan, Tait Dark Matter in Supersymmetry •A component of Dark Matter could be the Lightest Neutralino of Supersymmetry - stable and neutral with mass ~ 0.1 – 1 TeV •In this case, electroweak strength annihilation gives relic density of ΩCDM h2 ~ m2 (1 TeV)2 Fraction of total Dark Matter density Mass of Dark Matter Particle from Supersymmetry (TeV) Determination of Dark Matter Density @ LHC • Measure SUSY properties @ LHC • Benchmark point SPS1a • Dependence on Stau mass determination Baltz, Battaglia, Peskin, Wizansky hep-ph/0602187 The Hierarchy Problem: Extra Dimensions Energy (GeV) Planck GUT Simplest Model: Large Extra Dimensions desert 1019 1016 Future Collider Energies 10 3 Weak – Quantum Gravity = Fundamental scale in 4 + dimensions MPl2 = (Volume) MD2+ All of known physics Gravity propagates in D = 3+1 + dimensions 10-18 Solar System Gravity Arkani-Hamed, Dimopoulis, Dvali Kaluza-Klein Modes in a Detector Indirect Signature Missing Energy Signature pp g + Gn Events / 50 GeV / 100 fb-1 LHC 102 10 1 10-1 10-2 JLH Mee [GeV] Vacavant, Hinchliffe Graviton Exchange Modified with Running Gravitational Coupling t= SM 1 0.5 Insert Form Factor in coupling to parameterize running M*D-2 [1+q2/t2M*2 ]-1 Could reduce signal! D=3+4 M* = 4 TeV JLH, Rizzo, to appear Black Hole Production @ LHC: Dimopoulos, Landsberg Giddings, Thomas Black Holes produced when s > M* Classical Approximation: E/2 b [space curvature << E] b < Rs(E) BH forms E/2 Geometric Considerations: Naïve = Rs2(E), details show this holds up to a factor of a few Production rate is enormous! Determination of Number of Large Extra Dimensions 1 per sec at LHC! JLH, Lillie, Rizzo hep-ph/0503178 Black Hole event simulation @ LHC The Hierarchy Problem: Extra Dimensions Energy (GeV) Planck GUT desert 1019 1016 Future Collider Energies Model II: Warped Extra Dimensions strong curvature 10 3 Weak wk = MPl e-kr All of known physics 10-18 Solar System Gravity Randall, Sundrum Kaluza-Klein Modes in a Detector: SM on the brane Number of Events in Drell-Yan For this same model embedded in a string theory: AdS5 x S Davoudiasl, JLH, Rizzo Kaluza-Klein Modes in a Detector: SM off the brane Fermion wavefunctions in the bulk: decreased couplings to light fermions for gauge & graviton KK states gg gn tt gg Gn ZZ Lillie, Randall, Wang, hep-ph/0701164 Agashe, Davoudiasl, Perez, Soni hep-ph/0701186 Issue: Top Collimation g1 = 2 TeV gg gn tt g1 = 4 TeV Lillie, Randall, Wang, hep-ph/0701164 The Hierarchy Problem: Little Higgs Energy (GeV) Planck GUT Little Hierarchies! desert 1019 1016 Future Collider Energies 104 New Physics! 10 Weak 3 Simplest Model: The Littlest Higgs with ~ 10 TeV No UV completion All of known physics 10-18 Solar System Gravity Arkani-Hamed, Cohen, Katz, Nelson The Hierarchy Problem: Little Higgs Energy (GeV) 1019 1016 . . . Future Collider Energies Planck GUT 106 105 104 New Physics! New Physics! New Physics! 10 Weak 3 All of known physics 10-18 Solar System Gravity Stacks of Little Hierarchies Simplest Model: The Littlest Higgs with 1 ~ 10 TeV 2 ~ 100 TeV 3 ~ 1000 TeV ….. Little Higgs: The Basics • The Higgs becomes a component of a larger multiplet of scalars, • transforms non-linearly under a new global symmetry • New global symmetry undergoes SSB leaves Higgs as goldstone • Part of global symmetry is gauged Higgs is pseudo-goldstone • Careful gauging removes Higgs 1-loop divergences mh2 ~ 2 (162)2 , > 10 TeV, @ 2-loops! 3-Scale Model > 10 TeV: New Strong Dynamics Global Symmetry f ~ /4 ~ TeV: v ~ f/4 ~ 100 GeV: Sample Spectrum Symmetires Broken Pseudo-Goldstone Scalars New Gauge Fields New Fermions Light Higgs SM vector bosons & fermions Little Higgs Gauge Production WZ WH WZ 2j + 3l + Azuelos etal, hep-ph/0402037 Birkedal, Matchev, Perelstein, hep-ph/0412278 The Hierarchy Problem: Higgsless Energy (GeV) Planck GUT desert 1019 1016 Future Collider Energies Warped Extra Dimensions strong curvature 10 3 Weak wk = MPl e-kr With NO Higgs boson! All of known physics 10-18 Solar System Gravity Csaki, Grojean,Murayama, Pilo, Terning Framework: EW Symmetry Broken by Boundary Conditions SU(2)L x SU(2)R x U(1)B-L in 5-d Warped bulk Planck brane TeV-brane SU(2)L x SU(2)R SU(2)R x U(1)B-L U(1)Y WR, ZR get Planck scale masses SU(2)D BC’s restricted by variation of the action at boundary SU(2) Custodial Symmetry is preserved! W, Z get TeV scale masses left massless! Unitarity in Gauge Boson Scattering: What do we do without a Higgs? Exchange gauge KK towers: Conditions on KK masses & couplings: Csaki etal, hep-ph/0305237 (g1111)2 = k (g11k)2 4(g1111)2 M12 = k (g11k)2 Mk2 Necessary, but not sufficient, to guarantee perturbative unitarity! Production of Gauge KK States @ LHC gg, qq g1 dijets Davoudiasl, JLH, Lilllie, Rizzo Balyaev, Christensen The Hierarchy Problem: Who Cares!! Planck Scale Gauge Hierarchy Problem Weak Scale Cosmological Constant Problem Cosmological Scale We have much bigger Problems! Split Supersymmetry: Energy (GeV) Arkani-Hamed, Dimopoulis hep-ph/0405159 Giudice, Romanino hep-ph/0406088 MGUT ~ 1016 GeV MS : SUSY broken at high scale ~ 109-13 GeV Scalars receive mass @ high scale Mweak 1 light Higgs + Fermions protected by chiral symmetry Collider Phenomenology: Gluinos • • • • Pair produced via strong interactions as usual Gluinos are long-lived No MET signature Form R-hadrons q Gluino pair + jet cross section 1 0 ~ ~ g q q 100 fb-1 Rate ~ 0, due to heavy squark masses! JLH, Lillie, Masip, Rizzo hep-ph/0408248 Density of Stopped Gluinos in ATLAS Arvanitaki, etal hep-ph/0506242 See also ATLAS study, Kraan etal hep-ph/0511014 This is a Special Time in Particle Physics • Urgent Questions Provocative discoveries lead to urgent questions • Connections Questions seem to be related in fundamental, yet mysterious, ways • Tools We have the experimental tools, technologies, and strategies to tackle these questions We are witnessing a Scientific Revolution in the Making! The LHC is Turning On!!!!!!!! And we are ready! Higgs Coupling Determinations @ LHC Duhrssen, Heinemeyer, Logan, Rainwater, Weiglein, Zeppenfeld Observed Channels: – – – – gg H ZZ, WW, qqH qqZZ, qqWW, qq, qq WH WWW, W; ZH Z ttH, with H WW, , bb Theoretical Assumption: Employ Narrow Width Approx: (H) B(Hxx) = (H)SM p x V VSM , V=W,Z pSM tot