pptx - SLAC
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SLAC Particle Theory Overview circa 2007 Group Members Faculty & Staff: Stan Brodsky Michael Peskin Professor Professor Lance Dixon Tom Rizzo Professor Senior Staff JoAnne Hewett Eva Silverstein Professor Professor – ½ campus Stefan Höche Jay Wacker Associate Staff Assistant Professor Shamit Kachru Marvin Weinstein Professor – ½ campus Permanent Staff Particle Theory Program: at a Glance QCD Heavy Flavors Formal Theory Experimental Programs BSM Pheno Astro Interface Model Building QCD Highlights Brodsky, Dixon, Höche, Peskin • Leading effort in development of AdS/QCD framework • 1st computation of W/Z+3/4 jet production @ NLO • Prediction of left-handed W polarization at large pT – now observed by ATLAS/CMS • Development of BlackHat: general code for efficient NLO calculation of multi-jet processes – providing theoretical uncertainties on ATLAS/CMS data-driven estimations of SUSY MET+jets backgrounds • Sherpa event generator development and maintenance – only multi-purpose event generator maintained by US National Lab HEP theory staff member Direct connections of QCD research: SLAC program: ATLAS, BaBar, Super-B Broader program: CDF, D0, CMS, GSI, H1, Jlab, RHIC Heavy Flavor Highlights Brodsky, Hewett, Rizzo, Wacker • Development of algorithms for tagging top-quarks via boosted jets • Define and study top-quark forward-central charge asymmetry at LHC • Development of axigluon models that account for AtFB observed @ Tevatron • Study of relating Bs →μμ to Bs Mixing in models with new physics Direct connections of Heavy Flavor research: SLAC program: ATLAS, BaBar, LC, SuperB Broader program: CDF, D0, CMS, LHCb BSM Phenomenology Highlights Hewett, Peskin, Rizzo, Wacker • Generation of large pMSSM data sample – used by ATLAS/CMS • Development of Simplified Model approach to new physics searches - adopted by ATLAS/CMS • Leading effort on SUSY MET-based collider search techniques – collaboration with ATLAS/CMS • Novel Higgs signatures in 4GMSSM – new searches @CMS • Development of techniques to distinguish DM models at colliders Direct connections of BSM Pheno research: SLAC program: ATLAS, LC Broader program: CDF, D0, CMS BSM Model Building Highlights Hewett, Kachru, Peskin, Rizzo, Silverstein, Wacker • 1st construction of Supersymmetric Atoms • Development of dynamical SUSY Breaking models • Scattering states in AdS/CFT • Microscopic theory of gauge mediated SUSY breaking • Construction and study of composite DM models Direct connections of BSM Model Building research: SLAC program: ATLAS, BaBar, CDMS, Fermi, LC, SuperB Broader program: CDF, D0, CMS, LHCb, DM direct dectection Cosmology/Astro-Interface Highlights Hewett, Kachru, Peskin, Rizzo, Silverstein, Wacker • Comprehensive study of signatures of dark forces and construction and running of related experiment • DM searches in faint dwarf galaxies – in collaboration with Fermi • Construction of DM density profiles based on ΛCDM – in collaboration with KIPAC theory • Comprehensive study of pMSSM DM signatures • Development of natural and UV-complete large-field inflation, with signatures including gravitational waves • Complete analysis of redshifted slow roll brane inflation • Development of inflationary mechanisms and bottom-up systematics of non-Gaussianity – in collaboration with KIPAC theory Direct connections of Cosmo/Astro-interface research: SLAC program: BaBar, BICEP/SPUD, CDMS, Fermi, KIPAC theory, Super-B Broader program: CMB Pol, DM direct detection, Jlab, Kloe, PAMELA/HESS, Planck Formal Theory Highlights Dixon, Kachru, Silverstein, Weinstein • Studied uplifting of AdS/CFT to Cosmology and behind black hole horizons • Controlled QFTs with Lifshitz scaling symmetry: applications to phase transitions and transport • Showed N=4 super-Yang-Mills theory is solvable analog for QCD scattering • Demonstrated finiteness of N=8 supergravity through 4 loops Direct connections of Formal theory research: SLAC program: ATLAS, KIPAC theory, Phenomenological thrust, Photon Science Broader program: CDF, D0, CMS, Cosmology , Pheno The Large Hadron Collider: CERN, Geneva, Switzerland The LHC era has begun! The anticipation has fueled many ideas November 2007 CMS ATLAS pp e+e- + anything at the LHC Signals for a possible new Z’ Yellow = SM background as a function of the binned invariant mass of the two leptons showing statistical fluctuations Clearly the red case is very visible while the blue one is not..a small change in background might obscure it…so knowing the background very precisely would be very important in this case. gg H W+ W- e ± ± + neutrinos (=ME) at the Tevatron 10x Higgs contribution Lots of SM reactions can conspire to look like a Higgs boson which is only a tiny addition to the ordinary SM rate at the Tevatron. Unless the rates for all these processes are very well understood it will be impossible to claim that a Higgs boson has been found in this reaction… Thus it is generally extremely important to be able to make precise calculations of SM processes in order to find new physics which may be hiding in the background. This effort in the SLAC Theory group is headed by Lance Dixon, Stefan Hoeche Most calculations in the SM are performed using ‘Perturbation Theory’ which is an expansion of cross sections in a small parameter, e.g., the fine-structure constant in QED, using Feynman diagrams. These are pictorial representations of complex mathematical expressions which are determined by the interactions in a specific theory. - e+ QED 2 particles in and 2 particles out 22 e- + The complexity of these calculations depends upon the number of particles in the final state , e.g., 22 is easy involving at most a few graphs, while 2 8-10 may involve hundred or thousands of graphs & is VERY hard even at leading order(LO) The complexity ALSO depends on the order of the calculation, e.g. , 22 at NLO may involve hundreds of graphs depending on the identities of the particles! This is an enormous but important effort.. ‘loops’ occur at NLO This is the same process in QED but at NLO (with a single loop).. it is STILL 22 2n NNLO NLO LO LO This is an important background for Higgs searches as well as for Supersymmetry, one possible new physics scenario The Hierarchy Problem Energy (GeV) Planck Quantum Corrections: 1016 GUT Virtual Effects drag Weak Scale to MPl desert 1019 Future Collider Energies 103 Weak All of known physics 10-18 Solar System Gravity mH2 ~ ~ MPl2 A Cellar of New Ideas ’67 ’77 The Standard Model Vin de Technicolor ’70’s Supersymmetry: MSSM ’90’s SUSY Beyond MSSM ’90’s CP Violating Higgs ’98 Extra Dimensions ’02 Little Higgs ’03 ’03 ’04 ’05 Fat Higgs Higgsless Split Supersymmetry Twin Higgs a classic! aged to perfection better drink now mature, balanced, well developed - the Wino’s choice svinters blend all upfront, no finish lacks symmetry bold, peppery, spicy uncertain terrior complex structure young, still tannic needs to develop sleeper of the vintage what a surprise! finely-tuned double the taste J. Hewett 21 The Hierarchy Problem: Supersymmetry Energy (GeV) Planck Quantum Corrections: 1016 GUT Virtual Effects drag Weak Scale to MPl desert 1019 Future Collider Energies boson 103 Weak mH2 ~ ~ MPl2 fermion mH2 ~ All of known physics 10-18 Solar System Gravity ~ - MPl2 Large virtual effects cancel order by order in perturbation theory Two MSSM Model Frameworks • The constrained MSSM (CMSSM) – Based on mSUGRA – gravity mediated – Common masses & couplings at the GUT scale – m0, m1/2, A0, tanβ = v2/v1, sign • The phenomenological MSSM (pMSSM) – 19 real, weak-scale parameters scalars: mQ1, mQ3, mu1, md1, mu3, md3, mL1, mL3, me1, me3 gauginos: M1, M2, M3 tri-linear couplings: Ab, At, Aτ Higgs/Higgsino: μ, MA, tanβ What is the pMSSM ??? Berger, Conley, Cotta, Cowley, Gainer, Hewett, Ismail, Le, Rizzo • The most general, CP-conserving MSSM w/ R-parity conservation • Minimal Flavor Violation at the TeV scale • The first two sfermion generations are degenerate & have negligible Yukawa couplings • The lightest neutralino is the LSP & a thermal relic pMSSM LHC & LC Model Generation Fermi/Pamela Indirect Detection CDMS/XENON ICE3 Direct Detection ??? FLAT Solid=4j, dash=3j, dot=2j final states Red=20%, green=50%, blue=100% indicate background systematic errors Coverage in the all 3 channels depends quite sensitively on how well the backgrounds are understood How many models fail to have even one channel with S > some fixed value with L=10 fb-1 and B=20%? Benchmark Models? These models will be hard to find no matter what the lumi is… We are working with both ATLAS & CMS SUSY groups in studying these low-S models in detail FLAT Please come to the theory open house this afternoon! 2:00 Madrone Rm
