SLAC Particle Theory Overview circa 2007
Faculty & Staff: Group Members Stan Brodsky Professor Lance Dixon Professor JoAnne Hewett Professor Stefan Höche Associate Staff Shamit Kachru Professor ½ campus Michael Peskin Professor Tom Rizzo Senior Staff Eva Silverstein Professor ½ campus Jay Wacker Assistant Professor Marvin Weinstein Permanent Staff
Particle Theory Program: at a Glance QCD Heavy Flavors Formal Theory Experimental Programs BSM Pheno Astro Interface Model Building
QCD Highlights Leading effort in development of AdS/QCD framework 1 st computation of W/Z+3/4 jet production @ NLO Prediction of left-handed W polarization at large p T 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 Brodsky, Dixon, Höche, Peskin 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 A t FB observed @ Tevatron Study of relating B s μμ to B s 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 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 Hewett, Peskin, Rizzo, Wacker
BSM Model Building Highlights Hewett, Kachru, Peskin, Rizzo, Silverstein, Wacker 1 st 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 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 Hewett, Kachru, Peskin, Rizzo, Silverstein, Wacker
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 2 2 e - +
The complexity of these calculations depends upon the number of particles in the final state, e.g., 2 2 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., 2 2 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 2 2
2 n NNLO NLO LO LO
This is an important background for Higgs searches as well as for Supersymmetry, one possible new physics scenario
desert The Hierarchy Problem Energy (GeV) 10 19 10 16 Planck GUT Quantum Corrections: Virtual Effects drag Weak Scale to M Pl Future Collider Energies 10 3 Weak m H 2 ~ ~ M Pl 2 All of known physics 10-18 Solar System Gravity
A Cellar of New Ideas 67 The Standard Model 77 Vin de Technicolor a classic! aged to perfection better drink now 70 s 90 s 90 s Supersymmetry: MSSM SUSY Beyond MSSM CP Violating Higgs mature, balanced, well developed - the Wino s choice svinters blend all upfront, no finish lacks symmetry 98 Extra Dimensions 02 Little Higgs 03 Fat Higgs 03 Higgsless 04 Split Supersymmetry 05 Twin Higgs 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
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desert The Hierarchy Problem: Supersymmetry Energy (GeV) 10 19 10 16 Planck GUT Quantum Corrections: Virtual Effects drag Weak Scale to M Pl boson Future Collider Energies 10 3 Weak m H 2 ~ ~ M Pl 2 fermion All of known physics 10-18 Solar System Gravity m H 2 ~ ~ - M Pl 2 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 m 0, m 1/2, A 0, tanβ = v 2 /v 1, sign The phenomenological MSSM (pmssm) 19 real, weak-scale parameters scalars: m Q1, m Q3, m u1, m d1, m u3, m d3, m L1, m L3, m e1, m e3 gauginos: M 1, M 2, M 3 tri-linear couplings: A b, A t, A τ Higgs/Higgsino: μ, M A, 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 ICE 3 CDMS/XENON 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