Download - SLAC Particle Theory Overview
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SLAC Particle Theory Overview
circa 2007
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Group Members Faculty & Staff: Stan Brodsky Michael
Peskin
Lance Dixon Tom Rizzo
JoAnne Hewett Eva Silverstein
Stefan Höche Jay Wacker
Shamit Kachru Marvin Weinstein
Professor Professor
Professor
Professor Professor – ½ campus
Senior Staff
Associate Staff
Professor – ½ campus
Assistant Professor
Permanent Staff
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Particle Theory Program: at a Glance
QCD
Heavy Flavors
BSM Pheno
Model Building
Astro Interface
Formal Theory
Experimental Programs
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QCD Highlights• 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-BBroader program: CDF, D0, CMS, GSI, H1, Jlab, RHIC
Brodsky, Dixon, Höche, Peskin
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Heavy Flavor Highlights
• 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 At
FB 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, SuperBBroader program: CDF, D0, CMS, LHCb
Brodsky, Hewett, Rizzo, Wacker
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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, LCBroader program: CDF, D0, CMS
Hewett, Peskin, Rizzo, Wacker
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BSM Model Building Highlights
• 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
Hewett, Kachru, Peskin, Rizzo, Silverstein, Wacker
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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-BBroader program: CMB Pol, DM direct detection, Jlab, Kloe,
PAMELA/HESS, Planck
Hewett, Kachru, Peskin, Rizzo, Silverstein, Wacker
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Formal Theory Highlights• 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 loopsDirect connections of Formal theory research:SLAC program: ATLAS, KIPAC theory,
Phenomenological thrust, Photon ScienceBroader program: CDF, D0, CMS, Cosmology ,
Pheno
Dixon, Kachru, Silverstein, Weinstein
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The Large Hadron Collider: CERN, Geneva, Switzerland
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The LHC era has begun!
The anticipation has fueled many ideas
November 2007
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CMS
ATLAS
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pp e+e- + anything at the LHC
Yellow = SM background as a function of the binned invariant mass of the two leptons showing statistical fluctuations
Signals for a possible new Z’
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.
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gg H W+ W- e ± ± + neutrinos (=ME) at the Tevatron
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…
10x Higgscontribution
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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+
e-
QED
-
+
2 particles in and 2 particles out
22
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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..
This is the same process in QED but at NLO (with a single loop).. it is STILL 22
‘loops’ occur at NLO
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LO
LO
NLO
NNLO
2n
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This is an important background for Higgs searches as well as for Supersymmetry, one possible new physics scenario
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The Hierarchy ProblemEnergy (GeV)
1019
1016
103
10-18Solar SystemGravity
Weak
GUT
Planckde
sert
Future Collider Energies
All of known physics
mH2 ~ ~ MPl
2
Quantum Corrections:
Virtual Effects dragWeak Scale to MPl
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A Cellar of New Ideas’67 The Standard Model’77 Vin de Technicolor
’70’s Supersymmetry: MSSM
’90’s SUSY Beyond MSSM
’90’s CP Violating Higgs
’98 Extra Dimensions
’02 Little Higgs
’03 Fat Higgs’03 Higgsless’04 Split Supersymmetry’05 Twin Higgs
a classic!aged to perfection
better drink now
mature, balanced, welldeveloped - the Wino’s choice
complex structure
sleeper of the vintagewhat a surprise!
svinters blend
all upfront, no finishlacks symmetry
young, still tannicneeds to develop
bold, peppery, spicyuncertain terrior
J. Hewett
finely-tuned
double the taste
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21
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The Hierarchy Problem: SupersymmetryEnergy (GeV)
1019
1016
103
10-18Solar SystemGravity
Weak
GUT
Planckde
sert
Future Collider Energies
All of known physics
mH2 ~ ~ MPl
2
Quantum Corrections:
Virtual Effects dragWeak Scale to MPl
mH2 ~ ~ - MPl
2
boson
fermion
Large virtual effects cancel order by order in perturbation theory
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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
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• 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
What is the pMSSM ???Berger, Conley, Cotta, Cowley, Gainer, Hewett, Ismail, Le, Rizzo
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pMSSM
Model Generation
LHC & LC
Fermi/Pamela Indirect Detection
CDMS/XENON Direct DetectionICE3
???
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Red=20%, green=50%, blue=100% indicate background systematic errors
Solid=4j, dash=3j, dot=2j final states FLAT
Coverage in the all 3 channels depends quite sensitivelyon how well the backgrounds are understood
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How many models fail to have even one channel with S > some fixed value with L=10 fb-1 and B=20%?
FLAT
These models willbe hard to find no matter what the lumi is…
Benchmark Models?
We are working with both ATLAS & CMSSUSY groups in studying these low-Smodels in detail
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Please come to the theory open house this afternoon!
2:00 Madrone Rm