Theoretical physics Eric Laenen NIKHEF and Utrecht University

Theoretical physics Eric Laenen NIKHEF and Utrecht University Fri. Sept. 23, 2005 RECFA at NIKHEF 1

Dutch theory groups Groningen U. of Amsterdam Free U. , Amsterdam Free U. of Amsterdam Utrecht U. NIKHEF Radboud (Nijmegen) U. Leiden U. Utrecht U. Fri. Sept. 23, 2005 RECFA at NIKHEF 2

Groningen (Ru. G) Groningen (KVI) M. de Roo [Strings & quantum gravity] E. Bergshoeff [Strings & quantum gravity] E. Pallante [Lattice field theory] [50%] R. Timmermans [Baryon interactions, chiral PT, Atomic P violation] O. Scholten [Nucl. Phys. , HE Cosmic rays] 6 Ph. D. ’s, 1 Postdoc 8 papers in 04 2 Ph. D, 1 Postdoc 11 papers in 04 Funding: Ru. G, FOM, EU networks, INTAS, Nordic Network Collaborations: KVI, Utrecht, Cambridge, Kings’s Coll, Brussels, Leuven, Stanford Noteworthy: Pallante starts particle/lattice group, using LOFAR Blue. Gene/L computer String theory cosmology focus Fri. Sept. 23, 2005 Funding: FOM, Ru. G, EU networks Collaborations: VU, Nijmegen, Gent, Osaka, . . Noteworthy: Workshops at Trento, Seattle Close contact with TRIm. P, GSI More ambitions towards astroparticle physics RECFA at NIKHEF 3

Free University (VU) Amsterdam Leiden University P. Mulders [QCD spin ph. , proton structure] D. Boer [QCD spin ph. , phase structure] B. Bakker [Lightfront field th. , hadr. Struct. ] A. Achucarro [Topological/NP field theory and cosmology] P. van Baal [NP Yang-Mills, lattice, Hi. Sparc] W. Van Neerven [pert. QCD at colliders] Lorentz professor [Susskind, Wilczek, Kadanoff] [40 %] 3 to 4 Ph. D. ’s, 1 to 2 Postdocs 8 papers in 04 [30%] Funding: VU, FOM, EU Collaborations: KVI, Torino, Regensburg, BNL, Imperial, Heidelberg Noteworthy: Joint theory Master’s program with Uv. A Good contacts with NIKHEF theory, VU Exp. (Babar/LHCb, HERMES, LISA) 3 to 5 Ph. D’s, 3 to 4 Postdocs 19 papers in 04 Funding: UL, FOM, NOW, EU-RTN, ESF, other countries Collaborations: NIKHEF, Cambridge, Sussex, Berkeley, Madrid, Trinity, Princeton Noteworthy: Workshops at Lorentz Center Fri. Sept. 23, 2005 RECFA at NIKHEF 4

Utrecht G. ‘t Hooft [quantum field theory/gravity] B. de Wit [strings & quantum gravity] R. Loll [quantum gravity] J. Ambjorn [quantum gravity] T. Prokopec [cosmology] G. Aryutanov [strings & quantum gravity ] S. Vandoren [strings & quantum gravity] K. Peeters (‘ 06) [strings & quantum gravity] Kramers professor [Schwimmer, Olive, . . ] [60%] 7 Ph. D’s, 7 Postdocs 33 papers in 04 Funding: UU, FOM, NWO, KNAW, EU, INTAS Collaborations: Uv. A, Groningen, many abroad Nijmegen (Radboud U. ) R. Kleiss [collider physics, QFT methods] W. Beenakker [(B)SM at colliders, EW] T. Rijken [Baryon interactions] 3 Ph. D. ’s 8 papers Funding: RU, FOM, EU Collaborations: Athens, DESY, PSI, Osaka Noteworthy: Good contacts with NIKHEF theory, and Nijmegen HEP [ATLAS/D 0] and PA [Hi. SParc/NAHSA] Noteworthy: Summer school, well-attended Master’s program Fri. Sept. 23, 2005 RECFA at NIKHEF 5

University of Amsterdam (Uv. A) R, Dijkgraaf [Strings & quant. gravity, math. ] J. de Boer [Strings & quant. gravity] E. Verlinde [Strings & quant. Gravity] F. . Bais [Strings & topol. FT] J. Smit [Lattice FT, cosmology] K. Skenderis [Strings & quant. Gravity] M. Taylor-Robinson [Strings & quant. Gravity] K. Schalm [Strings & quant. Gravity] C. van Weert [Thermal field theory] [50%] NIKHEF J. Koch [Fin. T. lattice QCD, RHIC phys. ] B. Schellekens [Strings & quant. gravity] J. W. van Holten [SUSY, Cosmol. , Hi. SPARC] J. Vemaseren [high order p. QCD, FORM] E. Laenen [pert. QCD, heavy quark physics] 5 Ph. D’s, 2 Postdocs 13 papers in 04 Funding: FOM, Uv. A, UU Collaborations: DESY, Durham, Bielefeld, CERN, Torino, Chennai, Madrid 10 Ph. D. ’s, 7 Postdocs 36 papers in 04 Funding: Uv. A, FOM, NWO, EU Collaborations: UU, NIKHEF, NBI, Harvard, CERN, Princeton, Caltech, … Noteworthy: Host of National Seminar Close contact with NIKHEF experiments Noteworthy: Spinoza prize for Dijkgraaf; Highly acclaimed annual summer workshop on Strings Outreach Fri. Sept. 23, 2005 RECFA at NIKHEF 6

Nikhef theory group Activities • • Pursuit of active, wide-ranging research program Close interaction with NIKHEF experiments (analyses, Ph. D. ’s, topical lectures) • Introduce new theoretical developments to NIKHEF • Training of Master’s, Ph. D. students and postdocs • Members have professorships at 4 Universities teaching & exposing students to NIKHEF research Future funding? • • New FOM program with University groups (2007 ? ) EU-RTN networks, NWO, small FOM grants… Special: FORM (Jos Vermaseren) Fri. Sept. 23, 2005 RECFA at NIKHEF 7

Permanent staff/topic in 5 years from now Strings & quantum gravity [14] Groningen (2) Utrecht (5) U. of Amsterdam (6) NIKHEF (1) Lattice & non-pert. FT [4] Groningen (1) KVI-Groningen (2) Leiden (1) Fri. Sept. 23, 2005 Cosmology & PA [3] Leiden (1) Utrecht (1) NIKHEF (1) High-energy collider physics [6] NIKHEF (2) Nijmegen (2) Free U. (2) RECFA at NIKHEF 8

Theory Ph. D students and postdocs Ph. D. students • Total: 40 -50, more than half from NL • 60% continue to postdocs • Education through Dutch Research School for Theoretical Physics Postdocs • About 20 -25 • Mostly non-Dutch (policy) Fri. Sept. 23, 2005 RECFA at NIKHEF 9

Dutch Research School for Theoretical Physics • Offers joint program for education of TH Ph. D. students at 6 universities + NIKHEF via advanced courses • Two themes: 1. Quantum Field Theory and Elementary Particles 2. Condensed Matter and Statistical Physics • Organizes biannual 2 -day symposium with both themes • Organizes yearly Winter Schools in Nijmegen. 2 weeks, 4 lecturers, 25 -30 1 st & 2 nd year Ph. D. students. E. g. 2005: G. ‘t Hooft: Advanced quantum field theory E. Verlinde: String theory and black holes S. Weinzierl: Methods in higher order perturbation theory T. Prokopec: Cosmology Sept. 23, 2005 Theoretical physics 10

Key research topics Strings & quantum gravity Cosmology & PA Holography/Ad. S-CFT Black hole entropy Topological strings Standard Model from strings String cosmology Baryogenesis Domain walls Cosmic scalar fields Lattice & non-pert. field theory Calorons Finite T lattice Light-front, effective theories High-energy collider physics Higgs + t-tbar production Jet production Color glass Spin physics Resummation, top quark physics on lattice Fri. Sept. 23, 2005 RECFA at NIKHEF 11

Theory and Experiment QCD - ATLAS/D 0, HERA PA - Antares/KM 3 Net Structure functions (Next-to-leading order) Monte Carlo’s Jet physics Resummation Cosmic neutrinos Gravitational waves Cosmic Rays Spin - Hermes/Compass EW - LHC, ILC, LEP Radiative corrections Top quark physics Higgs physics Kaon physics Fri. Sept. 23, 2005 Transversity Spin structure functions Heavy Ions - Alice/STAR Finite T lattice Color glass condensate RECFA at NIKHEF 12

Two physics topics 1. 2. Quantum gravity via causal dynamical triangulations [Loll, Ambjorn, . . ] (Utrecht) 3 -loop QCD splitting functions [Vermaseren, Moch, Vogt] (NIKHEF) Fri. Sept. 23, 2005 RECFA at NIKHEF 13

The Universe from Scratch [Loll, Jurkiewicz, Ambjorn] • Minimalist approach to quantum gravity • No strings etc assumed Premise • At very short distances, spacetime fluctuates wildly • No background spacetime; “the stage itself becomes actor” Sanity conditions • Wild geometries at short distance ok • Einstein GR at larger distance Fri. Sept. 23, 2005 RECFA at NIKHEF 14

Tools: Path Integral Path integral • Genuinely non-perturbative • Most paths very weird • Magic of PI: true quantum physics due to superposition • Sum over suitable class of geometries • Sum eventually done on computer Fri. Sept. 23, 2005 RECFA at NIKHEF 15

Tools: Triangulation of spacetime Represent each spacetime in sum by piecewise flat geometries Curvature located at vertices • Edges all common length • Sum over gluings Fri. Sept. 23, 2005 Triangles RECFA at NIKHEF 4 -simplices 16

Inputs Usual Euclidean version produced weird spacetimes, with strange (Hausdorff) dimensions. Dimension is dynamical quantity! Key condition: causal dynamical triangulations (microcausality)! Fri. Sept. 23, 2005 RECFA at NIKHEF 17

Results Dimension of spacetime • Hausdorff dimension: 4! • Dimension (diffusion) at large scale • Dimension at short distance • Glimpse of spacetime near Planck length? Quantum cosmology Scale factor a(t) of Universe CDT allows expansion Fri. Sept. 23, 2005 RECFA at NIKHEF 18

Second order parton evolution kernels [Vermaseren, Moch, Vogt] • Opens gate to 2 nd order perturbation theory at LHC • Marvellous computer algebra tool: FORM • 3 -loop QCD. “Calculation of the decade” Quick acclaim: • 200 citations after 1. 5 year • selected Top Article in Nuclear Physics Earlier, the 4 -loop QCD function. . Fri. Sept. 23, 2005 RECFA at NIKHEF 19

1, 2, 3 & 4 -loop calculators # colors in QCD (strong interaction) # quark flavors (3: “red”, “green” & “blue”) (6: u-, d-, c-, s-, t- & b-quarks) FORM author

Hadronic cross sections and p. QCD Fri. Sept. 23, 2005 RECFA at NIKHEF 21

Theoretical cross section: Input: • hard scattering cross section calculate in perturbative QCD • parton distribution functions PDF determine from benchmark data (DIS) Fri. Sept. 23, 2005 RECFA at NIKHEF 22

Evolution kernels Fri. Sept. 23, 2005 RECFA at NIKHEF 23

How well do we know the PDF’s? Fri. Sept. 23, 2005 RECFA at NIKHEF 24

Evolution kernels in QCD perturbation theory Fri. Sept. 23, 2005 RECFA at NIKHEF 25

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Heroic effort • 20 Man-years • 1 M lines of FORM code • Several CPU years • 10 K diagrams, 100 K integrals Scale dependence at NNLO much better… First NNLO PDF sets appearing Fri. Sept. 23, 2005 RECFA at NIKHEF 28

A corolllary (Moch, Vogt). . Fri. Sept. 23, 2005 RECFA at NIKHEF 29

Prospects for Dutch theoretical physics Staff • A number of retirements coming up. Some positions prefilled. • Strings & quantum gravity effort strong, young • Cosmology & astroparticle physics smallish • Phenomenology not too large, decreasing. Funding of Ph. D. ’s and Postdocs • University funding: under pressure • Present: 3 FOM-TH programs: Universities (<2007), NIKHEF (<2007), Strings (<2009): also under pressure • Very important: new FOM-TH proposal, in preparation. Universities + NIKHEF • Increasingly look toward European funding Fri. Sept. 23, 2005 RECFA at NIKHEF 30