Quantum chromodynamics: string theory meets collider physics

25 Sept 2007, 08:00 → 28 Sept 2007, 18:00 Europe/Berlin

DESY Main Auditorium (DESY Hamburg)

Jochen Bartels (University Hamburg)

DESY THEORY WORKSHOP 2007

The annual DESY Theory Workshop is organized by the elementary particle physics community in Germany. The focus is on a topical subject in theoretical particle physics and related fields. The workshop features:
- One day of introductory lectures, aimed at young participants, but open to everyone
- Four half-day plenary sessions of specialized talks by invited speakers
- One half-day of parallel sessions, allowing young researchers to present their work
- The DESY Heinrich-Hertz-Lecture on Physics for public outreach

Introductory Lectures:

G. Arutyunov (Utrecht), J.F.L. Barbon (Madrid), G. Gustafson (Lund), U. Wiedemann (CERN)

List of speakers

N.Beisert (AEI Golm), V.Braun (Regensburg), B. Cox (Manchester), L.Dixon (Stanford), D.C. Dunbar (Swansea), N.Evans (Southampton), F.Farchioni (Münster), Th.Feldmann (Siegen), S.Gieseke (Karlsruhe), Ph.Hägler (TU München), J. W. Harris (Yale), U.Klein (Liverpool), Y.Kovchegov (Ohio), T. LeCompte (Argonne), L.N.Lipatov (Hamburg), H. Liu (Boston), J.Maldacena (Princeton), D.Mateos (Santa Barbara), A.Mitov (DESY Zeuthen), K.Peeters (Utrecht), M.Teper (Oxford), A.Ukawa (Tsukuba), W.Vogelsang (BNL)

DESY Heinrich-Hertz Lecture on Physics: J. Maldacena (Princeton)

Organizing Committee:

J. Bartels (Hamburg, Chair), V. Schomerus (DESY Hamburg), M. Diehl (DESY Hamburg), K. Jansen (DESY Zeuthen), M. Klein (Liverpool), D. Zeppenfeld (Karlsruhe), M. Beneke (Aachen), A. Schäfer (Regensburg), J. Erdmenger (MPI München), S. Theisen (MPI Potsdam)

Web-page address:

http://www.desy.de/desy-th/workshop2007

hotels hotels.pdf

program program.pdf

Tuesday, 25 September

Introductory lecture I

1 Introduction to AdS/CFT

Speaker: Jose L.F. Barbón (Madrid)

Slides Barbon.pdf

10:45 coffee break

Introductory lecture 2

2 Introduction to Heavy Ion Physics

Speaker: Urs Wiedemann (CERN)

Slides Wiedemann.pdf Wiedemann.ppt

13:00 lunch

Introductory lecture 3

3 Monte Carlo Physics for the LHC

Speaker: Gösta Gustafson (Lund)

Slides Gustafson.pdf

15:45 coffee break

Introductory lecture 4

4 Integrability

Speaker: Gleb Arutyunov (Utrecht)

Slides Arutyunov.pdf

Video Arutyunov_long.avi Arutyunov_short.avi

Wednesday, 26 September

Plenary session I

5 Welcome

Speaker: Albrecht Wagner (DESY)

6 HERA - Results and Perspectives for the LHC

Speaker: Uta Klein (Liverpool)

Slides KleinUta.pdf

7 Tevatron Results

Speaker: Tom Lecompte (Argonne)

Slides LeCompte.pdf LeCompte.ppt

8 Recent Monte Carlo Improvements

Speaker: Stefan Gieseke (Karlsruhe)

Slides Gieseke.pdf

10:55 coffee break

Plenary session II

9 Gluon Scattering Amplitudes at Strong Coupling

Speaker: Juan M. Maldacena (IAS Princeton)

Slides Maldacena.pdf Maldacena.ppt

10 Higher Loop Amplitudes in N=4 SYM

Speaker: David C. Dunbar (Swansea)

Slides Dunbar.pdf Dunbar.ppt

13:00 lunch

Plenary session III

11 QGP from AdS/CFT

Speaker: Kasper Peeters (Utrecht)

Slides Peeters.pdf

12 QCD - Phases and T_c

Speaker: Akira Ukawa (Tsukuba)

Slides Ukawa.pdf Ukawa.ppt

13 Lattice QCD at Small Quark Masses and Overlap Fermions

Speaker: Federico Farchioni (Münster)

Slides Farchioni.pdf

14 Holographic Mesons

Speaker: Nick Evans (Southampton)

Slides evans.pdf

16:30 break

Heinrich Hertz Lecture

15 QCD, Strings and Black Holes: A connection between Gauge Theories and Gravity

Speaker: Juan M. Maldacena (IAS Princeton)

Slides Maldecena-Hertz.pdf Maldecena-Hertz.ppt

19:00 buffet

Thursday, 27 September

Plenary session IV

16 Recent Developments in Small-x Physics

Speaker: Yuri Kovchegov (Ohio)

Slides Kovchegov.pdf Kovchegov.ppt

17 High Energy Behavior in N=4 SYM

Speaker: Lev Lipatov (Hamburg/St.Petersburg)

Slides Lipatov.pdf

18 Differential Cross Sections at NNLO

Speaker: Alexander Mitov (DESY)

Slides Mitov.pdf Mitov.ppt

10:45 coffee break

Plenary session V

19 Integrability in High Energy QCD

Speaker: Vladimir Braun (Regensburg)

Slides Braun.pdf

20 QCD calculations in Heavy Flavor Physics and SCET

Speaker: Thorsten Feldmann (Siegen)

Slides Feldmann.pdf

21 Structure of Hadrons from Lattice Calculations

Speaker: Philipp Hägler (TU München)

Slides Haegler.pdf

13:00 lunch

High Energy QCD

QCD Phenomenology

22 Heavy flavor production in DIS at O(a_s^2) and beyond

QCD precision tests based on deeply inelastic scattering data require the detailed knowledge of the heavy flavor contributions to the structure functions. We report on recent calculations of the heavy flavor Wilson coefficients to O(a_s^2), unpolarized and polarized, in the region Q^2/m^2 => 10 and on first results relevant at O(a_s^3).

Speaker: Mr Sebastian Klein (DESY-Zeuthen)

Slides KleinSebastian.pdf

23 Large mass expansion in two-loop QCD corrections of para-charmonium decay

We calculate the light-by-light scattering type two-loop QCD corrections due to the light quark loops in the para-charmonium decays $eta_{c} rightarrow gamma gamma$ and $eta_{c} rightarrow g g$. We replace the mass of the internal charm quarks by an artificial large mass and obtain the result as a series in the large mass. The obtained series can be transformed into the good convergent ones by a change of the expansion parameter. The results are supported by two other methods to improve the convergence. We also observe that the color singlet state of $eta_{c}$ eliminates the potential divergences in the two-loop QCD corrections. The obtained corrections to the modes $eta_{c} rightarrow gamma gamma$ and $eta_{c} rightarrow g g$ account for -1.25% and -0.73% of the tree level values, respectively.

Speaker: Dr Kouhei Hasegawa (Desy Zeuthen, Theory group)

Slides Hasegawa.pdf

24 Charged Current DIS at three loops

In this presentation I would like to discuss technical and computational problems on the derivation of the perturbative QCD corrections to three loops for the charged current structure functions F_2, F_L and F_3 for deep-inelastic neutrino-proton scattering in the combination "nu P - nubar P". In leading twist approximation we calculate the first six odd-integer Mellin moments in the case of F_2 and F_L and the first five even-integer moments in the case of F_3 . As a new result we obtain the coefficient functions to O(alpha_s^3) while the corresponding anomalous dimensions agree with known results in the literature.

Speaker: Dr Mikhail Rogal (DESY, Zeuthen)

Slides Rogal.pdf

String theory (1)

25 Early Time Dynamics in Heavy Ion Collisions from AdS/CFT Correspondence

We study the matter produced in heavy ion collisions assuming that this matter is strongly interacting and employing AdS/CFT correspondence to investigate its dynamics. At late proper times $\tau$ we show that Bjorken hydrodynamics solution, obtained recently by Janik and Peschanski using gauge-gravity duality, can be singled out by simply requiring that the metric tensor is a real and single-valued function of the coordinates everywhere in the bulk, without imposing any constraints on the curvature invariant. At early proper times we use similar strategy to show that the energy density $\epsilon$ approaches a constant as $\tau \rightarrow 0$. We therefore demonstrate that the strong coupling dynamics incorporates the isotropization transition in heavy ion collisions. By matching our early-time regime with the late-time one of Janik and Peschanski we estimate the isotropization time at RHIC to be approximately $\tau_{\text{iso}} \approx 0.3$~fm/c, in good agreement with results of hydrodynamic simulations.

Speaker: Prof. Yuri Kovchegov (Ohio State University)

Slides Kovchegov-parallel.pdf Kovchegov-parallel.ppt

26 Isospin diffusion in thermal AdS/CFT with flavor

Using a generalization of the AdS/CFT correspondence, it is possible to determine thermodynamic properties of strongly coupled field theories. Aiming for a description of the characteristics of systems such as the quark gluon plasma, we study the gauge/gravity dual of a finite temperature field theory at finite isospin chemical potential. Therefore we introduce a probe of two coincident D7-branes in the AdS-Schwarzschild black hole background. The isospin chemical potential is obtained by giving a vev to the time component of the non-Abelian gauge field on the brane. The gauge/gravity duality allows to obtain SU(2) flavor current correlators by examining gauge field fluctuations. We discuss the properties of these correlators which go beyond linear response theory. In particular, we show that the isospin chemical potential leads to a frequency-dependent isospin diffusion coefficient.

Speaker: Felix Rust (Max-Planck-Institut für Physik, München)

Slides Rust.pdf

27 Flavors from time-dependent D7 embeddings

We consider flavors in a holographic description of a boost-invariant viscous plasma by embedding D7 branes into the dual geometry. We obtain the (time-dependent) chiral quark condensate and meson spectra. To first order both agree with the adiabatic approximation, i.e. the prediction from the static AdS black hole. For very late times the supersymmetric configurations are approached.

Speaker: Dr Johannes Grosse (Institute of Physics, Jagiellonian University)

Slides Grosse.pdf

String theory (2)

28 Conformal spins at colliders and BFKL versus gravitational collapse.

Firstly, we review the Moebius invariance present in the Regge limit of perturbative QCD, and argue that the associated conformal spins are related to azimuthal angle correlations in the hadro-production of dijets. Secondly, we report on progress in the study of the connection between unitarity corrections at small x and critical behaviour of gravitational collapse in five dimensions.

Speaker: Dr Agustin Sabio Vera (CERN)

Slides SabioVera.pdf

29 High energy limit of R-current scattering in N=4 SYM

We address the computation of the four-point function of R-currents in N=4 SYM in the Regge limit as a tool to study such regime in a gauge invariant framework. The R-current is a close analog of the EM current in QED and SQED, which couple a gauge invariant state ('photon') to a YM system. Gauge invariance guarantee that the amplitude is free from infrared divergences. We discuss some subtlelties associated with the fact the R-current are not associated with a gauge symmetry.

Speaker: Dr Michele Salvadore (II. Institut fuer Theoretische Physik, Universitaet Hamburg)

Slides Salvadore.pdf

30 Reggeon transition vertices from the gauge invariant effective action

We investigate the derivation of reggeon transition vertices from Lipatov's gauge invariant effective action for high energy processes in QCD. In particular we address the question of longitudinal integrations in order to reduce the vertices into the required purely transverse form. We present a momentum space derivation of the BFKL-kernel and verify the vanishing of the 2 to 3 reggeon transition vertex. In addition we show first results on the derivation of the 2 to 4 reggeon transition vertex.

Speaker: Mr Martin Hentschinski (University of Hamburg)

Slides hentschinski.pdf

16:00 coffee break

High Energy QCD (continued)

31 Central jet production vertex in NLO kt-factorization

We discuss the inclusive production of jets in central regions of rapidity in the context of $k_T$-factorization at next-to-leading order (NLO). Calculations are performed in the Regge limit making use of the NLO BFKL results. We introduce a jet cone definition and carry out a proper phase-space separation into multi-Regge and quasi-multi-Regge kinematic regions. We discuss two situations: scattering of highly virtual photons, which requires a symmetric energy scale to separate impact factors from the gluon Green's function, and hadron-hadron collisions, where a non-symmetric scale choice is needed.

Speaker: Dr Schwennsen Florian (Universitaet Hamburg)

Slides Schwennsen.pdf

32 On baryon scattering in QCD

Impact-factors are presented corresponding to a baryon scattering at large energies by 2,3 and 4 gluon coupling. The small-x evolution of the impact factors is studied for various numbers of Reggeons in the t-channel. We find a new C-even BKP state that couples to baryons and a new 3->4 Reggeon transition vertex.

Speaker: Dr Leszek Motyka (Hamburg University and Jagellonian University)

Slides Motyka.pdf

33 Two loop virtual QCD corrections to W pair production at the LHC

Gauge boson production at the LHC

Speaker: Dr Grigorios Chachamis (University of Wuerzburg)

Slides Chachamis.pdf

QCD Phenomenology (continued)

34 Two loop O(G_F^2 m_t^4) correction to the Higgs decay into bottom quarks

In most of the mass range encompassed by the limits from the direct search and the electroweak precision test, the Higgs boson of the standard model preferably decays to bottom quarks. We calculated, in analytic form, the dominant two-loop electroweak correction, of O(G_F^2 m_t^4), to the partial width of this decay. It amplifies the familiar enhancement due to the O(G_F m_t^2) one-loop correction by about +16% and thus more than compensates the screening by about -8% through strong-interaction effects of O(alpha_s G_F m_t^2). In this talk I will present the results and describe the most important conceptual and technical details.

Speaker: Mr Mathias BUTENSCHÖN (Universität Hamburg)

Slides Butenschoen.pdf

35 Neutralino neutralino annihilation to gamma Z in MSSM

The 1-loop computation of the processes $\tchi_i \tchi_j \to \gamma Z$ has been performed at an arbitrary c.m. energy for any pair of MSSM neutralinos. As an application suitable for Dark Matter (DM) searches, the neutralino-neutralino annihilation is studied at the limiting case of vanishing relative velocity, describing the present DM distribution in the galactic halo; and at a relative velocity of about 0.5, determining the neutralino relic density contributions. Our results are contained in the FORTRAN code PLATONdmgZ, applying to any set of real MSSM parameters. Numerical results are also presented for a sample of 6 MSSM models, describing the various possible neutralino properties. A comparison with other existing works is also made.

Speaker: Dr theodoros diakonidis (DESY, Zeuthen)

Slides Diakonidis.pdf

36 Hadronic $B$ Decays in the MSSM with Large $\tan \beta$

I present an analysis of Hadronic $B$ decays in the MSSM with large $\tan \beta$. I consider all new four-quark operators arising in the MSSM and I give estimates for the corresponding Wilson coefficients. I select the most relevant new four-quark operators and I calculate their contribution to non leptonic $B$ decays. Significant differences with the SM are found in penguin dominated $B$ decays, for $\tan \beta \geq 40$. Various estimates for relevant branching ratios, CP asymmetries and others $B$ physics observables are given.

Speaker: Mr Leonardo Vernazza (Institute für Theoretische Physik E, RWTH Aachen)

Slides Vernazza.pdf

String theory (1) (continued)

37 AdS/CFT with Flavour and constant Kalb-Ramond field

We investigate the effect of a pure electric or magnetic Kalb-Ramond B-field on the physics of a D7 brane probe in the context of the AdS/CFT correspondence, both at finite and zero temperature. We find a confinement/deconfinement phase transition in both cases, and chiral symmetry breaking for the magnetic field. The general behaviour is that the magnetic field acts confining, while the electric field acts deconfining by ionizing the mesons. We also investigate the s- state meson spectra and find a shift for the zero temperature electric case similar to the second-order Stark effect.

Speaker: Mr René Meyer (Max-Planck-Instute for Physics, Munich, Germany)

Slides Meyer.pdf

38 Heavy-light mesons from AdS/CFT

In this talk I show how heavy-light mesons can be studied using the AdS/CFT correspondence. For this I embed two D7 brane probes at different positions into the dual supergravity background. I establish the non-Abelian Dirac-Born-Infeld (DBI) action for these probes which involves a 2x2 matrix. The off-diagonal elements of this U(2) fluctuation matrix correspond to the heavy-light mesons, while the diagonal elements correspond to the light-light and heavy-heavy mesons, respectively. Among other results, I find that heavy-light mesons scale differently with the 't Hooft coupling than the mesons involving quarks of equal mass.

Speaker: Dr Ingo Kirsch (ETH Zuerich)

Slides Kirsch.pdf

39 Diquark masses from AdS/QCD potential

AdS/QCD correspondence is able to predict quark-antiquark potential in the static limit [1]. We use this piece of information together with the Salpeter equation (Schroedinger equation with relativistic kinematics) and a short range hyperfine splitting potential to determine quark masses and quark potential parameters. Assuming a quark-diquark structure for the S-wave low-lying baryons allows to determine light diquark masses. A discussion of heavy diquark masses, based on the hypothesis of a diquark-antidiquark structure for the states X(3872) and X(3940) [2] is also presented. [1] O. Andreev and V. Zakharov, Phys. Rev. D 74 (2006) 025023 [arXiv: hep-ph/0604204]. [2] L. Maiani, F. Piccinini, A.D. Polosa, V. Riquer, Phys. Rev. D 71 (2005) 014028 [arXiv: hep-ph/0412098].

Speaker: Ms Floriana Giannuzzi (University of Bari and INFN sezione di Bari)

Slides Giannuzzi.pdf

40 Meson and baryon excitations in AdS/QCD

We construct an approximate holographic dual of QCD from experimental hadron properties. Conformal symmetry breaking and other IR effects are described exclusively by deformations of the anti-de Sitter background metric. This framework allows us to reproduce the empirically found linear square-mass trajectories of universal slope for radially and orbitally excited hadrons. The predictions for the light hadron spectrum include new relations between ground state masses and trajectory slopes and are in good overall agreement with experimental data.

Speaker: Dr Michael Beyer (Institut für Physik, Univ. Rostock)

Slides Beyer.pdf Beyer.ppt

String theory (2) (continued)

41 The standard model on twistor space

Many recent advances in the calculation of scattering amplitudes are inspired by insights from twistor space as initiated by Witten. However, little direct use has been made untill recently of the extra structure available on the twistor space. Partly based on joint research with Lionel Mason and David Skinner, I will present a simple method of deriving actions on twistor space from any given four dimensional theory with matter with spin less than or equal to one. In particular, the method applies to the standard model. Extra gauge symmetry on the twistor space allows one to choose a gauge which reproduces MHV/CSW- style Feynman rules. On space-time, I will show that this corresponds to a non- local and non-linear field transformation.

Speaker: Dr Rutger Boels (Niels Bohr International Academy (from sept. 1))

Slides Boels.pdf

42 Wilson loops in 4d SYM and in 2d YM

I will present some new results about supersymmetric Wilson loops in four dimensional YM. First I will present a large class of operators preserving 1/2, 1/4, 1/8 and 1/16 of the supersymmetries of the vacuum. Then I will show a possible realtion between some of those loops, following an arbitrary curve on an S^2 subspace of R^4 to Wilson loops in two dimensional YM. To the extent that we've been able to calculate, there is a precise agreement, suggesting another connection between certain operators in N=4 SYM and low dimensional soluable models.

Speaker: Dr Nadav Drukker (Humboldt University)

Slides Drukker.pdf

43 Yang-Mills and Gravity Scattering Amplitudes from Twistor Strings

I review the recent construction of a family of new twistor string theories which are free from world-sheet anomalies and give the space-time spectra of Einstein supergravities, with second order field equations, instead of the higher derivative conformal supergravities that arose from earlier twistor strings. I then discuss the calculation of gauge theory and gravity amplitudes in the new theories.

Speaker: Dr Mohab Abou Zeid (Institut des Hautes Etudes Scientifiques, Bures-sur-Yvette)

Slides AbouZeid.pdf

Friday, 28 September

Plenary session VI

44 Heavy Ions - Results and Interpretation

Speaker: John W. Harris (Yale)

Slides Harris.pdf

45 String Theory and RHIC Physics: The Fundamental Story

Speaker: David Mateos (Santa Barbara)

Slides Mateos.pdf

46 Drag Force and Jet Quenching from AdS/CFT

Speaker: Hong Liu (Boston)

Slides Liu.pdf Liu.ppt

11:00 coffee break

Plenary session VII

47 Spin Physics at RHIC

Speaker: Werner Vogelsang (BNL)

Slides Vogelsang.pdf

48 Diffractive Physics at the LHC

Speaker: Brian Cox (Manchester)

Slides Cox.pdf

12:45 lunch

Plenary Session VIII

49 Anomalous Dimensions and Integrability in AdS/CFT

Speaker: Niklas Beisert (AEI Golm)

Slides Beisert.pdf

50 Large N - the View from the Lattice

Speaker: Michael Teper (Oxford)

Slides Teper.pdf

51 Loop Calculations of Amplitudes with Many Legs

Speaker: Lance Dixon (Stanford)

Slides Dixon.pdf Dixon.ppt