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Selected results of department 29

The LHC was built to probe details of the electroweak symmetry breaking mechanism which is, as we believe today, responsible for generating masses of particles. We have proposed a method to probe the quartic boson interactions (γγ → γγ) in two-photon exchanges with forward proton tagging devices. Very small deviations from the Standard Model prediction, found for example in extra models with dimension, could become observable. These forward devices are already being constructed.

O. Kepka, B. Lenzi, S. Fichet, C. Royon, M. Saimpert, Phys.Rev. D89 (2014) 114004. The whole text »

This work is a detailed study of the holographic duality between Vasiliev's higher spin theory and two-dimensional minimal model conformal field theories (CFTs) with WN symmetry. It uses symmetry arguments to identify the precise states dual to conical defects, correcting an earlier proposal, and to excitations of Vasiliev's scalar field. This work is important as it shows a highly nontrivial matching of the spectra of the CFT and Vasiliev's theory.

Perlmutter, E. ; Procházka, Tomáš ; Raeymaekers, Joris; JHEP 1305 (2013) 007. The whole text »

This paper provides an exact analytic solution for the tachyon vacuum on a non-BPS D-brane in open superstring field theory. This gave the first rigorous proof of Sen's conjectures in superstring theory, provided intriguing hints into the topological origin of D-brane charge, and established that nonperturbative solutions could be constructed in superstring field theory.

T. Erler, JHEP 1311 (2013) 007. The whole text »

For a long time scientists suspected relation between classical solutions of open string field theory and D-brane configurations in string theory which can be described by boundary states of conformal field theory. In this paper we have proposed for the first time a very explicit construction of such a state from a given classical solution. This has opened new possibilities for using string field theory as a tool to study new boundary conditions in 2D conformal field theories.

Kudrna, Matěj ; Maccaferri, Carlo ; Schnabl, Martin; JHEP 1307 (2013) 033. The whole text »

The TOTEM collaboration has measured for the first time the proton-proton total cross section at energy of 8 TeV using a luminosity-independent method based on the application of the optical theorem. The measurements of the total nuclear elastic rate Nel and of the total inelastic rate Ninel have given the following values for the total cross section, integrated elastic and inelastic cross sections: σtot=(101.7±2.9) mb, σel =(27.1 ± 1.4) mb and σinel =(74.7±1.7) mb.

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The classical solutions of open string field theory are solitonic extended objects whose fluctuation spectra are described by open strings. At the turn of the millennium, Ashoke Sen discovered that tachyonic modes lead to instabilities of these solitionic objects and that there are classical solutions describing various endpoints with the expected properties, and among them a solution with no soliton. A group of researchers at MIT speculated that reverse phenomenon might occur, namely that there can be classical solutions describing multiple xerox copies of the original soliton. The whole text »

This paper established a groundbreaking result in Anti-de Sitter (AdS) gravity coupled to massless higher spin fields in three dimensions. It was found that these theories have a rich spectrum of smooth soliton-like solutions, which can be viewed as conical defects resolved by the higher spins. What is especially exciting about these solutions is that their quantum numbers are in beautiful agreement with those of certain states in a two-dimensional conformal field theory (CFT) in the appropriate classical limit. The whole text »

Study of heavy ion collisions at ultra high energies represents a major subject in the contemporary nuclear and particle physics. The fundamental motivation is to understand the properties of the new state of matter known as quark-gluon plasma which is predicted by Quantum Chromo-Dynamics to occur at very high temperatures and energy densities. In this work the ALICE experiment at LHC in CERN measured the azimuthal distribution of particles and found that the plasma behaves as a viscous fluid.

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Due to electroweak (EW) symmetry breaking, the couplings between three and four EW bosons are related. While cubic boson interactions are already well constrained experimentally, quartic gauge boson couplings (QGC) are not. We have proposed a method to probe QGC (γγ → WW, ZZ) in exclusive processes with forward proton tagging devices. Since much higher sensitivities can be attained in contrast to using conventional methods, the physics potential of the forward detector is high.

Chapon, E. ; Royon, C. ; Kepka, Oldřich, Phys.Rev. D81 (2010) 074003. The whole text »

Transverse momentum dependent distribution functions (TMDs) open a new way to a more complete understanding of the quark-gluon structure of the nucleon. TMDs involve important information about motion of quarks inside the nucleon, which reflects also the quark orbital momentum. The TMDs are still poorly known experimentally, but relations obtained in the paper allow us to predict them on the basis of ordinary parton distributions, which are known much better.

Efremov, A.V. ; Schweitzer, P. ; Teryaev, O.V. ; Závada, Petr, Phys.Rev. D80 (2009) 014021. The whole text »