HELSINKI INSTITUTE OF PHYSICS SEMINARS
HIP seminar room A315
- Tuesday 30 July 2019 at 14.15 in A315: Stan Brodsky (SLAC)
Meson/Baryon/Tetraquark Supersymmetry from Superconformal Algebra and Light-Front Holography
Abstract: Superconformal algebra leads to remarkable connections between the masses of mesons and baryons of the same parity — supersymmetric relations between the bosonic and fermionic bound states of QCD. Supercharges connect the mesonic eigenstates to their baryonic superpartners, where the mesons have internal angular momentum one unit higher than the baryons. We also predict the existence of tetraquarks which are degenerate in mass with baryons with the same angular momentum. An effective supersymmetric light-front Hamiltonian for hadrons composed of light quarks can be constructed by embedding superconformal quantum mechanics into AdS space. The breaking of conformal symmetry determines a unique quark-confining light-front potential for light hadrons including spin-spin interactions in agreement with the soft-wall AdS/QCD approach and light-front holography. The mass-squared of the light hadrons can be expressed as a frame-independent decomposition of contributions from the constituent kinetic energy, the confinement potential, and spin-spin contributions. The mass of the pion eigenstate vanishes in the chiral limit. Only one mass parameter appears; it sets the confinement mass scale, a universal value for the slope of all Regge trajectories, the nonzero mass of the proton and other hadrons in the chiral limit, as well as the mass parameter of the pQCD running coupling. The result is an effective coupling defined at all momenta. The matching of the high and low momentum-transfer regimes determines a scale Q_0 which sets the interface between perturbative and nonperturbative hadron dynamics. as well as the factorization scale for structure functions and distribution amplitudes. This procedure, in combination with the scheme-independent PMC procedure for setting renormalization scales, can greatly improve the precision of QCD predictions.
- Tuesday 6 August 2019 at 10.15 in A315: Jacob Sonnenschein (Tel Aviv)
Recent result of the HISH ( Holography inspired stringy hadron) model
Abstract: Holography inspired stringy hadron (HISH) is a model that describes hadrons as strings in four dimensional flat space-time. For mesons, baryons and exotics- open strings with endpoint (massive) particles, and for glueballs- closed strings. In the first part of the talk I will summarize the derivation and the results of the model. In particular the spectra and decay width of hadrons including possible identification of glue-balls and exotic hadrons. I will compare these results with the PDG experimental data. In the second part of the talk I will describe the quantization of a string with massive endpoints. This will include the classical solutions of rotating strings and the transverse and planar quantum fluctuations in the quadratic approximation. I will introduce an alterna-
tive method of renormalizing the system and computing the intercept. Next I will discuss the modification due to the non-criticality of the string and present the HISH Regge-like trajectories. In the third part I will describe the derivation of the scattering amplitude of strings with charges on their endpoints in constant electro-magnetic fields. I will determine the corresponding OPEs and derive the modification of the Veneziano amplitude. This will include a change of the target space metric and phases due to the underlying non-commutative geometry
- Tuesday 13 August 2019 at 10.15 in A315: Philipp Schicho (Bern)
3-Loop Gauge Coupling in Hot QCD
Abstract: Dimensionally reduced effective theories have been very successful for studying the thermodynamics of non-Abelian gauge theories. In the context of the dimensionally reduced effective theory for thermal QCD (“EQCD”), I will go through its construction and the relevant scales of hot QCD including the coupling renormalisation of “magnetostatic” QCD (“MQCD”). A recent computation of the latter shows a leftover logarithmic divergence originating from 3-loop effects from non-zero Matsubara modes. Therefore, I will demonstrate, through 1-loop and 2-loop computations that it is vital to include dimension-six vertices and that their effects are in general of the same order or larger than the hard-mode contribution.
- Tuesday 27 August 2019 at 10.15 in A315: Tommi Tenkanen (Johns Hopkins University)
Spectator Dark Matter
Abstract: The observed dark matter abundance in the Universe can be fully accounted for by a minimally coupled spectator scalar field that was light during inflation and has sufficiently strong self-coupling. In this scenario, dark matter was produced during inflation by amplification of quantum fluctuations of the spectator field. The self-interaction of the field suppresses its fluctuations on large scales, and therefore avoids isocurvature constraints. The scenario does not require any fine-tuning of parameters. I will also discuss ways to test the scenario.
- Tuesday 27 August 2019 at 14.15 in A315: Tiina Naaranoja (University of Helsinki)
Diamond Time-of-Flight Detectors and their Radiation Tolerance
- Tuesday 1 October 2019 at 14.15 in A315: Graham White (Triumf, Canada)
Hopefully the up to 50 min + 10 min discussion long seminar/colloquium will be understandable to a wide audience.
Contacts: Keijo Kajantie (keijo kajantie at helsinki fi) [ HIP seminar],
Sofie Koksbang (sofie koksbang at helsinki fi) [cosmo seminar]
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