Jacob Sonnenschein (Tel Aviv University and New York University) | Back to Square One: The HISH (holography inspired stringy hadron) model |




String theory was born as a theory of Hadrons. I will briefly review that old picture of stringy hadrons and the reasons it has been abandoned.
A modern version, Holography inspired stringy hadrons (HISH) model, will then be introduced. Mesons, baryons, and exotic hadrons are described as
open strings with massive endpoint particles and glueballs as closed strings. The model is based on a “map” from stringy hadrons of “holographic confining backgrounds” to strings in four dimensional flat space-time.

The HISH model admits “massive modified Regge trajectories”. In particular it includes a novel concept of quark mass, the “ string endpoint mass”. I will  compare the theoretical results with the experimental data and extract the best fits for a universal string tension, quark masses and quantum intercepts. Predictions for yet unobserved higher excited mesons and baryons will be presented.

I will suggest a simple method to identify glueballs by searching for flavorless states on trajectories with a slope which is half the one of the stringy mesons and baryons.

I will suggest to use the state Y(4630), which decays predominantly to ΛcΛc, as a window to the landscape of tetra-quarks. I will propose a simple criterion to decide whether a state is a stringy exotic hadron – a tetra-quark – or a “molecule”. If it is the former it should be on a (modified) Regge trajectory. I will briefly discuss the zoo of other exotic stringy hadrons.

I will further present the predictions for the hadrons strong decay widths and their comparison to the experimental observations. The main decay mechanism is that of a string splitting into two strings. The corresponding total decay width behaves as Γ = πATL/2 where T and L are the tension and length of the string and A is a dimensionless universal constant. The partial width of a given decay mode is given by Γi/Γ = Φi exp(−2πC(m_sep)^2/T) where Φi is a phase space factor, m_sep is the mass of the ”quark” and ”antiquark” created at the splitting point, and C is a dimensionless coefficient close to unity.

Fits to experimental decay widths will be presented. I will discuss the relation to string fragmentation and jet formation. I will extract the quark-di-quark structure of baryons from their decays. A stringy mechanism for Zweig suppressed decays of quarkonia will be proposed and will be shown to reproduce the decay width of Υ states. I will end with several open questions.

When: November 17, 2021 02:00 PM (Jerusalem) via Zoom.