arXiv subjects

N. Losacco

Publications and source records attributed to N. Losacco.

5 recordsLinked to original sources

arXiv2022

Holographic Study of the $ Q \bar Q$ Chaotic Dynamics in General Thermal Background

The holographic approach is applied to study the chaotic behaviour of a strongly coupled $Q \bar Q$ pair in general thermal background. We consider two different backgrounds, one with finite temperature and baryon density, and one with finite temperature and constant magnetic field along a fixed direction. The results allow us to understand the dependence of the chaotic dynamics on the background, to test the universal bound on chaos conjectured by Maldacena, Shenker and Standford (MSS)

hep-ph↗

arXiv2022

Relations among $B_c \to J/ψ, η_c$ form factors

We analyze the form factors parametrizing the $B_c \to J/ψ, η_c$ matrix elements of the operators in a generalized low-energy $b \to c$ semileptonic Hamiltonian. We consider an expansion in nonrelativistic QCD, classifying the heavy quark spin symmetry breaking terms and expressing the form factors in terms of universal functions in a selected kinematical range. Using as an input the lattice QCD results for the $B_c \to J/ψ$ matrix element of the SM operator, we obtain information on other form factors. The extrapolation to the full kinematical range is also presented.

hep-ph↗

arXiv2022

Semileptonic $B_c$ decays to $P-$wave charmonium and the nature of $χ_{c1}(3872)$

The hadronic form factors of $B_c$ semileptonic decays to the $P-$wave charmonium 4-plet can be expressed near the zero-recoil point in terms of universal functions, performing a systematic expansion in QCD in the relative velocity of the heavy quarks and in $1/m_Q$. Such functions are independent of the member of the multiplet involved in the transitions. We present the results of an NLO calculation up to $O(1/m_Q^2)$ classifying the universal functions at this order. We work out a set of relations among the form factors of the same mode and of different modes, which should be reproduced by explicit calculations, reducing the hadronic uncertainty affecting such channels. The approach is also helpful to investigate the debated nature of $χ_{c1}(3872)$, studying the production in $B_c$ semileptonic decays and comparing it to the modes involving the other $2P$ charmonia.

hep-ph↗

arXiv2022

Baryon density and magnetic field effects on chaos in a $Q \bar Q$ system at finite temperature

Baryon density and magnetic field effect on chaos for the holographic dual of a $Q \bar Q$ system at finite temperature is studied. A string in an AdS Reissner Nordstrom background, and in a metric with magnetic field near the black hole horizon is considered and small time-dependent perturbations of the static configurations are investigated. The proximity to the horizon induces chaos, which is softened increasing the chemical potential or the magnetic field. A background geometry including the effect of a dilaton is also examined. The Maldacena, Shenker, and Stanford bound on the Lyapunov exponents characterizing the perturbations is satisfied for finite baryon chemical potential and magnetic field and when the dilaton is included in the metric.

hep-ph↗

arXiv2020

Chaos in a $Q \bar Q$ system at finite temperature and baryon density

Onset of chaos for the holographic dual of a $Q \bar Q$ system at finite temperature and baryon density is studied. We consider a string in the $AdS$ Reissner-Nordstrom background near the black-hole horizon, and investigate small time-dependent perturbations of the static configurations. The proximity to the horizon induces chaos, which is softened increasing the chemical potential. A background geometry including the effect of a dilaton is also examined. The Maldacena, Shenker and Stanford bound on the Lyapunov exponents characterizing the perturbations is satisfied for finite baryon chemical potential and when the dilaton is included in the metric.

hep-ph↗