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Register a new userA review of quarkonia under strong magnetic fields
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We review the properties of quarkonia under strong magnetic fields. The main phenomena are (i) mixing between different spin eigenstates, (ii) quark Landau levels and deformation of wave function, (iii) modification of $bar{Q}Q$ potential, and (iv) the motional Stark effect. For theoretical approaches, we review (i) constituent quark models, (ii) effective Lagrangians, (iii) QCD sum rules, and (iv) holographic approaches.
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In this thesis is studied three of the fundamental properties of clusters of matter made of quarks u, d and s called strangelets: the energy per baryon, the radius and the electric charge, all in the presence of intense magnetic fields and finite temperature. Two cases will take our attention: unpaired phase strangelets, where there is no restriction to the number of flavors of quarks, and a particular case of the color superconducting phase, where exists a restriction to the quark numbers and an additional energy gap. We study the stability of strangelets, measured by the energy per baryon, to compare later with that of the 56Fe : the most stable isotope known in nature. We employ the Liquid Drop formalism of the Bag Model MIT to describe the interaction between quarks. We conclude that the field effects tend to decrease the energy per baryon of strangelets and temperature produces the opposite effect. It is also shown that strangelets in the color superconducting phase are more stable than those in the unpaired phase for an energy gap of about 100MeV. The radius of strangelets shows an analogous behavior with the baryon number, as that of the nuclei, and shows small variations with the magnetic field and temperature. It is obtained that the presence of magnetic fields modify the values of the electric charge regarding the non-magnetized case, being these higher (lower) for strangelets in the unpaired phase (superconducting).
We have investigated the effects of strong magnetic field on the properties of quarkonia immersed in a thermal medium of quarks and gluons and studied its quasi-free dissociation due to the Landau-damping. Thermalizing the Schwinger propagator in the lowest Landau levels for quarks and the Feynman propagator for gluons in real-time formalism, we have calculated the resummed retarded and symmetric propagators, which in turn give the real and imaginary components of dielectric permittivity, respectively. The magnetic field affects the large-distance interaction more than the short-distance interaction, as a result, the real part of potential becomes more attractive and the magnitude of imaginary part too becomes larger, compared to the thermal medium in absence of strong magnetic field. As a consequence the average size of $J/psi$s and $psi^prime$s are increased but $chi_c$s get shrunk. Similarly the magnetic field affects the binding of $J/psi$s and $chi_c$s discriminately, i.e. it decreases the binding of $J/psi$ and increases for $chi_c$. However, the further increase in magnetic field results in the decrease of binding energies. On contrary the magnetic field increases the width of the resonances, unless the temperature is sufficiently high. We have finally studied how the presence of magnetic field affects the dissolution of quarkonia in a thermal medium due to the Landau damping, where the dissociation temperatures are found to increase compared to the thermal medium in absence of magnetic field. However, further increase of magnetic field decreases the dissociation temperatures. For example, $J/psi$s and $chi_c$s are dissociated at higher temperatures at 2 $T_c$ and 1.1 $T_c$ at a magnetic field $eB approx 6~{rm{and}}~4~m_pi^2$, respectively, compared to the values 1.60 $T_c$ and 0.8 $T_c$ in the absence of magnetic field, respectively.
We develop a formalism for computing inclusive production cross sections of heavy quarkonia based on the nonrelativistic QCD and the potential nonrelativistic QCD effective field theories. Our formalism applies to strongly coupled quarkonia, which include excited charmonium and bottomonium states. Analogously to heavy quarkonium decay processes, we express nonrelativistic QCD long-distance matrix elements in terms of quarkonium wavefunctions at the origin and universal gluonic correlators. Our expressions for the long-distance matrix elements are valid up to corrections of order $1/N_c^2$. These expressions enhance the predictive power of the nonrelativistic effective field theory approach to inclusive production processes by reducing the number of nonperturbative unknowns, and make possible first-principle determinations of long-distance matrix elements once the gluonic correlators are known. Based on this formalism, we compute the production cross sections of $P$-wave charmonia and bottomonia at the LHC, and find good agreement with measurements.
Correlations between the QCD coupling alpha_s, the gluon condensate < alpha_s G^2 >, and the c,b-quark running masses m_c,b in the MS-scheme are explicitly studied (for the first time) from the (axial-)vector and (pseudo)scalar charmonium and bottomium ratios of Laplace sum rules (LSR) evaluated at the mu-subtraction stability point where PT @N2LO, N3LO and < alpha_s G^2> @NLO corrections are included. Our results clarify the (apparent) discrepancies between different estimates of < alpha_s G^2> from J/psi sum rule but also shows the sensitivity of the sum rules on the choice of the mu-subtraction scale which does not permit a high-precision estimate of m_c,b. We obtain from the (axial-)vector [resp. (pseudo)scalar] channels <alpha_s G^2>=(8.5+- 3.0)> [resp. (6.34+-.39)] 10^-2 GeV^4, m_c(m_c)= 1256(30) [resp. 1266(16)] MeV and m_b(m_b)=4192(15) MeV. Combined with our recent determinations from vector channel, one obtains the average: m_c(m_c)= 1263(14) MeV and m_b(m_b) 4184(11) MeV. Adding our value of the gluon condensate with different previous estimates, we obtain the new sum rule average: <alpha_s G^2>=(6.35+- 0.35) 10^-2 GeV^4. The mass-splittings M_chi_0c(0b)-M_eta_c(b) give @N2LO: alpha_s(M_Z)=0.1183(19)(3) in good agreement with the world average (see more detailed discussions in the section: addendum). .
We investigate the strong force fields and stabilities of the nucleon and the singly heavy baryon $Sigma_c$ within the framework of the chiral quark-soliton model. Having constructed the pion mean fields in the presence of the $N_c-1$ level quarks self-consistently, we are able to examine the gravitational form factors of $Sigma_c$. We mainly focus in the present work on the stability conditions for both the nucleon and $Sigma_c$ and discuss the strong force fields and their physical implications. We also present the results for the gravitational form factors and relevant observables, emphasising the difference between the nucleon and $Sigma_c$.
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