Nuclear Theory·nucl-th

Friday·June 8, 2018

6 papers—3 primary·3 cross-listed

04
Threshold corrections of $χ_{c} (2 P)$ and $χ_{b} (3 P)$ states and $J / ψ ρ$ and $J / ψ ω$ transitions of the $X (3872)$ in a coupled-channel model
J. Ferretti🇨🇳 · E. Santopinto🇮🇹
We calculate the masses of $χ_{c} (2 P)$ and $χ_{b} (3 P)$ states with threshold corrections in a coupled-channel model. Here, the meson quarkonium core is augmented by higher Fock components due to pair-creation effects. According to our results, we interpret the resonances characterized by very small threshold corrections, like $χ_{b} (3 P)$ 's, as almost pure quarkonia, and those states characterized by non-negligible threshold corrections, like the $X (3872)$ , as quarkonium cores plus meson-meson components. We also study the $J / ψ ρ$ and $J / ψ ω$ hidden-flavor strong decays of the $X (3872)$ . The decays are calculated as the dissociation of one of these components ( $D^{0} D ˉ^{0 *}$ ) into a $c c ˉ$ state ( $J / ψ$ ) plus a light meson ( $ρ$ or $ω$ ) in a potential model. In particular, our result for the ratio between the $X (3872) \to J / ψ ω$ and $J / ψ ρ$ widths (0.6) is compatible with the present experimental data ( $0.8 \pm 0.3$ ) within the experimental error.
↳ hep-phnucl-thPLB(2019)·45 citations
05
Thermodynamic versus kinetic approach to polarization-vorticity coupling
Wojciech Florkowski🇵🇱 · Avdhesh Kumar🇵🇱 · Radoslaw Ryblewski🇵🇱
We critically compare thermodynamic and kinetic approaches, that have been recently used to study relations between the spin polarization and fluid vorticity in systems consisting of spin-one-half particles. The thermodynamic approach refers to general properties of global thermal equilibrium with a rigid-like rotation and demonstrates that the spin-polarization and thermal-vorticity tensors are equal. On the other hand, the kinetic approach uses the concept of the Wigner function and its semi-classical expansion. In most of the works done so far, the Wigner functions satisfy kinetic equations with a vanishing collision term. We show that this assumption restricts significantly applicability of such frameworks and, in contrast to many claims found in the literature, does not allow for drawing any conclusions regarding the relation between the thermal-vorticity and spin-polarization tensors, except for the fact that the two should be constant in global equilibrium. We further show how the kinetic-theory equations including spin degrees of freedom can be used to formulate a hydrodynamic framework for particles with spin. We define hydrodynamic equations starting separately from the formulation by de~Groot, van~Leeuwen, and van~Weert and from the canonical formalism. In the former case the energy-momentum tensor is symmetric and the spin tensor is conserved, while in the later case the energy-momentum tensor is not symmetric and the spin tensor is not conserved. Nevertheless, in the two cases the total angular momentum is always conserved. Interestingly, the two approaches are connected by the pseudo-gauge transformation, which we explicitly define.
↳ hep-phnucl-thPRC(2018)·138 citations
06
A neutrinoless double beta decay master formula from effective field theory
V. Cirigliano🇺🇸 · W. Dekens🇺🇸 · J. de Vries🇳🇱 · M. L. Graesser🇺🇸 · E. Mereghetti🇺🇸
We present a master formula describing the neutrinoless-double-beta decay ( $0 ν β β$ ) rate induced by lepton-number-violating (LNV) operators up to dimension nine in the Standard Model Effective Field Theory. We provide an end-to-end framework connecting the possibly very high LNV scale to the nuclear scale, through a chain of effective field theories. Starting at the electroweak scale, we integrate out the heavy Standard Model degrees of freedom and we match to an $S U (3)_{c} \otimes U (1)_{em}$ effective theory. After evolving the resulting effective Lagrangian to the QCD scale, we use chiral perturbation theory to derive the lepton-number-violating chiral Lagrangian. The chiral Lagrangian is used to derive the two-nucleon $0 ν β β$ transition operators to leading order in the chiral power counting. Based on renormalization arguments we show that in various cases short-range two-nucleon operators need to be enhanced to leading order. We show that all required nuclear matrix elements can be taken from existing calculations. Our final result is a master formula that describes the $0 ν β β$ rate in terms of phase-space factors, nuclear matrix elements, hadronic low-energy constants, QCD evolution factors, and high-energy LNV Wilson coefficients, including all the interference terms. Our master formula can be easily matched to any model where LNV originates at energy scales above the electroweak scale. As an explicit example, we match our formula to the minimal left-right-symmetric model in which contributions of operators of different dimension compete, and we discuss the resulting phenomenology.
↳ hep-phnucl-exnucl-thJHEP(2018)·187 citations

Affiliations

first authorsco-authorsvia INSPIRE

Threshold corrections of χc​(2P) and χb​(3P) states and J/ψρ and J/ψω transitions of the X(3872) in a coupled-channel model

Thermodynamic versus kinetic approach to polarization-vorticity coupling

A neutrinoless double beta decay master formula from effective field theory

Affiliations

Threshold corrections of $χ_{c} (2 P)$ and $χ_{b} (3 P)$ states and $J / ψ ρ$ and $J / ψ ω$ transitions of the $X (3872)$ in a coupled-channel model