Nuclear Theory·nucl-th

Thursday·September 15, 2016

7 papers—3 primary·4 cross-listed

01
Study of X(5568) in a unitary coupled-channel approximation of $B K ˉ$ and $B_{s} π$
Bao-Xi Sun🇨🇳 · Fang-Yong Dong🇨🇳 · Jing-Long Pang🇨🇳
The potential of the $B$ meson and the pseudoscalar meson is constructed up to the next-to-leading order Lagrangian, and then the $B K ˉ$ and $B_{s} π$ interaction is studied in the unitary coupled-channel approximation, and a resonant state with a mass about $5568 M e V$ and $J^{P} = 0^{+}$ is generated dynamically, which can be associated with the $X (5568)$ state announced by D0 Collaboration recently. The mass and the decay width of this resonant state depend on the regularization scale in the dimensional regularization scheme, or the maximum momentum in the momentum cutoff regularization scheme. The scattering amplitude of the vector $B$ meson and the pseudoscalar meson is calculated, and an axial-vector state with a mass near $5620 M e V$ and $J^{P} = 1^{+}$ is produced. Moreover, their partners in the charm sector are also discussed.
nucl-thCPC(2017)·15 citations
02
A microscopic cranking model for nuclear collective rotation I: rigid-plus-irrotational-flow rotating frame
Parviz Gulshani
We derive in a simple manner and from first principles the Inglis semi-classical phenomenological cranking model for nuclear collective rotation. The derivation transforms the nuclear Schrodinger equation (instead of the Hamiltonian) to a rotating frame using a product wavefunction and imposing no constraints on either the wavefunction or the nucleon motion. The difference from Inglis model is that the frame rotation is driven by the motions of the nucleons and not externally. Consequently, the transformed Schrodinger equation is time-reversal invariant, and the total angular momentum is the sum of those of the intrinsic system and rotating frame. In this article, we choose the rotation of the frame to be given by a combination of rigid and irrotational flows. The dynamic angular velocity of the rotating frame is determined by the angular momentum of the frame and by a moment of inertia that is determined by the nature of the flow combination. The intrinsic-system and rotating-frame angular momenta emerge to have opposite signs. The angular momentum of the rotating frame is determined from requiring the expectation of the total angular momentum to have a given value. The transformed Schrodinger equation has, in addition to the Coriolis energy term, a rigid-flow type kinetic energy term that is absent from the conventional cranking model Schrodinger equation. Ignoring the relatively small effect of the fluctuations in the angular velocity and for a self-consistent deformed harmonic oscillator mean-field potential, the resulting Schrodinger equation is solved for the ground-state rotational band excitation energy and quadrupole moment in different configurations of Ne-20 and the results are compared with those of the conventional cranking model and empirical data.
nucl-th2 citations
03
Effect of magnetic field on the photon radiation from quark-gluon plasma in heavy ion collisions
B.G. Zakharov🇷🇺
We develop a formalism for the photon emission from the quark-gluon plasma with an external electromagnetic field. We then use it to investigate the effect of magnetic field on the photon emission from the quark-gluon plasma created in $AA$ collisions. We find that even for very optimistic assumption on the magnitude of the magnetic field generated in $AA$ collisions its effect on the photon emission rate is practically negligible. For this reason the magnetic field cannot generate a significant azimuthal asymmetry in the photon spectrum.
nucl-thhep-phEPJC(2016)·38 citations
04
The Analytic Structure of Non-Global Logarithms: Convergence of the Dressed Gluon Expansion
Andrew J. Larkoski🇺🇸 · Ian Moult🇺🇸 · Duff Neill🇺🇸
Non-global logarithms (NGLs) are the leading manifestation of correlations between distinct phase space regions in QCD and gauge theories and have proven a challenge to understand using traditional resummation techniques. Recently, the dressed gluon expansion was introduced that enables an expansion of the NGL series in terms of a "dressed gluon" building block, defined by an all-orders factorization theorem. Here, we clarify the nature of the dressed gluon expansion, and prove that it has an infinite radius of convergence as a solution to the leading logarithmic and large- $N_{c}$ master equation for NGLs, the Banfi-Marchesini-Smye (BMS) equation. The dressed gluon expansion therefore provides an expansion of the NGL series that can be truncated at any order, with reliable uncertainty estimates. In contrast, manifest in the results of the fixed-order expansion of the BMS equation up to 12-loops is a breakdown of convergence at a finite value of $α_{s}$ log. We explain this finite radius of convergence using the dressed gluon expansion, showing how the dynamics of the buffer region, a region of phase space near the boundary of the jet that was identified in early studies of NGLs, leads to large contributions to the fixed order expansion. We also use the dressed gluon expansion to discuss the convergence of the next-to-leading NGL series, and the role of collinear logarithms that appear at this order. Finally, we show how an understanding of the analytic behavior obtained from the dressed gluon expansion allows us to improve the fixed order NGL series using conformal transformations to extend the domain of analyticity. This allows us to calculate the NGL distribution for all values of $α_{s}$ log from the coefficients of the fixed order expansion.
↳ hep-phhep-thnucl-thJHEP(2016)·49 citations
05
On high-order perturbative calculations at finite density
Ioan Ghisoiu🇫🇮 · Tyler Gorda🇫🇮 · Aleksi Kurkela🇨🇭 · Paul Romatschke🇺🇸 · Matias Säppi🇫🇮 · Aleksi Vuorinen🇫🇮
We discuss the prospects of performing high-order perturbative calculations in systems characterized by a vanishing temperature but finite density. In particular, we show that the determination of generic Feynman integrals containing fermionic chemical potentials can be reduced to the evaluation of three-dimensional phase space integrals over vacuum on-shell amplitudes - a result reminiscent of a previously proposed "naive real-time formalism" for vacuum diagrams. Applications of these rules are discussed in the context of the thermodynamics of cold and dense QCD, where it is argued that they facilitate an extension of the Equation of State of cold quark matter to higher perturbative orders.
↳ hep-phnucl-thNPB(2017)·34 citations
06
Hadronic structure of the photon at small x in holographic QCD
Akira Watanabe🇹🇼 · Hsiang-nan Li🇹🇼
We present our analysis on the photon structure functions at small Bjorken variable x in the framework of the holographic QCD. In the kinematic region, a photon can fluctuate into vector mesons and behaves like a hadron rather than a pointlike particle. Assuming the Pomeron exchange dominance, the dominant hadronic contribution to the structure functions is computed by convoluting the probe and target photon density distributions obtained from the wave functions of the U(1) vector field in the five-dimensional AdS space and the Brower-Polchinski-Strassler-Tan Pomeron exchange kernel. Our calculations are in agreement with both the experimental data from OPAL collaboration at LEP and those calculated from the parton distribution functions of the photon proposed by Glück, Reya, and Schienbein. The predictions presented here will be tested at future linear colliders, such as the planned International Linear Collider.
↳ hep-phnucl-thEPJ Web Conf.(2016)·0 citations
07
Photoproduction of vector mesons: from ultraperipheral to semi-central heavy ion collisions
M. Klusek-Gawenda🇵🇱 · A. Szczurek🇵🇱
We discuss nuclear cross sections for $AA \to AA V$ and $AA \to AA V V$ reactions with one or two vector mesons in the final state. Our analysis is done in the impact parameter space equivalent photon approximation. This approach allows to consider the above processes taking into account distance between colliding nuclei. We consider both ultraperipheral and semi-central collisions. We are a first group which undertook a study of single $J / ψ$ photoproduction for different centrality bins. We show that one can describe new ALICE experimental data by including geometrical effects of collisions in the flux factor. Next, total and differential cross section for double-scattering mechanism in the exclusive $AA \to AA V V$ reaction in ultrarelativistic ultraperipheral heavy ion collisions is presented. In this context we consider double photoproduction and photon-photon processes. Simultaneously, we get very good agreement of our results with STAR (RHIC), CMS and ALICE (LHC) experimental data for single $ρ^{0}$ and $J / ψ$ vector meson production. A comparison of our predictions for exclusive four charged pions production is also presented.
↳ hep-phnucl-exnucl-thEPJ Web Conf.(2016)·4 citations

Affiliations

first authorsco-authorsvia INSPIRE

Study of X(5568) in a unitary coupled-channel approximation of BKˉ and Bs​π

A microscopic cranking model for nuclear collective rotation I: rigid-plus-irrotational-flow rotating frame

Effect of magnetic field on the photon radiation from quark-gluon plasma in heavy ion collisions

The Analytic Structure of Non-Global Logarithms: Convergence of the Dressed Gluon Expansion

On high-order perturbative calculations at finite density

Hadronic structure of the photon at small x in holographic QCD

Photoproduction of vector mesons: from ultraperipheral to semi-central heavy ion collisions

Affiliations

Study of X(5568) in a unitary coupled-channel approximation of $B K ˉ$ and $B_{s} π$