Nuclear Theory·nucl-th

Wednesday·October 4, 2017

13 papers—8 primary·5 cross-listed

09
A fast and accurate method for perturbative resummation of transverse momentum-dependent observables
Daekyoung Kang🇺🇸 · Christopher Lee🇺🇸 · Varun Vaidya🇺🇸
We propose a novel strategy for the perturbative resummation of transverse momentum-dependent (TMD) observables, using the $q_{T}$ spectra of gauge bosons ( $γ^{*}$ , Higgs) in $pp$ collisions in the regime of low (but perturbative) transverse momentum $q_{T}$ as a specific example. First we introduce a scheme to choose the factorization scale for virtuality in momentum space instead of in impact parameter space, allowing us to avoid integrating over (or cutting off) a Landau pole in the inverse Fourier transform of the latter to the former. The factorization scale for rapidity is still chosen as a function of impact parameter $b$ , but in such a way designed to obtain a Gaussian form (in $ln b$ ) for the exponentiated rapidity evolution kernel, guaranteeing convergence of the $b$ integral. We then apply this scheme to obtain the $q_{T}$ spectra for Drell-Yan and Higgs production at NNLL accuracy. In addition, using this scheme we are able to obtain a fast semi-analytic formula for the perturbative resummed cross sections in momentum space: analytic in its dependence on all physical variables at each order of logarithmic accuracy, up to a numerical expansion for the pure mathematical Bessel function in the inverse Fourier transform that needs to be performed just once for all observables and kinematics, to any desired accuracy.
↳ hep-phnucl-thJHEP(2018)·26 citations
10
Radiative resonance couplings in $γ π \to π π$
Martin Hoferichter🇺🇸 · Bastian Kubis🇩🇪 · Marvin Zanke🇩🇪
Studies of the reaction $γ π \to π π$ , in the context of the ongoing Primakoff program of the COMPASS experiment at CERN, give access to the radiative couplings of the $ρ (770)$ and $ρ_{3} (1690)$ resonances. We provide a vector-meson-dominance estimate of the respective radiative width of the $ρ_{3}$ , $Γ_{ρ_{3} \to π γ} = 48 (18)$ keV, as well as its impact on the $F$ -wave in $γ π \to π π$ . For the $ρ (770)$ , we establish the formalism necessary to extract its radiative coupling directly from the residue of the resonance pole by analytic continuation of the $γ π \to π π$ amplitude to the second Riemann sheet, without any reference to the vector-meson-dominance hypothesis.
↳ hep-phhep-exnucl-thPRD(2017)·81 citations
11
Roper resonances and quasi-normal modes of Skyrmions
C. Adam🇪🇸 · M. Haberichter🇩🇪 · T. Romanczukiewicz🇵🇱 · A. Wereszczynski🇵🇱
Radial vibrations of charge one hedgehog Skyrmions in the full Skyrme model are analysed. We investigate how the properties of the lowest resonance modes (quasi normal modes) - their frequencies and widths - depend on the form of the potential (value of the pion mass as well as the addition of further potentials) and on the inclusion of the sextic term. Then we consider the inverse problem, where certain values for the frequencies and widths are imposed, and the field theoretic Skyrme model potential giving rise to them is reconstructed. This latter method allows to reproduce the physical Roper resonances, as well as further physical properties of nucleons, with high precision.
↳ hep-thnucl-thJHEP(2018)·11 citations
12
New results from a number operator interpretation of the compositeness of bound and resonant states
J.A. Oller🇪🇸
A novel theoretical approach to the problem of the compositeness ( $X$ ) of a resonance or bound state is developed on the basis of the expectation values of the number operators of the free particles in the continuum. This formalism is specially suitable for effective field theories in which the bare elementary states are integrated out but that give rise to resonance and bound states when implemented in nonperturbative calculations. We demonstrate that $X = 1$ for finite-range energy-independent potentials, either regular or singular. A non-trivial example for an energy-dependent potential is discussed where it is shown that $X$ is independent of any type of cutoff regulator employed. The generalization of these techniques to relativistic states is developed. We also explain how to obtain a meaningful compositeness with respect to the open channels for resonances, even if it is complex in a first turn, by making use of suitable phase-factor transformations. Defining elementariness as $X = 0$ , we derive a new universal criterion for the elementariness of a bound state. Along the same lines, a necessary condition for a resonance to be qualified as elementary is given. The application of the formalism here developed might be of considerable practical interest.
↳ hep-phhep-lathep-thnucl-thAnnals Phys.(2018)·58 citations
13
Entropy and Multifractality in Relativistic Ion-Ion Collisions
Shaista Khan🇮🇳 · Shakeel Ahmad🇮🇳
Entropy production in multiparticle systems is investigated by analysing the experimental data on ion-ion collision at AGS and SPS energies and comparing the findings with those reported earlier for hadron-hadron, hadron-nucleus and nucleus-nucleus collisions. It is observed that the entropy produced in limited and full phase space, when normalised to maximum rapidity exhibits a kind of scaling which is nicely supported by Monte Carlo model \hij. Using the Rényi's order-q information entropy, multifractal characteristics of particle production are examined in terms of Generalized dimensions, D $_{q}$ . Nearly the same values of multifractal specific heat, $c$ observed in hadronic and ion-ion collisions over a wide range of incident energies suggest that the quantity $c$ may be used as a universal characteristic of multiparticle production in hadron-hadron, hadron-nucleus and nucleus-nucleus collisions.
↳ hep-phnucl-thAdv.High Energy Phys.(2018)·4 citations

Affiliations

first authorsco-authorsvia INSPIRE

A fast and accurate method for perturbative resummation of transverse momentum-dependent observables

Radiative resonance couplings in γπ→ππ

Roper resonances and quasi-normal modes of Skyrmions

New results from a number operator interpretation of the compositeness of bound and resonant states

Entropy and Multifractality in Relativistic Ion-Ion Collisions

Affiliations

Radiative resonance couplings in $γ π \to π π$