Nuclear Theory·nucl-th

Wednesday·August 19, 2020

9 papers—4 primary·5 cross-listed

05
TMD factorization for dijet and heavy-meson pair in DIS
Rafael F. del Castillo🇪🇸 · Miguel G. Echevarria🇪🇸 · Yiannis Makris🇮🇹 · Ignazio Scimemi🇪🇸
We study a transverse momentum dependent (TMD) factorization framework for the processes of di-jet and heavy meson pair production in deep-inelastic-scattering in an electron-proton collider, considering the measurement of the transverse momentum imbalance of the two hard probes in the Breit frame. For the factorization theorem we employ soft-collinear and boosted-heavy-quark effective field theories. The factorized cross-section for both processes is sensitive to gluon unpolarized and linearly polarized TMD distributions and requires the introduction of a new soft function. We calculate the new soft function here at one loop, regulating rapidity divergences with the $δ$ -regulator. In addition, using a factorization consistency relation and a universality argument regarding the heavy-quark jet function, we obtain the anomalous dimension of the new soft function at two loops.
↳ hep-phnucl-exnucl-thJHEP(2021)·48 citations
06
Impressions of the Continuum Bound State Problem in QCD
Si-Xue Qin🇨🇳 · Craig D. Roberts🇨🇳
Modern and anticipated facilities will deliver data that promises to reveal the innermost workings of quantum chromodynamics (QCD). In order to fulfill that promise, phenomenology and theory must reach a new level, limiting and overcoming model-dependence, so that clean lines can be drawn that connect the data with QCD itself. Progress in that direction, made using continuum methods for the hadron bound-state problem, is sketched herein.
↳ hep-phhep-exhep-latnucl-ex+1Chin.Phys.Lett.(2020)·77 citations
07
Diquark Correlations in Hadron Physics: Origin, Impact and Evidence
M. Yu. Barabanov🇷🇺 · M. A. Bedolla🇲🇽 · W. K. Brooks🇨🇱 · G. D. Cates🇺🇸 · C. Chen🇩🇪 · Y. Chen🇨🇳 · E. Cisbani🇮🇹 · M. Ding🇮🇹 · G. Eichmann🇵🇹 · R. Ent🇺🇸 · J. Ferretti🇫🇮 · R. W. Gothe🇺🇸 and 15 other authors
The last decade has seen a marked shift in how the internal structure of hadrons is understood. Modern experimental facilities, new theoretical techniques for the continuum bound-state problem and progress with lattice-regularised QCD have provided strong indications that soft quark+quark (diquark) correlations play a crucial role in hadron physics. For example, theory indicates that the appearance of such correlations is a necessary consequence of dynamical chiral symmetry breaking, viz. a corollary of emergent hadronic mass that is responsible for almost all visible mass in the universe; experiment has uncovered signals for such correlations in the flavour-separation of the proton's electromagnetic form factors; and phenomenology suggests that diquark correlations might be critical to the formation of exotic tetra- and penta-quark hadrons. A broad spectrum of such information is evaluated herein, with a view to consolidating the facts and therefrom moving toward a coherent, unified picture of hadron structure and the role that diquark correlations might play.
↳ hep-phhep-exhep-latnucl-ex+1PPNP(2021)·187 citations
08
Analytical and numerical expressions for the number of atomic configurations contained in a supershell
Jean-Christophe Pain🇫🇷 · Michel Poirier🇫🇷
We present three explicit formulas for the number of electronic configurations in an atom, i.e. the number of ways to distribute $Q$ electrons in $N$ subshells of respective degeneracies $g_{1}$ , $g_{2}$ , ..., $g_{N}$ . The new expressions are obtained using the generating-function formalism. The first one contains sums involving multinomial coefficients. The second one relies on the idea of gathering subshells having the same degeneracy. A third one also collects subshells with the same degeneracy and leads to the definition of a two-variable generating function, allowing the derivation of recursion relations. Concerning the distribution of population on $N$ distinct subshells of a given degeneracy $g$ , analytical expressions for the first moments of this distribution are given. The general case of subshells with any degeneracy is analyzed through the computation of cumulants. A fairly simple expression for the cumulants at any order is provided, as well as the cumulant generating function. Using Gram-Charlier expansion, simple approximations of the analyzed distribution in terms of a normal distribution multiplied by a sum of Hermite polynomials are given. The Edgeworth expansion has also been tested. Its accuracy is equivalent to the Gram-Charlier accuracy when few terms are kept, but it is much more rapidly divergent when the truncation order increases. While this analysis is illustrated by examples in atomic supershells it also applies to more general combinatorial problems such as fermion distributions.
↳ physics.atom-phmath-phmath.MPnucl-th+1J.Phys.B(2020)·0 citations
09
Two-pole structures in a relativistic Friedrichs-Lee-QPC scheme
Zhi-Yong Zhou🇨🇳 · Zhiguang Xiao🇨🇳
A general appearance of two-pole structures is exhibited in a relativistic Friedrichs-Lee model combined with a relativistic quark pair creation model in a consistent manner. This kind of two-pole structure could be found when a $q q ˉ$ state couples to the open-flavor continuum state in the $S$ partial wave. We found that many enigmatic states, such as $f_{0} (500) / σ$ , $K_{0}^{*} (700) / κ$ , $a_{0} (980)$ , $f_{0} (980)$ , $D_{0}^{*} (2300)$ , $D_{s 0}^{*} (2317)$ , and $X (3872)$ , together with another higher state for each, all result from this kind of two-pole structures. Furthermore, an interesting observation is that this kind of two-pole structure will contribute roughly a total of 180 $^{\circ}$ phase shift for the scattering process in a single channel approximation. This relativistic scheme may provide more insights into the understanding of the properties of non- $q q ˉ$ state. It is also suggested that such two-pole structure could be a common phenomenon which deserves studying both from theoretical and experimental perspectives.
↳ hep-phhep-exhep-latnucl-ex+1EPJC(2021)·23 citations

Affiliations

first authorsco-authorsvia INSPIRE

TMD factorization for dijet and heavy-meson pair in DIS

Impressions of the Continuum Bound State Problem in QCD

Diquark Correlations in Hadron Physics: Origin, Impact and Evidence

Analytical and numerical expressions for the number of atomic configurations contained in a supershell

Two-pole structures in a relativistic Friedrichs-Lee-QPC scheme

Affiliations