Nuclear Theory·nucl-th

Monday·September 6, 2021

8 papers—4 primary·4 cross-listed

05
[Submitted on 2 Sept 2021] (cross-list from hep-ph)
Bayesian Monte Carlo extraction of sea asymmetry with SeaQuest and STAR data
C. Cocuzza🇺🇸 · W. Melnitchouk🇺🇸 · A. Metz🇺🇸 · N. Sato🇺🇸
We perform a global QCD analysis of unpolarized parton distributions within a Bayesian Monte Carlo framework, including the new $W$ -lepton production data from the STAR Collaboration at RHIC and Drell-Yan di-muon data from the SeaQuest experiment at Fermilab. We assess the impact of these two new measurements on the light antiquark sea in the proton, and the $d ˉ - u ˉ$ asymmetry in particular. The SeaQuest data are found to significantly reduce the uncertainty on the $d ˉ / u ˉ$ ratio at large parton momentum fractions $x$ , strongly favoring an enhanced $d ˉ$ sea up to $x \approx 0.4$ , in general agreement with nonperturbative calculations based on chiral symmetry breaking in QCD.
Comments:
10 pages, 8 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
2109.00677 [pdf]
PRD(2021)·50 citations
06
[Submitted on 3 Sept 2021] (cross-list from hep-ph)
Revisit the isospin violating decays of $X (3872)$
Lu Meng🇩🇪 · Guang-Juan Wang🇯🇵 · Bo Wang🇨🇳 · Shi-Lin Zhu🇨🇳
In this work, we revisit the isospin violating decays of $X (3872)$ in a coupled-channel effective field theory. In the molecular scheme, the $X (3872)$ is interpreted as the bound state of $D ˉ^{* 0} D^{0} / D ˉ^{0} D^{* 0}$ and $D^{*-} D^{+} / D^{-} D^{*+}$ channels. In a cutoff-independent formalism, we relate the coupling constants of $X (3872)$ with the two channels to the molecular wave function. The isospin violating decays of $X (3872)$ are obtained by two equivalent approaches, which amend some deficiencies about this issue in literature. In the quantum field theory approach, the isospin violating decays arise from the coupling constants of $X (3872)$ to two di-meson channels. In the quantum mechanics approach, the isospin violating is attributed to wave functions at the origin. We illustrate that how to cure the insufficient results in literature. Within the comprehensive analysis, we bridge the isospin violating decays of $X (3872)$ to its inner structure. Our results show that the proportion of the neutral channel in $X (3872)$ is over $80%$ . As a by-product, we calculate the strong decay width of $X (3872) \to D ˉ^{0} D^{0} π^{0}$ and radiative one $X (3872) \to D ˉ^{0} D^{0} γ$ . The strong decay width and radiative decay width are about 30 keV and 10 keV, respectively, for the binding energy from $- 300$ keV to $- 50$ keV.
Comments:
8 pages, 4 figures. Accepted version by Physical Review D
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
2109.01333 [pdf]
PRD(2021)·36 citations
07
[Submitted on 3 Sept 2021] (cross-list from hep-ph)
The QCD Equation of State in Small Systems
W. A. Horowitz🇿🇦 · Alexander Rothkopf🇳🇴
We present first results on finite system size corrections to the equation of state, trace anomaly, and speed of sound for two model systems: 1) free, massless scalar theory and 2) quenched QCD with periodic boundary conditions (PBC). We further present work-in-progress results for quenched QCD with Dirichlet boundary conditions.
Comments:
Proceedings for the 50th International Symposium on Multiparticle Dynamics (ISMD2021). 4 pages, 2 figures. Minor revisions from first version
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
2109.01422 [pdf]
SciPost Phys.Proc.(2022)·12 citations
08
[Submitted on 3 Sept 2021] (cross-list from hep-ph)
Do Minimal Parity Solutions to the Strong CP Problem Work?
Jordy de Vries🇳🇱 · Patrick Draper🇺🇸 · Hiren H. Patel🇺🇸
One class of solutions to the strong CP problem relies on generalized parity symmetries. A minimal model of this type, constructed by Babu and Mohapatra and based on a softly broken parity symmetry, has the remarkable property that effective QCD vacuum angle $θ ˉ$ vanishes up to one-loop order. We compute the leading two-loop contributions to $θ ˉ$ in this model and estimate subleading contributions. In contrast to previous estimates, we argue that $θ ˉ$ is not suppressed by the weak scale, and we find contributions of order $1 0^{- 3}$ - $1 0^{- 2}$ multiplying unknown mixing angles and phases. Thus the model does not generically address the strong CP problem, but it might be made consistent with $θ ˉ < 1 0^{- 10}$ in some corners of parameter space. For such non-generic parameters, $θ ˉ$ is still likely to be just below present bounds, and therefore provides the dominant source of hadronic EDMs. We discuss the resulting EDM phenomenology.
Comments:
8 pages, 1 figure
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2109.01630 [pdf]
39 citations

Affiliations

first authorsco-authorsvia INSPIRE

Bayesian Monte Carlo extraction of sea asymmetry with SeaQuest and STAR data

Revisit the isospin violating decays of X(3872)

The QCD Equation of State in Small Systems

Do Minimal Parity Solutions to the Strong CP Problem Work?

Affiliations

Revisit the isospin violating decays of $X (3872)$