Nuclear Theory·nucl-th

Monday·February 8, 2021

6 papers—2 primary·4 cross-listed

03
[Submitted on 4 Feb 2021] (cross-list from hep-ph)
The Fermi constant from muon decay versus electroweak fits and CKM unitarity
Andreas Crivellin🇨🇭 · Martin Hoferichter🇨🇭 · Claudio Andrea Manzari🇨🇭
The Fermi constant ( $G_{F}$ ) is extremely well measured through the muon lifetime, defining one of the key fundamental parameters in the Standard Model (SM). Therefore, to search for physics beyond the SM (BSM) via $G_{F}$ , the constraining power is determined by the precision of the second-best independent determination of $G_{F}$ . The best alternative extractions of $G_{F}$ proceed either via the global electroweak (EW) fit or from superallowed $β$ decays in combination with the Cabibbo angle measured in kaon, $τ$ , or $D$ decays. Both variants display some tension with $G_{F}$ from muon decay, albeit in opposite directions, reflecting the known tensions within the EW fit and hints for the apparent violation of CKM unitarity, respectively. We investigate how BSM physics could bring the three determinations of $G_{F}$ into agreement using SM effective field theory and comment on future perspectives.
Comments:
7 pages, 2 figures; journal version
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2102.02825 [pdf]
PRL(2021)·77 citations
04
[Submitted on 4 Feb 2021] (cross-list from hep-ph)
Hot QCD at finite isospin density: confronting SU(3) Nambu-Jona-Lasinio model with recent lattice data
Bruno. S. Lopes🇧🇷 · Sidney S. Avancini🇧🇷 · Aritra Bandyopadhyay🇨🇳 · Dyana C. Duarte🇺🇸 · Ricardo L. S. Farias🇧🇷
Extending our recently published $S U (2)$ results for zero temperature we now compute the QCD equation of state for finite isospin density within the three flavor Nambu-Jona-Lasinio model in the mean field approximation, motivated by the recently obtained Lattice QCD results for both zero and finite temperatures. Like our previous study, here also we have considered both the commonly used Traditional cutoff Regularization Scheme and the Medium Separation Scheme. Our results are compared with recent high-precision lattice simulations as well as previously obtained results in two-flavor Nambu-Jona-Lasinio model. The agreement between the lattice results and the predictions from three-flavor NJL model is very good for low values of $μ_{I}$ (for both zero and finite temperatures). For larger values of $μ_{I}$ , the agreement between lattice data and the two-flavor NJL predictions is surprisingly good and better than with the three-flavor predictions.
Comments:
13 pages, 10 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2102.02844 [pdf]
PRD(2021)·31 citations
05
[Submitted on 4 Feb 2021] (cross-list from hep-ph)
On the interpretation of $Λ$ spin polarization measurements
Wojciech Florkowski🇵🇱 · Radoslaw Ryblewski🇵🇱
The physics interpretation of the recent measurements of the spin polarization of $Λ$ hyperons produced in relativistic heavy-ion collisions is discussed. We suggest that the polarization measured in the $Λ$ rest frame should be projected along the direction of the total angular momentum that is first transformed to the same frame, and only then averaged over $Λ$ 's with different momenta in the center-of-mass frame. While this procedure does not affect the current measurements done in a broad transverse-momentum range, it may become important (represent a correction of about 10\%) for the most energetic hyperons under study (with transverse momenta reaching 4-5 GeV/c). The proposed treatment is generally more appropriate for relativistic $Λ$ 's. Throughout the paper, we deliver explicit expressions for various boosts, rotations, and transformations of angular distributions, which may help to compare model predictions with the experimental results.
Comments:
26 pages, 6 figures; Figures 3 and 4 corrected. Section VI extended. Other minor corrections introduced
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2102.02890 [pdf]
PRC(2022)·18 citations
06
[Submitted on 5 Feb 2021] (cross-list from hep-lat)
Extracting the low-energy constant $L_{0}^{r}$ at three flavors from pion-kaon scattering
Chaitra Kalmahalli Guruswamy🇩🇪 · Ulf-G. Meißner🇩🇪 · Chien-Yeah Seng🇩🇪
Based on our analysis of the contributions from the connected and disconnected contraction diagrams to the pion-kaon scattering amplitude, we provide the first determination of the only free low-energy constant at $O (p^{4})$ , known as $L_{0}^{r}$ , in SU $(4∣1)$ Partially-Quenched Chiral Perturbation Theory using the data from the Extended Twisted Mass Collaboration, $L_{0}^{r} (μ = M_{ρ}) = 0.77 (20) (25) (7) (7) (2) \cdot 1 0^{- 3}$ . The theory uncertainties originate from the unphysical scattering length, the physical low-energy constants, the higher-oder chiral corrections, the (lattice) meson masses and the pion decay constant, respectively
Comments:
6 pages, 1 figure, more details, improved uncertainty analysis
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2102.03059 [pdf]
Commun.Theor.Phys.(2022)·1 citation

Affiliations

first authorsco-authorsvia INSPIRE

The Fermi constant from muon decay versus electroweak fits and CKM unitarity

Hot QCD at finite isospin density: confronting SU(3) Nambu-Jona-Lasinio model with recent lattice data

On the interpretation of Λ spin polarization measurements

Extracting the low-energy constant L0r​ at three flavors from pion-kaon scattering

Affiliations

On the interpretation of $Λ$ spin polarization measurements

Extracting the low-energy constant $L_{0}^{r}$ at three flavors from pion-kaon scattering