Nuclear Theory·nucl-th

Wednesday·October 28, 2020

11 papers—7 primary·4 cross-listed

08
[Submitted on 26 Oct 2020] (cross-list from hep-ph)
Comprehensive analysis of beta decays within and beyond the Standard Model
Adam Falkowski🇫🇷 · Martín González-Alonso🇪🇸 · Oscar Naviliat-Cuncic🇫🇷
Precision measurements in allowed nuclear beta decays and neutron decay are reviewed and analyzed both within the Standard Model and looking for new physics. The analysis incorporates the most recent experimental and theoretical developments. The results are interpreted in terms of Wilson coefficients describing the effective interactions between leptons and nucleons (or quarks) that are responsible for beta decay. New global fits are performed incorporating a comprehensive list of precision measurements in neutron decay, superallowed $0^{+} \to 0^{+}$ transitions, and other nuclear decays that include, for the first time, data from mirror beta transitions. The results confirm the $V$ - $A$ character of the interaction and translate into updated values for $V_{u d}$ and $g_{A}$ at the $1 0^{- 4}$ level. We also place new stringent limits on exotic couplings involving left-handed and right-handed neutrinos, which benefit significantly from the inclusion of mirror decays in the analysis.
Comments:
35 pages; v2: analysis updated, comments and references added; v3: compared to the JHEP version, typos in Eqs. 2.1, A3, A4 corrected, Eq. 4.4 updated, comment on aCORN update added in footnote 12
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2010.13797 [pdf]
JHEP(2021)·123 citations
09
[Submitted on 26 Oct 2020] (cross-list from hep-ph)
On the stability of the open-string QED neutron and dark matter
Cheuk-Yin Wong🇺🇸
We study the stability of a hypothetical QED neutron, which consists of a color-singlet system of two $d$ quarks and a $u$ quark interacting with the QED interaction. As a quark cannot be isolated, the intrinsic motion of the three quarks in the lowest-energy state may lie predominantly in 1+1 dimensions, as in a $d$ - $u$ - $d$ open string. The attractive $d$ - $u$ and $u$ - $d$ QED interactions may overcome the weaker repulsive $d$ - $d$ QED interaction to bind the three quarks together. We examine the QED neutron in a phenomenological three-body problem in 1+1 dimensions with an effective interaction extracted from Schwinger's exact QED solution in 1+1 dimensions. The phenomenological model in a variational calculation yields a stable QED neutron at 44.5 MeV. The analogous QED proton with two $u$ quarks and a $d$ quark has been found to be too repulsive to be stable and does not have a bound or continuum state, onto which the QED neutron can decay via the weak interaction. Consequently, the QED neutron is stable against the weak decay, has a long lifetime, and is in fact a QED dark neutron. It may be produced following the deconfinement-to-confinement phase transition of the quark gluon plasma in high-energy heavy-ion collisions. Because of the long lifetime of the QED dark neutron, self-gravitating assemblies of QED dark neutrons or dark antineutrons may be good candidates for a part of the primordial dark matter produced during the phase transition of the quark gluon plasma in the evolution of the early Universe.
Comments:
26 pages, 11 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2010.13948 [pdf]
EPJA(2022)·9 citations
10
[Submitted on 27 Oct 2020] (cross-list from hep-lat)
Jet transport coefficient $q^$ in lattice QCD
Amit Kumar (Wayne State University and McGill University)🇺🇸 · Abhijit Majumder (Wayne State University)🇺🇸 · Johannes Heinrich Weber (Michigan State University and Humboldt University of Berlin)🇺🇸
We present the first calculation of the jet transport coefficient $q^$ in quenched and (2+1)-flavor QCD on a 4-D Euclidean lattice. The light-like propagation of an energetic parton is factorized from the mean square gain in momentum transverse to the direction of propagation, which is expressed in terms of the thermal field-strength field-strength correlator. The leading-twist term in its operator product expansion is calculated on the lattice. Continuum extrapolated quenched results, and full QCD estimates based on un-renormalized lattice data, over multiple lattice sizes, are compared with (non) perturbative calculations and phenomenological extractions of $q^$ . The lattice data for $q^$ show a temperature dependence similar to the entropy density. Within uncertainties, these are consistent with phenomenological extractions, contrary to calculations using perturbation theory.
Comments:
Published version. 13 pages+6 figures. Revtex4.1
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2010.14463 [pdf]
PRD(2022)·41 citations
11
[Submitted on 27 Oct 2020] (cross-list from hep-ph)
Combined Explanation of the $Z \to b b ˉ$ Forward-Backward Asymmetry, the Cabibbo Angle Anomaly, $τ \to μν ν$ and $b \to s ℓ^{+} ℓ^{-}$ Data
Andreas Crivellin🇨🇭 · Claudio Andrea Manzari🇨🇭 · Marcel Alguero🇪🇸 · Joaquim Matias🇪🇸
In this article we propose a simple model which can provide a combined explanation of the $Z \to b b ˉ$ forward-backward asymmetry, the Cabibbo Angle Anomaly (CAA), $τ \to μν ν$ and $b \to s ℓ^{+} ℓ^{-}$ data. This model is obtained by extending the Standard Model (SM) by two heavy vector-like quarks (an $S U (2)_{L}$ doublet (singlet) with hypercharge $- 5/6$ (-1/3)), two new scalars (a neutral and a singly charged one) and a gauged $L_{μ} - L_{τ}$ symmetry. The mixing of the new quarks with the SM ones, after electroweak symmetry breaking, does not only explain $Z \to b b ˉ$ data but also generates a lepton flavour universal contribution to $b \to s ℓ^{+} ℓ^{-}$ transitions. Together with the lepton flavour universality violating effect, generated by loop-induced $Z^{'}$ penguins involving the charged scalar and the heavy quarks, it gives an excellent fit to data ( $6.1 σ$ better than the SM). Furthermore, the charged scalar (neutral vector) gives a necessarily constructive tree-level (loop) effect in $μ \to e ν ν$ ( $τ \to μν ν$ ), which can naturally account for the CAA ( $Br [τ \to μν ν] / Br [τ \to e ν ν]$ and $Br [τ \to μν ν] / Br [μ \to e ν ν]$ ).
Comments:
8 pages, 2 figures, version accepted for publication in PRL
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2010.14504 [pdf]
PRL(2021)·67 citations

Affiliations

first authorsco-authorsvia INSPIRE

Comprehensive analysis of beta decays within and beyond the Standard Model

On the stability of the open-string QED neutron and dark matter

Jet transport coefficient q^​ in lattice QCD

Combined Explanation of the Z→bbˉ Forward-Backward Asymmetry, the Cabibbo Angle Anomaly, τ→μνν and b→sℓ+ℓ− Data

Affiliations

Jet transport coefficient $q^$ in lattice QCD

Combined Explanation of the $Z \to b b ˉ$ Forward-Backward Asymmetry, the Cabibbo Angle Anomaly, $τ \to μν ν$ and $b \to s ℓ^{+} ℓ^{-}$ Data