Nuclear Theory·nucl-th

Wednesday·October 30, 2019

15 papers—7 primary·8 cross-listed

08
Grand Unified Neutrino Spectrum at Earth: Sources and Spectral Components
Edoardo Vitagliano🇩🇪 · Irene Tamborra🇩🇰 · Georg Raffelt🇩🇪
We briefly review the dominant neutrino fluxes at Earth from different sources and present the Grand Unified Neutrino Spectrum ranging from meV to PeV energies. For each energy band and source, we discuss both theoretical expectations and experimental data. This compact review should be useful as a brief reference to those interested in neutrino astronomy, fundamental particle physics, dark-matter detection, high-energy astrophysics, geophysics, and other related topics.
↳ astro-ph.HEhep-exhep-phnucl-thRMP(2020)·280 citations
09
Superallowed $0^{+} \to 0^{+}$ $β$ decay of $T = 2$ $^{20}$ Mg: $Q_{EC}$ value and $β γ$ branching
B. E. Glassman (Department of Physics and Astronomy and National Superconducting Cyclotron Laboratory, Michigan State University)🇺🇸 · D. Pérez-Loureiro (National Superconducting Cyclotron Laboratory, Michigan State University)🇺🇸 · C. Wrede (Department of Physics and Astronomy and National Superconducting Cyclotron Laboratory, Michigan State University)🇺🇸 · J. M. Allen (Department of Physics, University of Notre Dame)🇺🇸 · D. W. Bardayan (Department of Physics, University of Notre Dame)🇺🇸 · M. B. Bennett (Department of Physics and Astronomy and National Superconducting Cyclotron Laboratory, Michigan State University)🇺🇸 · B. A. Brown (Department of Physics and Astronomy and National Superconducting Cyclotron Laboratory, Michigan State University)🇺🇸 · K. A. Chipps (Oak Ridge National Laboratory and Department of Physics and Astronomy, University of Tennesssee)🇺🇸 · M. Febbraro (Oak Ridge National Laboratory and Department of Physics and Astronomy, University of Tennesssee)🇺🇸 · C. Fry (Department of Physics and Astronomy and National Superconducting Cyclotron Laboratory, Michigan State University)🇺🇸 · M. R. Hall (Department of Physics, University of Notre Dame and Oak Ridge National Laboratory)🇺🇸 · O. Hall (Department of Physics, University of Notre Dame)🇺🇸 and 9 other authors
\textbf{Background}: Superallowed $0^{+} \to 0^{+}$ $β$ decays of isospin $T = 2$ nuclides can be used to test theoretical isospin symmetry breaking corrections applied to extract the CKM matrix element $V_{u d}$ from $T = 0, 1$ decays by measuring precise $f t$ values and also to search for scalar currents using the $β - ν$ angular correlation. Key ingredients include the $Q_{EC}$ value and branching of the superallowed transition and the half life of the parent. \textbf{Purpose}: To determine a precise experimental $Q_{EC}$ value for the superallowed $0^{+} \to 0^{+}$ $β$ decay of $T = 2$ $^{20}$ Mg and the intensity of $^{20}$ Mg $β$ -delayed $γ$ rays through the isobaric analog state in $^{20}$ Na. \textbf{Method}: A beam of $^{20}$ Mg was produced using the in-flight method and implanted into a plastic scintillator surrounded by an array of high-purity germanium detectors used to detect $β$ -delayed $γ$ rays. The high-resolution $γ$ -ray spectrum was analyzed to measure the $γ$ -ray energies and intensities. \textbf{Results}: The intensity of $^{20}$ Mg $β$ -delayed $γ$ rays through the isobaric analog state in $^{20}$ Na was measured to be $(1.60 \pm 0.0 4_{stat} \pm 0.1 5_{syst} \pm 0.1 5_{theo}) \times 1 0^{- 4}$ , where the uncertainties are statistical, systematic, and theoretical, respectively. The $Q_{EC}$ value for the superallowed transition was determined to be $4128.7 \pm 2.2$ keV based on the measured excitation energy of $6498.4 \pm 0. 2_{stat} \pm 0. 4_{syst}$ keV and literature values for the ground-state masses of $^{20}$ Na and $^{20}$ Mg. \textbf{Conclusions}: The $β$ -delayed $γ$ -decay branch and $Q_{EC}$ value are now sufficiently precise to match or exceed the sensitivity required for current low-energy tests of the standard model.
↳ nucl-exhep-exnucl-th0 citations
10
Saturation and forward jets in proton-lead collisions at the LHC
Heikki Mäntysaari🇫🇮 · Hannu Paukkunen🇫🇮
We investigate the forward-jet energy spectrum within the Color Glass Condensate framework at 5 TeV center-of-mass energy. In particular, we focus on the kinematic range covered by the CMS-CASTOR calorimeter. We show that our saturation-model calculations are compatible with the CASTOR measurements and that to optimally reproduce the data, effects of multi-parton interactions need to be included. We predict a significant nuclear suppression - reaching down to 50% at the lowest considered jet energies $E_{jet} \sim 500 GeV$ .
↳ hep-phnucl-thPRD(2019)·22 citations
11
A New Theory Framework for the Electroweak Radiative Corrections in $K_{l 3}$ Decays
Chien-Yeah Seng🇩🇪 · Daniel Galviz🇩🇪 · Ulf-G. Meißner🇩🇪
We propose a new theory framework to study the electroweak radiative corrections in $K_{l 3}$ decays by combining the classic current algebra approach with the modern effective field theory. Under this framework, the most important $O (G_{F} α)$ radiative corrections are described by a single tensor $T^{μν}$ involving the time-ordered product between the charged weak current and the electromagnetic current, and all remaining pieces are calculable order-by-order in Chiral Perturbation Theory. We further point out a special advantage in the $K_{l 3}^{0}$ channel that it suffers the least impact from the poorly-constrained low-energy constants. This finding may serve as a basis for a more precise extraction of the matrix element $V_{u s}$ in the future.
↳ hep-phhep-exnucl-exnucl-thJHEP(2020)·37 citations
12
New evaluation of axial nucleon form factor from electron- and neutrino-scattering data and impact on neutrino-nucleus cross-section
G. D. Megias🇯🇵 · S. Bolognesi🇫🇷 · M. B. Barbaro🇮🇹 · E. Tomasi-Gustafsson🇫🇷
A joint fit to neutrino-nucleon scattering and pion electroproduction data is performed to evaluate the nucleon axial form factor in the two-component model consisting of a three-quark intrinsic structure surrounded by a meson cloud. Further constrains on the model are obtained by re-evaluating the electromagnetic form factor using electron scattering data. The results of the axial form factor show sizable differences with respect to the widely used dipole model. The impact of such changes on the Charged-Current Quasi-Elastic neutrino-nucleus cross-section is evaluated in the SuSAv2 nuclear model, based on the Relativistic Mean Field and including the contribution of two-body currents. How the different parametrizations of the axial form factor affect the cross-section prediction is assessed in full details and comparisons to recent T2K and MINERvA data are presented.
↳ hep-phhep-exnucl-thPRC(2020)·23 citations
13
Viscosity, non-conformal equation of state and sound velocity in Landau hydrodynamics
Deeptak Biswas🇮🇳 · Kishan Deka🇮🇳 · Amaresh Jaiswal🇮🇳 · Sutanu Roy🇮🇳
We find an analytical solution to relativistic viscous hydrodynamics for a 1+1 dimensional Landau flow profile. We consider relativistic Navier-Stokes form of the dissipative hydrodynamic equation, for a non-conformal system with a constant speed of sound, and employ the obtained solution to fit rapidity spectrum of observed pions in $s_{N N} =$ 200, 17.3, 12.3, 8.76, 7.62, 6.27, 4.29, 3.83, 3.28 and 2.63 GeV collision energies. We find that at the freeze-out hypersurface with improved Landau's freeze-out prescription, the viscous corrections do not affect the rapidity spectra. We demonstrate that the solution of the non-conformal Landau flow lead to a better agreement with the experimental data compared to the conformal ideal solution. We also extract speed of sound from fit to the rapidity spectra for various collision energies and find a monotonous decrease with decreasing collision energies. Appealing to the fact that viscosity has negligible effect on rapidity spectra for Landau's freeze-out scenario, we argue that our calculations provides a framework for extracting the average value of speed of sound in relativistic heavy-ion collisions.
↳ hep-phhep-thnucl-thPRC(2020)·18 citations
14
Spectroscopy, lifetime and decay modes of the $T_{bb}^{-}$ tetraquark
E. Hernández🇪🇸 · J. Vijande🇪🇸 · A. Valcarce🇪🇸 · Jean-Marc Richard🇫🇷
We present the first full-fledged study of the flavor-exotic isoscalar $T_{bb}^{-} \equiv bb u ˉ d ˉ$ tetraquark with spin and parity $J^{P} = 1^{+}$ . We report accurate solutions of the four-body problem in a quark model, characterizing the structure of the state as a function of the ratio $M_{Q} / m_{q}$ of the heavy to light quark masses. For such a standard constituent model, $T_{bb}^{-}$ lies approximately 150 MeV below the strong decay threshold $B^{-} B^{*} ˉ^{0}$ and 105 MeV below the electromagnetic decay threshold $B^{-} B ˉ^{0} γ$ . We evaluate the lifetime of $T_{bb}^{-}$ , identifying the promising decay modes where the tetraquark might be looked for in future experiments. Its total decay width is $Γ \approx 87 \times 1 0^{- 15}$ GeV and therefore its lifetime $τ \approx$ 7.6 ps. The promising final states are $B^{*}^{-} D^{*}^{+} ℓ^{-} ν ˉ_{ℓ}$ and $B^{*} ˉ^{0} D^{*}^{0} ℓ^{-} ν ˉ_{ℓ}$ among the semileptonic decays, and $B^{*}^{-} D^{*}^{+} D_{s}^{*}^{-}$ , $B^{*} ˉ^{0} D^{*}^{0} D_{s}^{*}^{-}$ , and $B^{*}^{-} D^{*}^{+} ρ^{-}$ among the nonleptonic ones. The semileptonic decay to the isoscalar $J^{P} = 0^{+}$ tetraquark $T_{b c}^{0}$ is also relevant but it is not found to be dominant. There is a broad consensus about the existence of this tetraquark, and its detection will validate our understanding of the low-energy realizations of Quantum Chromodynamics (QCD) in the multiquark sector.
↳ hep-phhep-exnucl-thPLB(2020)·62 citations
15
Longitudinal short-distance constraints for the hadronic light-by-light contribution to $(g - 2)_{μ}$ with large- $N_{c}$ Regge models
Gilberto Colangelo🇨🇭 · Franziska Hagelstein🇨🇭 · Martin Hoferichter🇺🇸 · Laetitia Laub🇨🇭 · Peter Stoffer🇺🇸
While the low-energy part of the hadronic light-by-light (HLbL) tensor can be constrained from data using dispersion relations, for a full evaluation of its contribution to the anomalous magnetic moment of the muon $(g - 2)_{μ}$ also mixed- and high-energy regions need to be estimated. Both can be addressed within the operator product expansion (OPE), either for configurations where all photon virtualities become large or one of them remains finite. Imposing such short-distance constraints (SDCs) on the HLbL tensor is thus a major aspect of a model-independent approach towards HLbL scattering. Here, we focus on longitudinal SDCs, which concern the amplitudes containing the pseudoscalar-pole contributions from $π^{0}$ , $η$ , $η^{'}$ . Since these conditions cannot be fulfilled by a finite number of pseudoscalar poles, we consider a tower of excited pseudoscalars, constraining their masses and transition form factors from Regge theory, the OPE, and phenomenology. Implementing a matching of the resulting expressions for the HLbL tensor onto the perturbative QCD quark loop, we are able to further constrain our calculation and significantly reduce its model dependence. We find that especially for the $π^{0}$ the corresponding increase of the HLbL contribution is much smaller than previous prescriptions in the literature would imply. Overall, we estimate that longitudinal SDCs increase the HLbL contribution by $Δ a_{μ}^{LSDC} = 13 (6) \times 1 0^{- 11}$ . This number does not include the contribution from the charm quark, for which we find $a_{μ}^{c -quark} = 3 (1) \times 1 0^{- 11}$ .
↳ hep-phhep-exhep-latnucl-thJHEP(2020)·431 citations

Affiliations

first authorsco-authorsvia INSPIRE