Nuclear Theory·nucl-th

Wednesday·June 7, 2023

9 papers—2 primary·7 cross-listed

03
Effective field theory for radiative corrections to charged-current processes I: Vector coupling
Vincenzo Cirigliano🇺🇸 · Wouter Dekens🇺🇸 · Emanuele Mereghetti🇺🇸 · Oleksandr Tomalak🇺🇸
We study radiative corrections to low-energy charged-current processes involving nucleons, such as neutron beta decay and (anti)neutrino-nucleon scattering within a top-down effective-field-theory approach. We first match the Standard Model to the low-energy effective theory valid below the weak scale and, using renormalization group equations with anomalous dimensions of $O (α, α α_{s}, α^{2})$ , evolve the resulting effective coupling down to the hadronic scale. Here, we first match to heavy-baryon chiral perturbation theory and subsequently, below the pion-mass scale, to a pionless effective theory, evolving the effective vector coupling with anomalous dimensions of $O (α, α^{2})$ all the way down to the scale of the electron mass, relevant for beta decays. We thus provide a new evaluation of the ``inner" radiative corrections to the vector coupling constant and to the neutron decay rate, discussing differences with the previous literature. Using our new result for the radiative corrections, we update the extraction of the Cabibbo-Kobayashi-Maskawa matrix element $V_{u d}$ from the neutron decay.
↳ hep-phhep-exhep-latnucl-ex+1PRD(2023)·71 citations
04
All-Orders Evolution of Parton Distributions: Principle, Practice, and Predictions
Pei-Lin Yin🇨🇳 · Yin-Zhen. XuID🇪🇸 · Zhu-Fang Cui🇨🇳 · Craig D. Roberts🇨🇳 · José Rodríguez-Quintero🇪🇸
Parton distribution functions (DFs) are defining expressions of hadron structure. Exploiting the role of effective charges in quantum chromodynamics, an algebraic scheme is described which, given any hadron's valence parton DFs at the hadron scale, delivers predictions for all its DFs -- unpolarised and polarised -- at any higher scale. The scheme delivers results that are largely independent of both the value of the hadron scale and the pointwise form of the charge; and, inter alia, enables derivation of a model-independent identity that relates the strength of the proton's gluon helicity DF, $Δ G_{p}^{ζ}$ , to that of the analogous singlet polarised quark DF and valence quark momentum fraction. Using available data fits and theory predictions, the identity yields $Δ G_{p} (ζ_{C} = \sqrt3 GeV) = 1.48 (10)$ . It furthermore entails that the measurable quark helicity contribution to the proton spin is $a ~_{0 p}^{ζ_{C}} = 0.32 (3)$ , thereby reconciling contemporary experiment and theory.
↳ hep-phhep-exhep-latnucl-ex+1Chin.Phys.Lett.(2023)·29 citations
05
The Gallium Anomaly
Steven R. Elliott🇺🇸 · Vladimir Gavrin🇷🇺 · Wick Haxton🇺🇸
In order to test the end-to-end operations of gallium solar neutrino experiments, intense electron-capture sources were fabricated to measure the responses of the radiochemical SAGE and GALLEX/GNO detectors to known fluxes of low-energy neutrinos. Such tests were viewed at the time as a cross-check, given the many tests of $^{71}$ Ge recovery and counting that had been routinely performed, with excellent results. However, the four $^{51}$ Cr and $^{37}$ Ar source experiments yielded rates below expectations, a result commonly known as the Ga anomaly. As the intensity of the electron-capture sources can be measured to high precision, the neutrino lines they produce are fixed by known atomic and nuclear rates, and the neutrino absorption cross section on $^{71}$ Ga is tightly constrained by the lifetime of $^{71}$ Ge, no simple explanation for the anomaly has been found. To check these calibration experiments, a dedicated experiment BEST was performed, utilizing a neutrino source of unprecedented intensity and a detector optimized to increase statistics while providing some information on counting rate as a function of distance from the source. The results BEST obtained are consistent with the earlier solar neutrino calibration experiments, and when combined with those measurements, yield a Ga anomaly with a significance of approximately $4 σ$ , under conservative assumptions. But BEST found no evidence of distance dependence and thus no explicit indication of new physics. In this review we describe the extensive campaigns carried out by SAGE, GALLEX/GNO, and BEST to demonstrate the reliability and precision of their experimental procedures, including $^{71}$ Ge recovery, counting, and analysis. We also describe efforts to define uncertainties in the neutrino capture cross section. With the results from BEST, an anomaly remains.
↳ nucl-exnucl-thPPNP(2024)·40 citations
06
Effect of a magnetic field on the thermodynamic properties of a high-temperature hadron resonance gas with van der Waals interactions
Bhagyarathi Sahoo🇮🇳 · Kshitish Kumar Pradhan🇮🇳 · Dushmanta Sahu🇮🇳 · Raghunath Sahoo🇮🇳
We study the behavior of a hadronic matter in the presence of an external magnetic field within the van der Waals hadron resonance gas model, considering both attractive and repulsive interactions among the hadrons. Various thermodynamic quantities like pressure ( $P$ ), energy density ( $ε$ ), magnetization ( $M$ ), entropy density ( $s$ ), squared speed of sound ( $c_{s}^{2}$ ), and specific-heat capacity at constant volume ( $c_{v}$ ) are calculated as functions of temperature ( $T$ ) and static finite magnetic field ( $e B$ ). We also consider the effect of baryochemical potential ( $μ_{B}$ ) on the above-mentioned thermodynamic observables in the presence of a magnetic field. Further, we estimate the magnetic susceptibility ( $χ_{M}^{2}$ ), relative permeability ( $μ_{r}$ ), and electrical susceptibility ( $χ_{Q}^{2}$ ) which can help us to understand the system better. Through this model, we quantify a liquid-gas phase transition in the T-eB- $μ_{B}$ phase space.
↳ hep-phhep-exhep-thnucl-ex+1PRD(2023)·24 citations
07
Lattice study on a tetra-quark state $T_{bb}$ in the HAL QCD method
Takafumi Aoki🇯🇵 · Sinya Aoki🇯🇵 · Takashi Inoue🇯🇵
We study a doubly-bottomed tetra-quark state $(bb u ˉ d ˉ)$ with quantum number $I (J^{P}) = 0 (1^{+})$ , denoted by $T_{bb}$ , in lattice QCD with the Non-Relativistic QCD (NRQCD) quark action for $b$ quarks. Employing $(2 + 1)$ -flavor gauge configurations at $a \approx 0.09$ {fm} on $3 2^{3} \times 64$ lattices, we have extracted the coupled channel potential between $B ˉ B ˉ^{*}$ and $B ˉ^{*} B ˉ^{*}$ in the HAL QCD method, which predicts an existence of a bound $T_{bb}$ below the $B ˉ B ˉ^{*}$ threshold. By extrapolating results at $m_{π} \approx 410, 570, 700$ {MeV} to the physical pion mass $m_{π} \approx 140$ {MeV}, we obtain a biding energy with its statistical error as $E_{binding}^{(single)} = 155 (17)$ MeV and $E_{binding}^{(coupled)} = 83 (10)$ MeV, where ``coupled" means that effects due to virtual $B ˉ^{*} B ˉ^{*}$ states are included through the coupled channel potential, while only a potential for a single $B ˉ B ˉ^{*}$ channel is used in the analysis for ``single". A comparison shows that the effect from virtual $B ˉ^{*} B ˉ^{*}$ states is quite sizable to the binding energy of $T_{bb}$ . We estimate systematic errors to be $\pm 20$ MeV at most, which are mainly caused by the NRQCD approximation for $b$ quarks.
↳ hep-lathep-phnucl-thPRD(2023)·42 citations
08
Photon radiation by relatively slowly rotating fermions in magnetic field
Matteo Buzzegoli🇺🇸 · Jonathan D. Kroth🇺🇸 · Kirill Tuchin🇺🇸 · Nandagopal Vijayakumar🇺🇸
We study the electromagnetic radiation by a fermion carrying an electric charge $q$ embedded in a medium rotating with constant angular velocity $Ω$ parallel or anti-parallel to an external constant magnetic field $B$ . We assume that the rotation is "relatively slow"; namely, that the angular velocity $Ω$ is much smaller than the inverse magnetic length $q B$ . In practice, such angular velocity can be extremely high. The fermion motion is a superposition of two circular motions: one due to its rigid rotation caused by forces exerted by the medium, another due to the external magnetic field. We derive an exact analytical expression for the spectral rate and the total intensity of this type of synchrotron radiation. Our numerical calculations indicate very high sensitivity of the radiation to the angular velocity of rotation. We show that the radiation intensity is strongly enhanced if $q B$ and $Ω$ point in the opposite directions and is suppressed otherwise.
↳ hep-phastro-ph.HEnucl-thPRD(2023)·13 citations
09
Potential Constraints to Neutrino-Nucleus Interactions Based on Electron Scattering Data
V. Pandey🇺🇸
A thorough understanding of neutrino-nucleus interactions physics is crucial to achieving precision goals in broader neutrino physics programs. The complexity of nuclei comprising the detectors and limited understanding of their weak response constitutes one of the biggest systematic uncertainties in neutrino experiments - both at intermediate energies affecting the short- and long-baseline neutrino programs as well as at lower energies affecting coherent scattering neutrino programs. While electron and neutrino interactions are different at the primary vertex, many underlying relevant physical processes in the nucleus are the same in both cases, and electron scattering data collected with precisely controlled kinematics, large statistics and high precision allows one to constrain nuclear properties and specific interaction processes. To this end, electron-nucleus scattering experiments provide vital complementary information to test, assess and validate different nuclear models and event generators intended to be used in neutrino experiments. In fact, for many decades, the study of electron scattering off a nucleus has been used as a tool to probe the properties of that nucleus and its electromagnetic response. While previously existing electron scattering data provide important information, new and proposed measurements are tied closely to what is required for the neutrino program in terms of expanding kinematic reach, the addition of relevant nuclei and information on the final states hadronic system.
↳ hep-exhep-phnucl-exnucl-thPhys.Sci.Forum(2023)·2 citations

Affiliations

first authorsco-authorsvia INSPIRE

Effective field theory for radiative corrections to charged-current processes I: Vector coupling

All-Orders Evolution of Parton Distributions: Principle, Practice, and Predictions

The Gallium Anomaly

Effect of a magnetic field on the thermodynamic properties of a high-temperature hadron resonance gas with van der Waals interactions

Lattice study on a tetra-quark state Tbb​ in the HAL QCD method

Photon radiation by relatively slowly rotating fermions in magnetic field

Potential Constraints to Neutrino-Nucleus Interactions Based on Electron Scattering Data

Affiliations

Lattice study on a tetra-quark state $T_{bb}$ in the HAL QCD method