Nuclear Theory·nucl-th

Tuesday·September 1, 2015

19 papers—11 primary·8 cross-listed

12
The Sensitivity of Core-Collapse Supernovae to Nuclear Electron Capture
Chris Sullivan · Evan O'Connor · Remco G. T. Zegers · Thomas Grubb · Sam M. Austin
A weak-rate library aimed at investigating the sensitivity of astrophysical environments to variations of electron-capture rates on medium-heavy nuclei has been developed. With this library, the sensitivity of the core-collapse and early post-bounce phases of core-collapse supernovae to nuclear electron-capture is examined by systematically and statistically varying electron-capture rates of individual nuclei. The rates are adjusted by factors consistent with uncertainties indicated by comparing theoretical rates to those deduced from charge-exchange and $β$ -decay measurements. To ensure a model independent assessment, sensitivity studies across a comprehensive set of progenitors and equations of state are performed. In our systematic study, we find a +16/-4 % range in the mass of the inner-core at the time of shock formation and a $\pm$ 20% range of peak {\nu}e-luminosity during the deleptonization burst. These ranges are each five times as large as those seen from a separate progenitor study in which we evaluated the sensitivity of these parameters to 32 presupernova stellar models. It is also found that the simulations are more sensitive to a reduction in the electron-capture rates than an enhancement, and in particular to the reduction in the rates for neutron-rich nuclei near the N = 50 closed neutron-shell. As measurements for medium-heavy (A > 65) and neutron-rich nuclei are sparse, and because accurate theoretical models which account for nuclear structure considerations on the individual nucleus level are not readily available, rates for these nuclei may be overestimated. If more accurate estimates confirm this, results from this study indicate that significant changes to the core-collapse trajectory can be expected. For this reason, experimental and theoretical efforts should focus in this region of the nuclear chart.
↳ astro-ph.HEnucl-exnucl-thApJ(2016)·96 citations
13
The Edge of Jets and Subleading Non-Global Logs
Duff Neill🇺🇸
A persistent and fascinating problem at the high energy colliders are jets. Often trying to observe physics underlying the hard interactions at colliders requires experimental cuts in phase space, defining several jet or beam regions. QCD being a gauge theory that readily decays into infra-red modes, correlations between jet regions is almost inevitable, spoiling the predictivity of fixed order QCD calculations. One is faced with the task of calculating the evolution of a reduced density matrix, where successively less energetic (jet) regions are integrated out, to gain control of the calculation. I relate the decay rates governing the flow into the IR to an effective field theory expansion in soft jets, allowing a systematic and resummed calculation of these rates, while further relating them to physically observable features of the QCD cascade. To demonstrate the utility of the soft jet expansion, I present a factorization theorem for a soft subjet collinearly splitting in and out of a parent fat jet. Using the resummation properties of this factorization theorem, I elucidate the structure of the subleading non-global logs (encoding the jet correlations) in the hemisphere jet mass distribution, as well as give a collinear improvement of the leading order resummation equation, the BMS equation. I compare to other approaches to subleading resummation of NGLs, and find the collinear improvement of the leading order equation removes the need for kinematic-dependent corrections in the IR averaging procedure of the reduced density matrix, so that no further large logs can be generated in the IR. Finally I end with speculation about connections with collinear improvements of the NLO B-JIMWLK hierarchy for small- $x$ resummation.
↳ hep-phnucl-th35 citations
14
Two Nucleon Systems at $m_{π} \sim 450 MeV$ from Lattice QCD
Kostas Orginos🇺🇸 · Assumpta Parreno🇪🇸 · Martin J. Savage🇺🇸 · Silas R. Beane🇺🇸 · Emmanuel Chang🇺🇸 · William Detmold🇺🇸
Nucleon-nucleon systems are studied with lattice quantum chromodynamics at a pion mass of $m_{π} \sim 450 MeV$ in three spatial volumes using $n_{f} = 2 + 1$ flavors of light quarks. At the quark masses employed in this work, the deuteron binding energy is calculated to be $B_{d} = 14. 4_{- 2.6}^{+ 3.2} MeV$ , while the dineutron is bound by $B_{nn} = 12. 5_{- 5.0}^{+ 3.0} MeV$ . Over the range of energies that are studied, the S-wave scattering phase shifts calculated in the 1S0 and 3S1-3D1 channels are found to be similar to those in nature, and indicate repulsive short-range components of the interactions, consistent with phenomenological nucleon-nucleon interactions. In both channels, the phase shifts are determined at three energies that lie within the radius of convergence of the effective range expansion, allowing for constraints to be placed on the inverse scattering lengths and effective ranges. The extracted phase shifts allow for matching to nuclear effective field theories, from which low energy counterterms are extracted and issues of convergence are investigated. As part of the analysis, a detailed investigation of the single hadron sector is performed, enabling a precise determination of the violation of the Gell-Mann--Okubo mass relation. [An Erratum to the published version is included as an appendix. It details the impact of an error discovered in 2020 and corrects typographical errors.]
↳ hep-lathep-phnucl-thPRD(2015)·167 citations
15
Critical line of 2+1 flavor QCD: Toward the continuum limit
Paolo Cea🇮🇹 · Leonardo Cosmai🇮🇹 · Alessandro Papa🇮🇹
We determine the continuum limit of the curvature of the pseudocritical line of QCD with $n_{f}$ =2+1 staggered fermions at nonzero temperature and quark density. We perform Monte Carlo simulations at imaginary baryon chemical potentials, adopting the HISQ/tree action discretization, as implemented in the code by the MILC collaboration. Couplings are adjusted so as to move on a line of constant physics, as determined in Ref.~\cite{Bazavov:2011nk}, with the strange quark mass $m_{s}$ fixed at its physical value and a light-to-strange mass ratio $m_{l} / m_{s} = 1/20$ . The chemical potential is set at the same value for the three quark species, $μ_{l} = μ_{s} \equiv μ$ . We attempt an extrapolation to the continuum using the results on lattices with temporal size up to $L_{t} = 12$ . Our estimate for the continuum value of the curvature $κ$ at zero baryon density, $κ = 0.020 (4)$ , is compared with recent lattice results and with experimental determinations of the freeze-out curve.
↳ hep-lathep-phnucl-thPRD(2016)·112 citations
16
Elastic proton scattering at intermediate energies as a probe of the $^{6, 8}$ He nuclear matter densities
Le Xuan Chung · Oleg A. Kiselev · Dao T. Khoa · Peter Egelhof
The Glauber model analysis of the elastic $^{6, 8}$ He+ $p$ scattering data at energies around 700 MeV/nucleon, measured in two separate experiments at GSI-Darmstadt, has been done using several phenomenological parametrizations of the nuclear matter density. By taking into account the new data points measured at the high momentum transfer, the nuclear matter radii of $^{6, 8}$ He were accurately determined from the Glauber model analysis of the data, with the spin-orbital interaction explicitly taken into account. The well-known geometry for the core and dineutron halo has been used with the new parametrizations of the $^{6}$ He density to extract the detailed information on the structure of $^{6}$ He in terms of the core and dineutron halo radii. An enhanced sensitivity of the data measured at the high momentum transfer to the core part of the $^{6, 8}$ He densities has been found.
↳ nucl-exnucl-thPRC(2015)·20 citations
17
Charge-conjugation symmetric complete impulse approximation for the pion electromagnetic form factor in the Covariant Spectator Theory
Elmar P. Biernat🇵🇹 · Franz Gross🇺🇸 · M. T. Peña🇵🇹 · Alfred Stadler🇵🇹
The pion form factor is calculated in the framework of the charge-conjugation invariant Covariant Spectator Theory. This formalism is established in Minkowski space and the calculation is set up in momentum space. In a previous calculation we included only the leading pole coming from the spectator quark (referred to as the relativistic impulse approximation). In this paper we also include the contributions from the poles of the quark which interacts with the photon and average over all poles in both the upper and lower half planes in order to preserve charge conjugation invariance (referred to as the $C$ -symmetric complete impulse approximation). We find that for small pion mass these contributions are significant at all values of the four-momentum transfer $Q^{2}$ but, surprisingly, do not alter the shape obtained from the spectator poles alone.
↳ hep-phnucl-thPRD(2015)·18 citations
18
Initial state and thermalization in the Color Glass Condensate framework
F. Gelis🇫🇷
In this review, I present the description of the early stages of heavy ion collisions at high energy in the Color Glass Condensate framework, from the pre-collision high energy nuclear wavefunction to the point where hydrodynamics may start becoming applicable.
↳ hep-phnucl-thIJMPE(2015)·40 citations
19
Sensitivity to Z-prime and non-standard neutrino interactions from ultra-low threshold neutrino-nucleus coherent scattering
Bhaskar Dutta🇺🇸 · Rupak Mahapatra🇺🇸 · Louis E. Strigari🇺🇸 · Joel W. Walker🇺🇸
We discuss prospects for probing Z-prime and non-standard neutrino interactions using neutrino-nucleus coherent scattering with ultra-low energy (~ 10 eV) threshold Si and Ge detectors. The analysis is performed in the context of a specific and contemporary reactor-based experimental proposal, developed in cooperation with the Nuclear Science Center at Texas A&M University, and referencing available technology based upon economical and scalable detector arrays. For expected exposures, we show that sensitivity to the Z-prime mass is on the order of several TeV, and is complementary to the LHC search with low mass detectors in the near term. This technology is also shown to provide sensitivity to the neutrino magnetic moment, at a level that surpasses terrestrial limits, and is competitive with more stringent astrophysical bounds. We demonstrate the benefits of combining silicon and germanium detectors for distinguishing between classes of models of new physics, and for suppressing correlated systematic uncertainties.
↳ hep-phastro-ph.HEhep-exnucl-ex+1PRD(2016)·76 citations

Affiliations

first authorsco-authorsvia INSPIRE