Thu·Apr 16, 2020Thursday·April 16, 2020

1. 01*

   Direct photon and light neutral meson production in the era of precision physics at the LHC

   Meike Charlotte Danisch (on behalf of the ALICE Collaboration)🇩🇪

   In these proceedings we present the latest results from ALICE on direct photon and light neutral meson production in p$-$Pb and Pb$-$Pb collisions. The direct photon excess ratio $R_{\gamma }$ in different charged particle multiplicity classes of p$-$Pb collisions at $\sqrt{s_{NN}}=5.02\mathrm{TeV}$ is shown. In addition, we present the direct photon elliptic flow coefficient $v_2$ in central and semicentral events of Pb$-$Pb collisions at $\sqrt{s_{NN}}=2.76\mathrm{TeV}$. An outlook on ongoing and future measurements is given.

   ↳ hep-exnucl-exSpringer Proc.Phys.(2020)·1 citation
2. 02*

   Diffractive dijet photoproduction at the EIC

   V. Guzey🇷🇺 · M. Klasen🇩🇪

   We present a first, detailed study of diffractive dijet photoproduction at the recently approved electron-ion collider (EIC) at BNL. Apart from establishing the kinematic reaches for various beam types, energies and kinematic cuts, we make precise predictions at next-to-leading order (NLO) of QCD in the most important kinematic variables. We show that the EIC will provide new and more precise information on the diffractive parton density functions (PDFs) in the pomeron than previously obtained at HERA, illuminate the still disputed mechanism of global vs.\ only resolved-photon factorization breaking, and provide access to a completely new quantity, i.e. nuclear diffractive PDFs.

   ↳ hep-phhep-exnucl-exnucl-thJHEP(2020)·13 citations
3. 03*

   Proton Holography -- Discovering Odderon from Scaling Properties of Elastic Scattering

   T. Csorgo🇭🇺 · T. Novak🇭🇺 · R. Pasechnik🇸🇪 · A. Ster🇭🇺 · I. Szanyi🇭🇺

   We investigate the scaling properties of elastic scattering data at ISR and LHC energies and find that the significance of an Odderon observation is larger than the discovery threshold of 5$\sigma$. As an unexpected by-product of these investigations, for certain experimentally relevant cases, we also conjecture the possibility of proton holography with the help of elastic proton-proton scattering.

   ↳ hep-phhep-exnucl-exnucl-thEPJ Web Conf.(2020)·3 citations
4. 04*

   How well do we know the neutron-matter equation of state at the densities inside neutron stars? A Bayesian approach with correlated uncertainties

   C. Drischler🇺🇸 · R. J. Furnstahl🇺🇸 · J. A. Melendez🇺🇸 · D. R. Phillips🇺🇸

   We introduce a new framework for quantifying correlated uncertainties of the infinite-matter equation of state derived from chiral effective field theory ($\chi$EFT). Bayesian machine learning via Gaussian processes with physics-based hyperparameters allows us to efficiently quantify and propagate theoretical uncertainties of the equation of state, such as $\chi$EFT truncation errors, to derived quantities. We apply this framework to state-of-the-art many-body perturbation theory calculations with nucleon-nucleon and three-nucleon interactions up to fourth order in the $\chi$EFT expansion. This produces the first statistically robust uncertainty estimates for key quantities of neutron stars. We give results up to twice nuclear saturation density for the energy per particle, pressure, and speed of sound of neutron matter, as well as for the nuclear symmetry energy and its derivative. At nuclear saturation density the predicted symmetry energy and its slope are consistent with experimental constraints.

   ↳ nucl-thastro-ph.HEhep-phnucl-exPRL(2020)·357 citations
5. 05*

   Estimating the Color Lifetime of Energetic Quarks

   William K. Brooks🇨🇱 · Jorge A. López🇨🇱

   Using a simple geometric framework with a realistic nuclear density distribution, we fit published HERMES data to determine fundamental properties of hadronization using the nuclear medium as a spatial analyzer. Our approach uses a fit to the transverse momentum broadening observable and the hadronic multiplicity ratio; the simultaneous fit to two different observables strongly constrains the outcome. Using the known sizes of the target nuclei, we extract the color lifetime, finding a z${}_{\mathrm{h}}$-dependent range of values from 2 to 8 fm/c for these data. We also extract estimates for the $\hat{q}$ transport coefficient characterizing the strength of the interaction between the quark and the cold nuclear medium, finding an average value of 0.035$\pm$0.011 GeV${}^2$/fm. With a three-parameter model we obtain satisfactory fits to the data with a goodness-of-fit parameter ${\chi }^2$/dof of 1.1 or less. In a secondary fit of the results from that model we independently find a value for the Lund String Model string tension of 1.00$\pm$0.05 GeV/fm. We evaluated the sensitivity for extracting quark energy loss and effective in-medium hadronic cross sections using four-parameter variants of the model, finding large uncertainties in both cases. Our results suggest that hadronic interaction of forming hadrons in the nuclear medium is the primary dynamical cause of meson attenuation in the HERMES data, with quark energy loss playing a more minor role.

   ↳ hep-phhep-exnucl-exPLB(2021)·17 citations
6. 06*

   Nuclear excitation of the ${}^{229}$Th isomer via defect states in doped crystals

   Brenden S. Nickerson · Martin Pimon · Pavlo V. Bilous · Johannes Gugler · Kjeld Beeks🇦🇹 · Tomas Sikorsky · Peter Mohn · Thorsten Schumm🇦🇹 · Adriana Pálffy🇩🇪

   When Th nuclei are doped in CaF${}_2$ crystals, a set of electronic defect states appears in the crystal bandgap which would otherwise provide complete transparency to vacuum-ultraviolet radiation. The coupling of these defect states to the 8 eV ${}^{229m}$Th nuclear isomer in the CaF${}_2$ crystal is investigated theoretically. We show that although previously viewed as a nuisance, the defect states provide a starting point for nuclear excitation via electronic bridge mechanisms involving stimulated emission or absorption using an optical laser. The rates of these processes are at least two orders of magnitude larger than direct photoexcitation of the isomeric state using available light sources. The nuclear isomer population can also undergo quenching when triggered by the reverse mechanism, leading to a fast and controlled decay via the electronic shell. These findings are relevant for a possible solid-state nuclear clock based on the ${}^{229m}$Th isomeric transition.

   ↳ cond-mat.mtrl-scinucl-exquant-phPRL(2020)·40 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.