Wed·Jul 5, 2017Wednesday·July 5, 2017

1. 01*

   First direct constraints on Fierz interference in free neutron $\beta$ decay

   K. P. Hickerson · X. Sun · Y. Bagdasarova · D. Bravo-Berguño · L. J. Broussard · M. A.-P. Brown · R. Carr · S. Currie · X. Ding · B. W. Filippone · A. García · P. Geltenbort and 32 other authors

   Precision measurements of free neutron $\beta$-decay have been used to precisely constrain our understanding of the weak interaction. However the neutron Fierz interference term $b_n$, which is particularly sensitive to Beyond-Standard-Model tensor currents at the TeV scale, has thus far eluded measurement. Here we report the first direct constraints on this term, finding $b_n=0.067\pm 0.005_{\text{stat}}{}_{-0.061}^{+0.090}{}_{\text{sys}}$, consistent with the Standard Model. The uncertainty is dominated by absolute energy reconstruction and the linearity of the beta spectrometer energy response.

   nucl-exPRC(2017)·40 citations
2. 02*

   D-meson azimuthal anisotropy in mid-central Pb-Pb collisions at $\sqrt{{\mathbf{s}}_{\mathrm{NN}}}=5.02$ TeV

   ALICE Collaboration

   The azimuthal anisotropy coefficient $v_2$ of prompt D${}^0$, D${}^{+}$, D${}^{\ast +}$ and D${}_s^{+}$ mesons was measured in mid-central (30-50% centrality class) Pb-Pb collisions at a centre-of-mass energy per nucleon pair $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV, with the ALICE detector at the LHC. The D mesons were reconstructed via their hadronic decays at mid-rapidity, $|y|<0.8$, in the transverse momentum interval $1<p_{\mathrm{T}}<24$ GeV/$c$. The measured D-meson $v_2$ has similar values as that of charged pions. The D${}_s^{+}$ $v_2$, measured for the first time, is found to be compatible with that of non-strange D mesons. The measurements are compared with theoretical calculations of charm-quark transport in a hydrodynamically expanding medium and have the potential to constrain medium parameters.

   nucl-exhep-exPRL(2018)·179 citations
3. 03*

   Constraints on long-range spin-gravity and monopole-dipole couplings of the proton

   Derek F. Jackson Kimball🇺🇸 · Jordan Dudley🇺🇸 · Yan Li🇺🇸 · Dilan Patel🇺🇸 · Julian Valdez🇺🇸

   Results of a search for a long-range monopole-dipole coupling between the mass of the Earth and rubidium (Rb) nuclear spins are reported. The experiment simultaneously measures the spin precession frequencies of overlapping ensembles of ${}^{85}$Rb and ${}^{87}$Rb atoms contained within an evacuated, antirelaxation-coated vapor cell. The nuclear structure of the Rb isotopes makes the experiment particularly sensitive to spin-dependent interactions of the proton. The spin-dependent component of the gravitational energy of the proton in the Earth's field is found to be smaller than $3\times 10^{-18}\mathrm{eV}$, improving laboratory constraints on long-range monopole-dipole interactions by over three orders of magnitude.

   ↳ physics.atom-phnucl-exquant-phPRD(2017)·47 citations
4. 04*

   Testing and improving shear viscous phase space correction models

   Mridula Damodaran (1,2)🇺🇸 · Denes Molnar (1,2)🇺🇸 · Gergely Gábor Barnaföldi (2)🇭🇺 · Dániel Berényi (2)🇭🇺 · Máté Ferenc Nagy-Egri (2) ((1) Dept. of Physics and Astronomy, Purdue University, (2) Wigner Research Center for Physics, Budapest)🇭🇺

   Comparison of hydrodynamic calculations with experimental data inevitably requires a model for converting the fluid to particles. In this work, nonlinear $2\to 2$ kinetic theory is used to assess the overall accuracy of various shear viscous fluid-to-particle conversion models, such as the quadratic Grad corrections, the Strickland-Romatschke (SR) ansatz, self-consistent shear corrections from linearized kinetic theory, and the correction from the relaxation time approach. We test how well the conversion models can reconstruct, using solely the hydrodynamic fields computed from the transport, the phase space density for a massless one-component gas undergoing a 0+1D longitudinal boost-invariant expansion with approximately constant specific shear viscosity in the range $\sim 0.03\le \eta /s\le \sim 0.2$. In general we find that at early times the SR form is the most accurate, whereas at late times or for small $\eta /s\sim 0.05$ the self-consistent corrections from kinetic theory perform the best. In addition, we show that the reconstruction accuracy of additive shear viscous $f=f_{\mathrm{eq}}+\delta f$ models dramatically improves if one ensures, through "exponentiation", that $f$ is always positive. We also illustrate how even more accurate viscous $\delta f$ models can be constructed if one includes information about the past evolution of the system via the first time derivative of hydrodynamic fields. Such time derivatives are readily available in hydrodynamic simulations, though usually not included in the output.

   ↳ nucl-thnucl-ex14 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.