Wed·Jan 18, 2017Wednesday·January 18, 2017

1. 01*

   Progress On Neutrino-Proton Neutral-Current Scattering In MicroBooNE

   Stephen Pate (for the MicroBooNE Collaboration)🇺🇸

   The MicroBooNE Experiment at the Fermi National Accelerator Laboratory, an 89-ton active mass liquid argon time projection chamber, affords a unique opportunity to observe low-$Q^2$ neutral-current neutrino-proton scattering events. Neutral-current neutrino-proton scattering at $Q^2<1$ GeV${}^2$ is dominated by the proton's axial form factor, which can be written as a combination of contributions from the up, down, and strange quarks: $G_A(Q^2)=\frac{1}{2}[-G_A^u(Q^2)+G_A^d(Q^2)+G_A^s(Q^2)]$. The contribution from up and down quarks has been established in past charged-current measurements. The contribution from strange quarks at low $Q^2$ remains unmeasured; this is of great interest since the strange quark contribution to the proton spin can be determined from the low-$Q^2$ behavior: $\Delta S=G_A^s(Q^2=0)$. MicroBooNE began operating in the Booster Neutrino Beam in October 2015. I will present the status in observing isolated proton tracks in the MicroBooNE detector as a signature for neutral-current neutrino-proton events. The sensitivity of the MicroBooNE experiment for measuring the strange quark contribution to the proton spin will be discussed.

   nucl-exhep-exPoS(2017)·2 citations
2. 02*

   Constraining simultaneously nuclear symmetry energy and neutron-proton effective mass splitting with nucleus giant resonances from a dynamical approach

   Hai-Yun Kong · Jun Xu🇨🇳 · Lie-Wen Chen🇨🇳 · Bao-An Li🇺🇸 · Yu-Gang Ma🇨🇳

   With a newly improved isospin- and momentum-dependent interaction and an isospin-dependent Boltzmann-Uehling-Uhlenbeck transport model, we have investigated the effects of the slope parameter $L$ of the nuclear symmetry energy and the isospin splitting of the nucleon effective mass $m_{n-p}^{\ast }=(m_n^{\ast }-m_p^{\ast })/m$ on the centroid energy of the isovector giant dipole resonance and the electric dipole polarizability in ${}^{208}$Pb. With the isoscalar nucleon effective mass $m_s^{\ast }=0.7m$ constrained by the empirical optical potential, we obtain a constraint of $L=64.29\pm 11.84(\mathrm{MeV})$ and $m_{n-p}^{\ast }=(-0.019\pm 0.090)\delta$, with $\delta$ being the isospin asymmetry of nuclear medium. With the isoscalar nucleon effective mass $m_s^{\ast }=0.84m$ extracted from the excitation energy of the isoscalar giant quadruple resonance in ${}^{208}$Pb, we obtain a constraint of $L=53.85\pm 10.29(\mathrm{MeV})$ and $m_{n-p}^{\ast }=(0.216\pm 0.114)\delta$.

   ↳ nucl-thnucl-exPRC(2017)·60 citations
3. 03*

   Precision Theoretical Analysis of Neutron Radiative Beta Decay

   A. N. Ivanov🇦🇹 · R. Höllwieser🇦🇹 · N. I. Troitskaya🇦🇹 · M. Wellenzohn🇦🇹 · Ya. A. Berdnikov🇷🇺

   In the Standard Model of electroweak interactions and in the tree--approximation we calculate the rate and branching ratio of the neutron radiative beta decay with one-real photon emission by taking into account the contributions of the weak magnetism and proton recoil to order 1/m_p of the large proton mass m_p expansion. We find that the obtained contributions of the weak magnetism and proton recoil increase the rate and branching ratio of the neutron radiative beta decay by about 0.70%. This is large compared with the contribution of the weak magnetism and proton recoil of about 0.16% to the rate of the neutron beta decay, calculated in Phys. Rev. D88, 073002 (2013).

   ↳ hep-phhep-exnucl-exPRD(2017)·8 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.