Thu·Jul 12, 2018Thursday·July 12, 2018

1. 01*

   Near-barrier Photofission in ${}^{232}$Th and ${}^{238}$U

   J. A. Silano🇺🇸 · H. J. Karwowski🇺🇸

   A study of photofission of ${}^{232}$Th and ${}^{238}$U was performed using quasi-monoenergetic, linearly-polarized $\gamma$-ray beams from the High Intensity $\gamma$-ray Source at Triangle Universities Nuclear Laboratory. The prompt photofission neutron polarization asymmetries, neutron multiplicities and the photofission cross sections were measured in the near-barrier energy range of 4.3-6.0 MeV. This data set constitutes the lowest energy measurements of those observables to date using quasi-monoenergetic photons. Large polarization asymmetries are observed in both nuclei, consistent with the E1 excitation as observed by another measurement of this kind made in a higher energy range. Previous experimental evidence of a deep third minimum in the ${}^{238}$U fission barrier has been identified as an accelerator-induced background.

   nucl-exPRC(2018)·9 citations
2. 02*

   Constraining unintegrated gluon distributions from inclusive photon production in proton-proton collisions at the LHC

   Sanjin Benić🇯🇵 · Kenji Fukushima🇯🇵 · Oscar Garcia-Montero🇩🇪 · Raju Venugopalan🇺🇸

   We compute the leading order (LO) $qg\to q\gamma$ and next-to-leading order (NLO) $gg\to q\bar{q}\gamma$ contributions to inclusive photon production in proton-proton (p+p) collisions at the LHC. These channels provide the dominant contribution at LO and NLO for photon transverse momenta $k_{\gamma \perp }$ corresponding to momentum fractions of $x\le 0.01$ in the colliding protons. Our computations, performed in the dilute-dense framework of the Color Glass Condensate effective field theory (CGC EFT), show that the NLO contribution dominates at small-$x$ because it is sensitive to $k_{\perp }$-dependent unintegrated gluon distributions in both of the protons. We predict a maximal $10\%$ modification of the cross section at low $k_{\gamma \perp }$ as a direct consequence of the violation of $k_{\perp }$-factorization. The coherence effects responsible for this modification are enhanced in nuclei and can be identified from inclusive photon measurements in proton-nucleus collisions. We provide numerical results for the isolated inclusive photon cross section for $k_{\gamma \perp }\le 20$ GeV in p+p collisions that can be tested in the future at the LHC.

   ↳ hep-phnucl-exnucl-thPLB(2019)·41 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.