Thu·Dec 6, 2018Thursday·December 6, 2018

1. 01*

   PHENIX measurements of low momentum direct photon radiation

   Vladimir Khachatryan (for the PHENIX Collaboration)🇺🇸

   The versatility of RHIC allowed the PHENIX collaboration to measure low momentum direct photons from small systems, such as p+p, p+A, d+Au at $\sqrt{s_{NN}}=$200 GeV as well as from large A+A systems, such as Au+Au and Cu+Cu at 200 GeV and Au+Au at 62.4 GeV and 39 GeV. In these measurements PHENIX has discovered a large excess over the scaled p+p yield of direct photons in A+A collisions, and a non-zero excess over the scaled p+p yield in central p+A collisions. Another PHENIX discovery is that at low-$p_T$ the integrated yield of direct photons, $d{N}_{\gamma }/dy$, from large systems follows a universal scaling as a function of the charged-particle multiplicity, $(d{N}_{ch}/d\eta {)}^{\alpha }$, with $\alpha =1.25$. The observed scaling properties of direct photons from these systems show that the photon production yield increases faster than the charged-particle multiplicity.

   nucl-exNPA(2019)·11 citations
2. 02*

   First Measurements of the Double-Polarization Observables $F$, $P$, and $H$ in $\omega$ Photoproduction off Transversely Polarized Protons in the $N^{\ast }$ Resonance Region

   P. Roy🇺🇸 · S. Park🇺🇸 · V. Crede🇺🇸 · A. V. Anisovich🇩🇪 · E. Klempt🇩🇪 · V. A. Nikonov🇩🇪 · A. V. Sarantsev🇩🇪 · N. C. Wei🇨🇳 · F. Huang🇨🇳 · K. Nakayama🇺🇸 · K. P. Adhikari🇺🇸 · S. Adhikari🇺🇸 and 136 other authors

   First measurements of double-polarization observables in $\omega$ photoproduction off the proton are presented using transverse target polarization and data from the CEBAF Large Acceptance Spectrometer (CLAS) FROST experiment at Jefferson Lab. The beam-target asymmetry $F$ has been measured using circularly polarized, tagged photons in the energy range 1200 - 2700 MeV, and the beam-target asymmetries $H$ and $P$ have been measured using linearly polarized tagged photons in the energy range 1200 - 2000 MeV. These measurements significantly increase the database on polarization observables. The results are included in two partial-wave analyses and reveal significant contributions from several nucleon ($N^{\ast }$) resonances. In particular, contributions from new $N^{\ast }$ resonances listed in the Review of Particle Properties are observed, which aid in reaching the goal of mapping out the nucleon resonance spectrum.

   nucl-exhep-exPRL(2019)·15 citations
3. 03*

   Solar Neutrino Measurements

   Andrea Pocar

   We present the most recent results from the two currently running solar neutrino experiments, Borexino at the Gran Sasso laboratory in Italy and SuperK at Kamioka mine in Japan. SuperK has released the most precise yet measurement of the 8B solar neutrino interaction rate, with a precision better than 2\%, consistent with a constant solar neutrino emission over more than a decade. Borexino has released refined measurements of all neutrinos produced in the pp fusion chain. For the first time, one single detector has measured the entire range of solar neutrinos at once. These new data weakly favor a high-metallicity Sun. Prospects for measuring CNO solar neutrinos with Borexino are discussed, and a brief outlook on the field provided.

   nucl-exastro-ph.SRhep-ex1 citation
4. 04*

   Measurement of inclusive very forward jet cross sections in proton-lead collisions at $\sqrt{s_{\mathrm{NN}}}=$ 5.02 TeV

   CMS Collaboration

   Measurements of differential cross sections for inclusive very forward jet production in proton-lead collisions as a function of jet energy are presented. The data were collected with the CMS experiment at the LHC in the laboratory pseudorapidity range $-$6.6 $<$ $\eta$ $<$ $-$5.2. Asymmetric beam energies of 4 TeV for protons and 1.58 TeV per nucleon for Pb nuclei were used, corresponding to a center-of-mass energy per nucleon pair of $\sqrt{s_{\mathrm{NN}}}=$ 5.02 TeV. Collisions with either the proton (p+Pb) or the ion (Pb+p) traveling towards the negative $\eta$ hemisphere are studied. The jet cross sections are unfolded to stable-particle level cross sections with $p_{\mathrm{T}}$ $\gtrsim$ 3 GeV, and compared to predictions from various Monte Carlo event generators. In addition, the cross section ratio of p+Pb and Pb+p data is presented. The results are discussed in terms of the saturation of gluon densities at low fractional parton momenta. None of the models under consideration describes all the data over the full jet-energy range and for all beam configurations. Discrepancies between the differential cross sections in data and model predictions of more than two orders of magnitude are observed.

   ↳ hep-exnucl-exJHEP(2019)·23 citations
5. 05*

   Equation of state effects in core-collapse supernovae

   Hannah Yasin · Sabrina Schäfer🇩🇪 · Almudena Arcones🇩🇪 · Achim Schwenk🇩🇪

   We investigate the impact of different properties of the nuclear equation of state in core-collapse supernovae, with a focus on the proto-neutron-star contraction and its impact on the shock evolution. To this end, we introduce a range of equations of state that vary the nucleon effective mass, incompressibility, symmetry energy, and nuclear saturation point. This allows us to point to the different effects in changing these properties from the Lattimer and Swesty to the Shen et al. equations of state, the two most commonly used equations of state in simulations. In particular, we trace the contraction behavior to the effective mass, which determines the thermal nucleonic contributions to the equation of state. Larger effective masses lead to lower pressures at nuclear densities and a lower thermal index. This results in a more rapid contraction of the proto-neutron star and consequently higher neutrino energies, which aids the shock evolution to a faster explosion.

   ↳ nucl-thastro-ph.HEnucl-exPRL(2020)·127 citations
6. 06*

   Lower bound on the proton charge radius from electron scattering data

   Franziska Hagelstein (AEC Bern)🇨🇭 · Vladimir Pascalutsa (JGU Mainz)🇩🇪

   The proton charge-radius determinations from the electromagnetic form-factor measurements in electron-proton scattering require an extrapolation to zero momentum transfer ($Q^2=0$) which is prone to model-dependent assumptions. We show that the data at finite momentum transfer can be used to establish a rigorous lower bound on the proton charge radius. Using the available $ep$ data at low $Q^2$, we obtain $R_E>0.850(1)$ fm as the lower bound on the proton radius. This reaffirms the discrepancy between the $ep$ and muonic-hydrogen values, while bypassing the model-dependent assumptions that go into the fitting and extrapolation of the $ep$ data.

   ↳ nucl-thhep-phnucl-exPLB(2019)·7 citations
7. 07*

   Observation of Reactor Antineutrinos with a Rapidly-Deployable Surface-Level Detector

   Alireza Haghighat🇺🇸 · Patrick Huber🇺🇸 · Shengchao Li🇺🇸 · Jonathan M. Link🇺🇸 · Camillo Mariani🇺🇸 · Jaewon Park🇺🇸 · Tulasi Subedi🇺🇸

   We deployed a small, 80kg, antineutrino detector based on solid plastic scintillator, called MiniCHANDLER for nearly three months at a distance of 25m from a 2.9GW thermal power reactor core at the North Anna Nuclear Generating Station. We report the detection of an antineutrino signal resulting from inverse beta decay at 5.5 sigma significance with no overburden and minimal shielding. This result also demonstrates that 3D segmentation can be used to significantly improve the signal to noise ratio, in this case by a factor of 4. In addition, this measurement represents an observation of the positron spectrum in a small, surface-deployed detector; this observation of reactor antineutrinos was achieved with a mobile neutrino detector mounted in an ordinary, small trailer.

   ↳ physics.ins-dethep-exnucl-exPhys.Rev.Applied(2020)·48 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.