Thu·May 24, 2018Thursday·May 24, 2018

1. 01*

   Revealing Color Forces with Transverse Polarized Electron Scattering

   W. Armstrong (1 and 2)🇺🇸 · H. Kang (3)🇰🇷 · A. Liyanage (4)🇺🇸 · J. Maxwell (5 and 6)🇺🇸 · J. Mulholland (5)🇺🇸 · L. Ndukum (7)🇺🇸 · A. Ahmidouch (8)🇺🇸 · I. Albayrak (4)🇺🇸 · A. Asaturyan (9)🇦🇲 · O. Ates (4)🇺🇸 · H. Baghdasaryan (5)🇺🇸 · W. Boeglin (10)🇺🇸 and 92 other authors

   The Spin Asymmetries of the Nucleon Experiment (SANE) measured two double spin asymmetries using a polarized proton target and polarized electron beam at two beam energies, 4.7 GeV and 5.9 GeV. A large-acceptance open-configuration detector package identified scattered electrons at 40${}^{\circ }$ and covered a wide range in Bjorken $x$ ($0.3<x<0.8$). Proportional to an average color Lorentz force, the twist-3 matrix element, ${\tilde{d}}_2^p$, was extracted from the measured asymmetries at $Q^2$ values ranging from 2.0 to 6.0 GeV${}^2$. The data display the opposite sign compared to most quark models, including the lattice QCD result, and an apparently unexpected scale dependence. Furthermore when combined with the neutron data in the same $Q^2$ range the results suggest a flavor independent average color Lorentz force.

   nucl-exPRL(2019)·35 citations
2. 02*

   Non-strange Dibaryon Resonances Observed in the $\gamma d\to {\pi }^0{\pi }^{0}d$ Reaction

   T. Ishikawa🇯🇵 · H. Fujimura🇯🇵 · H. Fukasawa🇯🇵 · R. Hashimoto🇯🇵 · Q. He🇯🇵 · Y. Honda🇯🇵 · T. Iwata🇯🇵 · S. Kaida🇯🇵 · H. Kanda🇯🇵 · J. Kasagi🇯🇵 · A. Kawano🇯🇵 · S. Kuwasaki🇯🇵 and 25 other authors

   Coherent double neutral-pion photoproduction on the deuteron, $\gamma d${$\to$}${\pi }^0{\pi }^{0}d$, has been experimentally studied at incident photon energies ranging from 0.75 to 1.15 GeV. The total cross section as a function of the $\gamma d$ center-of-mass energy shows resonance-like behavior, which peaks at approximately 2.47 and 2.63 GeV. The measured angular distribution of deuteron emission is rather flat, which cannot be reproduced by the kinematics of quasi-free ${\pi }^0{\pi }^0$ production with deuteron coalescence. In ${\pi }^{0}d$ invariant-mass distributions, a clear peak is observed at $2.14\pm 0.01$ GeV$/c^2$ with a width of $0.09\pm 0.01$ GeV$/c^2$. The spin-parity of this state is restricted to $1^{+}$, $2^{+}$ or $3^{-}$ from the angular distributions of the two ${\pi }^0$s. The present work shows strong evidence for the existence of an isovector dibaryon resonance with a mass of 2.14 GeV$/c^2$. The $2^{+}$ assignment is consistent with the theoretically predicted ${\mathcal{D}}_{12}$ state, and also with the energy dependence of the $\pi d$ partial-wave amplitude ${}^3{P}_2$ for the ${\pi }^{\pm }d${$\to$}${\pi }^{\pm }d$ and ${\pi }^{+}d${$\to$}$pp$ reactions.

   nucl-exhep-exPLB(2019)·44 citations
3. 03*

   A Cautionary Tale: The Coulomb Modified ANC for the $1/2_2^{+}$ State in ${}^{17}$O

   N. Keeley · K.W. Kemper🇺🇸 · K. Rusek

   We discuss the impact of the uncertainty ($\pm 8$ keV) in the excitation energy of the astrophysically important 6.356 MeV $1/2_2^{+}$ state of ${}^{17}$O on the precision with which the Coulomb reduced ANC ($\tilde{C}$) for the $⟨{}^{17}\mathrm{O}(1/2_2^{+})\mid \text{protect}{}^{13}\mathrm{C}+\alpha ⟩$ overlap can be extracted from direct reaction data. We find a linear dependence of ${\tilde{C}}^2$ on the binding energy, the value extracted varying by a factor of 4 over the range $E_{\mathrm{ex}}=6.356$ -- $6.348$ MeV. This represents an intrinsic limit on the precision with which ${\tilde{C}}^2$ can be determined which cannot be improved unless or until the uncertainty in $E_{\mathrm{ex}}$ is reduced.

   nucl-exnucl-thEPJA(2018)·5 citations
4. 04*

   Measurement of jets and photons with the ALICE experiment at the LHC

   Lucia Leardini🇩🇪

   Jets and direct photons are used to probe the formation and the properties of the Quark-Gluon Plasma (QGP) by the ALICE Collaboration. The results shown here will present the measurements obtained from Pb$-$Pb and p$-$Pb collisions. It is observed that in Pb$-$Pb collisions jets are collimated and hadron yields (${\pi }^0$ and $\eta$) at high transverse momentum undergo strong suppression due to the interaction of the patrons with the QGP. On the other hand, photons do not show any suppression in this region, and, in addition, an excess attributed to a thermal emission is observed at low transverse momentum. No hints of medium modifications are observed for the p$-$Pb results, for which a jet quenching limit of $-$0.4 GeV/$c$ is calculated.

   nucl-ex0 citations
5. 05*

   Peering into the dark side: magnesium lines establish a massive neutron star in PSR J2215+5135

   Manuel Linares (UPC, IAC)🇪🇸 · Tariq Shahbaz · Jorge Casares (IAC, ULL)🇪🇸

   New millisecond pulsars (MSPs) in compact binaries provide a good opportunity to search for the most massive neutron stars. Their main-sequence companion stars are often strongly irradiated by the pulsar, displacing the effective center of light from their barycenter and making mass measurements uncertain. We present a series of optical spectroscopic and photometric observations of PSR J2215+5135, a "redback" binary MSP in a 4.14 hr orbit, and measure a drastic temperature contrast between the dark/cold (T${}_{\mathrm{N}}$=5660${}_{-380}^{+260}$ K) and bright/hot (T${}_{\mathrm{D}}$=8080${}_{-280}^{+470}$ K) sides of the companion star. We find that the radial velocities depend systematically on the atmospheric absorption lines used to measure them. Namely, the semi-amplitude of the radial velocity curve of J2215 measured with magnesium triplet lines is systematically higher than that measured with hydrogen Balmer lines, by 10%. We interpret this as a consequence of strong irradiation, whereby metallic lines dominate the dark side of the companion (which moves faster) and Balmer lines trace its bright (slower) side. Further, using a physical model of an irradiated star to fit simultaneously the two-species radial velocity curves and the three-band light curves, we find a center-of-mass velocity of K${}_2$=412.3$\pm$5.0 km s${}^{-1}$ and an orbital inclination i=63.9${}^{\circ }$${}_{-2.7}^{+2.4}$. Our model is able to reproduce the observed fluxes and velocities without invoking irradiation by an extended source. We measure masses of M${}_1$=2.27${}_{-0.15}^{+0.17}$ M${}_{\odot }$ and M${}_2$=0.33${}_{-0.02}^{+0.03}$ M${}_{\odot }$ for the neutron star and the companion star, respectively. If confirmed, such a massive pulsar would rule out some of the proposed equations of state for the neutron star interior.

   ↳ astro-ph.HEnucl-exApJ(2018)·327 citations
6. 06*

   Measurement of Transverse Single Spin Asymmetries in ${\pi }^0$ Production from $p^{\uparrow }+p$ and $p^{\uparrow }+A$ Collisions at STAR

   Christopher Dilks (STAR Collaboration)🇺🇸

   In 2015 the first collisions between polarized protons and nuclei occurred at the Relativistic Heavy Ion Collider (RHIC), at a center-of-mass energy of $\sqrt{s_{NN}}=200$ GeV. Comparisons between spin asymmetries and cross-sections in $p+p$ production to those in $p+A$ production provide insight into nuclear structure, namely nuclear modification factors, nuclear dependence of spin asymmetries, and comparison to models with saturation effects. The transverse single-spin asymmetry, $A_N$, has been measured in ${\pi }^0$ production in the STAR Forward Meson Spectrometer (FMS), an electromagnetic calorimeter covering a forward psuedorapidity range of $2.6<\eta <4$. Within this kinematic range, STAR has previously reported the persistence of large ${\pi }^0$ asymmetries with unexpected dependences on $p_T$ and event topology in $p+p$ collisions. This talk will compare these dependences to those in $p+A$ production.

   ↳ hep-exnucl-exPoS(2016)·3 citations
7. 07*

   Dynamically integrated transport approach for heavy-ion collisions at high baryon density

   Yukinao Akamatsu🇯🇵 · Masayuki Asakawa🇯🇵 · Tetsufumi Hirano🇯🇵 · Masakiyo Kitazawa🇯🇵 · Kenji Morita🇵🇱 · Koichi Murase🇯🇵 · Yasushi Nara🇯🇵 · Chiho Nonaka🇯🇵 · Akira Ohnishi🇯🇵

   We develop a new dynamical model for high energy heavy-ion collisions in the beam energy region of the highest net-baryon densities on the basis of non-equilibrium microscopic transport model JAM and macroscopic 3+1D hydrodynamics by utilizing a dynamical initialization method. In this model,dynamical fluidization of a system is controlled by the source terms of the hydrodynamic fields. In addition, time dependent core-corona separation of hot regions is implemented. We show that our new model describes multiplicities and mean transverse mass in heavy-ion collisions within a beam energy region of $3<\sqrt{s_{NN}}<30$ GeV. Good agreement of the beam energy dependence of the $K^{+}/{\pi }^{+}$ ratio is obtained, which is explained by the fact that a part of the system is not thermalized in our core-corona approach.

   ↳ nucl-thhep-phnucl-exPRC(2018)·87 citations
8. 08*

   Measurement of nuclear modification factors of ${\rm Y}$(1S), ${\rm Y}$(2S), and ${\rm Y}$(3S) mesons in PbPb collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}=$ 5.02 TeV

   CMS Collaboration

   The cross sections for ${\rm Y}$(1S), ${\rm Y}$(2S), and ${\rm Y}$(3S) production in lead-lead (PbPb) and proton-proton (pp) collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}=$ 5.02 TeV have been measured using the CMS detector at the LHC. The nuclear modification factors, R${}_{\mathrm{AA}}$, derived from the PbPb-to-pp ratio of yields for each state, are studied as functions of meson rapidity and transverse momentum, as well as PbPb collision centrality. The yields of all three states are found to be significantly suppressed, and compatible with a sequential ordering of the suppression, R${}_{\mathrm{AA}}$(${\rm Y}$(1S)) $>$ R${}_{\mathrm{AA}}$(${\rm Y}$(2S)) $>$ R${}_{\mathrm{AA}}$(${\rm Y}$(3S)) . The suppression of ${\rm Y}$(1S) is larger than that seen at $\sqrt{s_{{}_{\mathrm{NN}}}}=$ 2.76 TeV, although the two are compatible within uncertainties. The upper limit on the R${}_{\mathrm{AA}}$ of ${\rm Y}$(3S) integrated over $p_{\mathrm{T}}$ and rapidity is 0.094 at 95% confidence level, which is the strongest suppression observed for any hadron species in heavy ion collisions to date.

   ↳ hep-exnucl-exPLB(2019)·251 citations
9. 09*

   Hierarchy of azimuthal anisotropy harmonics in collisions of small systems from the Color Glass Condensate

   Mark Mace🇺🇸 · Vladimir V. Skokov🇺🇸 · Prithwish Tribedy🇺🇸 · Raju Venugopalan🇺🇸

   We demonstrate that the striking systematics of two-particle azimuthal Fourier harmonics $v_2$ and $v_3$ in ultrarelativistic collisions of protons, deuterons and helium-3 ions off gold nuclei measured by the PHENIX Collaboration [arXiv:1805.02973] at the Relativistic Heavy Ion Collider (RHIC) is reproduced in the Color Glass Condensate (CGC) effective field theory. This contradicts the claim in [arXiv:1805.02973] that their data rules out initial state based explanations. The underlying systematics of the effect, as discussed previously in [arXiv:1705.00745,arXiv:1706.06260,arXiv:1801.09704], arise from the differing structure of strong color correlations between gluon domains of size $1/Q_S$ at fine ($p_{\perp }⪆Q_S$) or coarser ($p_{\perp }⪅Q_S$) transverse momentum resolution. Further tests of the limits of validity of this framework can be carried out in light-heavy ion collisions at both RHIC and the Large Hadron Collider. Such measurements also offer novel opportunities for further exploration of the role of the surprisingly large short-range nuclear correlations measured at Jefferson Lab.

   ↳ hep-phnucl-exnucl-thPRL(2018)·113 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.