Tue·Feb 7, 2017Tuesday·February 7, 2017

1. 01*

   Insight into the narrow structure in {\boldmath{$\eta$}}-photoproduction on the neutron from helicity dependent cross sections

   L. Witthauer🇨🇭 · M. Dieterle🇨🇭 · S. Abt🇨🇭 · P. Achenbach🇩🇪 · F. Afzal🇩🇪 · Z. Ahmed🇨🇦 · J.R.M. Annand🇬🇧 · H.J. Arends🇩🇪 · M. Bashkanov🇬🇧 · R. Beck🇩🇪 · M. Biroth🇩🇪 · N.S. Borisov🇷🇺 and 74 other authors

   The double polarization observable $E$ and the helicity dependent cross sections ${\sigma }_{1/2}$ and ${\sigma }_{3/2}$ were measured for $\eta$ photoproduction from quasi-free protons and neutrons. The circularly polarized tagged photon beam of the A2 experiment at the Mainz MAMI accelerator was used in combination with a longitudinally polarized deuterated butanol target. The almost $4\pi$ detector setup of the Crystal Ball and TAPS is ideally suited to detect the recoil nucleons and the decay photons from $\eta \to 2\gamma$ and $\eta \to 3{\pi }^0$. The results show that the narrow structure previously observed in $\eta$ photoproduction from the neutron is only apparent in ${\sigma }_{1/2}$ and hence, most likely related to a spin-1/2 amplitude. Nucleon resonances that contribute to this partial wave in $\eta$ production are only $N1/2^{-}$ ($S_{11}$) and $N1/2^{+}$ ($P_{11}$). Furthermore, the extracted Legendre coefficients of the angular distributions for ${\sigma }_{1/2}$ are in good agreement with recent reaction model predictions assuming a narrow resonance in the $P_{11}$ wave as the origin of this structure.

   nucl-exPRL(2016)·41 citations
2. 02*

   Characterizing the mechanism(s) of heavy element synthesis

   W. Loveland🇺🇸

   A review of the current state of our understanding of complete fusion reaction mechanisms is presented, from the perspective of an experimentalist. For complete fusion reactions, the overall uncertainties in predicting heavy element synthesis cross sections are examined in terms of the uncertainties associated with the calculations of capture cross sections, fusion probabilities and survival probabilities.

   nucl-exnucl-thEPJA Web of Conferences 131, 04003 (2016)·0 citations
3. 03*

   Measurement of prompt and nonprompt J/psi production in pp and pPb collisions at sqrt(s[NN]) = 5.02 TeV

   CMS Collaboration

   This paper reports the measurement of J/psi meson production in proton-proton (pp) and proton-lead (pPb) collisions at a center-of-mass energy per nucleon pair of 5.02 TeV by the CMS experiment at the LHC. The data samples used in the analysis correspond to integrated luminosities of 28 inverse picobarns and 35 inverse nanobarns for pp and pPb collisions, respectively. Prompt and nonprompt J/psi mesons, the latter produced from the decay of B mesons, are measured in their dimuon decay channels. Differential cross sections are measured in the transverse momentum range of 2 < pt < 30 GeV/c, and center-of-mass rapidity ranges of abs(y[CM]) < 2.4 (pp) and -2.87 < y[CM] < 1.93 (pPb). The nuclear modification factor, R[pPb], is measured as functions of both pt and y[CM]. Small modifications of the J/psi cross sections are observed in pPb relative to pp collisions. The ratio of J/psi production cross sections in p-going and Pb-going directions, R[FB], studied as functions of pt and y[CM], shows a significant decrease for increasing transverse energy deposited at large pseudorapidities. These results, which cover a wide kinematic range, provide new insight on the role of cold nuclear matter effects on prompt and nonprompt J/psi production.

   nucl-exhep-exEPJC(2017)·109 citations
4. 04*

   Production of muons from heavy-flavour hadron decays in p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV

   ALICE Collaboration

   The production of muons from heavy-flavour hadron decays in p-Pb collisions at $\sqrt{{\text{s}}_{\mathrm{NN}}}=5.02$ TeV was studied for $2<p_{\mathrm{T}}<16$ GeV/$c$ with the ALICE detector at the CERN LHC. The measurement was performed at forward (p-going direction) and backward (Pb-going direction) rapidity, in the ranges of rapidity in the center-of-mass system (cms) $2.03<y_{\mathrm{cms}}<3.53$ and $-4.46<y_{\mathrm{cms}}<-2.96$, respectively. The production cross sections and nuclear modification factors are presented as a function of transverse momentum ($p_{\mathrm{T}}$). At forward rapidity, the nuclear modification factor is compatible with unity while at backward rapidity, in the interval $2.5<p_{\mathrm{T}}<3.5$ GeV/$c$, it is above unity by more than 2$\sigma$. The ratio of the forward-to-backward production cross sections is also measured in the overlapping interval $2.96<|y_{\mathrm{cms}}|<3.53$ and is smaller than unity by 3.7$\sigma$ in $2.5<p_{\mathrm{T}}<3.5$ GeV/$c$. The data are described by model calculations including cold nuclear matter effects.

   nucl-exhep-exPLB(2017)·43 citations
5. 05*

   Stellar ($n,\gamma$) cross section of ${}^{23}$Na

   E. Uberseder🇺🇸 · M. Heil🇩🇪 · F. Käppeler🇩🇪 · C. Lederer🇩🇪 · A. Mengoni🇮🇹 · S. Bisterzo🇮🇹 · M. Pignatari🇭🇺 · M. Wiescher🇺🇸

   The cross section of the ${}^{23}$Na($n,\gamma$)${}^{24}$Na reaction has been measured via the activation method at the Karlsruhe 3.7 MV Van de Graaff accelerator. NaCl samples were exposed to quasistellar neutron spectra at $kT=5.1$ and 25 keV produced via the ${}^{18}$O($p,n$)${}^{18}$F and ${}^7$Li($p,n$)${}^7$Be reactions, respectively. The derived capture cross sections $⟨\sigma {⟩}_{\mathrm{kT}=5keV}=9.1\pm 0.3$ mb and $⟨\sigma {⟩}_{\mathrm{kT}=25keV}=2.03\pm 0.05$ mb are significantly lower than reported in literature. These results were used to substantially revise the radiative width of the first ${}^{23}$Na resonance and to establish an improved set of Maxwellian average cross sections. The implications of the lower capture cross section for current models of $s$-process nucleosynthesis are discussed.

   nucl-exPRC(2017)·5 citations
6. 06*

   Is the caloric curve a robust signal of the phase transition in hot nuclei?

   E.Vient (for the INDRA and ALADIN Collaborations)🇫🇷

   The richness of the data set, collected by the INDRA collaboration during the last twenty years, enabled us to build a set of caloric curves for nuclei of various sizes, by using, for the first time, a single experimental set-up and a single experimental protocol. We will therefore present the different caloric curves ($E^{\ast }-T$) obtained by a new calorimetry, for Quasi-Projectiles produced by symmetric or quasi symmetric reactions at different incident energies (Au+Au, Xe+Sn, Ni+Ni). For all these systems, a clear change of the de-excitation process of hot nuclei is observed but this one is neither a plateau nor a back-bending, but a sudden change of slope.

   nucl-exNuovo Cim.C(2016)·1 citation
7. 07*

   Azimuthally differential pion femtoscopy in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV

   ALICE Collaboration

   We present the first azimuthally differential measurements of the pion source size relative to the second harmonic event plane in Pb-Pb collisions at a center-of-mass energy per nucleon-nucleon pair of $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV. The measurements have been performed in the centrality range 0-50% and for pion pair transverse momenta $0.2<k_{\mathrm{T}}<0.7$ GeV/$c$. We find that the $R_{\mathrm{side}}$ and $R_{\mathrm{out}}$ radii, which characterize the pion source size in the directions perpendicular and parallel to the pion transverse momentum, oscillate out of phase, similar to what was observed at the Relativistic Heavy Ion Collider (RHIC). The final-state source eccentricity, estimated via $R_{\mathrm{side}}$ oscillations, is found to be significantly smaller than the initial-state source eccentricity, but remains positive; indicating that even after a stronger expansion in the in-plane direction, the pion source at the freeze-out is still elongated in the out-of-plane direction. The 3+1D hydrodynamic calculations are in qualitative agreement with observed centrality and transverse momentum $R_{\mathrm{side}}$ oscillations, but systematically underestimate the oscillation magnitude.

   nucl-exhep-exPRL(2017)·28 citations
8. 08*

   Spin asymmetry for proton-deuteron Drell-Yan process with tensor-polarized deuteron

   S. Kumano🇯🇵 · Qin-Tao Song🇯🇵

   Tensor structure of the deuteron can be studied by deep inelastic scattering and Drell-Yan process to understand it in terms of quark and gluon degrees of freedom. It probes interesting features in the deuteron including a D-wave contribution. In the charged-lepton DIS, twist-two structure functions $b_1$ and $b_2$ are expressed by tensor-polarized parton distribution functions (PDFs). We note that the HERMES experimental measurement of $b_1$ seems to be much different from a conventional theoretical prediction. This puzzling situation should be significantly improved in the near future by an approved experiment to measure $b_1$ at JLab. On the other hand, the tensor-polarized PDFs, especially antiquark distributions, could be measured by spin asymmetries in the Drell-Yan process with a tensor-polarized deuteron at Fermilab. In this work, we estimate tensor-polarization asymmetries for the Fermilab Drell-Yan experiment by using a parametrization for the tensor-polarized PDFs to explain the HERMES $b_1$ data. Obtained spin asymmetries are typically a few percent order and they could be measured by the Fermilab-E1039 experiment. Since the tensor-polarized antiquark distributions will play an important role to solve the puzzle, further theoretical and experimental efforts are needed toward the Drell-Yan experiment at Fermilab and other hadron facilities.

   ↳ nucl-thhep-lathep-phnucl-ex7 citations
9. 09*

   Establishment of Imaging Spectroscopy of Nuclear Gamma-Rays based on Geometrical Optics

   Toru Tanimori🇯🇵 · Yoshitaka Mizumura🇯🇵 · Atsushi Takada · Shohei Miyamoto🇯🇵 · Taito Takemura🇯🇵 · Tetsuro Kishimoto🇯🇵 · Shotaro Komura🇯🇵 · Hidetoshi Kubo🇯🇵 · Shunsuke Kurosawa🇯🇵 · Yoshihiro Matsuoka🇯🇵 · Kentaro Miuchi🇯🇵 · Tetsuya Mizumoto and 7 other authors

   Since the discovery of nuclear gamma-rays, its imaging has been limited to pseudo imaging, such as Compton Camera (CC) and coded mask. Pseudo imaging does not keep physical information (intensity, or brightness in Optics) along a ray, and thus is capable of no more than qualitative imaging of bright objects. To attain quantitative imaging, cameras that realize geometrical optics is essential, which would be, for nuclear MeV gammas, only possible via complete reconstruction of the Compton process. Recently we have revealed that "Electron Tracking Compton Camera" (ETCC) provides a well-defined Point Spread Function (PSF). The information of an incoming gamma is kept along a ray with the PSF and that is equivalent to geometrical optics. Here we present an imaging-spectroscopic measurement with the ETCC. Our results highlight the intrinsic difficulty with CCs in performing accurate imaging, and show that the ETCC surmounts this problem. The imaging capability also helps the ETCC suppress the noise level dramatically by ~3 orders of magnitude without a shielding structure. Furthermore, full reconstruction of Compton process with the ETCC provides spectra free of Compton edges. These results mark the first proper imaging of nuclear gammas based on the genuine geometrical optics.

   ↳ physics.ins-detastro-ph.IMhep-exnucl-exSci.Rep.(2017)·26 citations
10. 10*

    First On-Site True Gamma-Ray Imaging-Spectroscopy of Contamination near Fukushima Plant

    Dai Tomono🇯🇵 · Tetsuya Mizumoto · Atsushi Takada · Shotaro Komura🇯🇵 · Yoshihiro Matsuoka🇯🇵 · Yoshitaka Mizumura🇯🇵 · Makoto Oda🇯🇵 · Toru Tanimori🇯🇵

    We have developed an Electron Tracking Compton Camera (ETCC), which provides a well-defined Point Spread Function (PSF) by reconstructing a direction of each gamma as a point and realizes simultaneous measurement of brightness and spectrum of MeV gamma-rays for the first time. Here, we present the results of our on-site pilot gamma-imaging-spectroscopy with ETCC at three contaminated locations in the vicinity of the Fukushima Daiichi Nuclear Power Plants in Japan in 2014. The obtained distribution of brightness (or emissivity) with remote-sensing observations is unambiguously converted into the dose distribution. We confirm that the dose distribution is consistent with the one taken by conventional mapping measurements with a dosimeter physically placed at each grid point. Furthermore, its imaging spectroscopy, boosted by Compton-edge-free spectra, reveals complex radioactive features in a quantitative manner around each individual target point in the background-dominated environment. Notably, we successfully identify a "micro hot spot" of residual caesium contamination even in an already decontaminated area. These results show that the ETCC performs exactly as the geometrical optics predicts, demonstrates its versatility in the field radiation measurement, and reveals potentials for application in many fields, including the nuclear industry, medical field, and astronomy.

    ↳ physics.ins-detastro-ph.IMhep-exnucl-exSci.Rep.(2017)·7 citations
11. 11*

    Feasibility Studies for Single Transverse-Spin Asymmetry Measurements at a Fixed-Target Experiment Using the LHC Proton and Lead Beams (AFTER@LHC)

    Daniel Kikoła🇵🇱 · Miguel García Echevarria🇪🇸 · Cynthia Hadjidakis🇫🇷 · Jean-Philippe Lansberg🇫🇷 · Cedric Lorcé🇫🇷 · Laure Massacrier🇫🇷 · Catarina Marques Quintans🇵🇹 · Andrea Signori🇺🇸 · Barbara Trzeciak🇳🇱

    The measurement of Single Transverse-Spin Asymmetries, $A_N$, for various quarkonium states and Drell-Yan lepton pairs can shed light on the orbital angular momentum of quarks and gluons, a fundamental ingredient of the proton-spin puzzle. The AFTER@LHC proposal combines a unique kinematic coverage and large luminosities thanks to the Large Hadron Collider beams to deliver precise measurements, complementary to the knowledge provided by collider experiments such as at RHIC. In this paper, we report on sensitivity studies for $J/\psi$, ${\rm Y}$ and Drell-Yan $A_N$ done using the performance of LHCb-like or ALICE-like detectors, combined with polarised gaseous hydrogen and helium-3 targets. In particular, such analyses will provide us with new insights and knowledge about transverse-momentum-dependent parton distribution functions for quarks and gluons and on twist-3 collinear matrix elements in the proton and the neutron.

    ↳ hep-exhep-phnucl-exnucl-thFew Body Syst.(2017)·44 citations
12. 12*

    Concurrent application of ANC and THM to assess the ${}^{13}\mathrm{C}(\alpha ,n{)}^{16}\mathrm{O}$ absolute cross section at astrophysical energies and possible consequences for neutron production in low-mass AGB stars

    Oscar Trippella · Marco La Cognata

    The ${}^{13}\mathrm{C}(\alpha ,n{)}^{16}\mathrm{O}$ reaction is considered to be the main neutron source responsible for the production of heavy nuclides (from $\mathrm{Sr}$ to $\mathrm{Bi}$) through slow $n$-capture nucleosynthesis ($s$-process) at low temperatures during the asymptotic giant branch (AGB) phase of low mass stars ($\lesssim 3-4{\mathrm{M}}_{\odot }$, or LMSs). In recent years, several direct and indirect measurements have been carried out to determine the cross section at the energies of astrophysical interest (around $190\pm 40\mathrm{keV}$). However, they yield inconsistent results causing a highly uncertain reaction rate and affecting the neutron release in LMSs. In this work we have combined two indirect approaches, the asymptotic normalization coefficient (or ANC) and the Trojan Horse Method (THM), to unambiguously determine the absolute value of the ${}^{13}\mathrm{C}(\alpha ,n{)}^{16}\mathrm{O}$ astrophysical factor. Therefore, we have determined a very accurate reaction rate to be introduced into astrophysical models of $s$-process nucleosynthesis in LMSs. Calculations using such recommended rate have shown limited variations in the production of those neutron-rich nuclei (with $86\le A\le 209$) receiving contribution only by slow neutron captures.

    ↳ astro-ph.SRnucl-exnucl-thApJ(2017)·34 citations
13. 13*

    Evidence for light-by-light scattering in heavy-ion collisions with the ATLAS detector at the LHC

    ATLAS Collaboration

    Light-by-light scattering ($\gamma \gamma \to \gamma \gamma$) is a quantum-mechanical process that is forbidden in the classical theory of electrodynamics. This reaction is accessible at the Large Hadron Collider thanks to the large electromagnetic field strengths generated by ultra-relativistic colliding lead (Pb) ions. Using 480 $\mu$b${}^{-1}$ of Pb+Pb collision data recorded at a centre-of-mass energy per nucleon pair of 5.02 TeV by the ATLAS detector, the ATLAS Collaboration reports evidence for the $\gamma \gamma \to \gamma \gamma$ reaction. A total of 13 candidate events are observed with an expected background of 2.6$\pm$0.7 events. After background subtraction and analysis corrections, the fiducial cross section of the process $\text{Pb+Pb}(\gamma \gamma )\to {\text{Pb}}^{(\ast )}\text{+}{\text{Pb}}^{(\ast )}\gamma \gamma$, for photon transverse energy $E_{\mathrm{T}}>$3 GeV, photon absolute pseudorapidity $|\eta |<$2.4, diphoton invariant mass greater than 6 GeV, diphoton transverse momentum lower than 2 GeV and diphoton acoplanarity below 0.01, is measured to be 70 $\pm$ 24 (stat.) $\pm$ 17 (syst.) nb, which is in agreement with Standard Model predictions.

    ↳ hep-exnucl-exNat.Phys.(2017)·509 citations
14. 14*

    Relative flow fluctuations as a probe of initial state fluctuations

    Giuliano Giacalone🇫🇷 · Jacquelyn Noronha-Hostler🇺🇸 · Jean-Yves Ollitrault🇫🇷

    Elliptic flow, $v_2$, and triangular flow, $v_3$, are to a good approximation linearly proportional to the corresponding spatial anisotropies of the initial density profile, ${\epsilon }_2$ and ${\epsilon }_3$. Using event-by-event hydrodynamic simulations, we point out when deviations from this linear scaling are to be expected. When these deviations are negligible, relative $v_n$ fluctuations are equal to relative ${\epsilon }_n$ fluctuations, and one can directly probe models of initial conditions using ratios of cumulants, for instance $v_n\{4\}/v_n\{2\}$. We argue that existing models of initial conditions tend to overestimate flow fluctuations in central Pb+Pb collisions, and to underestimate them in peripheral collisions. We make predictions for $v_3\{6\}$ in noncentral Pb+Pb collisions, and for $v_3\{4\}$ and $v_3\{6\}$ in high-multiplicity p+Pb collisions.

    ↳ nucl-thhep-phnucl-exPRC(2017)·101 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.