Fri·Sep 25, 2015Friday·September 25, 2015

1. 01*

   The influence of experimental setup on the spectroscopy investigation of ${}^{14}$Be by Coulomb breakup reaction

   Yu-Shou Song🇨🇳 · Ying-Wei Hou🇨🇳 · Li-Yuan Hu🇨🇳 · Hui-Lan Liu🇨🇳 · Hong-Yi Wu🇨🇳

   The two-body core+$2n$ cluster structure was implemented to describe the two-neutron halo nucleus ${}^{14}\mathrm{Be}$, where the core${}^{12}\mathrm{Be}$ was assumed inert and at ground state and the dineutron was assumed at pure $2S_0$ state. Based on such a structure the three-body continuum-discretized coupled-channel (CDCC) calculation was successfully used to deal with the ${}^{14}\mathrm{Be}$ breakup reactions of ${}^{14}\mathrm{Be}{+}^{12}\mathrm{C}$ at 68~MeV/nucleon and ${}^{14}\mathrm{Be}+$Pb at 35~MeV/nucleon.Consequently, we modeled the kinematically complete measurement experiment of ${}^{14}\mathrm{Be}$ (35~MeV/nucleon) Coulomb breakup at a lead target with the help of Geant4. From the simulation data the relative energy spectrum was constructed by the invariant mass method and $B(E1)$ spectrum was extracted using virtual photon model. The influence of the target thickness and detector performance on the spectroscopy was investigated.

   nucl-exphysics.ins-detCPC(2016)·0 citations
2. 02*

   Multiplicity and transverse momentum evolution of charge-dependent correlations in pp, p-Pb, and Pb-Pb collisions at the LHC

   ALICE Collaboration

   We report on two-particle charge-dependent correlations in pp, p-Pb, and Pb-Pb collisions as a function of the pseudorapidity and azimuthal angle difference, $\mathrm{\Delta }\eta$ and $\mathrm{\Delta }\phi$ respectively. These correlations are studied using the balance function that probes the charge creation time and the development of collectivity in the produced system. The dependence of the balance function on the event multiplicity as well as on the trigger and associated particle transverse momentum ($p_{\mathrm{T}}$) in pp, p-Pb, and Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=7$, 5.02, and 2.76 TeV, respectively, are presented. In the low transverse momentum region, for $0.2<p_{\mathrm{T}}<2.0$ GeV/$c$, the balance function becomes narrower in both $\mathrm{\Delta }\eta$ and $\mathrm{\Delta }\phi$ directions in all three systems for events with higher multiplicity. The experimental findings favor models that either incorporate some collective behavior (e.g. AMPT) or different mechanisms that lead to effects that resemble collective behavior (e.g. PYTHIA8 with color reconnection). For higher values of transverse momenta the balance function becomes even narrower but exhibits no multiplicity dependence, indicating that the observed narrowing with increasing multiplicity at low $p_{\mathrm{T}}$ is a feature of bulk particle production.

   nucl-exhep-exEPJC(2016)·65 citations
3. 03*

   Measurement of D${}_s^{+}$ production and nuclear modification factor in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV

   ALICE Collaboration

   The production of prompt D${}_s^{+}$ mesons was measured for the first time in collisions of heavy nuclei with the ALICE detector at the LHC. The analysis was performed on a data sample of Pb-Pb collisions at a centre-of-mass energy per nucleon pair, $\sqrt{s_{\mathrm{NN}}}$, of 2.76 TeV in two different centrality classes, namely 0-10% and 20-50%. D${}_s^{+}$ mesons and their antiparticles were reconstructed at mid-rapidity from their hadronic decay channel D${}_s^{+}\to \varphi {\pi }^{+}$, with $\varphi \to$K${}^{-}$K${}^{+}$, in the transverse momentum intervals $4<p_{\mathrm{T}}<12$ GeV/$c$ and $6<p_{\mathrm{T}}<12$ GeV/$c$ for the 0-10% and 20-50% centrality classes, respectively. The nuclear modification factor $R_{\mathrm{AA}}$ was computed by comparing the $p_{\mathrm{T}}$-differential production yields in Pb-Pb collisions to those in proton-proton (pp) collisions at the same energy. This pp reference was obtained using the cross section measured at $\sqrt{s}=7$ TeV and scaled to $\sqrt{s}=2.76$ TeV. The $R_{\mathrm{AA}}$ of D${}_s^{+}$ mesons was compared to that of non-strange D mesons in the 10% most central Pb-Pb collisions. At high $p_{\mathrm{T}}$ ($8<p_{\mathrm{T}}<12$ GeV/$c$) a suppression of the D${}_s^{+}$-meson yield by a factor of about three, compatible within uncertainties with that of non-strange D mesons, is observed. At lower $p_{\mathrm{T}}$ ($4<p_{\mathrm{T}}<8$ GeV/$c$) the values of the D${}_s^{+}$-meson $R_{\mathrm{AA}}$ are larger than those of non-strange D mesons, although compatible within uncertainties. The production ratios D${}_s^{+}$/D${}^0$ and D${}_s^{+}$\D${}^{+}$ were also measured in Pb-Pb collisions and compared to their values in proton-proton collisions.

   nucl-exhep-exJHEP(2016)·83 citations
4. 04*

   Centrality evolution of the charged-particle pseudorapidity density over a broad pseudorapidity range in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV

   ALICE Collaboration

   The centrality dependence of the charged-particle pseudorapidity density measured with ALICE in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ over a broad pseudorapidity range is presented. This Letter extends the previous results reported by ALICE to more peripheral collisions. No strong change of the charged-particle pseudorapidity density distributions with centrality is observed, and when normalised to the number of participating nucleons in the collisions, the evolution over pseudorapidity with centrality is likewise small. The broad pseudorapidity range allows precise estimates of the total number of produced charged particles which we find to range from $162\pm 22$ (syst.) to $17170\pm 770$ (syst.) in 80-90% and 0-5 central collisions, respectively. The total charged-particle multiplicity is seen to approximately scale with the number of participating nucleons in the collision. This suggests that hard contributions to the charged-particle multiplicity are limited. The results are compared to models which describe $\text{mbox}d{N}_{\text{mbox}ch}/\text{mbox}d\eta$ at mid-rapidity in the most central Pb-Pb collisions and it is found that these models do not capture all features of the distributions.

   nucl-exhep-exPLB(2016)·75 citations
5. 05*

   Direct photon production in Pb-Pb collisions at \sqrt{s_\rm{NN}} = 2.76 TeV

   ALICE Collaboration

   Direct photon production at mid-rapidity in Pb-Pb collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}=2.76$ TeV was studied in the transverse momentum range $0.9<p_{\mathrm{T}}<14$ GeV$/c$. Photons were detected with the highly segmented electromagnetic calorimeter PHOS and via conversions in the ALICE detector material with the $e^{+}{e}^{-}$ pair reconstructed in the central tracking system. The results of the two methods were combined and direct photon spectra were measured for the 0-20%, 20-40%, and 40-80% centrality classes. For all three classes, agreement was found with perturbative QCD calculations for $p_{\mathrm{T}}\gtrsim 5$ GeV$/c$. Direct photon spectra down to $p_{\mathrm{T}}\approx 1$ GeV$/c$ could be extracted for the 20-40% and 0-20% centrality classes. The significance of the direct photon signal for $0.9<p_{\mathrm{T}}<2.1$ GeV$/c$ is $2.6\sigma$ for the 0-20% class. The spectrum in this $p_{\mathrm{T}}$ range and centrality class can be described by an exponential with an inverse slope parameter of $(297\pm 12^{\mathrm{stat}}\pm 41^{\mathrm{syst}})$ MeV. State-of-the-art models for photon production in heavy-ion collisions agree with the data within uncertainties.

   nucl-exhep-exPLB(2016)·427 citations
6. 06*

   Azimuthal anisotropy of charged jet production in $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV Pb-Pb collisions

   ALICE Collaboration

   We present measurements of the azimuthal dependence of charged jet production in central and semi-central $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV Pb-Pb collisions with respect to the second harmonic event plane, quantified as $v_2^{\mathrm{ch}\mathrm{jet}}$. Jet finding is performed employing the anti-$k_{\mathrm{T}}$ algorithm with a resolution parameter $R$ = 0.2 using charged tracks from the ALICE tracking system. The contribution of the azimuthal anisotropy of the underlying event is taken into account event-by-event. The remaining (statistical) region-to-region fluctuations are removed on an ensemble basis by unfolding the jet spectra for different event plane orientations independently. Significant non-zero $v_2^{\mathrm{ch}\mathrm{jet}}$ is observed in semi-central collisions (30-50\% centrality) for 20 $<$ $p_{\mathrm{T}}^{\mathrm{ch}\mathrm{jet}}$ $<$ 90 $\mathrm{GeV}/c$. The azimuthal dependence of the charged jet production is similar to the dependence observed for jets comprising both charged and neutral fragments, and compatible with measurements of the $v_2$ of single charged particles at high $p_{\mathrm{T}}$. Good agreement between the data and predictions from JEWEL, an event generator simulating parton shower evolution in the presence of a dense QCD medium, is found in semi-central collisions.

   nucl-exhep-exPLB(2016)·87 citations
7. 07*

   Determination of integral cross sections of 3H in Al foils monitors irradiated by protons with energies ranging from 40 to 2600 MeV

   Yu. E. Titarenko · V. F. Batyaev · M. V. Chauzova · I. A. Kashirin · S. V. Malinovskiy · K. V. Pavlov · V. I. Rogov · A. Yu. Titarenko · V. M. Zhivun · S. G. Mashnik🇺🇸 · A. Yu. Stankovskiy

   Results of t production in Al foil monitors are presented. These foils have been irradiated by protons of different energies in a range of 0.04 - 2.6 GeV. The irradiations were carried out at the ITEP accelerator U-10 under the ISTC Project 3266 during 2006 - 2009. t has been extracted from Al foils using an A307 Sample Oxidizer. The values of the Al(p,x)t cross sections obtained in these experiments are compared with data measured at other laboratories and with results of simulations by the MCNP6 radiation transport code using the CEM03.03 event generator.

   nucl-exEPJ Web Conf.(2016)·0 citations
8. 08*

   Charge, neutron, and weak size of the atomic nucleus

   G. Hagen🇺🇸 · A. Ekström🇺🇸 · C. Forssén🇸🇪 · G. R. Jansen🇺🇸 · W. Nazarewicz🇺🇸 · T. Papenbrock🇺🇸 · K. A. Wendt🇺🇸 · S. Bacca🇨🇦 · N. Barnea🇮🇱 · B. Carlsson🇸🇪 · C. Drischler🇩🇪 · K. Hebeler🇩🇪 and 5 other authors

   What is the size of the atomic nucleus? This deceivably simple question is difficult to answer. While the electric charge distributions in atomic nuclei were measured accurately already half a century ago, our knowledge of the distribution of neutrons is still deficient. In addition to constraining the size of atomic nuclei, the neutron distribution also impacts the number of nuclei that can exist and the size of neutron stars. We present an ab initio calculation of the neutron distribution of the neutron-rich nucleus ${}^{48}$Ca. We show that the neutron skin (difference between radii of neutron and proton distributions) is significantly smaller than previously thought. We also make predictions for the electric dipole polarizability and the weak form factor; both quantities are currently targeted by precision measurements. Based on ab initio results for ${}^{48}$Ca, we provide a constraint on the size of a neutron star.

   ↳ nucl-thnucl-exNat.Phys.(2015)·379 citations
9. 09*

   Towards the understanding of jet shapes and cross sections in heavy ion collisions using soft-collinear effective theory

   Yang-Ting Chien🇺🇸 · Ivan Vitev🇺🇸

   We calculate the jet shape and the jet cross section in heavy ion collisions using soft-collinear effective theory (SCET) and its extension with Glauber gluon interactions in the medium (SCET${}_{\mathrm{G}}$). We use the previously developed framework to systematically resum the jet shape at next-to-leading logarithmic accuracy, and we consistently include the medium modification by incorporating the leading order medium-induced splitting functions. The calculation provides, for the first time, a quantitative understanding of the jet shape modification measurement in lead-lead collisions at $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV at the LHC. The inclusive jet suppression is also calculated within the same framework beyond the traditional concept of parton energy loss, and the dependence on the centrality, the jet radius and the jet kinematics is examined. In the end we present predictions for the anticipated jet shape and cross section measurements in lead-lead collisions at $\sqrt{s_{\mathrm{NN}}}\approx 5.1$ TeV at the LHC.

   ↳ hep-phhep-exnucl-exnucl-thJHEP(2016)·150 citations
10. 10*

    Violations of discrete space-time symmetries in chiral effective field theory

    J. de Vries🇩🇪 · Ulf-G. Meißner🇩🇪

    We review recent progress in the theoretical description of the violation of discrete space-time symmetries in hadronic and nuclear systems. We focus on parity-violating and time-reversal-conserving interactions which are induced by the Standard Model weak interaction, and on parity- and time-reversal-violating interactions which can be caused by a nonzero QCD theta term or by beyond-the-Standard Model physics. We discuss the origins of such interactions and review the development of the chiral effective field theory extension that includes discrete symmetry violations. We discuss the construction of symmetry-violating chiral Lagrangians and nucleon-nucleon potentials and their applications in few-body systems.

    ↳ hep-phnucl-exnucl-thIJMPE(2016)·52 citations
11. 11*

    Hybrid method to resolve the neutrino mass hierarchy by supernova (anti)neutrino induced reactions

    D. Vale🇭🇷 · T. Rauscher🇬🇧 · N. Paar🇭🇷

    We introduce a hybrid method to determine the neutrino mass hierarchy by simultaneous measurements of responses of at least two detectors to antineutrino and neutrino fluxes from accretion and cooling phases of core-collapse supernovae. The (anti)neutrino-nucleus cross sections for ${}^{56}$Fe and ${}^{208}$Pb are calculated in the framework of the relativistic nuclear energy density functional and weak interaction Hamiltonian, while the cross sections for inelastic scattering on free protons $\mathrm{p}({\bar{\nu }}_{\mathrm{e}},{\mathrm{e}}^{+})\mathrm{n}$ are obtained using heavy-baryon chiral perturbation theory. The modelling of (anti)neutrino fluxes emitted from a protoneutron star in a core-collapse supernova include collective and Mikheyev-Smirnov-Wolfenstein effects inside the exploding star. The particle emission rates from the elementary decay modes of the daughter nuclei are calculated for normal and inverted neutrino mass hierarchy. It is shown that simultaneous use of (anti)neutrino detectors with different target material allows to determine the neutrino mass hierarchy from the ratios of ${\nu }_{\mathrm{e}}$- and ${\bar{\nu }}_{\mathrm{e}}$-induced particle emissions. This hybrid method favors neutrinos from the supernova cooling phase and the implementation of detectors with heavier target nuclei (${}^{208}$Pb) for the neutrino sector, while for antineutrinos the use of free protons in mineral oil or water is the appropriate choice.

    ↳ nucl-thastro-ph.IMastro-ph.SRhep-ex+1JCAP(2016)·12 citations
12. 12*

    Subterranean production of neutrons, ${}^{39}$Ar and ${}^{21}$Ne: Rates and uncertainties

    Ondřej Šrámek · Lauren Stevens · William F. McDonough🇺🇸 · Sujoy Mukhopadhyay · R. J. Peterson

    Accurate understanding of the subsurface production rate of the radionuclide ${}^{39}$Ar is necessary for argon dating techniques and noble gas geochemistry of the shallow and the deep Earth, and is also of interest to the WIMP dark matter experimental particle physics community. Our new calculations of subsurface production of neutrons, ${}^{21}$Ne, and ${}^{39}$Ar take advantage of the state-of-the-art reliable tools of nuclear physics to obtain reaction cross sections and spectra (TALYS) and to evaluate neutron propagation in rock (MCNP6). We discuss our method and results in relation to previous studies and show the relative importance of various neutron, ${}^{21}$Ne, and ${}^{39}$Ar nucleogenic production channels. Uncertainty in nuclear reaction cross sections, which is the major contributor to overall calculation uncertainty, is estimated from variability in existing experimental and library data. Depending on selected rock composition, on the order of $10^7$-$10^{10}$ {\alpha} particles are produced in one kilogram of rock per year (order of 1-$10^3$ kg${}^{-1}$ s${}^{-1}$); the number of produced neutrons is lower by $\sim 6$ orders of magnitude, ${}^{21}$Ne production rate drops by an additional factor of 15-20, and another one order of magnitude or more is dropped in production of ${}^{39}$Ar. Our calculation yields a nucleogenic ${}^{21}$Ne/${}^4$He production ratio of $(4.6\pm 0.6)\times 10^{-8}$ in Continental Crust and $(4.2\pm 0.5)\times 10^{-8}$ in Oceanic Crust and Depleted Mantle. Calculated ${}^{39}$Ar production rates span a great range from $29\pm 9$ atoms kg-rock${}^{-1}$ yr${}^{-1}$ in the K-Th-U-enriched Upper Continental Crust to $(2.6\pm 0.8)\times 10^{-4}$ atoms kg-rock${}^{-1}$ yr${}^{-1}$ in Depleted Upper Mantle. Nucleogenic ${}^{39}$Ar production exceeds the cosmogenic production below $\sim 700$ meters depth and thus, affects radiometric ages of groundwater.

    ↳ physics.geo-phnucl-exphysics.ins-detGeochim.Cosmochim.Acta(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.