Thu·May 26, 2016Thursday·May 26, 2016

1. 01*

   D-meson production in p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV and in pp collisions at $\sqrt{s}=7$ TeV

   ALICE Collaboration

   The production cross sections of the prompt charmed mesons D${}^0$, D${}^{+}$, D${}^{\ast +}$ and D${}_s$ were measured at mid-rapidity in p-Pb collisions at a centre-of-mass energy per nucleon pair $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV with the ALICE detector at the LHC. D mesons were reconstructed from their decays D${}^0\to {\mathrm{K}}^{-}{\pi }^{+}$, D${}^{+}\to {\mathrm{K}}^{-}{\pi }^{+}{\pi }^{+}$, D${}^{\ast +}\to D^0{\pi }^{+}$, D${}_s^{+}\to \varphi {\pi }^{+}\to {\mathrm{K}}^{-}{\mathrm{K}}^{+}{\pi }^{+}$, and their charge conjugates. The $p_{\mathrm{T}}$-differential production cross sections were measured at mid-rapidity in the interval $1<p_{\mathrm{T}}<24$ GeV/$c$ for D${}^0$, D${}^{+}$ and D${}^{\ast +}$ mesons and in $2<p_{\mathrm{T}}<12$ GeV/$c$ for D${}_s$ mesons, using an analysis method based on the selection of decay topologies displaced from the interaction vertex. The production cross sections of the D${}^0$, D${}^{+}$ and D${}^{\ast +}$ mesons were also measured in three $p_{\mathrm{T}}$ intervals as a function of the rapidity $y_{\mathrm{cms}}$ in the centre-of-mass system in $-1.26<y_{\mathrm{cms}}<0.34$. In addition, the prompt D${}^0$ cross section was measured in pp collisions at $\sqrt{s}=7$ TeV and p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV down to $p_{\mathrm{T}}=0$ using an analysis technique that is based on the estimation and subtraction of the combinatorial background, without reconstruction of the D${}^0$ decay vertex. The nuclear modification factor $R_{\mathrm{pPb}}(p_{\mathrm{T}})$, defined as the ratio of the $p_{\mathrm{T}}$-differential D-meson cross section in p-Pb collisions and that in pp collisions scaled by the mass number of the Pb nucleus, was calculated for the four D-meson species and found to be compatible with unity within experimental uncertainties. The results are compared to theoretical calculations that include cold-nuclear-matter effects and to transport model calculations incorporating the interactions of charm quarks with an expanding deconfined medium.

   nucl-exhep-exPRC(2016)·178 citations
2. 02*

   A proposed direct measurement of cross section at Gamow window for key reaction ${}^{19}$F($p$,$\alpha$)${}^{16}$O in Asymptotic Giant Branch stars with a planned accelerator in CJPL

   J.J. He🇨🇳 · S.W. Xu · S.B. Ma · J. Hu🇨🇳 · L.Y. Zhang · C.B. Fu🇨🇳 · N.T. Zhang · G. Lian🇨🇳 · J. Su🇨🇳 · Y.J. Li · S.Q. Yan🇨🇳 · Y.P. Shen and 7 other authors

   In 2014, the National Natural Science Foundation of China (NSFC) approved the Jinping Underground Nuclear Astrophysics laboratory (JUNA) project, which aims at direct cross-section measurements of four key stellar nuclear reactions right down to the Gamow windows. In order to solve the observed fluorine overabundances in Asymptotic Giant Branch (AGB) stars, measuring the key ${}^{19}$F($p$,$\alpha$)${}^{16}$O reaction at effective burning energies (i.e., at Gamow window) is established as one of the scientific research sub-projects. The present paper describes this sub-project in details, including motivation, status, experimental setup, yield and background estimation, aboveground test, as well as other relevant reactions.

   nucl-exSCPMA(2016)·14 citations
3. 03*

   Recent results in nuclear astrophysics

   Alain Coc🇫🇷 · Fairouz Hammache🇫🇷 · Juergen Kiener🇫🇷

   In this review, we emphasize the interplay between astrophysical observations, modeling, and nuclear physics laboratory experiments. Several important nuclear cross sections for astrophysics have long been identified e.g. 12C(alpha,gamma)16O for stellar evolution, or 13C(alpha,n)16O and 22Ne(alpha,n)25Mg as neutron sources for the s-process. More recently, observations of lithium abundances in the oldest stars, or of nuclear gamma-ray lines from space, have required new laboratory experiments. New evaluation of thermonuclear reaction rates now includes the associated rate uncertainties that are used in astrophysical models to i) estimate final uncertainties on nucleosynthesis yields and ii) identify those reactions that require further experimental investigation. Sometimes direct cross section measurements are possible, but more generally the use of indirect methods is compulsory in view of the very low cross sections. Non-thermal processes are often overlooked but are also important for nuclear astrophysics, e.g. in gamma-ray emission from solar flares or in the interaction of cosmic rays with matter, and also motivate laboratory experiments. Finally, we show that beyond the historical motivations of nuclear astrophysics, understanding i) the energy sources that drive stellar evolution and ii) the origin of the elements can also be used to give new insights into physics beyond the standard model.

   nucl-exastro-ph.HEEPJA(2015)·19 citations
4. 04*

   Radii and binding energies in oxygen isotopes: a puzzle for nuclear forces

   V. Lapoux🇫🇷 · V. Somà🇫🇷 · C. Barbieri🇬🇧 · H. Hergert🇺🇸 · J.D. Holt🇨🇦 · S.R. Stroberg🇨🇦

   We present a systematic study of both nuclear radii and binding energies in (even) oxygen isotopes from the valley of stability to the neutron drip line. Both charge and matter radii are compared to state-of-the-art {\it ab initio} calculations along with binding energy systematics. Experimental matter radii are obtained through a complete evaluation of the available elastic proton scattering data of oxygen isotopes. We show that, in spite of a good reproduction of binding energies, {\it ab initio} calculations with conventional nuclear interactions derived within chiral effective field theory fail to provide a realistic description of charge and matter radii. A novel version of two- and three-nucleon forces leads to considerable improvement of the simultaneous description of the three observables for stable isotopes, but shows deficiencies for the most neutron-rich systems. Thus, crucial challenges related to the development of nuclear interactions remain.

   nucl-exnucl-thPRL(2016)·136 citations
5. 05*

   Freezeout conditions in proton-proton collisions at the top RHIC and LHC energies

   Sabita Das🇨🇳 · Debadeepti Mishra🇮🇳 · Sandeep Chatterjee🇮🇳 · Bedangadas Mohanty🇮🇳

   The freezeout conditions in proton-proton collisions at $\sqrt{s_{\text{NN}}}=200$, $900$ and $7000$ GeV have been extracted by fits to the mean hadron yields at mid-rapidity within the framework of the statistical model of an ideal gas of hadrons and resonances in the grand canonical ensemble. The variation of the extracted freezeout thermal parameters and the goodness of the fits with $\sqrt{s_{\text{NN}}}$ are discussed. We find the extracted temperature and baryon chemical potential of the freezeout surface to be similar in p+p and heavy ion collisions. On the other hand, the thermal behaviour of the strange hadrons is qualitatively different in p+p as compared to A+A. We find an additional parameter accounting for non-equilibrium strangeness production is essential for describing the p+p data. This is in contrast to A+A where the non-equilibrium framework could be successfully replaced by a sequential and complete equilibrium model with an early freezeout of the strange hadrons.

   ↳ nucl-thnucl-exPRC(2017)·26 citations
6. 06*

   Single electrons from heavy-flavor mesons in relativistic heavy-ion collisions

   Taesoo Song🇩🇪 · Hamza Berrehrah🇩🇪 · Juan M. Torres-Rincon🇩🇪 · Laura Tolos🇩🇪 · Daniel Cabrera🇪🇸 · Wolfgang Cassing🇩🇪 · Elena Bratkovskaya🇩🇪

   We study the single electron spectra from $D-$ and $B-$meson semileptonic decays in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}=$200, 62.4, and 19.2 GeV by employing the parton-hadron-string dynamics (PHSD) transport approach that has been shown to reasonably describe the charm dynamics at RHIC and LHC energies on a microscopic level. In this approach the initial heavy quarks are produced by using the PYTHIA which is tuned to reproduce the FONLL calculations. The produced heavy quarks interact with off-shell massive partons in QGP with scattering cross sections which are calculated in the dynamical quasi-particle model (DQPM). At energy densities close to the critical energy density the heavy quarks are hadronized into heavy mesons through either coalescence or fragmentation. After hadronization the heavy mesons interact with the light hadrons by employing the scattering cross sections from an effective Lagrangian. The final heavy mesons then produce single electrons through semileptonic decay. We find that the PHSD approach well describes the nuclear modification factor $R_{\mathrm{AA}}$ and elliptic flow $v_2$ of single electrons in d+Au and Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}=$ 200 GeV and the elliptic flow in Au+Au reactions at $\sqrt{s_{\mathrm{NN}}}=$ 62.4 GeV from the PHENIX collaboration, however, the large $R_{\mathrm{AA}}$ at $\sqrt{s_{\mathrm{NN}}}=$ 62.4 GeV is not described at all. Furthermore, we make predictions for the $R_{\mathrm{AA}}$ of $D-$mesons and of single electrons at the lower energy of $\sqrt{s_{\mathrm{NN}}}=$ 19.2 GeV. Additionally, the medium modification of the azimuthal angle $\varphi$ between a heavy quark and a heavy antiquark is studied. We find that the transverse flow enhances the azimuthal angular distributions close to $\varphi =$ 0 because the heavy flavors strongly interact with nuclear medium in relativistic heavy-ion collisions and almost flow with the bulk matter.

   ↳ nucl-thnucl-exPRC(2017)·38 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.