Tue·Sep 27, 2011Tuesday·September 27, 2011

1. 01*

   Time-of-flight mass measurements for nuclear processes in neutron star crusts

   A. Estrade🇺🇸 · M. Matos🇺🇸 · H. Schatz🇺🇸 · A. M. Amthor🇺🇸 · D. Bazin🇺🇸 · M. Beard🇺🇸 · A. Becerril🇺🇸 · E. F. Brown🇺🇸 · R. Cyburt🇺🇸 · T. Elliot🇺🇸 · A. Gade🇺🇸 · D. Galaviz🇺🇸 and 14 other authors

   The location of electron capture heat sources in the crust of accreting neutron stars depends on the masses of extremely neutron-rich nuclei. We present first results from a new implementation of the time-of-flight technique to measure nuclear masses of rare isotopes at the National Superconducting Cyclotron Laboratory. The masses of 16 neutron-rich nuclei in the scandium -- nickel range were determined simultaneously, improving the accuracy compared to previous data in 12 cases. The masses of ${}^{61}${V}, ${}^{63}${Cr}, ${}^{66}${Mn}, and ${}^{74}${Ni} were measured for the first time with mass excesses of $-30.510(890)$ MeV, $-35.280(650)$ MeV, $-36.900(790)$ MeV, and $-49.210(990)$ MeV, respectively. With the measurement of the ${}^{66}$Mn mass, the locations of the two dominant electron capture heat sources in the outer crust of accreting neutron stars that exhibit superbursts are now experimentally constrained. We find that the location of the ${}^{66}$Fe${\to }^{66}$Mn electron capture transition occurs significantly closer to the surface than previously assumed because our new experimental Q-value is 2.1 MeV (2.6$\sigma$) smaller than predicted by the FRDM mass model.

   nucl-exastro-ph.SRPRL(2011)·45 citations
2. 02*

   Identified Particle Production from the BES at RHIC

   Lokesh Kumar (for the STAR Collaboration)🇺🇸

   The RHIC Beam Energy Scan focuses on the study of the QCD phase diagram --- temperature ($T$) vs. baryon chemical potential (${\mu }_B$). The aim is to verify some predictions from QCD: that a cross-over occurs at ${\mu }_B$ = 0, that there exists a first-order phase transition at large ${\mu }_B$ and a critical point at an intermediate ${\mu }_B$. The spectra and ratios of produced particles can be used to extract $T$ and ${\mu }_B$ in different energies and system sizes. The STAR experiment has collected data for Au+Au collisions at $\sqrt{s_{NN}}=$ 7.7 GeV, 11.5 GeV, and 39 GeV in the year 2010. We present midrapidity $p_T$ spectra, rapidity density, average transverse mass, and particle ratios for identified hadrons from the STAR experiment. The centrality and transverse momentum dependence of the particle yields and ratios are compared to existing data at lower and higher beam energies. The chemical and kinetic freeze-out conditions are extracted from the ratios and particle spectra.

   nucl-ex7 citations
3. 03*

   Two-pion Bose-Einstein correlations in Pb-Pb collisions at sqrt(s_NN) = 2.76 TeV measured with the ALICE experiment

   Johanna Lena Gramling (for the ALICE collaboration)🇨🇭

   The measurement of pion source radii in Pb-Pb collisions with the ALICE experiment at LHC is presented. By the analysis of Bose-Einstein enhancement in the correlation function of identical pions information on the size and evolution of the source region in space-time can be obtained. The source radii observed at LHC are larger than at RHIC, approximately scaling with the cube root of the particle multiplicity. A decrease of source radii with increasing pair momentum, indicating a collective expansion of the medium, was observed at RHIC and SPS and is also expected at LHC energies. The ALICE data confirm this and provide strict constraints on dynamical models describing the medium expansion. The results suggest that the created fireball has a higher temperature and a longer lifetime as compared to lower energies.

   nucl-exhep-exAIP Conf.Proc.(2012)·4 citations
4. 04*

   Reactor Simulation for Antineutrino Experiments using DRAGON and MURE

   C. L. Jones🇺🇸 · A. Bernstein🇺🇸 · J. M. Conrad🇺🇸 · Z. Djurcic🇺🇸 · M. Fallot🇫🇷 · L. Giot🇫🇷 · G. Keefer🇺🇸 · A. Onillon🇫🇷 · L. Winslow🇺🇸

   Rising interest in nuclear reactors as a source of antineutrinos for experiments motivates validated, fast, and accessible simulations to predict reactor fission rates. Here we present results from the DRAGON and MURE simulation codes and compare them to other industry standards for reactor core modeling. We use published data from the Takahama-3 reactor to evaluate the quality of these simulations against the independently measured fuel isotopic composition. The propagation of the uncertainty in the reactor operating parameters to the resulting antineutrino flux predictions is also discussed.

   nucl-exhep-exPRD(2012)·44 citations
5. 05*

   Directed and elliptic flow of charged particles in Cu+Cu collisions at $\sqrt{{\mathbf{s}}_{\mathbf{NN}}}=$ 22.4 GeV

   G. Agakishiev · M. M. Aggarwal · Z. Ahammed · A. V. Alakhverdyants · I. Alekseev · J. Alford · B. D. Anderson · C. D. Anson · D. Arkhipkin · G. S. Averichev · J. Balewski · D. R. Beavis and 360 other authors

   This paper reports results for directed flow $v_1$ and elliptic flow $v_2$ of charged particles in Cu+Cu collisions at $\sqrt{s_{NN}}=$ 22.4 GeV at the Relativistic Heavy Ion Collider. The measurements are for the 0-60% most central collisions, using charged particles observed in the STAR detector. Our measurements extend to 22.4 GeV Cu+Cu collisions the prior observation that $v_1$ is independent of the system size at 62.4 and 200 GeV, and also extend the scaling of $v_1$ with $\eta /y_{\mathrm{beam}}$ to this system. The measured $v_2(p_T)$ in Cu+Cu collisions is similar for $\sqrt{s_{NN}}=22.4-200$ GeV. We also report a comparison with results from transport model (UrQMD and AMPT) calculations. The model results do not agree quantitatively with the measured $v_1(\eta ),v_2(p_T)$ and $v_2(\eta )$.

   nucl-exPRC(2012)·44 citations
6. 06*

   Electromagnetic Calorimeter for HADES

   W. Czyzycki (1)🇵🇱 · E.Epple (2)🇩🇪 · L.Fabbietti (2)🇩🇪 · M.Golubeva (3)🇷🇺 · F.Guber (3)🇷🇺 · A.Ivashkin (3)🇷🇺 · M.Kajetanowicz (4)🇵🇱 · A.Krasa (5)🇨🇿 · F.Krizek (5)🇨🇿 · A.Kugler (5)🇨🇿 · K.Lapidus (2 and 3)🇩🇪 · E.Lisowski (1)🇵🇱 and 8 other authors

   We propose to build the Electromagnetic calorimeter for the HADES di-lepton spectrometer. It will enable to measure the data on neutral meson production from nucleus-nucleus collisions, which are essential for interpretation of dilepton data, but are unknown in the energy range of planned experiments (2-10 GeV per nucleon). The calorimeter will improve the electron-hadron separation, and will be used for detection of photons from strange resonances in elementary and HI reactions. Detailed description of the detector layout, the support structure, the electronic readout and its performance studied via Monte Carlo simulations and series of dedicated test experiments is presented. The device will cover the total area of about 8 m^2 at polar angles between 12 and 45 degrees with almost full azimuthal coverage. The photon and electron energy resolution achieved in test experiments amounts to 5-6%/sqrt(E[GeV]) which is sufficient for the eta meson reconstruction with S/B ratio of 0.4% in Ni+Ni collisions at 8 AGeV. A purity of the identified leptons after the hadron rejection, resulting from simulations based on the test measurements, is better than 80% at momenta above 500 MeV/c, where time-of-flight cannot be used.

   nucl-ex17 citations
7. 07*

   Femtoscopy of Pb-Pb and pp collisions at the LHC with the ALICE experiment

   A. Kisiel (for the ALICE collaboration)🇨🇭

   We report on the results of femtoscopic analysis of Pb-Pb collisions at sqrt(s_NN)=2.76 TeV and pp collisions at sqrt(s)=0.9, 2.76 and 7 TeV with identical pions and kaons. Detailed femtoscopy studies in heavy-ion collisions at SPS and RHIC have shown that emission region sizes ("HBT radii") decrease with increasing pair transverse momentum k_T, which is understood as a manifestation of the collective behavior of matter. The trend was predicted to persist at the LHC. The data from Pb-Pb collisions confirm the existence of a flowing medium and provide strict constraints on the dynamical models. Similar analysis is carried out for pp collisions for pions and kaons and qualitative similarities to heavy-ion data are seen, especially in collisions producing large number of particles. The observed trends give insight into the soft particle production mechanism in pp collisions. 3D radii were also found to universally scale with event multiplicity in heavy-ion collisions. We extend the range of multiplicities both upwards with the Pb-Pb data and downwards with the pp data to test the scaling in new areas. In particular the high multiplicity pp collisions reach particle densities comparable to the ones measured in peripheral Cu-Cu and Au-Au collisions at RHIC. This allows for the first time to directly compare freeze-out sizes for systems with very different initial states.

   nucl-exhep-exJ.Phys.G(2011)·11 citations
8. 08*

   Bulk viscosity, particle spectra and flow in heavy-ion collisions

   Kevin Dusling🇺🇸 · Thomas Schaefer🇺🇸

   We study the effects of bulk viscosity on pT spectra and elliptic flow in heavy ion collisions. For this purpose we compute the dissipative correction df to the single particle distribution functions in leading-log QCD, and in several simplified models. We consider, in particular, the relaxation time approximation and a kinetic model for the hadron resonance gas. We implement these distribution functions in a hydrodynamic simulation of Au + Au collisions at RHIC. We find significant corrections due to bulk viscosity in hadron pT spectra and the differential elliptic flow parameter v2(pT). These corrections are dominated by viscous corrections to the distribution function. We find that the relation between df and the bulk viscosity is different in the quark gluon plasma and hadronic phases. Reliable bounds on the bulk viscosity require accurate calculations of df in a hadronic resonance gas. Based on v2 spectra at RHIC we conservatively estimate zeta/s <= 0.05 near freeze-out. We also find that effects of the bulk viscosity on the pT integrated v2 are small.

   ↳ hep-phnucl-exnucl-thPRC(2012)·169 citations
9. 09*

   Measurement of reference cross sections in pp and Pb-Pb collisions at the LHC in van der Meer scans with the ALICE detector

   Martino Gagliardi (for the ALICE collaboration)🇮🇹

   Reference cross sections have been measured with the ALICE detector in both pp and Pb-Pb collisions, in dedicated luminosity calibration experiments (van der Meer scans) at the LHC. The results and their uncertainties are discussed, together with a few selected applications.

   ↳ hep-exnucl-exAIP Conf.Proc.(2012)·22 citations
10. 10*

    New results in exclusive hard reactions

    B. Pire🇫🇷 · K. Semenov-Tian-Shansky🇫🇷 · L. Szymanowski🇵🇱 · J. Wagner🇵🇱

    Generalized Parton Distributions offer a new way to access the quark and gluon nucleon structure. We review recent progress in this domain, emphasizing the need to supplement the experimental study of DVCS by its crossed version, timelike Compton scattering (TCS), where data at high energy should appear thanks to the study of ultraperipheral collisions at the LHC. This will open the access to very low skewness quark and gluon GPDs. Our leading order estimates show that the factorization scale dependence of the amplitudes is quite high. This fact demands the understanding of higher order contributions with the hope that they will stabilize this scale dependence. The magnitudes of the NLO coefficient functions are not small and neither is the difference of the coefficient functions appearing respectively in the DVCS and TCS amplitudes. The conclusion is that extracting the universal GPDs from both TCS and DVCS reactions requires much care. We also describe the extension of the GPD concept to three quark operators and the relevance of their nucleon to meson matrix elements, namely the transition distribution amplitudes (TDAs) which factorize in hard exclusive pion electroproduction off a nucleon in the backward region and baryon-antibaryon annihilation into a pion and a lepton pair. We discuss the main properties of the TDAs.

    ↳ hep-phhep-exnucl-exnucl-thPoS(2011)·0 citations
11. 11*

    The search for neutrinoless double beta decay

    J. J. Gomez-Cadenas🇪🇸 · J. Martin-Albo🇪🇸 · M. Mezzetto🇮🇹 · F. Monrabal🇪🇸 · M. Sorel🇪🇸

    In the last two decades the search for neutrinoless double beta decay has evolved into one of the highest priorities for understanding neutrinos and the origin of mass. The main reason for this paradigm shift has been the discovery of neutrino oscillations, which clearly established the existence of massive neutrinos. An additional motivation for conducting such searches comes from the existence of an unconfirmed, but not refuted, claim of evidence for neutrinoless double decay in ${}^{76}\text{Ge}$. As a consequence, a new generation of experiments, employing different detection techniques and $\beta \beta$ isotopes, is being actively promoted by experimental groups across the world. In addition, nuclear theorists are making remarkable progress in the calculation of the neutrinoless double beta decay nuclear matrix elements, thus eliminating a substantial part of the theoretical uncertainties affecting the particle physics interpretation of this process. In this report, we review the main aspects of the double beta decay process and some of the most relevant experiments. The picture that emerges is one where searching for neutrinoless double beta decay is recognized to have both far-reaching theoretical implications and promising prospects for experimental observation in the near future.

    ↳ hep-exhep-phnucl-exRiv.Nuovo Cim.(2012)·251 citations
12. 12*

    Production of charmed baryon ${\Lambda }_c(2940{)}^{+}$ at PANDA

    Jun He🇨🇳 · Zhen Ouyang🇨🇳 · Xiang Liu🇨🇳 · Xue-Qian Li🇨🇳

    In this work we evaluate the production rate of the charmed baryon ${\Lambda }_c(2940{)}^{+}$ at PANDA. For possible assignments of ${\Lambda }_c(2940{)}^{+}$: $J^P=1/2^{\pm }$, $3/2^{\pm }$ and $5/2^{\pm }$, the total cross section of $p\bar{p}\to {\bar{\Lambda }}_c{\Lambda }_c(2940{)}^{+}$ is estimated, which may exceed 1 nb. With the designed luminosity ($2\times 10^{-32}$cm${}^{-2}$/s) of PANDA, our estimate indicates that ten thousand events per day if ${\Lambda }_c(2940{)}^{+}$ is of $J^P=1/2^{+}$ or $10^8$ per day if it is of $J^P=5/2^{+}$ can be expected. Those values actually set the lower and upper limits of the ${\Lambda }_c(2940{)}^{+}$ production. In addition, we present the Dalitz plot and carry out a rough background analysis of the ${\Lambda }_c(2940{)}^{+}$ production in the $p\bar{p}\to D^{0}p{\bar{\Lambda }}_c$ and $p\bar{p}\to {\Sigma }_c^{0,++}{\pi }^{+,-}{\bar{\Lambda }}_c$ processes, which would provide valuable information for accurate determination of the ${\Lambda }_c(2940{)}^{+}$ identity.

    ↳ hep-phhep-exnucl-exnucl-thPRD(2011)·39 citations
13. 13*

    Medium-induced parton splitting kernels from Soft Collinear Effective Theory with Glauber gluons

    Grigory Ovanesyan🇺🇸 · Ivan Vitev🇺🇸

    We derive the splitting kernels for partons produced in large $Q^2$ scattering processes that subsequently traverse a region of strongly-interacting matter using a recently-developed effective theory \SCETG. We include all corrections beyond the small-$x$ approximation, consistent with the power counting of \SCETG. We demonstrate how medium recoil, geometry and expansion scenarios, and phase space cuts can be implemented numerically for phenomenological applications. For the simplified case of infinite transverse momentum kinematics and a uniform medium, we provide closed-form analytic results that can be used to validate the numerical simulations.

    ↳ hep-phnucl-exnucl-thPLB(2012)·111 citations
14. 14*

    The Nuclear Shell Model Toward the Drip Lines

    A. Poves🇪🇸 · E. Caurier🇫🇷 · F. Nowacki🇫🇷 · K. Sieja🇫🇷

    We describe the "islands of inversion" that occur when approaching the neutron drip line around the magic numbers N=20, N=28 and N=40 in the framework of the Interacting Shell Model in very large valence spaces. We explain these configuration inversions (and the associated shape transitions) as the result of the competition between the spherical mean field (monopole) which favors magicity and the correlations (multipole) which favor deformed intruder states. We also show that the N=20 and N=28 islands are in reallity a single one, which for the Magnesium isotopes is limited by N=18 and N=32.

    ↳ nucl-thnucl-exPhys.Scripta T(2012)·11 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.