Thu·Sep 4, 2014Thursday·September 4, 2014

1. 01*

   Search for dark photons from neutral meson decays in $p$$+$$p$ and $d$$+$Au collisions at $\sqrt{s_{{}_{NN}}}$=200 GeV

   A. Adare🇺🇸 · S. Afanasiev🇷🇺 · C. Aidala🇺🇸 · N.N. Ajitanand🇺🇸 · Y. Akiba🇯🇵 · R. Akimoto🇯🇵 · H. Al-Bataineh🇺🇸 · H. Al-Ta'ani🇺🇸 · J. Alexander🇺🇸 · M. Alfred🇺🇸 · K.R. Andrews🇺🇸 · A. Angerami🇺🇸 and 569 other authors

   The standard model (SM) of particle physics is spectacularly successful, yet the measured value of the muon anomalous magnetic moment $(g-2{)}_{\mu }$ deviates from SM calculations by 3.6$\sigma$. Several theoretical models attribute this to the existence of a "dark photon," an additional U(1) gauge boson, which is weakly coupled to ordinary photons. The PHENIX experiment at the Relativistic Heavy Ion Collider has searched for a dark photon, $U$, in ${\pi }^0,\eta \to \gamma e^{+}{e}^{-}$ decays and obtained upper limits of $\mathcal{O}(2\times 10^{-6})$ on $U$-$\gamma$ mixing at 90% CL for the mass range $30<m_U<90$ MeV/$c^2$. Combined with other experimental limits, the remaining region in the $U$-$\gamma$ mixing parameter space that can explain the $(g-2{)}_{\mu }$ deviation from its SM value is nearly completely excluded at the 90% confidence level, with only a small region of $29<m_U<32$ MeV/$c^2$ remaining.

   nucl-exPRC(2015)·96 citations
2. 02*

   Origin of fine structure of the giant dipole resonance in sd-shell nuclei

   R. W. Fearick (1)🇿🇦 · B. Erler (2) · H. Matsubara (3,4)🇯🇵 · P. von Neumann-Cosel (2)🇩🇪 · A. Richter (2)🇩🇪 · R. Roth (2)🇩🇪 · A. Tamii (3) ((1) Department of Physics, University of Cape Town, (2) Institut für Kernphysik, Technische Universität Darmstadt, (3) Research Center for Nuclear Physics, Osaka University, (4) National Institute of Radiological Sciences)🇯🇵

   A set of high resolution zero-degree inelastic proton scattering data on 24Mg, 28Si, 32S, and 40Ca provides new insight into the long-standing puzzle of the origin of fragmentation of the Giant Dipole Resonance (GDR) in sd-shell nuclei. Understanding is provided by state-of-the-art theoretical Random Phase Approximation (RPA) calculatios for deformed nuclei using for the first time a realistic nucleon-nucleon interaction derived from the Argonne V18 potential with the unitary correlation operator method and supplemented by a phenomenological three-nucleon contact interaction. A wavelet analysis allows to extract significant scales both in the data and calculations characterizing the fine structure of the GDR. The fair agreement supports that the fine structure arises from ground-state deformation driven by alpha clustering.

   nucl-exnucl-thPRC(2018)·19 citations
3. 03*

   Experimental access to Transition Distribution Amplitudes with the P̄ANDA experiment at FAIR

   PANDA Collaboration: B.P. Singh · W. Erni · I. Keshelashvili · B. Krusche · M. Steinacher % · B. Liu · H. Liu · Z. Liu · X. Shen · C. Wang · J. Zhao % · M. Albrecht and 523 other authors

   Baryon-to-meson Transition Distribution Amplitudes (TDAs) encoding valuable new information on hadron structure appear as building blocks in the collinear factorized description for several types of hard exclusive reactions. In this paper, we address the possibility of accessing nucleon-to-pion ($\pi N$) TDAs from $\bar{p}p\to e^{+}{e}^{-}{\pi }^0$ reaction with the future P̄ANDA detector at the FAIR facility. At high center of mass energy and high invariant mass squared of the lepton pair $q^2$, the amplitude of the signal channel $\bar{p}p\to e^{+}{e}^{-}{\pi }^0$ admits a QCD factorized description in terms of $\pi N$ TDAs and nucleon Distribution Amplitudes (DAs) in the forward and backward kinematic regimes. Assuming the validity of this factorized description, we perform feasibility studies for measuring $\bar{p}p\to e^{+}{e}^{-}{\pi }^0$ with the P̄ANDA detector. Detailed simulations on signal reconstruction efficiency as well as on rejection of the most severe background channel, i.e. $\bar{p}p\to {\pi }^{+}{\pi }^{-}{\pi }^0$ were performed for the center of mass energy squared $s=5$ GeV${}^2$ and $s=10$ GeV${}^2$, in the kinematic regions $3.0<q^2<4.3$ GeV${}^2$ and $5<q^2<9$ GeV${}^2$, respectively, with a neutral pion scattered in the forward or backward cone $|\cos {\theta }_{{\pi }^0}|>0.5$ in the proton-antiproton center of mass frame. Results of the simulation show that the particle identification capabilities of the P̄ANDA detector will allow to achieve a background rejection factor of $5\cdot 10^7$ ($1\cdot 10^7$) at low (high) $q^2$ for $s=5$ GeV${}^2$, and of $1\cdot 10^8$ ($6\cdot 10^6$) at low (high) $q^2$ for $s=10$ GeV${}^2$, while keeping the signal reconstruction efficiency at around $40\%$. At both energies, a clean lepton signal can be reconstructed with the expected statistics corresponding to $2$ fb${}^{-1}$ of integrated luminosity. (.../...)

   ↳ hep-exhep-phnucl-exEPJA(2015)·51 citations
4. 04*

   The $D_{sJ}^{\ast }(2860)$ Mesons as Excited D-wave $c\bar{s}$ States

   Stephen Godfrey🇨🇦 · Kenneth Moats (Carleton University)🇨🇦

   A new charm-strange meson, the $D_{s1}^{\ast }(2863)$, has recently been observed by the LHCb collaboration which also determined the $D_{sJ}^{\ast }(2860)$ to have spin 3. One of the speculations about the previously observed $D_{s1}^{\ast }(2710)$ is that it is the $1^3{D}_1(c\bar{s})$ state. In this paper we reexamine the quark model properties and assignments of these three states in light of these new measurements. We conclude that the $D_{s1}^{\ast }(2863)$ and $D_{s3}^{\ast }(2863)$ are the $1^3{D}_1(c\bar{s})$ and $1^3{D}_3(c\bar{s})$ states respectively and the $D_{s1}^{\ast }(2710)$ is the $2^3{S}_1(c\bar{s})$ state. In addition to these three states there are another three excited $D_s$ states in this mass region still to be found; the $2^1{S}_0$ and two $1D_2$ states. We calculate the properties of these states and expect that LHCb has the capability of observing these states in the near future.

   ↳ hep-phhep-exnucl-exnucl-thPRD(2014)·45 citations
5. 05*

   Particle-number projection method in time-dependent Hartree-Fock theory: Properties of reaction products

   Kazuyuki Sekizawa🇯🇵 · Kazuhiro Yabana🇯🇵

   Background: The time-dependent Hartree-Fock (TDHF) theory has been successful in describing low-energy heavy ion collisions. Recently, we have shown that multinucleon transfer processes can be reasonably described in the TDHF theory combined with the particle-number projection technique. Purpose: In this work, we propose a theoretical framework to analyze properties of reaction products in TDHF calculations. Methods: TDHF calculation in three-dimensional Cartesian grid representation combined with particle number projection method. Results: We develop a theoretical framework to calculate expectation values of operators in the TDHF wave function after collision with the particle-number projection. To show how our method works in practice, the method is applied to ${}^{24}$O+${}^{16}$O collisions for two quantities, angular momentum and excitation energy. The analyses revealed following features of the reaction: The nucleon removal proceeds gently, leaving small values of angular momentum and excitation energy in nucleon removed nuclei. Contrarily, nuclei receiving nucleons show expectation values of angular momentum and excitation energy which increase as the incident energy increases. Conclusions: We have developed a formalism to analyze properties of fragment nuclei in the TDHF theory combined with the particle-number projection technique. The method will be useful for microscopic investigations of reaction mechanisms in low-energy heavy ion collisions as well as for evaluating effects of particle evaporation on multinucleon transfer cross sections.

   ↳ nucl-thnucl-exPRC(2014)·53 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.