Tue·Aug 26, 2014Tuesday·August 26, 2014

1. 01*

   The fate of the weakly-bound $\psi (2s)$ in nuclear matter

   J. Matthew Durham (for the PHENIX Collaboration)🇺🇸

   We present new results of a completed PHENIX analysis of $\psi (2s)$ modification at midrapidity in 200 GeV $d+$Au collisions. Strong suppression of the $\psi (2s)$ relative to the $J/\psi$ is observed. This difference in suppression is too strong to be explained by breakup effects in the nucleus, due to the short nuclear crossing times at RHIC. Given the observation of long range correlations in $p(d)+$A collisions at LHC and RHIC, consistent with hydrodynamics, these observations raise interesting questions about the mechanism of $\psi (2s)$ suppression when it is produced in a nuclear target. In 2012, the PHENIX Collaboration installed the FVTX, a silicon tracker that precisely measures muon pair opening angles prior to any multiple scattering in the muon arm absorber, and thus provides an improved dimuon mass resolution. The FVTX allows the $\psi (2s)$ to be separated from the $J/\psi$ at forward and backward rapidity for the first time at RHIC. We present new results on $\psi (2s)$ production in $p+p$ collisions at $\sqrt{s}=510$ GeV from the 2013 data set.

   nucl-exNPA(2014)·1 citation
2. 02*

   Pygmy resonance and low-energy enhancement in the $\gamma$-ray strength functions of Pd~isotopes

   Tomas Kvalheim Eriksen🇳🇴 · Hilde-Therese Nyhus🇳🇴 · Magne Guttormsen🇳🇴 · Andreas Görgen🇳🇴 · Ann-Cecilie Larsen🇳🇴 · Therese Renstrøm🇳🇴 · Inger-Eli Ruud🇳🇴 · Sunniva Siem🇳🇴 · Heidi Kristine Toft🇳🇴 · Gry Merete Tveten🇳🇴 · Jonathan Wilson🇫🇷

   An unexpected enhancement in the $\gamma$-ray strength function, as compared to the low energy tail of the Giant Dipole Resonance (GDR), has been observed for Sc, Ti, V, Fe and Mo isotopes for $E_{\gamma }<4$ MeV. This enhancement was not observed in subsequent analyses on Sn isotopes, but a Pygmy Dipole Resonance (PDR) centered at $E_{\gamma }\approx 8$ MeV was however detected. The $\gamma$-ray strength functions measured for Cd isotopes exhibit both features over the range of isotopes, with the low-energy enhancement decreasing- and PDR strength increasing as a function of neutron number. This suggests a transitional region for the onset of low-energy enhancement, and also that the PDR strength depends on the number of neutrons. The $\gamma$-ray strength functions of ${}^{105-108}$Pd have been measured in order to further explore the proposed transitional region. Experimental data were obtained at the Oslo Cyclotron Laboratory by using the charged particle reactions (${}^3$He, ${}^3$He${}^{\prime }\gamma$) and (${}^3$He, $\alpha$$\gamma$) on ${}^{106,108}$Pd target foils. Particle$-\gamma$ coincidence measurements provided information on initial excitation energies and the corresponding $\gamma$-ray spectra, which were used to extract the level densities and $\gamma$-ray strength functions according to the Oslo method. The $\gamma$-ray strength functions indicate a sudden increase in magnitude for $E_{\gamma }>4$ MeV, which is interpreted as a PDR centered at $E_{\gamma }\approx 8$ MeV. An enhanced $\gamma$-ray strength at low energies is also observed for ${}^{105}$Pd, which is the lightest isotope measured in this work. Further, the results correspond and agree very well with the observations from the Cd isotopes, and support the suggested transitional region for the onset of low-energy enhancement with decreasing mass number. The neutron number dependency of the PDR strength is also evident.

   nucl-exPRC(2014)·20 citations
3. 03*

   Search for the deeply bound $K^{-}pp$ state from the semi-inclusive forward-neutron spectrum in the in-flight $K^{-}$ reaction on helium-3

   Tadashi Hashimoto · Shuhei Ajimura · George Beer · Hyoungchan Bhang · Mario Bragadireanu · Luigi Busso · Michael Cargnelli · Seonho Choi · Catalina Curceanu · Shun Enomoto · Diego Faso · Hiroyuki Fujioka and 55 other authors

   An experiment to search for the $K^{-}pp$ bound state was performed via the in-flight ${}^3$He($K^{-},n)$ reaction using 5.3 $\times$ $10^9$ kaons at 1 GeV/$c$ at the J-PARC hadron experimental facility. In the semi-inclusive neutron missing-mass spectrum at ${\theta }_n^{lab}=0^{\circ }$, no significant peak was observed in the region corresponding to $K^{-}pp$ binding energy larger than 80 MeV, where a bump structure has been reported in the $\Lambda p$ final state in different reactions. Assuming the state to be isotropically decaying into $\Lambda p$, mass-dependent upper limits on the production cross section were determined to be 30--180, 70--250, and 100--270 $\mu$b/sr, for the natural widths of 20, 60, and 100 MeV, respectively, at 95\% confidence level.

   nucl-exPTEP(2015)·61 citations
4. 04*

   ABC Effect and Resonance Structure in the Double-Pionic Fusion to ${}^3$He

   P. Adlarson🇸🇪 · W. Augustyniak🇵🇱 · W. Bardan🇵🇱 · M. Bashkanov🇩🇪 · F. S. Bergmann🇩🇪 · M. Berłowski🇵🇱 · H. Bhatt🇮🇳 · A. Bondar🇷🇺 · M. Büscher🇩🇪 · H. Calén🇸🇪 · I. Ciepał🇵🇱 · H. Clement🇩🇪 and 91 other authors

   Exclusive and kinematically complete measurements of the double pionic fusion to ${}^3$He have been performed in the energy region of the so-called ABC effect, which denotes a pronounced low-mass enhancement in the $\pi \pi$-invariant mass spectrum. The experiments were carried out with the WASA detector setup at COSY. Similar to the observations in the basic $pn\to d{\pi }^0{\pi }^0$ reaction and in the $dd{\to }^4$He${\pi }^0{\pi }^0$ reaction, the data reveal a correlation between the ABC effect and a resonance-like energy dependence in the total cross section. Differential cross sections are well described by the hypothesis of $d^{\ast }$ resonance formation during the reaction process in addition to the conventional $t$-channel $\Delta \Delta$ mechanism. The deduced $d^{\ast }$ resonance width can be understood from collision broadening due to Fermi motion of the nucleons in initial and final nuclei.

   nucl-exhep-exPRC(2015)·42 citations
5. 05*

   Charged Particle and Photon Multiplicity, and Transverse Energy Production in High-Energy Heavy-Ion Collisions

   Raghunath Sahoo🇮🇳 · Aditya Nath Mishra (IIT Indore, India)🇮🇳 · Nirbhay K. Behera🇮🇳 · Basanta K. Nandi (IIT Bombay, India)🇮🇳

   We review the charged particle and photon multiplicity, and transverse energy production in heavy-ion collisions starting from few GeV to TeV energies. The experimental results of pseudorapidity distribution of charged particles and photons at different collision energies and centralities are discussed. We also discuss the hypothesis of limiting fragmentation and expansion dynamics using the Landau hydrodynamics and the underlying physics. Meanwhile, we present the estimation of initial energy density multiplied with formation time as a function of different collision energies and centralities. In the end, the transverse energy per charged particle in connection with the chemical freeze-out criteria is discussed. We invoke various models and phenomenological arguments to interpret and characterize the fireball created in heavy-ion collisions. This review overall provides a scope to understand the heavy-ion collision data and a possible formation of a deconfined phase of partons via the global observables like charged particles, photons and the transverse energy measurement.

   nucl-exhep-exhep-phAdv.High Energy Phys.(2015)·27 citations
6. 06*

   Mean transverse mass of hadrons in proton-proton reactions

   V. Yu. Vovchenko🇺🇦 · D. V. Anchishkin🇺🇦 · M. I. Gorenstein🇺🇦

   An energy dependence of the mean transverse mass $⟨m_T⟩$ at mid-rapidity in proton-proton ($p+p$) reactions is studied within the ultra-relativistic quantum molecular dynamics (UrQMD). The UrQMD model predicts a nonmonotonous dependence of $⟨m_T⟩$ on collision energy for several hadron species: for ${\pi }^{+}$, $p$, $K^{+}$, and $\Lambda$ the mean transverse mass has a maximum at the center of mass energy region $5\le \sqrt{s}\le 8$ GeV. These results are a consequence of an interplay of two contributions: 1) excitations and decays of the baryonic resonances $N^{\ast }$ and $\Delta$; 2) excitations and decays of the baryonic strings. The UrQMD results do not show any nonmonotonous dependence of $⟨m_T⟩$ on $\sqrt{s}$ for ${\pi }^{-}$, $K^{-}$, and antiprotons. Whether a nonmonotonous dependence of $⟨m_T⟩$ at mid-rapidity on the collision energy for ${\pi }^{+}$, $p$, $K^{+}$, and $\Lambda$ is relevant for real $p+p$ interactions will be soon checked experimentally by the NA61/SHINE Collaboration.

   ↳ nucl-thnucl-exNPA(2015)·9 citations
7. 07*

   Neutron Density Distributions of Neutron-Rich Nuclei Studied with the Isobaric Yield Ratio Difference

   Chun-Wang Ma🇨🇳 · Xiao-Man Bai · Jiao Yu🇺🇸 · Hui-Ling Wei🇨🇳

   The isobaric yield ratio difference (IBD) between two reactions of similar experimental setups is found to be sensitive to nuclear density differences between projectiles. In this article, the IBD probe is used to study the density variation in neutron-rich ${}^{48}$Ca. By adjusting diffuseness in the neutron density distribution, three different neutron density distributions of ${}^{48}$Ca are obtained. The yields of fragments in the 80$A$ MeV ${}^{40,48}$Ca + ${}^{12}$C reactions are calculated by using a modified statistical abrasion-ablation model. It is found that the IBD results obtained from the prefragments are sensitive to the density distribution of the projectile, while the IBD results from the final fragments are less sensitive to the density distribution of the projectile.

   ↳ nucl-thnucl-exEPJA(2014)·15 citations
8. 08*

   Surface-integral formalism of deuteron stripping

   A. M. Mukhamedzhanov🇺🇸 · D. Y. Pang🇨🇳 · C. A. Bertulani🇺🇸 · A. S. Kadyrov

   The purpose of this paper is to develop an alternative theory of deuteron stripping to resonance states based on the surface integral formalism of Kadyrov et al. [Ann. Phys. 324, 1516 (2009)] and continuum-discretized coupled channels (CDCC). First we demonstrate how the surface integral formalism works in the three-body model and then we consider a more realistic problem in which a composite structure of target nuclei is taken via optical potentials. We explore different choices of channel wave functions and transition operators and show that a conventional CDCC volume matrix element can be written in terms of a surface-integral matrix element, which is peripheral, and an auxiliary matrix element, which determines the contribution of the nuclear interior over the variable $r_{nA}$. This auxiliary matrix element appears due to the inconsistency in treating of the $n-A$ potential: this potential should be real in the final state to support bound states or resonance scattering and complex in the initial state to describe $n-A$ scattering. Our main result is formulation of the theory of the stripping to resonance states using the prior form of the surface integral formalism and CDCC method. It is demonstrated that the conventional CDCC volume matrix element coincides with the surface matrix element, which converges for the stripping to the resonance state. Also the surface representation (over the variable $r_{nA}$ of the stripping matrix element enhances the peripheral part of the amplitude although the internal contribution doesn't disappear and increases with increase of the deuteron energy. We present calculations corroborating our findings for both stripping to the bound state and the resonance.

   ↳ nucl-thnucl-exPRC(2014)·9 citations
9. 09*

   Production of two hadrons in semi-inclusive Deep Inelatic Scattering

   Stephen Gliske🇺🇸 · Alessandro Bacchetta🇮🇹 · Marco Radici🇮🇹

   We present the general expression, in terms of structure functions, of the cross section for the production of two hadrons in semi-inclusive deep-inelastic scattering. We analyze this process including full transverse-momentum dependence up to subleading twist and check, where possible, the consistency with existing literature.

   ↳ hep-phhep-exnucl-exnucl-thPRD(2014)·42 citations
10. 10*

    Measurement of hadron composition in charged jets from pp collisions with the ALICE experiment

    Benjamin Andreas Hess (for the ALICE Collaboration)🇩🇪

    We report on the first measurement of the charged hadron composition in charged jets from pp collisions. The ALICE detector at the LHC was used to study charged pion, kaon and (anti-)proton production in jets. The results were extracted from $2\times 10^8$ minimum bias events at a centre-of-mass energy of $\sqrt{s}=7$ TeV. We present the transverse momentum ($p_{\mathrm{T}}$) spectra and reduced momentum spectra ($z^{\mathrm{ch}}\equiv p_{\mathrm{T}}^{\mathrm{track}}/p_{\mathrm{T},\mathrm{jet}}^{\mathrm{ch}}$) of $\pi$, K and p in charged jets with $p_{\mathrm{T},\mathrm{jet}}^{\mathrm{ch}}$ between 5 and 20 GeV/$c$. The measurements are compared to Monte Carlo calculations.

    ↳ hep-exnucl-ex9 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.