Fri·Mar 13, 2015Friday·March 13, 2015

1. 01*

   Spectroscopy of ${\eta }^{\prime }$-nucleus bound states at GSI and FAIR --- very preliminary results and future prospects ---

   H. Fujioka🇯🇵 · Y. Ayyad🇯🇵 · J. Benlliure🇪🇸 · K.-T. Brinkmann🇩🇪 · S.Friedrich🇩🇪 · H. Geissel🇩🇪 · J. Gellanki🇳🇱 · C. Guo🇨🇳 · E. Gutz🇩🇪 · E. Haettner🇩🇪 · M.N. Harakeh🇳🇱 · R.S. Hayano🇯🇵 and 42 other authors

   The possible existence of \eta'-nucleus bound states has been put forward through theoretical and experimental studies. It is strongly related to the \eta' mass at finite density, which is expected to be reduced because of the interplay between the $U_A(1)$ anomaly and partial restoration of chiral symmetry. The investigation of the C(p,d) reaction at GSI and FAIR, as well as an overview of the experimental program at GSI and future plans at FAIR are discussed.

   nucl-exnucl-thHyperfine Interact.(2015)·10 citations
2. 02*

   Recent results on Bose-Einstein correlations by the PHENIX Experiment

   Mate Csanad (for the PHENIX Collaboration)🇭🇺

   Bose-Einstein momentum correlation functions of identical bosons reveal the shape and size of the (soft) particle emitting source of the given particle. The widths of these correlation functions are called HBT radii, named after Brown and Twiss who studied the angular diameter of stars via intensity correlations in their radio telescopes. Today, high energy physics experiments measure the HBT radii as a function of many parameters: particle type, transverse momentum, azimuthal angle, collision energy, collision geometry. In this paper we present results from the RHIC PHENIX experiment. These include the observation of strong azimuthal-angle dependence of the extracted Gaussian HBT radii, the similarities and differences between kaon and pion HBT radii. The key point of this paper is the application of Bose-Einstein correlations to the search for the critical point: how HBT radii would show the appearance of a first order phase transition, and what the non-monotonic collision energy dependence of the pion source tells us about the critical point; and how the non-Gaussian shape of correlation functions is related to one of the critical exponents.

   nucl-exPoS(2015)·0 citations
3. 03*

   Microscopic analysis of fusion hindrance in heavy systems

   Kouhei Washiyama🇯🇵

   Background: Heavy-ion fusion reactions involving heavy nuclei at energies around the Coulomb barrier exhibit fusion hindrance, where the probability of compound nucleus formation is strongly hindered compared with that in light- and medium-mass systems. The origin of this fusion hindrance has not been well understood from a microscopic point of view. Purpose: Analyze the fusion dynamics in heavy systems by a microscopic reaction model and understand the origin of the fusion hindrance. Method: We employ the time-dependent Hartree-Fock (TDHF) theory. We extract nucleus--nucleus potential and energy dissipation by the method combining TDHF dynamics of the entrance channel of fusion reactions with one-dimensional Newton equation including a dissipation term. Then, we analyze the origin of the fusion hindrance using the properties of the extracted potential and energy dissipation. Results: Extracted potentials show monotonic increase as the relative distance of two nuclei decreases, which induces the disappearance of an ordinary barrier structure of the potential. This is different from those in light- and medium-mass systems and from density-constraint TDHF calculations. Extracted friction coefficients show sizable energy dependence and universal value of their magnitude, which are rather similar to those in light- and medium-mass systems. Using these properties, we analyze the origin of the fusion hindrance and find that contribution of the increase in potential to the extra-push energy is larger than that of the accumulated dissipation energy in most systems studied in this article. Conclusions: By the analysis of the origin of the fusion hindrance, we conclude that, as the system becomes heavier, the dynamical increase in potential at small relative distances plays a more important role than the dissipation during the fusion reaction for understanding the origin of the fusion hindrance.

   ↳ nucl-thnucl-exPRC(2015)·31 citations
4. 04*

   Realistic estimate of valence transversity distributions from inclusive dihadron production

   Marco Radici🇮🇹 · A. Courtoy🇧🇪 · Alessandro Bacchetta🇮🇹 · Marco Guagnelli🇮🇹

   We present an updated extraction of the transversity parton distribution based on the analysis of pion-pair production in deep-inelastic scattering off transversely polarized targets in collinear factorization. Data for proton and deuteron targets make it possible to perform a flavor separation of the valence components of the transversity distribution, using di-hadron fragmentation functions taken from the semi-inclusive production of two pion pairs in back-to-back jets in e+e- annihilation. The e+e- data from Belle have been reanalyzed using the replica method and a more realistic estimate of the uncertainties on the chiral-odd interference fragmentation function has been obtained. Then, the transversity distribution has been extracted by using the most recent and more precise COMPASS data for deep-inelastic scattering off proton targets. Our results represent the most accurate estimate of the uncertainties on the valence components of the transversity distribution currently available.

   ↳ hep-phhep-exnucl-exnucl-thJHEP(2015)·151 citations
5. 05*

   Measurement of very forward neutron energy spectra for 7 TeV proton--proton collisions at the Large Hadron Collider

   O. Adriani🇮🇹 · E. Berti🇮🇹 · L. Bonechi🇮🇹 · M. Bongi🇮🇹 · G. Castellini🇮🇹 · R. D'Alessandro🇮🇹 · M. Del Prete🇮🇹 · M. Haguenauer🇫🇷 · Y. Itow🇯🇵 · K. Kasahara🇯🇵 · K. Kawade🇯🇵 · Y. Makino🇯🇵 and 19 other authors

   The Large Hadron Collider forward (LHCf) experiment is designed to use the LHC to verify the hadronic-interaction models used in cosmic-ray physics. Forward baryon production is one of the crucial points to understand the development of cosmic-ray showers. We report the neutron-energy spectra for LHC $\sqrt{s}$ = 7 TeV proton--proton collisions with the pseudo-rapidity $\eta$ ranging from 8.81 to 8.99, from 8.99 to 9.22, and from 10.76 to infinity. The measured energy spectra obtained from the two independent calorimeters of Arm1 and Arm2 show the same characteristic feature before unfolding the difference in the detector responses. We unfolded the measured spectra by using the multidimensional unfolding method based on Bayesian theory, and the unfolded spectra were compared with current hadronic-interaction models. The QGSJET II-03 model predicts a high neutron production rate at the highest pseudo-rapidity range similar to our results and the DPMJET 3.04 model describes our results well at the lower pseudo-rapidity ranges. However no model perfectly explains the experimental results in the whole pseudo-rapidity range. The experimental data indicate the most abundant neutron production rate relative to the photon production, which does not agree with predictions of the models.

   ↳ hep-exnucl-exPLB(2015)·85 citations
6. 06*

   Feasibility Study of Gas Electron Multiplier Detector as an X-Ray Image Sensor

   Sukyoung Shin🇰🇷 · Jaehoon Jung🇰🇷 · Soonhyouk Lee🇰🇷

   For its ease manufacturing, flexible geometry, and cheap manufacturing cost, the gas electron multiplier (GEM) detector can be used as an x-ray image sensor. For this purpose, we acquired relative detection efficiencies and suggested a method to increase the detection efficiency in order to study the possibility of GEM detector as an x-ray image sensor. The GEM detector system is composed of GEM foils, the instrument system, the gas system, and the negative power supply. The instrument system consists of the A225 charge sensitive preamp, A206 discriminator, and MCA8000D multichannel analyzer. For the gas system, Argon gas was mixed with CO2 to the ratio of 8:2, and for the negative 2,000 volts, the 3106D power supply was used. The CsI-coated GEM foil was used to increase the detection efficiency. Fe-55 was used as an x-ray source and the relative efficiency was acquired by using the ratio of GEM detector to the CdTe detector. The total count method and the energy spectrum method were used to calculate the relative efficiency. The relative detection efficiency of GEM detector for Fe-55 by using total count method was 32 % and by using energy spectrum method, the relative efficiencies were 5, 43, 33, 37, 35, and 36 % respectively according to the energy spectrum of 2, 3, 4, 5, 6, and 7 KeV. In conclusion, we found that the detection efficiency of the two layered GEM detector is insufficient for the x-ray image sensor, so we suggested a CsI coated GEM foil to increase the efficiency rate and the result value was increased to 41 %.

   ↳ physics.ins-dethep-exnucl-exJ.Korean Phys.Soc.(2015)·0 citations
7. 07*

   Rapidity dependence of elliptic and triangular flow in proton-nucleus collisions from collective dynamics

   Piotr Bozek🇵🇱 · Adam Bzdak🇵🇱 · Guo-Liang Ma🇨🇳

   The rapidity dependence of elliptic, $v_2$, and triangular, $v_3$, flow coefficients in proton-nucleus (p+A) collisions is predicted in hydrodynamics and in a multi-phase transport model (AMPT). We find that $v_n$ ($n=2,3$) on a nucleus side is significantly larger than on a proton side and the ratio between the two, $v_n^{\mathrm{Pb}}/v_n^{\mathrm{p}}$, weekly depends on the transverse momentum of produced particles.

   ↳ hep-phhep-exnucl-exnucl-thPLB(2015)·64 citations
8. 08*

   Forward hadron production in ultraperipheral proton-heavy-ion collisions at the LHC and RHIC

   Gaku Mitsuka🇮🇹

   We discuss hadron production in the forward rapidity region in ultraperipheral proton-lead collisions at the LHC and proton-gold collisions at RHIC. Our discussion is based on the Monte Carlo simulations of the interactions of virtual photons emitted by a fast moving nucleus with a proton beam. We simulate the virtual photon flux with the STARLIGHT event generator and then particle production with the SOPHIA, DPMJET, and PYTHIA event generators. We show the rapidity distributions of charged and neutral particles, and the momentum distributions of neutral pions and neutrons at forward rapidities. According to the Monte Carlo simulations, we find large cross sections of ultraperipheral collisions for particle production especially in the very forward region, leading to substantial background contributions to investigations of collective nuclear effects and spin physics. Finally we can distinguish between proton-nucleus inelastic interactions and ultraperipheral collisions with additional requirements of either of the charged particles at midrapidity and a certain level of activities at negative forward rapidity.

   ↳ hep-phhep-exnucl-exEPJC(2015)·14 citations
9. 09*

   Scintillation characteristics of undoped and Cu+-doped Li2B4O7 single crystals

   Masaaki Kobayashi · Mitsuru Ishii · Nachimuthu Senguttuvan

   Scintillation characteristics of undoped and Cu+-doped lithium tetraborate Li2B4O7 (LTB) were studied including optical transmittance, photoluminescence, radioluminescence for X- and gamma-rays, alpha/gamma ratio, and decay kinetics. The total time-integrated LYs in undoped and Cu+-doped LTB for X-rays are ~600 and ~760 ph/MeV (photons/MeV), respectively. The decay kinetics in undoped and Cu+-doped LTB are similar to each other. Typical decay spectra for pulsed X-rays can be fitted with four exponentials: for fast (t1~0.8 ns, t2~25-50 ns), medium (t3~300-400 ns), and slow (t4~20-30 ms) components. The slow component occupies about 60% of the total LY, while the fast ones less than 10%. The 10-90% rise time was 163 ps. The alpha/gamma ratio was 0.18 for external 241Am alpha-rays. The obtained increase in LY due to Cu+ doping remains modest. The Cu+-induced emission contains both fast and slow components, requiring further studies of the emission mechanism to explain the fast component.

   ↳ physics.ins-detnucl-exProblemy Spektroskopii i Spektrometrii (P…·0 citations
10. 10*

    Proton-${}^3$H scattering calculation: Elastic and charge-exchange reactions up to 30 MeV

    A. Deltuva🇱🇹 · A. C. Fonseca🇵🇹

    Proton-${}^3$H elastic scattering and charge-exchange reaction ${}^3$H$(p,n){}^3$He in the energy regime above four-nucleon breakup threshold are described in the momentum-space transition operator framework. Fully converged results are obtained using realistic two-nucleon potentials and two-proton Coulomb force as dynamic input. Differential cross section, proton analyzing power, outgoing neutron polarization, and proton-to-neutron polarization transfer coefficients are calculated between 6 and 30 MeV proton beam energy. Good agreement with the experimental data is found for the differential cross section both in elastic and charge-exchange reactions; the latter shows a complicated energy and angular dependence. The most sizable discrepancies between predictions and data are found for the proton analyzing power and outgoing neutron polarization in the charge-exchange reaction, while the respective proton-to-neutron polarization transfer coefficients are well described by the calculations.

    ↳ nucl-thnucl-exPRC(2015)·14 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.