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At least 379 records · Page 21Linked to original sources
arXiv2013

Coulomb effects in cold fission from reactions 233U(nth,f) and 235U(nth,f)

The Coulomb effect hypothesis in cold fission, formerly used to interpret fluctuations in the curve of maximal total kinetic energy as a function of fragments mass, in reactions 233U(nth,f), 235U(nth,f) and 239Pu(nth,f), is confirmed by the preference for more asymmetrical charge splits observed in cold fragmentations. Several experimental results on reactions 233U(nth,f) and 235U(nth,f) show that, for two isobaric fragmentations with similar Q-values, the greater is the value of the kinetic energy of the fragments, the greater will be the probability of more asymmetric charge split.

nucl-ex↗
arXiv2013

Study of gamma cascades of 59Ni by thermal neutron reaction

The quantum properties are important to study nuclear structure. The energy, spin, parity, transition order are usually interesting to research. In this experiment, 59Ni is activated by thermal neutron on 3rd horizontal channel of Dalat nuclear Reactor.

nucl-ex↗
arXiv2013

Measurement of the 92,93,94,100Mo(g,n) reactions by Coulomb Dissociation

The Coulomb Dissociation (CD) cross sections of the stable isotopes 92,94,100Mo and of the unstable isotope 93Mo were measured at the LAND/R3B setup at GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt, Germany. Experimental data on these isotopes may help to explain the problem of the underproduction of 92,94Mo and 96,98Ru in the models of p-process nucleosynthesis. The CD cross sections obtained for the stable Mo isotopes are in good agreement with experiments performed with real photons, thus validating the method of Coulomb Dissociation. The result for the reaction 93Mo(g,n) is especially important since the corresponding cross section has not been measured before. A preliminary integral Coulomb Dissociation cross section of the 94Mo(g,n) reaction is presented. Further analysis will complete the experimental database for the (g,n) production chain of the p-isotopes of molybdenum.

astro-ph.IM↗
arXiv2013

Transverse target single-spin asymmetry in inclusive electroproduction of charged pions and kaons

Single-spin asymmetries were investigated in inclusive electroproduction of charged pions and kaons from transversely polarized protons at the HERMES experiment. The asymmetries were studied as a function of the azimuthal angle $ψ$ about the beam direction between the target-spin direction and the hadron production plane, the transverse hadron momentum relative to the direction of the incident beam, and the Feynman variable $x_F$. The $\sin(ψ)$ amplitudes are positive for positive pions and kaons, slightly negative for negative pions and consistent with zero for negative kaons, with particular transverse-momentum but weak $x_F$ dependences. Especially large asymmetries are observed for two small subsamples of events, where also the scattered electron was recorded by the spectrometer.

hep-ex↗
arXiv2013

First experimental research of low energy proton radiography

Proton radiography is a new scatheless diagnostic tool, and which provides a potential development direction for advanced hydrotesting. Recently a low energy proton radiography system has been developed at CAEP. This system has been designed to use 11MeV proton beam to radiograph thin static objects. This system consists of a proton cyclotron coupled to an imaging beamline. The design features and commissioning results of this radiography system are presented.

physics.acc-ph↗
arXiv2013

Implications of the ABC Resonance Structure on Elastic Neutron-Proton Scattering

In recent WASA-at-COSY measurements of the basic double-pionic fusion reactions $pn \to dπ^0π^0$ and $pn \to dπ^+π^-$ a narrow resonance structure with $I(J^P) = 0(3^+)$ in the total cross section has been found. If this constitutes a s-channel resonance in the $pn$ system, then it should cause distinctive consequences in $pn$ scattering. The magnitude of the decay width into the $pn$ channel is estimated and the expected resonance effects in integral and differential $pn$ scattering observables are presented. The inclusion of the resonance improves the description of total cross section data. For the analyzing power a characteristic energy dependence is predicted, which should allow a crucial experimental check of the resonance hypothesis.

nucl-ex↗
arXiv2013

Development of a microtpc detector as a standard instrument for low energy neutron field characterization

In order to measure energy and fluence of neutron fields, with energy ranging from 8 keV to 1 MeV, a new primary standard is being developed at the IRSN (Institute for Radioprotection and Nuclear Safety). This project, micro-TPC (Micro Time Projection Chamber), carried out in collaboration with the LPSC, is based on the nucleus recoil detector principle. The measurement strategy requires track reconstruction of recoiling nuclei down to a few keV, which can be achieved with a low pressure gaseous detector using a micro-pattern gaseous detector. A gas mixture, mainly isobutane, is used as a n-p converter to detect neutrons into the detection volume. Then electrons, coming from the ionization of the gas by the proton recoil, are collected by the pixelised anode (2D projection). A self-triggered electronics is able to perform the anode readout at a 50 MHz frequency in order to give the third dimension of the track. Then the scattering angle is deduced from this track using algorithms. The charge collection leads to the proton energy, taking into account the ionization quenching factor. This article emphasizes the neutron energy measurements of a monoenergetic neutron field produced at 127 keV. The measurements are compared to Monte Carlo simulations using realistic neutron fields and simulations of the detector response. The discrepancy between experiments and simulations is 5 keV mainly due to the calibration uncertainties of 10%.

physics.ins-det↗
arXiv2013

Studying the high x frontier with A Fixed-Target ExpeRiment at the LHC

The opportunities which are offered by a next generation and multi-purpose fixed-target experiment exploiting the proton and lead LHC beams extracted by a bent crystal are outlined. In particular, such an experiment can greatly complement facilities with lepton beams by unraveling the partonic structure of polarised and unpolarised nucleons and of nuclei, especially at large momentum fractions.

hep-ex↗
arXiv2013

Models for exclusive vector meson production in heavy-ion collisions

We discuss coherent and incoherent photoproduction of $J/Ψ$ vector mesons in high energy heavy ion collisions. In a dipole picture for the photon both can be naturally related to the dipole cross section that is also probed in inclusive DIS. We compare results of a particular calculation to ALICE data.

hep-ph↗
arXiv2013

Latest RHIC Results on Ultra-Peripheral Collisions

With RHIC running in its second phase at higher luminosities the new data sets collected so far by PHENIX and STAR are allowing improvements in the study of vector meson photo-production in Ultra peripheral Collision events in Au+Au at the highest energy. This is a brief summary of what has been accomplished so far by both collaborations.

hep-ex↗
arXiv2013

Photon neutrino-production in a chiral EFT for nuclei and extrapolation to $E_ν\sim$ GeV region

We carry out a series of studies on pion and photon productions in neutrino/electron/photon--nucleus scatterings. The low energy region is investigated by using a chiral effective field theory for nuclei. The results for the neutral current induced photon production ($γ$-NCP) are then extrapolated to neutrino energy $E_ν\sim$ GeV region. By convoluting the cross sections with MiniBooNE's beam spectrum and detection efficiency, we estimate its $γ$-NCP, event number, and conclude that such photon production can not fully explain its low energy event excess in both neutrino and antineutrino runs.

nucl-th↗
arXiv2013

Results on ultra-peripheral interactions in Pb-Pb and p-Pb collisions in ALICE

Ultra-relativistic heavy ions generate strong electromagnetic fields which offer the possibility to study $γ$-nucleus and $γ$-proton interactions at the LHC in the so called ultra-peripheral collisions (UPC). Here we report ALICE results on J/psi photoproduction measured in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV and in p-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV.

hep-ex↗
arXiv2013

Long-range and short-range multiparticle correlation in collisions of $_{79}Au^{197}$ 10.7 A GeV with photoemulsion nuclei

A search and research of long-range and short-range multiparticle correlations in pseudorapidity distribution of secondary particles on the base of analysis of individual interaction of nuclei of $^{197}Au$ at energy 10.7 AGeV with photoemulsion nuclei, is carried out. Events with long-range multiparticle correlations (LC), short-range multiparticle correlations (SC) and mixed type (MT) in pseudorapidity distribution of secondary particles, are selected by Hurst method in accordance of Hurst curve behavior. These types have significantly different characteristics. At first, they have different parameters of fragmentation. Events of LC type are processes of full destruction of projectile nucleus, in which multicharge fragments are absent. In events of mixed type several multicharge fragments of projectile nucleus are discovered. Secondly, these two types have significantly different multiplicity distribution. Mean multiplicity of LC type events is significantly more than in events of mixed type. On the basis of research of dependence of multiplicity versus target-nuclei fragments number for events of various types it is revealed, that the most considerable multiparticle correlations are observed in interactions of mixed type, which correspond to the central collisions of gold nuclei and nuclei of CNO-group, i.e. nuclei with strongly asymmetric volume, nuclear mass, charge, etc. Such events are characterised by full destruction of target-nucleus and disintegration of projectile-nucleus on several multi-charged fragments.

nucl-th↗
arXiv2013

Search for narrow six-quark states in the reactions $γd\to πγnn$

We study the reactions $γd\toπγNN$ with the aim to search for six-quark states, the decay of which into two nucleons is forbidden by the Pauli exclusion principle. These states with the masses $M<2m_N+m_π$ should mainly decay by emitting a photon. This is a new class of metastable six-quark states with the decay widths $<< 1$keV. The recent experiment at Proton Linear Accelerator of INR (Moscow) suggests a possibility of the existence of such states with masses 1904, 1926, and 1942 MeV. The proposed experiment at MAMI-C could provide an unique opportunity to observe such dibaryon states in mass region up to 2000 MeV and determine their masses and quantum numbers.

nucl-ex↗
arXiv2013

The yields of different states of Delta(1232) in neutrino-induced reactions at E_ν= 10 GeV

First experimental data on the inclusive yields of Delta^{0}(1232) and Delta^{+}(1232) isobars in neutrino-induced reactions are obtained. Their total yields in neutrino-nucleon interactions, 0.145+-0.055 and 0.182+-0.054, respectively, exceed the value of 0.091+-0.015 obtained recently for the Delta^{++}(1232) state. The data for the all three states of Delta(1232) cannot be reproduced by the LEPTO6.5 model. The fractions of π^0, π^- and π^+ mesons originating from the decay of lightest baryonic and mesonic resonances are estimated to be, respectively 56.6+-9.6%, 39.5+-6.6% and 27.7+-3.2%.

nucl-ex↗
arXiv2013

Large x physics: recent results and future plans

The valence region is exceedingly important in hadron physics since this region not only defines a hadron but also is an excellent discriminator of nucleon structure models. Present uncertainties in light quark distribution functions at high x could also impact high energy physics. Here we will describe a new generation of experiments at Jefferson Lab that is aimed at the high x region of the nucleon. It is noted that the proposed Electron Ion Collider could explore the high x regime.

nucl-ex↗
arXiv2013

Acoustic scaling of anisotropic flow in shape-engineered events: implications for extraction of the specific shear viscosity of the quark gluon plasma

It is shown that the acoustic scaling patterns of anisotropic flow for different event shapes at a fixed collision centrality (shape-engineered events), provide robust constraints for the event-by-event fluctuations in the initial-state density distribution from ultrarelativistic heavy ion collisions. The empirical scaling parameters also provide a dual-path method for extracting the specific shear viscosity $(η/s)_\mathrm{QGP}$ of the quark-gluon plasma (QGP) produced in these collisions. A calibration of these scaling parameters via detailed viscous hydrodynamical model calculations, gives $(η/s)_\mathrm{QGP}$ estimates for the plasma produced in collisions of Au+Au ($\sqrt{s_{NN}}= 0.2$ TeV) and Pb+Pb ($\sqrt{s_{NN}}= 2.76$ TeV). The estimates are insensitive to the initial-state geometry models considered.

nucl-ex↗