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At least 181 records · Page 10Linked to original sources
arXiv2010

Calculations of Polarization Observables in Pseudoscalar Meson Photo-production Reactions

In preparation for the extraction of pseudoscalar meson photo-production amplitudes from a new generation of complete experiments, we assemble the relations between experimental observables and the Chew-Goldberger-Low-Nambu amplitudes. We present expressions that allow the direct calculation of matrix elements with arbitrary spin projections and uses these to clarify sign differences that exist in the literature. Comparing to the MAID and SAID analysis codes, we have found that the implied definitions of six double-polarization observables are the negative of what has been used in comparing to recent experimental data.

nucl-th↗
arXiv2010

Discovery of the Einsteinium Isotopes

Seventeen einsteinium isotopes have so far been observed; the discovery of these isotopes is discussed. For each isotope a brief summary of the first refereed publication, including the production and identification method, is presented.

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arXiv2015

Low-lying continuum states of drip-line Oxygen isotopes

Low-lying continuum states of exotic oxygen isotopes are studied, by introducing the Continuum-Coupled Shell Model (CCSM) characterized by an infinite wall placed very far and by an interaction for continuum coupling constructed in a close relation to realistic shell-model interaction. Neutron emission spectra from exotic oxygen isotopes are calculated by the doorway-state approach in heavy-ion multi-nucleon transfer reactions. The results agree with experiment remarkably well, as an evidence that the continuum effects are stronger than $\sim$1 MeV, consistently with the shell evolution in exotic nuclei. The results by this CCSM doorway-state approach are compared with calculations on neutron-scattering resonance peaks made within the CCSM phase-shift approach and also with those obtained in the Gamow shell model, by taking the same interaction. Remarkable similarities in peak energies and certain differences in widths are then obtained.

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arXiv2010

Free magnetized knots of parity-violating deconfined matter in heavy-ion collisions

We show that the local parity violation in the quark-gluon plasma supports existence of free (meta)stable knots of deconfined hot quark matter stabilized by superstrong magnetic fields. The magnetic field in the knots resembles the spheromak plasma state of the magnetic confinement approach to nuclear fusion. The size of the knot is quantized, being inversely proportional to the chiral conductivity of the quark-gluon plasma. The parity symmetry is broken inside the knot. Particles produced in the decays of the knots have unusual azimuthal distribution and specific flavor content. We argue that these knots may be created in noncentral heavy-ion collisions.

nucl-th↗
arXiv2013

Finite-size behavior near the critical point of QCD phase-transition

It is pointed out that finite-size effect is not negligible in locating critical point of QCD phase transition at current relativistic heavy ion collisions. Finite-size behavior near critical point, in particular, finite-size scaling and fixed-point behavior of the final observables can be served as a quantitative identification of critical point and the nearby boundary of the QCD phase transition. The validity of the method at finite detector acceptances at RHIC is discussed.

nucl-th↗
arXiv2010

Long term prospects for double beta decay

In rather general terms the long term perspective of double beta decay is discussed. All important experimental parameters are investigated as well as the status of nuclear matrix element issues. The link with other neutrino physics results and options to disentangle the underlying physics process are presented.

nucl-ex↗
arXiv2010

Charmonium mass in hot asymmetric nuclear matter

We calculate the in-medium masses of J/$ψ$ and of the excited states of charmonium ($ψ$(3686) and $ψ$(3770)) in isospin asymmetric nuclear matter at finite temperatures. These mass modifications arise due to the interaction of the charmonium states with the gluon condensates of QCD, simulated by a scalar dilaton field introduced to incorporate the broken scale invariance of QCD within an effective chiral model. The change in the mass of J/$ψ$ in the nuclear matter with density is seen to be rather small, as has been shown in the literature by using various approaches, whereas, the masses of the excited states of charmonium ($ψ$(3686) and $ψ$(3770)) are seen to have considerable drop at high densities. The dependence of the masses of the charmonium states on the isospin asymmetry has also been investigated in the hot nuclear matter and is seen to be appreciable at moderate temperatures and high densities. These medium modifications of the charmonium states should modify the experimental observables arising from the compressed baryonic matter produced in asymmetric heavy ion collision experiments in the future facility of FAIR, GSI.

nucl-th↗
arXiv2010

Inelastic neutron scattering: resonances and fluctuations

R-function theory of Thomas used in study of inelastic scattering of neutrons to a definite state. Onset of fluctuations, effects of randomness of phases of interfering amplitudes, and variations in statistical distributions of neutron widths considered in detail. Fluctuations exhibit well-defined maxima and sharp minima. For certain adjacent resonances, strong interference effects are predicted.

nucl-ex↗
arXiv2010

Nuclear Scaling and the EMC Effect

Results of recent EMC effect measurements and nuclear scaling measurements have both been attributed to local nuclear density effects and not properties of the bulk nuclear system. This lead us to the phenomenological observation that the ratio of the slopes in the 0.3 < x_B < 0.7 EMC data scale as the ratio of the x_B > 1 nuclear scaling plateaus. Using this correlation, we developed a phenomenological relation which reproduces the general trends and features of the EMC effect for nuclei from 3He to 56Fe.

hep-ph↗
arXiv2010

Measuring (n,f) cross-sections of short-lived states

In order to test theories of fission cross-sections, it is desirable to measure the (n,f) cross-sections of both an isomeric state and the ground state of the same isotope of the same element. This would test the ability to calculate effects that depend only on spin and parity without the confusion of effects that depend on (Z,A). At present there is no isotope for which the (n,f) cross-section has been measured successfully at MeV energies, where theoretical predictions can be made. There have been a few measurements of the cross-section U235m at thermal and cold energies. At these energies the cross-section is expected to be dominated by incalculable resonances, so that it may not be a useful test of theoretical predictions. I suggest methods for measuring the (n,f) cross-sections to neutrons with a fission spectrum of 1/2+ (26 m) isomeric U235m and of 1- (16 h) (shorter lived than the isomer) Am242gs.

nucl-ex↗
arXiv2010

Discovery of the Tin Isotopes

Thirty-eight tin isotopes have so far been observed; the discovery of these isotopes is discussed. For each isotope a brief summary of the first refereed publication, including the production and identification method, is presented.

nucl-ex↗
arXiv2010

Alpha-particle condensation in excited 12C

The fragmentation of quasi-projectiles from the nuclear reaction $^{40}Ca$+$^{12}C$ at 25 MeV/nucleon was used to produce excited states candidates to $α$-particle condensation. The methodology relies on high granularity 4$π$ detection coupled to correlation function techniques. Under the assumption that the equality among the kinetic energies of the emitted $α$-particles and the emission simultaneity constitutes a reliable fingerprint of $α$ condensation, we identify several tens of events corresponding to the deexcitation of the Hoyle state of $^{12}$C which fulfill the condition.

nucl-ex↗
arXiv2010

Discovery of the Calcium Isotopes

Twenty four calcium isotopes have so far been observed; the discovery of these isotopes is discussed. For each isotope a brief summary of the first refereed publication, including the production and identification method, is presented.

nucl-ex↗
arXiv2010

Discovery of the Indium Isotopes

Thirty-eight indium isotopes (A = 98-135) have so far been observed; the discovery of these isotopes is discussed. For each isotope a brief summary of the first refereed publication, including the production and identification method, is presented.

nucl-ex↗
arXiv2010

Chiral-odd transversity GPDs from a leading twist hard amplitude

The chiral-odd transversity generalized parton distributions (GPDs) of the nucleon can be accessed experimentally through the exclusive photoproduction process gamma + N -> pi + rho + N', in the kinematics where the meson pair has a large invariant mass and the final nucleon has a small transverse momentum, provided the vector meson is produced in a transversally polarized state. We calculate perturbatively the scattering amplitude at leading order in alpha_s. We build a simple model for the dominant transversity GPD H_T(x,xi,t) based on the concept of double distribution. We estimate the unpolarized differential cross section for this process in the kinematics of the Jlab and COMPASS experiments. Counting rates show that the experiment looks feasible with the real photon beam characteristics expected at JLab@12 GeV, and with the quasi real photon beam in the COMPASS experiment.

hep-ph↗
arXiv2011

Gallium experiments with artificial neutrino sources as a tool for investigation of transition to sterile states

We propose to place a very intense source of 51Cr at the center of a 50-tonne target of gallium metal that is divided into two concentric spherical zones and to measure the neutrino capture rate in each zone. This experiment can set limits on transitions from active to sterile neutrinos with Delta m^2 ~ 1 eV^2 with a sensitivity to disappearance of electron neutrinos of a few percent.

nucl-ex↗
arXiv2011

Solid oxygen as converter for the production of ultra-cold neutrons

We have investigated solid oxygen as a converter material for the production of ultra-cold neutrons. In a first series of experiments the crystal preparation was examined. An optically semi-transparent solid $α$-oxygen crystal has been prepared. In a second series of experiments such a crystal prepared indentically as in the first series of experiments has been exposed to the cold neutron flux of the MEPHISTO beam line of the FRM II. Ultra-cold neutrons produced inside the oxygen crystal have been extracted and the count rates have been measured at different converter temperatures. The results of these measurements give a clear signal of the superthermal UCN production mechanism in $α$-oxygen. The mean free loss length of UCN inside the crystal at a temperature of 5\,K was determined to be in the order of $20\,\mathrm{cm}$.

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