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At least 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Exclusive single pion electroproduction off the proton in the invariant mass range up to 2 GeV and at Q2$<$5GeV2 with CLAS.

Exclusive meson electroproduction off protons is a powerful tool to probe the effective degrees of freedom in excited nucleon states at the varying distance scale where the transition from the contributions of both quark core and meson-baryon cloud to the quark core dominance. During the past decade, the CLAS collaboration has executed a broad experimental program to study the excited states of the proton using polarized electron beam and (un)polarized proton targets. The measurements covered a broad kinematic range in the invariant mass W and photon virtuality Q2 with nearly full coverage in solid angles in the hadronic CMSystem. As results, several low-lying nucleon resonance states have been explored, such as ?(1230)3/2+, N(1440)1/2+, N(1520)3/2-, and N(1535)1/2- in particular for W<1.6 GeV. In this talk, we present preliminary cross-sections and helicity amplitudes of the reaction g*p?npi+ at higher W (1.6 to 2.0 GeV). Some of the excited states with isospin 1/2 and with masses near 1.7 GeV can be accessed in single npi+ production as there are no isospin 3/2 states present in this mass range with the same spin-parity assignments. These are the N(1675)5/2-, N(1680)5/2+, and N(1710)1/2+ states. We will briefly discuss preliminary results for these states.

Burkert, Volker↗
DOE OSTI2022

Search for the NΔ resonance in the 𝛾𝑑 → 𝑑𝜋 +𝜋 − reaction

A dibaryon which is an object with baryon number B = 2 has been studied for a long time. Dyson and Xuong classified non-strangeness dibaryon states based on SU(6) symmetries in 1960?s. In the framework, the deuteron is classified as one of the sextet states of dibaryons. Although dibaryon have been an interesting subject of research for a long time, most of the experimental studies up to the early 2000?s were unsuccessful. The CELCIUS/WASA collaboration reported this state via the double-pionic fusion reaction (?= ! 3c0c0) in 2009. Thereafter, the WASA-at-COSY collaboration revealed properties of the isoscaler resonance state via the ?= ! 3c0c0 reaction in 2011. The dibaryon resonance state with isospin ? = 0 and spin ( = 3 thought to be a ?03 which was predicted by Dyson and Xuong at 2.35 GeV?22 with a configuration of ??. The reported mass and width of that state were 2?37 GeV?22 and 0?07 GeV?22, espectively. The mass was ?0?08 GeV?22 smaller than that of 2?, the width was narrower than that of single ?. This surprising result made dibaryon study come back into the limelight. ?12 is one of the dibaryon states classified by Dyson and Xuong with isospin ? = 1, spin ( = 2. This state can be regarded as an s-wave #? resonance. ?12 is an interesting state from the point of view of the possibilities of existence as an internal structure of ?03 and contribution to many-body effects in nuclei. Though there were some experimental clues and theoretical studies of this state, it was unclear whether the obtained experimental results represented a real resonance or not due to the difficulty of separation from kinematical effects. Very recently, the FOREST group at Tohoku University reported a photoproduced isovector dibaryon state at mass of 2.14 GeV?22 in the 3c0 invariant mass spectra of the W3 ! 3c0c0 reaction. The most probable ?% configuration was 2¸ although they didn?t exclude the possibility of ?% = 1¸ or 3?. They separated the dibaryon production process from conventional pion production process for the first time using angular distribution of deuteron. We investigated the W3 ! 3c¸c? reaction for study of a possible #? dibaryon state using a deuterium target at the Research Center for Electron Photon Science, Tohoku University, Japan. In the experiment, ?3 ? 1012 tagged photon beam at energies ranging from 0.8 to 1.1 GeV was impinged to the liquid deuterium target (?520 mg?cm2) and the charged particles in the final state: deuteron, c¸, and c?, were detected by a magnetic spectrometer with a large solid angle named NKS2. NKS2 had capabilities of reconstructing momentum of charged particles, multi-track analysis, and ??c separation. We performed two different analyses named 2-track analysis and 3-track analysis. The 2-track (3-track) analysis was for events in which two (three) particles of 3c¸c? in the final state, including deuteron, were detected by NKS2. In the 3-track and 2-track analysis, ?2000? ?15000 events were identified as the W3 ! 3c¸c? reaction events, respectively. The 2-track analysis with higher statistics was mainly used to derive the cross sections, and the 3-track analysis was used to check the consistency of the 2-track analysis. In this thesis, we have shown the total cross section, the differential cross sections of the W3 ! 3c¸c? reaction in the region of jC j ¡ 0?15 GeV2. This is the world?s first measurement of this reaction in this energy region. Dibaryon resonance structures were observed below the #? threshold in the differential cross section of the invariant mass of 3c?. The mass and width of the structure were consistent with these of ?12 measured by the W3 ! 3c0c0 reaction. The mechanism of the production process was discussed based on the angular distribution of emitted deuteron.

Toyama, Yuichi↗
DOE OSTI2010

The effective chiral Lagrangian from the theta term

We construct the effective chiral Lagrangian involving hadronic and electromagnetic interactions originating from the QCD {theta}-bar term. We impose vacuum alignment at both quark and hadronic levels, including field redefinitions to eliminate pion tadpoles. We show that leading time-reversal-violating (TV) hadronic interactions are related to isospin-violating interactions that can in principle be determined from charge-symmetry-breaking experiments. We discuss the complications that arise from TV electromagnetic interactions. Some implications of the expected sizes of various pion-nucleon TV interactions are presented, and the pion-nucleon form factor is used as an example.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Tensor optimized Fermi sphere method for nuclear matter—Power series correlated wave function and a cluster expansion

A new formalism, called “tensor optimized Fermi sphere (TOFS) method”, is developed to treat the nuclear matter using a bare interaction among nucleons. In this method, the correlated nuclear matter wave function is taken to be a power series type, Ψ{sub N}=[∑{sub n=0}{sup N}(1∕n!)F{sup n}]Φ{sub 0} and an exponential type, Ψ{sub ex}=exp(F)Φ{sub 0}, with the uncorrelated Fermi-gas wave function Φ{sub 0}, where the correlation operator F can induce central, spin–isospin, tensor, etc. correlations, and Ψ{sub ex} corresponds to a limiting case of Ψ{sub N} (N→∞). In the TOFS formalism based on Hermitian form, it is shown that the energy per particle in nuclear matter with Ψ{sub ex} can be expressed in terms of a linked-cluster expansion. On the basis of these results, we present the formula of the energy per particle in nuclear matter with Ψ{sub N}. We call the Nth-order TOFS calculation for evaluating the energy with Ψ{sub N}, where the correlation functions are optimally determined in the variation of the energy. The TOFS theory is applied for the study of symmetric nuclear matter using a central NN potential with short-range repulsion. The calculated results are fairly consistent to those of other theories such as the Brueckner–Hartree–Fock approach etc.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2012

Solution of the Skyrme-Hartree-Fock-Bogolyubov equations in the Cartesian deformed harmonic-oscillator basis. (VII) HFODD (v2.49t): A new version of the program

We describe the new version (v2.49t) of the code HFODD which solves the nuclear Skyrme Hartree-Fock (HF) or Skyrme Hartree-Fock-Bogolyubov (HFB) problem by using the Cartesian deformed harmonic-oscillator basis. In the new version, we have implemented the following physics features: (i) the isospin mixing and projection, (ii) the finite temperature formalism for the HFB and HF+BCS methods, (iii) the Lipkin translational energy correction method, (iv) the calculation of the shell correction. A number of specific numerical methods have also been implemented in order to deal with large-scale multi-constraint calculations and hardware limitations: (i) the two-basis method for the HFB method, (ii) the Augmented Lagrangian Method (ALM) for multi-constraint calculations, (iii) the linear constraint method based on the approximation of the RPA matrix for multi-constraint calculations, (iv) an interface with the axial and parity-conserving Skyrme-HFB code HFBTHO, (v) the mixing of the HF or HFB matrix elements instead of the HF fields. Special care has been paid to using the code on massively parallel leadership class computers. For this purpose, the following features are now available with this version: (i) the Message Passing Interface (MPI) framework, (ii) scalable input data routines, (iii) multi-threading via OpenMP pragmas, (iv) parallel diagonalization of the HFB matrix in the simplex breaking case using the ScaLAPACK library. Finally, several little significant errors of the previous published version were corrected.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Survey of Evaluated Isobaric Analog States

Isobaric analog states (IAS) can be used to estimate the masses of members belonging to the same isospin multiplet. Experimental and estimated IAS have been used frequently within the Atomic Mass Evaluation (AME) in the past, but the associated set of evaluated masses have been published for the first time in AME2012 and NUBASE2012. In this paper the current trends of the isobaric multiplet mass equation (IMME) coefficients are shown. The T = 2 multiplet is used as a detailed illustration.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2014

β Decay in the Region of Neutron-deficient {sup 69,70,71}Kr

Decay spectroscopy was performed for neutron-deficient nuclei ranging from zinc to krypton with isospin −3/2 ≤T{sub z}≤0. Measurements of correlated β-delayed protons allowed us to determine the isobaric analog states fed from the decay of {sup 65}Se and {sup 69}Kr, constraining the spin of the {sup 69}Kr ground state. Preliminary results regarding the half lives for the T{sub z}=−1 systems, relevant to the rapid proton capture (rp) process, are discussed.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

Hyperon Resonance Photoproduction at CLAS

The study of hyperon resonances has entered a new era of precision with advent of high-statistics photoproduction data from the CLAS detector at Jeffersonnext term Lab. These data have multi-particle final states, allowing clean identification of exclusive reactions associated with strange mesons and baryons. Examples of physics results are: evidence for isospin interference in the decay of the Λ(1405) resonance; a strong suggestion of meson cloud effects in the structure of the Sigma (1385) resonance; data from Klow asterisk photoproduction that will test the existence of the purported K0(800) meson. Properties of other hyperon resonances will also be studied in the near future.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

The NJL-jet model for quark fragmentation functions

A description of fragmentation functions which satisfy the momentum and isospin sum rules is presented. We concentrate on the pion fragmentation function, taking into account cascade-like processes in a generalized jet-model approach. Numerical results obtained in this NJL-jet model are presented.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Kaon fragmentation function from NJL-jet model

The NJL-jet model provides a sound framework for calculating the fragmentation functions in an effective chiral quark theory, where the momentum and isospin sum rules are satisfied without the introduction of ad hoc parameters [1]. Earlier studies of the pion fragmentation functions using the Nambu-Jona-Lasinio (NJL) model within this framework showed good qualitative agreement with the empirical parameterizations. Here we extend the NJL-jet model by including the strange quark. The corrections to the pion fragmentation function and corresponding kaon fragmentation functions are calculated using the elementary quark to quark-meson fragmentation functions from NJL. The results for the kaon fragmentation function exhibit a qualitative agreement with the empirical parameterizations, while the unfavored strange quark fragmentation to pions is shown to be of the same order of magnitude as the unfavored light quark's. The results of these studies are expected to provide important guidance for the analysis of a large variety of semi-inclusive data.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

A high-accuracy extraction of the isoscalar {pi}N scattering length from pionic deuterium data

We present a high-accuracy calculation of the {pi}(bar sign)d scattering length using chiral perturbation theory up to order (M{sub {pi}/}m{sub p}){sup 7/2}. For the first time isospin-violating corrections are included consistently. The resulting value of a{sub {pi}-}bar{sub d} has a theoretical uncertainty of a few percent. We use it, together with data on pionic deuterium and pionic hydrogen atoms, to extract the isoscalar and isovector pion-nucleon scattering lengths from a combined analysis, and obtain a{sup +} (7.9{+-}3.2){center_dot}10{sup -3}M{sub {pi}}{sup -1} and a-bar (86.3{+-}1.0){center_dot}10{sup -3}M{sub {pi}}{sup -1}.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Gamow-Teller Transitions Studied in ({sup 3}He, t) Reaction and Analogous {beta} decay

Due to the simplicity of the {sigma}{tau} operator that causes Gamow-Teller (GT) transitions, they are the most popular nuclear weak process in the Universe. The GT transitions in pf-shell nuclei, for example, starting from stable T{sub z} = +1 and proton-rich T{sub z} = +1 nuclei, where T{sub z} = (N-Z)/2, play important roles in the supernova-explosion or rp-process nucleosynthesis. In the {beta}-decay study of pf-shell nuclei, half-lives can be measured rather accurately. On the other hand, in a high-resolution ({sup 3}He, t) charge-exchange reaction at 0 degree sign , individual GT transitions up to high excitations can be studied. In order to derive reliable GT transition strengths B(GT), we present a unique analysis that combines the strength distribution form the ({sup 3}He, t) measurement with the information from the study of mirror {beta} decay, where good isospin symmetry of T{sub z} = {+-}1{yields}0 transitions is assumed.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2010

Comparison of T{sub z} = {+-}1{yields}0 GT Transitions

Gamow-Teller (GT) transitions can be studied in both {beta}-decay and charge exchange(CE) reactions. If isospin is a good quantum number, then the T{sub z} = -1{yields}0 and T{sub z} = +1{yields}0 GT mirror transitions, are identical. Therefore, a comparison of the results from studies of {beta} decay and CE should shed light on this assumption. Accordingly we have studied the {beta} decay of the T{sub z=-1} fp-shell nuclei, {sup 54}Ni, {sup 50}Fe, {sup 46}Cr, and {sup 42}Ti, produced in fragmentation and we have compared our results with the spectra from ({sup 3}He, t) measurements on the mirror T{sub z} = +1 target nuclei studied in high resolution at RCNP, Osaka. The {beta}-decay experiments were performed as part of the STOPPED beam RISING campaign at GSI.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2010

Study of DCX reaction on medium nuclei with Monte-Carlo Shell Model

In this work a method is introduced to calculate the DCX reaction in the framework of Monte-Carlo Shell Model (MCSM). To facilitate the use of Zero-temperature formalism of MCSM, the Double-Isobaric-Analog State (DIAS) is derived from the ground state by using isospin shifting operator. The validity of this method is tested by comparing the MCSM results to those of the SU(3) symmetry case. Application of this method to DCX on {sup 56}Fe and {sup 93}Nb is discussed.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2010

3D calculation of Tucson-Melbourne 3NF effect in triton binding energy

As an application of the new realistic three-dimensional (3D) formalism reported recently for three-nucleon (3N) bound states, an attempt is made to study the effect of three-nucleon forces (3NFs) in triton binding energy in a non partial wave (PW) approach. The spin-isospin dependent 3N Faddeev integral equations with the inclusion of 3NFs, which are formulated as function of vector Jacobi momenta, specifically the magnitudes of the momenta and the angle between them, are solved with Bonn-B and Tucson-Melbourne NN and 3N forces in operator forms which can be incorporated in our 3D formalism. The comparison with numerical results in both, novel 3D and standard PW schemes, shows that non PW calculations avoid the very involved angular momentum algebra occurring for the permutations and transformations and it is more efficient and less cumbersome for considering the 3NF.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2010

Precision spectroscopy of Kaonic helium-3 and helium-4 3d{yields}2p X-rays

Recently, the shift of the kaonic helium-4 2p state was precisely determined by the E570 and SIDDHARTA experiments. Prior to the experiment by E570, the average of three earlier experimental results showed -43{+-}8 eV,while most of the theoretical calculations give {approx}0 eV. This five-sigma discrepancy between theory and experiment was known as the 'kaonic helium puzzle'. A recent theoretical model showed a possible resonance-like shift of maximum 10 eV for a certain value of a deep antikaon-nucleon interaction potential, which is different in helium 3 and helium 4.The E570 experiment determined the shift of the kaonic helium-4 2p state as +2{+-}2 (stat){+-}2 (sys) eV in 2007. The SIDDHARTA experiment determined the shift as 0{+-}6(stat){+-}2(sys) eV in 2009. The results of these experiments resolved the long-standing puzzle. A new experiment of the kaonic helium-3 X-ray measurement is being prepared by the J-PARC E17 collaborators, and the kaonic helium-3 X-ray data taken very recently by the SIDDHARTA experiment are on the way to be analyzed. The results of the E570, E17 and SIDDHARTA experiments examine the strong interaction for light nuclei with different isospin, and test furthermore recent theoretical predictions.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2010

High-resolution study of {sup 37}Cl{yields}{sup 37}Ar Gamow-Teller transition via {sup 37}Cl({sup 3}He, t){sup 37}Ar reaction

We performed a {sup 37}Cl({sup 3}He, t){sup 37}Ar experiment at E = 140 MeV/nucleon and 0 deg. with a resolution of 30 keV. The Gamow-Teller (GT) strength distribution was obtained up to the excitation energy (E{sub x}) of 14.2 MeV in {sup 37}Ar. Under the assumption of isospin symmetry, the GT strengths in the {sup 37}Cl{yields}{sup 37}Ar and {sup 37}Ca{yields}{sup 37}K transitions are analogous. The obtained strength distribution was compared with the mirror {sup 37}Ca{beta} decay up to E{sub x} = 8.6 MeV. The overall shapes of the distributions were similar, but the details were not necessary the same. In order to understand those differences, the experimental distribution was compared with the shell model (SM) calculation using the USD interaction. The SM calculation suggests that differences at lower energies can be caused by a large tensor contribution in the charge-exchange reaction. On the other hand, the differences seen at higher energies are due to the breaking of the mirror symmetry. The neutrino cross section for the {sup 8}B solar neutrino source was calculated using the obtained data.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2010

Gamow-Teller Transitions in Proton Rich Exotic pf-shell Nuclei Deduced from Mirror Transitions

The rp-process nucleosynthesis proceeds through nuclei near the proton drip-line, in which Gamow-Teller (GT) transitions starting from unstable pf-shell nuclei play important roles. In the {beta}-decay study of these nuclei, half-lives can be measured rather accurately. On the other hand, in the high-resolution ({sup 3}He, t) charge-exchange reactions on mirror nuclei, individual GT transitions can be studied up to high excitations. For the accurate study of the GT transition strengths in the A = 52, T = 2, system, we compare and combine the {beta}-decay study of the proton-rich nucleus {sup 52}Ni and the {sup 52}Cr({sup 3}He, t) measurement assuming the isospin symmetry of the T{sub z} = {+-}2{yields}{+-}1 transitions.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗