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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 595 records · Page 33
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DOE OSTI2011

Tensor meson contribution to {gamma}p {yields} K{sup +}{Lambda}({Sigma};{sup 0}) at high energies

The role of the tensor meson K{sub 2}*(1430) exchange is investigated in the kaon photoproduction within the Regge framework. Inclusion of the K{sub 2}* exchange with the meson-baryon coupling constants chosen from the SU(3) symmetry reproduces the cross sections in good agreement with the experimental data. This shows the importance of the tensor meson exchange in the present process.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

{Lambda}(1520) photoproduction with Regge contribution

In this talk, we report our recent progresses on the {Lambda}(1520) photoproduction using the effective Lagrangian approach. In addition to the tree-level Born diagrams, we take into account the Regge-trajectories for the possible strange-meson exchanges in the t channel. We compute the angular and energy dependences of the production process, including polarization observables, such as the photon-beam asymmetry and the polarization-transfer coefficients, resulting in good qualitative agreement with current experimental data. We also compute the K{sup -} angle distribution function in the Gottfried-Jackson frame, using the polarization-transfer coefficients in the z direction.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Photoproduction of Mesons off Light Nuclei

During the last few years, a series of experiments has been done at the ELSA accelerator in Bonn with the Crystal Barrel/TAPS setup and at the MAMI accelerator in Mainz with the Crystal Ball/TAPS setup. Photoproduction of light mesons off the deuteron and {sup 3}He-nuclei has been studied in detail. We will report some of the most interesting results.A completely unexpected finding, is the pronounced structure in the excitation function of the {gamma}n {yields} n{eta} reaction around 1 GeV, which has no counterpart for the proton. Recent measurements at GRAAL, Sendai, ELSA [1] and MAMI estimate it's width below 50 MeV, which would be extremely narrow for a nucleon resonance at this excitation energy. In the experiment with the {sup 3}He target, special attention was given to the threshold behavior of the {gamma}He{sup 3} reactions in view of possible indications for the formation of (quasi-)bound {eta}-nucleus states, so-called {eta}-mesic nuclei. A very strong threshold enhancement of coherent {eta}-photoproduction off {sup 3}He was found. In a new experiment, this reaction was measured with much better statistical accuracy compared to an earlier experiment at MAMI-B using the TAPS detector [2].

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

{Lambda}K*{Lambda}(1116) photoproduction and nucleon resonances

In this presentation, we report our recent studies on the {Lambda}K*{Lambda}(1116) photoproduction off the proton target, using the tree-level Born approximation, via the effective Lagrangian approach. In addition, we include the nine (three- or four-star confirmed) nucleon resonances below the threshold {radical}(s{sub th}){approx_equal}2008 MeV, to interpret the discrepancy between the experiment and previous theoretical studies, in the vicinity of the threshold region. From the numerical studies, we observe that the S{sub 11}(1535) and S11(1650) play an important role for the cross-section enhancement near the {radical}(s{sub th}). It also turns out that, in order to reproduce the data, we have the vector coupling constants gK*S{sub 11}(1535){Lambda} = (7.0{approx}9.0) and gK*S{sub 11}(1650){Lambda} (5.0{approx}6.0).

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Kaon photoproduction and electroproduction near threshold

We analyze the electromagnetic production of K{sup +}{Lambda} and K{sup 0}{Lambda} near their production thresholds by using isobar models. In the K{sup +}{Lambda} channel we show that the model can nicely describe the available experimental data. In the K{sup 0}{Lambda} channel we demonstrate that the K{sup 0} charge form factor has sizable effects on the longitudinal cross section. By extending the model up to W = 1730 MeV, we are able to observe the existence of the narrow P{sub 11}(J{sup p} = 1/2{sup +}) resonance in the kaon photoproduction process. It is found that the most convincing mass (width) of this resonance is 1650 MeV(5 MeV).

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Hadronic particles made of multi-{rho}(770) mesons

We summarize the work [1] where we studied the few body system made of several {rho}(770) mesons. Based on the very strong interaction of two {rho}(770) vector mesons in spin 2 and isospin 0, we show that the resonances {rho}3(1690)(3{sup --}), f4(2050)(4{sup ++}), {rho}5(2350)(5{sup --}) and f6(2510)(6{sup ++}) can be interpreted as few body systems made of an increasing number of {rho}(770) particles. The fixed center approximation of the Faddeev equations is used in order to write the multi-body interaction in terms of the elementary two-body scattering amplitudes. Very good agreement with the experimental masses is found. An extension of the model to include also the interaction with K*(895) is discussed.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

NN*(1440) quasi-bound states

Inspired by a recent observation of a narrow resonance-like structure around 2360 MeV in the pn {yields} d{pi}{sup 0}{pi}{sup 0} cross section, we investigate the possibility of forming NN*(1440) quasi-bound state by meson exchange potential. With parameters of the t-channel {pi}, {sigma}, {rho} and {omega} exchanges determined by relevant NN scattering and N*(1440) decay processes, it is found that a NN*(1440) quasi-bound state with the same quantum numbers as the deuteron can be formed with binding energy about 20 MeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Effect of three-pion unitarity on resonance poles from heavy meson decays

We study the final state interaction in 3{pi} decay of meson resonances at the Excited Baryon Analysis Center (EBAC) of JLab. We apply the dynamical coupled-channels formulation which has been extensively used by EBAC to extract N{sup *} information. The formulation satisfies the 3{pi} unitarity condition which has been missed in the existing works with the isobar models. We report the effect of the 3{pi} unitarity on the meson resonance pole positions and Dalitz plot.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

The Charmonium-molecule hybrid structure of the X(3872)

We propose that the X(3872) has the charmonium and the DD*-bar hadronic molecule hybrid structure. We study the structure of the X(3872) using the schematic model with the separable interaction. The strengths of the couplings between the charmonium state and the hadronic molecule states are determined so as to reproduce the observed mass of the the X(3872). The isospin symmetry breaking is introduced by the mass differences of the neutral and charged D mesons. The obtained structure of the X(3872) is about 9% of cc-bar charmonium, 75% of the isoscalar DD*-bar molecule and 16percent; of the isovector DD*-bar molecule which explains observed properties of the X(3872) well.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

From hadrons to nuclei with charm and bottom flavors

We discuss new exotic nuclei which contain D-bar and B mesons. As simplest systems, we consider D-bar(B) bound systems with one nucleon and two nucleons. With respecting to the heavy quark symmetry, we derive the one pion exchange potential as a long range force as an interaction between D-bar(B) meson and nucleon. We solve the Schroedinger equation with coupled channels, and investigate the D-barN (BN) bound states. We further discuss the possibility of existence of D-barNN (BNN). We discuss the possible observations of these exotic states in experiments in accelerator facilities.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Possible molecular bound state of two charmed baryons

One-boson-exchange approach is widely used in the study of baryon-baryon interactions. Because of the higher masses, charmed baryons are likely to form molecular bound states. We here investigate this possibility in the {Lambda}{sub c{Lambda}c}(J{sup P} = 0{sup +}, I = 0) system, which may be the lowest mass state composed of two charmed baryons. Since the long-range interactions must play an important role for the formation of possible molecular bound states, we consider the one-pion-exchange potential explicitly and embed the short-range effects into a phenomenological cutoff parameter. As single pion exchange does not occur between two {Lambda}{sub c}'s, couplings to the nearby {Sigma}{sub c{Sigma}c}, {Sigma}{sub c{Sigma}c}* and {Sigma}{sub c}*{Sigma}{sub c}{sup *} channels may be crucial in binding two {Lambda}{sub c}'s. We find that it is possible to have a molecular bound state of two {Lambda}{sub c}'s, where the tensor force plays a crucial role, although the predicted binding energies are sensitive to the cutoff parameter.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

QCD sum rule calculation of quark-gluon three-body components in the B-meson wave function

We discuss the QCD sum rule calculation of the heavy-quark effective theory parameters {lambda}{sub E} and {lambda}{sub H}, which represent quark-gluon three-body components in the B-meson wave function. We update the sum rules for {lambda}{sub E,H} calculating the new higher-order contributions to the operator product expansion for the corresponding correlator, i.e., the order {alpha}{sub s} radiative corrections to the Wilson coefficients associated with the dimension-5 quark-gluon mixed condensate, and the power corrections due to the dimension-6 vacuum condensates. We find that the new radiative corrections significantly improve stability of the corresponding Borel sum rules, modifying the values of {lambda}{sub E,H}.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Backward-meson photoproduction at SPring-8/LEPS

Photoproductions of {pi}{sup 0} and {eta} mesons from protons were measured at backward angles. Bump structures were observed in both reaction, and a strong angular distribution of photon asymmetries was found in {pi}{sup 0} production. These structures are discussed connecting with baryon resonances.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

N* production from pp and p-barp collisions

With an effective Lagrangian approach, we give a full analysis on the NN{yields}NN{pi}{pi} and pp{yields}pn{pi}{sup +} reactions for proton beam energy from 1 to 1.5 GeV. The results are very consistent with the experiment data from CELSIUS, KEK, COSY, and so on. Based on these results, we consider the N-barN{yields}N-barN{pi}{pi} and p-barp{yields}p-barn{pi}{sup +} for proton beam energy up to 4 GeV. Compare to the pp collisions, there are many benefits to study N* resonances in these two reactions. And for the high proton beam energy up to 15 GeV, we consider some new resonances with hidden charm which are definitely beyond three constituent quarks model in the p-barp{yields}p-barpJ/{psi} and p-barp{yields}p-barp{eta}{sub c}, where there are very nice places to find these new N{sub cc}-bar*. The predicted results about p-barp collisions can be looked for at the forthcoming PANDA/FAIR experiments.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Status Report of J-PARC E19

The aim of the J-PARC E19 experiment is to search for the pentaquark {Theta}{sup +} in the {pi}{sup -}+p{yields}K{sup -}+X reaction. The expected sensitivity reaches 75 {mu}b/sr in the laboratory frame. This is the first experimental program to be performed at the J-PARC Hadron Facility. The spectrometer has been completed and successfully operated. The physics run has started on October 2010. As a first step, we accumulated the statistics which is enough to confirm the existence of the {Theta}{sup +} assuming the cross section of 1.9 {mu}b/sr reported in the past KEK experiment. We plan to study the energy dependence of the cross section for beamtime from Spring 2011.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Quark-hadron duality in nucleon structure functions

We review progress in the study of quark-hadron duality in nucleon structure functions. New developments include insights into local duality obtained using truncated moments of structure functions, which allow duality-violating higher-twist contributions to be identified in individual resonance regions. Studies of pion electroproduction have also showed the first glimpses of duality in semi-inclusive cross sections, which if confirmed would greatly expand the scope of constraining the flavor and spin dependence of parton distributions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Electromagnetic properties of baryons

We discuss the chiral behavior of the nucleon and {Delta}(1232) electromagnetic properties within the framework of a SU(2) covariant baryon chiral perturbation theory. Our one-loop calculation is complete to the order p{sup 3} and p{sup 4}/{Delta} with {Delta} as the {Delta}(1232)-nucleon energy gap. We show that the magnetic moment of a resonance can be defined by the linear energy shift only when an additional relation between the involved masses and the applied magnetic field strength is fulfilled. Singularities and cusps in the pion mass dependence of the {Delta}(1232) electromagnetic moments reflect a non-fulfillment. We show results for the pion mass dependence of the nucleon iso-vector electromagnetic quantities and present preliminary results for finite volume effects on the iso-vector anomalous magnetic moment.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Hyperon vector coupling f{sub 1}(0) from 2+1 flavor lattice QCD

We present results for the hyperon vector form factor f{sub 1} for {Xi}{sup 0}{yields}{Sigma}{sup +}l{nu}-bar and {Sigma}{sup -}{yields}nl{nu}-bar semileptonic decays from dynamical lattice QCD with domain-wall quarks. Simulations are performed on the 2+1 flavor gauge configurations generated by the RBC and UKQCD Collaborations with a lattice cutoff of a{sup -1} = 1.7 GeV. Our preliminary results, which are calculated at the lightest sea quark mass (pion mass down to approximately 330 MeV), show that a sign of the second-order correction of SU(3) breaking on hyperon vector coupling f{sub 1}(0) is likely negative.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗