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Results for “HADRON-HADRON INTERACTIONS”

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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2010

Charmonium dissociation in matter: perspectives from CERN to JLab

The J/{Psi}-meson dissociation in nuclear matter remains one of the most surprising problems in physics. In 2000 the NA50 Collaboration at CERN reported anomalous results on J/{Psi} absorption that was considered as evidence of Quark-Gluon Plasma formation. On the other hand, there may be other mechanisms which produce an increase in J/{Psi} absorption in a hot dense medium due to the modification of the charm mesons. Our detailed calculations were one of the first indications that the CERN data can indeed be well explained by a mechanism different from QGP formation. For further clarification we proposed to study the modification of charm in nuclei through antiproton annihilation, which is now part of the PANDA project at FAIR GSI. The experiment on charmonium dissociation in nuclei is under discussion at JLab as part of its 12 GeV upgrade.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

QMC and the nature of dense matter: written in the stars?

We discuss the recent progress in calculating the properties of 'hybrid stars'(stellar objects similar to neutron stars, classified by the incorporation of non-nucleonic degrees of freedom, including but not limited to hyperons and/or a quark-matter core) using the octet-baryon Quark-Meson Coupling (QMC) model. The version of QMC used is a recent improvement which includes the in-medium modification of the quark-quark hyperfine interaction.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Nuclear Halos

We show that extreme nuclear halos are caused only by pairs of s-wave neutrons (or single s-wave neutrons) and that such states occur much more frequently in the periodic table than previously believed. Besides lingering long near zero neutron separation energy such extreme halos have very remarkable properties: they can contribute significantly to the nuclear density at more than twice the normal nuclear radius and their spreading width can be very narrow. The properties of these states are primarily determined by the ''thickness'' of the nuclear surface in the mean-free nuclear potential and thus their importance increases greatly as we approach the neutron drip line. We discuss what such extreme halos are, where they occur, what their properties are and some of their impact on nuclear observations.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Scalar response of the nucleon, chiral symmetry and nuclear matter properties

In this talk we present a description of nuclear binding in a chiral approach based on the existence of a chiral invariant scalar field associated with the generation of the masses through spontaneous chiral symmetry breaking. We discuss the emergence of such a field on the example of the NJL model. We also incorporate the effect of confinement at the level of the nucleon substructure to stabilize nuclear matter. In a particular quark-diquark model we illustrate the simutaneous influences of spontaneous chiral symmetry breaking and confinement on the nucleon mass and on the nuclear matter description.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Electric dipole moment of light nuclei

We examine the sensitivity of the deuteron Electric Dipole Moment (EDM) to variation in the nucleon-nucleon interaction. In particular, we write the EDM as a sum of two terms, one depends on the target wave function, the second on intermediate multiple scattering states in the {sup 3}P{sub 1} channel. This second contribution is sensitive to off-shell behavior of the {sup 3}P{sub 1} amplitude.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
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

Strangeness in the Meson Cloud Model

I review progress in calculating strange quark and antiquark distributions of the nucleon using the meson cloud model. This progress parallels that of the meson cloud model, which is now a useful theoretical basis for understanding symmetry breaking in nucleon parton distribution functions. I examine the breaking of symmetries involving strange quarks and antiquarks, including quark--antiquark symmetry in the sea, SU(3) flavour symmetry and SU(6) spin-flavour symmetry.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

From the nucleus to the quarks

Early work by A. W. Thomas and his colleagues inspired the first measurements of polarization in pion-deuteron elastic scattering. This line of research and technology developments enabled polarization experiments in electron-deuteron elastic scattering as well as the widespread use of polarized internal targets in storage rings. These ideas and techniques are now being used to study two-photon exchange effects and to make progress toward experiments that will allow for improved extractions the d/u ratio at high x.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

The structure of a bound nucleon

We highlight some of the progress made in understanding the EMC effect and the NuTeV anomaly using a chiral effective theory of QCD, that is, the Nambu-Jona-Lasinio model. A natural consequence of this approach is that for nuclear systems the mean scalar and vector fields couple to the quarks inside the bound nucleons and therefore nucleon properties are modified in the medium. In particular, we demonstrate that the medium modification of nucleon quark distributions provides a natural explanation of the EMC effect. We also illustrate how a proton-neutron asymmetry in nuclei leads to an isovector-vector mean-field which couples to the quarks in the bound nucleons and that this mechanism leads to an additional correction to the NuTeV measurement of sin{sup 2} {theta}{sub w}.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Meson-baryon dynamics as a tool for baryon resonance analysis

The analytical properties of the scattering amplitudes, such as the poles and zeroes on the different Riemann sheets and their residues, determine the global behavior of the amplitude on the real axis. The poles and residues provide a parameterization of the resonances which does not depend on assumptions for the background, and thus allow to relate resonance contributions in different reactions. We show the resonance parameters extracted by using the Juelich coupled reaction channel approach to meson-nucleon scattering and discuss first applications of that approach to photon-induced meson production.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

The ALICE experiment at the LHC First Physics Results

ALICE is one of the experiments at the LHC. The excellent performance of the detector has been demonstrated with the measurement and analysis of the first proton-proton collisions provided by the LHC on November 2009. We review the first physics results and the general status of the project. We also review the activities of the Mexican group participating in ALICE project.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Electroproduction of Excited Baryons with the CLAS Detector in Hall B of Jefferson Lab

Recent results from Jefferson Lab (JLab) on the extraction of single-and double-polarization observables in both the 1{pi}-and 2{pi}-channel show their high sensitivity to resonant production amplitudes and therefore their importance for the extraction of resonance parameters. The CEBAF Large Acceptance Spectrometer (CLAS) has access to the baryon resonance (N*) form factors at high Q{sup 2}, which is advantageous for the study of the dynamical properties of nucleon resonances. In anticipation of the 12 GeV energy upgrade to JLab, our group plans to extract the electromagnetic transition form factors (electrocouplings) for many well-established excited nucleon states in the unexplored domain of Q{sup 2}>5 GeV{sup 5}. The expected data on resonance electro-couplings will allow us to systematically explore how in the strong interaction regime of QCD bare quarks are dressed with gluons and how quark cores of the various N* states emerge from QCD.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Hadron loops in the quark model

We present an unquenched quark model for baryons in which the effects of quark-antiquark pair creation (uu(bar sign), dd(bar sign) and ss(bar sign)) are taken into account in an explicit form via a microscopic, QCD-inspired, quark-antiquark creation mechanism. It is shown that, while the inclusion of the qq(bar sign) pairs does not affect the baryon magnetic moments, it leads to a sizeable contribution of the orbital angular momentum to the spin of the proton.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Recent Studies of Nucleon Electromagnetic Form Factors

The electromagnetic form factors of nucleons are fundamental quantities in nucleon structure. As such, they have been studied extensively both theoretically and experimentally. Significant progress has been made with new measurements at Jlab, MAMI and MIT-Bates, with emphases on expanding the momentum-transfer range and on higher precision. In this paper, we describe the status of this field and present new results from measurements at both low and high momentum transfers. We also compare the experimental data to model predictions, and mention possible implications of the new results to other fields.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Study of the B{sub s} meson with forthcoming LHC data at CMS

A study of the properties of the B{sub s} meson decays has been done using a full Monte Carlo simulation of the CMS detector. The CMS pixel detector allows a precise measurement of the B{sub s} decay vertices which are displaced from the proton-proton interaction point. This facilitates a time dependent analysis of the angular correlations between the B{sub s} decay products. In particular, the decay B{sub s{yields}}(J/{psi}){phi}{yields}{mu}{sup +{mu}-}K{sup +}K{sup -} enables measurements of the width difference between heavy and light mass eigenstates. Furthermore, it permits a measurement of the CP violating phase {phi}{sub s} which is sensitive to physics beyond the Standard Model.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Nuclear Physics and the New Standard Model

Nuclear physics studies of fundamental symmetries and neutrino properties have played a vital role in the development and confirmation of the Standard Model of fundamental interactions. With the advent of the CERN Large Hadron Collider, experiments at the high energy frontier promise exciting discoveries about the larger framework in which the Standard Model lies. In this talk, I discuss the complementary opportunities for probing the 'new Standard Model' with nuclear physics experiments at the low-energy high precision frontier.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Masses and Structure

The use of nuclear masses to elucidate structure and its evolution with Z and N is discussed, with emphasis on two-neutron separation energies and the proton-neutron interaction as extracted from double differences of binding energies. The enhanced sensitivity of masses to structure in deformed nuclei is also discussed.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗