Role of Quarks in Nuclear Structure

Thomas, A. W.

doi:10.1093/acrefore/9780190871994.013.1

Cited by 6 publications

(3 citation statements)

References 155 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The argument that the large scalar mean-field in a nuclear medium may be expected to lead to changes in the structure of a bound proton is compelling [108]. Nevertheless it is critical to test this theoretical argument against experimental evidence.…”

Section: Tests Of Changing Hadron Structurementioning

confidence: 99%

The Role of Baryon Structure in Neutron Stars

Motta,

Thomas

2022

Preprint

View full text Add to dashboard Cite

The current state of neutron star mass measurements is depicted in Fig. 1. We see that the only measurements of heavy neutron stars with reasonably small errors are those of PSR J1614-2230 [29] and PSR J0348+0432 [2], along with PSR J0740+6620 [30] which is the newest member of the heavy neutron star club. Nevertheless, the uncertainties on the aforementioned pulsars still make them all comparable with each other within two standard deviations. Therefore, a conservative lower estimate for the maximum mass of neutron stars is that of PSR J1614-2230, namely, 1.908±0.016M . RadiiOther than their masses, the radii of neutron stars are extremely sensitive to different models for the equations of state. However, the experimental constraints on radii are less numerous and until recently the systematic errors were quite large. The first new source of a constraint came on August 17th 2017, with the first gravitational wave measurement [4] of the merger of two neutron stars. This yielded the result that the radii of the neutron stars involved in the merger both lie within R = 11.9 +1.4 −1.4 , at the 90% confidence level.More recently, the NICER mission, with its X-ray telescope on the space station, obtained results [5,37] for PSR J0030+0451. The collaboration applied different analyses on the data and obtained values of (all at 68% credibility) 12.71 +1.14 −1.19 km and mass 1.34 +0.15 −0.16 M in Ref.[5] and 13.02 +1.24 −1.06 km in Ref.[37] with the mass estimated at 1.44 +0.15 −0.14 M . Another recent measurement by the NICER collaboration was that of pulsar PSR J0740+6620 which by virtue of being much heavier, is of considerable interest to nuclear physicists. They measured a radius of 12.39 +1.3 −0.98 km for a mass of 2.07 ± 0.06M [38]. Modelling Dense MatterHistorically, studies of the properties of nuclear matter were primarily aimed at understanding finite nuclei. They were based primarily on using two-body and three-body potentials with standard techniques in quantum many-body theory, such as Brueckner-Hartree-Fock (BHF) [39], Bethe-Brueckner-Goldstone (BBG) [40]. The two-body potentials were derived from phenomenological fits to nucleonnucleon scattering [41]. The quantum Monte Carlo variational approach has had considerable success with light nuclei [42], with parameters of the phenomenological three-body force tuned to nuclear data. In recent years there has been a great deal of activity using chiral effective field theory [43,44,45,46,47,48], with its systematic expansion in powers of momentum. This approach builds in the constraints of chiral symmetry within a Lagrangian theory built upon pion and nucleon degrees of freedom, plus counterterms. With a similar number of parameters to those needed for phenomenological potentials (typically 25-30), it yields a good description of nucleon-nucleon scattering data. Within the same framework, one also has a systematic expansion of a three-nucleon force, with counterterms again tuned to nuclear data. Once again one finds excellent agreement with data for light nuc...

show abstract

Section: Tests Of Changing Hadron Structurementioning

confidence: 99%

The Role of Baryon Structure in Neutron Stars

Motta,

Thomas

2022

Preprint

View full text Add to dashboard Cite

show abstract

“…The density dependent scalar couplings are calculated by solving the MIT bag model [88] equations of motion in the scalar fields and thus our calculation includes the self-consistent adjustment of the internal structure of the baryons in the medium at the corresponding local density [89][90][91]. The density dependence of these couplings is equivalent to the inclusion of repulsive three-body forces between all of the baryons, which arise naturally once allowance is made for the modification of baryon structure in the medium, without any new parameters [92,93].…”

Section: Equation Of Statementioning

confidence: 99%

Improved Treatment of Dark Matter Capture in Neutron Stars III: Nucleon and Exotic Targets

Anzuini,

Bell,

Busoni

et al. 2021

Preprint

View full text Add to dashboard Cite

We consider the capture of dark matter (DM) in neutron stars via scattering on hadronic targets, including neutrons, protons and hyperons. We extend previous analyses by including momentum dependent form factors, which account for hadronic structure, and incorporating the effect of baryon strong interactions in the dense neutron star interior, rather than modelling the baryons as a free Fermi gas. The combination of these effects suppresses the DM capture rate over a wide mass range, thus increasing the cross section for which the capture rate saturates the geometric limit. In addition, variation in the capture rate associated with the choice of neutron star equation of state is reduced. For proton targets, the use of the interacting baryon approach to obtain the correct Fermi energy is essential for an accurate evaluation of the capture rate in the Pauli-blocked regime. For heavy neutron stars, which are expected to contain exotic matter, we identify cases where DM scattering on hyperons contributes significantly to the total capture rate. Despite smaller neutron star capture rates, compared to existing analyses, we find that the projected DM-nucleon scattering sensitivity greatly exceeds that of nuclear recoil experiments for a wide DM mass range.

show abstract

“…We know that the protons and neutrons are themselves made of more fundamental particles, the quarks, and that the quark structure of the protons and neutrons may be modified inside an atomic nucleus. This is an area of research dear to my heart and it has led to a remarkably accurate description of nuclear properties (Thomas 2021).…”

mentioning

confidence: 99%