Nuclear Theory·nucl-th

Wednesday·June 21, 2017

15 papers—10 primary·5 cross-listed

11
Scattering processes and resonances from lattice QCD
Raul A. Briceno🇺🇸 · Jozef J. Dudek🇺🇸 · Ross D. Young🇦🇺
The vast majority of hadrons observed in nature are not stable under the strong interaction, rather they are resonances whose existence is deduced from enhancements in the energy dependence of scattering amplitudes. The study of hadron resonances offers a window into the workings of quantum chromodynamics (QCD) in the low-energy non-perturbative region, and in addition, many probes of the limits of the electroweak sector of the Standard Model consider processes which feature hadron resonances. From a theoretical standpoint, this is a challenging field: the same dynamics that binds quarks and gluons into hadron resonances also controls their decay into lighter hadrons, so a complete approach to QCD is required. Presently, lattice QCD is the only available tool that provides the required non-perturbative evaluation of hadron observables. In this article, we review progress in the study of few-hadron reactions in which resonances and bound-states appear using lattice QCD techniques. We describe the leading approach which takes advantage of the periodic finite spatial volume used in lattice QCD calculations to extract scattering amplitudes from the discrete spectrum of QCD eigenstates in a box. We explain how from explicit lattice QCD calculations, one can rigorously garner information about a variety of resonance properties, including their masses, widths, decay couplings, and form factors. The challenges which currently limit the field are discussed along with the steps being taken to resolve them.
↳ hep-lathep-phnucl-thRMP(2018)·416 citations
12
Parton model description of multiparticle azimuthal correlations in $p A$ collisions
Kevin Dusling🇺🇸 · Mark Mace🇺🇸 · Raju Venugopalan🇺🇸
In arXiv:1705.00745, an initial state "parton model" of quarks scattering off a dense nuclear target was shown to qualitatively reproduce the systematics of multiparticle azimuthal anisotropy cumulants measured in proton/deuteron-nucleus ( $p A$ ) collisions at RHIC and the LHC. The systematics included i) the behavior of the four-particle cumulant $c_{2} {4}$ , which generates a real four-particle second Fourier harmonic $v_{2} {4}$ , ii) the ordering $v_{2} {2} > v_{2} {4} \approx v_{2} {6} \approx v_{2} {8}$ for two-, four-, six-, and eight-particle Fourier harmonics, iii) the behavior of so-called symmetric cumulants $SC (2, 3)$ and $SC (2, 4)$ . These features of azimuthal multiparticle cumulants were previously interpreted as a signature of hydrodynamic flow; our results challenge this interpretation. We expand here upon our previous study and present further details and novel results on the saturation scale and transverse momentum ( $p_{⊥}$ ) dependence of multiparticle azimuthal correlations. We find that the dependence of $v_{2} {2}$ and $v_{2} {4}$ on the number of color domains in the target varies with the $p_{⊥}$ window explored. We extend our prior discussion of symmetric cumulants and compute as yet unmeasured symmetric cumulants. We investigate the $N_{c}$ dependence of $v_{2} {2}$ and $v_{2} {4}$ . We contrast our results, which include multiple scatterings of each quark off the target, to the Glasma graph approximation, where each quark suffers at most two gluon exchanges with the target. We find that coherent multiple scattering is essential to obtain a positive definite $v_{2} {4}$ . We provide an algorithm to compute expectation values of arbitrary products of the "dipole" lightlike Wilson line correlators.
↳ hep-phnucl-exnucl-thPRD(2018)·79 citations
13
Beyond integrability: Baryon-baryon backward scattering in the massive Gross-Neveu model
Michael Thies🇩🇪
Due to integrability, baryon-baryon scattering in the massless Gross-Neveu model at large N features only forward elastic scattering. A bare mass term breaks integrability and is therefore expected to induce backward elastic scattering as well as inelastic reactions. We confirm these expectations by a study of baryon-baryon scattering in the massive Gross-Neveu model near the non-relativistic limit. This restriction enables us to solve the time-dependent Hartree-Fock equations with controlled approximations, using a combination of analytical methods from an effective field theory and the numerical solution of partial differential equations.
↳ hep-thhep-phnlin.SInucl-thPRD(2017)·5 citations
14
Baryon-Baryon Interactions and Spin-Flavor Symmetry from Lattice Quantum Chromodynamics
Michael L. Wagman🇺🇸 · Frank Winter🇺🇸 · Emmanuel Chang🇺🇸 · Zohreh Davoudi🇺🇸 · William Detmold🇺🇸 · Kostas Orginos🇺🇸 · Martin J. Savage🇺🇸 · Phiala E. Shanahan🇺🇸
Lattice quantum chromodynamics is used to constrain the interactions of two octet baryons at the SU(3) flavor-symmetric point, with quark masses that are heavier than those in nature (equal to that of the physical strange quark mass and corresponding to a pion mass of $\approx 806 MeV$ ). Specifically, the S-wave scattering phase shifts of two-baryon systems at low energies are obtained with the application of Lüscher's formalism, mapping the energy eigenvalues of two interacting baryons in a finite volume to the two-particle scattering amplitudes below the relevant inelastic thresholds. The values of the leading-order low-energy scattering parameters in the irreducible representations of SU(3) are consistent with an approximate SU(6) spin-flavor symmetry in the nuclear and hypernuclear forces that is predicted in the large- $N_{c}$ limit of QCD. The two distinct SU(6)-invariant interactions between two baryons are constrained at this value of the quark masses, and their values indicate an approximate accidental SU(16) symmetry. The SU(3) irreducible representations containing the $N N (^{1} S_{0})$ , $N N (^{3} S_{1})$ and $\frac{1}{2} (Ξ^{0} n + Ξ^{-} p) (^{3} S_{1})$ channels unambiguously exhibit a single bound state, while the irreducible representation containing the $Σ^{+} p (^{3} S_{1})$ channel exhibits a state that is consistent with either a bound state or a scattering state close to threshold. These results are in agreement with the previous conclusions of the NPLQCD collaboration regarding the existence of two-nucleon bound states at this value of the quark masses.
↳ hep-lathep-phnucl-thPRD(2017)·125 citations
15
Constructing probability density function of net-proton multiplicity distributions using Pearson curve method
Nirbhay Kumar Behera🇰🇷 · Min Jung Kweon🇰🇷
The probability density functions of proton, anti-proton, and net-proton multiplicity distributions are constructed from the Beam Energy Scan results of the STAR experiment using the Pearson curve method. The constructed distributions of proton and anti-proton are compared with Poisson and Binomial distributions. The net-proton probability distributions are compared with Skellam distributions to study the O(4) criticality near the chiral crossover transition. The $C_{6} / C_{2}$ results estimated from the obtained PDFs are compared with Skellam and Binomial baselines for the Beam Energy Scan data. The current study shows some signatures of O(4) criticality, which can be further investigated by precision measurements of the cumulants and understanding the contribution of non-critical fluctuations to them. This study also provides a baseline for the higher-order cumulant measurement in the upcoming RHIC BES II program and future LHC run.
↳ nucl-exhep-exhep-phnucl-thEPJA(2022)·4 citations

Affiliations

first authorsco-authorsvia INSPIRE

Scattering processes and resonances from lattice QCD

Parton model description of multiparticle azimuthal correlations in pA collisions

Beyond integrability: Baryon-baryon backward scattering in the massive Gross-Neveu model

Baryon-Baryon Interactions and Spin-Flavor Symmetry from Lattice Quantum Chromodynamics

Constructing probability density function of net-proton multiplicity distributions using Pearson curve method

Affiliations

Parton model description of multiparticle azimuthal correlations in $p A$ collisions