Search results for "nucl-th"
showing 10 items of 1223 documents
$S$-wave $KK^*$ interaction in a finite volume and the $f_1(1285)$
2015
Lattice QCD simulations provide a promising way to disentangle different interpretations of hadronic resonances, which might be of particular relevance to understand the nature of the so-called $XYZ$ particles. Recent studies have shown that in addition to the well-established naive quark model picture, the axial-vector meson $f_1(1285)$ can also be understood as a dynamically generated state built upon the $KK^*$ interaction. In this work, we calculate the energy levels of the $KK^*$ system in the $f_1(1285)$ channel in finite volume using the chiral unitary approach. We propose to calculate the loop function in the dimensional regularization scheme, which is equivalent to the hybrid appro…
The nucleon mass and pion-nucleon sigma term from a chiral analysis of lattice QCD world data
2013
The pion-mass dependence of the nucleon mass within the covariant SU(2) baryon chiral perturbation theory both without and with explicit Delta(1232) degrees of freedom up to order p^4 is investigated. By fitting to lattice QCD data in 2 and 2+1 flavors from several collaborations, for pion masses M_pi < 420 MeV, we obtain low energy constants of natural size and compatible with pion nucleon scattering data. Our results are consistent with the rather linear pion-mass dependence showed by lattice QCD. In the 2 flavor case we have also performed simultaneous fits to the nucleon mass and pion-nucleon sigma-term data. As a result of our analysis, which encompasses the study of finite volume c…
Searching for Scalar Dark Matter in Atoms and Astrophysical Phenomena: Variation of Fundamental Constants
2015
Stadnik, Yevgeny V. "Searching for Scalar Dark Matter in Atoms and Astrophysical Phenomena: Variation of Fundamental Constants" in Proceedings, 11th Patras Workshop on Axions, WIMPs and WISPs (Axion-WIMP 2015) / Irastorza, Igor G., Redondo, Javier, Carmona, José Manuel, Cebrian, Susana, Dafni, Theopisti, Iguaz, Francisco J., Luzon, Gloria (eds.), Verlag Deutsches Elektronen-Synchrotron : 2015 ; AXION-WIMP 2015 : 11th Patras Workshop on Axions, WIMPs and WISPs, 2015-06-22 - 2015-06-26, Zaragoza 11th Patras Workshop on Axions, WIMPs and WISPs, AXION-WIMP 2015, Zaragoza, Spain, 22 Jun 2015 - 26 Jun 2015 ; DESY-PROC 169-172(2015). doi:10.3204/DESY-PROC-2015-02/roberts_benjamin
The nucleon sigma terms with $N_f = 2 + 1$ O($a$)-improved Wilson fermions
2023
We present a lattice-QCD based analysis of the nucleon sigma terms using gauge ensembles with $N_f = 2 + 1$ flavors of ${\cal O}(a)$-improved Wilson fermions, with a complete error budget concerning excited-state contaminations, chiral extrapolation as well as finite-size and lattice spacing effects. We compute the sigma terms determined directly from the matrix elements of the scalar currents. For the pion nucleon sigma term, we obtain $\sigma_{\pi N} = (43.6\pm3.8)$ MeV, where the error includes all systematics. The tension with extractions based on dispersion theory persists at the 3-$\sigma$ level. For the strange sigma term, we obtain a non-zero value, $\sigma_s=(27.1\pm9.8)$ MeV.
Delta electromagnetic form factors and quark transverse charge densities from lattice QCD
2009
We discuss the techniques to extract the electromagnetic Delta form factors in Lattice QCD. We evaluate these form factors using dynamical fermions with smallest pion mass of about 350 MeV. We pay particular attention to the extraction of the electric quadrupole form factor that signals a deformation of the Delta. The magnetic moment of the $\Delta$ is extrapolated using a chiral effective field theory. Using the form factors we evaluate the transverse density distributions in the infinite momentum frame showing deformation in the Delta.
The errant life of a heavy quark in the quark-gluon plasma
2010
In the high-temperature phase of QCD, the heavy quark momentum diffusion constant determines, via a fluctuation-dissipation relation, how fast a heavy quark kinetically equilibrates. This transport coefficient can be extracted from thermal correlators via a Kubo formula. We present a lattice calculation of the relevant Euclidean correlators in the gluon plasma, based on a recent formulation of the problem in heavy-quark effective field theory (HQET). We find a $\approx20%$ enhancement of the Euclidean correlator at maximal time separation as the temperature is lowered from $6T_c$ to $2T_c$, pointing to stronger interactions at lower temperatures. At the same time, the correlator becomes fla…
Consistency between SU(3) and SU(2) chiral perturbation theory for the nucleon mass
2016
Treating the strange quark mass as a heavy scale compared to the light quark mass, we perform a matching of the nucleon mass in the SU(3) sector to the two-flavor case in covariant baryon chiral perturbation theory. The validity of the $19$ low-energy constants appearing in the octet baryon masses up to next-to-next-to-next-to-leading order~\cite{Ren:2014vea} is supported by comparing the effective parameters (the combinations of the $19$ couplings) with the corresponding low-energy constants in the SU(2) sector~\cite{Alvarez-Ruso:2013fza}. In addition, it is shown that the dependence of the effective parameters and the pion-nucleon sigma term on the strange quark mass is relatively weak ar…
Enhanced nuclear Schiff moment and time reversal violation in 229Th-containing molecules
2018
Octupole deformation results in a strongly enhanced collective Schiff moment in 229Th nucleus. An additional enhancement of time reversal (T) and parity (P) violating effects (such as T,P-violating electric dipole moments) appears in the ground 1Sigma state and in the metastable 3Delta_1 state of diatomic molecule 229ThO. Similar enhancements exist in molecular ions 229ThOH+, 229ThF+ and 225,223RaOH+. Corresponding experiments may be used to test CP-violation theories predicting T,P-violating nuclear forces and to search for axions.
Theoretical study of $^{173}$YbOH to search for the nuclear magnetic quadrupole moment
2019
CP-violating interaction of the nuclear magnetic quadrupole moment (MQM) with electrons in the ytterbium mono-hydroxide molecule, $^{173}$YbOH, is considered. Both the magnetic quadrupole moment (MQM) of the $^{173}$Yb nucleus and the molecular interaction constant WM are estimated. Electron correlation effects are taken into account within the relativistic Fock-space coupled cluster method. Results are interpreted in terms of the strength constants of CP-violating nuclear forces, neutron EDM, QCD vacuum angle $\theta$, quark EDM and chromo-EDM.
Deep learning for flow observables in ultrarelativistic heavy-ion collisions
2023
We train a deep convolutional neural network to predict hydrodynamic results for flow coefficients, average transverse momenta and charged particle multiplicities in ultrarelativistic heavy-ion collisions from the initial energy density profiles. We show that the neural network can be trained accurately enough so that it can reliably predict the hydrodynamic results for the flow coefficients and, remarkably, also their correlations like normalized symmetric cumulants, mixed harmonic cumulants and flow-transverse-momentum correlations. At the same time the required computational time decreases by several orders of magnitude. To demonstrate the advantage of the significantly reduced computati…