Search results for "nucl-th"
showing 10 items of 1223 documents
Three-particle quantization condition: an update
2014
We give an update on our derivation of a quantization condition relating the finite-volume spectrum of three particles in a cubic box to infinite-volume scattering quantities. We have discovered and fixed technical problems in the derivation sketched in the proceedings of last year's lattice conference [arXiv:1311.4848], and have presented a detailed description of the corrected derivation in Ref. [arXiv:1408.5933]. Here we give an overview of the problems and their solutions, and describe open questions.
Adler function and hadronic vacuum polarization from lattice vector correlators
2013
We study a representation of the hadronic vacuum polarization based on the time-momentum representation of the vector correlator. This representation suggests a way to compute the hadronic vacuum polarization and the associated Adler function for any value of virtuality, irrespective of the flavor structure of the current. We present results on both of these phenomenologically important functions, derived from local-conserved two-point lattice vector correlation functions, computed on a subset of light two-flavor ensembles made available to us through the CLS effort.
Determination of the $\boldsymbol{��^3{\rm He}}$ threshold structure from the low energy $\boldsymbol{pd \to ��^3{\rm He}}$ reaction
2016
We analyze the data on cross sections and asymmetries for the $pd (dp) \to ��^3{\rm He}$ reaction close to threshold and look for bound states of the $��^3 {\rm He}$ system. Rather than parameterizing the scattering matrix, as is usually done, we develop a framework in which the $��^3 {\rm He}$ optical potential is the key ingredient, and its strength, together with some production parameters, are fitted to the available experimental data. The relationship of the scattering matrix to the optical potential is established using the Bethe-Salpeter equation and the $��^3 {\rm He}$ loop function incorporates the range of the interaction given by the empirical $^3 {\rm He}$ density. We find a loc…
Triangle singularity mechanism for the $pp \to ��^+ d$ fusion reaction
2021
We develop a model for the $pp \to ��^+ d$ reaction based on the $pp \to ��(1232) N$ transition followed by $��(1232) \to ��N'$ decay and posterior fusion of $N N'$ to give the deuteron. We show that the triangle diagram depicting this process develops a triangle singularity leading to a large cross section of this reaction compared to ordinary fusion reactions. The results of the calculation also show that the process is largely dominated by the $pp$ system in $L=2, S=0$, which transfers $J=2$ to the final $��^+ d$ system. This feature is shown to be well suited to provide $L=2,S=1$, $J^\mathrm{tot}=3$ for $np$ in the $np(I=0) \to ��^- pp$ followed by $pp \to ��^+ d$ reaction, which has be…
Direct X(3872) production in e+e- collisions
2014
Direct production of the charmonium-like state $X(3872)$ in $e^+e^-$ collisions is considered in the framework of the vector meson dominance model. An order-of-magnitude estimate for the width $\Gamma(X\to e^+e^-)$ is found to be $\gtrsim$0.03 eV. The same approach applied to the $\chi_{c1}$ charmonium decay predicts the corresponding width of the order 0.1 eV in agreement with earlier estimates. Experimental perspectives for the direct production of the $1^{++}$ charmonia in $e^+e^-$ collisions are briefly discussed.
Semileptonic decays of spin-1/2 doubly charmed baryons
2012
We evaluate exclusive semileptonic decays of ground-state spin-1/2 doubly heavy charmed baryons. The decays are driven by a $c\to s,d$ transition at the quark level. Our form factors are consistent with Heavy Quark Symmetry constraints. The latter are valid in the limit of infinitely heavy quark mass at zero recoil.
Antineutrino induced Lambda(1405) production off the proton
2015
We have studied the strangeness changing antineutrino induced reactions $\bar{\nu}_{l} p \rightarrow l^+ \phi B $, with $\phi B = K^-p$, $\bar{K}^0n$, $\pi^0\Lambda$, $\pi^0\Sigma^0$, $\eta\Lambda$, $\eta\Sigma^0$, $\pi^+\Sigma^-$, $\pi^-\Sigma^+$, $K^+\Xi^-$ and $K^0\Xi^0$, using a chiral unitary approach. These ten coupled channels are allowed to interact strongly, using a kernel derived from the chiral Lagrangians. This interaction generates two $\Lambda(1405)$ poles, leading to a clear single peak in the $\pi \Sigma$ invariant mass distributions. At backward scattering angles in the center of mass frame, $\bar{\nu}_{\mu} p \rightarrow \mu^+ \pi^0 \Sigma^0$ is dominated by the $\Lambda(1…
Progress and open questions in the physics of neutrino cross sections
2014
New and more precise measurements of neutrino cross sections have renewed the interest in a better understanding of electroweak interactions on nucleons and nuclei. This effort is crucial to achieve the precision goals of the neutrino oscillation program, making new discoveries, like the CP violation in the leptonic sector, possible. We review the recent progress in the physics of neutrino cross sections, putting emphasis on the open questions that arise in the comparison with new experimental data. Following an overview of recent neutrino experiments and future plans, we present some details about the theoretical development in the description of (anti)neutrino-induced quasielastic scatter…
Recent Developments in Neutrino/Antineutrino - Nucleus Interactions
2012
Recent experimental results and developments in the theoretical treatment of neutrino-nucleus interactions in the energy range of 1-10 GeV are discussed. Difficulties in extracting neutrino-nucleon cross sections from neutrino-nucleus scattering data are explained and significance of understanding nuclear effects for neutrino oscillation experiments is stressed. Detailed discussions of the status of two-body current contribution in the kinematic region dominated by quasi-elastic scattering and specific features of partonic nuclear effects in weak DIS scattering are presented.
Gold-plated moments of nucleon structure functions in baryon chiral perturbation theory
2014
We obtain leading- and next-to-leading order predictions of chiral perturbation theory for several prominent moments of nucleon structure functions. These free-parameter free results turn out to be in overall agreement with the available empirical information on nearly all of the considered moments, in the region of low-momentum transfer ($Q^2 < 0.3$ GeV$^2$). Especially surprising is the situation for the spin polarizability $\delta_{LT}$, which thus far was not reproducible in chiral perturbation theory for proton and neutron simultaneously. This problem, known as the "$\delta_{LT}$ puzzle," is not seen in the present calculation.