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Register a new userNuclear Dependence in Weak Structure Functions and the Determination of Weak Mixing Angle
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We have studied nuclear medium effects in the weak structure functions $F^A_2(x)$ and $F^A_3(x)$ and in the extraction of weak mixing angle using Paschos Wolfenstein(PW) relation. We have modified the PW relation for nonisoscalar nuclear target. We have incorporated the medium effects like Pauli blocking, Fermi motion, nuclear binding energy, nucleon correlations, pion $&$ rho cloud contributions, and shadowing and antishadowing effects.
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We obatin the ratio $F_i^A/F_i^{D}$(i=2,3, A=Be, C, Fe, Pb; D=Deuteron) in the case of weak and electromagnetic nuclear structure functions. For this, relativistic nuclear spectral function which incorporate the effects of Fermi motion, binding and nucleon correlations is used. We also consider the pion and rho meson cloud contributions and shadowing and antishadowing effects.
We have studied nuclear structure functions $F_{1A}(x,Q^2)$ and $F_{2A}(x,Q^2)$ for electromagnetic and weak processes in the region of $1 GeV^2 < Q^2 <8 GeV^2$. The nuclear medium effects arising due to Fermi motion, binding energy, nucleon correlations, mesonic contributions and shadowing effects are taken into account using a many body field theoretical approach. The calculations are performed in a local density approximation using a relativistic nucleon spectral function. The results are compared with the available experimental data. Implications of nuclear medium effects on the validity of Callan-Gross relation are also discussed.
We utilize precise weak interaction experiments on atomic muon capture and beta decay in the A = 3 nuclei, and take into account the effects of nuclear anomalous thresholds to extract the pseudoscalar pi-^3He-^3H coupling parameter, G^{eff}(m_pi^2) = 45.8+- 2.4. This is an order of magnitude improvement in precision over that from the use of pion-nuclear scattering data and dispersion relations.
Using the new results on coherent elastic neutrino-nucleus scattering data in cesium-iodide provided by the COHERENT experiment, we determine a new measurement of the average neutron rms radius of $^{133}text{Cs}$ and $^{127}text{I}$. In combination with the atomic parity violation (APV) experimental result, we derive the most precise measurement of the neutron rms radii of $^{133}text{Cs}$ and $^{127}text{I}$, disentangling for the first time the contributions of the two nuclei. By exploiting these measurements we determine the corresponding neutron skin values for $^{133}text{Cs}$ and $^{127}text{I}$. These results suggest a preference for models which predict large neutron skin values, as corroborated by the only other electroweak measurements of the neutron skin of $^{208}text{Pb}$ performed by PREX experiments. Moreover, for the first time, we obtain a data-driven APV+COHERENT measurement of the low-energy weak mixing angle with a percent uncertainty, independent of the value of the average neutron rms radius of $^{133}text{Cs}$ and $^{127}text{I}$, that is allowed to vary freely in the fit. The value of the low-energy weak mixing angle that we found is slightly larger than the standard model prediction.
Recent phenomenological analysis of experimental data on DIS processes induced by charged leptons and neutrinos/antineutrinos beams on nuclear targets by CTEQ collaboration has confirmed the observation of CCFR and NuTeV collaborations, that weak structure function $F_{2A}^{Weak} (x,Q^2)$ is different from electromagnetic structure function $F_{2A}^{EM} (x,Q^2)$ in a nucleus like iron, specially in the region of low $x$ and $Q^2$. In view of this observation we have made a study of nuclear medium effects on $F_{2A}^{Weak} (x,Q^2)$ and $F_{2A}^{EM} (x,Q^2)$ for a wide range of $x$ and $Q^2$ using a microscopic nuclear model. We have considered Fermi motion, binding energy, nucleon correlations, mesonic contributions from pion and rho mesons and shadowing effects to incorporate nuclear medium effects. The calculations are performed in a local density approximation using a relativistic nucleon spectral function which includes nucleon correlations. The numerical results in the case of iron nucleus are compared with the experimental data.
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