arXiv subjects

L. Yurev

Publications and source records attributed to L. Yurev.

5 recordsLinked to original sources

arXiv2020

Differential Cross Sections for Neutron-Proton Scattering in the Region of the $d^*(2380)$ Dibaryon Resonance

Differential cross sections have been extracted from exclusive and kinematically complete high-statistics measurements of quasifree polarized $\vec{n}p$ scattering performed in the energy region of the $d^*(2380)$ dibaryon resonance covering the the range of beam energies $T_n$ = 0.98 - 1.29 GeV ($\sqrt s$ = 2.32 - 2.44 GeV). The experiment was carried out with the WASA-at-COSY setup having a polarized deuteron beam impinged on the hydrogen pellet target and utilizing the quasifree process $dp \to np + p_{spectator}$. That way the $np$ differential cross section $σ(Θ)$ was measured over a large angular range. The obtained angular distributions complement the corresponding analyzing power $A_y(Θ)$ measurements published previously. A SAID partial-wave analysis incorporating the new data strengthens the finding of a resonance pole in the coupled $^3D_3 - ^3G_3$ waves.

hep-ex↗

arXiv2014

Charge Symmetry Breaking in dd->4Heπ0 with WASA-at-COSY

Charge symmetry breaking (CSB) observables are a suitable experimental tool to examine effects induced by quark masses on the nuclear level. Previous high precision data from TRIUMF and IUCF are currently used to develop a consistent description of CSB within the framework of chiral perturbation theory. In this work the experimental studies on the reaction dd->4Heπ0 have been extended towards higher excess energies in order to provide information on the contribution of p-waves in the final state. For this, an exclusive measurement has been carried out at a beam momentum of p=1.2 GeV/c using the WASA-at-COSY facility. The total cross section amounts to sigma(tot) = (118 +- 18(stat) +- 13(sys) +- 8(ext)) pb and first data on the differential cross section are consistent with s-wave pion production.

nucl-ex↗

arXiv2014

ABC Effect and Resonance Structure in the Double-Pionic Fusion to $^3$He

Exclusive and kinematically complete measurements of the double pionic fusion to $^3$He have been performed in the energy region of the so-called ABC effect, which denotes a pronounced low-mass enhancement in the $ππ$-invariant mass spectrum. The experiments were carried out with the WASA detector setup at COSY. Similar to the observations in the basic $pn \to d π^0π^0$ reaction and in the $dd \to ^4$He$π^0π^0$ reaction, the data reveal a correlation between the ABC effect and a resonance-like energy dependence in the total cross section. Differential cross sections are well described by the hypothesis of $d^*$ resonance formation during the reaction process in addition to the conventional $t$-channel $ΔΔ$ mechanism. The deduced $d^*$ resonance width can be understood from collision broadening due to Fermi motion of the nucleons in initial and final nuclei.

nucl-ex↗

arXiv2014

Neutron-Proton Scattering in the Context of the $d^*$(2380) Resonance

New data on quasifree polarized neutron-proton scattering, in the region of the recently observed $d^*$ resonance structure, have been obtained by exclusive and kinematically complete high-statistics measurements with WASA at COSY. This paper details the determination of the beam polarization, checks of the quasifree character of the scattering process, on all obtained $A_y$ angular distributions and on the new partial-wave analysis, which includes the new data producing a resonance pole in the $^3D_3$-$^3G_3$ coupled partial waves at ($2380\pm10 - i40\pm5$) MeV -- in accordance with the $d^*$ dibaryon resonance hypothesis. The effect of the new partial-wave solution on the description of total and differential cross section data as well as specific combinations of spin-correlation and spin-transfer observables available from COSY-ANKE measurements at $T_d$ = 2.27 GeV is discussed.

nucl-ex↗

arXiv2014

Evidence for a New Resonance from Polarized Neutron-Proton Scattering

Exclusive and kinematically complete high-statistics measurements of quasifree polarized $\vec{n}p$ scattering have been performed in the energy region of the narrow resonance structure $d^*$ with $I(J^P) = 0(3^+)$, $M \approx$ 2380 MeV/$c^2$ and $Γ\approx$ 70 MeV observed recently in the double-pionic fusion channels $pn \to dπ^0π^0$ and $pn \to dπ^+π^-$. The experiment was carried out with the WASA detector setup at COSY having a polarized deuteron beam impinged on the hydrogen pellet target and utilizing the quasifree process $\vec{d}p \to np + p_{spectator}$. That way the $np$ analyzing power $A_y$ was measured over a large angular range. The obtained $A_y$ angular distributions deviate systematically from the current SAID SP07 NN partial-wave solution. Incorporating the new $A_y$ data into the SAID analysis produces a pole in the $^3D_3 - ^3G_3$ waves as expected from the $d^*$ resonance hypothesis.

nucl-ex↗