Delta Delta Excitation in Proton-Proton Induced pi0pi0 Production
T. Skorodko, M. Bashkanov, D. Bogoslawsky, H. Calen, H. Clement, E. Doroshkevich, L. Demiroers, C. Ekstroem, K. Fransson, L. Gustafsson, B. Hoistad, G. Ivanov, … 展开作者
T. Skorodko, M. Bashkanov, D. Bogoslawsky, H. Calen, H. Clement, E. Doroshkevich, L. Demiroers, C. Ekstroem, K. Fransson, L. Gustafsson, B. Hoistad, G. Ivanov, M. Jacewicz, E. Jiganov, T. Johansson, O. Khakimova, S. Keleta, I. Koch, F. Kren, S. Kullander, A. Kupsc, P. Marciniewski, R. Meier, B. Morosov, C. Pauly, H. Petren, Y. Petukhov, A. Povtorejko, R. J. M. Y. Ruber, K. Schoenning, W. Scobel, B. Shwartz, J. Stepaniak, P. Thoerngren-Engblom, V. Tikhomirov, G. J. Wagner, M. Wolke, A. Yamamoto, J. Zabierowski, J. Zlomanczuk
Exclusive measurements of the $pp \to ppπ^0π^0$ reaction have been performed at CELSIUS/WASA at energies from threshold up to $T_p$ = 1.3 GeV. Total and differential cross sections have been obtained. Here we concentrate on energies $T_p \ge$ 1 GeV, where the $ΔΔ$ excitation becomes the leading process. No evidence is found for a significant ABC effect beyond that given by the conventional $t$-channel $ΔΔ$ excitation. This holds also for the double-pionic fusion to the quasibound $^2$He. The data are compared to model predictions, which are based on both pion and $ρ$ exchange. Total and differential cross sections are at variance with these predictions and call for a profound modification of the $ρ$-exchange. A phenomenological modification allowing only a small $ρ$ exchange contribution leads to a quantitative description of the data.
Hard bremsstrahlung production in proton-proton collisions has been studied with the ANKE spectrometer at COSY-Juelich in the energy range of 353-800 MeV by detecting the final proton pair {pp}_s from the pp -> {pp}_s reaction with very low excitation energy. Differential cross sections were measured at small diproton c.m. angles from 0 to 20 degrees and the average over this angular interval reveals a broad peak at a beam energy around 650 MeV with a FWHM of about 220 MeV, suggesting the influence of Delta(1232)N intermediate states. Comparison with deuteron photodisintegration shows that the…
For the first time, the total yield and inclusive spectra of the $Δ^{++}(1232)$isobar are measured in $νp$ and $νn$ charged-current interactions. An indication is obtained that the $Δ^{++}(1232)$ production mainly results from the neutrino scattering on the valence d- quark of the target nucleon. The total yield of $Δ^{++}(1232)$ in $νp$ interactions is compatible with that measured in hadronic interactions of the same net charge and net baryonic number. The yield of $Δ^{++}(1232)$ in $νn$ interactions is significantly suppressed as compared to the case of the proton target. The form of the sq…
We analyse the proton Compton-scattering differential cross section for photon energies up to 325 MeV using Chiral Effective Field Theory and extract new values for the electric and magnetic polarisabilities of the proton. Our EFT treatment builds in the key physics in two different regimes: photon energies around the pion mass ("low energy") and the higher energies where the Delta(1232) resonance plays a key role. The Compton amplitude is complete at N4L0, O(e^2 delta^4), in the low-energy region, and at NLO, O(e^2 delta^0), in the resonance region. Throughout, the Delta-pole graphs are dress…
The parity-violating asymmetry arising from inelastic electron-nucleon scattering at backward angle (~95 degrees) near the Delta(1232) resonance has been measured using a hydrogen target. From this asymmetry, we extracted the axial transition form factor G^A_{NΔ}, a function of the axial Adler form factors C^A_i. Though G^A_{NΔ} has been previously studied using charged current reactions, this is the first measurement of the weak neutral current excitation of the Delta using a proton target. For Q^2 = 0.34 (GeV/c)^2 and W = 1.18 GeV, the asymmetry was measured to be -33.4 \pm (5.3)_{stat} \pm …
Beam-helicity asymmetry measurements in the Virtual Compton Scattering reaction in the g*N-Delta transition at Q2=0.20 (GeV/c)^2
本文报道了在Delta（1232）$ resonance at Q2=0.20 (GeV/c)2. The measurements were performed at MAMI and were carried out simultaneously with the measurement of the H(\vec{e},e'p)π^0 reaction channel. It is the lowest Q2 for which the $中H（\vec{e}，e 'p）γ反应的束流螺旋度不对称性的新测量。测量的不对称性进行了比较，并已被发现是很好地描述的色散关系（DR）计算的色散。本文用DR方法研究了数据对质子的广义极化率（GPs）和核子激发到Delta（1232）的振幅的敏感性。测量的不对称性已被发现表现出更高的灵敏度的GP，而它是建议，未来的测量更高的统计精度将提供更强的约束理论计算，并将提供有价值的洞察力对更完整的理解的GP的质子和π-N振幅。
Determination of proton and neutron contributions to the $0_{g.s.}^+ \rightarrow 2_1^+$ excitations in $^{42}$Si and $^{44}$S using inelastic proton scattering in inverse kinematics and intermediate energy Coulomb excitation
Cross-sections for the proton-induced reactions on natural neodymium in energy regions 5-10 MeV and 30-35 MeV were measured using the cyclotron U-120M at the Nuclear Physics Institute at Rez near Prague. This measurement completes the investigation previously done in the 10-30 MeV energy range. Results revealed practical production thresholds and secondary maxima and minima in the excitation functions. It allowed for more appropriate calculation of thick target yields and production rates of many longer-lived radionuclides potentially disturbing the search for neutrinoless double beta decay. M…
The charge-exchange break-up of polarised deuterons pol{d}p -> {pp}n, where the final {pp} diproton system has a very low excitation energy and hence is mainly in the 1S0 state, is a powerful tool to probe the spin-flip terms in the proton-neutron charge-exchange scattering. Recent measurements with the ANKE spectrometer at the COSY storage ring at 1.6, 1.8, and 2.27 GeV have extended these studies into the pion-production regime in order to investigate the mechanism for the excitation of the Delta(1232) isobar in the pol{d}p -> {pp}X reaction. Values of the differential cross section and two …
We report on the experimental study of quadrupole collectivity in the neutron-deficient nucleus \nuc{104}{Sn} using intermediate-energy Coulomb excitation. The $B(E2; 0^+_1 \rightarrow 2^+_1)$ value for the excitation of the first $2^+$ state in \nuc{104}{Sn} has been measured to be $0.180(37)~e^2$b$^2$ relative to the well-known $B(E2)$ value of \nuc{102}{Cd}. This result disagrees by more than one sigma with a recently published measurement \cite{Gua13}. Our result indicates that the most modern many-body calculations remain unable to describe the enhanced collectivity below mid-shell in Sn …
We consider two-photon exchange (TPE) in the elastic electron-proton scattering and study the contribution arising from the production of Delta(1232) resonance in the intermediate state. We calculate all three TPE amplitudes (generalized form factors), and find that the Delta contribution mainly influences generalized electric form factor (contrary to the elastic contribution, which affects magnetic form factor), and the effect grows with Q^2. If the corresponding correction is applied to the recent polarization transfer measurements of proton form factors, their results will change markedly. …
Determination of the high density behavior of the symmetry energy through the simultaneous measurement of elliptic flow excitation functions of neutrons, protons and light clusters is proposed. The elliptic flow developed in relativistic heavy ion collisions has been proven theoretically and experimentally to have a unique sensitivity and robustness in probing the symmetry energy up to around $2 ρ_{o}$. The knowledge of the density dependence of the symmetry energy in a broad range of densities will provide a missing link for astrophysical predictions of the neutron star mass--radius relation.…
Beam asymmetries for the reactions gamma p -> p pi0 and gamma p -> n pi+ have been measured with the CEBAF Large Acceptance Spectrometer (CLAS) and a tagged, linearly polarized photon beam with energies from 1.102 to 1.862 GeV. A Fourier moment technique for extracting beam asymmetries from experimental data is described. The results reported here possess greater precision and finer energy resolution than previous measurements. Our data for both pion reactions appear to favor the SAID and Bonn-Gatchina scattering analyses over the older Mainz MAID predictions. After incorporating the present s…
Results on two-particle angular correlations for charged particles emitted in pPb collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV are presented. The analysis uses two million collisions collected with the CMS detector at the LHC. The correlations are studied over a broad range of pseudorapidity, eta, and full azimuth, phi, as a function of charged particle multiplicity and particle transverse momentum, pt. In high-multiplicity events, a long-range (2 < abs(Delta(eta)) < 4), near-side (Delta(phi) approximately 0) structure emerges in the two-particle Delta(eta)-Delta(phi) corr…
Nuclear formation cross sections are reported for 26 radionuclides, measured with 40 to 200 MeV proton irradiations of terbium foils. These data are relevant to the production of medically relevant radionuclides (e.g., 152Tb, 155Tb, 155Eu, and 156Eu) and to ongoing efforts to characterize stellar nucleosynthesis routes passing through long-lived intermediaries (e.g., 153Gd). Computational predictions from the ALICE2011, CEM03.03, Bertini, and INCL+ABLA codes are compared with newly measured data to contribute to the ongoing process of code development, and yields are calculated for selected ra…
Spin-isospin excitation of ${}^3$He nucleus by proton-induced charge-exchange reaction, ${}^3\mathrm{He}(p,n)ppp$, at forward neutron scattering angle is studied in a plane wave impulse approximation (PWIA). In PWIA, cross sections of the reaction is written in terms of proton-neutron scattering amplitudes and response functions of the transition from ${}^{3}$He to three-proton state by spin-isospin transition operators. The response functions are calculated with realistic nucleon-nucleon potential models using a Faddeev three-body method. Calculated cross sections agree with available experim…
We examine the two-photon exchange corrections to elastic electron-proton scattering within a dispersive approach, including contributions from both Nucleon and Delta intermediate states. The dispersive analysis avoids off-shell uncertainties inherent in traditional approaches based on direct evaluation of loop diagrams, and guarantees the correct unitary behavior in the high energy limit. Using empirical information on the electromagnetic nucleon elastic and N-Delta transition form factors, we compute the two-photon exchange corrections both algebraically and numerically. Results are compared…
Near-threshold $ω$-meson production in proton-proton collisions: With or without resonance excitations ?
我们目前的研究结果的$p p \to p p ω$反应考虑两种不同的情况：有和没有包括核子共振激发。最近测量的角分布的COSY-TOF合作在$Q = 173$ MeV的过剩能量和能量依赖的总截面数据$π^- p \to ωn$用于校准模型参数。核子共振的加入改善了在过剩能量$Q < 31$ MeV时$pp \to ppω$中总截面的能量依赖性的理论预测。然而，它仍然低估了数据的两倍，并且在理解反应机制方面仍然存在问题。
We investigate the pp --> pp e+e- and quasifree pn --> pn e+e- reactions within an effective Lagrangian model at the laboratory kinetic energy of 1.25 GeV for which experimental data have recently been reported by the HADES Collaboration. The model uses a meson-exchange approximation to describe the initial nucleon-nucleon (NN) scattering. Contributions to the reaction amplitudes are included from the NN bremsstrahlung as well as from the excitation, propagation and radiative decay of the Delta(1230) isobar state. It is found that the HADES data on the e+e- invariant mass distribution in the p…
We implement the de-excitation processes of residual nuclei associated with proton decays in $^{12} {\rm C}$ based on the GENIE generator and TALYS code. To derive the reasonable excitation energy spectra of residual nuclei $^{11} {\rm B}$, $^{10} {\rm B}$ and $^{10} {\rm Be}$, the default GENIE nucleon decay generator is modified in terms of the Spectral Function nuclear model. Then we use the TALYS code to estimate the de-excitation processes of residual nuclei. The TALYS calculation can partly account for the experimental data.
Using the delta-shell representation we present a successful fit to neutron-proton and proton-proton scattering data below pion production threshold. A detailed overview of the theory necessary to calculate observables with this potential is presented. A new data selection process is used to obtain the largest mutually consistent data base. The analysis includes data within the years 1950 to 2013. Using 46 parameters we obtain chi^2/Ndata = 1.04 with Ndata = 6713 including normalization data. Phase shifts with error bars are provided.
Experimental results of the rapidity spectra of protons and net-protons (protons minus antiprotons) emitted in gold-gold (Au-Au) and lead-lead (Pb-Pb) collisions, measured by a few collaborations at the alternating gradient synchrotron (AGS), super proton synchrotron (SPS), and relativistic heavy ion collider (RHIC), are described by a three-source distribution. The values of the distribution width $σ_C$ and contribution ratio (relative contribution) $k_C$ of the central rapidity region, and the distribution width $σ_F$ and rapidity shift $Δy$ of the forward/backward rapidity regions, are then…
A preferred candidate for neutrinoless double-β decay, 150Nd, is present in natural neodymium at an abundance level of 5.64%. However, neodymium could be activated by cosmic rays during the period it spends on the Earth's surface. Its activation by protons is therefore of interest when it comes to estimating the possible disturbance effects and increased background during neutrinoless double-β-decay experiments like Sudbury Neutrino Observatory plus liquid scintillator (SNO+). In most cases, we lack experimental data on proton-induced reactions on neodymium. Therefore, a measurement of cross s…
