Proton Breakup Research Articles

Unexpected properties of interaction of high-energy protons**This review is an extended version of a talk at the Scientific Session of the Physical Sciences Division, Russian Academy of Sciences, “On the 100th anniversary of the birth of Vitaly Ginzburg,” held on October 5, 20016 [see Physics-Uspekhi 60 (4) 413 (2017)

Experimental data on proton–proton interactions in high-energy collisions show that the elastic-to-inelastic scattering ratio varies in an unexpected way with the collision energy: the decrease at comparatively low energies is followed by an increase by a factor of over 1.5 (!) in the energy range from 11–60 GeV at the Intersecting Storage Rings (ISR) to 7–13 TeV at the Large Hadron Collider (LHC). Intuitive expectations are that, classically, proton break-up processes continue increasing in number compared to proton survivals. It can be assumed that this surprising effect is due to either the asymptotic freedom property or the collision time being extremely short at such high energies. The unquestionable unitarity principle is combined with the available elastic scattering data to gain new insight into the spatial shape of the interaction region of colliding protons. We discuss how this region evolves at energies currently used and make some predictions on its behavior at still higher energies under different assumptions concerning the relative roles of elastic scattering and inelastic processes. The shape can transform rather drastically if elastic processes keep increasing in proportion. There is an unexpected corollary to this unexpected property. The possible origins of the effect and its relation to strong interaction dynamics are discussed.

Beautiful clusters – boron-9: simulations and decay

Monte-Carlo simulations for analysis of the9Be(3He, t)9B∗ reaction at 33 MeV using coincidences between the high-resolution Munich Q3D spectrograph and the large-acceptance Birmingham silicon detector array are presented. These focus on the identification of the proton break-up product and the application to evidencing the first excited1/2+ state. Identifying this state has posed a challenge for over 70 years, but would enable the mirror symmetry in this light system to be explored, giving insight into its possible clustered structure. Penetrabilities for the low excitation energy regime are calculated showing the efficacy of the proton-identification method.

Systematic Study of Three-Nucleon System Dynamics in Deuteron–Proton Breakup Reaction

We report on preliminary results of the first measurement of elastic scattering of protons from deuterons and proton induced deuteron breakup at proton beam energy of 108 MeV conducted at new Cyclotron Center Bronowice IFJ PAN in Krakow. The experiment is aimed at precise determination of the differential cross section for extensive set of kinematical configurations in a wide range of angular acceptance. In the first data taking run the average statistical per-point accuracy of about 5% has been reached.

Breakup of 8B on 58Ni at energies around the Coulomb barrier and the astrophysical S17(0) factor revisited

Calculations of breakup and direct proton transfer for the 8 B+ 58 Ni system at energies around the Coulomb barrier ( E B,lab =22.95 MeV) were performed by the continuum-discretized coupled channels (CDCC) method and the coupled-reaction-channels (CRC) method, respectively. For the 7 Be+ 58 Ni interaction, we used a semimicroscopic optical model potential (OMP) that combines microscopic calculations of the mean-field double folding potential and a phenomenological construction of the dynamical polarization potential (DPP). The 7 Be angular distribution at E lab =25.75 MeV from the 8 B breakup on 58 Ni was calculated and the spectroscopic factor for 8 B → 7 Be+ p vertex, S expt = 1.10 ± 0.05, was deduced. The astrophysical S 17 (0) factor was calculated equal to 20.7 ±1.1 eV•b, being in good agreement with the previously reported values.

Near and sub-barrier reactions of 8B

Four classes of measurements that are important for achieving a complete understanding of the reactions of exotic nuclei are identified and classified according to their degree of difficulty. Previously reported data for near- and sub-barrier fusion of 8 B+58 Ni are critically reviewed. The influence of breakup protons on the evaporation proton measurements for this system is shown to be small at all energies except for the lowest one measured, and corrections are made for this process. Model dependencies in the deduced fusion cross sections are assessed using three different evaporation codes. Data sets for targets of 58 Ni and 28 Si are shown to be consistent with each other, and with fusion enhancement up to energies that are greater than the Coulomb barrier Vb (Ec.m. ≲ Vb + 1.5×ћω ). An important difference with the behavior of neutron-halo systems is thereby confirmed. Possible fusion suppression beyond this energy is suggested by the 28 Si data. A proposal to measure the 8 B+40 Ar fusion cross section using an active-target time projection chamber is discussed.

Above-barrier fusion enhancement of proton-halo systems

Previously reported data for fusion of the $^{8}\mathrm{B}+(^{58}\mathrm{Ni},^{28}\mathrm{Si})$ systems are critically reviewed. New $\ensuremath{\alpha}\text{-particle}$ data from the fusion of $^{8}\mathrm{B}+^{58}\mathrm{Ni}$ also are reported, but the paper is mostly based on using realistic calculations of well-established codes to reanalyze the previous data. The influence of breakup protons on the evaporation proton measurements for the heavier system is found to be small at all energies except for the lowest one measured, and corrections are made for this process. Possible model dependencies in the deduced fusion cross sections are investigated using three different evaporation codes. The data sets for the $^{58}\mathrm{Ni}$ and $^{28}\mathrm{Si}$ targets are shown to be consistent with each other and with fusion enhancement up to energies that are greater than the Coulomb barrier ${V}_{b}$ $({E}_{\text{c.m.}}\ensuremath{\lesssim}\phantom{\rule{4pt}{0ex}}{\mathrm{V}}_{b}+1.5\ifmmode\times\else\texttimes\fi{}\ensuremath{\hbar}\ensuremath{\omega})$. This limit corresponds to 6.2 MeV above the barrier for the $^{58}\mathrm{Ni}$ target. An important difference with the behavior of neutron-halo systems is thus confirmed.

12C+p resonant elastic scattering in the Maya active target

In a proof-of-principle measurement, the Maya active target detector was employed for a C-12(p, p) resonant elastic scattering experiment in inverse kinematics. The excitation energy region from 0 to 3MeV above the proton breakup threshold in N-13 was investigated in a single measurement. By using the capability of the detector to localize the reaction vertex and record the tracks of the recoiling protons, data covering a large solid angle could be utilized, at the same time keeping an energy resolution comparable with that of direct-kinematics measurements. The excitation spectrum in N-13 was fitted using the R-matrix formalism. The level parameters extracted are in good agreement with previous studies. The active target proved its potential for the study of resonant elastic scattering in inverse kinematics with radioactive beams, when detection efficiency is of primary importance.

Systematic Study of Three-Nucleon Systems Dynamics in the Cross Section of the Deuteron–Proton Breakup Reaction

An experiment to investigate the 1H(d, pp)n breakup reaction using a deuteron beam of 340, 380 and 400 MeV and the WASA detector has been performed at the Cooler Synchrotron COSY–Julich. The main goal was the detailed study of various aspects of few-nucleon dynamics in the medium energy region, with particular emphasis on relativistic effects and their interplay with three nucleon forces. These effects become more important with increasing available energy in the three nucleon system. Therefore the investigations at high energies are crucial to understand their nature. The almost 4π geometry of the WASA detector gives an unique possibility to study various aspects of dynamics of processes in the three-nucleon reaction. Preliminary results obtained using the WASA detector are presented.

Investigation of the Three-Nucleon System Dynamics in the Deuteron–Proton Breakup Reaction

Precise and large sets of cross section, vector A x , A y and tensor A xx , A xy , A yy analyzing power data for the 1 H(d, pp)n breakup reactions were measured at 100 and 130 MeV deuteron beam energies with the SALAD and BINA detectors at KVI and the Germanium Wall setup at FZ-Julich. Results are compared with various theoretical approaches which model the three-nucleon system dynamics. The cross section data reveal a sizable three-nucleon force (3NF) and Coulomb force influence. In case of the analyzing powers very low sensitivity to these effects was found and the data are well describe by 2N models only. For A xy at 130 MeV, serious disagreements were observed when 3NF models are included in the calculations.

Enhanced subbarrier fusion for proton halo nuclei

In this short note we use a simple model to describe the dynamical effects of break-up processes in the subbarrier fusion involving weakly bound nuclei. We model two similar cases involving either a neutron or a proton halo nucleus, both schematically coupled to the break-up channels. We find that the decrease of the coulomb barrier in the proton break-up channel leads, ceteris paribus, to a larger enhancement of the subbarier fusion probabilities with respect to the neutron-halo case.

A study of proton breakup from exotic nuclei through various reaction mechanisms in 40A - 80AMeV energy range

We have studied the single proton breakup from weakly bound exotic nuclei due to several reaction mechanisms separately and their total and the interference effects, in order to clarify quantitatively which mechanism would dominate the measured observables. We have considered: (i) the recoil effect of the core-target Coulomb potential which we distinguish from the direct proton-target Coulomb potential, and (ii) nuclear breakup, which consists of stripping and diffraction. Thus, we have calculated the absolute values of breakup cross sections and parallel momentum distributions (LMD) for 8 B and 17 F projectiles on a light and a heavy target in a range of intermediate incident energies (40A-80A MeV) for each reaction mechanism. Furthermore the interference among the two Coulomb effects and nuclear diffraction has been studied in detail. The calculation of the direct and recoil Coulomb effects separately and of their interference is the new and most relevant aspect of this work.

Systematic Studies of the Three-nucleon System Dynamics in the Deutron–Proton Breakup Reaction

Precise and large sets of data for cross section, vector and tensor analyzing powers for the H-1((d) over right arrow ,pp)n breakup reaction were obtained in experiments carried out at KVI Groningen and FZ-Julich at deuteron beam energies of 100 MeV, 13 MeV and 160 MeV (cross sections only). These precise experimental data obtained in a wide phase-space region allowed to establish evidences for three-nucleon force contributions and to confirm predictions of sizable effect of the Coulomb force. The vector analyzing powers data are generally quite well described by theoretical predictions even with pure nucleon nucleon interactions. Tensor analyzing powers can be also very well reproduced by calculations in most of the studied region but in some regions locally discrepancies are observed at energy of 130 MeV. DOI:10.5506/APhysPolB.44.345

Interplay of nuclear and Coulomb effects in proton breakup from exotic nuclei

This paper gives new insight to the study of dynamical effects in proton breakup as compared to neutron breakup from a weakly bound state in an exotic nucleus. Following our recent work [Ravinder Kumar and Angela Bonaccorso, Phys. Rev. C84 014613 (2011)] there has been some discussion in the literature [B. Paes, J. Lubiana, P.R.S. Gomes, V. Guimar\~aes, Nucl. Phys. A890 1 (2012); Y. Kucuk and A. M. Moro, Phys. Rev. C86 034601 (2012)], thus in order to clarify and asses quantitatively which mechanism would dominate measured observables, we study here several reaction mechanisms separately but also their total including interference. These mechanisms are: the recoil effect of the core-target Coulomb potential which we distinguish from the direct proton-target Coulomb potential and nuclear breakup, which consists of stripping and diffraction. Direct Coulomb breakup typically gives cross sections about an order of magnitude larger than the recoil term and the amount of nuclear diffraction vs. Coulomb depends on the target. Thus for each mechanism the absolute values of breakup cross sections and parallel momentum distributions for 8B and 17F projectiles calculated on a light and a heavy target in a range of intermediate incident energies (40-80A.MeV) are presented. Furthermore we study in detail the interference among the two Coulomb effects and nuclear diffraction. The calculation of the direct and recoil Coulomb effects separately and of their interference is the new and most relevant aspect of this paper.

Cross section of the deuteron–proton breakup as a probe of three-nucleon system dynamics

Modern nucleon-nucleon interaction models can be probed quantitatively in the three-nucleon environment by comparing predictions based on rigorous solutions of the Faddeev equations with the measured observables. Proper description of the experimental data can be achieved only if the dynamical models include subtle effects of suppressed degrees of freedom, effectively introduced by means of genuine three-nucleon forces. A large set of high precision, exclusive cross-section data for the 1H(d,pp)n breakup reaction at 130 MeV, contributes significantly to constrain the physical assumptions underlying the theoretical interaction models. Comparison of nearly 1800 cross section data points with the predictions using nuclear interactions generated in various ways, allowed to establish for the first time a clear evidence of importance of the three-nucleon forces in the breakup process. Moreover, the results, supplemented by a set of cross sections from another dedicated experiment, confirmed predictions of sizable Coulomb force influences in this reaction.

Dynamical effects in proton breakup from exotic nuclei

We study dynamical effects in proton breakup from a weakly bound state in an exotic nucleus on a heavy target. The Coulomb interactions between the proton and the core and between the proton and the target are treated to all orders, including also the full multipole expansion of the Coulomb potential. The dynamics of proton nuclear and Coulomb breakup is compared to that of an equivalent neutron of higher binding energy in order to elucidate the differences with the well-understood neutron breakup mechanism. A number of experimentally measurable observables such as parallel momentum distributions, proton angular distributions, and total breakup cross sections are calculated. With respect to nuclear breakup it is found that a proton behaves exactly as a neutron of higher binding energy. The extra ``effective energy'' is caused by the combined core-target Coulomb barrier. In Coulomb breakup we distinguish the effect of the core-target Coulomb potential (called the recoil effect), with respect to which the proton behaves, again, as a more bound neutron, from the direct proton-target Coulomb potential. The latter gives cross sections about an order of magnitude larger than the recoil term. The two effects give rise to complicated interferences in the parallel momentum distributions. They are instead easily separable in the proton angular distributions, which are therefore suggested as a very useful observable for future experimental studies.

Cross Sections of the Deuteron–Proton Breakup at 130 MeV: A Probe of Three-Nucleon System Dynamics

The three‐nucleon system is the simplest, non‐trivial testing ground which allows one to probe quantitatively modern nucleon‐nucleon interaction models. The rigorous technique of solving the Faddeev equations for the three‐nucleon system allows one to test the influence of additional dynamical ingredients, referred to as three‐nucleon forces, as well as the Coulomb interaction and relativistic effects. A large set of high precision, exclusive cross‐section data for the 1H(d,pp)n breakup reaction at 130 MeV was obtained at KVI, Groningen. This allowed us to establish for the first time clear evidence for three‐nucleon force contributions to the cross sections of the breakup process and to confirm recent predictions of a sizable influence of the Coulomb force in this reaction.

Vector and Tensor Analyzing Powers in Deuteron–Proton Breakup

High precision data for vector and tensor analyzing powers of the \({^1{\rm {H}}(\vec{\rm{d}},\rm{{pp}})\rm{n}}\) breakup reaction at 130 and 100 MeV deuteron beam energies have been measured in a large fraction of the phase space. They are compared to the theoretical predictions based on various approaches to describe the three nucleon (3N) system dynamics. Theoretical predictions describe very well the vector analyzing power data, with no need to include any three-nucleon force effects for these observables. Tensor analyzing powers can be also very well reproduced by calculations in most of the studied region, but locally certain discrepancies are observed. At 130 MeV for A xy such discrepancies usually appear, or are enhanced, when model 3N forces are included. Predicted effects of 3NFs are much lower at 100 MeV and at this energy equally good consistency between the data and the calculations is obtained with or without 3NFs.

All orders proton breakup from exotic nuclei

We present a semiclassical method to treat the proton breakup from a weakly bound state in an exotic nucleus. The Coulomb interactions among the proton, the core, and the target are treated to all orders, including the full-multipole expansion of the Coulomb potential. The nuclear proton-target interaction is also treated to all orders. The core-target interaction is included as an absorption. The method is semianalytical, thus allowing for a detailed understanding of the short-range and long-range effects of the interactions in the reaction dynamics. It explains also the origin of possible asymmetries in the core parallel momentum distributions when the full-multipole expansion of the Coulomb potential is used. Calculations are compared to results of other, fully numerical, methods and to experimental data to establish the accuracy and reliability of the method.

Study of spin parts of three nucleon forces via [formula omitted] breakup reactions at intermediate energies

Measurements of deuteron–proton breakup reactions at 135 MeV/A have been made at RIKEN Accelerator Research Facility, focusing on the specific coplanar configurations. The obtained results are compared with the Faddeev calculations based on the modern nucleon–nucleon forces together with the Tucson-Melbourne99, and UrbanaIX three nucleon forces.

Evidence of the Coulomb-force effects in the cross-sections of the deuteron–proton breakup at 130 MeV

High precision cross-section data of the deuteron-proton breakup reaction at 130 MeV deuteron energy are compared with the theoretical predictions obtained with a coupled-channel extension of the CD Bonn potential with virtual Delta-isobar excitation, without and with inclusion of the long-range Coulomb force. The Coulomb effect is studied on the basis of the cross-section data set, extended in this work to about 1500 data points by including breakup geometries characterized by small polar angles of the two protons. The experimental data clearly prefer predictions obtained with the Coulomb interaction included. The strongest effects are observed in regions in which the relative energy of the two protons is the smallest.