Deuteron Disintegration Research Articles

Deuteron disintegration by reactor antineutrinos

The existence of a new interaction involving the electron neutrino and the nucleons, which has received a convincing confirmation through a good agreement between the theoretical and experimental results concerning all observable processes with solar neutrinos, should also inevitably manifest itself in the deuteron disintegration by the neutral currents of reactor antineutrinos. The special attention is drawn to the problem of finding the neutron registration efficiency, discussed in the preparation of the experiment at the Sudbury Neutrino Observatory and in a number of special studies. Lessons are noted that can be learned from three long-standing experiments on the deuteron disintegration by reactor neutrinos.

Experimental search for the bound-state singlet deuteron in the radiative n−p capture

We performed an experimental search for the bound state singlet deuteron predicted in some microscopic calculations. The predicted energy of this metastable level is in vicinity of the deuteron disintegration threshold. This state should manifest itself in two-photon transition following thermal neutron capture by protons. The experiment consists in the search for the second gamma-ray in the cascade through a high statistics measurement of $\gamma$-ray spectra after cold neutron capture by hydrogen nuclei. The upper limit $2\mu$b (2$\sigma$ level) is obtained for the cross section of the singlet deuteron production with the bound energy in the range 10-125 keV.

Particle physics origin of the 5 MeV bump in the reactor antineutrino spectrum?

One of the most puzzling questions in neutrino physics is the origin of the excess at 5 MeV in the reactor antineutrino spectrum. In this paper, we explore the excess via the reaction $^{13}$C$(\overline{\nu}, \overline{\nu}^\prime n)^{12}$C$^*$ in organic scintillator detectors. The de-excitation of $^{12}$C$^*$ yields a prompt $4.4$ MeV photon, while the thermalization of the product neutron causes proton recoils, which in turn yield an additional prompt energy contribution with finite width. Together, these effects can mimic an inverse beta decay event with around 5 MeV energy. We consider several non-standard neutrino interactions to produce such a process and find that the parameter space preferred by Daya Bay is disfavored by measurements of neutrino-induced deuteron disintegration and coherent elastic neutrino-nucleus scattering. While non-minimal particle physics scenarios may be viable, a nuclear physics solution to this anomaly appears more appealing.

Coincidence charged-current neutrino-induced deuteron disintegration for H22O16

Semi-inclusive charge-changing neutrino reactions on targets of heavy water are investigated with the goal of determining the relative contributions to the total cross section of deuterium and oxygen in kinematics chosen to emphasize the former. The study is undertaken for conditions where the typical neutrino beam energies are in the few GeV region, and hence relativistic modeling is essential. For this, the previous relativistic approach for the deuteron is employed, together with a spectral function approach for the case of oxygen. Upon optimizing the kinematics of the final-state particles assumed to be detected (typically a muon and a proton) it is shown that the oxygen contribution to the total cross section is suppressed by roughly an order of magnitude compared with the deuterium cross section, thereby confirming that CC$\nu$ studies of heavy water can effectively yield the cross sections for deuterium, with acceptable backgrounds from oxygen. This opens the possibility of using deuterium to determine the incident neutrino flux distribution, to have it serve as a target for which the nuclear structure issues are minimal, and possibly to use deuterium to provide improved knowledge of specific aspects of hadronic structure, such as to explore the momentum transfer dependence of the isovector axial-vector form factor of the nucleon.

Coincidence charged-current neutrino-induced deuteron disintegration

Deuteron disintegration by charged-current neutrino (CC$\nu$) scattering offers the possibility to determine the energy of the incident neutrino by measuring in coincidence two of the three resulting particles: a charged lepton (usually a muon) and two protons, where we show that this channel can be isolated from all other, for instance, from those with a pion in the final state. We discuss the kinematics of the process for several detection scenarios, both in terms of kinematic variables that are natural from a theoretical point of view and others that are better matched to experimental situations. The deuteron structure is obtained from a relativistic model (involving an approximation to the Bethe-Salpeter equation) as an extension of a previous, well-tested model used in deuteron electrodisintegration. We provide inclusive and coincidence (semi-inclusive) cross sections for a variety of kinematic conditions, using the plane-wave impulse approximation, introducing final-state hadronic exchange terms (plane-wave Born approximation) and final-state hadronic interactions (distorted-wave Born approximation).

Experimental search for the singlet metastable deuteron in the radiative n-p capture

We performed an experimental search for the bound state singlet deuteron predicted in some microscopic calculations. The predicted energy of this level is in vicinity of the deuteron disintegration threshold. This state should manifest itself in two-photon $$^3 \tilde S_1 \to ^1 S_0 \to ^3 S_1$$ transition following thermal neutron capture by protons. The experiment consists in the search for the second gamma-ray in the cascade through a high statistics measurement of γ-ray spectra after thermal neutron capture by hydrogen nuclei. The upper limit 15 μb is obtained for the cross section of the singlet deuteron production with the bound energy in the range 25–125 keV.

Muon induced deuteron disintegration in three-dimensions

We present a three-dimensional (3D) description of muon induced deuteron disintegration. This reaction is treated as the decay of the muonic atom with the muon initially on the lowest K shell. Our aim is to calculate the total and differential de- cay rates. We work in momentum space and use 3D momentum eigenstates directly. This approach allowed us to calculate the appropriate nuclear matrix elements, necessary building blocks for the differential decay rate, in a single step. For contrast - in classi- cal calculations many partial-waves have to be taken into account. We achieved a very good agreement between the 3D and partial-wave methods for calculations that involve single-nucleon currents. Our result for the total decay rate is also in agreement with ex- perimental values, though these are not very precise. This success motivates us to also include two-nucleon current contributions that include the meson exchange currents. Ad- ditionally, our formalism can also be applied to other, so far poorly described, processes like: μ + 3 He → ν + n + d or μ + 3 He → ν + n + n + p.

Deuteron disintegration, thermonuclear and nuclear fission reactions induced by γ-quanta in D-saturated palladium and dense deuterium gas with synthesis of new structures

The results obtained by investigating the chemical composition and structure of Pd sample sur-faces, chamber components, and a new synthesized object (NSO) are presented. The NSO is produced in the chamber with a high-pressure (about 3 kbar) deuterium gas under irradiation by γ-quanta with an energy of 8.8 MeV. The measured concentrations of chemical elements arisen from nuclear reactions initiated by γ-quanta have made it possible to develop the phenomenological approach to describing the process whereby deuterium atoms are heated by the protons and neutrons of a deuteron photofission reaction, hot D-D fusion, Oppenheimer reactions, and palladium nuclear fission. The coefficient of the process efficiency greatly exceeds unity. A new type of reactors (deuterated nuclear fission reactor) is proposed.

Weak axial nuclear heavy meson exchange currents and interactions of solar neutrinos with deuterons

Starting from the axial heavy meson exchange currents, constructed earlier in conjunction with the Bethe–Salpeter equation, we first present the axial ρ-, ω- and a 1 -meson exchange Feynman amplitudes that satisfy the partial conservation of the axial current. Employing these amplitudes, we derive the corresponding weak axial heavy meson exchange currents in the leading order in the 1 / M expansion ( M is the nucleon mass), suitable for the nuclear physics calculations beyond the threshold energies and with wave functions obtained by solving the Schrödinger equation with one-boson exchange potentials. The constructed currents obey the nuclear form of the partial conservation of the axial current. We apply the space component of these currents in calculations of the cross sections for the disintegration of deuterons by low energy (anti)neutrinos. The deuteron and the final state nucleon–nucleon wave functions are derived (i) from a variant of the OBEPQB potential, and (ii) from the Nijmegen 93 and Nijmegen I nucleon–nucleon interaction. The extracted values of the constant L 1 , A , entering the axial exchange currents of the pionless effective field theory, are in a reasonable agreement with its value predicted by the dimensional analysis.

Parity-violating interaction effects in thenpsystem

We investigate parity-violating observables in the $np$ system, including the longitudinal asymmetry and neutron-spin rotation in $\stackrel{P\vec}{n}p$ elastic scattering, the photon asymmetry in $\stackrel{P\vec}{n}p$ radiative capture, and the asymmetries in deuteron photodisintegration $d(\stackrel{P\vec}{\ensuremath{\gamma}},n)p$ in the threshold region and electrodisintegration $d(\stackrel{P\vec}{e},{e}^{\ensuremath{'}})np$ in quasielastic kinematics. To have an estimate of the model dependence for the various predictions, a number of different, latest-generation strong-interaction potentials---Argonne ${v}_{18}$, Bonn 2000, and Nijmegen I---are used in combination with a weak-interaction potential consisting of $\ensuremath{\pi}$-, $\ensuremath{\rho}$-, and $\ensuremath{\omega}$-meson exchanges---the Desplanques-Donoghue-Holstein (DDH) model. The complete bound and scattering problems in the presence of parity-conserving, including electromagnetic, and parity-violating potentials are solved in both configuration and momentum space. The issue of electromagnetic current conservation is examined carefully. We find large cancellations between the asymmetries induced by the parity-violating interactions and those arising from the associated pion-exchange currents. In the $\stackrel{P\vec}{n}p$ capture, the model dependence is nevertheless quite small, because of constraints arising through the Siegert evaluation of the relevant ${E}_{1}$ matrix elements. In quasielastic electron scattering these processes are found to be insignificant compared to the asymmetry produced by $\ensuremath{\gamma}\text{\ensuremath{-}}Z$ interference on individual nucleons. These two experiments, then, provide clean probes of different aspects of weak-interaction physics associated with parity violation in the $np$ system. Finally, we find that the neutron-spin rotation in $\stackrel{P\vec}{n}p$ elastic scattering and asymmetry in deuteron disintegration by circularly polarized photons exhibit significant sensitivity both to the values used for the weak vector-meson couplings in the DDH model and to the input strong-interaction potential adopted in the calculation. This reinforces the conclusion that these short-ranged meson couplings are not in themselves physical observables; rather, the parity-violating mixings are the physically relevant parameters.

A radium assay technique using hydrous titanium oxide adsorbent for the Sudbury Neutrino Observatory

As photodisintegration of deuterons mimics the disintegration of deuterons by neutrinos , the accurate measurement of the radioactivity from thorium and uranium decay chains in the heavy water in the Sudbury Neutrino Observatory (SNO) is essential for the determination of the total solar neutrino flux. A radium assay technique of the required sensitivity is described that uses hydrous titanium oxide adsorbent on a filtration membrane together with a β−α delayed coincidence counting system. For a 200 tonne assay the detection limit for 232 Th is a concentration of ∼3×10 −16 g Th/g water and for 238 U of ∼3×10 −16 g U/g water. Results of assays of both the heavy and light water carried out during the first 2 years of data collection of SNO are presented.

Neutrino-induced deuteron disintegration in an experiment at the Krasnoyarsk nuclear reactor

The results of studying antineutrino interactions with deuterons (CCD and NCD reactions) and hydrogen (CCP) at the Krasnoyarsk underground reactor with the Deuteron detector are presented. The cross sections for NCD and CCD were measured with a precision of 9%. For CCP, the precision is 3%: σ expt NCD =(3.35±0.31)×10−44 cm2/fission 235U, σ expt NCD =(1.08±0.09)×10−44 cm2/fission 235U, and σ expt NCD =(6.39±0.19)×10−43 cm2/fission 235U. The precision of the experimental results is close to the theoretical one and is in good agreement with other experiments. The limit on the parameters of antineutrino oscillations into the sterile state was obtained: Δm 2≤4.7×10−2 eV2 for sin2(2ϑ)=1.0 (68% C.L.). A comparison of the measured and theoretical cross section gives us the neutron-neutron scattering length of a nn(S)=−17±6 fm in the approach of zero momentum transfers. The weak neutral current constant is in good agreement with the prediction of the Standard Model: G A NC =G A CC /0.932±0.056.

Violation of the equivalence principle in the light of the SNO and SK solar neutrino results

The SNO result on charged current deuteron disintegration, the SuperKamiokande 1258-day data on electron scattering, and other solar neutrino results are used to revisit the model of neutrino oscillations driven by a violation of the equivalence principle. We use a chisq minimization technique to examine oscillation between the nu(e) and another active neutrino, both massless, and find that within the Standard Solar Model the fit to the SNO and SuperKamiokande spectra are moderately good while a very good fit is obtained when the absolute normalizations of the 8B and hep neutrino fluxes are allowed to vary. The best fit prefers large, but not maximal, mixing, essentially no hep neutrinos, and a 40% reduction in the 8B neutrino flux. The fit to the total rates from the different experiments is not encouraging but when the rates and spectra are considerd together the situation is much improved. We remark on the expectations of the VEP model for the neutral current measurements at SNO.

Parity nonconservation in the deuteron photodisintegration

We calculate P-odd difference of the total cross sections of the deuteron disintegration by left and right polarized photons. The relative magnitude of this difference in the threshold region is about 10 −7 . Its experimental measurement would give valuable information on the weak nucleon–nucleon interaction at short distances.

The solar proton burningprocess revisited within a covariant model based on the Bethe-Salpeterformalism

A covariant model based on the Bethe-Salpeter formalism is proposedfor investigating the solar proton burning processpp→De+νe and the near-threshold deuteron disintegration viaelectromagnetic and weak interactions.Results of numerical calculations of the energy dependence of relevantcrosssections and the astrophysical low-energy cross section factorSpp of the proton burning process are presented.Our results confirm previous canonical values, and the energy dependenceofthe Spp factor is rather close to phenomenological extrapolationscommonly adopted in computations of solar nuclear reaction rates.

Low- and intermediate-energy nucleon-nucleon interactions and the analysis of deuteron photodisintegration within the dispersion relation technique

The nucleon-nucleon interaction in the region of the nucleon kinetic energy up to 1000 MeV is analysed together with the reaction $\gamma d \to pn$ in the photon energy range $E_{\gamma}=0-400$ MeV. Nine nucleon-nucleon $s$-channel partial amplitudes are reconstructed in the dispersion relation $N/D$ method: $^1S_0$, $^3S_1-^3D_1$, $^3P_0$, $^1P_1$, $^3P_1$, $^3P_2$, $^1D_2$, $^3D_2$ and $^3F_3$. Correspondingly, the dispersive representation of partial amplitudes $N\Delta \to pn$, $NN^* \to pn$ and $NN\pi \to pn$ is given. Basing on that, we have performed parameter-free calculation of the amplitude $\gamma d \to pn$, taking into account: $(i)$ pole diagram, $(ii)$ nucleon-nucleon final-state rescattering $\gamma d \to pn \to pn$, and $(iii)$ inelastic final-state rescatterings $\gamma d \to N\Delta(1232) \to pn$, $\gamma d \to NN^*(1400) \to pn$ and $\gamma d \to NN\pi \to pn$. The $\gamma d \to pn$ partial amplitudes for nine above-mentioned channels are found. It is shown that the process $\gamma d \to pn \to pn$ is significant for the waves $^1S_0$, $^3P_0$, $^3P_1$, at $E_{\gamma} =50 -100$ MeV, while $\gamma d \to N\Delta \to pn$ for the waves $^3P_2$, $^1D_2$,$^3F_3$ dominates at $E_{\gamma} > 300$ MeV. Meson exchange current contributions into the deuteron disintegration are estimated: they are significant at $E_\gamma =100-400$ MeV.

Parity violation in quasifree electron scattering off the deuteron

For deuteron electroweak disintegration, parity violating effects are investigated which arise from the interference of γ and Z exchange as well as from the hadronic sector via a small parity violating component in the deuteron. The general formalism for the differential cross section and polarization observables of electromagnetic deuteron disintegration is extended to incorporate parity violating contributions. Formal expressions for the additional structure functions and derived. Results are presented for these parity violating structure functions for quasifree kinematics neglecting final state interaction and two-body effects. Both types of parity violating contributions to the asymmetry of the inclusive reaction with respect to longitudinally polarized electrons are evaluated. The one from parity violating deuteron components is negligible over the whole range of momentum transfers considered.

Possibility to study color transparency in the large momentum transfer exclusive2H(p,2p)nreaction

The deuteron disintegration at high energies and large angles in the d(p,2p)n reaction is calculated in kinematic conditions where the dominant contributions are due to soft rescatterings of the initial and final nucleons, which accompany the hard pp reaction. The eikonal approximation, which accounts for relativistic kinematics as dictated by Feynman diagrams, reveals the important role played by the initial and final state interactions in the angular and momentum dependences of the differential cross section. Based on these results, we propose a new and effective test, at moderate energies, of the physics relevant for the color transparency phenomenon in hadron-initiated exclusive hard processes. {copyright} {ital 1997} {ital The American Physical Society}

Δ(1232)-nucleon interaction in the2H(p,n)charge-exchange reaction

The ${}^{2}\mathrm{H}(p,n)$ charge exchange reaction at ${T}_{p}=790\mathrm{MeV}$ is used to study the \ensuremath{\Delta}(1232)-nucleon $(\ensuremath{\Delta}N)$ interaction in the \ensuremath{\Delta} resonance excitation energy region. For the $\ensuremath{\Delta}N$ potential, a meson exchange model is adopted where \ensuremath{\pi}, \ensuremath{\rho}, \ensuremath{\omega}, and \ensuremath{\sigma} meson exchanges are taken into account. The deuteron disintegration below and above pion threshold is calculated using a coupled-channel approach. Various observables, such as the inclusive cross section, the quasifree \ensuremath{\Delta} decay, the coherent pion production, and the two-nucleon breakup, are considered. It is shown that these observables are influenced by the dynamical treatment of the \ensuremath{\Delta} degrees of freedom. Of special interest is the coherent pion decay of the \ensuremath{\Delta} resonance, which is studied by means of the exclusive reaction ${}^{2}\mathrm{H}(p,n{\ensuremath{\pi}}^{+}{)}^{2}\mathrm{H}.$ Both the peak energy and the magnitude of the coherent pion production cross section depend very sensitively on the strength of the $\ensuremath{\Delta}N$ potential. The coherent pions have a peak energy of $\ensuremath{\omega}=300\mathrm{MeV}$ and a strongly forward peaked angular distribution.

Gauge fields, hidden local symmetries, and meson exchange currents

The model dependence of the electromagnetic isovector meson exchange current (MEC) operator at higher momentums transfer is studied. For this purpose, the MEC operator constructed from a Lagrangian of the πϱa 1 system obtained within the framework of the hidden local symmetries (HLS) approach is compared with the analogous operator derived earlier from a minimal Yang-Mills (YM) Lagrangian. Numerical results for the deuteron disintegration near threshold show that the model dependent part of the exchange current modifies the tail of the cross section sensibly and that the presence of the a 1 meson both in the MEC and in the nuclear interaction provides a consistent description of the cross sections up to the momentums transfer t ∼ 1.5 GeV 2. It is also found that the standard π + ϱ MEC does not possess the correct chiral properties.