Nucleon Recoil Research Articles

A minimal dark matter interpretation for the CRESST-II signal

AbstractWe report on the possible interpretation of the two proposed dark matter mass values mχ=11.6 GeV and mχ=25.3 GeV from CRESST-II within the framework of the Higgs portal minimal dark matter model. We find that the higher mass value yields a suitable fit with a dark matter-Higgs coupling η/2=0.157 and a recoil cross section which is compatible with contemporary estimates of the effective Higgs–nucleon coupling. On the other hand, the lower mass solution would require a large strangeness component in the nucleon to explain the corresponding nucleon recoil cross section reported by CRESST-II.

Radiative corrections to antineutrino-proton scattering at low energies

For the low-energy antineutrino reaction, ${\overline{\ensuremath{\nu}}}_{e}+p\ensuremath{\rightarrow}{e}^{+}+n$, which is of great current interest in connection with on-going high-precision neutrino-oscillation experiments, we calculate the differential cross section in a model-independent effective field theory (EFT), taking into account radiative corrections of order $\ensuremath{\alpha}$. In EFT, the short-distance radiative corrections are subsumed into well-defined low-energy constants, the values of which can in principle be determined from the available neutron $\ensuremath{\beta}$-decay data. In our low-energy EFT, the order-$\ensuremath{\alpha}$ radiative corrections are considered to be of the same order as the nucleon recoil corrections, which include the ``weak magnetism'' contribution. These recoil corrections have been evaluated as well. We emphasize that EFT allows a systematic evaluation of higher order corrections, providing estimates of theoretical uncertainties in our results.

Exclusive production of quarkonia as a probe of the generalized parton distribution for gluons

Exclusive quarkonium photo- and electro-production off the nucleon is studied in the framework of generalized parton distributions (GPDs). The short distance part of the process is treated at leading order in perturbative Quantum Chromodynamics. The main focus is on the GPD E for gluons. On the basis of different models for E we estimate the transverse target spin asymmetry for typical kinematics of a future Electron Ion Collider. We also explore the potential of measuring the polarization of the recoil nucleon.

Beam spin asymmetry of ep → eNπγ reactions with the CLAS detector: pioneering experimental investigation of ΔVCS

The Generalized Parton Distributions (GPDs) parameterize the non-pertubative content of the nucleon. They appear in the amplitude of hard exclusive processes such as DVCS on the proton (ep → epγ). They correlate the spatial and momentum structure of the nucleon in terms of partonic degrees of freedom. The introduction of transition GPDs extended the GPD formalism to more general final states. These GPDs can be used for instance to describe processes where the recoil nucleon is excited into a nucleon resonance. In this paper we focus on the N-Δ transition. The simplest process to access N-Δ transition GPDs is the ΔVCS (ep → eΔ+γ). First experimental beam spin asymmetry results associated to this process and obtained from CLAS data are presented. The Δ+ decaying into Nπ pair, the analysis focused on the ep → eNπγ reactions in the Δ+ region.

LargeQ2electrodisintegration of the deuteron in the virtual nucleon approximation

The two-body break up of the deuteron is studied at high $Q^2$ kinematics, with main motivation to probe the deuteron at small internucleon distances. Such studies are associated with the probing of high momentum component of the deuteron wave function. For this, two main theoretical issues have been addressed such as electromagnetic interaction of the virtual photon with the bound nucleon and the strong interaction of produced baryons in the final state of the break-up reaction. Within virtual nucleon approximation we developed a new prescription to account for the bound nucleon effects in electromagnetic interaction. The final state interaction at high $Q^2$ kinematics is calculated within generalized eikonal approximation (GEA). We studied the uncertainties involved in the calculation and performed comparisons with the first experimental data on deuteron electrodisintegration at large $Q^2$. We demonstrate that the experimental data confirm GEA's early prediction that the rescattering is maximal at $\sim 70^0$ of recoil nucleon production relative to the momentum of the virtual photon. Comparisons also show that the forward recoil nucleon angles are best suited for studies of the electromagnetic interaction of bound nucleons and the high momentum structure of the deuteron. Backward recoil angle kinematics show sizable effects due to the $\Delta$-isobar contribution. The latter indicates the importance of further development of GEA to account for the inelastic transitions in the intermediate state of the electrodisintegration reactions.

Investigation of the anomaly in η-photoproduction off the neutron

Quasi-free photoproduction of η-mesons off the neutron and off the proton has been studied using a deuterium target and bremsstrahlung photons produced by MAMI-C with incident energies up to 1.5 GeV. The η-mesons were detected in coincidence with the recoil nucleons thus a fully exclusive measurement was performed. Preliminary results show a bump-like structure in the excitation function for the neutron close to W ≈ 1675 MeV which is not seen for the proton. Considering the experimental resolution and using a Breit-Wigner fit the width of this structure was approximated below 50 MeV.

Chiral effective field theory calculations of neutrino processes in dense matter

We calculate neutrino processes involving two nucleons at subnuclear densities using chiral effective field theory. Shorter range noncentral forces reduce the neutrino rates significantly compared with the one-pion exchange approximation currently used in supernova simulations. For densities $\ensuremath{\rho}<{10}^{14} \mathrm{g} {\mathrm{cm}}^{\ensuremath{-}3}$, we find that neutrino rates are well constrained by nuclear interactions and nucleon-nucleon scattering data. As an application, we calculate the mean-square energy transfer in scattering of a neutrino from nucleons and find that collision processes and spin-dependent mean-field effects dominate over the energy transfer due to nucleon recoil.

Nucleon recoil for low-energy antikaon-deuteron scattering

The effect of the nucleon recoil for antikaon-deuteron scattering is studied in the framework of effective field theory. In particular, we performed a calculation of the nucleon recoil effect for the double scattering process. It is shown that the leading correction to the static term that emerges at order ξ1/2, where ξ = mK/MN, vanishes due to a complete cancellation of individually large terms. The resulting recoil effect for the double scattering process is found to be of order of 10–15% compared to the static term. We also developed a method to include the nucleon recoil effect in the calculation of the multiple scattering diagrams.

The role of nucleon recoil in low-energy antikaon-deuteron scattering

The effect of the nucleon recoil for the antikaon-deuteron scattering is investigated in the framework of the effective field theory. In particular, we concentrate on the calculation of the nucleon recoil effect for the double-scattering process. It is shown that the leading correction to the static term that emerges at order \( \xi^{{1/2}}_{}\) with \( \xi\) = M K/m N vanishes due to a complete cancellation of individually large contributions. The resulting recoil effect in this process is found to be of the order of 10-15% as compared to the static term. We also briefly discuss the application of the method in the calculations of the multiple-scattering diagrams.

Track treeing mechanism and plastic zone in solid Part 1: Initial development of plastic zone

After neutron exposure and chemical etching in advance, latent tracks of recoil nucleon develop into pits on CR39 surface. During electrochemical etching, plastic zone is formed at top of pits. Some pits develop into tree cracks in the initial stage of plastic zone development. Physical and mathematical model of crack and plastic zone is proposed; parameter of development free path of plastic zone is presented. Based on integration of elementary theories the stress analysis is build up; based on analyses of measured parameters, a set of common relations between parameters is obtained. Integrate parameter analysis and stress analysis, depth of plastic zone development, law and phenomenon in experimental data can be interpreted completely.

New experimental and simulated results on nuclear media effects in meson photoproduction off nuclei

New experimental approach to study meson photoproduction in nuclei is discussed. It is based on the measurement of the recoil nucleon as a tagger for identification of the initial step of reaction. Propagation of mesons and nucleons within a nucleus is described by the Intra-Nuclear Cascade (INC) model. Simulations and preliminary experimental data for the deuteron target obtained at GRAAL are presented.

Probing new physics in the neutrinoless double beta decay using electron angular correlation

The angular correlation of the electrons emitted in the neutrinoless double beta decay ($0\nu2\beta$) is presented using a general Lorentz invariant effective Lagrangian for the leptonic and hadronic charged weak currents. We show that the coefficient $K$ in the angular correlation $d\Gamma/d\cos \theta \propto (1-K\cos \theta)$ is essentially independent of the nuclear matrix element models and present its numerical values for the five nuclei of interest ($^{76}{Ge}$, $^{82}{Se}$, $^{100}{Mo}$, $^{130}{Te}$, and $^{136}{Xe}$), assuming that the $0\nu2\beta$-decays in these nuclei are induced solely by a light Majorana neutrino, $\nu_M$. This coefficient varies between $K=0.81$ (for the $^{76}{Ge}$ nucleus) and $K=0.88$ (for the $^{82}{Se}$ and $^{100}{Mo}$ nuclei), calculated taking into account the effects from the nucleon recoil, the $S$ and $P$-waves for the outgoing electrons and the electron mass. Deviation of $K$ from its values derived here would indicate the presence of New Physics (NP) in addition to a light Majorana neutrino, and we work out the angular coefficients in several $\nu_M + {NP}$ scenarios for the $^{76}{Ge}$ nucleus. As an illustration of the correlations among the $0\nu2\beta$ observables (half-life $T_{1/2}$, the coefficient $K$, and the effective Majorana neutrino mass $|< m>|$) and the parameters of the underlying NP model, we analyze the left-right symmetric models, taking into account current phenomenological bounds on the right-handed $W_R$-boson mass and the left-right mixing parameter $\zeta$.

Quasielastic channel of single-stage nuclear fission induced by 1-GeV protons

Experimental indications that there exists single-stage fission of 238U and 232Th nuclei that is induced by a nearly transverse flux of intranuclear nucleons are obtained from an experiment that employs a two-arm time-of-flight spectrometer exposed to a beam of 1-GeV protons. A nearly transverse flux of mean multiplicity about 10 to 15 nucleons is initiated by a recoil nucleon of mean momentum about 240 MeV/c in the quasielastic scattering of an incident proton.

Role of excited nuclear states in photoabsorption shadowing at medium energies

The effect of intranuclear motion of nucleons on the photoabsorption shadowing due to the conversion of a γ-ray photon into a vector meson in nuclear matter is analyzed. It is shown within the method of time-correlation functions that, in comparison with the results of the standard approach, the correction to the total photoabsorption cross section due to the nuclear shadowing is determined by two additional factors: the Fermi motion of nucleons in a nucleus and nucleon recoil.

A study of the cross sections and the spin observables for proton-12C elastic scattering in momentum space in the intermediate energy region

The differential cross sections and the spin observables of p-12C elastic scattering in the whole intermediate energy region are calculated using the KMT multiple scattering theory with microscopic momentum space optical potential which incorporates the spin dependence of the NN and p-12C interactions. The theory takes into consideration the antisymmetrized NN amplitudes, nucleon recoil and binding energy shifts, Lorentz invariant angle transformations, t matrices with on-shell behavior from NN phase shifts,and off-shell behavior from a realistic separable potential model. Qualitative agreement is found in differential cross sections and polarization data for 200Ep&lt;1000 MeV.

Model independent method for determination of the DIS structure of free neutron

We present a model independent procedure for extracting deep-inelastic structure function of “free” neutron from the electron–deuteron scattering with protons produced in the target fragmentation region of the reaction. This procedure is based on the extrapolation of t, which describes the invariant momentum transfered to the proton, to the unphysical region corresponding to the mass of the struck neutron. We demonstrate that the impulse approximation diagram of the reaction has a pole at this limit with a residue being proportional to the “free” neutron structure function. The method is analogous to that of Chew and Low for extraction of the “free” pion–pion and neutron–neutron cross sections from p(π,p)X and d(n,n)pn reactions, respectively. We demonstrate that in the extrapolation the final state interaction amplitudes are smooth functions of t and have negligible contribution in the extracted “free” nucleon structure function. We also estimate the range of the recoil nucleon momenta which could be used for successful extrapolation procedure.

Two-dimensional hydrodynamic core-collapse supernova simulations with spectral neutrino transport

Supernova models with a full spectral treatment of the neutrino transport are presented, employing the PROMETHEUS/VERTEX neutrinohydrodynamics code with a variable Eddington factor closure of the O(v/c) moments equations of neutrino number, energy, and momentum. Our ray-by-ray plus approximation developed for two- (or three-) dimensional problems assumes that the local neutrino distribution function is azimuthally symmetric around the radial direction, which implies that the nonradial flux components disappear. Other terms containing the angular velocity components are retained in the moments equations and establish a coupling of the transport at different latitudes by lateral derivatives. Also lateral components of the neutrino pressure gradients are included in the hydrodynamics equations. This approximative approach for neutrino transport in multi-dimensional environments is motivated and critically assessed with respect to its capabilities, limitations, and inaccuracies in the context of supernova simulations. In this first paper of a series, one- (1D) and two-dimensional (2D) core-collapse calculations for a (nonrotating) 15 M ○. star are discussed, uncertainties in the treatment of the equation of state - numerical and physical - are tested, Newtonian results are compared with simulations using a general relativistic potential, bremsstrahlung and interactions of neutrinos of different flavors are investigated, and the standard approximation in neutrino-nucleon interactions with zero energy transfer is replaced by rates that include corrections due to nucleon recoil, thermal motions, weak magnetism, and nucleon correlations. Models with the full implementation of the ray-by-ray plus spectral transport were found not to explode, neither in spherical symmetry nor in 2D when the computational grid is constrained to a lateral wedge (<±45°) around the equator. The success of previous two-dimensional simulations with grey, flux-limited neutrino diffusion can therefore not be confirmed. An explosion is obtained in 2D for the considered 15 M ○. progenitor, when the radial velocity terms in the neutrino momentum equation are omitted. This manipulation increases the neutrino energy density in the convective gain layer by about 20-30% and thus the integral neutrino energy deposition in this region by about a factor of two compared to the non-exploding 2D model with the full transport. The spectral treatment of the transport and detailed description of charged-current processes leads to proton-rich neutrino-heated ejecta, removing the problem that previous explosion models with approximate neutrino treatment overproduced N = 50 closed neutron shell nuclei by large factors.

Exclusive electrodisintegration ofHe3at highQ2. I. Generalized eikonal approximation

We develop a theoretical framework for calculation of high-${Q}^{2}$ exclusive electrodisintegration of $A=3$ systems. The main result of this work is the calculation of the final state interaction of the struck energetic nucleon with recoil nucleons within the generalized eikonal approximation (GEA), which allows us to account for the finite and relatively large momenta of the bound nucleons in the nucleus. This approach makes it possible to study in a self-consistent way the short-range correlations in nuclei. This is because the GEA does not require a stationary condition for recoil nucleons as does the conventional Glauber approximation. As a result GEA treats explicitly the Fermi motion of recoil nucleons in the nucleus.

RELATIVISTIC DESCRIPTION OF QUASIFREE ETA PHOTOPRODUCTION

A relativistic plane wave formalism for quasifree eta meson photoproduction is presented. The sensitivity of the unpolarized differential cross section, the recoil nucleon polarization, and the photon asymmetry is investigated. The results indicate that the S11 resonance dominates the unpolarized differential cross section, but that its contribution to the spin observables are very small, for which the D13 resonance plays the primary role.

Spectrum of recoil nucleons in quasi-elastic neutrino-nucleus interactions

We have analyzed the consequences of introducing the local density approximation combined with an effective nuclear momentum-dependent potential into the CC quasi-elastic neutrino-nucleus scattering. We note that the distribution of recoil nucleons momenta becomes smooth for low momentum values and the sharp threshold is removed. Our results may be relevant for Sci-Fi detector analysis of K2K experiments. The total amount of observed recoil protons is reduced because some of them remain bound inside the nucleus. We compare theoretical predictions for a probability of such events with the results given by NUX + FLUKA MC simulations.