Incident Momentum Research Articles

Contributions of various mechanisms of pion production into kinematical spectra of negative pions in collisions of deuterons with 12C nuclei at incident momentum of 4.2 GeV/c per nucleon

Contributions of various mechanisms of pion production into kinematical spectra of negative pions in collisions of deuterons with 12C nuclei at incident momentum of 4.2 GeV/c per nucleon

Missing-Mass Measurement of the 12C(K-, K+) Reaction at 1.8 GeV/c with the Superconducting Kaon Spectrometer

Abstract We performed a measurement of the inclusive missing-mass spectrum of the $^{12}$C$(K^-, K^+)$ reaction at an incident beam momentum of 1.8 GeV/c. This measurement was carried out by using the Superconducting Kaon Spectrometer (SKS) and the K1.8 beamline spectrometer at the Hadron Experimental Facility in J-PARC. From the missing-mass of the $^{12}$C$(K^-, K^+)$ reaction, the binding energy of a $\Xi ^-$ hyperon in a core $^{11}$B nucleus, $B_{\Xi ^-}$, can be calculated. Our experimental setup yielded a good energy resolution of 8.2 MeV (full width at half maximum), which allowed us to observe significant enhancements in the proximity of the $^{12}_{\Xi }$Be production threshold region. In order to extract information from the missing-mass spectrum, we employed several fitting parameters assumptions. A good agreement with the spectrum shape was obtained by adding two Gaussian functions, with the constant experimental resolution for the $\Xi$-hypernuclear states, to the background distribution. The peak positions were obtained to be $B_{\Xi ^-} = 8.9 \pm 1.4$ (stat.) $^{+3.8}_{-3.1}$ (syst.) MeV and $B_{\Xi ^-} = -2.4 \pm 1.3$ (stat.) $^{+2.8}_{-1.2}$ (syst.) MeV. Another model assumption, one Breit–Wigner function with $B_{\Xi ^-} = -2.7 \pm 2.2$ (stat.) $^{+0.5}_{-0.7}$ (syst.) MeV and $\Gamma = 4.1 \pm 2.1$ (stat.) $^{+1.2}_{-0.7}$ (syst.) MeV, also yielded a similar $\chi ^2$ value.

Revealing the Incidence-Angle-Independent Frequency Shift in the Acoustic Rotational Doppler Effect.

The Doppler effect is a universal wave phenomenon that has inspired various applications due to the induced frequency shift. In the case of the linear Doppler effect, the frequency shift depends on the incident frequency and angle. Here, we unveil the frequency shift dependence induced by the acoustic rotational Doppler effect in the wave-object scattering process. We experimentally demonstrate that this frequency shift is exclusively determined by the angular speed and rotational symmetry of the spinning scatterer while remaining independent of the incident angular momentum and angle. We derive the analytical relationship between the frequency shift and the scatterer's helicity, presenting a novel approach for helical feature recognition. The angle-independent nature of the frequency shift inherently prevents spectrum broadening and offers a solution for precise motion measurement through the rotational Doppler effect. This work provides a rigorous and comprehensive understanding of the acoustic Doppler effect, enriching its applications in helicity and motion detection.

Thermal Mixing and Flow Characteristics Study in a T-Junction

The objective of the current paper is to investigate the turbulent flow characteristics, thermal mixing behavior, and backflow features of coolant fluid in a T-junction using three-dimensional numerical simulations. The impact of critical flow parameters and different branch pipe axial and transverse incident angles on thermal mixing performance are explored as a function of momentum ratio. The investigation identifies the impact of jet flow, deflection flow, and wall jet flow patterns. The results reveal that the upside backflow of T-junction is more significant for a lower momentum ratio (<0.32) and decreases with higher momentum ratio (0.32 < momentum ratio < 2.7). The efficiency of thermal mixing is considerably improved by changing the incident angle and momentum ratio. Thermal mixing length decreases by ∼39%, 28%, and 21% as compared to the reference case. The current findings will help researchers to understand flow behavior and thermal mixing in a T-junction. It is also useful in high-temperature engineering applications for the evaluation of thermal cracking and safety management.

The parameter-free Monte Carlo approach for diffractive dissociation of relativistic oxygen nuclei into four alpha particles in interactions with protons at 3.25GeV/c per nucleon

In this paper, we have investigated the processes of formation of four alpha particles in the final state in the reactions [Formula: see text] of diffractive dissociation of oxygen-16 nuclei in interactions with protons at an incident momentum of 3.25[Formula: see text]GeV/[Formula: see text] per nucleon. A Monte Carlo model is proposed to describe the kinematic characteristics of the produced alpha particles. The proposed Monte Carlo model does not have any free parameters. The algorithm of the model takes into account the energetically allowed channels of direct (or cascade) decays of the excited oxygen-16 nuclei into the final four alpha particles. To form the masses of the excited oxygen-16, carbon-12, and beryllium-8 nuclei, the experimental tables of their excitation levels have been used. All decays have been generated isotropically in the rest frame of each unstable nucleus — the excited oxygen-16, carbon-12, and beryllium-8 nuclei. The results of the Monte Carlo model calculations have proved to be in good agreement with distributions of various kinematic characteristics of the final state alpha particles taken from the experiment. The good agreement is reached if, after simulation of the mass of the excited oxygen-16, the energetically allowed decay channel is selected for which the sum of the total energy, released in this channel, and the masses of the four secondary alpha particles turn out to be less, but closest to the mass of the excited oxygen-16 nucleus. At a high level of excitation, there are several channels with the same energy release, which have been generated with equal probabilities.

Multi-mode optical chirality extremizations on the incident momentum sphere.

We study the momentum-space evolutions for chiral optical responses of multi-mode resonators scattering plane waves of varying incident directions. It was revealed, in our previous study [Phys. Rev. Lett.126, 253901 (2021)10.1103/PhysRevLett.126.253901], that for single-mode resonators the scattering optical chiralities characterized by circular dichroism (CD) are solely decided by the third Stokes parameter distributions of the quasi-normal mode (QNM) radiations: CD = S3. Here we extend the investigations to multi-mode resonators, and explore numerically the dependence of optical chiralities on incident directions from the perspectives of QNM radiations and their circular polarization singularities. In contrast to the single-mode regime, for multi-mode resonators it is discovered that CDs defined in terms of extinction, scattering and absorption generally are different and cannot reach the ideal values of ±1 throughout the momentum sphere. Though the exact correspondence between CD and S3 does not hold anymore in the multi-mode regime, we demonstrate that the positions of the polarization singularities still serve as an efficient guide for identifying those incident directions where the optical chiralities can be extremized.

Orbital period change of Dimorphos due to the DART kinetic impact

The Double Asteroid Redirection Test (DART) spacecraft successfully performed the first test of a kinetic impactor for asteroid deflection by impacting Dimorphos, the secondary of near-Earth binary asteroid (65803) Didymos, and changing the orbital period of Dimorphos. A change in orbital period of approximately 7 min was expected if the incident momentum from the DART spacecraft was directly transferred to the asteroid target in a perfectly inelastic collision1, but studies of the probable impact conditions and asteroid properties indicated that a considerable momentum enhancement (β) was possible2,3. In the years before impact, we used lightcurve observations to accurately determine the pre-impact orbit parameters of Dimorphos with respect to Didymos4–6. Here we report the change in the orbital period of Dimorphos as a result of the DART kinetic impact to be −33.0 ± 1.0 (3σ) min. Using new Earth-based lightcurve and radar observations, two independent approaches determined identical values for the change in the orbital period. This large orbit period change suggests that ejecta contributed a substantial amount of momentum to the asteroid beyond what the DART spacecraft carried.

Instantaneous tunneling of relativistic massive spin-0 particles

The tunneling time problem studied earlier in Phys. Rev. Lett., 108 (2012) 170402, using a non-relativistic time-of-arrival (TOA) operator predicted that tunneling time is instantaneous. This raises the question whether instantaneous tunneling time is a consequence of using a non-relativistic theory. Here, we extend the analysis by proposing a formalism on the construction of relativistic TOA operators for spin-0 particles in the presence of an interaction potential V (q) via quantization. We then construct the corresponding barrier traversal time operator, and impose the condition that the barrier height V o is less than the rest mass energy of the particle. We show that only the above-barrier energy components of the incident wavepackets momentum distribution contribute to the barrier traversal time while the below-barrier components are transmitted instantaneously.

Breakup of oxygen nucleus on four doubly charged fragments in 16O+p interactions at incident momentum of 3.25 GeV/c per nucleon

The new experimental data on breakup of oxygen-16 nucleus on four doubly charged ([Formula: see text]) fragments in [Formula: see text]O[Formula: see text] interactions at 3.25 GeV/[Formula: see text] per nucleon are presented. The number of such interaction events (with the formation of four doubly charged fragments) with simultaneous production of [Formula: see text] with no recoil proton has proved to be equal to the number of events with simultaneous production of [Formula: see text] as well as [Formula: see text] in events with a recoil proton. For the first time, the experimental cross-section of the diffractive dissociation of the oxygen-16 nucleus on four [Formula: see text]-particles in [Formula: see text]O[Formula: see text] interactions at 3.25 GeV/[Formula: see text] per nucleon has been determined to be [Formula: see text] (diffr.)[Formula: see text] mb. The temperature of the diffractive breakup of oxygen nucleus on four [Formula: see text]-particles has been calculated to be [Formula: see text] MeV within the framework of the statistical model of fast fragmentation of Feshbach–Huang–Goldhaber. Using the obtained slope of the integral distribution on the square of a transverse momentum of a recoil proton in the laboratory system for the events of diffractive breakup of an oxygen nucleus on four [Formula: see text]-particles, we have calculated the radius of a target proton to be [Formula: see text] fm, which agrees very well with the corresponding radius, [Formula: see text] fm, determined a few years ago in the Jefferson Lab Proton Radius (PRad) experiment.

Production mechanism and prediction cross sections of unknown neutron-rich 263–265,267–269Lr isotopes in multinucleon transfer reactions based on the dinuclear system model

Within the framework of the dinuclear system model, the production cross sections for producing the new neutron-rich Lr isotopes in the multinucleon transfer reactions with 249Bk and 254Es targets were predicted. The results show that the 124Sn + 254Es reaction has the highest production cross sections, followed by the 130Te + 249Bk reaction. As far as the existing experimental techniques are concerned, 130Te + 249Bk is the most suitable choice. With experimental techniques developing in the future, 124Sn + 254Es is preferable when the thick 254Es target can be prepared. The optimal energy for producing the new neutron-rich Lr isotopes is 1.1 times the Coulomb barrier for both reaction systems, and both reactions produced 263–265,267–269Lr isotopes. The production mechanism of Lr isotopes has been investigated in the 130Te + 249Bk reaction. It is found that the production of Lr isotopes mainly originates from the contribution of quasifission. And the contribution of quasifission gradually decreases with the increase of the incident angular momentum. The final production cross sections for 263–265,267–269Lr in 130Te + 249Bk reaction at E c.m. = 1.10V C are 0.22 μb, 0.13 μb, 0.15 μb, 4.45 nb, 0.62 nb, and 0.03 nb, respectively

Characteristics of secondary particles associated with the leading protons in n12C and p12C collisions at 3.37GeV incident energy

The new experimental data on characteristics of the secondary particles associated with the leading protons in inelastic interactions of projectile neutrons and protons with target carbon nuclei at incident momentum 4.2[Formula: see text]GeV/c (corresponds to incident kinetic energy 3.37[Formula: see text]GeV) have been presented. The dependencies of the average multiplicities of the charged pions and accompanying protons on longitudinal as well as transverse momenta of the leading protons in [Formula: see text]C and [Formula: see text]C collisions at 4.2[Formula: see text]GeV/c have been investigated. The experimental dependencies have been compared systematically with the Monte Carlo calculations using the modified FRITIOF model. On the whole, the kinematical characteristics of the leading protons in [Formula: see text]C and [Formula: see text]C collisions have proved to be practically the same, even though they are formed as a result of different processes. From a systematic comparison of the experimental data with the model calculations, we could conclude that for a realistic description of the studied experimental dependencies it is probably necessary to take into account the interaction of strings for the case when fragmentation of strings occurs not outside of the nucleus (as it is assumed in the model), but inside and, possibly, on the boundary of the nucleus in the modified FRITIOF model.

Detection of particles of dark matter from the spectrum of secondary particles in high-energy proton-proton collisions in a thermodynamic model

In a simple hydrodynamic model, the transverse momentum distributions are found for A hyperons formed in pp collisions at ultrarelativistic energies. The calculated spectra are compared with the experimental data obtained for various colliders in a wide range of proton collision energies, including the data from experiments at the Large Hadron Collider. An interpretation of the transverse momentum spectra of soft photons in pp collisions is proposed, taking into account the X17 boson with a mass of 17 MeV - a new particle, a possible candidate for the role of dark matter particles. A tube model is proposed on the basis of combining two-dimensional quantum chromodynamics and quantum electrodynamics. An interpretation is proposed for the detection of a 38 MeV boson in the spectra of photons emitted in the reactions of protons with carbon nuclei at an incident proton momentum of 5.5 GeV/c. The X38 boson with a mass of 38 MeV has a mass close to the boson mass obtained by us, equal to 35 MeV for an electromagnetic tube. This new particle was discovered in experiments carried out recently in Dubna for the reactionp p + C→2γ + X. To interpret the obtained experimental data on the spectra of emitted photons depending on their mass, it is proposed to use the formulas obtained for massive particles, setting the mass of a boson decaying into two photons equal to 38 MeV. It was proposed to consider bosons X17 and X38 as particles of dark matter.

Parametric scaling of a magnetic field-reversed conducting coil assembly for radiation shielding

• The geometric scalability of a novel form of active magnetic shield is analyzed • This scalable shield offers an expandable shell of concentrated magnetic energy • Tabletop experiments verify computational models of amplifying and canceling magnetic flux We explore the design scalability of an active magnetic shield for protecting against isotropic radiation, such as galactic cosmic rays in deep space. Each shield is composed of two concentric, elliptical layers of circular conducting coils, each arranged like lines of latitude on a globe, with the current modulated to amplify the magnetic field in the layer between the ellipses, and canceling within. The efficacy of this field-reversed array for creating a shell of magnetic energy to protect a central object from isotropic radiation is explored using quantitative analyses of incident particle momentum. The parametric scalings are verified through ANSYS magnetostatic modeling and corresponding 3D-printed test article demonstrations matching vector magnetic field models. The quantitative parameters utilized here can be applied to constrain and optimize magnetic shielding requirements of this type with respect to size, maximum current, total number of coils, and mass. We will also demonstrate that these parametric scalings can help design future experimental tests of this shield type for deflecting any class of incident radiation.

Single and double scattering mechanisms in ionization of helium by electron vortex projectiles

Triple differential cross sections (TDCSs) for electron vortex projectile ionization of helium into the azimuthal plane are calculated using the distorted wave Born approximation. In this collision geometry, the TDCSs at low and intermediate energies exhibit unique qualitative features that can be used to identify single and double scattering mechanisms. In general, our results predict that the ionization dynamics for vortex projectiles are similar to those of their non-vortex counterparts. However, some key differences are observed. For non-vortex projectiles, a double scattering mechanism is required to emit electrons into the azimuthal plane, and this mechanism becomes more important with increasing energy. Our results demonstrate that for vortex projectiles, emission into the azimuthal plane does not require a double scattering mechanism, although this process still significantly influences the shape of the TDCS at higher energies. At low projectile energies, non-vortex ionization proceeds primarily through single binary collisions. The same is generally true for vortex projectiles, although our results indicate that double scattering is also important, even at low energy. Vortex projectiles have an inherent uncertainty in their incident momentum, which causes a broadening of the binary peak at all energies and results in a splitting of the binary peak at higher energies. The results presented here lead to several predictions that can be experimentally tested.

Physical meaning of the deviation scale under arbitrary turbulence strengths of optical orbital angular momentum.

The recently so-called deviation scale [Phys. Rev. A99, 013828 (2019)PLRAAN1050-294710.1103/PhysRevA.99.013828] bridges the connection between the result of the infinitesimal propagation equation (IPE) prediction and that of the single phase screen (SPS) approximation. Thanks to the multiple phase screen (MPS) approach, in this paper we elaborate the physical meaning of the deviation scale: the spatial accumulation of slight intensity modulation of incident orbital angular momentum (OAM)-carrying beam splits the original vortex into multiple individual vortices with a topological charge (TC) of +1 and regenerates the vortex-antivortex pairs with a TC of +1 and with a TC of -1, leading to a significant deviation between these two different results only when the disruption of this compound effect on the phase distribution of the incident OAM-carrying beam becomes more significant. Other than that, we also show that the appearance of the deviation scale cannot be predicted only by the Rytov variance, which can be predicted through the vortex-splitting ratio of the received optical field alone or with the help of the normalized propagation distance.

New features in the surface plasmon induced photon drag effect in noble metal thin films

We study light–matter interactions leading to the generation of photon drag voltage under surface plasmon resonance conditions in noble metal thin films and observe important effects, which provide opportunity for condensed matter theorists to critically evaluate theoretical models. The drag voltage originates from a force that arises because of the transfer of momentum from incident light to electrons. This transfer of photon momentum leads to an electric current, which in turn results in the generation of drag voltage. The effect is particularly enhanced under surface plasmon resonance conditions and thereby reinforces the interaction between light and collective oscillations of the surface charges. We observe relatively high voltages with a nonlinear dependence on laser intensity. In disagreement with previous results, we do not observe a reversal in the sign of the voltage when the direction of the incident laser momentum is reversed. Qualitative analyses of the data show that the hydrodynamic model of laser-induced drag voltage does not work: the hydrodynamic model predicts voltages that are nine orders of magnitude lower than our measurements. However, there is reasonable consistency between the results of the measurements and numerical simulations.

Characteristics of negative pions produced in dC collisions at 4.2 GeV/c per nucleon

Temperature is considerably an important and commonly used parameter to study characteristics of matter formed during high-energy nuclear collisions. Experimental data from JINR and UrQMD (latest code 3.3p2) models’ simulations have been used to estimate the temperature and other properties of negative pions in collisions of deuteron with carbon nuclei at an incident momentum of 4.2 GeV/c. Transverse mass and transverse momentum spectra have been used to get the temperature of said particles, with the help of some fittings. These fittings are referred to as Hagedorn Thermodynamic and Boltzmann Distribution functions. Such functions or equations are used to describe the particles spectra. Temperature of negative pions has been found to be equal to 98 ± 2 and 114 ± 2 MeV in experimental and model, respectively, using Hagedorn function. Results from both experimental and model calculations have also been compared with each other and thus most reliable fitting function has been suggested. It is found that Hagedorn Thermodynamic function is the most reliable function to get pions’ temperature in said collision system at given incident momentum. Similarly temperature obtained in this research has been compared with results from other experiments in the world and worthy conclusions have been reached and reported.

On Event-by-event Pseudorapidity Fluctuations in Relativistic Nuclear Interactions

Present study is an attempt to have a detailed look into event-by-event(e-by-e) pseudorapidity fluctuations of the relativistic charged particles produced in $^{28}$Si-nucleus interactions at incident momenta 4.5A and 14.5A GeV/c.The method used in the present study makes use of a kinematic variable which is derived in terms of the average pseudo-rapidity and the total number of particles produced in a single event. The multiplicity and pseudorapidity dependence of these fluctuations have also been studied. The results obtained for the experimental data are compared with HIJING simulation.

Transparent mirror effect in twist-angle-disordered bilayer graphene

When light is incident on a medium with spatially disordered index of refraction, interference effects lead to near-perfect reflection when the number of dielectric interfaces is large, so that the medium becomes a "transparent mirror." We investigate the analog of this effect for electrons in twisted bilayer graphene (TBG), for which local fluctuations of the twist angle give rise to a spatially random Fermi velocity. In a description that includes only spatial variation of Fermi velocity, we derive the incident-angle-dependent localization length for the case of quasi-one-dimensional disorder by mapping this problem onto one dimensional Anderson localization. The localization length diverges at normal incidence as a consequence of Klein tunneling, leading to a power-law decay of the transmission when averaged over incidence angle. In a minimal model of TBG, the modulation of twist angle also shifts the location of the Dirac cones in momentum space in a way that can be described by a random gauge field, and thus Klein tunneling is inexact. However, when the Dirac electron's incident momentum is large compared to these shifts, the primary effect of twist disorder is only to shift the incident angle associated with perfect transmission away from zero. These results suggest a mechanism for disorder-induced collimation, valley filtration, and energy filtration of Dirac electron beams, so that TBG offers a promising new platform for Dirac fermion optics.

An event excess observed in the deeply bound region of the 12C (K−, p) missing-mass spectrum

Abstract We have measured, for the first time, the inclusive missing-mass spectrum of the $^{12}$C$(K^-, p)$ reaction at an incident kaon momentum of 1.8 GeV/$c$ at the J-PARC K1.8 beamline. We observed a prominent quasi-elastic peak ($K^-p \rightarrow K^-p$) in this spectrum. In the quasi-elastic peak region, the effect of secondary interaction is apparently observed as a peak shift, and the peak exhibits a tail in the bound region. We compared the spectrum with a theoretical calculation based on the Green’s function method by assuming different values of the parameters for the $\bar{K}$–nucleus optical potential. We found that the spectrum shape in the binding-energy region $-300 \, \text{MeV} &amp;lt; B_{K} &amp;lt; 40$ MeV is best reproduced with the potential depths $V_0 = -80$ MeV (real part) and $W_0 = -40$ MeV (imaginary part). On the other hand, we observed a significant event excess in the deeply bound region around $B_{K} \sim 100$ MeV, where the major decay channel of $K^- NN \to \pi\Sigma N$ is energetically closed, and the non-mesonic decay modes ($K^- NN \to \Lambda N$ and $\Sigma N$) should mainly contribute. The enhancement is fitted well by a Breit–Wigner function with a kaon-binding energy of 90 MeV and width 100 MeV. A possible interpretation is a deeply bound state of a $Y^{*}$-nucleus system.