The European Physical Journal A最新文献

A method to measure the angular differential cross section of (n, (alpha )) reactions using gridded ionization chamber (GIC) and gas sample was established. The anode signal rise time is used to get the projection length of the track in the direction of the electric field (related to the ({alpha }) emission angle). The anode signal amplitude is used to distinguish the events with the same anode signal rise time but different ({alpha }) emission angles because of the PHD (pulse height defect) effect. Using this method, the angular differential cross sections of the (^{16})O(n, (alpha _0))(^{13})C reaction at 10.45 MeV were measured based on the HI-13 tandem accelerator of China Institute of Atomic Energy (CIAE). The GIC was used as the charged particle detector, with working gas of 3.0 atm Kr+4.0%CO(_2). The oxygen atoms in the CO(_2) were used as the sample. Anode signal amplitude vs the anode signal rise time two-dimensional spectrum was used in this method to determine the count of the (^{16})O(n, (alpha _0))(^{13})C reaction events. A (^{238})U(_3)O(_8) sample inside the GIC was used to determine the neutron fluences and an EJ-309 scintillation detector was placed on the beam line to measure the neutron energy spectra to correct the events induced by the low-energy neutrons.

Data from a previous study of (^{110})Cd with the ((n,n^{prime }gamma )) reaction with monoenergetic neutrons have been reanalysed with the aim of identifying additional low-intensity (gamma )-ray transitions. The data set included excitation functions measured with neutron energies between 1.94 and 3.34 MeV, and (gamma )-ray angular distributions performed at neutron energies of 2.6, 2.9, and 3.2 MeV. A total of 162 (gamma ) rays were placed in a level scheme comprising 69 levels (of which 58 (gamma )-ray assignments and 10 levels are newly established) up to 3.3 MeV in excitation energy. Lifetimes, or limits, were established for many levels using the Doppler-shift attenuation technique allowing for the determination of an extended set of transition rates.

The potential of the intense secondary muon, neutrino, and (hypothetical) light dark matter beams at the Thomas Jefferson National Accelerator Facility (Jefferson Lab) is explored. These are produced in the high-power dumps with high-current electron beams. Light dark matter searches with the approved Beam Dump eXperiment (BDX) are driving the realization of a new underground vault behind Hall A that could be extended to a Beamdump Facility with little additional installations. High-energy muons created via the Bethe–Heitler process uniquely do not proceed through the more common pion production and decay channels. Several possible muon physics applications are highlighted. Neutrino detector technologies and experiments suitable for a beamdump facility are outlined.

The FAMU experiment, supported and funded by the Italian Institute of Nuclear Physics (INFN) and by the Science and Technology Facilities Council (STFC), aims to perform the first measurement of the ground-state hyperfine splitting (1S-hfs) of muonic hydrogen ((mu H)). This quantity is highly sensitive to the proton’s Zemach radius (R_Z). An experimental determination of (R_Z) provides significant constraints on the parametrisation of the proton form factors as well as on theoretical models describing the proton’s electromagnetic structure. Following years of technological and methodological development, the FAMU experiment began operations in 2023 at Port 1 of the RIKEN-RAL muon beam line at the ISIS Neutron and Muon Source facility (Didcot, UK). In this paper, we first describe the unique detection technique employed by FAMU to determine the 1S-hfs of muonic hydrogen, followed by a detailed presentation of the final experimental layout. Finally, we report the first outcome from the 2023 commissioning run and from the initial physics runs performed in 2023 and 2024.

Triton and helion nonlocal optical potentials are constructed from available global systematics of nonlocal nucleon optical potentials using a single-folding procedure. With nucleon optical potentials of the Perey-Buck type, used here, and simple gaussian triton/helion wave functions, the triton and helion nonlocal folding potentials are also of the Perey-Buck type with a nonlocality range being a third of that for a nucleon. The scattering problem with such potentials is solved exactly and the cross sections obtained are compared to those obtained in its local-equivalent model at the leading and next-to-leading orders. It was found that leading-order angular distributions are almost indistinguishable from those given by the exact solution. Constructing local triton/helion folding potentials from local equivalents of nonlocal nucleon potentials gives a different result, making this procedure unsuitable. A comparison with experimental data has been carried out for triton and helion scattering from (^{40})Ca, (^{89})Y and (^{90})Zr targets at laboratory energies between 20 and 130 MeV. With no renormalization of the folding potential the forward angle scattering is reproduced reasonably well and thus is deemed suitable for rearrangement reactions studies at forward angles. At larger angles the predictions overestimate the scattering data and underestimate absorption cross sections. Recommendation to further improvement of the model to address the lack of absorption in that area is given.

In this paper, we analyze the relativistic energy spectrum (or relativistic Landau levels) for charged Dirac fermions with anomalous magnetic moment (AMM) in the presence of the chiral magnetic effect (CME) and of a noncommutative (NC) phase space, where we work with the ((3+1))-dimensional Dirac equation in cylindrical coordinates. Using a similarity transformation, we obtain four coupled first-order differential equations. Subsequently, we obtain four non-homogeneous second-order differential equations. To solve these equations exactly and analytically, we use a change of variable, the asymptotic behavior, and the Frobenius method. Consequently, we obtain the relativistic spectrum for the electron/positron, where we note that this spectrum is quantized in terms of the radial quantum number n and the angular quantum number (m_j), and explicitly depends on the helicity h (describes the projection of spin in the direction of linear momentum), position and momentum NC parameters (theta ) and (eta ) (describes the NC phase space), (an angular frequency that depends on the electric charge e, mass m, and external magnetic field B, i.e., (omega _c=eB/m)) anomalous magnetic energy (E_m) (an energy generated through the interaction of the AMM with the magnetic field), z-momentum (k_z) (linear momentum along the z-axis), and on the fermion and chiral chemical potential (mu ) and (mu _5) (describes the CME). However, through (theta ,) (eta ,) and m,  we define two types of “NC angular frequencies”, given by (omega _theta =4/mtheta ) and (omega _eta =eta /m) (i.e., our spectrum depends on three angular frequencies). Comparing our spectrum with other papers, we verified that it generalizes several particular cases found in the literature. Besides, we also graphically analyze the behavior of the spectrum as a function of B,  (mu ,) (mu _5,) (k_z,) (theta ,) and (eta ) for three different values of n and (m_j.)

We have determined the decay energy (Q value) of the double beta decay of (^{122})Sn with the JYFLTRAP double Penning trap mass spectrometer using the Phase-Imaging Ion Cyclotron Resonance technique. Our new Q value, 373.58(12) keV, agrees with the literature value but is 20 times more precise. We also measured the Q value for the double beta decay of (^{124})Sn with unprecedented precision, 2293.542(83) keV. The Q values of (^{122})Sn and (^{124})Sn were used to calculate precisely the phase-space factors for the neutrinoless double beta ((0nu beta beta )) decay mode of these nuclei. With the phase-space factor and our computed nuclear matrix elements (NMEs) we predict the (0nu beta beta )-decay half-life of (^{122})Sn based on the recently extracted upper limit of the effective neutrino mass by the KamLAND-Zen experiment. We used three nuclear-structure frameworks to compute the NMEs, namely the proton-neutron quasiparticle random-phase approximation (pnQRPA), the microscopic interacting boson model (IBM-2), and a hybrid model exploiting both the pnQRPA and the nuclear shell model (NSM). We find that including the short-range components enhances the total NME in the IBM-2 model, making it significantly larger than the NMEs calculated with the pnQRPA and hybrid models. Nevertheless, for all models, the obtained half-lives are very long for (^{122})Sn ( (approx 10^{27})–(10^{29}) years), making the observation of (0nu beta beta ) decay of (^{122})Sn experimentally challenging. On the other hand, the hybrid-model calculated value of the NME for (^{124})Sn goes, interestingly enough, toward those previously computed by the NSM and the ab initio model.

This review summarizes the state of knowledge of the (^{12})C+(^{12})C fusion reaction and its impact on stellar carbon burning environments.

Taking the stable and neutron-rich oxygen and calcium isotopes as cores, we investigate the structure of multi-(Lambda ) hypernuclei with the Skyrme Hartree–Fock–Bogoliubov model. So far, the observed rare double-(Lambda ) hypernuclei events can only provide information for the S-wave (Lambda Lambda ) interaction, but not for the P-wave. Therefore, in this paper we perform several trials of the strength of P-wave (Lambda Lambda ) interaction, and discuss its effect on the properties for the multi-(Lambda ) hypernuclei. We find that different strengths of P-wave interaction will influence the (Lambda ) hyperon drip line in the neutron-rich hypernuclei, but not much in the hypernuclei with a stable core. The diffused (Lambda ) hyperon mean-field potential in the neutron-rich core makes the single (Lambda ) orbits more bound than in the stable core. Thus, the (Lambda ) continuum states are easier to be pulled down to be weakly bound states with attractive P-wave interaction strength as more (Lambda ) hyperons are added.