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D. Frekers

Publications and source records attributed to D. Frekers.

27 records · Page 2Linked to original sources
arXiv2010

Measurement of the atmospheric muon charge ratio with the OPERA detector

The OPERA detector at the Gran Sasso underground laboratory (LNGS) was used to measure the atmospheric muon charge ratio in the TeV energy region. We analyzed 403069 atmospheric muons corresponding to 113.4 days of livetime during the 2008 CNGS run. We computed separately the muon charge ratio for single and for multiple muon events in order to select different energy regions of the primary cosmic ray spectrum and to test the charge ratio dependence on the primary composition. The measured charge ratio values were corrected taking into account the charge-misidentification errors. Data have also been grouped in five bins of the "vertical surface energy". A fit to a simplified model of muon production in the atmosphere allowed the determination of the pion and kaon charge ratios weighted by the cosmic ray energy spectrum.

hep-ex↗
arXiv2009

Nuclear-atomic state degeneracy in neutrinoless double-electron capture: A unique test for a Majorana-neutrino

There is a general consensus that detection of a double-beta decay without any neutrino involved would mark physics beyond the Standard Model. This is because in such decay modes lepton number conservation would be violated and the neutrino would reveal itself as being its own antiparticle, thereby of Majorana type. So far, the experimental focus has mostly been on the double beta minus decay variant, where one attempts to measure the spectrum of the two emitted electrons. A discrete line at the endpoint energy marks the unique signature for a Majorana neutrino. Little attention has been given to alternative decay modes in double-beta decay. In this note we show that there is at least one case in the periodic table, where the parent in the neutrinoless double-electron capture process is nearly degenerate with an excited state in the daughter, leading to a possible enhancement of the decay rate by several orders of magnitude. It is the nucleus 74-Se, which has this unique property. Furthermore, there is an easy to detect 2 gamma-ray decay cascade in 74-Ge, which follows the zero-neutrino double electron capture, and which by its mere detection provides unique signature of the Majorana neutrino.

hep-ex↗
arXiv2004

Nuclear Input for Core-collapse Models

We review the nuclear physics input necessary for the study of the collapse of massive stars as precursor to supernova explosions. Recent theoretical advances for the calculation of the relevant weak-interaction processes and their influence in the collapse and postbounce dynamics are discussed. Future improvements are expected to come with the advent of radioactive ion-beam facilities.

astro-ph↗
arXiv2003

Testing quantum correlations with nuclear probes

We investigated the feasibility of quantum-correlation measurements in nuclear physics experiments. In a first approach, we measured spin correlations of singlet-spin (1S0) proton pairs, which were generated in 1H(d,2He) and 12C(d,2He) nuclear charge-exchange reactions. The experiment was optimized for a clean preparation of the 2He singlet state and offered a 2pi detection geometry for both protons in the exit channel. Our results confirm the effectiveness of the setup for theses studies, despite limitations of a small data sample recorded during the feasibility studies.

quant-ph↗
arXiv2003

Polarization Correlations of 1S0 Proton Pairs as Tests of Bell and Wigner Inequalities

In an experiment designed to overcome the loophole of observer dependent reality and satisfying the counterfactuality condition, we measured polarization correlations of 1S0 proton pairs produced in 12C(d,2He) and 1H(d,He) reactions in one setting. The results of these measurements are used to test the Bell and Wigner inequalties against the predictions of quantum mechanics.

quant-ph↗
arXiv2000

Simultaneous Measurements of the $p+d\to (A=3) +π$ Reactions

A stack of annular detectors made of high purity germanium was used to measure simultaneously $pd\to {^3H} π^+$ and $pd\to {^3He} π^0$ differential cross sections at beam momenta of 750 MeV/c, 800 MeV/c, and 850 MeV/c over a large angular range. The extracted total cross sections for the $pd\to {^3He} π^0$ reactions bridge a gap between near threshold data and those in the resonance region. The ratio of the cross sections for the two reaction channels taken at the same $η={p^{cm}_π}/m_π$ yields $2.11\pm0.08$ indicating that a deviation from isospin symmetry is very small.

nucl-ex↗
arXiv2000

Meson Production in p+d Reactions

The production of neutral and charged pions as well as eta mesons is studied in the Delta and N* resonance region, respectively. Heavy A=3 recoils were measured with the GEM detector. The differential cross sections covering the full angular range are compared with model calculations.

nucl-ex↗
arXiv1999

Measurement of p + d -> 3He + eta in S(11) Resonance

We have measured the reaction p + d -> 3He + eta at a proton beam energy of 980 MeV, which is 88.5 MeV above threshold using the new ``germanium wall'' detector system. A missing--mass resolution of the detector system of 2.6% was achieved. The angular distribution of the meson is forward peaked. We found a total cross section of (573 +- 83(stat.) +- 69(syst.))nb. The excitation function for the present reaction is described by a Breit Wigner form with parameters from photoproduction.

nucl-ex↗