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International audience; PUMA, antiProton Unstable Matter Annihilation, is a nuclear-physics experiment at CERN aiming at probing the surface properties of stable and rare isotopes by use of low-energy antiprotons. Low-energy antiprotons offer a very unique sensitivity to the neutron and proton densities at the annihilation site, i.e. in the tail of the nuclear density. Today, no facility provides a collider of low-energy radioactive ions and low-energy antiprotons: while not being a collider experiment, PUMA aims at transporting one billion antiprotons from ELENA, the Extra-Low-ENergy Antiproton ring, to ISOLDE, the rare-isotope beam facility of CERN. PUMA will enable the capture of low-energy antiprotons by short-lived nuclei and the measurement of the emitted radiations. In this way, PUMA will give access to the so-far largely unexplored isospin composition of the nuclear-radial-density tail of radioactive nuclei. The motivations, concept and current status of the PUMA experiment are presented.

The present knowledge of nuclear forces is not sufficient to describe all experimental data for systems which consist of more than two nucleons. Recent three-nucleon scattering experiments have shown that the theoretical models based solely on nucleon-nucleon potentials fail to describe most of the experimental results. In this paper, we present data of the \(\vec {p}+d \longrightarrow p+p+n \) break-up reaction that were obtained using a 190 MeV polarized-proton beam impinging on a liquid deuterium target. The experiment was performed by exploiting BINA (Big Instrument for Nuclear-polarization Analysis), a detector system with a large angular acceptance and a high energy resolution.

In this contribution, vector analyzing powers are presented for the proton-deuteron break-up reaction studied using a polarised-proton beam at 135 MeV. For the experiment, we used the Big Instrument for Nuclear-polarisation Analysis (BINA) at KVI, the Netherlands. With this setup, we determined, for the first time, (formula presented) for a large range in the kinematical S, polar and azimuthal angles of the two outgoing protons. Our data are reasonably well described by Faddeev calculations for kinematical configurations at which the three-nucleon force effect is predicted to be small. However, striking discrepancies are observed at specific configurations, for which the relative azimuthal angle between the two protons becomes small. In this contribution, some of these configurations along with the analysis techniques are presented.

A measurement of the analyzing powers for the \(^{2}\mathrm{H}(\mathbf {p},pp)n\) break-up reaction was carried out at KVI exploiting a polarized-proton beam at 135 MeV. The results are compared with theoretical calculations. The theoretical calculations describe the main features of the measured distributions, but none of them can reproduce the details. This indicates the need for further development of the three-nucleon force (3NF) models.

In this contribution, the results for the differential cross sections and a rich set of vector and tensor analyzing powers are presented for various configurations of the three-body break-up channel of (formula presented). The data were obtained at KVI using a polarised deuteron beam with a beam energy of 65 MeV/nucleon and a liquid deuterium target in combination with a (formula presented) detection system carrying the name Big-Instrument for Nuclear-Polarization Analysis (BINA). This work extends the results from an earlier study reported in [1]. In particular, additional kinematical configurations and spin observables were analyzed and obtained.

Antiprotons as a probe to study short-lived isotopes remain unexploited despite past pioneering works with stable nuclei. In particular, low-energy antiprotons offer a very unique sensitivity to the neutron and proton densities at the annihilation site, i.e. in the tail of the nuclear density. Such studies with short-lived nuclei and low-energy antiprotons are the first motivation of the proposed antiProton Unstable Matter Annihilation (PUMA) experiment. Today, no facility provides a collider of low-energy radioactive ions and low-energy antiprotons: PUMA aims at transporting one billion antiprotons from CERN/ELENA to CERN/ISOLDE to perform the capture of low-energy antiprotons by short-lived nuclei, and probe in this way the so-far unexplored isospin composition of the nuclear-radial-density tail of radioactive nuclei.

The vector and tensor analysing powers, Ay and Ayy, of the pd→→n{pp}s charge-exchange reaction have been measured at a beam energy of 600 MeV at the COSY-ANKE facility by using an unpolarised proton beam incident on an internal storage cell target filled with polarised deuterium gas. The low energy recoiling protons were measured in a pair of silicon tracking telescopes placed on either side of the target. Putting a cut of 3 MeV on the diproton excitation energy ensured that the two protons were dominantly in the S01 state, here denoted by {pp}s. The polarisation of the deuterium gas was established through measurements in parallel of proton–deuteron elastic scattering. By analysing events where both protons entered the same telescope, the charge-exchange reaction was measured for momentum transfers q≥160 MeV/c. These data provide a good continuation of the earlier results at q≤140 MeV/c obtained with a polarised deuteron beam. They are also consistent with impulse approximation predictions with little sign evident for any modifications due to multiple scatterings. These successful results confirm that the ANKE deuteron charge-exchange programme can be extended to much higher energies with a polarised deuterium target than can be achieved with a polarised deuteron beam. Keywords: Deuteron charge exchange, Polarisation effects

International audience; The vector and tensor analysing powers, AyAy and AyyAyy, of the View the MathML sourcepd→→n{pp}s charge-exchange reaction have been measured at a beam energy of 600 MeV at the COSY-ANKE facility by using an unpolarised proton beam incident on an internal storage cell target filled with polarised deuterium gas. The low energy recoiling protons were measured in a pair of silicon tracking telescopes placed on either side of the target. Putting a cut of 3 MeV on the diproton excitation energy ensured that the two protons were dominantly in the View the MathML sourceS01 state, here denoted by {pp}s{pp}s. The polarisation of the deuterium gas was established through measurements in parallel of proton–deuteron elastic scattering. By analysing events where both protons entered the same telescope, the charge-exchange reaction was measured for momentum transfers q≥160 MeV/cq≥160 MeV/c. These data provide a good continuation of the earlier results at q≤140 MeV/cq≤140 MeV/c obtained with a polarised deuteron beam. They are also consistent with impulse approximation predictions with little sign evident for any modifications due to multiple scatterings. These successful results confirm that the ANKE deuteron charge-exchange programme can be extended to much higher energies with a polarised deuterium target than can be achieved with a polarised deuteron beam.

The masses of the low-lying strange and charm baryons are evaluated using two degenerate flavors of twisted mass sea quarks for pion masses in the range of about 260 MeV to 450 MeV. The strange and charm valence quark masses are tuned to reproduce the mass of the kaon and D-meson at the physical point. The tree-level Symanzik improved gauge action is employed. We use three values of the lattice spacing, corresponding to $\beta=3.9$, $\beta=4.05$ and $\beta=4.2$ with $r_0/a=5.22(2)$, $r_0/a=6.61(3)$ and $r_0/a=8.31(5)$ respectively. %spacings $a=0.0855(5)$ and $a=0.0667(3)$ determined from the pion decay constant. We examine the dependence of the strange and charm baryons on the lattice spacing and strange and charm quark masses. The pion mass dependence is studied and physical results are obtained using heavy baryon chiral perturbation theory to extrapolate to the physical point., Comment: 19 pages, 18 Figures. Typos corrected, reference added, version to appear in Phys. Rev. D. arXiv admin note: text overlap with arXiv:0910.2419

We present results on the nucleon axial form factors within lattice QCD using two flavors of degenerate twisted mass fermions. Volume effects are examined using simulations at two volumes of spatial length $L=2.1$ fm and $L=2.8$ fm. Cut-off effects are investigated using three different values of the lattice spacings, namely $a=0.089$ fm, $a=0.070$ fm and $a=0.056$ fm. The nucleon axial charge is obtained in the continuum limit and chirally extrapolated to the physical pion mass enabling comparison with experiment., ETM Collaboration, 14 pages, 12 figures

We present results on the nucleon form factors and moments of generalized parton distributions obtained within the twisted mass formulation of lattice QCD. We include a discussion of lattice artifacts by examining results at different volumes and lattice spacings. We compare our results with those obtained using different discretization schemes and to experiment., 4 pages, 3 Figures, Invited talk presented at the 35th International Conference of High Energy Physics - ICHEP 2010 July 22-28, 2010, Paris, France

We present results on the nucleon electromagnetic form factors within lattice QCD using two flavors of degenerate twisted mass fermions. Volume effects are examined using simulations at two volumes of spatial length L=2.1 fm and L=2.8 fm. Cut-off effects are investigated using three different values of the lattice spacings, namely a=0.089 fm, a=0.070 and a=0.056 fm. The nucleon magnetic moment, Dirac and Pauli radii are obtained in the continuum limit and chirally extrapolated to the physical pion mass allowing for a comparison with experiment., Comment: ETM Collaboration, 14 pages, 15 Figures

We present results on the nucleon form factors using two degenerate flavors of twisted mass fermions on 243×48 and 32×64 lattices with pion masses in the range 290÷485MeV. © 2010 American Institute of Physics. 1261 141 146 Sponsors: Univ. Adelaide, Cent. Subatomic Struct. Matter Jefferson Lab Conference code: 82660

The masses of the low lying baryons are evaluated using two degenerate flavors of twisted mass sea quarks corresponding to pseudo scalar masses in the range of about 270-500 MeV. The strange valence quark mass is tuned to reproduce the mass of the kaon in the physical limit. The tree-level Symanzik improved gauge action is employed. We use lattices of spatial size 2.1 fm and 2.7 fm at two values of the lattice spacing with $r_0/a=5.22(2)$ and $r_0/a=6.61(3)$. We check for both finite volume and cut-off effects on the baryon masses. We performed a detailed study of the chiral extrapolation of the octet and decuplet masses using SU(2) $\chi$PT. The lattice spacings determined using the nucleon mass at the physical point are consistent with the values extracted using the pion decay constant. We examine the issue of isospin symmetry breaking for the octet and decuplet baryons and its dependence on the lattice spacing. We show that in the continuum limit isospin breaking is consistent with zero, as expected. The baryon masses that we find after taking the continuum limit and extrapolating to the physical limit are in good agreement with experiment., Comment: By the ETM Collaboration, 24 pages, 24 figures

The differential cross section and deuteron analysing powers of the dp -> {pp}n charge-exchange reaction have been measured with the ANKE spectrometer at the COSY storage ring. Using a deuteron beam of energy 1170 MeV, data were obtained for small momentum transfers to a {pp} system with low excitation energy. A good quantitative understanding of all the measured observables is provided by the impulse approximation using known neutron-proton amplitudes. The proof of principle achieved here for the method suggests that measurements at higher energies will provide useful information in regions where the existing np database is far less reliable., 11 pages with 5 figures

We present results on the mass of the nucleon and the Delta using two dynamical degenerate twisted mass quarks and the tree-level Symanzik improved gauge action. The evaluation is performed at four quark masses corresponding to a pion mass in the range of about 300-600 MeV on lattices of 2.1-2.7 fm. We check for cut-off effects by evaluating these baryon masses on lattices of spatial size 2.1 fm at beta=3.9 and beta=4.05 and on a lattice of 2.4 fm at beta=3.8. The values we find are compatible within our statistical errors. Lattice results are extrapolated to the physical limit using continuum chiral perturbation theory. Performing a combined fit to our lattice data at beta=3.9 and beta=4.05 we find a nucleon mass of 964\pm 28 (stat.) \pm 8 (syst.) MeV. The nucleon mass at the physical point provides an independent determination of the lattice spacing. Using heavy baryon chiral perturbation theory at O(p^3) we find a_{\beta=3.9}=0.0890\pm 0.0039(stat.) \pm 0.0014(syst.) fm, and a_{\beta=4.05}= 0.0691\pm 0.0034(stat.) \pm 0.0010(syst.) fm, in good agreement with the values determined from the pion decay constant. Isospin violating lattice artifacts in the Delta-system are found to be compatible with zero for the values of the lattice spacings used in this work. Performing a combined fit to our lattice data at beta=3.9 and beta=4.05 we find for the masses of the Delta^{++,-} and Delta^{+,0} 1316 \pm 60 (stat.) MeV and 1330 \pm 74 (stat.) MeV respectively. We confirm that in the continuum limit they are also degenerate., Comment: 19 pages, 18 figures, Version as accepted in Phys. Rev. D, Discussion on nucleon sigma-term extended, typos corrected

The Lattice 2008 proceedings will be published in the online journal, “Proceedings of Science” (PoS) organized by SISSA; International audience; We present results on the nucleon axial charge and the lowest moment hxi of the quark distribution using two degenerate flavors of light dynamical twisted mass fermions. The calculation is performed for pion masses in the range of 500 MeV to 300 MeV on a lattice of spatial size of about 2.1 fm.

OECD Publishing ISBN 9789264028579; In this contribution current advances and challenge in low energy few-nucleon scattering problem are discussed. Some original results obtained when solving Faddeev-Yakubovski equations in configuration space are presented both for three and four-nucleon systems.

By comparing respectively the interaction between 3He atoms and the neutron-neutron one, we examine the possibility for both fermionic systems to form small clusters., Comment: Contributed talk to 17th International IUPAP Conference on Few-Body Problems in Physics, Durham, North Carolina, 5-10 June 2003. Published in the proceedings (Elsevier, 2004) pp. S106-S108

The light-front dynamics is an efficient approach to study of field theory and of relativistic composite systems (nuclei at relativistic relative nucleon momenta, hadrons in the quark models). The explicitly covariant version of this approach is briefly reviewed and illustrated by some applications., Comment: 16 pages, 8 figures. Talk at the 21-st International Workshop on Nuclear Theory, Rila Mountains, Bulgaria, June 10-15, 2002

Virtual bremsstrahlung yields measured in (p) over bar+p-->p+p+e(+)+e(-) and (p) over bar+d-->He-3+e(+)+e(-) are presented. The experiments were performed with a 190 MeV polarized proton beam obtained from the cyclotron AGOR at KVI in Groningen. Differential cross sections, response functions and analyzing powers were obtained for both reactions in exclusive measurements in which all outgoing particles were measured in a coincidence setup between SALAD and TAPS. The data are compared with gauge-invariant calculations using a NN T-matrix fitted to elastic phase-shifts. For pp-->ppe(+) e(-) a reasonable agreement is found for all measured virtual-photon invariant masses, M-gamma > 15 MeV/c(2) up to 80 MeV/c(2). For the pd-->He-3 e(+)e(-) angular distributions, the calculations underestimate the data for theta(CM) >100 degrees similar to what is found in the real-photon capture reaction.

A series of bremsstrahlung measurements have been performed at KVI with the 190 MeV polarized proton beam of the new superconducting cyclotron, AGOR. The aim of these measurements is to investigate the dynamics of interactions involving intermediate off-shell nucleons. Nucleon-nucleon bremsstrahlung is the most fundamental process used for such studies as it involves the strong interaction between two nucleons and the well-known electromagnetic interaction. The present experiment provides the most accurate experiment to date on the proton-proton system. The accuracy is high enough to investigate higher order effects such as the virtual Delta-isobar and meson exchange currents. Surprisingly, none of the microscopic calculations is able to describe the data both in magnitude and in shape.

A beam-polarimeter for medium energy protons and deuterons (E=100-200 MeV) has been constructed. Its operation is based on the p + d, p + p and d + p elastic scattering with coincident detection of both particles in 4 independent planes. The 16 detectors of the polarimeter have a phoswich construction to ensure particle identification. With this device the analyzing power, A(y), of p + p elastic scattering has been measured at 190 MeV for CM-angles of 25 degrees to 115 degrees in two planes, monitored by p Sp elastic scattering in the two other planes. The target was mixed CH2/CD2. This allowed for simultaneous extraction of A(y)(p, d) and the beam polarizations. The analyzing power is compared with calculations based on the Bonn-potential including partial waves up to J = 5.

The vector and tensor analysing powers, AyAy and AyyAyy, of the View the MathML sourcepd→→n{pp}s charge-exchange reaction have been measured at a beam energy of 600 MeV at the COSY-ANKE facility by using an unpolarised proton beam incident on an internal storage cell target filled with polarised deuterium gas. The low energy recoiling protons were measured in a pair of silicon tracking telescopes placed on either side of the target. Putting a cut of 3 MeV on the diproton excitation energy ensured that the two protons were dominantly in the View the MathML sourceS01 state, here denoted by {pp}s{pp}s. The polarisation of the deuterium gas was established through measurements in parallel of proton–deuteron elastic scattering. By analysing events where both protons entered the same telescope, the charge-exchange reaction was measured for momentum transfers q≥160 MeV/cq≥160 MeV/c. These data provide a good continuation of the earlier results at q≤140 MeV/cq≤140 MeV/c obtained with a polarised deuteron beam. They are also consistent with impulse approximation predictions with little sign evident for any modifications due to multiple scatterings. These successful results confirm that the ANKE deuteron charge-exchange programme can be extended to much higher energies with a polarised deuterium target than can be achieved with a polarised deuteron beam.

International audience; The understanding of nuclear systems as composed of interacting nucleons has been considerably sharpened by the effective field theory (EFT) framework. The latter provides a link between the nuclear interaction and the underlying quantum chromodynamics, as the relevant degrees of freedom result, at least ideally, from a decimation process starting from fundamental quarks and gluons. Owing to chiral symmetry and the Goldstone bosons’ characters of the interchanged pions among nucleons, the properties of heavier nuclei can in principle be traced back to a restricted set of low-energy constants (LECs) to be determined in lighter systems in the framework of a systematic low-energy expansion. At smaller energy scales, in pionless EFT, the interactions simplify becoming of contact type. The low-energy expansion is organized differently, relying on the emergence of universal properties, characteristic of systems with large two-body scattering lengths. We will examine the two above schemes and discuss their relation, with the aim of devising viable power counting schemes for applications in nuclear physics.