The photon beam asymmetry of the C-12((gamma) over right arrow, p(01))(11) B and C-12((gamma) over right arrow, p(2-6))(11) B reactions has been measured in the energy range 40-65 MeV, using a tagged, linearly-polarized photon beam at the MAX-lab facility in Sweden. The asymmetry of the C-12((gamma) over right arrow, p(01))(11) B reaction to ground and first excited state of (11) B is Sigma approximate to 0.82 over the measured energy range. The main contribution to the C-12((gamma) over right arrow, p(2-6))(11) B reaction to higher excited states comes from processes in which the residual nucleus is in the 3/2(-)(5.02MeV) or 7/2(-)(6.74MeV) excited states. The asymmetry of this reaction is Sigma approximate to 0.6, close to the value for free deuteron photodisintegration.

The photon beam asymmetry of the C12(γ→,p01)11B and C12(γ→,p2−6)11B reactions has been measured in the energy range 40–65 MeV, using a tagged, linearly-polarized photon beam at the MAX-lab facility in Sweden. The asymmetry of the C12(γ→,p01)11B reaction to ground and first excited state of B11 is Σ≈0.82 over the measured energy range. The main contribution to the C12(γ→,p2−6)11B reaction to higher excited states comes from processes in which the residual nucleus is in the 3/2−(5.02 MeV) or 7/2−(6.74 MeV) excited states. The asymmetry of this reaction is Σ≈0.6, close to the value for free deuteron photodisintegration.

The photon beam asymmetry of the C12(γ→,p01)11B and C12(γ→,p2−6)11B reactions has been measured in the energy range 40–65 MeV, using a tagged, linearly-polarized photon beam at the MAX-lab facility in Sweden. The asymmetry of the C12(γ→,p01)11B reaction to ground and first excited state of B11 is Σ≈0.82 over the measured energy range. The main contribution to the C12(γ→,p2−6)11B reaction to higher excited states comes from processes in which the residual nucleus is in the 3/2−(5.02MeV) or 7/2−(6.74MeV) excited states. The asymmetry of this reaction is Σ≈0.6, close to the value for free deuteron photodisintegration.

The asymmetry of the cross section of the 12C(γ,p0)11B and 12C(γ,p1)11B reactions has been measured in the energy range 40...55MeV using linearly polarized tagged photons of the MAX-lab facility. The asymmetry of the process 12C(⃗γ,p0)11B is Σ ≈ 0.85, that implies one-particle reaction mechanism. The asymmetry of the reaction 12C(⃗γ,p1)11B is smaller, Σ ≈ 0.6...0.7, that may be due to the stronger relative contribution of the 2h−1p mechanism to the dominant one-particle reaction mechanism.

The electromagnetic polarizabilities of the nucleon are fundamental nucleon-structure observables that characterize its response to external electromagnetic fields. The neutron polarizabilities can be accessed from Compton-scattering data on light nuclear targets. Recent measurements of the differential cross section for Compton scattering on the deuteron below the pion-production threshold have decreased the uncertainties in the neutron polarizabilities, yet the proton polarizabilities remain known substantially more accurately. As the sensitivity of the cross section to the polarizabilities increases with incident photon energy, measurements above the pion threshold may offer a way for an improved determination of the neutron polarizabilities. In this article, the first measurement of the cross section for Compton scattering on the deuteron above the pion-production threshold is presented.

On the base of reaction of deuteron photo-disintegration it was studied possibility of the simultaneous measuring of cross sections and asymmetry of the (gamma,p) reactions at the using of the coherent polarized photon beam. Measurements were performed for the proton emission angle 90 degrees. The cross sections well agree with the literary data, obtained on the bremsstrahlung photon beam in the range of energies 45...80 MeV.

The gamma-radiation by electrons with the energy of similar to 200 MeV in a 100 mu m-thick diamond crystal has been measured at the MAX-lab experimental facility, when the electrons are incident on the crystal along the (100) axis. In this case, the intensity of the -radiation with the energy similar to l-2 MeV is approximately 16 times higher than that in amorphous matter of the same thickness. Theoretical calculations based on the quasi-classical QED approximation are in good agreement with the experimental data. The analysis of the radiation mechanisms has shown that the main contribution to the radiation intensity resulted from electrons, moving in the above-barrier regime and at small angles to the crystal axis.

The cross section asymmetry of C-12(gamma, P-01)B-11 and C-12(gamma, p(2-6))B-11 reactions has been studied at the energy range 40-55 MeV, using linearly polarized tagged photons of the MAX-lab facility. The asymmetry of the C-12(gamma, p(01))B-11 processes, which assume the one-body mechanism of the reaction, is Sigma approximate to 0.82 +/- 0.05 for photon energies 45-50 MeV. The asymmetry for the C-12(gamma, p(2-6))B-11 reactions, which produce a maximum at excitation energy similar to 6 MeV, is Sigma approximate to 0.53 +/- 0.13 for a photon energy 49 MeV. It is close to the asymmetry of reaction of the free deuteron photodisintegration, and can be resulted from the two-body mechanism of the photon absorption. (C) 2016 Elsevier B.V. All rights reserved.

Information on the triggered strips of silicon strip detectors of a MAX-lab Delta E-E CsI/SSD-telescope was used to determination the angular range of emitted reaction particles. It allowed an improvement in the energy resolution of the telescope by decreasing the kinematical broadening of the missing energy spectra of C-12(gamma,p)B-11 reaction, and enabling more accurate separation of exited states of residual nucleus.

Baryon-to-meson Transition Distribution Amplitudes (TDAs) encoding valuable new information on hadron structure appear as building blocks in the collinear factorized description for several types of hard exclusive reactions. In this paper, we address the possibility of accessing nucleon-to-pion (πN) TDAs from \(\bar pp \to e^ + e^ - \pi ^0 \) reaction with the future P̄ANDA detector at the FAIR facility. At high center-of-mass energy and high invariant mass squared of the lepton pair q 2, the amplitude of the signal channel \(\bar pp \to e^ + e^ - \pi ^0 \) admits a QCD factorized description in terms of πN TDAs and nucleon Distribution Amplitudes (DAs) in the forward and backward kinematic regimes. Assuming the validity of this factorized description, we perform feasibility studies for measuring \(\bar pp \to e^ + e^ - \pi ^0 \) with the P̄ANDA detector. Detailed simulations on signal reconstruction efficiency as well as on rejection of the most severe background channel, i.e. \(\bar pp \to \pi ^ + \pi ^ - \pi ^0 \) were performed for the center-of-mass energy squared s = 5 GeV2 and s = 10 GeV2, in the kinematic regions 3.0 < q 2 < 4.3 GeV2 and 5 < q 2 GeV2, respectively, with a neutral pion scattered in the forward or backward cone \(\left| {\cos \theta _{\pi ^0 } } \right| > 0.5\) in the proton-antiproton center-of-mass frame. Results of the simulation show that the particle identification capabilities of the P̄ANDA detector will allow to achieve a background rejection factor of 5 · 107 (1 · 107) at low (high) q 2 for s = 5 GeV2, and of 1 · 108 (6 · 106) at low (high) q 2 for s = 10 GeV2, while keeping the signal reconstruction efficiency at around 40%. At both energies, a clean lepton signal can be reconstructed with the expected statistics corresponding to 2 fb−1 of integrated luminosity. The cross sections obtained from the simulations are used to show that a test of QCD collinear factorization can be done at the lowest order by measuring scaling laws and angular distributions. The future measurement of the signal channel cross section with P̄ANDA will provide a new test of the perturbative QCD description of a novel class of hard exclusive reactions and will open the possibility of experimentally accessing π TDAs.

Differential cross sections for elastic scattering of photons from the deuteron have recently been measured at the Tagged-Photon Facility at the MAX IV Laboratory in Lund, Sweden. These first new measurements in more than a decade further constrain the isoscalar electromagnetic polarizabilities of the nucleon and provide the first-ever results above 100 MeV, where the sensitivity to the polarizabilities is increased. We add 23 points between 70 and 112 MeV, at angles 60 degrees, 120 degrees, and 150 degrees. Analysis of these data using a chiral effective field theory indicates that the cross sections are both self-consistent and consistent with previous measurements. Extracted values of alpha(s) = [12.1 +/- 0.8(stat) +/- 0.2(BSR) +/- 0.8(th)] x 10(-4) fm(3) and beta(s) = [2.4 +/- 0.8(stat) +/- 0.2(BSR) +/- 0.8(th)] x 10(-4) fm(3) are obtained from a fit to these 23 new data points. This paper presents in detail the experimental conditions and the data analysis used to extract the cross sections.

The paper considers the results of experiments on the reactions C-12(gamma, p)B-11 and d(gamma, p)n in the energy range of tagged photons 35...80 MeV. Demonstrated the possibility identification of protons by Delta E - E using CsI/SSD telescope. Using the spectra of the missing energy defined the values of differential cross sections of these reactions in the range of photon energies. The good agreement of the experimental results with the available data in the literature.

In this work properties of a vacuum phototriode (VPT) and preamplifier unit designed for the electromagnetic calorimeter of the PANDA experiment being built at FAIR are investigated. With the use of lead tungstate and lanthanium bromide scintillators the VPT properties are studied at low photon energies, from tens of keV in the lanthanium bromide measurements and between 10MeV and 60MeV in the lead tungstate measurements. At these energies the noise of the VPT unit can be expected to influence its performance significantly. It is shown that the noise contribution to the measured energy resolution, under optimal conditions, is consistent with a fluctuation of (one standard deviation) approximately 200 electrons at the VPT anode. For a lead tungstate crystal this is equivalent to a noise of 1.2MeV. For lanthanium bromide this makes it possible to use VPTs for gamma ray spectroscopy above a few hundreds of keV without noticeable effects on the energy resolution compared to measurements with a standard photomultiplier.

A linearly polarized photon beam has been produced at MAX-lab using the coherent bremsstrahlung of electrons with an energy of 192.6MeV in a 0.1mm thick diamond crystal. The intensity and shape of the coherent maxima and their dependence on the crystal orientation are similar to the features observed at higher electron energies (~ 1GeV) and are well described by coherent bremsstrahlung theory. The linear polarization of the uncollimated beam at the coherent peak energy ≈50–60MeV is about 20% and can be increased to 40–45% if collimation of half the characteristic angle is used. At present the degree of polarization is high enough to allow the study of polarization observables in photo-nuclear reactions at MAX-lab in the energy range from Giant Dipole Resonance up to ≈80MeV.

This document describes the technical layout and the expected performance of the Straw Tube Tracker (STT), the main tracking detector of the PANDA target spectrometer. The STT encloses a Micro-Vertex-Detector (MVD) for the inner tracking and is followed in beam direction by a set of GEM stations. The tasks of the STT are the measurement of the particle momentum from the reconstructed trajectory and the measurement of the specific energy loss for a particle identification. Dedicated simulations with full analysis studies of certain proton-antiproton reactions, identified as being benchmark tests for the whole PANDA scientific program, have been performed to test the STT layout and performance. The results are presented, and the time lines to construct the STT are described.

This document describes the technical layout and the expected performance of the Straw Tube Tracker (STT), the main tracking detector of the \(\overline{P}\)ANDA target spectrometer. The STT encloses a Micro-Vertex-Detector (MVD) for the inner tracking and is followed in beam direction by a set of GEM stations. The tasks of the STT are the measurement of the particle momentum from the reconstructed trajectory and the measurement of the specific energy loss for a particle identification. Dedicated simulations with full analysis studies of certain proton-antiproton reactions, identified as being benchmark tests for the whole \(\overline{P}\)ANDA scientific program, have been performed to test the STT layout and performance. The results are presented, and the time lines to construct the STT are described.

Rate-dependent effects in the electronics used to instrument the tagger focal plane at the MAX IV Laboratory have been investigated using the novel approach of Monte Carlo simulation. Results are compared to analytical calculations as well as experimental data for both specialized testing and production running to demonstrate a thorough understanding of the behavior of the detector system.

The response of a matrix of 25 lead tungstate (PWO) scintillator detectors, operated at −25°C, to photons in the range 13MeV–64MeV has been measured at the tagged-photon facility at MAX-lab, Lund. The tapered PWO crystals, each with a length of 200mm and a cross-section of 24.4×24.4mm2 in the front end, read out by 19mm photomultiplier tubes, were arranged in a 5×5 matrix. The response was measured for photons directed towards the centre of the central crystal as well as for photons directed towards the corner of the central crystal, where four crystals meet. The obtained energy resolution surpasses what has been published so far and is close to the limit given by Poisson statistics and escaped energy. For photons directed towards the centre(corner) of the central crystal the relative energy resolution, defined as (FWHM/2.35)/Eγ, decreases from 7.3%(11.0%) at Eγ=13MeV to 3.3%(3.6%) at Eγ=64MeV. The reconstructed point of impact of a photon in this energy range is determined with an uncertainty (one standard deviation) of 7.3±0.1mm.

A low-pressure, position-sensitive, multi-wire proportional chamber (LPMWPC) system with an active area 12×12 cm 2 for the detection of heavy nuclear fragments, has been developed for use in tagged photon beam experiments. The LPMWPC system can be operated in single as well as double step operational modes. In the case of double step operational mode with a high gas amplification factor, signals from α-particles reside well above the electronic noise. Typical energy loss spectra of alpha particles and fission fragments (FF) obtained from a 252 Cf source are shown and discussed. The pulse height distributions of α-particles have a Landau distribution shape, while the pulse height distribution of FFs differs from Gaussian shape. It has long tails at both low-and high-energy sides. The average pulse height ratio of alpha particles and FF's is close to the theoretical value and amounts to about 1/80. (Less)