Discovery of a new Galactic bona fide luminous blue variable with Spitzer

We report the discovery of a circular mid-infrared shell around the emission-line star Wray 16- 137 using archival data of the Spitzer Space Telescope. Follow-up optical spectroscopy of Wray 16-137 with the Southern African Large Telescope revealed a rich emission spectrum typical of the classical luminous blue variables (LBVs) like P Cygni. Subsequent spectroscopic and photometric observations showed drastic changes in the spectrum and brightness during the last three years, meaning that Wray 16-137 currently undergoes an S Dor-like outburst. Namely, we found that the star has brightened by ≈1 mag in the V and Ic bands, while its spectrum became dominated by Fe II lines. Taken together, our observations unambiguously show that Wray 16-137 is a new member of the family of Galactic bona fide LBVs

O-C diagrams for 33 RR Lyrae-type stars

In this paper we study period variations of 33 RR Lyrae type stars using O-C analysis, and calculate their mean light elements

Short time scale period variations of the RRc star V468 Hya

We find large period changes of the first-overtone RR Lyrae type star V468 Hya

Track reconstruction and matching between emulsion and silicon pixel detectors for the SHiP-charm experiment

In July 2018 an optimization run for the proposed charm cross section measurement for SHiP was performed at the CERN SPS. A heavy, moving target instrumented with nuclear emulsion films followed by a silicon pixel tracker was installed in front of the Goliath magnet at the H4 proton beam-line. Behind the magnet, scintillating-fibre, drift-tube and RPC detectors were placed. The purpose of this run was to validate the measurement's feasibility, to develop the required analysis tools and fine-tune the detector layout. In this paper, we present the track reconstruction in the pixel tracker and the track matching with the moving emulsion detector. The pixel detector performed as expected and it is shown that, after proper alignment, a vertex matching rate of 87% is achieved.Peer Reviewe

Measurement of the muon flux from 400 GeV/c protons interacting in a thick molybdenum/tungsten target

The SHiP experiment is proposed to search for very weakly interacting particles beyond the Standard Model which are produced in a 400 GeV/c proton beam dump at the CERN SPS. About 1011 muons per spill will be produced in the dump. To design the experiment such that the muon-induced background is minimized, a precise knowledge of the muon spectrum is required. To validate the muon flux generated by our Pythia and GEANT4 based Monte Carlo simulation (FairShip), we have measured the muon flux emanating from a SHiP-like target at the SPS. This target, consisting of 13 interaction lengths of slabs of molybdenum and tungsten, followed by a 2.4 m iron hadron absorber was placed in the H4 400 GeV/c proton beam line. To identify muons and to measure the momentum spectrum, a spectrometer instrumented with drift tubes and a muon tagger were used. During a 3-week period a dataset for analysis corresponding to (3.27±0.07) × 1011 protons on target was recorded. This amounts to approximatively 1% of a SHiP spill

Track reconstruction and matching between emulsion and silicon pixel detectors for the SHiP-charm experiment

In July 2018 an optimization run for the proposed charm cross section measurement for SHiP was performed at the CERN SPS. A heavy, moving target instrumented with nuclear emulsion films followed by a silicon pixel tracker was installed in front of the Goliath magnet at the H4 proton beam-line. Behind the magnet, scintillating-fibre, drift-tube and RPC detectors were placed. The purpose of this run was to validate the measurement's feasibility, to develop the required analysis tools and fine-tune the detector layout. In this paper, we present the track reconstruction in the pixel tracker and the track matching with the moving emulsion detector. The pixel detector performed as expected and it is shown that, after proper alignment, a vertex matching rate of 87% is achieved

Measurement of the beam asymmetry Σ for π0 and η photoproduction on the proton at Eγ=9 GeV

We report measurements of the photon beam asymmetry Σ for the reactions γ - p→pπ0 and γ - p→pη from the GlueX experiment using a 9 GeV linearly polarized, tagged photon beam incident on a liquid hydrogen target in Jefferson Lab's Hall D. The asymmetries, measured as a function of the proton momentum transfer, possess greater precision than previous π0 measurements and are the first η measurements in this energy regime. The results are compared with theoretical predictions based on t-channel, quasiparticle exchange and constrain the axial-vector component of the neutral meson production mechanism in these models. © 2017 American Physical Society

Beam asymmetry ς for the photoproduction of η and η′ mesons at Eγ=8.8 GeV

We report on the measurement of the beam asymmetry ς for the reactions γ - p→pη and γ - p→pη′ from the GlueX experiment using an 8.2-8.8-GeV linearly polarized tagged photon beam incident on a liquid hydrogen target in Hall D at Jefferson Laboratory. These measurements are made as a function of momentum transfer -t with significantly higher statistical precision than our earlier η measurements and are the first measurements of η′ in this energy range. We compare the results to theoretical predictions based on t-channel quasiparticle exchange. We also compare the ratio of ςη to ςη′ to these models as this ratio is predicted to be sensitive to the amount of ss exchange in the production. We find that photoproduction of both η and η′ is dominated by natural parity exchange with little dependence on -t. © 2019 American Physical Society

Measurement of the muon flux from 400 GeV/c protons interacting in a thick molybdenum/tungsten target

The SHiP experiment is proposed to search for very weakly interacting particles beyond the Standard Model which are produced in a 400 GeV/c proton beam dump at the CERN SPS. About 1011muons per spill will be produced in the dump. To design the experiment such that the muon-induced background is minimized, a precise knowledge of the muon spectrum is required. To validate the muon flux generated by our Pythia and GEANT4 based Monte Carlo simulation (FairShip), we have measured the muon flux emanating from a SHiP-like target at the SPS. This target, consisting of 13 interaction lengths of slabs of molybdenum and tungsten, followed by a 2.4 m iron hadron absorber was placed in the H4 400 GeV/c proton beam line. To identify muons and to measure the momentum spectrum, a spectrometer instrumented with drift tubes and a muon tagger were used. During a 3-week period a dataset for analysis corresponding to (3.27 +/- 0.07)x1011protons on target was recorded. This amounts to approximatively 1% of a SHiP spill

Measurement of the muon flux for the SHiP experiment

The SHiP experiment will search for very weakly interacting particles beyond the Standard Model which are produced in a 400 \GeV/$c$ proton beam dump at the CERN SPS. About $10^{11}$ muons per spill will be produced in the dump. To design the experiment such that the muon-induced background is minimized, a precise knowledge of the muon spectrum is required. To validate the muon flux generated by our Pythia and GEANT4 based Monte Carlo simulation (FairShip), we have measured the muon flux emanating from a SHiP-like target at the SPS. This target, consisting of 13 interaction lengths of slabs of molybdenum and tungsten, followed by a 2.4 m iron hadron absorber was placed in the H4 400~\GeV/$c$ proton beam line. To identify muons and to measure the momentum spectrum, a spectrometer instrumented with drift tubes and a muon tagger were used. During a three-week period a dataset for analysis corresponding to $(3.27\pm0.07)~\times~10^{11}$ protons on target was recorded. This amounts to approximatively 1\% of a SHiP spill