This document complements and completes what was submitted last year to PAC45 as an update to the proposal PR12-16-001 "Dark matter search in a Beam-Dump eXperiment (BDX)" at Jefferson Lab submitted ...to JLab-PAC44 in 2016. Following the suggestions contained in the PAC45 report, in coordination with the lab, we ran a test to assess the beam-related backgrounds and validate the simulation framework used to design the BDX experiment. Using a common Monte Carlo framework for the test and the proposed experiment, we optimized the selection cuts to maximize the reach considering simultaneously the signal, cosmic-ray background (assessed in Catania test with BDX-Proto) and beam-related backgrounds (irreducible NC and CC neutrino interactions as determined by simulation). Our results confirmed what was presented in the original proposal: with 285 days of a parasitic run at 65 \(\mu\)A (corresponding to \(10^{22}\) EOT) the BDX experiment will lower the exclusion limits in the case of no signal by one to two orders of magnitude in the parameter space of dark-matter coupling versus mass.
Physical Review C 91, 042201(R) (2015) First measurement of the beam asymmetry $\Sigma$ for Compton scattering off
the proton in the energy range $E_{\gamma}=0.85 - 1.25$ GeV is presented. The
data ...reveals two narrow structures at $E_{\gamma}= 1.036$ and
$E_{\gamma}=1.119$ GeV. They may signal narrow resonances with masses near
$1.68$ and $1.72$ GeV, or they may be generated by the sub-threshold $K\Lambda$
and $\omega p$ production. Their decisive identification requires additional
theoretical and experimental efforts.
This document is an update to the proposal PR12-16-001 Dark matter search in a Beam-Dump eXperiment (BDX) at Jefferson Lab submitted to JLab-PAC44 in 2016 reporting progress in addressing questions ...raised regarding the beam-on backgrounds. The concerns are addressed by adopting a new simulation tool, FLUKA, and planning measurements of muon fluxes from the dump with its existing shielding around the dump. First, we have implemented the detailed BDX experimental geometry into a FLUKA simulation, in consultation with experts from the JLab Radiation Control Group. The FLUKA simulation has been compared directly to our GEANT4 simulations and shown to agree in regions of validity. The FLUKA interaction package, with a tuned set of biasing weights, is naturally able to generate reliable particle distributions with very small probabilities and therefore predict rates at the detector location beyond the planned shielding around the beam dump. Second, we have developed a plan to conduct measurements of the muon ux from the Hall-A dump in its current configuration to validate our simulations.
Observation of a narrow structure at \(W\sim 1.68\) GeV in the excitation functions of some photon- and pion-induced reactions may signal a new narrow isospin-1/2 \(N(1685)\) resonance. New data on ...the \(\gamma N \to \pi \eta N\) reactions from GRAAL seems to reveal the signals of both \(N^+(1685)\) and \(N^0(1685)\) resonances.
In the years an increase of last biliary injuries during laparoscopic cholecystectomy was observed. At present this occurrence rate is 0.1-3.4% of laparoscopic procedures. Probably this is to be ...related to less contraindications to cholecystectomy by laparoscopic procedures, with increase of more difficult operations. The intraoperative biliary injuries are due to anatomical anomalies of the local structures, mistakes of technique, flogosis of the cholecisto-choledocal region. Factors preventing iatrogenic injuries are accurate and standardized operative technique, adoption of modern instruments, intraoperative cholangiography. The Authors have reviewed their experience based on 1236 laparoscopic cholecysectomies performed in six years (1992-1998) in their own structure. Four lesions of the biliary tract (0.3%) have occurred: three Bismuth I-II and one Bismuth IV. They have always performed intraoperative cholangiography, without false negative, in contrast with present literature. They conclude underlining the need of the routine contrastrographic study of the biliary tract in all cholecysectomies as well as of an adequate training in radiological imagines interpretation.
Different interpretations of narrow structures at \(W\sim 1.68\) and \(W\sim 1.72\) GeV observed in several reactions are discussed. It is questionable whether interference phenomena could explain ...the whole complex of experimental findings. More probable hypotheses would be the existence of one or two narrow resonances \(N(1685)\) and \(N(1726)\) and/or the sub-threshold virtual \(K\Sigma\) and \(\omega p\) production (cusps).
MeV-GeV dark matter (DM) is theoretically well motivated but remarkably unexplored. This proposal presents the MeV-GeV DM discovery potential for a \(\sim\)1 m\(^3\) segmented CsI(Tl) scintillator ...detector placed downstream of the Hall A beam-dump at Jefferson Lab, receiving up to 10\(^{22}\) electrons-on-target (EOT) in 285 days. This experiment (Beam-Dump eXperiment or BDX) would be sensitive to elastic DM-electron and to inelastic DM scattering at the level of 10 counts per year, reaching the limit of the neutrino irreducible background. The distinct signature of a DM interaction will be an electromagnetic shower of few hundreds of MeV, together with a reduced activity in the surrounding active veto counters. A detailed description of the DM particle \(\chi\) production in the dump and subsequent interaction in the detector has been performed by means of Monte Carlo simulations. Different approaches have been used to evaluate the expected backgrounds: the cosmogenic background has been extrapolated from the results obtained with a prototype detector running at INFN-LNS (Italy), while the beam-related background has been evaluated by GEANT4 Monte Carlo simulations. The proposed experiment will be sensitive to large regions of DM parameter space, exceeding the discovery potential of existing and planned experiments in the MeV-GeV DM mass range by up to two orders of magnitude.
Eur. Phys. J. A (2015) 51: 77 The $\Sigma$ beam asymmetry in $\eta^{\prime}$ photoproduction off the proton
was measured at the GrAAL polarised photon beam with incoming photon energies
of 1.461 and ...1.480 GeV. For both energies the asymmetry as a function of the
meson production angle shows a clear structure, more pronounced at the lowest
one, with a change of sign around 90$^o$. The observed behaviour is compatible
with P-wave D-wave (or S-wave F-wave) interference, the closer to threshold the
stronger. The results are compared to the existing state-of-the-art
calculations that fail to account for the data.
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