Fri·Jul 5, 2019Friday·July 5, 2019

1. 01*

   Precision Beta Decay as a Probe of New Physics

   Vincenzo Cirgiliano🇺🇸 · Alejandro Garcia🇺🇸 · Doron Gazit🇮🇱 · Oscar Naviliat-Cuncic🇺🇸 · Guy Savard🇺🇸 · Albert Young🇺🇸

   The document presents a summary of discussions at recent workshops at the Amherst Center for Fundamental Interactions at Amherst, MA, and at the European Centre for Theoretical Studies in Nuclear Physics and Related Areas at Trento, Italy, on the potential sensitivity of precision beta-decay experiments towards new physics.

   nucl-ex48 citations
2. 02*

   Excited Nucleon Spectrum and Structure Studies with CLAS and CLAS12

   Daniel S. Carman🇺🇸

   The study of the spectrum and structure of excited nucleon states employing the electroproduction of exclusive reactions is an important avenue for exploring the nature of the non-perturbative strong interaction. The CLAS detector in Hall~B has provided the dominant part of the available world data on most relevant meson electroproduction channels off the nucleon in the resonance region for $Q^2$ up to 5~GeV${}^2$. Analyses of CLAS data for the exclusive channels $\pi N$, $\eta N$, and ${\pi }^{+}{\pi }^{-}p$ on a proton target have provided the only results available on the $Q^2$ evolution of the electro-excitation amplitudes for the transitions from the initial photon-proton to the final $N^{\ast }$ states in the mass range up to $W$=1.8~GeV. These electrocouplings allow for exploration of the internal structure of the produced excited nucleon states. This work has made it clear that consistent results from independent analyses of several exclusive channels with different resonance hadronic decay parameters and non-resonant backgrounds but the same $N^{\ast }$ electro-excitation amplitudes, is essential to have confidence in the extracted results. Starting in early 2018, a program to study the spectrum and structure of $N^{\ast }$ states in various exclusive electroproduction channels using the new CLAS12 spectrometer commenced. These studies will probe the structure of $N^{\ast }$ states in the mass range up to $W$=3~GeV and for $Q^2$ as low as 0.05~GeV${}^2$ and as high as 10-12~GeV${}^2$, thus providing a means to access $N^{\ast }$ structure information spanning a broad range of distance scales. Quasi-real photoproduction studies are also planned to search for additional $N^{\ast }$ states, the so-called hybrid baryons, for which the glue serves as an active structural component. In this talk the $N^{\ast }$ programs from both CLAS and CLAS12 will be reviewed.

   nucl-exAIP Conf.Proc.(2020)·7 citations
3. 03*

   A study in using MICROMEGAS to improve particle identification with the TAMU-MDM focal plane detector

   Alexandra Spiridon · Emmanuel Pollacco · Antti Saastamoinen · Robert E. Tribble · George Pascovici · Livius Trache · Bertrand Mehl · Rui de Oliveira

   A MICROMEGAS detection amplifier has been incorporated into the design of the TAMU MDM focal plane detector with the purpose of improving the energy resolution and thus, the particle identification. Beam tests showed a factor of 2 improvement over the original design, from 10-12% to 4-6%, for ions with A<40 at E/A around 10-20 MeV.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2019)·5 citations
4. 04*

   The high voltage system with pressure and temperature corrections for the novel MPGD-based photon detectors of COMPASS RICH-1

   J. Agarwala🇮🇹 · M. Bari🇮🇹 · F. Bradamante🇮🇹 · A. Bressan🇮🇹 · C. Chatterjee🇮🇹 · A. Cicuttin🇮🇹 · P. Ciliberti🇮🇹 · M. Crespo🇮🇹 · S. Dalla Torre🇮🇹 · S. Dasgupta🇮🇹 · B. Gobbo🇮🇹 · M. Gregori🇮🇹 and 8 other authors

   The novel MPGD-based photon detectors of COMPASS RICH-1 consist of large-size hybrid MPGDs with multi-layer architecture including two layers of Thick-GEMs and a bulk resistive MicroMegas. The top surface of the first THGEM is coated with a CsI film which also acts as photo-cathode. These detectors have been successfully in operation at COMPASS since 2016. Concerning bias-voltage supply, the Thick-GEMs are segmented in order to reduce the energy released in case of occasional discharges, while the MicroMegas anode is segmented into pads individually biased with positive voltage while the micromesh is grounded. In total, there are about ten different electrode types and more than 20000 electrodes supplied by more than 100 HV channels, where appropriate correlations among the applied voltages are required for the correct operation of the detectors. Therefore, a robust control system is mandatory, implemented by a custom designed software package, while commercial power supply units are used. This sophisticated control system allows to protect the detectors against errors by the operator, to monitor and log voltages and currents at 1 Hz rate, and automatically react to detector misbehaviour. In addition, a voltage compensation system has been developed to automatically adjust the biasing voltage according to environmental pressure and temperature variations, to achieve constant gain over time. This development answers to a more general need. In fact, voltage compensation is always a requirement for the stability of gaseous detectors and its need is enhanced in multi-layer ones. In this paper, the HV system and its performance are described in details, as well as the stability of the novel MPGD-based photon detectors during the physics data taking at COMPASS.

   ↳ physics.ins-dethep-exnucl-exNucl.Instrum.Meth.A(2019)·7 citations
5. 05*

   A facility for direct measurements for nuclear astrophysics at IFIN-HH -- a 3 MV tandem accelerator and an ultra-low background laboratory

   Dana Tudor · Livius Trache🇺🇸 · Alexandra I. Chilug · Ionut C. Stefanescu · Alexandra Spiridon🇷🇴 · Mihai Straticiuc🇷🇴 · Ion Burducea · Ana Pantelica · Romulus Margineanu · Dan G. Ghita🇷🇴 · Doru G. Pacesila · Radu F. Andrei and 3 other authors

   We present a facility for direct measurements at low and very low energies typical for nuclear astrophysics (NA). The facility consists of a small and robust tandem accelerator where irradiations are made, and an ultra-low background laboratory located in a salt mine where very low radio-activities can be measured. Both belong to Horia Hulubei National Institute for Physics and Nuclear Engineering (IFIN-HH) but are situated 120 km apart. Their performances are shown using a few cases where they are used. We argue that this facility is competitive for the study of nuclear reactions induced by alpha particles and by light ions at energies close or down into the Gamow windows. A good case study was the 13C+12C fusion reaction, where the proton evaporation channel leads to an activity with T1/2 = 15 h, appropriate for samples' transfer to the salt mine. Measurements were done using the thick target method down into the Gamow window for energies from Ecm=2.2 MeV, which is the lowest energy ever reached for this reaction, up to 5.3 MeV, using 13C beams from the 3 MV tandetron. The activation method allowed us to determine a cross section of the order of 100 pb. Reactions induced by alphas were also measured. Proton induced resonant reactions were used to calibrate the accelerator terminal voltage. Some results of the experiemnts characterizing the assembly are sown and discussed.

   ↳ physics.acc-phnucl-exNucl.Instrum.Meth.A(2020)·4 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.