Thu·Apr 23, 2020Thursday·April 23, 2020

1. 01*

   Unstable states in dissociation of relativistic nuclei. Recent findings and prospects of researches

   D.A. Artemenkov🇷🇺 · V. Bradnova🇷🇺 · M.M. Chernyavsky · E. Firu🇷🇴 · M. Haiduc🇷🇴 · N.K. Kornegrutsa · A.I. Malakhov🇷🇺 · E. Mitsova · A. Neagu🇷🇴 · N.G. Peresadko · V.V. Rusakova🇷🇺 · R. Stanoeva🇧🇬 and 3 other authors

   The invariant mass method is used to identify the ${}^8$Be and ${}^9$B nuclei and Hoyle state formed in dissociation of relativistic nuclei in a nuclear track emulsion. It is shown that to identify these extremely short-lived states in the case of the isotopes ${}^9$Be, ${}^{10}$B, ${}^{10}$C, ${}^{11}$C, ${}^{12}$C, and ${}^{16}$O, it is sufficient to determine the invariant mass as a function of the angles in pairs and triples of He and H fragments in the approximation of the conservation of momentum per nucleon of the parent nucleus. According to the criteria established in this way, the contribution of these three unstable states was evaluated in the relativistic fragmentation of the ${}^{28}$Si and ${}^{197}$Au nuclei.

   nucl-exEPJA(2020)·14 citations
2. 02*

   Laser Calibration System for Time of Flight Scintillator Arrays

   A. Denniston🇺🇸 · E.P. Segarra🇺🇸 · A. Schmidt🇺🇸 · A. Beck · S. May-Tal Beck · R. Cruz-Torres🇺🇸 · F. Hauenstein🇺🇸 · A. Hrnjic🇺🇸 · T. Kutz🇺🇸 · A. Nambrath🇺🇸 · J.R. Pybus🇺🇸 · P. Toledo🇺🇸 and 5 other authors

   A laser calibration system was developed for monitoring and calibrating time of flight (TOF) scintillating detector arrays. The system includes setups for both small- and large-scale scintillator arrays. Following test-bench characterization, the laser system was recently commissioned in experimental Hall B at the Thomas Jefferson National Accelerator Facility for use on the new Backward Angle Neutron Detector (BAND) scintillator array. The system successfully provided time walk corrections, absolute time calibration, and TOF drift correction for the scintillators in BAND. This showcases the general applicability of the system for use on high-precision TOF detectors.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2020)·7 citations
3. 03*

   The CLAS12 Backward Angle Neutron Detector (BAND)

   E.P. Segarra · F. Hauenstein · A. Schmidt · A. Beck · S. May-Tal Beck · R. Cruz-Torres · A. Denniston · A. Hrnjic · T. Kutz · A. Nambrath · J.R. Pybus · K. Pryce and 16 other authors

   The Backward Angle Neutron Detector (BAND) of CLAS12 detects neutrons emitted at backward angles of $155^{\circ }$ to $175^{\circ }$, with momenta between $200$ and $600$ MeV/c. It is positioned 3 meters upstream of the target, consists of $18$ rows and $5$ layers of $7.2$ cm by $7.2$ cm scintillator bars, and read out on both ends by PMTs to measure time and energy deposition in the scintillator layers. Between the target and BAND there is a 2 cm thick lead wall followed by a 2 cm veto layer to suppress gammas and reject charged particles. This paper discusses the component-selection tests and the detector assembly. Timing calibrations (including offsets and time-walk) were performed using a novel pulsed-laser calibration system, resulting in time resolutions better than $250$ ps (150 ps) for energy depositions above 2 MeVee (5 MeVee). Cosmic rays and a variety of radioactive sources were used to calibration the energy response of the detector. Scintillator bar attenuation lengths were measured. The time resolution results in a neutron momentum reconstruction resolution, $\delta p/p<1.5$\% for neutron momentum $200\le p\le 600$ MeV/c. Final performance of the BAND with CLAS12 is shown, including electron-neutral particle timing spectra and a discussion of the off-time neutral contamination as a function of energy deposition threshold.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2020)·14 citations
4. 04*

   Polarized proton spin filter for epithermal neutron based on dynamic nuclear polarization using photo-excited triplet electron spins

   Shusuke Takada🇯🇵 · Kenichiro Tateishi🇯🇵 · Yasuo Wakabayashi🇯🇵 · Yoshimasa Ikeda🇯🇵 · Tamaki Yoshioka🇯🇵 · Yoshie Otake🇯🇵 · Tomohiro Uesaka🇯🇵

   For the polarization of neutrons with an energy level of \textcolor{black}{$>0.1$ eV}, we developed a novel polarized proton spin filter based on dynamic nuclear polarization using photo-excited triplet electron spins. The spin filter consists of a single crystal of naphthalene doped with deuterated pentacene and has a size of $\varphi 15\times 4$ ${\mathrm{mm}}^3$, allowing it to cover a wide beam diameter. It was operated in 0.35 T and at 90 K. We succeeded in polarizing neutrons in the energy range $0.1-10$ eV using a RIKEN accelerator-driven compact neutron source. The averaged values of the proton and neutron polarization were $0.250\pm 0.050$ and $0.076\pm 0.015$, respectively.

   ↳ physics.ins-dethep-exnucl-exPTEP(2020)·4 citations
5. 05*

   Comparative study of charged multiplicities and moments in $pp$ collisions at $\sqrt{s}$=7 TeV in the forward region at the LHC

   R. Aggarwal🇮🇳 · M. Kaur🇮🇳

   Charged particle multiplicities in proton-proton collisions measured in the LHCb detector at a centre-of-mass energy of $\sqrt{s}$=7 TeV in different windows of pseudorapidity $\eta$, in the forward region of the vertex detector are studied by using different statistical distributions. Three distributions are compared with the data and the moments of the distributions are calculated. The data constituting two sets, one of minimum bias events and another of hard QCD events are analysed. The distributions considered derive from different functional forms based on underlying interaction dynamics. The analysis complements the multiplicity analysis done by LHCb in terms of Monte Carlo event generators. The present analysis is from a different perspective, using statistical distributions.

   ↳ hep-exnucl-exPRD(2020)·2 citations
6. 06*

   Centrifugal effects in N-Delta states

   J. A. Niskanen🇫🇮

   Recently it has been pointed out that in the two-baryon $N\Delta$ or $\Delta \Delta$ system the width of the state is greatly diminished due to the relative kinetic energy of the two baryons, since the internal energy of the particles, available for pionic decay, is smaller. For nonzero orbital angular momenta this effect becomes state dependent. Also the real part of the $N\Delta$ energy can get contribution from the centrifugal barrier leading to rotational series of diffuse states. Obviously, these states may have an interpretation as isospin one dibaryons. Direct and explicit calculations for this are presented with some details of the coupled state wave functions displayed. With finite expectation values of these repulsive effects it may be possible to define state dependent effective thresholds for $N\Delta$ states and these, in turn, can show resonant like behavior.

   ↳ nucl-thhep-exhep-phnucl-exPRC(2020)·2 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.