Tue·Oct 16, 2018Tuesday·October 16, 2018

1. 01*

   Overview on heavy-flavour at RHIC and LHC

   Andrea Dubla🇩🇪

   The PHENIX and STAR Collaborations at the Relativistic Heavy-Ion Collider and ALICE, CMS, ATLAS and LHCb Collaborations at the Large Hadron Collider have measured the production of charmonium and bottonium states as well as open heavy flavor hadrons via their hadronic and semi-leptonic decays at mid-rapidity and in the semi-muonic decay channel at forward rapidity in pp, p--A and A--A collisions in an energy domain that ranges from $\sqrt{s}$ = 0.2 TeV to $\sqrt{s}$ = 13 TeV in pp collisions and from $\sqrt{s_{\mathrm{NN}}}$ = 0.2 TeV to $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV in A--A collisions. In this contribution the latest experimental results will be reviewed.

   nucl-exMDPI Proc.(2019)·0 citations
2. 02*

   Machine Learning based jet momentum reconstruction in heavy-ion collisions

   Rüdiger Haake (Yale University)🇺🇸 · Constantin Loizides (ORNL)🇺🇸

   The precise reconstruction of jet transverse momenta in heavy-ion collisions is a challenging task. A major obstacle is the large number of (mainly) low-$p_{\mathrm{T}}$ particles overlaying the jets. Strong region-to-region fluctuations of this background complicate the jet measurement and lead to significant uncertainties. In this paper, a novel approach to correct jet momenta (or energies) for the underlying background in heavy-ion collisions is introduced. The proposed method makes use of common Machine Learning techniques to estimate the jet transverse momentum based on several parameters, including properties of the jet constituents. Using a toy model and HIJING simulations, the performance of the new method is shown to be superior to the established standard area-based background estimator. The application of the new method to data promises the measurement of jets down to extremely low transverse momenta, unprecedented thus far in data on heavy-ion collisions.

   nucl-exnucl-thPRC(2019)·48 citations
3. 03*

   Fabrication and Characterization of High-Purity Germanium Detectors with Amorphous Germanium Contacts

   X.-H. Meng🇨🇳 · G.-J. Wang🇺🇸 · M.-D. Wagner · H. Mei🇺🇸 · W.-Z. Wei🇺🇸 · J. Liu🇺🇸 · G. Yang🇺🇸 · D.-M. Mei🇺🇸

   Large, high-purity, germanium (HPGe) detectors are needed for neutrinoless double-beta decay and dark matter experiments. Currently, large (> 4 inches in diameter) HPGe crystals can be grown at the University of South Dakota (USD). We verify that the quality of the grown crystals is sufficient for use in large detectors by fabricating and characterizing smaller HPGe detectors made from those crystals. We report the results from eight detectors fabricated over six months using crystals grown at USD. Amorphous germanium (a-Ge) contacts are used for blocking both electrons and holes. Two types of geometry were used to fabricate HPGe detectors. As a result, the fabrication process of small planar detectors at USD is discussed in great detail. The impact of the procedure and geometry on the detector performance was analyzed for eight detectors. We characterized the detectors by measuring the leakage current, capacitance, and energy resolution at 662 keV with a Cs-137 source. Four detectors show good performance, which indicates that crystals grown at USD are suitable for making HPGe detectors.

   ↳ physics.ins-detnucl-exJINST(2019)·22 citations
4. 04*

   Centrality and pseudorapidity dependence of the transverse energy density in pPb collisions at $\sqrt{s_{\mathrm{NN}}}=$ 5.02 TeV

   CMS Collaboration

   The almost hermetic coverage of the CMS detector is used to measure the distribution of transverse energy, $E_{\mathrm{T}}$, over 13.2 units of pseudorapidity, $\eta$, for pPb collisions at a center-of-mass energy per nucleon pair of $\sqrt{s_{\mathrm{NN}}}=$ 5.02 TeV. The huge angular acceptance exploits the fact that the CASTOR calorimeter at $-6.6$ $<$ $\eta$ $<$ $-5.2$ is effectively present on both sides of the colliding system because of a switch in the proton-going and lead-going beam directions. This wide acceptance enables the study of correlations between well-separated angular regions and makes the measurement a particularly powerful test of event generators. For minimum bias pPb collisions the maximum value of d$E_{\mathrm{T}}/$d$\eta$ is 22 GeV, which implies an $E_{\mathrm{T}}$ per participant nucleon pair comparable to that of peripheral PbPb collisions at $\sqrt{s_{\mathrm{NN}}}=$ 2.76 TeV. The increase of d$E_{\mathrm{T}}/$d$\eta$ with centrality is much stronger for the lead-going side than for the proton-going side. The $\eta$ dependence of d$E_{\mathrm{T}}/$d$\eta$ is sensitive to the $\eta$ range in which the centrality variable is defined. Several modern generators are compared to these results but none is able to capture all aspects of the $\eta$ and centrality dependence of the data and the correlations observed between different $\eta$ regions.

   ↳ hep-exnucl-exPRC(2019)·21 citations
5. 05*

   Simple description of the temperature dependencies of the width of fission-fragment mass yield in 197Au and 209Bi at intermediate energies

   V. Yu. Denisov🇺🇦 · O. A. Belyanovska · V. P. Khomenkov · I. Yu. Sedykh🇷🇺 · K. M. Sukhyy

   Simple approach is used to a description of the experimental data for the widths of fission fragment mass yields in 197Au and 209Bi at low and intermediate energies. This approach based on both the expression for the temperature dependence of the width of fission fragment mass yield and the mass of the most probable fragment. The expression for the width of fission fragment mass yield depends on the mass of the most probable fragment, the surface terms of the energy level density parameter, the temperature and the stiffness parameter of the potential related to mass-asymmetric degree of freedom. It is shown that the contribution of the surface term of the energy level density parameter into the width is important for description of the experimental data in wide range of energies.

   ↳ nucl-thnucl-exCPC(2019)·2 citations
6. 06*

   Systematic investigation of the high-$K$ isomers and the high-spin rotational bands in the neutron rich Nd and Sm isotopes by a particle-number conserving method

   Zhen-Hua Zhang

   The rotational properties of the neutron rich Nd and Sm isotopes with mass number $A\approx 150$ are systematically investigated using the cranked shell model with pairing correlations treated by a particle-number conserving method, in which the Pauli blocking effects are taken into account exactly. The 2-quasiparticle states in even-even Nd and Sm isotopes with excitation energies lower than 2.5~MeV are systematically calculated. The available data can be well reproduced and some possible 2 and 4-quasiparticle isomers are also suggested for future experiments. The experimentally observed rotational frequency variations of moments of inertia for the even-even and odd-$A$ nuclei are reproduced very well by the calculations. The effects of high-order deformation ${\epsilon }_6$ on the 2-quasiparticle excitation energies and moments of inertia of the ground state bands in even-even Nd and Sm isotopes are analyzed in detail. By analyzing the occupation probability $n_{\mu }$ of each cranked Nilsson orbitals near the Fermi surface and the contribution of each major shell to the angular momentum alignments, the alignment mechanism in these nuclei is understood clearly.

   ↳ nucl-thnucl-exPRC(2018)·13 citations
7. 07*

   Observation of $\Xi (1620{)}^0$ and evidence for $\Xi (1690{)}^0$ in ${\Xi }_c^{+}\to {\Xi }^{-}{\pi }^{+}{\pi }^{+}$ decays

   Belle collaboration: M. Sumihama · I. Adachi · J. K. Ahn · H. Aihara · S. Al Said · D. M. Asner · H. Atmacan · T. Aushev · R. Ayad · V. Babu · I. Badhrees · S. Bahinipati and 173 other authors

   We report the first observation of the doubly-strange baryon $\Xi (1620{)}^0$ in its decay to ${\Xi }^{-}{\pi }^{+}$ via ${\Xi }_c^{+}\to {\Xi }^{-}{\pi }^{+}{\pi }^{+}$ decays based on a $980{\mathrm{fb}}^{-1}$ data sample collected with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider. The mass and width are measured to be 1610.4 $\pm$ 6.0 (stat) ${}_{-3.5}^{+5.9}$ (syst)~MeV$/c^2$ and 59.9 $\pm$ 4.8 (stat) ${}_{-3.0}^{+2.8}$ (syst)~MeV, respectively. We obtain 4.0$\sigma$ evidence of the $\Xi (1690{)}^0$ with the same data sample. These results shed light on the structure of hyperon resonances with strangeness $S=-2$.

   ↳ hep-exnucl-exPRL(2019)·64 citations
8. 08*

   The GAmmas from Nuclear Decays Hiding from Investigators (GANDHI) Experiment

   Giovanni Benato🇺🇸 · Alexey Drobizhev🇺🇸 · Surjeet Rajendran🇺🇸 · Harikrishnan Ramani🇺🇸

   We propose a high statistics experiment to search for invisible decay modes in nuclear gamma cascades. A radioactive source (such as ${}^{60}$Co or ${}^{24}$Na) that triggers gamma cascades is placed in the middle of a large, hermetically sealed scintillation detector, enabling photon identification with high accuracy. Invisible modes are identified by establishing the absence of a photon in a well-identified gamma cascade. We propose the use of fast scintillators with nanosecond timing resolution, permitting event rates as high as $10^7$ Hz. Our analysis of the feasibility of this setup indicates that branching fractions as small as $10^{-12}-10^{-14}$ can be probed. This experimental protocol benefits from the fact that a search for invisible modes is penalized for weak coupling only in the production of the new particle. If successfully implemented, this experiment is an exquisite probe of particles with mass below $\sim$4 MeV that lie in the poorly constrained supernova "trapping window" that exists between 100 keV - 30 MeV. Such particles have been invoked as mediators between dark matter and nucleons, explain the proton radius and $(g-2{)}_{\mu }$ anomalies and potentially power the shock wave in type II supernovae. The hadronic axion could also be probed with modifications to the proposed setup.

   ↳ hep-phnucl-exphysics.ins-detPRD(2019)·19 citations
9. 09*

   Calibration of the compact neutron spectrometer at PTB

   M. Osipenko🇮🇹 · V. Ceriale🇮🇹 · G. Gariano🇮🇹 · M. Girolami🇮🇹 · S. Cerchi🇮🇹 · R. Nolte🇩🇪 · E. Pirovano🇩🇪 · M. Ripani🇮🇹 · D.M. Trucchi🇮🇹

   In the present article we describe the calibration measurements of the compact neutron spectrometer at certified PTB neutron source. The spectrometer is based on two diamond detectors enclosing the Li-6 neutron converter. The incident neutron energy is measured through the sum of energies of the two conversion reaction products: t and alpha. The prototype used in this work was based on two 4x4 mm2, 100 um thick single crystal CVD commercial diamond plates. The measurements were performed in the fission spectrum domain at five different neutron energies varying from 0.3 up to 2 MeV. The obtained data showed a very good neutron energy reconstruction, i.e. in agreement with its reference values within statistical uncertainties or with deviation below 11 keV in absolute scale. The energy resolution of the spectrometer was found to be about 100 keV (RMS) with a small (about 9 keV/MeV) rising trend towards higher energies. The measured detection efficiency was found to be compatible with expectations based on analytical calculations and on Geant4 simulations within 3% statistical and 4% systematic precision.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2019)·0 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.