Nuclear Theory·nucl-th

Tuesday·July 26, 2022

6 papers—3 primary·3 cross-listed

04
Measurement of the Parity-Odd Angular Distribution of Gamma Rays From Polarized Neutron Capture on $^{35}$ Cl
N. Fomin · R. Alarcon · L. Alonzi · E. Askanazi · S. Baeßler · S. Balascuta · L. Barrón-Palos · A. Barzilov · D. Blyth · J.D. Bowman · N. Birge · J.R. Calarco and 52 other authors
We report a measurement of two energy-weighted gamma cascade angular distributions from polarized slow neutron capture on the $^{35}$ Cl nucleus, one parity-odd correlation proportional to $s_{n} \cdot k_{γ}$ and one parity-even correlation proportional to $s_{n} \cdot k_{n} \times k_{γ}$ . A parity violating asymmetry can appear in this reaction due to the weak nucleon-nucleon (NN) interaction which mixes opposite parity S and P-wave levels in the excited compound $^{36}$ Cl nucleus formed upon slow neutron capture. If parity-violating (PV) and parity-conserving (PC) terms both exist, the measured differential cross section can be related to them via $\frac{d σ}{d Ω} \propto 1 + A_{γ, P V} cos θ + A_{γ, P C} sin θ$ . The PV and PC asymmetries for energy-weighted gamma cascade angular distributions for polarized slow neutron capture on $^{35}$ Cl averaged over the neutron energies from 2.27~meV to 9.53~meV were measured to be $A_{γ, P V} = (- 23.9 \pm 0.7) \times 1 0^{- 6}$ and $A_{γ, P C} = (0.1 \pm 0.7) \times 1 0^{- 6}$ . These results are consistent with previous experimental results. Systematic errors were quantified and shown to be small compared to the statistical error. These asymmetries in the angular distributions of the gamma rays emitted from the capture of polarized neutrons in $^{35}$ Cl were used to verify the operation and data analysis procedures for the NPDGamma experiment which measured the parity-odd asymmetry in the angular distribution of gammas from polarized slow neutron capture on protons.
↳ nucl-exnucl-thPRC(2022)·2 citations
05
Colliding and Fixed Target Mode in a Single Experiment -- A Novel Approach to Study the Matter under New Extreme Conditions
Oleksandr V. Vitiuk🇵🇱 · Valery M. Pugatch🇺🇦 · Kyrill A. Bugaev🇺🇦 · Nazar S. Yakovenko🇺🇦 · Pavlo P. Panasiuk🇺🇦 · Elizaveta S. Zherebtsova🇷🇺 · Vasyl M. Dobishuk🇺🇦 · Sergiy B. Chernyshenko🇺🇦 · Borys E. Grinyuk🇺🇦 · Violetta Sagun🇵🇹 · Oleksii Ivanytskyi🇵🇱
Here, we propose a novel approach to experimentally and theoretically study the properties of QCD matter under new extreme conditions, namely having an initial temperature over 300~MeV and baryonic charge density over three times the values of the normal nuclear density. According to contemporary theoretical knowledge, such conditions were not accessible during the early Universe evolution and are not accessible now in the known astrophysical phenomena. To achieve these new extreme conditions, we proposed performing high-luminosity experiments at LHC or other colliders by means of scattering the two colliding beams at the nuclei of a solid target that is fixed at their interaction region. Under plausible assumptions, we estimate the reaction rate for the p+C+p and Pb+Pb+Pb reactions and discuss the energy deposition into the target and possible types of fixed targets for such reactions. To simulate the triple nuclear collisions, we employed the well-known UrQMD 3.4 model for the beam center-of-mass collision energies 2.76 TeV. As a result of our modeling, we found that, in the most central and simultaneous triple nuclear collisions, the initial baryonic charge density is approximately three times higher than the one achieved in the ordinary binary nuclear collisions at this energy.
↳ hep-phhep-exnucl-thParticles(2022)·0 citations
06
Probing initial geometrical anisotropy and final azimuthal anisotropy in heavy-ion collisions at Large Hadron Collider energies through event-shape engineering
Suraj Prasad🇮🇳 · Neelkamal Mallick🇮🇳 · Sushanta Tripathy🇮🇹 · Raghunath Sahoo🇮🇳
Anisotropic flow is accredited to have effects from the initial state geometry and fluctuations in the nuclear overlap region. The elliptic flow ( $v_{2}$ ) and triangular flow ( $v_{3}$ ) coefficients of the final state particles are expected to have influenced by eccentricity ( $ε_{2}$ ) and triangularity ( $ε_{3}$ ) of the participants, respectively. In this work, we study $v_{2}$ , $v_{3}$ , $ε_{2}$ , $ε_{3}$ and the correlations among them with respect to event topology in the framework of a multi-phase transport model (AMPT). We use transverse spherocity and reduced flow vector as event shape classifiers in this study. Transverse spherocity has the unique ability to separate events based on geometrical shapes, i.e., jetty and isotropic, which pertain to pQCD and non-pQCD domains of particle production in high-energy physics, respectively. We use the two-particle correlation method to study different anisotropic flow coefficients. We confront transverse spherocity with a more widely used event shape classifier -- reduced flow vector ( $q_{n}$ ) and they are found to have significant (anti-)correlations among them. We observe significant spherocity dependence on $v_{2}$ , $v_{3}$ and $ε_{2}$ . This work also addresses transverse momentum dependent crossing points between $v_{2}$ and $v_{3}$ , which varies for different centrality and spherocity percentiles.
↳ hep-phhep-exhep-thnucl-ex+1PRD(2023)·26 citations

Affiliations

first authorsco-authorsvia INSPIRE

Measurement of the Parity-Odd Angular Distribution of Gamma Rays From Polarized Neutron Capture on 35Cl

Colliding and Fixed Target Mode in a Single Experiment -- A Novel Approach to Study the Matter under New Extreme Conditions

Probing initial geometrical anisotropy and final azimuthal anisotropy in heavy-ion collisions at Large Hadron Collider energies through event-shape engineering

Affiliations

Measurement of the Parity-Odd Angular Distribution of Gamma Rays From Polarized Neutron Capture on $^{35}$ Cl