Fri·Aug 21, 2020Friday·August 21, 2020

1. 01*

   Measurement of semi-inclusive jet fragmentation functions in Au+Au collisions at sqrt(s_NN) = 200 GeV in STAR

   Saehanseul Oh (for the STAR Collaboration)🇺🇸

   Jet quenching in relativistic heavy ion collisions can have multiple phenomenological consequences: jet energy loss, modification of jet substructure, and induced acoplanarity. In these proceedings, we report a measurement of the jet fragmentation function, which is one of the jet substructure observables, in peripheral Au+Au collisions at sqrt(s_NN) = 200 GeV by the STAR experiment at RHIC. In particular, we use a semi-inclusive population of jets recoiling from a high transverse momentum trigger hadron. The fragmentation function is constructed from the fraction of the transverse momentum of charged particles projected onto the jet axis over the transverse momentum of the jet. In a previous STAR publication of the semi-inclusive charged-jet spectra, the Mixed-Event technique was used along with the semi-inclusive approach to remove the uncorrelated background contributions, which enables the measurement of jet distributions at low transverse momentum and large jet radius (R) in heavy ion collisions. In this analysis we extend this approach to the measurement of jet fragmentation functions. The reported fragmentation functions are corrected for uncorrelated background and instrumental effects via unfolding. The results are compared to those in PYTHIA simulations for pp collisions.

   nucl-exhep-exPoS(2021)·1 citation
2. 02*

   Measurement of $\gamma$+jet and ${\pi }^0$+jet in central Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 200 GeV with the STAR experiment

   Nihar Ranjan Sahoo (for the STAR Collaboration)🇨🇳

   We present the semi-inclusive measurement of charged jets recoiling from direct-photon and ${\pi }^0$ triggers in central Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 200 GeV, using a dataset with integrated luminosity 13 $\mathrm{n}{\mathrm{b}}^{-1}$ recorded by the STAR experiment in 2014. The photon and ${\pi }^0$ triggers are selected within transverse energy (${\mathrm{E}}_{\mathrm{T}}^{\mathrm{trig}}$) between 9 GeV and 20 GeV. Charged jets are reconstructed with the anti-$k_{\mathrm{T}}$ algorithm with resolution parameters R = 0.2 and 0.5. A Mixed-Event technique developed previously by STAR is used to correct the recoil jet yield for uncorrelated background, enabling recoil jet measurements over a broad ${\mathrm{p}}_{\mathrm{T},\mathrm{jet}}$ range. We report fully corrected charged-jet yields recoiling from direct-photon and ${\pi }^0$ triggers for the above two jet radii and also discuss the jet R dependence of in-medium parton energy loss at the top RHIC energy.

   nucl-exhep-exhep-phnucl-thPoS(2021)·7 citations
3. 03*

   Measurement of the Generalized Polarizabilities of the Proton at Intermediate $Q^2$

   H.Fonvieille (1) · J. Beričič (2) · L. Correa (1)(3) · M. Benali (1) · P. Achenbach (3) · C. Ayerbe Gayoso (3) · J.C. Bernauer (4)(5) · A. Blomberg (6) · R. Böhm (3) · D. Bosnar (7) · L. Debenjak (2) · A. Denig (3) and 27 other authors

   Background: Generalized polarizabilities (GPs) are important observables to describe the nucleon structure, and measurements of these observables are still scarce. Purpose: This paper presents details of a virtual Compton scattering (VCS) experiment, performed at the A1 setup at the Mainz Microtron by studying the $ep\to ep\gamma$ reaction. The article focuses on selected aspects of the analysis. Method: The experiment extracted the $P_{LL}-P_{TT}/ϵ$ and $P_{LT}$ structure functions, as well as the electric and magnetic GPs of the proton, at three new values of the four-momentum transfer squared $Q^2$: 0.10, 0.20 and 0.45 GeV${}^2$. Results: We emphasize the importance of the calibration of experimental parameters. The behavior of the measured $ep\to ep\gamma$ cross section is presented and compared to the theory. A detailed investigation of the polarizability fits reveals part of their complexity, in connection with the higher-order terms of the low-energy expansion. Conclusions: The presented aspects are elements which contribute to minimize the systematic uncertainties and improve the precision of the physics results.

   nucl-exhep-phnucl-thPRC(2021)·9 citations
4. 04*

   Octupole correlations in light actinides from the interacting boson model based on the Gogny energy density functional

   K. Nomura🇭🇷 · R. Rodríguez-Guzmán🇰🇼 · Y. M. Humadi · L. M. Robledo🇪🇸 · J. E. García-Ramos🇪🇸

   The quadrupole-octupole coupling and the related spectroscopic properties have been studied for the even-even light actinides ${}^{218-238}$Ra and ${}^{220-240}$Th. The Hartree-Fock-Bogoliubov approximation, based on the Gogny-D1M energy density functional, has been employed as a microscopic input, i.e., to obtain (axially symmetric) mean-field potential energy surfaces as functions of the quadrupole and octupole deformation parameters. The mean-field potential energy surfaces have been mapped onto the corresponding bosonic potential energy surfaces using the expectation value of the $sdf$ Interacting Boson Model (IBM) Hamiltonian in the boson condensate state. The strength parameters of the $sdf$-IBM Hamiltonian have been determined via this mapping procedure. The diagonalization of the mapped IBM Hamiltonian provides energies for positive- and negative-parity states as well as wave functions which are employed to obtain transitional strengths. The results of the calculations compare well with available data from Coulomb excitation experiments and point towards a pronounced octupole collectivity around ${}^{224}$Ra and ${}^{226}$Th.

   ↳ nucl-thnucl-exPRC(2020)·33 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.