Tue·Sep 26, 2023Tuesday·September 26, 2023

1. 01*

   Investigating nonflow contribution subtraction in d-Au collisions with AMPT model

   Zuman Zhang🇨🇳 · Sha Li🇨🇳 · Ning Yu🇨🇳 · Qiao Wu🇨🇳

   This paper presents research that focuses on nonflow contribution subtraction in heavy-ion collisions, using a multiphase transport model (AMPT). Specifically, the study aims to investigate the behavior of charged particle elliptic flow ($v_2$) in d-Au collisions at a collision energy of $\sqrt{s_{\mathrm{NN}}}=200$ GeV and to determine the impact of nonflow sources, such as jet correlations and resonance decays, in small collision systems. To reduce nonflow effects, the per-trigger yield distribution in peripheral d-Au collisions or pp collisions with the same collision energy is subtracted. Our results show that the nonflow effects in central and mid-central collisions are not strongly dependent on subtracting the per-trigger yield distribution in peripheral d-Au collisions or pp collisions. Furthermore, the elliptic flow of charged particles, after removing nonflow effects through two subtracting methods from this work, exhibits consistency in various collision centrality classes. We also discuss comparisons with measurements from d-Au collisions at $\sqrt{s_{\mathrm{NN}}}=200$ GeV. Overall, this work provides valuable insights and serves as a reference for researchers studying nonflow contribution subtraction in experiments with small collision systems.

   nucl-exnucl-thEPJA(2023)·3 citations
2. 02*

   Inclusive e${}^{+}$e${}^{-}$ production in collisions of pions with protons and nuclei in the second resonance region of baryons

   R. Abou Yassine · J. Adamczewski-Musch · O. Arnold · E.T. Atomssa · M. Becker · C. Behnke · J.C. Berger-Chen · A. Blanco · C. Blume · M. Böhmer · L. Chlad · P. Chudoba and 116 other authors

   Inclusive e${}^{+}$e${}^{-}$ production has been studied with HADES in ${\pi }^{-}$ + p, ${\pi }^{-}$ + C and ${\pi }^{-}+{\mathrm{CH}}_2$ reactions, using the GSI pion beam at $\sqrt{s_{\pi p}}$ = 1.49 GeV. Invariant mass and transverse momentum distributions have been measured and reveal contributions from Dalitz decays of ${\pi }^0$, $\eta$ mesons and baryon resonances. The transverse momentum distributions are very sensitive to the underlying kinematics of the various processes. The baryon contribution exhibits a deviation up to a factor seven from the QED reference expected for the dielectron decay of a hypothetical point-like baryon with the production cross section constrained from the inverse $\gamma$ n$\to {\pi }^{-}$ p reaction. The enhancement is attributed to a strong four-momentum squared dependence of the time-like electromagnetic transition form factors as suggested by Vector Meson Dominance (VMD). Two versions of the VMD, that differ in the photon-baryon coupling, have been applied in simulations and compared to data. VMD1 (or two-component VMD) assumes a coupling via the $\rho$ meson and a direct coupling of the photon, while in VMD2 (or strict VMD) the coupling is only mediated via the $\rho$ meson. The VMD2 model, frequently used in transport calculations for dilepton decays, is found to overestimate the measured dielectron yields, while a good description of the data can be obtained with the VMD1 model assuming no phase difference between the two amplitudes. Similar descriptions have also been obtained using a time-like baryon transition form factor model where the pion cloud plays the major role.

   nucl-exPRC(2025)·7 citations
3. 03*

   High precision measurement of the ${}^{99}$Tc $\beta$ spectrum

   Michael Paulsen🇩🇪 · Philipp Ranitzsch🇩🇪 · Martin Loidl🇫🇷 · Matias Rodrigues🇫🇷 · Karsten Kossert🇩🇪 · Xavier Mougeot🇫🇷 · Abilasha Singh🇫🇷 · Sylvain Leblond🇫🇷 · Jörn Beyer🇩🇪 · Lina Bockhorn🇩🇪 · Christian Enss🇩🇪 · Mathias Wegner🇩🇪 · Sebastian Kempf🇩🇪 · Ole Nähle🇩🇪

   Highly precise measurements of the ${}^{99}$Tc beta spectrum were performed in two laboratories using metallic magnetic calorimeters. Independent sample preparations, evaluation methods and analyses yield consistent results and the spectrum could be measured down to less than 1 keV. Consistent beta spectra were also obtained via cross-evaluations of the experimental data sets. An additional independent measurement with silicon detectors in a $4\pi$ configuration confirms the spectrum shape above 25 keV. Detailed theoretical calculations were performed including nuclear structure and atomic effects. The spectrum shape was found to be sensitive to the effective value of the axial-vector coupling constant. Combining measurements and predictions, we extracted $Q_{\beta }=$295.82(16) keV and $g_A^{\text{eff}}=1.530(83)$. Furthermore, we derived the mean energy of the beta spectrum ${\overline{E}}_{\beta }$=98.45(20) keV, $\log f=-0.47660(22)$ and $\log ft=12.3478(23)$.

   nucl-exnucl-thphysics.ins-detPRC(2024)·16 citations
4. 04*

   Beam Charge Asymmetries for Deeply Virtual Compton Scattering on the Proton at CLAS12

   E. Voutier · V. Burkert · S. Niccolai · R. Paremuzyan · A.Afanasev · J.-S. Alvarado-Galeano · M. Atoui · L. Barion · M. Battaglieri · J. Bernauer · A. Bianconi · M. Bondi and 67 other authors

   The parameterization of the nucleon structure through Generalized Parton Distributions (GPDs) shed a new light on the nucleon internal dynamics. For its direct interpretation, Deeply Virtual Compton Scattering (DVCS) is the golden channel for GPDs investigation. The DVCS process interferes with the Bethe-Heitler (BH) mechanism to constitute the leading order amplitude of the $eN\to eN\gamma$ process. The study of the $ep\gamma$ reaction with polarized positron and electron beams gives a complete set of unique observables to unravel the different contributions to the $ep\gamma$ cross section. This separates the different reaction amplitudes, providing a direct access to their real and imaginary parts which procures crucial constraints on the model dependences and associated systematic uncertainties on GPDs extraction. The real part of the BH-DVCS interference amplitude is particularly sensitive to the $D$-term which parameterizes the Gravitational Form Factors of the nucleon. The separation of the imaginary parts of the interference and DVCS amplitudes provides insights on possible higher-twist effects. We propose to measure the unpolarized and polarized Beam Charge Asymmetries (BCAs) of the ${\vec{e}}^{\pm }p\to e^{\pm }p\gamma$ process on an unpolarized hydrogen target with {\tt CLAS12}, using polarized positron and electron beams at 10.6 GeV. The azimuthal and $t$-dependences of the unpolarized and polarized BCAs will be measured over a large $(x_B,Q^2)$ phase space using a 100 day run with a luminosity of 0.66$\times 10^{35}$cm${}^{-2}\cdot$s${}^{-1}$.

   nucl-exhep-ex5 citations
5. 05*

   What can we learn from recent $2\nu \beta \beta$ experiments?

   Dong-Liang Fang🇨🇳

   With recent measurements of the two neutrino double beta decay high precision electron spectra, combining with charge exchange or $\beta$-decay experimental data, we give severe constraints over the current nuclear many body calculations. Our calculation shows that QRPA approach can well reproduce the measured spectra for the two open shell nuclei, ${}^{82}$Se and ${}^{100}$Mo. For the closed shell nucleus ${}^{136}$Xe, QRPA can also reproduce the spectra with proper treatments. We also find that considering the high-lying state reduction, Nuclear Shell Model can also well reproduce the spectra as well as B(GT) strength under a unique quenched $g_A$. For ${}^{136}$Xe, we find that the flip of the sign for the decay strength will lead the spectra to go beyond HSD. These results call for future high precision measurement of charge-exchange reaction.

   ↳ nucl-thnucl-exCPC(2024)·2 citations
6. 06*

   Measurement of prompt $D^{+}$ and $D_s^{+}$ production in $p\mathrm{Pb}$ collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$TeV

   LHCb collaboration: R. Aaij🇳🇱 · A.S.W. Abdelmotteleb🇬🇧 · C. Abellan Beteta🇨🇭 · F. Abudinén🇬🇧 · T. Ackernley🇬🇧 · B. Adeva🇪🇸 · M. Adinolfi🇬🇧 · P. Adlarson🇸🇪 · H. Afsharnia🇫🇷 · C. Agapopoulou🇨🇭 · C.A. Aidala🇺🇸 · Z. Ajaltouni🇫🇷 and 1051 other authors

   The production of prompt $D^{+}$ and $D_s^{+}$ mesons is studied in proton-lead collisions at a centre-of-mass energy of $\sqrt{s_{\mathrm{NN}}}=5.02$TeV. The data sample corresponding to an integrated luminosity of $(1.58\pm 0.02){\mathrm{nb}}^{-1}$ is collected by the LHCb experiment at the LHC. The differential production cross-sections are measured using $D^{+}$ and $D_s^{+}$ candidates with transverse momentum in the range of $0<p_{\mathrm{T}}<14\mathrm{GeV}/c$ and rapidities in the ranges of $1.5<y^{\ast }<4.0$ and $-5.0<y^{\ast }<-2.5$ in the nucleon-nucleon centre-of-mass system. For both particles, the nuclear modification factor and the forward-backward production ratio are determined. These results are compared with theoretical models that include initial-state nuclear effects. In addition, measurements of the cross-section ratios between $D^{+}$, $D_s^{+}$ and $D^0$ mesons are presented, providing a baseline for studying the charm hadronization in lead-lead collisions at LHC energies.

   ↳ hep-exnucl-exJHEP(2024)·16 citations
7. 07*

   Examining the influence of hadronic interactions on the directed flow of identified particles in RHIC Beam Energy Scan energies using UrQMD model

   Aswini Kumar Sahoo🇮🇳 · Prabhupada Dixit🇮🇳 · Md Nasim🇮🇳 · Subhash Singha🇨🇳

   The directed flow of identified particles can serve as a sensitive tool for investigating the interactions during initial and final states in heavy ion collisions. This study examines the rapidity-odd directed flow ($v_1$) and its slope ($d{v}_1/dy$) for ${\pi }^{\pm }$, $K^{\pm }$, p, and $\bar{\mathrm{p}}$ in Au+Au collisions at different collision centralities and beam energies ($\sqrt{s_{\mathrm{N}N}}$ = 7.7, 11.5, 14.5, 19.6, 27, and 39 GeV) using the UrQMD model. We investigate the impact of late-stage hadronic interactions on charge dependent $v_1(y)$ and its slope by modifying the duration of the hadronic cascade lifetime ($\tau$). The energy dependence of $d{v}_1/dy$ for p ($\bar{\mathrm{p}}$) exhibits distinct pattern compared to ${\pi }^{\pm }$ and $K^{\pm }$. Notably, we observe a change in the sign reversal position of proton $d{v}_1/dy$ at different beam energies with varying $\tau$ in central and mid-central collisions. Moreover, the difference in $d{v}_1/dy$ between positively and negatively charged hadrons ($\Delta d{v}_1/dy$) demonstrates a stark centrality dependence for different particle species. The deuteron displays a significant increase in $d{v}_1/dy$ with increasing $\tau$ compared to p and n. This investigation underscores the importance of considering the temporal evolution and duration of the hadronic phase when interpreting the sign reversal, charge splitting of $v_1$ and light nuclei formation at lower RHIC energies.

   ↳ nucl-thnucl-exMod.Phys.Lett.A(2024)·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.