Nuclear Theory·nucl-th

Wednesday·November 23, 2022

14 papers—5 primary·9 cross-listed

06
Dead-cone searches in heavy-ion collisions using the jet tree
Leticia Cunqueiro🇮🇹 · Davide Napoletano🇮🇹 · Alba Soto-Ontoso🇨🇭
We explore the possibility of using the dead cone of heavy quarks as a region of the Lund plane where medium-induced gluon radiation can be isolated and characterised. The filling of the dead cone by medium-induced gluons is expected to be the result of the interplay between the minimum angle of such radiation due to transverse momentum broadening and the dead-cone angle. Since the measurement of a fully corrected Lund plane in heavy-ion collisions is currently challenging, we propose to use jet grooming techniques to identify a particular splitting in the jet tree that is both perturbative and sensitive to the dead-cone effect. To that end, we propose a new jet substructure groomer, dubbed Late- $k_{t}$ , that selects the most collinear splitting in a QCD jet above a certain transverse momentum cutoff $k_{t, cut}$ . The role of $k_{t, cut}$ is to guarantee perturbative splittings, while selecting the most collinear splitting enhances the sensitivity to mass effects. As a proof of concept, we study the angular distribution of the splitting tagged by Late- $k_{t}$ both analytically and with Monte Carlo simulations. First, we derive the logarithmic resummation structure in vacuum and demonstrate its capability to distinguish between inclusive and heavy-flavoured jets. Next, we extend the calculation for in-medium jets and show that medium-induced emissions lead to an enhancement of collinear emissions below the dead cone angle. Numerically, we demonstrate an excellent resilience of Late- $k_{t}$ against uncorrelated thermal background, thus confirming this observable as a potential candidate to unveil medium dynamics around the dead cone regime.
↳ hep-phhep-exnucl-exnucl-thPRD(2023)·27 citations
07
Measurement of global spin alignment of vector mesons at RHIC
Subhash Singha (For STAR collaboration)🇨🇳
We report the measurements of spin alignment ( $ρ_{00}$ ) for $K^{* 0}$ , $K^{* 0}$ , $K^{*+}$ , and $K^{*-}$ vector mesons in RHIC isobar collisions (Zr+Zr and Ru+Ru) at $s_{NN}$ = 200 GeV. We observe the first non-zero spin alignment for $K^{*\pm}$ in heavy-ion collisions. The $K^{*\pm}$ $ρ_{00}$ is about 3.9 $σ$ larger than that of $K^{* 0}$ . The observed difference and the ordering between $K^{*\pm}$ and $K^{* 0}$ are surprising, and require further inputs from theory. When comparing between the isobar and Au+Au collisions, no significant system size dependence in $K^{* 0}$ $ρ_{00}$ is observed within uncertainties.
↳ nucl-exhep-exnucl-thActa Phys.Polon.Supp.(2023)·4 citations
08
Pseudoscalar and Scalar Meson Photoproduction Interpreted by Regge Phenomenology
Igor I. Strakovsky (GWU)🇺🇸 · William J. Briscoe (GWU)🇺🇸 · Olga Cortes Becerra (GWU)🇺🇸 · Michael Dugger (ASU)🇺🇸 · Gary Goldstein (Tufts U.)🇺🇸 · Victor L. Kashevarov (Mainz U.)🇩🇪 · Axel Schmidt (GWU)🇺🇸 · Peter Solazzo (GWU)🇺🇸 · Byung-Geel Yu (Korea Aerospace U.)🇰🇷
We have evaluated pseudoscalar and scalar neutral pion photoproduction in $γ p \to π^{0} p$ and $γ p \to a_{0}^{0} p$ above the resonance region and within Regge phenomenology. Our fit, including GlueX $Σ$ pseudoscalar photoproduction data, shows that previous SLAC $Σ$ measurements for $γ p \to π^{0} p$ above $E_{γ} = 4 GeV$ are at variance with SLAC data with more recent measurements made by GlueX in vicinity of $E_{γ} = 9 GeV$ . The Regge model predicts that the beam polarization asymmetry $Σ$ of the scalar meson is opposite to that of pseudoscalar meson photoproduction, however, the cross sections are similar. While the vector natural parity meson exchange is dominant in both cases, the contribution of the pseudovector unnatural parity meson exchange is very small. Using Regge phenomenology, we predicted high energy behavior for double polarized observables $E$ , $F$ , $G$ , and $H$ for the reactions $γ p \to π^{0} p$ and $γ p \to a_{0}^{0} p$ .
↳ hep-phhep-exnucl-exnucl-thPRC(2023)·3 citations
09
Hybrid stars may have an inverted structure
Chen Zhang🇨🇳 · Jing Ren🇨🇳
We propose a new stellar structure of compact stars, the ``cross stars" that consist of a hadronic matter core and a quark matter crust, with an inverted structure compared to the conventional hybrid stars. This distinct stellar structure naturally arises from the quark matter to hadronic matter transition associated with the chemical potential crossing, in the context of the quark matter hypothesis that either strange or up-down quark matter is the ground state of baryonic matter at low pressure. We find that the interplay between the hadronic matter and quark matter compositions of cross stars can help to reconcile the small radii constraints indicated by the LIGO/Virgo GW170817 event, the large radii constraints set for massive compact stars by recent NICER X-ray observations, and the recent observation of the most-massive pulsar PSR J0952-0607. This leaves more space open for the equation of states of both hadronic matter and quark matter.
↳ astro-ph.HEgr-qchep-phnucl-thPRD(2023)·16 citations
10
Non-perturbative insights into the spectral properties of QCD at finite temperature
Peter Lowdon🇩🇪 · Owe Philipsen🇩🇪
In quantum field theories at finite temperature spectral functions describe how particle systems behave in the presence of a thermal medium. Although data from lattice simulations can in principle be used to determine spectral function characteristics, existing methods rely on the extraction of these quantities from temporal correlators, which requires one to circumvent an ill-posed inverse problem. In these proceedings we report on a recent approach that instead utilises the non-perturbative constraints imposed by field locality to extract spectral function information directly from spatial correlators. In particular, we focus on the application of this approach to lattice QCD data of the spatial pseudo-scalar meson correlator in the temperature range $220 - 960 MeV$ , and outline why this data supports the conclusion that there exists a distinct pion state above the chiral pseudo-critical temperature $T_{pc}$ .
↳ hep-lathep-phhep-thnucl-thEPJ Web Conf.(2022)·5 citations
11
Molecular state interpretation of charmed baryons in the quark model
Ye Yan🇨🇳 · Xiaohuang Hu🇨🇳 · Yuheng Wu🇨🇳 · Hongxia Huang🇨🇳 · Jialun Ping🇨🇳 · Youchang Yang🇨🇳
Stimulated by the observation of $Λ_{c} (2910)^{+}$ by the Belle Collaboration, the $S$ -wave $q q q q ˉ c (q = u or d)$ pentaquark systems with $I$ = 0, $J^{P}$ = $\frac{1}{2}^{-}, \frac{3}{2}^{-} an d \frac{5}{2}^{-}$ are investigated in the framework of quark delocalization color screening model(QDCSM). The real-scaling method is utilized to check the bound states and the genuine resonance states. The root mean square of cluster spacing is also calculated to study the structure of the states and estimate if the state is resonance state or not. The numerical results show that $Λ_{c} (2910)$ cannot be interpreted as a molecular state, and $Σ_{c} (2800)$ cannot be explained as the $N D$ molecular state with $J^{P} = 1/ 2^{-}$ . $Λ_{c} (2595)$ can be interpreted as the molecular state with $J^{P} = \frac{1}{2}^{-}$ and the main component is $Σ_{c} π$ . $Λ_{c} (2625)$ can be interpreted as the molecular state with $J^{P} = \frac{3}{2}^{-}$ and the main component is $Σ_{c}^{*} π$ . $Λ_{c} (2940)$ is likely to be interpreted as a molecular state with $J^{P} = 3/ 2^{-}$ , and the main component is $N D^{*}$ . Besides, two new molecular states are predicted, one is the $J^{P} = 3/ 2^{-}$ $Σ_{c} ρ$ resonance state with the mass around 3140 MeV, another one is the $J^{P} = \frac{5}{2}^{-}$ $Σ_{c}^{*} ρ$ with the mass of 3188.3 MeV.
↳ hep-phnucl-thEPJC(2023)·19 citations
12
Charmed hadron production in high-energy nuclear collisions
Andrea Beraudo🇮🇹 · Arturo De Pace🇮🇹 · Marco Monteno🇮🇹 · Marzia Nardi🇮🇹 · Daniel Pablos🇮🇹 · Francesco Prino🇮🇹
We present a new model for the description of heavy-flavor hadronization in high-energy nuclear (and possibly hadronic) collisions, where the process takes place not in the vacuum, but in the presence of other color charges. We explore its effect on the charmed hadron yields and kinematic distributions once the latter is applied at the end of transport calculations used to simulate the propagation of heavy quarks in the deconfined fireball produced in nuclear collisions. The model is based on the formation of color-singlet clusters through the recombination of charm quarks with light antiquarks or diquarks from the same fluid cell. This local mechanism of color neutralization leads to a strong space-momentum correlation, which provides a substantial enhancement of charmed baryon production -- with respect to expectations based on $e^{+} e^{-}$ collisions -- and of the collective flow of all charmed hadrons. We also discuss the similarities between our model and recently developed mechanisms implemented in QCD event generators to simulate medium corrections to hadronization in the presence of other nearby color charges.
↳ hep-phnucl-exnucl-th0 citations
13
Investigation of octupole collectivity near the $A = 72$ shape-transitional point
M. Spieker · L.A. Riley · P.D. Cottle · K.W. Kemper · D. Bazin · S. Biswas · P.J. Farris · A. Gade · T. Ginter · S. Giraud · J. Li · S. Noji and 4 other authors
Enhanced octupole collectivity is expected in the neutron-deficient Ge, Se and Kr isotopes with neutron number $N \approx 40$ and has indeed been observed for $^{70, 72}$ Ge. Shape coexistence and configuration mixing are, however, a notorious challenge for theoretical models trying to reliably predict octupole collectivity in this mass region, which is known to feature rapid shape changes with changing nucleon number and spin of the system. To further investigate the microscopic configurations causing the prolate-oblate-triaxial shape transition at $A \approx 72$ and their influence on octupole collectivity, the rare isotopes $^{72}$ Se and $^{74, 76}$ Kr were studied via inelastic proton scattering in inverse kinematics. While significantly enhanced octupole strength of $\sim 32$ Weisskopf units (W.u.) was observed for $^{72}$ Se, only strengths of $\sim 15$ W.u. were observed for $^{74, 76}$ Kr. In combination with existing data, the new data clearly question a simple origin of enhanced octupole strengths around $N = 40$ . The present work establishes two regions of distinct octupole strengths with a sudden strength increase around the $A = 72$ shape transitional point.
↳ nucl-exnucl-thPRC(2022)·9 citations
14
$QQq q q ˉ$ Quark System, Compact Pentaquark, and Gauge/String Duality
Oleg Andreev🇩🇪
For the case of two light flavors we propose the stringy description of the system consisting of two heavy and three light quarks, with the aim of exploring the quark organization inside the system and its low-lying Born-Oppenheimer potentials as a function of the heavy quark separation. Our analysis reveals several critical separations related to the processes of string reconnection, breaking and junction annihilation. We find that a compact pentaquark configuration makes the dominant contribution to the potential of the first excited state at small separations, and for separations larger than $0.1 fm$ , the antiquark-diquark-diquark structure emerges. Moreover, it turns out that the length scale of string junction annihilation is the same as that for the $QQ q ˉ q ˉ$ system. We also discuss the relation to the potential of the $QQq$ system and some relations among the masses of hadrons in the heavy quark limit.
↳ hep-phhep-lathep-thnucl-thPRD(2023)·13 citations

Affiliations

first authorsco-authorsvia INSPIRE