Nuclear Theory·nucl-th

Friday·September 17, 2021

12 papers—4 primary·8 cross-listed

05
Universality of a truncated sigma-model
Andrei Alexandru🇺🇸 · Paulo F. Bedaque🇺🇸 · Andrea Carosso🇺🇸 · Andy Sheng🇺🇸
Bosonic quantum field theories, even when regularized using a finite lattice, possess an infinite dimensional Hilbert space and, therefore, cannot be simulated in quantum computers with a finite number of qubits. A truncation of the Hilbert space is then needed and the physical results are obtained after a double limit: one to remove the truncation and another to remove the regulator (the continuum limit). A simpler alternative is to find a model with a finite dimensional Hilbert space belonging to the same universality class as the continuum model (a "qubitization"), so only the space continuum limit is required. A qubitization of the $1 + 1$ dimensional asymptotically free $O (3)$ nonlinear $σ$ -model based on ideas of non-commutative geometry was previously proposed arXiv:1903.06577 and, in this paper, we provide evidence that it reproduces the physics of the $σ$ -model both in the infrared and the ultraviolet regimes.
↳ hep-lathep-thnucl-thquant-phPLB(2022)·11 citations
06
Light Cone Distribution Amplitudes of Heavy-Light Mesons and Quarkonia
Fernando E. Serna🇧🇷 · Bruno El-Bennich🇧🇷
In this work we use the framework of the Dyson-Schwinger and Bethe-Salpeter equations to compute Light-Cone Distribution Amplitudes of heavy-light mesons and quarkonia. In studying the meson properties, we introduce a flavor dependence in the heavy-quark sector of the Bethe-Salpeter ladder kernel which yields improved numerical results for masses and leptonic decay constants of the pseudoscalar $D$ , $D_{s}$ , $B$ and $B_{s}$ mesons. Finally, the corresponding heavy-light Bethe-Salpeter amplitudes are projected onto the light front and we reconstruct the distribution amplitudes of the mesons in the full theory.
↳ hep-phnucl-thPoS(2021)·6 citations
07
Probing the gluonic structure of the deuteron with $J / ψ$ photoproduction in d+Au ultra-peripheral collisions
STAR Collaboration: M. S. Abdallah · B. E. Aboona · J. Adam · L. Adamczyk · J. R. Adams · J. K. Adkins · G. Agakishiev · I. Aggarwal · M. M. Aggarwal · Z. Ahammed · I. Alekseev · D. M. Anderson and 390 other authors
Understanding gluon density distributions and how they are modified in nuclei are among the most important goals in nuclear physics. In recent years, diffractive vector meson production measured in ultra-peripheral collisions (UPCs) at heavy-ion colliders has provided a new tool for probing the gluon density. In this Letter, we report the first measurement of $J / ψ$ photoproduction off the deuteron in UPCs at the center-of-mass energy $s_{_{NN}} = 200 GeV$ in d $+$ Au collisions. The differential cross section as a function of momentum transfer $- t$ is measured. In addition, data with a neutron tagged in the deuteron-going Zero-Degree Calorimeter is investigated for the first time, which is found to be consistent with the expectation of incoherent diffractive scattering at low momentum transfer. Theoretical predictions based on the Color Glass Condensate saturation model and the gluon shadowing model are compared with the data quantitatively. A better agreement with the saturation model has been observed. With the current measurement, the results are found to be directly sensitive to the gluon density distribution of the deuteron and the deuteron breakup, which provides insights into the nuclear gluonic structure.
↳ nucl-exhep-exnucl-thPRL(2022)·30 citations
08
The production of doubly charmed exotic hadrons in heavy ion collisions
Yuanyuan Hu🇨🇳 · Jinfeng Liao🇺🇸 · Enke Wang🇨🇳 · Qian Wang🇨🇳 · Hongxi Xing🇨🇳 · Hui Zhang🇨🇳
Hadron spectroscopy provides direct physical measurements that shed light on the non-perturbative behavior of quantum chromodynamics (QCD). In particular, various exotic hadrons such as the newly observed $T_{cc}^{+}$ by the LHCb collaboration, offer unique insights on the QCD dynamics in hadron structures. In this letter, we demonstrate how heavy ion collisions can serve as a powerful venue for hadron spectroscopy study of doubly charmed exotic hadrons by virtue of the extremely charm-rich environment created in such collisions. The yields of $T_{cc}^{+}$ as well as its potential isospin partners are computed within the molecular picture for Pb-Pb collisions at center-of-mass energy $2.76 TeV$ . We find about three-order-of-magnitude enhancement in the production of $T_{cc}^{+}$ in Pb-Pb collisions as compared with the yield in proton-proton collisions, with a moderately smaller enhancement in the yields of the isospin partners $T_{cc}^{0}$ and $T_{cc}^{++}$ . The $T_{cc}^{+}$ yield is comparable to that of the $X (3872)$ in the most central collisions while shows a considerably stronger decrease toward peripheral collisions, due to a "threshold" effect of the required double charm quarks for $T_{cc}^{+}$ . Final results for their rapidity and transverse momentum $p_{T}$ dependence as well as the elliptic flow coefficient are reported and can be tested by future experimental measurements.
↳ hep-phhep-exnucl-exnucl-thPRD(2021)·56 citations
09
Weak transition form factors of heavy-light pseudoscalar mesons for space- and timelike momentum transfers
Oliver Heger🇦🇹 · María Gómez-Rocha🇪🇸 · Wolfgang Schweiger🇦🇹
Weak $B^{-} \to D^{0}, π^{0}$ and $D^{-} \to K^{0}, π^{0}$ transition form factors are described in both the space- and time-like momentum transfer regions, within a constituent-quark model. Neutrino-meson scattering and semileptonic weak decays are formulated within the point form of relativistic quantum mechanics to end up with relativistic invariant process amplitudes from which meson transition currents and form factors are extracted in an unambiguous way. For space-like momentum transfers, form factors depend on the frame in which the $W M M^{'}$ vertex is considered. Such a frame dependence is expected from a pure valence-quark picture, since a complete, frame independent description of form factors is supposed to include non-valence contributions. The most important of such contributions are the $Z$ -graphs, which are, however, suppressed in the infinite-momentum frame ( $q^{2} < 0$ ). On the other hand, they can play a significant role in the Breit frame ( $q^{2} < 0$ ) and in the direct decay calculation ( $q^{2} > 0$ ), as a comparison with the infinite-momentum-frame form factors (analytically continued to $q^{2} > 0$ ) reveals. Numerical results for the analytically continued infinite-momentum-frame form factors agree very well with lattice data in the time-like momentum transfer region and the experimental value for the slope of the $F_{B \to D}^{+}$ transition form factor at zero recoil is reproduced satisfactorily. These predictions satisfy heavy-quark-symmetry constraints and their $q^{2}$ dependence is well approximated by a pole fit, reminiscent of a vector-meson-dominance-like decay mechanism. We discuss how such a decay mechanism can be accommodated within an extension of our constituent-quark model, by allowing for a non-valence component in the meson wave functions. We also address the question of wrong cluster properties inherent in the Bakamjian-Thomas formulation.
↳ hep-phnucl-thPRD(2021)·7 citations
10
Reconstruction of high-energy part of gamma-ray spectrum in thermal neutron capture by $^{113}$ Cd
V.A. Plujko · O.M. Gorbachenko · K.M. Solodovnyk · V.M. Petrenko
The average gamma-ray spectrum $^{114}$ Cd after thermal neutron capture in $^{113}$ Cd was evaluated in units of mb/MeV. Two approaches are considered for estimation of the average gamma-ray spectrum with normalization of the experimental data: mean spectra for all gamma-energies were found by averaging frequency polygon for experimental data histogram, and mean spectra were estimated as the combination of theoretical values at low gamma-ray energies and averaging experimental data in high-energy range. The experi mental spectra were evaluated from the gamma-intensities presented by Mheemeed et al. [A. Mheemeed et al., Nucl. Phys. A 412 (1984) 113] and Belgya et al [T. Belgya et al., EPJ Web of Conf. 146 (2017) 05009]. They were normalized to the average theoretical spectrum which was calculated using EMPIRE and TALYS codes. The procedure of normalization of the high-energy part of the spectrum was described. Estimated $γ$ - spectra for $^{113}$ Cd(n,{x $γ$ }) reaction induced by thermal neutrons were presented.
↳ nucl-exnucl-thNucl.Phys.Atom.Energy(2021)·0 citations
11
Charmonium suppression in ultra-relativistic proton-proton collisions at LHC energies: A hint for QGP in small systems
Captain R. Singh🇮🇳 · Suman Deb🇮🇳 · Raghunath Sahoo🇮🇳 · Jan-e Alam🇮🇳
Proton-proton ( $pp$ ) collision has been considered as a baseline to study the system produced in relativistic heavy-ion (AA) collisions with the basic assumption that no thermal medium is formed in $pp$ collisions. This warrants a cautious analysis of the system produced in $pp$ collisions at relativistic energies.In this work we investigate the charmonium suppression in $pp$ collisions at $s = 5.02, 7$ and $13$ TeV energies. Further, charmonium suppression has been studied for various event multiplicities and transverse momenta by including the mechanisms of color screening, gluonic dissociation, collisional damping along with regeneration due to correlated $c c ˉ$ pairs. Here we obtain a net suppression of charmonia at high-multiplicity events indicating the possibility of the formation of quark-gluon plasma in $pp$ collisions.
↳ hep-phhep-exnucl-exnucl-thEPJC(2022)·19 citations
12
Heavy-meson chiral Lagrangians, effective flavored couplings, SU(4) flavor breaking and their consequences
Bruno El-Bennich🇧🇷 · Fernando E. Serna🇧🇷
We review heavy quark flavor and spin symmetries, their exploitation in heavy meson effective theories and the flavored couplings of charmed and light mesons in the definition of their effective Lagrangians. We point out how nonperturbative continuum QCD approaches based on Dyson-Schwinger and Bethe-Salpeter equations can be used to calculate strong and leptonic decays of open-charm mesons and heavy quarkonia. The strong decay $D^{*} \to D π$ serves as a benchmark, as it is the only physical open-charm observable that can be related to the effective Lagrangian's couplings. Nonetheless, a quantitative comparison of $D^{*} D π$ , $ρ D D$ , $ρ D^{*} D$ and $ρ D^{*} D^{*}$ couplings for a range of off-shell momenta of the $ρ$ -meson invalidates SU(4) $_{F}$ symmetry relations between these couplings. Thus, besides the breaking of flavor symmetry by mass terms in the Lagrangians, the flavor-symmetry breaching in couplings and their dependence on the $ρ$ -meson virtuality cannot be ignored. We also take the opportunity to present new results for the effective $J / ψ D D$ and $J / ψ D^{*} D$ couplings. We conclude this contribution with a discussion on how the description of pseudoscalar and vector $D$ , $D_{s}$ , $B$ and $B_{s}$ meson properties can be drastically improved with a modest modification of the flavor-dependence in the Bethe-Salpeter equation.
↳ hep-phhep-exhep-latnucl-thPoS(2021)·4 citations

Affiliations

first authorsco-authorsvia INSPIRE