Nuclear Theory·nucl-th

Wednesday·January 30, 2019

12 papers—7 primary·5 cross-listed

08
Charmonium Excitation functions in $p ˉ$ A Collisions
Gy. Wolf🇭🇺 · G. Balassa🇭🇺 · P. Kovacs🇭🇺 · M. Zetenyi🇭🇺 · S.H. Lee🇰🇷
We study the excitation function of the low-lying charmonium state: $Ψ$ (3686) in $p ˉ$ Au collisions taking into account their in-medium propagation. The time evolution of the spectral functions of the charmonium state is studied with a BUU type transport model. We calculated the excitation function of $Ψ$ (3686) production and show that it is strongly effected by the medium. The energy regime will be available for the PANDA experiment.
↳ hep-phnucl-thActa Phys.Polon.Supp.(2018)·4 citations
09
Probing nucleon's spin structures with polarized Drell-Yan in the Fermilab SpinQuest experiment
Andrew Chen🇺🇸 · J.C. Peng🇺🇸 · H. Leung🇺🇸 · M. Tian🇺🇸 · N. Makins🇺🇸 · M. Brooks🇺🇸 · A. Klein🇺🇸 · D. Kleinjan🇺🇸 · K. Liu🇺🇸 · M. McCumber🇺🇸 · P. McGaughey🇺🇸 · J. Miraal-Martinez🇺🇸 and 42 other authors
Although the proton was discovered about 100 years ago, its spin structure still remains a mystery. Recent studies suggest that the orbital angular momentum of sea quarks could significantly contribute to the proton's spin. The SeaQuest experiment, which recently completed data collection, probed the unpolarized light quark sea distributions of the proton using the Drell-Yan process. Its successor, the SpinQuest (E1039), will access the $u ˉ$ and $d ˉ$ Sivers functions using polarized NH $_{3}$ and ND $_{3}$ targets. A non-zero Sivers asymmetry, observed in SpinQuest, would be a strong indication of non-zero sea-quark orbital angular momentum. The SpinQuest experiment can also probe the sea quark's transversity distribution, which is relevant for the determination of proton's tensor charge. Recent study suggests that sea-quarks might contribute significantly to deuteron's tensor polarized structure functions. This can be further probed in SpinQuest using tensor polarized ND $_{3}$ target. The current status and future plan of the experiment are presented.
↳ nucl-exnucl-thPoS(2019)·22 citations
10
Meson deformation by magnetic fields in lattice QCD
Koichi Hattori🇯🇵 · Arata Yamamoto🇯🇵
We study light meson properties in a magnetic field, focusing on a charged pion and a charged and polarized rho meson, in quenched lattice QCD. The gauge-invariant density-density correlators are calculated to investigate the deformation caused by the magnetic field. We find that these mesons acquire elongated shapes along the magnetic field. The magnitude of the deformation is about 10-20 % when the strength of the magnetic field is of the order of the squared unphysical pion mass.
↳ hep-lathep-phnucl-thPTEP(2019)·16 citations
11
Spin partners $W_{b J}$ from the line shapes of the $Z_{b} (10610)$ and $Z_{b} (10650)$
V. Baru🇩🇪 · E. Epelbaum🇩🇪 · A. A. Filin🇩🇪 · C. Hanhart🇩🇪 · A. V. Nefediev🇷🇺 · Q. Wang🇩🇪
In a recent paper Phys.Rev. D98, 074023 (2018), the most up-to-date experimental data for all measured production and decay channels of the bottomonium-like states $Z_{b} (10610)$ and $Z_{b} (10650)$ were analysed in a field-theoretical coupled-channel approach which respects analyticity and unitarity and incorporates both the pion exchange as well as a short-ranged potential nonperturbatively. All parameters of the interaction were fixed directly from data, and pole positions for both $Z_{b}$ states were determined. In this work we employ the same approach to predict in a parameter-free way the pole positions and the line shapes in the elastic and inelastic channels of the (still to be discovered) spin partners of the $Z_{b}$ states. They are conventionally referred to as $W_{b J}$ 's with the quantum numbers $J^{P C} = J^{++}$ ( $J = 0, 1, 2$ ). It is demonstrated that the results of our most advanced pionful fit, which gives the best $χ^{2} / d.o.f.$ for the data in the $Z_{b}$ channels, are consistent with all $W_{b J}$ states being above-threshold resonances which manifest themselves as well pronounced hump structures in the line shapes. On the contrary, in the pionless approach, all $W_{b J}$ 's are virtual states which can be seen as enhanced threshold cusps in the inelastic line shapes. Since the two above scenarios provide different imprints on the observables, the role of the one-pion exchange in the $B^{(*)} B ˉ^{(*)}$ systems can be inferred from the once available experimental data directly.
↳ hep-phnucl-thPRD(2019)·54 citations
12
On the elliptic flow of heavy quarkonia in $p A$ collisions
Cheng Zhang🇨🇳 · Cyrille Marquet🇫🇷 · Guang-You Qin🇨🇳 · Shu-Yi Wei🇫🇷 · Bo-Wen Xiao🇨🇳
Using the dilute-dense factorization in the Color Glass Condensate framework, we investigate the azimuthal angular correlation between a heavy quarkonium and a charged light hadron in proton-nucleus collisions. We extract the second harmonic $v_{2}$ , commonly known as the elliptic flow, with the light hadron as the reference. This particular azimuthal angular correlation between a heavy meson and a light hadron has first been measured at the LHC recently. The experimental results indicate that the elliptic flows for heavy-flavor mesons ( $J / ψ$ and $D^{0}$ ) are almost as large as those for light hadrons. Our calculation demonstrates that this result can be naturally interpreted as an initial state effect due to the interaction between the incoming partons from the proton and the dense gluons inside the target nucleus. Since the heavy quarkonium $v_{2}$ exhibits a weak mass dependence according to our calculation, we predict that the heavy quarkonium $Υ$ should have a similar elliptic flow as compared to that of the $J / ψ$ , which can be tested in future measurements.
↳ hep-phnucl-exnucl-thPRL(2019)·62 citations

Affiliations

first authorsco-authorsvia INSPIRE

Charmonium Excitation functions in pˉ​A Collisions

Probing nucleon's spin structures with polarized Drell-Yan in the Fermilab SpinQuest experiment

Meson deformation by magnetic fields in lattice QCD

Spin partners WbJ​ from the line shapes of the Zb​(10610) and Zb​(10650)

On the elliptic flow of heavy quarkonia in pA collisions

Affiliations

Charmonium Excitation functions in $p ˉ$ A Collisions

Spin partners $W_{b J}$ from the line shapes of the $Z_{b} (10610)$ and $Z_{b} (10650)$

On the elliptic flow of heavy quarkonia in $p A$ collisions