Publication
From identical S- and P-wave $p_\mathrm{T}$ spectra to maximally distinct polarizations: probing NRQCD with $\chi $ states
| dc.contributor.author | Faccioli, Pietro | |
| dc.contributor.author | Lourenço, Carlos | |
| dc.contributor.author | Araújo, Mariana | |
| dc.contributor.author | Seixas, João | |
| dc.contributor.author | Krätschmer, Ilse | |
| dc.contributor.author | Knünz, Valentin | |
| dc.date.accessioned | 2019-02-05T15:53:53Z | |
| dc.date.available | 2019-02-05T15:53:53Z | |
| dc.date.issued | 2018-03-29 | |
| dc.date.updated | 2019-02-05T15:53:53Z | |
| dc.description.abstract | A global analysis of ATLAS and CMS measurements reveals that, at mid-rapidity, the directly-produced $\chi_{c1}$, $\chi_{c2}$ and J/$\psi$ mesons have differential cross sections of seemingly identical shapes, when presented as a function of the mass-rescaled transverse momentum, $p_{\rm T}/M$. This identity of kinematic behaviours among S- and P-wave quarkonia is certainly not a natural expectation of non-relativistic QCD (NRQCD), where each quarkonium state is supposed to reflect a specific family of elementary production processes, of significantly different $p_{\rm T}$-differential cross sections. Remarkably, accurate kinematic cancellations among the variegated NRQCD terms (colour singlets and octets) of its factorization expansion can lead to a surprisingly good description of the data. This peculiar tuning of the NRQCD mixtures leads to a clear prediction regarding the $\chi_{c1}$ and $\chi_{c2}$ polarizations, the only observables not yet measured: they should be almost maximally different from one another, and from the J/$\psi$ polarization, a striking exception in the global panorama of quarkonium production. Measurements of the difference between the $\chi_{c1}$, $\chi_{c2}$ and J/$\psi$ polarizations, complementing the observed identity of momentum dependences, represent a decisive probe of NRQCD. | |
| dc.description.version | Peer Reviewed | |
| dc.identifier | Eur.Phys.J. C78 (2018) 268; DOI 10.1140/epjc/s10052-018-5755-7 | |
| dc.identifier.uri | http://dx.doi.org/10.1140/epjc/s10052-018-5755-7 | |
| dc.identifier.uri | http://hdl.handle.net/10400.26/27570 | |
| dc.language.iso | eng | |
| dc.title | From identical S- and P-wave $p_\mathrm{T}$ spectra to maximally distinct polarizations: probing NRQCD with $\chi $ states | |
| dc.type | journal article | |
| dspace.entity.type | Publication | |
| rcaap.rights | openAccess | pt |
| rcaap.type | article |