From identical S- and P-wave $$p_\mathrm{T}$$ pT spectra to maximally distinct polarizations: probing NRQCD with $$\chi $$ χ states
Abstract A global analysis of ATLAS and CMS measurements reveals that, at mid-rapidity, the directly-produced $$\chi _{c1}$$ χc1 , $$\chi _{c2}$$ χc2 and J/$$\psi $$ ψ mesons have differential cross sections of seemingly identical shapes, when presented as a function of the mass-rescaled transverse...
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doaj-0abf522e9f42445f892c504938c1cde02020-11-24T21:04:32ZengSpringerOpenEuropean Physical Journal C: Particles and Fields1434-60441434-60522018-03-017831810.1140/epjc/s10052-018-5755-7From identical S- and P-wave $$p_\mathrm{T}$$ pT spectra to maximally distinct polarizations: probing NRQCD with $$\chi $$ χ statesPietro Faccioli0Carlos Lourenço1Mariana Araújo2João Seixas3Ilse Krätschmer4Valentin Knünz5LIP and ISTCERNCERNLIP and ISTHEPHYCERNAbstract A global analysis of ATLAS and CMS measurements reveals that, at mid-rapidity, the directly-produced $$\chi _{c1}$$ χc1 , $$\chi _{c2}$$ χc2 and J/$$\psi $$ ψ mesons have differential cross sections of seemingly identical shapes, when presented as a function of the mass-rescaled transverse momentum, $$p_\mathrm{T}/M$$ pT/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 $$p_\mathrm{T}$$ pT -differential cross sections. Remarkably, accurate kinematic cancellations among the various 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 $$\chi _{c1}$$ χc1 and $$\chi _{c2}$$ χc2 polarizations, the only observables not yet measured: they should be almost maximally different from one another, and from the J/$$\psi $$ ψ polarization, a striking exception in the global panorama of quarkonium production. Measurements of the difference between the $$\chi _{c1}$$ χc1 , $$\chi _{c2}$$ χc2 and J/$$\psi $$ ψ polarizations, complementing the observed identity of momentum dependences, represent a decisive probe of NRQCD.http://link.springer.com/article/10.1140/epjc/s10052-018-5755-7 |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Pietro Faccioli Carlos Lourenço Mariana Araújo João Seixas Ilse Krätschmer Valentin Knünz |
spellingShingle |
Pietro Faccioli Carlos Lourenço Mariana Araújo João Seixas Ilse Krätschmer Valentin Knünz From identical S- and P-wave $$p_\mathrm{T}$$ pT spectra to maximally distinct polarizations: probing NRQCD with $$\chi $$ χ states European Physical Journal C: Particles and Fields |
author_facet |
Pietro Faccioli Carlos Lourenço Mariana Araújo João Seixas Ilse Krätschmer Valentin Knünz |
author_sort |
Pietro Faccioli |
title |
From identical S- and P-wave $$p_\mathrm{T}$$ pT spectra to maximally distinct polarizations: probing NRQCD with $$\chi $$ χ states |
title_short |
From identical S- and P-wave $$p_\mathrm{T}$$ pT spectra to maximally distinct polarizations: probing NRQCD with $$\chi $$ χ states |
title_full |
From identical S- and P-wave $$p_\mathrm{T}$$ pT spectra to maximally distinct polarizations: probing NRQCD with $$\chi $$ χ states |
title_fullStr |
From identical S- and P-wave $$p_\mathrm{T}$$ pT spectra to maximally distinct polarizations: probing NRQCD with $$\chi $$ χ states |
title_full_unstemmed |
From identical S- and P-wave $$p_\mathrm{T}$$ pT spectra to maximally distinct polarizations: probing NRQCD with $$\chi $$ χ states |
title_sort |
from identical s- and p-wave $$p_\mathrm{t}$$ pt spectra to maximally distinct polarizations: probing nrqcd with $$\chi $$ χ states |
publisher |
SpringerOpen |
series |
European Physical Journal C: Particles and Fields |
issn |
1434-6044 1434-6052 |
publishDate |
2018-03-01 |
description |
Abstract A global analysis of ATLAS and CMS measurements reveals that, at mid-rapidity, the directly-produced $$\chi _{c1}$$ χc1 , $$\chi _{c2}$$ χc2 and J/$$\psi $$ ψ mesons have differential cross sections of seemingly identical shapes, when presented as a function of the mass-rescaled transverse momentum, $$p_\mathrm{T}/M$$ pT/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 $$p_\mathrm{T}$$ pT -differential cross sections. Remarkably, accurate kinematic cancellations among the various 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 $$\chi _{c1}$$ χc1 and $$\chi _{c2}$$ χc2 polarizations, the only observables not yet measured: they should be almost maximally different from one another, and from the J/$$\psi $$ ψ polarization, a striking exception in the global panorama of quarkonium production. Measurements of the difference between the $$\chi _{c1}$$ χc1 , $$\chi _{c2}$$ χc2 and J/$$\psi $$ ψ polarizations, complementing the observed identity of momentum dependences, represent a decisive probe of NRQCD. |
url |
http://link.springer.com/article/10.1140/epjc/s10052-018-5755-7 |
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