English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

The ALICE Collaboration at the LHC has measured the J/$\psi$ and $\psi^{'}$photoproduction at mid-rapidity in ultra-peripheral Pb-Pb collisions at$\sqrt{s_{\rm NN}}=2.76$ TeV. The charmonium is identified via its leptonicdecay for events where the hadronic activity is required to be minimal. Theanalysis is based on an event sample corresponding to an integrated luminosityof about 23 $\mu\rm{b}^{-1}$. The cross section for coherent and incoherentJ/$\psi$ production in the rapidity interval $-0.9<y<0.9$, are$\mathrm{d}\sigma_{{\rm J}/\psi}^{\rm coh}/\mathrm{d}y =2.38^{+0.34}_{-0.24}\big(\mathrm{sta+sys}\big)$mb. and $\mathrm{d}\sigma_{{\rmJ}/\psi}^{\rm inc}/\mathrm{d}y =0.98^{+0.19}_{-0.17}\big(\mathrm{sta+sys}\big)$mb, respectively. The resultsare compared to theoretical models for J/$\psi$ production and the coherentcross section is found to be in good agreement with those models incorporatingmoderate nuclear gluon shadowing, such as EPS09 parametrization. In additionthe cross section for the process $\gamma\gamma\rightarrow e^+ e^-$ has beenmeasured and found to be in agreement with models implementing QED at leadingorder.

Charmonium and $e^+e^-$ pair photoproduction at mid-rapidity in ultra-peripheral Pb-Pb collisions at $\sqrt{s_{\rm NN}}$=2.76 TeV