Measurement of exclusive $$\mathrm {\Upsilon }$$ Υ photoproduction from protons in $$\mathrm {p}$$ p Pb collisions at $$\sqrt{\smash [b]{s_{_{\mathrm {NN}}}}} = 5.02\,\text {TeV} $$ sNN=5.02TeV

Abstract

Abstract The exclusive photoproduction of $$\mathrm {\Upsilon }\mathrm {(nS)} $$ Υ(nS) meson states from protons, $$\gamma \mathrm {p} \rightarrow \mathrm {\Upsilon }\mathrm {(nS)} \,\mathrm {p}$$ γp→Υ(nS)p (with $$\mathrm {n}=1,2,3$$ n=1,2,3 ), is studied in ultraperipheral $$\mathrm {p}$$ p Pb collisions at a centre-of-mass energy per nucleon pair of $$\sqrt{\smash [b]{s_{_{\mathrm {NN}}}}} = 5.02\,\text {TeV} $$ sNN=5.02TeV . The measurement is performed using the $$\mathrm {\Upsilon }\mathrm {(nS)} \rightarrow \mu ^+\mu ^-$$ Υ(nS)→μ+μ- decay mode, with data collected by the CMS experiment corresponding to an integrated luminosity of 32.6$$\,\text {nb}^{-1}$$ nb-1 . Differential cross sections as functions of the $$\mathrm {\Upsilon }\mathrm {(nS)} $$ Υ(nS) transverse momentum squared $$p_{\mathrm {T}} ^2$$ pT2 , and rapidity y, are presented. The $$\mathrm {\Upsilon (1S)}$$ Υ(1S) photoproduction cross section is extracted in the rapidity range $$|y |< 2.2$$ |y|<2.2 , which corresponds to photon–proton centre-of-mass energies in the range $$91<W_{\gamma \mathrm {p}} <826\,\text {GeV} $$ 91<Wγp<826GeV . The data are compared to theoretical predictions based on perturbative quantum chromodynamics and to previous measurements.

Keywords

• CMS
• UPC
• photoproduction
• Y
• pPb