CMS-PAS-FSQ-16-007

CMS-PAS-FSQ-16-007
Exclusive $\rho(770)^{0}$ photoproduction in ultra-peripheral pPb collisions at ${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} =$ 5.02 TeV with the CMS experiment
CMS Collaboration
September 2018

Abstract: Exclusive $\rho(770)^{0}$ photoproduction is studied for the first time in ultra-peripheral pPb collisions at ${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} =$ 5.02 TeV. The cross section, $\sigma (\gamma \mathrm{p} \rightarrow \rho(770)^{0} \rm{p})$ , is measured for photon-proton centre-of-mass energies, $W_{\gamma \rm{p}}$ , between 29 and 213 GeV with the CMS experiment. The integrated cross section is measured to be $\sigma =$ 11.2 $\pm$ 1.4 (stat) $\pm$ 1.0 (syst) $\mu$ b. The differential cross section ${\mathrm{d}}\sigma/{\mathrm{d}}\|t\|$ is measured in the 0.025 $< \|t\| <$ 1.000 GeV $^{2}$ interval as a function of $W_{\gamma \rm{p}}$ , where $t$ is the squared four-momentum transfer at the proton vertex. The results are compared to previous measurements and theoretical predictions. The measured cross section $\sigma (\gamma \mathrm{p} \rightarrow \rho(770)^{0}\rm{p})$ has a power-law energy dependence, consistent with HERA measurements. The $W_{\gamma \rm{p}}$ dependence of the exponential slope of the ${\mathrm{d}}\sigma/{\mathrm{d}}\|t\|$ cross section for exclusive $\rho(770)^{0}$ photoproduction is also measured.
Links: CDS record (PDF) ; CADI line (restricted) ; These preliminary results are superseded in this paper, EPJC 79 (2019) 702. The superseded preliminary plots can be found here.

Figures & Tables	Summary	References	CMS Publications

Figures
png pdf	Figure 1: Template for the $\rho '$ background
png pdf	Figure 2: Template fits to the reconstructed transverse momenta of $\pi ^{+}\pi ^{-}$ distribution
png pdf	Figure 3: Invariant mass $M_{inv} (\pi ^{+}\pi ^{-})$ distribution for ${\rho \mathrm {(770)}}^{0}$ in the rapidity interval $\|y({\pi ^+} {\pi ^-})\| < 2.0$ fitted with the Soding model xxxxx
png pdf	Figure 4: Invariant mass $M_{inv} (\pi ^{+}\pi ^{-})$ distribution for ${\rho \mathrm {(770)}}^{0}$ in the rapidity interval $\|y({\pi ^+} {\pi ^-})\| < 2.0$ fitted with the Soding model xxxxx
png pdf	Figure 5: The total cross section $\sigma$ of ${\rho \mathrm {(770)}}^{0}$ photoproduction as a function of $W_{\gamma \rm {p}}$
png pdf	Figure 6: Differential cross section ${\mathrm{d}}\sigma /{\mathrm{d}}\| t \|$ for exclusive ${\rho \mathrm {(770)}}^{0}$ photoproduction in four different rapidity bins together with the STARLIGHT prediction
png pdf	Figure 6-a: Differential cross section ${\mathrm{d}}\sigma /{\mathrm{d}}\| t \|$ for exclusive ${\rho \mathrm {(770)}}^{0}$ photoproduction in four different rapidity bins together with the STARLIGHT prediction
png pdf	Figure 6-b: Differential cross section ${\mathrm{d}}\sigma /{\mathrm{d}}\| t \|$ for exclusive ${\rho \mathrm {(770)}}^{0}$ photoproduction in four different rapidity bins together with the STARLIGHT prediction
png pdf	Figure 6-c: Differential cross section ${\mathrm{d}}\sigma /{\mathrm{d}}\| t \|$ for exclusive ${\rho \mathrm {(770)}}^{0}$ photoproduction in four different rapidity bins together with the STARLIGHT prediction
png pdf	Figure 6-d: Differential cross section ${\mathrm{d}}\sigma /{\mathrm{d}}\| t \|$ for exclusive ${\rho \mathrm {(770)}}^{0}$ photoproduction in four different rapidity bins together with the STARLIGHT prediction
png pdf	Figure 7: Differential cross section $\rm {d}\sigma /\rm {d}\|t\|$ for exclusive ${\rho \mathrm {(770)}}^{0}$ photoproduction in the rapidity interval $-1.2 < y({\pi}^{+} {\pi}^{-}) < 0$ together with H1 and ZEUS data
png pdf	Figure 8: The slope parameter $b$ as a function of $W_{\gamma {\mathrm{p}}}$

Tables
png pdf	Table 1: Integrated luminosity and number of events after each of the selection requirements for the two data samples.
png pdf	Table 2: Summary of the systematic uncertainties. The total uncertainty is calculated by adding the individual uncertainties in quadrature.
png pdf	Table 3: Differential cross section for exclusive ${\rho \mathrm {(770)}}^{0}$ photoproduction, $\sigma (\gamma {\rm p} \rightarrow {\rho \mathrm {(770)}}^{0} {\rm p})$ , with statistical and systematic uncertainties, for $\|t\| < 0.5$ GeV $^{2}$ . The differential cross section d $\sigma /\rm {d}\|t\|$ is also shown, along with rapidity range and the $W_{\gamma \rm {p}}$ , $< W_{\gamma \rm {p}}>$ , and $k \frac {\mathrm {d}n}{\mathrm {d}k}$ .

Summary

In summary, the CMS Collaboration has made the first LHC measurement of the exclusive

$rho(770)^{0}$ photoproduction off protons in UPC pPb collisions at

${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} =$ 5.02 TeV. The cross section of this process is measured in the photon-proton centre-of-mass energy interval 29

$< W_{\gamma \rm{p}} <$ 213 GeV. The total cross section reproduces well the measurements performed by the H1 and ZEUS Collaborations at HERA. The combination of the present data and the earlier, lower energy results is in good agreement with theoretically inspired fits. The differential cross section d

$\sigma/\rm{d}|t|$ for

$rho(770)^{0}$ photoproduction is measured as a function of

$W_{\gamma \rm{p}}$ and compared to STARLIGHT predictions.

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