Abstract
The LHCb experiment, besides its main programme concerning flavour physics performs also very well as a general purpose forward detector, covering the pseudo-rapidity range from 2.0 to 5.0. Exploiting the experiment’s unique geometry, the LHCb collaboration is pursuing a rich programme of forward QCD measurements. In particular two-particle angular correlations are studied in proton-lead collisions at a nucleon-nucleon centre-of-mass energy of √ S NN = 5 TeV, with data collected by the LHCb detector at the LHC in 2013. The analysis is based on data recorded in two opposing beam configurations, in which either the direction of the proton or that of the lead remnants is analysed. This is the first measurement of a long-range correlation on the near side in proton-lead collisions in the forward region. It extends previous observations in the central region.
Highlights
Of a high-density system likely produced in these collisions
The two beam configurations provided by LHC, p+Pb and Pb+ p which differs by the direction of proton and ion beams can be analysed in the forward region
The correlation for particles with 1 < pT < 2 GeV/c is illustrated in Fig. 2 for p+Pb configuration and in Fig. 3 for Pb+ p configuration
Summary
The instrumentation of the LHCb singlearm spectrometer covers a unique rapidity range 2 < η < 5 in the laboratory frame [22, 23]. The measurements are based on proton-lead collisions that are dominated by single interactions (98%). The simple trigger was configured to accept events with at least one reconstructed track in the vertex detector for non-empty beam bunch crossing. The events were required to have exactly one reconstructed primary vertex with at least five tracks. The tracks were selected to originate directly from interaction point based on its impact parameter with respect to primary vertex. The rapidity range in the nucleon-nucleon centre-of-mass frame is 1.5 < y < 4.4 for p+Pb and −5.4 < y < −2.5 for Pb+ p. The results of the analysis were published in Ref. [24]
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